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The demand for fast and ultratrace biomarkers detection is increasing in bioanalytical chemistry. In this work, highly ordered nanowires array and sensor integration are achieved with nanoscale printing approach. Negatively charged poly(3,4‐ethylenedioxythiophene)–poly(styrenesulfonate) doped with positively charged PEGylated biotin‐derivatized polyelectrolytes results a direct biofunctionalization on the nanowire surface without multiple postmodification steps. It provides homogeneous dispersed biofunctional sites and nonfouling surface on the nanowires. The ordered nanowires array enables the immunosensor to detect biotargets quickly and ultrasensitively. The nanowires impedimetric immunosensor is demonstrated for specific biomarkers detection and achieved a minimum responsive concentration as low as 10 pg mL−1 for protein biomarker and 10 CFU mL−1 for pathogen. A kind of biotin functionalization ink is achieved by doping with PEGylated biotin‐derivatized polyelectrolytes which enables a direct biofunctionalization on the nanowire surface. Then an immunosensor based on highly ordered nanowires array is fabricated by nanoscale printing approach. This sensor can be a general platform for different materials and various bioanalytical applications with ultrahigh sensitivity, trace detection, and fast response.
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... Commercially available conductive polymers such as poly (3, 4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) are doped with PEGlated biotin-derivatized polyelectrolytes and printed on the nanowire surface, as shown in Figure 5i. This highly ordered nano-array setup could detect E. coli as low as 10 CFU/mL . Rolling circle amplification (RCA) is a powerful method for DNA amplification, and the authors employed the technique to enhance the detection sensitivity of E. coli O157:H7 in the microfluidic system. ...
... As stated above, detection systems for infectious pathogens have started exploring the potential application of smart materials to develop robust and high throughput technology. A brief summary of the emerging smart materials for microbial pathogens is shown in Table 3.  (iv) Wide detection array (v) Relatively large bandwidth terfaces (iv) Tunability of the slowdown factor in given structure Ionic Liquid based systems (i) Both conductor and binder (ii) Good catalytic ability and super sensitivity (iii) High thermal stability (i) Relatively expensive as compared to conventional organic solvents (ii) High cytotoxicity (iii) Mostly limited to electro-analytical system 10 2 CFU/mL  10 3 CFU/mL  Responsive Polymer based system (i) Multifunctionality (ii) Structural stability (iii) Facile integration in the detection devices (iv) Tunable detection sensitivity (i) Tedious synthesis process of the designed responsive polymer (ii) Lack of toxicity data profile 10 CFU/mL  10 2 CFU/mL  Figure 5. Responsive polymer-based pathogen detection system. (i) (a) Fabrication steps of the immunosensor using conductive polymers such as PEDOT:PSS, and (b) immobilization and detection strategies of E. coli using the nanoarray setup. ...
The development of robust bioanalytical devices and biosensors for infectious pathogens is progressing well with the advent of new materials, concepts, and technology. The progress is also stepping towards developing high throughput screening technologies that can quickly identify , differentiate, and determine the concentration of harmful pathogens, facilitating the decision making process for their elimination and therapeutic interventions in large-scale operations. Recently, much effort has been focused on upgrading these analytical devices to an intelligent technological platform by integrating them with modern communication systems, such as the internet of things (IoT) and machine learning (ML), to expand their application horizon. This review outlines the recent development and applications of bioanalytical devices and biosensors to detect pathogenic microbes in environmental samples. First, the nature of the recent outbreaks of pathogenic microbes such as foodborne, waterborne, and airborne pathogens and microbial toxins are discussed to understand the severity of the problems. Next, the discussion focuses on the detection systems chronologically, starting with the conventional methods, advanced techniques, and emerging technologies, such as biosensors and other portable devices and detection platforms for pathogens. Finally, the progress on multiplex assays, wearable devices, and integration of smartphone technologies to facilitate pathogen detection systems for wider applications are highlighted .
... Besides, the increased surface area by the nanoscale electrodes improves the sensitivity as well as signal to noise ratio of the sensor (Liu et al., 2017). The molecular design of the bio-ink was introduced in detail in our previous work (see also the Supplementary Materials S1) (Xue et al., 2019). Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate J o u r n a l P r e -p r o o f (PEDOT:PSS) is negatively charged and polyelectrolytes (PLL-g-OEG4-Biotin) is positively charged, which leads to the direct formation of bio functionalized nanowires without multiple post modification steps ( Figure s1). ...
The current ongoing outbreak of Coronavirus Disease 2019 (COVID-19) has globally affected the lives of more than one hundred million people. RT-PCR based molecular test is recommended as the gold standard method for diagnosing current infections. However, transportation and processing of the clinical sample for detecting virus require an expert operator and long processing time. Testing device enables on-site virus detection could reduce the sample-to-answer time, which plays a central role in containing the pandemic. In this work, we proposed an intelligent face mask, where a flexible immunosensor based on high density conductive nanowire array, a miniaturized impedance circuit, and wireless communication units were embedded. The sub-100 nm size and the gap between the neighbored nanowires facilitate the locking of nanoscale virus particles by the nanowire arrays and greatly improve the detection efficiency. Such a point-of-care (POC) system was demonstrated for coronavirus ‘spike’ protein and whole virus aerosol detection in simulated human breath. Detection of viral concentration as low as 7 pfu/mL from the atomized sample of coronavirus aerosol mimic was achieved in only 5 mins. The POC systems can be readily applied for preliminary screening of coronavirus infections on-site and may help to understand the COVID-19 progression while a patient is under prescribed therapy.
... To evaluate the thermodynamic favorability for the formation of various supramolecular associates in the chemical systems under study, we performed quantum chemical calculations using density functional theory (DFT) (for details, see the Computational Details section and Supporting Information, Tables S4 and S5). The results of our quantum chemical calculations reveal that (i) self-assembly of PDADMAC and heparin to dimeric associates heparin/PDADMAC is thermodynamically profitable (by 43 6 ] 2+ is dramatic, and removal of small imaginary frequencies does not change the thermodynamics estimation qualitatively. ...
Poly(3,4‐ethylenedioxythiophene) (PEDOT) and its derivatives have demonstrated potential in the development of bioelectrodes because of their superior conductivity. However, developing reliable implanted bioelectrodes requires improvements in biocompatibility and the prevention of nonspecific adhesion. In this study, a six ethylene glycol (EG)‐functionalized EDOTs with three different EG lengths (tri‐EG, tetra‐EG, and hexa‐EG) and two types of end groups, hydroxyl (−OH) and methoxy (−OCH3) is synthesized and systematically investigated. By coating them on gold electrodes using electropolymerization, the surface and electrochemical properties of these functionalized PEDOT‐coated electrodes are investigated. Although PEDOT with −OH groups on the surface is more hydrophilic, those with −OCH3 groups on the surface exhibit higher electrochemical activity and lower impedance. The increase in EG units and −OCH3 groups on the surface effectively reduces the adhesion between the PEDOT and atomic force microscopy tips. PEDOT with longer EG lengths and −OCH3 groups exhibits relatively few adhered platelets, and the results of the analysis of hydrated states through differential scanning calorimetry are consistent with those of the platelet adhesion test. This study suggests that a tetra(EG)‐functionalized PEDOT with −OCH3 groups on the surface is a promising coating for implanted bioelectrode applications. Six ethylene glycol‐functionalized PEDOTs with three different EG lengths and two types of end groups are synthesized and investigated. PEDOT‐EG4‐OMe coating exhibits good electrochemical activity, low impedance, and few adhered platelets. The results of the analysis of hydrated states are consistent with those of the platelet adhesion test.
Recent advances in nano/microfluidics have led to the miniaturization of surface-based chemical and biochemical sensors, with applications ranging from environmental monitoring to disease diagnostics. These systems rely on the detection of analytes flowing in a liquid sample, by exploiting their innate nature to react with specific receptors immobilized on the microchannel walls. The efficiency of these systems is defined by the cumulative effect of analyte detection speed, sensitivity, and specificity. In this perspective, we provide a fresh outlook on the use of important parameters obtained from well-characterized analytical models, by connecting the mass transport and reaction limits with the experimentally attainable limits of analyte detection efficiency. Specifically, we breakdown when and how the operational (e.g., flow rates, channel geometries, mode of detection, etc.) and molecular (e.g., receptor affinity and functionality) variables can be tailored to enhance the analyte detection time, analytical specificity, and sensitivity of the system (i.e., limit of detection). Finally, we present a simple yet cohesive blueprint for the development of high-efficiency surface-based microfluidic sensors for rapid, sensitive, and specific detection of chemical and biochemical analytes, pertinent to a variety of applications.
Detection and recognition of chemical and biological species via sensor electronics are important not only for various sensing applications but also for fundamental scientific understanding. In the past two decades, sensor devices using one-dimensional (1D) nanowires have emerged as promising and powerful platforms for electrical detection of chemical species and biologically relevant molecules due to their superior sensing performance, long-term stability, and ultra-low power consumption. This paper presents a comprehensive overview of the recent progress and achievements in 1D nanowire synthesis, working principles of nanowire-based sensors, and the applications of nanowire-based sensor electronics in chemical and biological analytes detection and recognition. In addition, some critical issues that hinder the practical applications of 1D nanowire-based sensor electronics, including device reproducibility and selectivity, stability, and power consumption, will be highlighted. Finally, challenges, perspectives, and opportunities for developing advanced and innovative nanowire-based sensor electronics in chemical and biological applications are featured.
π-Conjugated polymers (CPs) constitute key elements for the emerging next-generation of bioelectronics, on the basis of their unique optoelectrochemical characteristics, biocompatibility, desired mechanical deformability and printing processability for high-throughput device fabrication. Direct growth of CPs into three-dimensional (3D) structures via solution-based processes has drawn significant attention, as is enabling unprecedented paradigm shift from the conventional 2D thin-film-based electronics. Herein, we address 3D direct writing and meniscus-guided pen writing methods, which are capable of fabricating 3D micro/nanostructures from soluble CPs and CP precursors, and recent advances in these techniques. Moreover, we highlight some of the interesting devices developed and their applications that are featured by unique advantageous properties originating from the fabricated 3D micro/nanostructures of CPs. Finally, we present an outlook on the future direction and possible applications in this field. This perspective mini-review is intended to provide a valuable insight into the emerging field of 3D micro/nanofabrication of CPs and their composites that may inspire the next generation of CP-based (bio)electronics.
Resistive devices composed of one dimensional nanostructures are promising candidate for next generation gas sensors. However, the large-scale fabrication of nanowires is still a challenge, restricting the commercialization of such type of devices. Here, we reported a highly efficient and facile approach to fabricate poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) nanowire chemiresistive type of gas sensor by nanoscale soft lithography. Well-defined sub-100 nm nanowires are fabricated on silicon substrate which facilitates the device integration. The nanowire chemiresistive gas sensor is demonstrated for NH3 and NO2 detection at room-temperature and shows a limit of detection at ppb level which is compatible with nanoscale PEDOT:PSS gas sensors fabricated with conventional lithography technique. In comparison with PEDOT:PSS thin film gas sensor, the nanowire gas sensor exhibits a higher sensitivity and much faster response to gas molecules.
Immunoassays are nowadays a crucial tool for diagnostics and drug development. However, they often involve time-consuming procedures and need at least two antibodies in charge of the capture and detection processes, respectively. This study reports a nanocomposite based on graphene oxide-coated nanopaper (GONAP) facilitating an advantageous immunosensing platform using a single antibody and without the need for washing steps. The hydrophilic, porous, and photoluminescence-quenching character of GONAP allows for the adsorption and quenching of photoluminescent quantum dots nanocrystals complexed with antibodies (Ab-QDs), enabling a ready-to-use immunosensing platform. The photoluminescence is recovered upon immunocomplex (antibody-antigen) formation which embraces a series of interactions (hydrogen bonding,
electrostatic, hydrophobic, and Van der Waals interactions) that trigger desorption of the antigen-Ab-QD complex from GONAP surface. However, the antigen is then attached onto the GONAP surface by electrostatic interactions leading to a spacer (greater than ≈20 nm) between Ab-QDs and GONAP and thus hindering nonradiative energy transfer. It is demonstrated that this simple—yet highly sensitive—platform represents a virtually universal immunosensing approach by using small-sized and big-sized targets as model analytes, those are, human-IgG protein and Escherichia coli bacteria. In addition, the assay is proved effective in real matrices analysis, including human serum, poultry meat, and river water. GONAP opens the way to conceptually new paper-based devices for immunosensing, which are amenable to point of care applications and automated
A wearable skin hydration sensor in the form of a capacitor is demonstrated based on skin impedance measurement. The capacitor consists of two interdigitated or parallel electrodes that are made of silver nanowires (AgNWs) in a polydimethylsiloxane (PDMS) matrix. The flexible and stretchable nature of the AgNW/PDMS electrode allows conformal contact to the skin. The hydration sensor is insensitive to the external humidity change and is calibrated against a commercial skin hydration system on an artificial skin over a wide hydration range. The hydration sensor is packaged into a flexible wristband, together with a network analyzer chip, a button cell battery, and an ultralow power microprocessor with Bluetooth. In addition, a chest patch consisting of a strain sensor, three electrocardiography electrodes, and a skin hydration sensor is developed for multimodal sensing. The wearable wristband and chest patch may be used for low-cost, wireless, and continuous monitoring of skin hydration and other health parameters.
A paper-based lateral flow immunoassay for pathogen detection that avoids the use of secondary antibodies and is revealed by the photoluminescence quenching ability of graphene oxide is reported. Escherichia coli has been selected as a model pathogen. The proposed device is able to display a highly specific and sensitive performance with a limit of detection of 10 CFU mL-1 in standard buffer and 100 CFU mL-1 in bottled water and milk. This low-cost disposable and easy-to-use device will prove valuable for portable and automated diagnostics applications.
Nanostructures are fabricated using either conventional or unconven-tional tools—that is, by techniques that are highly developed and widely used or by tech-niques that are relatively new and still being developed. This chapter reviews techniques of unconventional nanofabrication, and focuses on experimentally simple and inex-pensive approaches to pattern features with dimensions <100 nm. The techniques dis-cussed include soft lithography, scanning probe lithography, and edge lithography. The chapter includes recent advances in fabricating nanostructures using each set of tech-niques, together with demonstrated advantages, limitations, and applications for each.
In this work, gold-incorporated polyethylenedioxythiophene nanocomposite material has been synthesized chemically, employing
reverse emulsion polymerization method. Infrared and Raman spectroscopic studies revealed that the polymerization of ethylenedioxythiophene
leads to the formation of polymer polyethylenedioxythiophene incorporating gold nanoparticles. Scanning electron microscope
studies showed the formation of polymer nanorods of 50–100nm diameter and the X-ray diffraction analysis clearly indicates
the presence of gold nanoparticles of 50nm in size.
Monitoring the binding affinities and kinetics of protein interactions is important in clinical diagnostics and drug development because such information is used to identify new therapeutic candidates. Surface plasmon resonance is at present the standard method used for such analysis, but this is limited by low sensitivity and low-throughput analysis. Here, we show that silicon nanowire field-effect transistors can be used as biosensors to measure protein-ligand binding affinities and kinetics with sensitivities down to femtomolar concentrations. Based on this sensing mechanism, we develop an analytical model to calibrate the sensor response and quantify the molecular binding affinities of two representative protein-ligand binding pairs. The rate constant of the association and dissociation of the protein-ligand pair is determined by monitoring the reaction kinetics, demonstrating that silicon nanowire field-effect transistors can be readily used as high-throughput biosensors to quantify protein interactions.
One-dimensional organic nanostructures are essential building blocks for high performance gas sensors. Constucting as e-nose type sensor array is the current golden standard in develping portable system for gas mixtures detection. However, facile fabrication of nanoscale sensor array is still challenging due to the high cost of the conventional nanofabication techniques. In this work, we fabricate chemiresistive gas sensor array composed of well-ordered sub-100 nm wide conducting polymer nanowires using cost-effective nanoscale soft lithography. The poly (3,4-ethylene-dioxythiophene)-poly (styrene sulfonate) (PEDOT: PSS) nanowires functionalized by different self-assembled monolayers (SAMs) are capable of identifying volatile organic compounds (VOCs) at low concentrations range. The side chains and functional groups of the SAMs introduce different sensitivity and selectivity to the targeted analytes. The distinct response pattern of each chemical is subjected to pattern recognition protocols, which leads to a clear separation towards ten VOCs, including ketones, alcohols, alkanes, aromatics and amines. These results of the chemiresistive gas sensor array demonstrate that the nanoscale soft lithography is a reliable approach for fabricating nanosclae devices and have the potential of mass producibility.
The present study aimed to develop a highly sensitive label-free electrochemical aptasensor for the detection of Diazinon (DZN), as one of the most widespread organophosphorus compounds. The aptasensor was assembled using screen-printed gold electrode modified by thiolated aptamers which were immobilized on gold nanoparticles (Au NPs). Optimum deposition time, in which the highest electrochemical response occurred, was found in 150 s. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize electrochemical properties of the novel aptasensor. Electrochemical detection was carried out through differential pulse voltammetry in [Fe(CN)6]3-/4- solution. Fluctuation of the current was examined in the DZN concentration range of 0.1-1000 nM. According to the results, the designed aptasensor provided an extremely lower limit of detection (0.0169 nM) compared with HPLC and other colorimetric techniques for DZN detection. The present highly specific designed aptasensor doesn't interact with other analytes in the real sample. Consequently, the present aptasensor is easy to use and relatively inexpensive with a good sensitivity, stability, and reproducibility for this application. We are now evaluating all approaches to make a portable device for fast and sensitive quantification of DZN and related OPs.
The increased threat of antibiotic resistance has created an urgent need for new strategies. Herein, polyprodrug antimicrobials are proposed to mimic antimicrobial peptides appended with a concurrent drug release property, exhibiting broad‐spectrum antibacterial activity and especially high potency to inhibit methicillin‐resistant Staphylococcus aureus (MRSA) without inducing resistance. Two series of polyprodrug antimicrobials are fabricated by facile polymerization of triclosan prodrug monomer (TMA) and subsequent quaternization of hydrophilic poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA), affording PDMAEMA‐b‐PTMA and PQDMA‐b‐PTMA, respectively. Optimized samples with proper hydrophobic ratio are screened out, which exhibit remarkable bacterial inhibition and low hemolysis toward red blood cells. Furthermore, synergistic antibacterial mechanisms contribute to the bacteria killing, including serious membrane damage, increased out‐diffusion of cytosolic milieu across the membrane, and intracellular reductive milieu‐mediated triclosan release. No detectable resistance is observed for polyprodrug antimicrobials against MRSA, which is demonstrated to be better than commercial triclosan and vancomycin against in vivo MRSA‐infected burn models and a promising approach to the hurdle of antibiotic resistance in biomedicine.
Silver nanoparticles modified with poly(vinyl alcohol) (AgNP–PVA) were prepared by the reduction of silver ions with ascorbic acid. The concentrations of AgNPs, type of solvent and solvent ratio were optimized for the preparation of silver nano-ink to obtain a better conductive surface (low resistance). Different substrates such as glass, poly(vinyl chloride) (PVC) and poly(ethylene terephthalate) (PET) were tested and the sintering process was optimized for the preparation of an efficient electrode for electrochemical application. The screen-printed glass electrode fabricated with silver nano-ink showed low resistance and therefore was used as a working electrode in cyclic voltammetry (CV) determination of hydrogen peroxide (H2O2). A wide linear calibration range, 1.0 μM to 0.5 mM, was obtained for the determination of H2O2 with a limit of detection of 0.3 μM. The high recovery percentage (93.3–96.0%) has been obtained for the determination of H2O2 in a complex sample matrix (hospital and beauty parlor wastewater) and an interference study demonstrated the selectivity of the method. The screen-printed glass electrode is found to be simple, low cost and homemade compared to commercially available glass electrodes for monitoring H2O2 in environmental water samples.
Hydrogen sulfide, as the typical atmospheric pollutant, is neurotoxic and flammable even at a very low concentration. In this study, we design stable H<sub>2</sub>S sensors based on ZnO-carbon nanofibers. The nanofibers with 30.34 wt% carbon is prepared by a facial electrospinning route and following annealing treatment. The corresponding H<sub>2</sub>S sensors show excellent selectivity and response compared to pure ZnO nanofiber H<sub>2</sub>S sensors, particularly the response of 102 to 50 ppm H<sub>2</sub>S. Besides, they exhibit a nearly constant response of approximate 40 to 20 ppm H<sub>2</sub>S over 60 days. The superior performance of those H<sub>2</sub>S sensors can be attributed to protection of carbon which makes sure the high stability of ZnO, and oxygen vacancies to improve the response and selectivity to H<sub>2</sub>S. The good performance of ZnO-carbon H<sub>2</sub>S sensors suggests that the composites with oxygen vacancies prepared by a facial electrospinning route may provide a new research strategy in field of gas sensors, photocatalysts and semiconductor devices.
A sandwich-type nanostructured immunosensor based on carboxylated multi-walled carbon nanotube (CMWCNT)-embedded whiskered nanofibres (WNFs) was developed for detection of cardiac Troponin I (cTnI). WNFs were directly fabricated on glassy carbon electrodes (GCE) by removing the sacrificial component (polyethylene glycol, PEG) after electrospinning of polystyrene/CMWCNT/PEG nanocomposite nanofibres, and utilised as a transducer layer for enzyme-labelled amperometric immunoassay of cTnI. The whiskered segments of CMWCNTs were activated and utilised to immobilise anti-cTnT antibodies. It was observed that the anchored CMWCNTs within the nanofibres were suitably stabilised with excellent electrochemical repeatability. A sandwich-type immuno-complex was formed between cTnI and horseradish peroxidase-conjugated anti-cTnI (HRP-anti-cTnI). The amperometric responses of the immunosensor were studied using cyclic voltammetry (CV) through an enzymatic reaction between hydrogen peroxide and HRP conjugated to the secondary antibody. The nanostructured immunosensor delivered a wide detection range for cTnI from the clinical borderline for a normal person (0.5-2 ng mL-1) to the concentration present in myocardial infarction patients ( >20 ng mL-1), with a detection limit of ~0.04 ng mL-1. It also showed good reproducibility and repeatability for three different cTnI concentration (1, 10 and 25 ng mL-1) with satisfactory relative standard deviations (RSD). Hence, the proposed nanostructured immunosensor shows potential for point-of-care testing.
An electrochemical biosensor was developed based on a steric hindrance hybridization assay to allow the highly sensitive detection of streptavidin. In the steric hindrance hybridization assay, the signaling strand DNA (sig-DNA) was labeled at the 3' end with CdSe quantum dots (QDs) and at the 5' end with biotin, and capturing strand DNA (the complementary strand of sig-DNA) was labeled at the 5' end with thiol. The steric hindrance effect generated by streptavidin which was bound with the signaling DNA strand. The streptavidin limited the ability of the sig-DNA to hybridize with the cap-DNA, which were linked on the surface of a gold electrode. Therefore, the concentration of streptavidin was detected indirectly based on the concentration of CdSe QDs on the electrode surface. The concentration of CdSe QDs on the electrode surface was detected by differential pulse anodic stripping voltammetry. Under optimal conditions, the streptavidin detection range using the as-prepared biosensor was 1.96pg/mL to 1.96µg/mL and the detection limit was 0.65pg/mL. The experimental results showed that the electrochemical biosensor could detect streptavidin rapidly and accurately.
Principles of Bacterial Detection: Biosensors, Recognition Receptors and Microsystems presents a significant and up-to-date review of various integrated approaches for bacterial detection. Distinguished engineers and scientists from key institutions worldwide have contributed chapters that provide a deep analysis of their particular subject; at the same time, each topic is framed within the context of this integrated approach. This work is a comprehensive approach to bacterial detection requiring a thorough knowledge of the subject and an effective integration of other disciplines in order to appropriately convey the state-of-the-art fundamentals and applications of the involved disciplines.
The book consists of four parts:
The first part provides an introduction to pathogenic bacteria and sampling techniques and an overview of the rapid microbiological methods.
The second part describes the different transducers used for the detection of bacteria. It covers the theory behind each technique and provides a state-of-the-art review of all the new technologies used for the detection of bacteria in detail. Strategies and future prospects are suggested at the end of each chapter for developing future technologies to achieve a better sensitivity and swifter detection of bacteria.
The third part gives an account of the different recognition receptors used in the various methods for the detection of bacteria. It describes in detail the use of immunoassays, nucleic acids, oligonucleotide microarrays, carbohydrates, aptamers, protein microarrays, bacteriophages, phage displays and molecular imprinted polymers as recognition elements.
The fourth part covers the microsystems used for detection/identification and bacterial manipulation such as bacteria lysis and PCR in microfluidics, dielectrophoresis, ultrasonic manipulation techniques and mass spectrometry techniques.
Students and researchers who need a solid foundation or reference and practitioners interested in discovering more about the state-of-the-art methods of bacterial detection will find this book invaluable. This book is directed at academics and undergraduate and postgraduate students who work in areas related to bacterial detection. It may also serve as an important reference for professionals working in different fields, including biomedical science, physical science, microsystems engineering, nanotechnology, veterinary science, food quality assurance, bioterrorism and security as well as health surveillance.
Cellulose, the impressive potential sustainable fuels, is difficult to hydrolyze because of the protection of the β-1,4-glycosidic bonds by the tight hydrogen bonding network. In this work, homogenous graphene oxide (GO)-peptide nanofiber hybrid hydrogel (GO-PNFs) was designed as β-glycosyl hydrolase mimetic for realizing the efficient degradation of cellobiose and cellopentose. For comparison, free peptides, graphene oxide mixed with free peptides (GO-Peptdies) and self-assembled peptide nanofibers (PNFs) were also studied for their activity as hydrolase mimetic for degradation of cellobiose. Among these materials, the GO-PNFs showed the highest hydrolysis activity. Transmission electron microscopy, Atomic force microscopy, Fluorescence analysis, Circular dichroism spectroscopies, X-ray diffraction, Raman spectra and Computational modeling were used to interprete the difference of mechanism of activity in these designed artificial enzymes. These investigation suggested that the high catalytic performance of GO-PNFs toward cellobiose and cellopentose hydrolysis could be attributed to the formation of nanofiber structures of peptides, optimal molecular conformation and less steric hindrance to access the substrate. More importantly, GO not only served as a platform for attaching PNFs, but also created a hydrophobic microenvironment and facilitated the proton transfer process, which is an essential step in the catalytic hydrolysis, thus enhaning the catalytic activity. All these provided insights into the potential use of peptide and GO hybrid composite nanoenzyme in efficient cellulose hydrolysis.
A Cu nanowire array seamlessly grown on Cu wire was prepared by electrochemical reduction of copper oxide nanowires grown by thermal oxidation. The morphology and structure of the nanostructured Cu wires were characterized via scanning electron microscope, transmission electron microscopy and X-ray diffraction spectroscopy. The seamless surface nanostructure offered a large surface area and improved conductivity. Electrochemical measurements demonstrated that the seamless nanowires structure could electrochemically reduce nitrate due to the improved conductivity between the active sites and the substrate. A linear response to nitrate ions over a concentration range from 50 μM to 600 μM (R² = 0.9974) with a high sensitivity of 0.357 μA μM⁻¹ cm⁻¹ and low detection limit of 12.2 μM at a signal-to-noise ratio of 3, respectively, were obtained on the nanostructured copper wire. The influences of structure on electrochemical performance which are significant for the design of electrochemical sensor are discussed.
Here we prepared an electrochemical immunosensor employing Au sheet as working electrode, Fe3O4 magnetic nanoparticles (MNPs) as supporting matrix and hemin/G-quadruplex DNAzyme as signal amplifier for determination of hepatitis B virus surface antigen (HBsAg). First, the primary antibody of HBs (Ab1) was immobilized on the surface of the carboxyl-modified MNPs. Then, the assembly of antibody and alkylthiol/G-quadruplex DNA/hemin on gold nanoparticles was used as bio-bar-coded nanoparticle probe. Protein target was sandwiched between the primary antibody of HBs (Ab1) immobilized on the MNPs and hemin bio-bar-coded AuNPs probe labeled antibody (Ab2). Hemin/G-quadruplex structure as HRP mimicking-DNAzyme significantly improved the catalytic reduction of H2O2 by oxidation of methylene blue (MB). Square wave voltammetry signals of MB provided quantitative measurements of HBsAg with a linear concentration range of 0.3–1000 pgmL⁻¹ and detection limit of 0.19 pgmL⁻¹. Due to efficient catalytic activity of HRP mimicking-DNAzyme, the proposed immunosensor exhibited high sensitivity and it holds great promise for clinical application and provides a new platform for immunosensor development and fast disease diagnosis.
This paper reports a surface functionalization strategy for protein detections based on biotin-derivatized poly(L-lysine)-grafted oligo-ethylene glycol (PLL-g-OEGx-Biotin) copolymers. Such strategy can be used to attach the biomolecule receptors in a reproducible way simply by incubation of the transducer element in a solution containing such copolymers which largely facilitated the sensor functionalization at an industrial scale. As the synthesized copolymers are cationic in physiology pH, surface biotinylation can be easily achieved via electrostatic adsorption on negatively charged sensor surface. Biotinylated receptors can be subsequently attached through well-defined biotin-streptavidin interaction. In this work, the bioactive sensor surfaces were applied for mouse IgG and prostate specific antigen (PSA) detections using quartz crystal microbalance (QCM), optical sensor (BioLayer Interferometry) and conventional ELISA test (colorimetry). A limit of detection (LOD) of 0.5 nM was achieved for PSA detections both in HEPES buffer and serum dilutions in ELISA tests. The synthesized PLL-g-OEGx-Biotin copolymers with different OEG chain length were also compared for their biosensing performance. Moreover, the surface regeneration was achieved by pH stimulation to remove the copolymers and the bonded analytes, while maintaining the sensor reusability as well. Thus, the developed PLL-g-OEGx-Biotin surface assembling strategy is believed to be a versatile surface coating method for protein detections with multi-sensor compatibility.
The use of biosensors in point-of-care (POC) testing devices has attracted considerable attention in the past few years, mainly because of their high specificity, portability, and relatively low cost. Coupling these devices with miniaturized electrochemical transducers has shown great potential toward simple, rapid, and cost-effective analysis that can be performed in the field, especially for healthcare, environmental monitoring, and food quality control. For this reason, the number of publications in this field has grown exponentially over the past decade, making it a trending topic in current research. Although great improvement has been achieved in the field of electrochemical biosensing, there are still some challenges to overcome, especially concerning the improvement of sensing materials and miniaturization. In this Review, we summarize some of the most recent advances achieved in POC electrochemical biosensor applications, focusing on new materials and modifiers for biorecognition developed to improve sensitivity, specificity, stability, and response time.
Self-assembled nanowire (NW) crystals can be grown into nearly defect-free nanomechanical resonators with exceptional properties, including small motional mass, high resonant frequency, and low dissipation. Furthermore, by virtue of slight asymmetries in geometry, a NW's flexural modes are split into doublets oscillating along orthogonal axes. These characteristics make bottom-up grown NWs extremely sensitive vectorial force sensors. Here, taking advantage of its adaptability as a scanning probe, we use a single NW to image a sample surface. By monitoring the frequency shift and direction of oscillation of both modes as we scan above the surface, we construct a map of all spatial tip-sample force derivatives in the plane. Finally, we use the NW to image electric force fields distinguishing between forces arising from the NW charge and polarizability. This universally applicable technique enables a form of atomic force microscopy particularly suited to mapping the size and direction of weak tip-sample forces.
Development of high-performance p-type semiconductor based gas sensors exhibiting fast-response/recovery times with ultra-high response are of major importance for gas sensing applications. Recent reports demonstrated the excellent properties of p-type semiconducting oxide for various practical applications, especially for selective oxidation of volatile organic compounds (VOCs). In this work, sensors based on CuO nanowire (NW) networks have been successfully fabricated via a simple thermal oxidation process on pre-patterned Au/Cr pads. Our investigation demonstrates high impact of the process temperature on aspect ratio and density of copper oxide NWs. An optimal temperature for growth of thin and densely packed NWs was found to be at 425 °C. The fabricated sensors demonstrated ultra-high gas response by a factor of 313 to ethanol vapour (100 ppm) at an operating temperature of 250 °C. High stability and repeatability of these sensors indicate the efficiency of p-type oxide based gas sensors for selective detection of VOCs. A high-performance nanodevice was fabricated in a FIB-SEM system using a single CuO NW, demonstrating an ethanol response of 202 and rapid response and recovery of ~198 ms at room temperature. The involved gas sensing mechanism of CuO NW networks has been described. We consider that the presented results will be of a great interest for the development of higher-performance p-type semiconductor based sensors and bottom-up nanotechnologies.
A new surface functionalization scheme for nano-Bio field effect transistors (FETs) using biocompatible polyelectrolyte thin films (PET) is developed. PET assemblies on Si nanowires (Si-NWs) are driven by electrostatic interactions between the positively charged polymer backbone and negatively charged Si/SiO2 surface. Such assemblies can be directly coated from PET aqueous solutions and result in a uniform nanoscale thin film, which is more stable compared to the conventional amine silanization. Short oligo-ethylene glycol chains are grafted on the PETs to prevent nonspecific protein binding. Moreover, the reactive groups of the polymer chains can be further functionalized to other chemical groups in specific stoichiometry for biomolecules detection. Therefore, it opens a new strategy to precisely control the functional group densities on various biosensor surfaces at the molecular level. In addition, such assemblies of the polymers together with the bound analytes can be removed with the pH stimulation resulting in regeneration of a bare sensor surface without compromising the integrity and performance of the Si-NWs. Thus, it is believed that the developed PET coating and sensing systems on Si-NW FETs represent a versatile, promising approach for regenerative biosensors which can be applied to other biosensors and will benefit real device applications, enhancing sensor lifetime, reliability, and repeatability.
We report here the use of nanomolding in capillaries (NAMIC) coupled with dithiocarbamate (DTC) chemistry to fabricate sub-50 nm quasi-1D arrays of 3.5 nm core gold nanoparticles (Au NPs) over large areas. Owing to chemical immobilization via the DTC bond, the patterned NP systems are stable in water and organic solvents, thus allowing the surface modification of the patterned Au NP arrays through thiol chemistry and further orthogonal binding of proteins. The electrical properties of these patterned Au NP wires have also been studied. Our results show that NAMIC combined with surface chemistry is a simple but powerful tool to create metal NP arrays that can potentially be applied to fabricate nanoelectronic or biosensing devices.
Nanowires are important potential candidates for the realization of the next generation of sensors. They offer many advantages such as high surface-to-volume ratios, Debye lengths comparable to the target molecule, minimum power consumption, and they can be relatively easily incorporated into microelectronic devices. Accordingly, there has been an intensified search for novel nanowire materials and corresponding platforms for realizing single-molecule detection with superior sensing performance. In this work, progress made towards the use of nanowires for achieving better sensing performance is critically reviewed. In particular, various nanowires types (metallic, semiconducting, and insulating) and their employment either as a sensor material or as a template material are discussed. Major obstacles and future steps towards the ultimate nanosensors based on nanowires are addressed.
We have developed a simple assay method for the evaluation of estrogen receptor (ER) binding capacity of chemicals without the use of radio- or fluorescence-labeled compounds. We used the solution competition assay by the BIACORE biosensor, a surface plasmon resonance biosensor, with estradiol as a ligand, human recombinant ER(alpha) (hrER(alpha)) as a high molecular weight (hmw) interactant and test chemicals as analytes. For the ligand, aminated estradiol with a spacer molecule (E2-17PeNH) was synthesized and immobilized on a carboxymethyl dextran-coated sensor chip by the amine coupling method. The injection of the hmw interactant hrER(alpha) to the biosensor raised the sensorgram, indicating its binding to the ligand E2-17PeNH. The binding of test chemicals to hrERalpha was determined as a reduction in the hrER(alpha) binding to E2-17PeNH. The dissociation constant for the binding to hrER(alpha) was calculated for estrone (4.29 x 10(-9)M), estradiol (4.04 x 10(-10)M), estriol (8.35 x 10(-10)M), tamoxifen (2.16 x 10(-8)M), diethylstilbestrol (1.46 x 10(-10)M), bisphenol A (1.35 x 10(-6)M) and 4-nonylphenol (7.49 x 10(-6)M), by plotting the data according to an equation based on mass action law. This method can also be used as a high throughput screening method.
Avidin-poly(ethylene glycol) (PEG) conjugates were obtained by derivatization of about 10% of the protein amino groups (four amino groups per protein molecule) with linear 5 kDa PEG or branched 10 or 20 kDa PEGs. Circular dichroism analysis showed that the polymer conjugation neither altered the protein structure nor the environment of the aromatic amino acids which are present at the level of the biotin binding site. Spectroscopic studies were carried out to evaluate the biotin recognition activity of the conjugates either in terms of number of biotin binding sites or avidin/biotin affinity. Avidin-PEG 5 kDa and avidin-PEG 10 kDa displayed over 90% of the native protein biological activity while a reduction in the recognition of biotinylated antibodies of about 25% was found with PEG 20 kDa. In vivo studies demonstrated that the protein immunogenicity was in the order: wild type avidin>avidin-PEG 5 kDa>avidin-PEG 10 kDa>avidin-PEG 20 kDa. By intravenous injection into mice bearing a solid tumor, all conjugates displayed prolonged permanence in the circulation with respect to the native protein. The area under the curve values of avidin-PEG 5 kDa, avidin-PEG 10 kDa and avidin-PEG 20 kDa were about 3-, 7- and 30-times higher than the wild type avidin with reduced accumulation in kidneys and liver. Interestingly, all conjugates accumulated significantly in the tumor mass. In particular, in the case of avidin-PEG 20 kDa, 8% of the injected dose (ID)/g of tissue accumulated in the tumor after 5 h from the administration and over 6% of the ID/g was maintained throughout 72 h.
In order to establish ELISA (enzyme-linked immunosorbent assay) method to detect Total E. coli in water environment, E. coli multi-characters antigens in water environment were prepared according to the characters of kinds of E. coli serotypes, including antigen of whole cell, antigen of disrupted whole cell, somatic antigen, flagellar antigen and fimbrial antigen. Total E. coli polyclonal antibodies were obtained from the New Zealand rabbits immunized with these five antigens, respectively. Antibodies generated in this research are with high titers and good purity, can conjugate with antigens, specifically, stably and strongly. Indirect ELISA shows the titers of antibody of whole cell and antibody of disrupted whole cell are both over 1x10(5). The cross-reactivity of the antibody is from 12 to 30% which indicate the specificity of the antibody against Total E. coli. Based on these antibodies, we established indirect ELISA method to detect Total E. coli in water environment. The matrix effects were studied and the results show that there is no significant influence by all the factors. The ELISA result shows that the detection limitation could be 10(4) CFU (colony forming units) L(-1). The indirect ELISA method developed in this study is well suited for Total E. coli analysis in real water samples as a rapid screen method.