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Inorganic-Organic Hybrid Tongue-Mimic for Time-Resolved Luminescent Noninvasive Pattern and Chiral Recognition of Thiols in Biofluids toward Healthcare Monitoring
Abstract
In this work, manganese(II)-doped zinc/germanium oxide nanoparticles (Mn@ZGNPs) have been hydrothermally synthesized to equip with appealing time-resolved luminescence (TRL). Interestingly, we reveal that they can be readily quenched (“turn off”) via a facile surface coating with bioinspired polydopamine (PDA) polymerized from dopamine (DA), resulting from PDA-triggered TRL resonance energy transfer (TRL-RET). By Integrated with the thiol-induced inhibition of PDA formation, an ingenious inorganic-organic hybrid tongue-mimic sensor array is thus unveiled for noninvasive pattern recognition of thiols in biofluids in a TRL-RET-reversed "turn on" format toward healthcare monitoring. The sensing principle is based on the new finding that there are differential inhibitions from thiols against the polymerization of DA with various concentrations. Furthermore, density function theory (DFT) studies excellently prove our sensing principle and experimental results, reinforcing the power of the presented system. More importantly, chiral recognition of varied concentrations and mixtures of cysteine enantiomers using our platform are also been demonstrated, promising its practical usage. This is a novel concept of inorganic-organic hybrid-based pattern and chiral recognition platform for TRL background-free sensing and would sprout more novel relevant strategies toward broader applications.
... To some degree, antioxidants can effi-ciently eliminate and inactivate the free reactive oxygen species (ROS) including hydroxyl radical (•OH), superoxide free radicals (ROO•) and so on [5]. Among common antioxidants, ascorbic acid (AA), namely vitamin C, is differed from other reductant biothiols in molecular structure [6], so many functions related to AA have been explored in physiological mechanism [7]. Previous work has proved that AA has great potential in anti-cancer activity through DNA demethylation mediated by ten-eleven translocation enzyme activation [8]. ...
... We herein report a novel strategy for rapid determination of AA in a mix-and-read format. Mn 2+ -doped zinc/germanium oxide nanoparticles (Mn@ZnGe NPs) were synthesized with the characteristic green emission of Mn 2+ (fluorescence peak at 536 nm) and appealing time-resolved phosphorescence (TRP) [6]. Due to the extensive overlap between the excitation spectrum of Mn@ZnGe NPs and the absorption spectrum of AA in UV region, an effective inner-filter effect (IFE) process can take place and then the TRP of Mn@ZnGe NPs gradually decrease with the addition of various amount of AA, which can provide a detection method for AA in a TRP Bturn offf ormat. ...
... Synthetic procedure of Mn@ZnGe NPs was referred to our previous work with minor modifications [6]. In brief, 11 mL of deionized water with 0.98 mL of 2 M of Zn(NO 3 ) 2 and 62.5 μL of 0.08 M of Mn(NO 3 ) 2 were mixed well under room temperature. ...
A method is described for the determination of ascorbic acid (AA) in complex biological fluids. It based on maganese(II)-doped zinc/germanium oxide nanoparticles (Mn@ZnGe NPs) with appealing time-resolved phosphorescence (TRP). TRP can provide a background-free reporter signal in analytical methods. The absorption of AA overlaps the excitation band of Mn@ZnGe NPs at 254 nm. This reduces the intensity of fluorescence via an inner filter effect (IFE) with increasing concentration of AA. Typical experimental conditions include an emission peak at 536 nm, a delay time of 50 μs and a counting time of 2 ms. This method can detect AA in a range of 5–500 μM with a 0.13 μM limit of detection. If AA is oxidized by the enzyme AA oxidase (AAOx), dehydroascorbic acid will be formed which doesn’t absorb at 254 nm. Hence, the IFE cannot occur and fluorescence is not reduced. The strategy can be used to quantify AAOx in the activity range of 1–4 U·mL⁻¹. By using a handheld UV lamp and a smart phone with a color-scanning feature, the feasibility for visual detection and real-time/onsite quantitative scanometric monitoring of AA and AAOx is demonstrated.
Graphical abstractSchematic presentation of a fluorometric method for determination of ascorbic acid (AA) and ascorbic oxidase and a scanometric visual assay. It based on the use of maganese(II)-doped zinc/germanium oxide nanoparticles (Mn@ZnGe NPs) with appealing time-resolved phosphorescence (TRP) and the inner-filter effect (IFE) between AA and Mn@ZnGe NPs.
... Considering the chemical complexity of biological samples, in 2018, Zhang's group reported identifying and quantifying biological thiols by a sensor array [37]. ...
... Illustration of the discrimination of thiols in biofluids by the "turn on" assay based on Mn(II)-doped zinc/germanium oxide nanoparticles and DA developed by Zhang and coworkers. Adapted from Ref.[37] with permission from the American Chemical Society, copyright 2018. ...
The detection and discrimination of chiral analytes has always been a topical theme in food and pharmaceutical industries and environmental monitoring, especially when dealing with chiral drugs and pesticides, whose enantiomeric nature assessment is of crucial importance. The typical approach matches novel chiral receptors designed ad hoc for the discrimination of a target enantiomer with emerging nanotechnologies. The massive synthetic efforts requested and the difficulty of analyzing complex matrices warrant the ever-growing exploitation of sensor array as an alternative route, using a limited number of chiral or both chiral and achiral sensors for the stereoselective identification and dosing of chiral compounds. This review aims to illustrate a little-explored winning strategy in chiral sensing based on sensor arrays. This strategy mimics the functioning of natural olfactory systems that perceive some couples of enantiomeric compounds as distinctive odors (i.e., using an array of a considerable number of broad selective receptors). Thus, fundamental concepts related to the working principle of sensor arrays and the role of data analysis techniques and models have been briefly presented. After the discussion of existing examples in the literature using arrays for discriminating enantiomers and, in some cases, determining the enantiomeric excess, the remaining challenges and future directions are outlined for researchers interested in chiral sensing applications.
... Oxidation-reduction reaction was also under our consideration. Polydopamine (PDA) derived from dopamine monomer was an ideal quencher for many inorganic fluorescent species (such as manganese(II)-doped zinc/ germanium oxide nanoparticles) and from blocking of polymerization by redox mechanism, a novel inorganic-organic hybrid sensor array in a fluorescence "turn-on" format has been established toward the pattern recognition of many biothiols [86]. ...
... This method is also limited by the affinity constant of metal ions. Another intriguing way was developed by our group [86]. The formation of PDA processed the steps of oxidation, cyclization, rearrangement and polymerization. ...
Conventional molecular recognition was tightly related to the development of analyte-specific sensor. However, all most every biochemical process are not decided on only one factor. When several factors were imported simultaneously, the established sensor could be seriously interfered and gave the wrong response. In this regard, chemical tongue-mimic sensor array was promoted to recognize a set of analytes, which concerned each component of mixtures. This review, focused on the development of chemical “tongue” sensor arrays from recent years, and gave enlightening examples about how to design integrated sensor system, how to choose the responsive signals and explain the mechanism of each used. As for applications, this review concluded the status of what chemical or biochemical species could be discriminated, what the advantages or drawbacks they had and the novel mechanism they used. In the last, this review also pointed out the limitations and future of related field.
... The same research group also developed a flexible device for monitoring the pH in sweat by depositing an iridium oxide film onto graphite working electrode and combinig it with an integrated circuit board allows for data acquisition [145]. As well as electrochemical detection, also optical detection has been proposed for its application on wearable biosensors [146][147][148][149][150][151] (Figure 4b). In this case some biomarkers have intrinsic optical properties like absorption and emission spectra that allows to selectively detect these species [152]. ...
Analytical chemistry applied to medical and diagnostic analysis, recently focused on the development of cost-effective biosensors able to monitor the health status or to assess the level of specific biomarkers that can be indicative for several diseases. The improvement of technologies relating to the possibility of non-invasive sampling of biological fluids, as well as sensors for the detection of analytical signals and the computational capabilities of the systems routinely employed in everyday life (e.g. smartphones, computers, etc.), make the complete integration of self-standing analytical devices more accessible. This review aims to discuss the biosensors that have been proposed in the last 5 years focusing on two principal detecting approaches, optical and electrochemical, which have been employed for quantifying different kind of target analytes reaching detection limits below the clinical sample levels required. These detection principles applied to Point-of-care (POC) devices, have been extensively reported in literature and even the limited examples found on the market are based on these strategies. This work will show the latest innovations considering the integration of optical and electrochemical detection with the most commonly reported analytical platforms for POC applications such as paper-based or wearable and implantable devices.
... Over the past few years, nanoparticles (NPs) have been widely applied to assess the enantiomeric purity of chiral targets within several chiral recognition strategies. 37 The chiroptical properties of NPs can be easily tuned and boosted by optimizing their core structure or by manipulating chiral ligands on their surface with the aim of designing promising sensing platforms for chiral discrimination. 38−41 In addition, chiral self-assemblies of NPs that are provided based on specific interactions between their surface ligands have exhibited interesting chiroptical properties. ...
... Various methods have been used for the chiral recognition of enantiomers, in particular, optical methods, such as colorimetry [4][5][6][7], spectrofluorimetry [8][9][10][11] and circular dichroism (CD) spectroscopy [12][13][14][15][16][17][18] have received great interest due to their apparent advantages over other methods by virtue of their high sensitivity and the convenience in operation. CD spectroscopy is generally utilized to analyze the molecular chirality, which is sensitive to the conformational changes of the chiral molecules. ...
Chiral recognition is of fundamental importance in chemistry and life sciences and the principle of chiral recognition is instructive in chiral separation and enantioselective catalysis. Non-chiral Ag nanoparticles (NPs) conjugated with chiral cysteine (Cys) molecules demonstrate strong circular dichroism (CD) responses in the UV range. The optical activities of the l-/d-Cys capped Ag NPs are associated with the formation of order arrangements of chiral molecules on the surface of Ag NPs, which are promoted by the electrostatic attraction and hydrogen bonding interaction. The intensity of the chiroptical response is related to the total surface area of Ag NPs in the colloidal solution. The anisotropy factor on the order of 10−2 is acquired for Ag NPs with the size varying from ~2.4 to ~4.5 nm. We demonstrate a simple and effective method for the fabrication of a quantitative chiral sensing platform, in which mesoporous silica coated Ag nanoparticles (Ag@mSiO2) were used as chiral probes for recognition and quantification of Cys enantiomers.
Analytical chemistry applied to medical and diagnostic analysis has recently focused on the development of cost-effective biosensors able to monitor the health status or to assess the level of specific biomarkers that can be indicative of several diseases. The improvement of technologies relating to the possibility of the non-invasive sampling of biological fluids, as well as sensors for the detection of analytical signals and the computational capabilities of the systems routinely employed in everyday life (e.g., smartphones, computers, etc.), makes the complete integration of self-standing analytical devices more accessible. This review aims to discuss the biosensors that have been proposed in the last five years focusing on two principal detecting approaches, optical and electrochemical, which have been employed for quantifying different kinds of target analytes reaching detection limits below the clinical sample levels required. These detection principles applied to point-of-care (POC) devices have been extensively reported in literature, and even the limited examples found on the market are based on these strategies. This work will show the latest innovations considering the integration of optical and electrochemical detection with the most commonly reported analytical platforms for POC applications such as paper-based or wearable and implantable devices.
For accurately discriminating and detecting metal ions that pose a threat to both public health and the natural environment, higher requirements are put forward for sensor designing. The emergence of sensor arrays diminishes the difficulty of designing specific receptors to a certain extent, but actualizing high-order sensing from one material with different transduction principles remains a challenge. Herein, a dual-channel sensing platform is firstly proposed for high-throughput recognizing eight metal ions based on simultaneously collecting different optical signals from sulfur quantum dots (S dots). The robust statistical techniques (linear discriminant analysis and hierarchical cluster analysis) convert noticeable signal changes (fluorescence, second-order scattering, and ultraviolet-visible absorption) of S dots, resulting from the affinity of sulfur atoms to metal ions, into unique “fingerprints” and “Euclidean distances”, respectively. Hence, eight metal ions and their mixtures are well identified, circumventing the drawbacks of multi-materials sensing array in increasing the cost and complexity of experiments. Significantly, the high-order sensing platform allows the qualitative performance of metal ions and the semi-quantitative analysis of mixed metal ions in actual water samples. Therefore, the high-order sensor array for metal ions discrimination provides a high-throughput, cost-effective, rather powerful and competitive solution to analogues recognition and environmental tests, which constitutes an essential motivation for this work.
Traditional single sensor is designed based on the “lock-and-key” mode, which only relies on the most dominant interactions between the sensing element and the target. Although it exhibits high selectivity, there are challenges in detecting multiple analytes at the same time. Here, a sensor array with three sensing elements is developed to detect multiple heavy metal ions simultaneously and quickly. In our experiment, bovine serum albumin-encapsulated gold nanoclusters (BSA-AuNCs) were used as fluorescence probes and three different dopamine (DA) concentrations as nonspecific receptors. As we know, self-polymerized polydopamine (PDA) can quench part of the fluorescence of BSA-AuNCs. Upon the addition of the heavy metal ions, the diverse non-specific interactions between DA and heavy metal ions result in the difference in the number of the remaining PDA. Therefore it would lead to different degrees of fluorescence recovery behavior. This unique “turn-on” fluorescence response mode can be analyzed by linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA). Two-dimensional, three-dimensional and even four-dimensional mixed ions detection and quantitative detection have also been achieved. Moreover, by using this fluorescence array mode, heavy metal ions in tap water or blood samples can be detected.
Wearable biochemical sensors have received substantial attention in recent years due to their great potential to provide insights into the physical condition of individuals. Based on the innovative biochemical sensing mechanisms and the recent advances in material science, the integrated biosensors are moving toward soft and small on-body electronic systems that can smartly and persistently monitor tiny changes in biochemical markers. They are beginning to transform almost every aspect of healthcare. This review looks into the state-of-the-art advances in this rising field by connecting the noninvasive biochemical sensing principles, materials science, advanced integration methods and the most representative cases of health monitoring wearable biosensors. Specifically, starting with a brief overview of the trends in wearable healthcare devices, we introduce the fundamental of chemistry for bio-sensing. The subsequent content highlights the contributions of nanomaterials and nanotechnologies in integrating and achieving on-body bio-sensing systems. We also discuss the key issues emerging in this area from a biocompatibility and material perspective. In the end, the review concludes with a summary of opportunities where advances in biochemistry and nanotechnology will be significant for future progress.
Chiral recognition is of significant importance in the fields of chemical asymmetric synthesis and biological pharmaceutical research. In this work, an electrochemical chiral sensor with two kinds of chiral sites (chiral cavity for β-cyclodextrin and chiral skeleton for Ca-sacc/MeOH) by electrooxidation β-cyclodextrin onto Ca-sacc/MeOH was built. The proposed multichiral β[email protected]/MeOH/GCE can be used for recognition of tryptophan and penicillamine enantiomers simultaneously with wide linear range, low detection limits value, high repeatability and stability within the available electrochemical window. The strategy for integration multichiral sources is crucial to construct novel chiral platforms for simultaneous recognition of multiple chiral compounds in complicated chiral systems.
Numerous detection strategies have been undertaken for quantitative analysis of single metal ion in the field of water-quality monitoring, whereas the complexity in the types and concentrations of potential contaminant leads us to should focus on groups of contaminants than to individual contaminants. To the best of our knowledge, there are few strategies to explore cross response-based semiselective sensor array in the area of water-quality monitoring. In this study, a colorimetric sensor array based on enzyme response analysis was innovatively developed for pattern recognition of various metal ions. Three types of metal phosphates-acetylcholinesterase nanoflowers (MP-AChE NFs) were prepared by using a green, facile, cost-efficient enzyme immobilization technology to construct the sensor array. With the help of a multivariate statistical analysis that can concentrate the most significant characteristics (variance) of the data into a lower dimensional space, principal component analysis (PCA) successfully identifies and distinguishes 11 species of metal ions, and gives unique fingerprint information for each analyte. Moreover, the sensor array can distinguish different concentrations of single model analyte, as well as a mixture of different contaminants in tap water.
Biological thiols are essential for mediating physiological and pathological processes. Because of their similarity of structures and reactivity properties, it is a challenging but significant task to identify different types of biological thiols. Herein, a multichannel sensor array was constructed to identify biological thiols based on three-color emitting carbon dots (CDs)-metal ion pairs. Primarily, three metal ions (Cu²⁺, Ag⁺, and Fe³⁺) were selected to quench the fluorescence signals of the three CDs, respectively. Upon the addition of thiols, the fluorescence intensities of the three CDs can be restored or further quenched owing to the synergistic coordinative and steric hindrance effect of the interaction and between thiols, metal ions and the three CDs. Recur to statistical analysis methods, the multichannel sensor array can effectively discriminate six thiols in serum and urine media using only a single “well”. Moreover, the present multichannel sensor array can also be effectively identified cell type from normal or cancer cells. Collectively, the versatile sensor array based on CDs-metal ion pairs offers a highly discerning and adaptive alternative for identifying biological thiols, which exhibit great potential in point-of-care clinical diagnostics.
Lanthanide-doped upconversion nanoparticles (Ln-UCNPs) are a new type of nanomaterials with excellent fluorescence properties, which are well applied in fluorescent biosensing. Herein we developed a multifunctional probe based on the surface engineering of core-shell structure UCNPs with polyacrylic acid (PAA). The developed PAA/UCNPs probe could be highly selective to detect and respond to Cu²⁺ at different pH. Cu²⁺ could easily combine with the carboxylate anion of PAA to quench the fluorescence of UCNPs. Therefore, we creatively proposed a fluorescent array sensor (PAA/UCNPs-Cu²⁺), in which the same material acted as the sensing element by coupled with pH regulation for pattern recognition of 5 thiols. It could also easily identify the chiral enantiomer of cystine (L-Cys and D-Cys), and distinguish their mixed samples with different concentrations, and more importantly, it could be combined with urine samples to detect actual level of homocysteine (Hcys) to provide a new solution for judging whether the human body suffers from homocystinuria.
Tunable multi-responsive mesoporous silica nanoparticles were prepared by post-condensation/surface modification of MCM-41 nanoparticles. Surface grafting of a poly(N,N-dimethylaminoethyl methacrylate)-based polymer containing disulfide bonds was achieved by a click reaction. Chemical modification, morphological characteristics, and textural properties of the nanoparticles were studied using multiple characterization techniques such as Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, small-angle X-ray scattering, and nitrogen adsorption/desorption behavior. The nanoparticles retained the meso-structural integrity of MCM41 and particle size < 100 nm after grafting with the polymer. The pH and redox-responsive behavior of the nanoparticles were also studied. The nanoparticles possess excellent drug-loading capacity owing to their large surface area and 'closed gate' mechanism of the grafted polymer chains. The release profile of doxorubicin at two different pH (7.4 and 5.5) and in the presence of dithiothreitol showed a dual response behavior. The nano drug carrier device exhibited efficient intracellular uptake in cancer cells with suitable cytotoxicity and pharmacokinetic behavior, and may therefore be considered a good candidate for cancer therapy.
Over the past decade, non-invasive wearable chemical sensors have gained tremendous attention in the field of personal health monitoring and medical diagnosis. These sensors provide non-invasive, real-time, and continuous monitoring of targeted biomarkers with more simplicity than the conventional diagnostic approaches. This review primarily describes the substrate materials used for sensor fabrication, sample collection and handling, and analytical detection techniques that are utilized to detect biomarkers in different biofluids. Common substrates including paper, textile, and hydrogel for wearable sensor fabrication are discussed. Principles and applications of colorimetric and electrochemical detection in wearable chemical sensors are illustrated. Data transmission systems enabling wireless communication between the sensor and output devices are also discussed. Finally, examples of different designs of wearable chemical sensors including tattoos, garments, and accessories are shown. Successful development of non-invasive wearable chemical sensors will effectively help users to manage their personal health, predict the potential diseases, and eventually improve the overall quality of life.
In this work, we prepared a type of multiplexing upconversion nanoparticle (UCNP). There are three fluorescence emission peaks when our UCNPs are excited with 980 and 808 nm lasers. These fluorescence peaks of UCNPs can be quenched ("turn off") to varying degrees via fluorescence resonance energy transfer (FRET) when the UCNPs are coated with a polydopamine (PDA) layer, which is a universal quencher self-polymerized from dopamine (DA). Here, we create a novel single-component nanoprobe that can be used for the pattern recognition of antioxidants in a "turn on" manner by integrating with the prevention of PDA formation with an antioxidant. Our sensing strategy is based on the recovery of the fluorescence intensity of three emission peaks to different degrees due to different antioxidants with differential inhibition of PDA formation. Then, these three fluorescence emission peaks of UCNPs are innovatively selected as the sensor array, which enables us to discriminate multiple antioxidants and their mixtures. Simultaneously, the sensor array shows excellent performance in the chiral discrimination of cysteine enantiomers. This is a novel, innovative sensor array that requires only a single component to achieve the upconversion fluorescence pattern and recognize chiral molecules, and it elucidates a more innovative concept towards widespread applications.
To date, the effective discrimination of anionic sulfonate surfactants with tiny differences in structure, considered as environmentally noxious xenobiotics, is still a challenge for traditional analytical techniques. Fortunately, sensor array becomes the best choice for recognizing targets with similar structures or physical/chemical properties by virtue of principal component analysis (PCA, a statistical technique). Herein, benefiting from the construction of the statistical strategy and using two types of luminescent metal-organic frameworks (LMOFs, NH2-UiO-66 and NH2-MIL-88) as sensing elements, high-throughput discrimination and detection of five anionic sulfonate surfactants as well as their mixtures are nicely realized for the first time. Significantly, the stacking interaction of aromatic rings and dynamic quenching play essential roles in the generation of diverse fluorescence responses and unique fingerprint maps for individual anionic sulfonate surfactants. Moreover, the mixtures of anionic sulfonate surfactants are also satisfactorily distinguished in environmental water samples, demonstrating the practicability of the sensor array. On the basis of the PCA method, this strategy converts general fluorescence signals into unique optical fingerprints of individual analytes, providing a new opportunity for the application of LMOFs in the field of analytes recognition.
Thiols play vital roles in mediating physiological processes. However, it is difficult to discriminate one thiol species from other due to the similarities among structures and reactivities of thiols. In light of the ultra-low background and impressive discrimination power, persistent luminescence-based sensing array has attracted increasing attention while remains a huge challenge. Herein, we have throughly studied the chemistry involved dual-emission PLNPs (D-PLNPs) with metal ions (MI) and for the first time proposed MI-triggered ratiometric persistent luminescence (R-PersL) sensor array for the discrimination of six thiols. To extract data-rich outputs from a single sensor element, three representative D-PLNPs with core-shell structure and subsequent carboxyl functionalizations (CSD-PLNPs) were rationally fabricated. Interestingly, MI revealed the different regulating efficiencies for two main emission bands of CSD-PLNPs, resulting from MI-triggered R-PersL signal transductions. Inspired by the crucial roles of thiols in vivo, a proof-of-concept sensor array through the ensemble of CSD-PLNPs-COOH and certain MI was developed and demonstrated R-PersL “fingerprint“ pattern identification for six thiols. Remarkably, in virtue of autofluorescence-free background and high-throughput signal output, this sensing array system enabled a highly sensitive and differentiable detection of thiols at various concentrations in human blood serums, paving a new way to develop multi-parameters sensing for complex analytes.
Enormous efforts have been paid to detection of various biothiols due to their involvements in many physiological processes. In the present work, we reported a simple fluorescent sensor array for fingerprinting four different biothiols based on the same probe. The probe was a dual-fluorophore containing pyrene-pyronine FRET pair and its fluorescence emission could be easily modulated by CTAB surfactant assemblies. The three-element sensor array was built by simply varying CTAB concentration in the sensor elements that contained the same probe. The array can produce unique fluorescence fingerprints for four different biothiols and be applied to discriminate them even in biofluids like serum and urine. This study demonstrates the surfactant modulation strategy associated with using a FRET dual-fluorophore can offer an opportunity to build simple and effective fingerprinting sensing platform for multiple biothiols.
A colorimetric sensor array was constructed to detect metal ions by pattern recognition based on image analysis and absorption spectra.
The three most important redox couples, including cysteine (Cys)/cystine (Cyss), homocysteine (Hcys)/homocystine (Hcyss) and reduced glutathione (GSH)/glutathione disulfide (GSSG), are closely associated with human aging and many diseases. Thus, it is highly important to determine their redox statuses at the following two levels: ⅰ) the redox identity in different thiols/disulfides and ⅱ) the redox ratio in a mixture of a specific couple. Herein, by using one single AIE-doped photonic-structured poly(ionic liquid) sphere as a virtual sensor array (AIE, aggregation-induced emission), we firstly realize the direct determination of the redox status without a reducing pre-treatment of disulfides, which will greatly promote the development of high-throughput and simple procedures. The pattern-recognition method uses the multiple noncovalent interactions of imidazolium-based poly(ionic liquid)s (PILs) with these redox species to produce differential responses in both the photonic crystal and fluorescence dual channels. On the one hand, a single sphere enables the direct and simultaneous discrimination of the redox identities of Cys, Cyss, Hcys, Hcyss, GSH and GSSG under the interference of other five commonly occurring thiols. On the other hand, this sphere also allows for not only the direct quantification of the GSH/GSSG ratios without previously determining the individual concentrations of GSH and GSSG, but also the accurate prediction of the ratios in unknown redox samples. To further demonstrate the real-life applications, redox mixtures in a real biological context are differentiated. Additionally, quantum calculations further confirm the interactions between the imidazolium-based PILs and these redox species.
A facile approach was reported to synthesize β-cyclodextrin functionalized graphene that is bridged by 3,4,9,10-perylene tetracarboxylic acid (rGO-PTCA-CD) via a chemical route that involves the functionalization of rGO with PTCA followed by covalently cross-linking NH2-β-CD. The as-prepared rGO-PTCA-CD was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. The working electrodes were thoroughly studied for the cyclic voltammetry by using [Fe(CN)6]4−/3- as redox probe and using ferrocene as an internal standard. Furthermore, rGO-PTCA-CD was successfully applied to the recognition of phenylalanine enantiomers. The host-guest inclusion interaction between rGO-PTCA-CD and the phenylalanine enantiomers was investigated by differential pulse voltammetry with Fc used as a competitor. The recognition result showed that the rGO-PTCA-CD-modified glassy carbon electrode exhibited higher chiral recognition capability for L-Phe than for D-Phe with an enantioselectivity coefficient of 2.07. The proposed modified electrode had a limit of detection of 0.08 nM and 0.2 nM (S/N = 3) for L-Phe and D-Phe, respectively, with a linear response range of 0.01 mM to 5 mM, which was ascribed to the synergy of the rGO-PTCA (e.g., its excellent electrochemical performance) and β-CD (e.g., the hydrophobic inner cavity with good molecular recognition and enrichment abilities).
The discrimination of various sulfur containing species helps us to deeply understand how sulfur affects cellular signaling and other physiological events. Herein, we present a three-dimensional sensor array based on simultaneous variation of the optical properties (fluorescence, light scattering and UV-vis absorption) of gold-silver alloy nanocluster (AuAgNCs)-gold nanoparticle (AuNPs) composite for the rapid identification of 13 sulfur-containing species and sulfur oxidizing bacteria. The sensor array is fabricated based on the strong coordination interactions between sulfur-containing compounds and AuAgNCs on the surface of AuNPs. The sulfur species of interest exhibit different affinities towards AuAgNCs and generate unique optical properties. These response patterns could divide the analytes into three categories including organic sulfide, inorganic sulfide and thiols. 13 types of sulfur species including cystine, methionine, GSSG, S²⁻, SO3²⁻, S2O3²⁻, S2O7²⁻, S2O8²⁻, S4O6²⁻, GSH, N-acetyl-L-cysteine, homocysteine and cysteine can be well distinguished by the sensor array with principal component analysis (PCA) at 0.5 μM. Moreover, sulfur oxidizing bacteria and non-sulfur bacteria can also be well discriminated at a level of OD600=0.005.
An enhancement of the reactional wettability variation (RWV) sensing strategy is achieved based on the wettability switch of a nanoneedle surface. The sensor unit is formed by coating hydrophobic azoimidazole compounds, as the responder compounds onto the originally hydrophilic surface of cobalt hydroxide nanoneedles. The complexation reaction between metal ions and azoimidazole ligands etches the hydrophobic coating and switches the surface wettability, making the surface hydrophilic again. This switch is revealed by a decrease in the static contact angle (CA) and an increase in the sliding angle of the surface. The reactivity is tuned by the derivatization and conformational manipulation of the azoimidazole compounds. A sensor array composed of six as-tuned sensor units is constructed to distinguish among the species and concentrations of Fe ³⁺ , Ni ²⁺ and La ³⁺ at a low limit of 10 ⁻⁶ M using the chemometric method of principal component analysis (PCA). In addition, a new on-site detection strategy is developed based on PCA of the sliding angle, which can be measured conveniently and swiftly with a smartphone app and a commercially available setup. The application of the general RWV strategy is envisioned to open new possibilities for on-site detection.
In this contribution, a chiral N-propargylamide monmer (R and S) was synthesized and used as comonomer to prepare hydrophilic polyacetylene (HPA) bearing polymerizable vinyl groups in the presence of (nbd)Rh⁺B⁻(C6H5)4. The obtained HPA chains could form single-handed helical structure in water and showed intense optical activity. Taking advantage of the hydrophilic and polymerizable moieties, HPA was further used as macromer to prepare hydrogels in deionized water via free radical polymerization, using N-isopropylacrylamide (NIPAm) as comonomer, N,N-methylenebisacrylamide (BIS) as crosslinker, ammonium persulphate (APS) and N,N,N,N-tetramethylethylenediamine (TEMEDA) as redox initiator. The as-prepared hydrogels exhibited optical activity, thermal responsibility and biocompatibility. More interestingly, the hydrogels showed enantio-differentiating release ability towards mandelic acid enantiomers, demonstrating the potential applications of the novel optically active hydrogels in chiral drug delivery fields.
Thiols play a crucial role in various biological processes, and the discrimination of thiols in biofluids is a significant but difficult issue. Herein, a facile label-free non-invasive fluorescent sensor array has been presented based on PDA/PEIn-Cu2+ in three different pH buffer for pattern discrimination of thiols and chiral recognition of cysteine (Cys) enatiomers in biofluids toward health monitoring. The proposed sensor array was fabricated based on that Cu2+ has strong affinity toward thiols, which prevents Cu2+ from binding PDA/PEIn, and the fluorescence property of PDA/PEIn was recovered to a certain degree. Different thiols exhibited different affinities toward Cu2+, generating distinct fluorescence responses pattern. These response patterns are characteristic for each thiol and can be discriminated by principal component analysis (PCA). In this work, three types of PDA/PEI48-Cu2+ sensors (PDA/PEI48-Cu2+4, PDA/PEI48-Cu2+4.5 and PDA/PEI48-Cu2+5) were prepared by using acetate buffer with different pH (at 4, 4.5, and 5) to form our proposed sensor array, which could realize the pattern discrimination of 8 thiols. Moreover, we successfully realized the sensitivity and selectivity assays to these thiols. Furthermore, the proposed sensor array could discriminate the mixtures of thiols as well as chiral recognition of mixtures of Cys enantiomers, promising its potential practical usage. Significantly, the resultant practical application in real samples showed that it could be a fascinating assay for the development of non-invasive diagnosis. This method promises the facile, sensitive and powerful discrimination of thiols in biofluids and would sprout more relevant strategies toward broader applications.
Skin-based wearable devices have a great potential that could result in a revolutionary approach to health monitoring and diagnosing disease. With continued innovation and intensive attention to the materials and fabrication technologies, development of these healthcare devices is progressively encouraged. This article gives a concise, although admittedly non-exhaustive, didactic review of some of the main concepts and approaches related to recent advances and developments in the scope of skin-based wearable devices (e.g. temperature, strain, biomarker-analysis werable devices, etc.), with an emphasis on emerging materials and fabrication techniques in the relevant fields. To give a comprehensive statement, part of the review presents and discusses different aspects of these advanced materials, such as the sensitivity, biocompatibility and durability as well as the major approaches proposed for enhancing their chemical and physical properties. A complementary section of the review linking these advanced materials with wearable device technologies is particularly specified. Some of the strong and weak points in development of each wearable material/device are highlighted and criticized. Several ideas regarding further improvement of skin-based wearable devices are also discussed.
Rapid, multiplexed, sensitive and specific identification and quantitative detection of nitric oxide (NO) are in great demand in biomedical science. Herein, a novel multifunctional probe based on the intramolecular LRET (luminescence resonance energy transfer) strategy, TRP-NO, was designed for the highly sensitive and selective ratiometric and luminescence lifetime detection of lysosomal NO. Before reaction with NO, the emission of the rhodamine moiety in TRP-NO is switched off, which prevents the LRET process, so that the probe emits only the long-lived Tb³⁺ luminescence. However, upon reaction with NO, accompanied by the turn-on of rhodamine emission, the LRET from the Tb³⁺-complex moiety to rhodamine moiety occurs, which results in a remarkable increase of the rhodamine emission and decrease of the Tb³⁺ emission. After the reaction, the intensity ratio of the rhodamine emission to the Tb³⁺ emission, I565/I540, was found to be 28.8-fold increased, and the dose-dependent enhancement of the I565/I540 value showed a good linearity upon the increase of NO concentration. In addition, a dose-dependent luminescence lifetime decrease was distinctly observed between the average luminescence lifetime of the probe and NO concentration, which provides a ∼10-fold contrast window for the detection of NO. These unique properties allowed TRP-NO to be conveniently used as a time-gated luminescence probe for the quantitative detection of NO using both luminescence intensity ratio and luminescence lifetime as signals. The applicability of TRP-NO for ratiometric time-gated luminescence imaging of NO in living cells was investigated. Meanwhile, dye co-localization studies confirmed a quite precise distribution of TRP-NO in lysosomes by confocal microscopy imaging. Furthermore, the practical applicability of TRP-NO was demonstrated by the visualization of NO in Daphnia magna. All of the results demonstrated that TRP-NO could serve as a useful tool for exploiting and elucidating the function of NO at sub-cellular levels with high specificity, accuracy and contrast.
We report on an artificially intelligent nanoarray based on molecularly modified gold nanoparticles and a random network of single-walled carbon nanotubes for noninvasive diagnosis and classification of a number of diseases from exhaled breath. The performance of this artificially intelligent nanoarray was clinically assessed on breath samples collected from 1404 subjects having one of 17 different disease conditions included in the study or having no evidence of any disease (healthy controls). Blind experiments showed that 86% accuracy could be achieved with the artificially intelligent nanoarray, allowing both detection and discrimination between the different disease conditions examined. Analysis of the artificially intelligent nanoarray also showed that each disease has its own unique breathprint, and that the presence of one disease would not screen out others. Cluster analysis showed a reasonable classification power of diseases from the same categories. The effect of confounding clinical and environmental factors on the performance of the nanoarray did not significantly alter the obtained results. The diagnosis and classification power of the nanoarray was also validated by an independent analytical technique, i.e., gas chromatography linked with mass spectrometry. This analysis found that 13 exhaled chemical species, called volatile organic compounds, are associated with certain diseases, and the composition of this assembly of volatile organic compounds differs from one disease to another. Overall, these findings could contribute to one of the most important criteria for successful health intervention in the modern era, viz. easy-to-use, inexpensive (affordable), and miniaturized tools that could also be used for personalized screening, diagnosis, and follow-up of a number of diseases, which can clearly be extended by further development.
A stretchable polyaniline nanofiber temperature sensor array with an active matrix consisting of single-walled carbon nanotube thin film transistors is demonstrated. The integrated temperature sensor array gives mechanical stability under biaxial stretching of 30%, and the resultant spatial temperature mapping does not show any mechanical or electrical degradation.
The detection of many diseases is missed because of delayed diagnoses or the low efficacy of some treatments. This emphasizes the urgent need for inexpensive and minimally invasive technologies that would allow efficient early detection, stratifying the population for personalized therapy, and improving the efficacy of rapid bed-side assessment of treatment. An emerging approach that has a high potential to fulfill these needs is based on so-called "volatolomics", namely, chemical processes involving profiles of highly volatile organic compounds (VOCs) emitted from body fluids, including breath, skin, urine and blood. This article presents a didactic review of some of the main advances related to the use of nanomaterial-based solid-state and flexible sensors, and related artificially intelligent sensing arrays for the detection and monitoring of disease with volatolomics. The article attempts to review the technological gaps and confounding factors related to VOC testing. Different ways to choose nanomaterial-based sensors are discussed, while considering the profiles of targeted volatile markers and possible limitations of applying the sensing approach. Perspectives for taking volatolomics to a new level in the field of diagnostics are highlighted.
Simple thiol derivatives, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play key roles in biological processes, and the fluorescent probes to detect such thiols in vivo selectively with high sensitivity and fast response times are critical for understanding their numerous functions. However, the similar structures and reactivities of these thiols pose considerable challenges to the development of such probes. This review focuses on various strategies for the design of fluorescent probes for the selective detection of biothiols. We classify the fluorescent probes for discrimination among biothiols according to reaction types between the probes and thiols such as cyclization with aldehydes, conjugate addition-cyclization with acrylates, native chemical ligation, and aromatic substitution-rearrangement.
We report on ultrasensitive molecularly-modified silicon nanowire field effect transistor that marries between the lock-and-key and cross-reactive sensing worlds for the diagnosis of (gastric) cancer from exhaled volatolome. The sensor is able to selectively detect VOCs that are linked with gastric cancer conditions in exhaled breath and to discriminate them from environmental VOCs that would exist in exhaled breath samples but do not relate to the gastric cancer per se. Using breath samples collected from real patients with gastric cancer and from volunteers that have no cancer, blind analysis validated the ability of the reported sensor to discriminate between gastric cancer and control conditions, irrespective of important confounding factors such as tobacco consumption and gender with >85% accuracy. The reported sensing approach paves the way for utilizing the power of silicon nanowires in simple, inexpensive, portable, and non-invasive diagnosis of both cancer and other diseases conditions.
A good number of abstracts and research articles (in total 74) published, so far, for evaluating antioxidant activity of various samples of research interest were gone through where 407 methods were come across, which were repeated from 29 different methods. These were classified as in vitro and in vivo methods. And those are described and discussed below in this review article. In the later part of this review article, frequency of in vitro as well as in vivo methods is analyzed with a bar diagram. Solvents are important for extracting antioxidants from natural sources. Frequency of solvents used for extraction is also portrayed and the results are discussed in this article. As per this review there are 19 in vitro methods and 10 in vivo methods that are being used for the evaluation of antioxidant activity of the sample of interest. DPPH method was found to be used mostly for the in vitro antioxidant activity evaluation purpose while LPO was found as mostly used in vivo antioxidant assay. Ethanol was with the highest frequency as solvent for extraction purpose.
The role of oxidative stress in the genesis of various types of cancers is well established. Several chemical, cell culture and animal studies also indicate that antioxidants may slow or even prevent the development of cancer. Brain is considered abnormally sensitive to oxidative damage as brain tissue has high rate of oxygen consumption, high lipid content and relatively low antioxidant defenses, compared to other tissues.
The study design chosen for the present study was cross sectional. The biochemical parameters that were estimated in saliva manually using spectrophotometric methods were ferric reducing antioxidant power (FRAP) assay--a direct measure of total antioxidant activity of biological fluids and protein thiols. The physical parameters of saliva that were also assessed were salivary flow rate, pH of the saliva and the osmolality of the saliva.
The mean values of salivary flow rate and pH were significantly decreased among malignant and benign tumor patients whereas the salivary osmolality was significantly increased in both the groups of patients. The mean values of salivary FRAP were significantly reduced among malignant and benign tumor patients. However, the salivary protein thiols were significantly increased in these patients.
Hence with these observations it can be concluded that in saliva, besides the physical characteristics, salivary FRAP and protein thiol levels are appropriate indicators of the antioxidant status in brain tumor patients.
We report a method to form multifunctional polymer coatings through simple dip-coating of objects in an aqueous solution of
dopamine. Inspired by the composition of adhesive proteins in mussels, we used dopamine self-polymerization to form thin,
surface-adherent polydopamine films onto a wide range of inorganic and organic materials, including noble metals, oxides,
polymers, semiconductors, and ceramics. Secondary reactions can be used to create a variety of ad-layers, including self-assembled
monolayers through deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioinert
and bioactive surfaces via grafting of macromolecules.
Latent fingerprints (LFPs) are highly specific to individuals, and LFP imaging has played an important role in areas such as forensic investigation and law enforcement. Presently, LFP imaging still faces considerable problems, including background interference and destructive and complex operations. Herein, we have designed a background-free, nondestructive, and easy-to-perform method for LFP imaging based on pH-mediated recognition of LFPs by carboxyl group-functionalized Zn2GeO4:Mn (ZGO:Mn-COOH) persistent luminescence nanorods (PLNRs). By simply adjusting the pH of the ZGO:Mn-COOH colloid dispersion to a certain acidic range, the negatively charged ZGO:Mn-COOH readily binds to protonated fingerprint ridges via electrostatic attraction. The ZGO:Mn-COOH colloid dispersion can be stored in portable commercial spray bottles, and the LFPs have been easily detected in situ by simply dropping the colloid dispersion on the LFPs. Moreover, since the ZGO:Mn-COOH can remain luminescent after excitation ceases, background color and background fluorescence interference were efficiently removed by simply capturing the luminescent LFP images after the excitation ceased. The entire LFP imaging process can be easily conducted without any destructive or complex operations. Due to the great versatility of the developed method for LFP imaging, clear LFP images with well-resolved ridge patterns were obtained. The designed background-free, nondestructive, and easy-to-perform LFP imaging strategy has great potential for future applications, such as forensic investigations and law enforcement. Open image in new window
This article is an overview of the present and ongoing developments in the field of nanomaterial-based sensors for enabling fast, relatively inexpensive and minimally (or non-) invasive diagnostics of health conditions with follow-up by detecting volatile organic compounds (VOCs) excreted from one or combination of human body fluids and tissues (e.g., blood, urine, breath, skin). Part of the review provides a didactic examination of the concepts and approaches related to emerging sensing materials and transduction techniques linked with the VOC-based non-invasive medical evaluations. We also present and discuss diverse characteristics of these innovative sensors, such as their mode of operation, sensitivity, selectivity and response time, as well as the major approaches proposed for enhancing their ability as hybrid sensors to afford multidimensional sensing and information-based sensing. The other parts of the review give an updated compilation of the past and currently available VOC-based sensors for disease diagnostics. This compilation summarizes all VOCs identified in relation to sickness and sampling origin that links these data with advanced nanomaterial-based sensing technologies. Both strength and pitfalls are discussed and criticized, particularly from the perspective of the information and communication era. Further ideas regarding improvement of sensors, sensor arrays, sensing devices and the proposed workflow are also included.
There is a close correlation between body health and the level of biofluid-derived metal ions, which makes it an attractive model analyte for non-invasive health monitoring. The present work has developed a novel nose/tongue-mimic chemosensor array based on bioinspired polydopamaine/polyethyleneimine copolymers (PDA/PEIn) for label-free fluorescent determination of metal ions in biofluids. Three types of PDA/PEIn (PDA/PEI6, PDA/PEI18 and PDA/PEI48) were prepared by using different concentrations of PEI to construct the proposed sensor array, which would lead to unique fluorescence response patterns upon challenged with metal ions for their pattern discrimination. The results show that as few as 3 PDA/PEIn sensors can successfully realize the largescale sensitive detection of metal ions in biofluids. Moreover, we have demonstrated that PDA/PEIn sensors are qualified for lifetime-based pattern discrimination application. Furthermore, the sensors can distinguish between different concentrations of metal ions, as well as a mixture of different metal ions in biofluids, even the mixtures with different valence states. The method promises the simple, rapid, sensitive, and powerful discrimination of metal ions in accessible biofluids, showing the potential applications in the diagnosis of metal ion-involved diseases.
Fluorescence sensors for biologically active molecules are catching attention due to their good performance and simplicity. Herein, we report a fluorescence sensor for the selective and sensitive detection of dopamine (DA) in aqueous samples. MoS2 nanohybrid material composed of MoS2 quantum dots dispersed over MoS2 nanosheets (MoS2 QDNS) in alkaline medium was employed as the fluorescent probe. In the presence of DA, the photoluminescence intensity of MoS2 QDNS was quenched linearly with increasing concentration of the former. The quenching mechanism was found to operate via Förster resonance energy transfer (FRET), and the inner filter effect (IFE). The QDNS sensor demonstrates high selectivity towards DA, especially in the presence of ascorbic acid and uric acid, which are the most potential interference for DA in biological systems. The sensitivity of the system was as low as 0.9 nM and demonstrated two linear ranges from 2.5 nM to 5.0 μM and from 5.0 μM to 10.4 μM. The sensor demonstrated a remarkable ability in the analysis of real blood samples and showed excellent potential for visual detection.
Metabolism is a fundamental process of life. However, non-invasive measurement of local tissue metabolism is limited today by a deficiency in adequate tools for in vivo observations. We designed a multi-modular platform that explored the relation between local tissue oxygen consumption, determined by label-free optoacoustic measurements of hemoglobin, and concurrent indirect calorimetry obtained during metabolic activation of brown adipose tissue (BAT). By studying mice and humans, we show how video-rate handheld multi-spectral optoacoustic tomography (MSOT) in the 700-970 nm spectral range enables non-invasive imaging of BAT activation, consistent with positron emission tomography findings. Moreover, we observe BAT composition differences between healthy and diabetic tissues. The study consolidates hemoglobin as a principal label-free biomarker for longitudinal non-invasive imaging of BAT morphology and bioenergetics in situ. We also resolve water and fat components in volunteers, and contrast MSOT readouts with magnetic resonance imaging data.
Background: Myopia remains a leading cause of vision loss and visual disability in Ukraine (75%) and one of the most common ocular disorders worldwide. Most of available biological materials like blood and tear fluid can be used to measure the levels of these compounds, and thus to assess the relative balance between lipid peroxidation (LPO) and antioxidant system (AOS) in myopes. This will enable to find a pharmacological way for normalizing this balance in order to prevent degenerative retinal changes, and to stop the progression of myopia. Purpose: To evaluate the antioxidant status in patients with different severity of myopia based on the activity of enzymes (glutathione-S-Transferase (GST), catalase (CAT), and glutathione peroxidase (GPx)) in their tear fluid and of sulfur-containing protein groups in their blood and tear fluid before and after treatment with Fakovit, a thiol agent. Materials and Methods: The Facovit treatment group included 67 myopes (low myopes, n = 26; medium myopes, n = 22; high myopes, n = 19) aged 12-24 years, whereas the control group included 67 aged-matched who did not receive Facovit treatment. In addition, 30 aged-matched healthy individuals were included into the study. Results: At baseline, GPx neutralized lipid hydroperoxides too slowly, and GST activity was markedly inhibited, with GST activity in the tear fluid and in the blood in low, moderate and high myopes of the Fakovit treatment group being statistically significantly lower than in normal individuals. In addition, CAT activity in the tear fluid in moderate and high myopes of this group was low. The baseline levels of free and protein-bound sulphydryl and disulphide groups in the tear fluid in low, moderate and high myopes of the Fakovit treatment group were abnormal, indicating substantial abnormalities of the AOS, with the tear fluid levels of free sulfhydryl groups and of protein-bound sulfhydryl groups being statistically significantly lower, and with the tear fluid levels of free disulphide groups and of protein-bound disulphide groups being higher than in normal individuals. Biochemical study demonstrated that the treatment including the thiol agent resulted in a substantial increase in the activity of enzymes (GPx and GST) of the detoxification system. Consclusion: Fakovit was found to have a substantial antioxidation effect on thiols in myopia, with increase in the levels of free sulfhydryl groups and decrease in the levels of protein-bound disulphide groups in the blood and tear fluid.
In the past three decades, our understanding of brain-behavior relationships has been significantly shaped by research using non-invasive brain stimulation (NIBS) techniques. These methods allow non-invasive and safe modulation of neural processes in the healthy brain, enabling researchers to directly study how experimentally altered neural activity causally affects behavior. This unique property of NIBS methods has, on the one hand, led to groundbreaking findings on the brain basis of various aspects of behavior and has raised interest in possible clinical and practical applications of these methods. On the other hand, it has also triggered increasingly critical debates about the properties and possible limitations of these methods. In this review, we discuss these issues, clarify the challenges associated with the use of currently available NIBS techniques for basic research and practical applications, and provide recommendations for studies using NIBS techniques to establish brain-behavior relationships.
Early detection of breast cancer is a critical component in patient prognosis and establishing effective therapy regimens. Here, we developed an easily accessible yet potentially powerful sensor to detect cancer cell targets by utilizing seven dual-ligand cofunctionalized gold nanoclusters (AuNCs) as both effective cell recognition elements and signal transducers. On the basis of this AuNC multichannel sensor, we have successfully distinguished healthy, cancerous and metastatic human breast cells with excellent reproducibility and high sensitivity. Triple negative breast cancer cells (TNBCs), which exhibit low expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2, were identified. The high accuracy of the blind breast cell sample tests further validates the practical application of the sensor array. In addition, the versatility of the sensor array is further justified by identifying amongst distinct cell types, different cell concentrations and cell mixtures. Notably, the drug-resistant cancer cells can also be efficiently discriminated. Furthermore, the dual-ligand cofunctionalized AuNCs can efficiently differentiate different cells from the peripheral blood of tumor-free and tumor-bearing mice. Taken together, this fluorescent AuNCs based array provides a powerful cell analysis tool with potential applications in biomedical diagnostics.
A simple and novel method for evaluating antioxidants in complex biological fluids has been developed based on the interaction of dye-labeled single-strand DNA (ssDNA) and polydopamine (PDA). Due to the interaction between ssDNA and PDA, the fluorescence of dye-labeled ssDNA (e.g. FITC-ssDNA, as donor) can be quenched by PDA (as acceptor) to the fluorescence “off” state through Förster resonance energy transfer (FRET). However, in the presence of various antioxidants, such as glutathione (GSH), ascorbic acid (AA), cysteine (Cys) and homocysteine (Hcys), the spontaneous oxidative polymerization reaction from DA to PDA would be blocked, resulting in the freedom of FITC-ssDNA and leading to the fluorescence “on” state. The sensing system shows great sensitivity for the monitoring of antioxidants in a fluorescent “turn on” format. The new strategy also exhibits great selectivity and is free from the interferences of amino acids, metal ions and the biological species commonly existing in brain systems. Moreover, by combining the microdialysis technique, the present method has been successfully applied to monitor the dynamic changes of the striatum antioxidants in rat cerebrospinal microdialysates during the normal/ischemia/reperfusion process. This work establishes an effective platform for in vivo monitoring antioxidants in cerebral ischemia model, and promises new opportunities for the research of brain chemistry, neuroprotection, physiological and pathological events.
Two of the biggest challenges in medicine today are the need to detect diseases in a non-invasive manner, and to differentiate between patients using a single diagnostic tool. The current study targets these two challenges by developing a molecularly-modified Silicon Nanowire Field Effect Transistors (SiNW FETs) and showing its use in the detection and classification of many disease breathprints (lung cancer, gastric cancer, asthma and Chronic Obstructive Pulmonary Disease). The fabricated SiNW FETs are characterized and optimized based on a training set that correlated their sensitivity and selectivity towards volatile organic compounds (VOCs) linked with diseased states. The best sensors obtained in the training set are then examined under real-world clinical conditions, using breath samples from 374 subjects. Analysis of the clinical samples showed that the optimized SiNW FETs can detect and discriminate between almost all binary comparisons of the diseases under examination with >80% accuracy. Overall, this approach has the potential to support detection of many diseases in a direct positive way, which can reassure patients and prevent numerous negative investigations.
An ambipolar poly(diketopyrrolopyrrole-terthiophene)-based field-effect transistor (FET) sensitively detects xylene isomers at low ppm levels with multiple sensing features. Combined with pattern-recognition algorithms, a sole ambipolar FET sensor, rather than arrays of sensors, can discriminate highly similar xylene structural isomers from one another.
A simple colorimetric sensor array technique was developed for the detection of various different nanoparticles (NPs) in aqueous solutions. The sensor array consists of five different cross-reactive chemoresponsive dyes, whose visible absorbances change in response to their interactions with NPs. Although no single dye is specific for any one NP, the pattern of color changes for all dyes provides a unique molecular fingerprint for each type of NP studied. Based on the responses of various dyes, a semiquantitative determination of concentration of each type of NP could also be accomplished with excellent sensitivity (<100 ng/mL). A variety of chemically distinct NPs were unambiguously identified using a standard chemometric approaches, including gold nanospheres (2 through 40 nm diameter), gold nanorods (2.4 and 3.5 aspect ratios), and multifunctional carbon nanospheres without errors in 112 trials. This colorimetric approach may pave the way for a fast, reliable, and inexpensive method to detect nanopollution and to characterize the physiochemical properties of NPs.
Copper ion (Cu(2+) ) and L-cysteine (CySH) are closely correlated with physiological and pathological events of Alzheimer's Disease (AD), however the detailed mechanism is still unclear, mainly owing to a lack of accurate analytical methods in live brains. Herein, we report a single biosensor for electrochemical ratiometric detection of Cu(2+) and CySH in live rat brains with AD. N,N-di-(2-picoly)ethylenediamine (DPEA) is first synthesized for specific recognition of Cu(2+) to form a DPEA-Cu(2+) complex. This complex shows high selectivity for CySH owing to the release of Cu(2+) from the complex through CySH binding to Cu(2+) center. In parallel, 5'-MB-GGCGCGATTTTTTTTTTTTT-SH-3' (HS-DNA-MB, MB=Methylene Blue) is designed as an inner-reference for providing a built-in correction to improve the accuracy. As a result, combined with the amplified effect of Au nanoleaves, our single ratiometric biosensor can be successfully applied in real-time detection of Cu(2+) and CySH in the live rat brains with AD. To our knowledge, this is the first report on the accurate concentrations of Cu(2+) and CySH in live rat brains with AD.
An array of highly sensitive pressure sensors entirely made of biodegradable materials is presented, designed as a single-use flexible patch for application in cardiovascular monitoring. The high sensitivity in combination with fast response time is unprecedented when compared to recent reports on biodegradable pressure sensors (sensitivity three orders of magnitude higher), as illustrated by pulse wave velocity measurements, toward hypertension detection.
We presented an extensible multidimensional sensor with conjugated nonspecific dye-labeled DNA sequences absorbed onto gold nanoparticles (DNA-AuNPs) as receptors. At the presence of target protein, DNA was removed from the surface of AuNPs due to the competitive binding, which resulted in a red-to-blue color change along with salt-induced aggregation of AuNPs for colorimetric analysis and fluorescent 'turn-on' signal of the labeled dye for fluorescence analysis. The orthogonal and complementary fluorescent and colorimetric signals obtained from each protein were applied to the distinguishment of different proteins. By simply changing the DNA sequences, more dual-channel sensing elements could be easily obtained and added into this multidimensional sensor. This enhanced its discriminating power to the proteins. With three sensing elements, our extensible multidimensional sensing platform exhibited excellent discrimination ability. 11 proteins at the concentration of 50 nM had been classified with accuracies of 100% by using linear discriminant analysis (LDA). Remarkably, two similar proteins (BSA and HSA) at various concentrations and the mixture of these two proteins with different molar ratios had been successfully discriminated in one LDA plot as well. Furthermore, in the presence of human urine sample, 10 proteins at 1.0 μM could also be well discriminated. The accuracy of discrimination of unknown samples was all 100% for these experiments. This strategy is a complement of the multidimensional sensing system and traditional sensor platform, offering a new way to develop sensitive array sensing systems.
ABSTRACT A novel core-shell hybrid system based on upconversion fluorescent nanoparticles (UCNPs) and dopamine-melanin, has been developed for evaluation of antioxidant capacity of biological fluids. In this approach, dopamine-melanin nanoshells facilely formed on the surface of UCNPs act as ultra-efficient quencher for upconversion fluorescence, attributing to a photo-induced electron transfer mechanism. This spontaneous oxidative polymerization of dopamine induced quenching effect could be effectively prevented by the presence of various antioxidants (typically biothiols, ascorbic acid (Vitamin C) and Trolox). The chemical response of the UCNPs@dopamine-melanin hybrid system exhibited great selectivity and sensitivity toward antioxidants relative to other compounds at 100-fold higher concentration. Satisfactory correlation was established between the ratio of "anti-quenching" fluorescence intensity and the concentration of antioxidants. Besides the response of upconversion fluorescence signal, specific evaluation process for antioxidants could be visualized by the color change from colorless to dark grey accompanied with spontaneous oxidation of dopamine. The near infrared (NIR) excited upconversion nanoparticle-based antioxidant capacity assay (UNACA) platform was further used to evaluate the antioxidant capacity of cell extracts and human plasma, satisfied sensitivity, repeatability and recovery rate were obtained. This approach features easy preparation, fluorescence/visual dual mode detection, high specificity to antioxidants and enhanced sensitivity with NIR excitation, showing great potentials for screening and quantitatively evaluating antioxidants in biological systems.
The unpolarized absorption and circular dichroism spectra of the
fundamental vibrational transitions of the chiral molecule,
4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields
are obtained using Density Functional Theory (DFT), MP2, and SCF
methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use
the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP)
density functionals. Mid-IR spectra predicted using LSDA, BLYP, and
B3LYP force fields are of significantly different quality, the B3LYP
force field yielding spectra in clearly superior, and overall excellent,
agreement with experiment. The MP2 force field yields spectra in
slightly worse agreement with experiment than the B3LYP force field. The
SCF force field yields spectra in poor agreement with experiment.The
basis set dependence of B3LYP force fields is also explored: the 6-31G
and TZ2P basis sets give very similar results while the 3-21G basis set
yields spectra in substantially worse agreements with experiment.
An important advantage of pattern-based chemosensor sets is their potential to detect and differentiate a large number of analytes with only few sensors. Here we test this principle at a conceptual limit by analyzing a large set of metal ion analytes covering essentially the entire periodic table, employing fluorescent DNA-like chemosensors on solid support. A tetrameric "oligodeoxy-fluoroside" (ODF) library of 6,561 members containing metal-binding monomers was screened for strong responders to 57 metal ions in solution. Our results show that a set of nine chemosensors could successfully discriminate the 57 species, including alkali, alkaline earth, post-transition, transition and lanthanide metals. As few as six ODF chemosensors can detect and differentiate 50 metals at 100 µM, and a blind test with 50 metals further confirmed the discriminating power of the ODFs.
Rational approaches to engineering polydopamine films with tailored properties for surface coating and functionalization are currently challenged by the lack of detailed information about the polymer structure and the mechanism of buildup. Using an integrated chemical and spectroscopic approach enables the demonstration of: a) a three-component structure of polydopamine, comprising uncyclized (catecholamine) and cyclized (indole) units, as well as novel pyrrolecarboxylic acid moieties; b) remarkable variations in the relative proportions of the cyclized and uncyclized units with starting dopamine concentration; c) the occurrence of oligomer components up to the tetramer level; d) the covalent incorporation of Tris buffer; and e) the role of dopamine quinone as a crucial control point for directing the buildup pathways and tuning the properties. The importance of the uncyclized amine-containing units in polydopamine adhesion is also highlighted. The proper selection of substrate concentration and buffer is thus proposed as a practical means of tailoring polydopamine functionality via control of competing pathways downstream of dopamine quinone.
Polydopamine is fast becoming a popular polymer that is receiving increased attention from scientists from different areas of expertise. The physicochemical properties of polydopamine, as well as its potential applications are reviewed. Similar to the foot protein in mussels, polydopamine has also shown versatile adhesion capability to virtually all types of surfaces, and provides a general surface-coating strategy for researchers to functionalize some specific technique-related substrates. It easily reacts with numerous amine- and thiol-containing molecules based on Michael-type addition and Schiff base reactions and has strong metal chelating/redox capabilities, which imparts to materials with structural flexibility and the ability to tailor the coatings for producing diverse hybrid materials with specific functionalities. During investigations of the polymerization process, specific attention should be drawn to the thickness of the polydopamine film deposited on the substrates.
The use of molecularly modified Si nanowire field effect transistors (SiNW FETs) for selective detection in liquid phase has been successfully demonstrated. In contrast, selective detection of chemical species in the gas phase has been rather limited. In this paper, we show that the application of artificial intelligence on deliberately controlled SiNW FET device parameters can provide high selectivity towards specific volatile organic compounds (VOCs). The obtained selectivity allows identifying VOCs in both single-component and multi-component environments as well as estimating the constituent VOC concentrations. The effect of the structural properties (functional group and/or chain length) of the molecular modifications on the accuracy of VOC detection is presented and discussed. The reported results have the potential to serve as a launching pad for the use of SiNW FET sensors in real-world counteracting conditions and/or applications.
Inspired by the bio-adhesive ability of the marine mussel, a simple, versatile and powerful synthesis strategy was developed to prepare highly reproducible and permselective molecular sieve membranes by using polydopamine as a novel covalent linker. Attributing to the formation of strong covalent and non-covalent bonds, ZIF-8 nutrients are attracted and bound to the support surface, thus promoting the ZIF-8 nucleation and the growth of uniform, well intergrown and phase-pure ZIF-8 molecular sieve membranes. The developed ZIF-8 membranes show high hydrogen selectivity and thermal stability. At 150 ºC and 1 bar, the mixture separation factors of H2/CO2, H2/N2, H2/CH4, and H2/C3H8 are 8.9, 16.2, 31.5 and 712.6, with H2 permeances higher than 1.8 x 10-7 mol•m-2•s-1•Pa-1, which is promising for hydrogen separation and purification.
The adhesive proteins secreted by mussels are applied to the surface modification of a wide range of inorganic and organic materials, resulting in the fabrication of multifunctional coatings for biomedical applications. The adhesive polymer film is formed from dopamine with a primary amine functional group while the surface-active polydopamine readily adhere to all surfaces including noble metals and metals with native oxide surfaces. Advances in soft ionization mass spectroscopy have enabled the characterization of the adhesives of mussels on smooth substrates. A mass-spectrometry technique detects the presence of dihyroxyindole oligomers in the adsorbed dopamine polymer, indicating that a similar oxidation mechanism is involved in the dopamine-derived polymer coating.
We developed a colorimetric sensor array with reported protein aptamers as nonspecific receptors. We found that different target proteins could make the aptamer-protected AuNPs exhibit different aggregation behaviors in the presence of high concentration salt and cause various color change. Based on this phenomenon, we applied a series of reported protein aptamers as receptor array obtaining a distinct response pattern to each target protein. Seven proteins have been well distinguished with the naked eye at 50 nM level. Cancerous human cells have also been discriminated from noncancerous cells. This method is simple, label-free and sensitive. It will broaden the application filed of plasmonic nanoparticle-based sensors and give new direction of developing sensitive array sensing systems.
A facile, economic and green one-step hydrothermal synthesis route using dopamine as source towards photoluminescent carbon nanoparticles (CNPs) is proposed. The as-prepared CNPs have an average size about 3.8 nm. The emission spectra of the CNPs are broad, ranging from approximately 380 (purple) to approximately 525 nm (green), depending on the excitation wavelengths. Due to the favorable optical properties, the CNPs can readily enter into A549 cells and has been used for multicolor biolabeling and bioimaging. Most importantly, the as-prepared CNPs contain distinctive catechol groups on their surfaces. Due to the special response of catechol groups to Fe(3+) ions, we further demonstrate that such wholly new CNPs can serve as a very effective fluorescent sensing platform for label-free sensitive and selective detection of Fe(3+) ions and dopamine with a detection limit as low as 0.32 μM and 68 nM, respectively. The new "mix-and-detect" strategy is simple, green, and exhibits high sensitivity and selectivity. The present method was also applied to the determination of Fe(3+) ions in real water samples and dopamine in human urine and serum samples successfully.
The trolox equivalent antioxidant capacity (TEAC) assay is a popular method for assessing the capacity of a compound to scavenge ABTS radicals (ABTS). Under the conditions in which the assay is performed, the reaction between most antioxidants and ABTS does not reach completion within the time span applied. This leads to an underestimation of the TEAC of these antioxidants. In the present study, incubations with different concentrations of ABTS and a fixed concentration of antioxidant were performed. The decrease in ABTS concentration in 6 min was plotted against the initial concentration of ABTS and fitted by an exponential function. Extrapolation of the fit to an infinite excess of ABTS gives the maximal concentration of ABTS that can be scavenged by the antioxidant at the concentration employed. This can be used to determine the actual TEAC of antioxidants, i.e. the total antioxidant capacity.
Despite the remarkable thermochemical accuracy of Kohn–Sham density-functional theories with gradient corrections for exchange-correlation [see, for example, A. D. Becke, J. Chem. Phys. 96, 2155 (1992)], we believe that further improvements are unlikely unless exact-exchange information is considered. Arguments to support this view are presented, and a semiempirical exchange-correlation functional containing local-spin-density, gradient, and exact-exchange terms is tested on 56 atomization energies, 42 ionization potentials, 8 proton affinities, and 10 total atomic energies of first- and second-row systems. This functional performs significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.
Iron is one of the most abundant metals found in senile plaques of post mortem patients with Alzheimer's disease. However, the interaction mode between iron ions and β-amyloid peptide as well as their precise affinity is unknown. In this study we apply ab initio computational methodology to calculate binding energies of Fe(2+/3+) with the His13-His14 sequence of Aβ, as well as other important ligands such as His6 and Tyr10. Calculations were carried out at the "MP2/6-311+G(2df,2p)"//B3LYP/6-31+G(d) level of theory and solvent effects included by the IEFPCM procedure. Several reaction paths for the binding of imidazole, phenol, and the His13-His14 fragment (modeled by N-(2-(1H-imidazol-4-yl)ethyl)-3-(1H-imidazol-4-yl)propanamide) were sequentially explored. The results show that the most stable complexes containing His13-His14 and phenolate of Tyr10 are the pentacoordinated [Fe(2+)(O-HisHis)(PhO(-))(H(2)O)](+) and [Fe(3+)(N-HisHis)(PhO(-))(H(2)O)](+) compounds and that simultaneous coordination of tyrosine and His13-His14 to Fe(2+/3+) is thermodynamically favorable in water at physiological pH. Computed Raman spectra confirm the conclusion obtained by Miura et al. ( Biochemistry 2000 , 39 , 7024 ) that tyrosine is coordinated to Fe(3+) but do not exclude coordination of imidazoles. Finally, calculations of standard reduction potentials indicate that phenol coordination reduces the redox activity of the iron/Aβ complexes.
Chiral recognition is among the important and special modes of molecular recognition. It is highly desirable to develop a simple, rapid, sensitive, and high-throughput routine assay for chiral recognition. In this study, we demonstrate that nucleotide-capped Ag nanoparticles (AgNPs) can be used as an ultrahigh efficiency enantioseparation and detection platform for d- and l-cysteine. The aggregation of AgNPs is selectively induced by an enantiomer of cysteine, which allowed the rapid colorimetric enantiodiscrimination of cysteine without any prior derivatization and specific instruments and left an excess of the other enantiomer in the solution, thus resulting in enantioseparation. This is the first application of a nucleotide-capped AgNP-based biosensing platform for chiral recognition and opens new opportunities for design of more novel enantiosensing strategies and enantiospecific adsorbents and expansion of its application in different fields.
Exposure of food proteins to certain processing conditions induces two major chemical changes: racemization of all L-amino acids (LAAs) to D-amino acids (DAAs) and concurrent formation of cross-linked amino acids such as lysinoalanine (LAL). The diet contains both processing-induced and naturally-formed DAA. The latter include those found in microorganisms, plants, and marine invertebrates. Racemization impairs digestibility and nutritional quality. Racemization of LAA residues to their D-isomers in food and other proteins is pH-, time-, and temperature-dependent. Although racemization rates of LAA residues in a protein vary, relative rates in different proteins are similar. The nutritional utilization of different DAAs varies widely in animals and humans. Some DAAs may exert both adverse and beneficial biological effects. Thus, although D-Phe is utilized as a nutritional source of L-Phe, high concentrations of D-Tyr in such diets inhibit the growth of mice. Both D-Ser and LAL induce histological changes in the rat kidney. The wide variation in the utilization of DAAs is illustrated by the fact that, whereas D-Meth is largely utilized as a nutritional source of the L-isomer, D-Lys is not. Similarly, although L-CysSH has a sparing effect on L-Meth when fed to mice, D-CysSH does not. Since DAAs are consumed as part of their normal diet, a need exists to develop a better understanding of their roles in foods, microbiology, nutrition, and medicine. To contribute to this effort, this overview surveys our present knowledge of the chemistry, nutrition, safety, microbiology, and pharmacology of DAAs. Also covered are the origin and distribution of DAAs in food and possible roles of DAAs in human physiology, aging, and the etiology and therapy of human diseases.
A correlation-energy formula due to Colle and Salvetti [Theor. Chim. Acta 37, 329 (1975)], in which the correlation energy density is expressed in terms of the electron density and a Laplacian of the second-order Hartree-Fock density matrix, is restated as a formula involving the density and local kinetic-energy density. On insertion of gradient expansions for the local kinetic-energy density, density-functional formulas for the correlation energy and correlation potential are then obtained. Through numerical calculations on a number of atoms, positive ions, and molecules, of both open- and closed-shell type, it is demonstrated that these formulas, like the original Colle-Salvetti formulas, give correlation energies within a few percent.
In this issue of THE JOURNAL, 2 meta-analyses critically review the
coronary heart disease (CHD) risks related to blood levels of homocysteine
and a common variant of methylene tetrahydrofolate reductase (MTHFR), a gene that is known to be an important regulator of homocysteine
metabolism.1- 2 The authors summarize
data on the potential effects of this genetic variant and plasma homocysteine
levels on CHD risk and conclude that the risks are increased modestly. While
the authors do not recommend new approaches to evaluate persons at risk for
CHD, the study findings do provide a perspective on how scientists assess
the utility of newer biomarkers and genetic factors that may contribute to
CHD risk.
Free neutral D-amino acids have previously been detected in human plasma, usually accounting for less than 2% of the total free amino acid concentration (D-amino acid ratio) [Nagata, Y., Masui, R., Akino, T., 1992a. The presence of free D-serine, D-alanine and D-proline in human plasma. Experientia 48, 986-988. Nagata, Y., Yamamoto, K., Shimojo, T., 1992b. Determination of D- and L-amino acids in mouse kidney by high-performance liquid chromatography. Journal of Chromatography 575, 147-152. Nagata, Y., Yamamoto, K., Shimojo, T., Konno, R., Yasumura, Y., Akino, T., 1992c. The presence of free D-alanine, D-proline and D-serine in mice. Biochimca et Biiophysica Acta 1115, 208-211]. In the present study to search for the source of free D-amino acids, D- and L-enantiomers of the major non-essential amino acids, i.e., the free form of serine, alanine, proline, aspartate and glutamate were analyzed by HPLC in human saliva, submandibular glands and oral epithelial cells. The D-enantiomer ratios to total of free alanine or proline were 35% and 20%, respectively, in saliva. The ratios of the other D-amino acids were less than 11%. The effect of ingested food and oral bacteria on the saliva amino acid levels was suggested to be insignificant. D-Alanine and d-aspartate were also detected in the submandibular gland in ratios up to 5%, and D-alanine and d-proline were found in oral epithelial cells in ratios of 18% and 5%, respectively. The submandibular gland and oral epithelial cells are suggested to be possible sources of the saliva D-alanine and D-aspartate.
Antioxidative Status as Assessed by Enzymatic Activity in the Tear Fluid and by the Levels of Sulfur-Containing Protein Groups in the Blood and Tear Fluid of Myopes Before and After Treatment with a Thiol Agent. Oftal'mol. Zh. 2017, 68, 31−39
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