No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Rapid Purification and Enrichment of Viral Particles Using Self-Propelled Micromotors
Abstract
Virus infections remain one of the principal causes of morbidity and mortality worldwide. The current gold standard approach for diagnosing pathogens requires access to reverse transcription-polymerase chain reaction (RT-PCR) technology. However, separation and enrichment of the targets from complex and diluted samples remains a major challenge. In this work, we proposed a micromotor-based sample preparation concept for the efficient separation and concentration of target viral particles before PCR. The micromotors are functionalized with antibodies with a 3D polymer linker and are capable of self-propulsion by the catalytic generation of oxygen bubbles for selective and positive virus enrichment. This strategy significantly improves the enrichment efficiency and recovery rate of virus (up to 80% at 104 tu mL-1 in a 1 mL volume within just 6 min) without external mixing equipment. The method allows the Ct value in regular PCR tests to appear 6-7 cycles earlier and a detection limit of 1 tu mL-1 for the target virus from swap samples. A point-of-need test kit is designed based on the micromotors which can be readily applied to pretreat a large volume of samples.
ResearchGate has not been able to resolve any citations for this publication.
“On‐the‐fly” molecule enrichment by micro/nanomotors obviously improves heterogeneous catalysis, trace detection, and environmental monitoring, yet faces challenges of the trade‐off between collection range and interaction time. Inspired by the versatile foraging process of predators, this work demonstrates that micromotors doing spontaneous multipattern motion with microvortex can greatly enhance “on‐the‐fly” enrichment, demonstrated by highly sensitive surface‐enhanced Raman scattering detection. It leverages an axis‐asymmetric bowl‐shaped structure and the nonlinear Ag–AgCl reaction, realizing alternating low‐velocity swinging forward and accelerated steering motions for prolonged interaction and large work area. Moreover, the bowl‐shaped microstructure bestows a micro‐vortex above the Ag side due to the competition of electric potential and pressure gradient, also extending interaction time during the acceleration. Consequently, it exhibits at least an order of magnitude larger enhancement of detection signals than the counterparts. This proof‐of‐concept study highlights the significance of motion mode and structure design in guiding flow field, offering substantial benefits for applications.
Bovine mastitis produced by Staphylococcus aureus (S. aureus) causes major problems in milk production due to the staphylococcal enterotoxins produced by this bacterium. These enterotoxins are stable and cannot be eradicated easily by common hygienic procedures once they are formed in dairy products. Here, magnetic microrobots (MagRobots) are developed based on paramagnetic hybrid microstructures loaded with IgG from rabbit serum that can bind and isolate S. aureus from milk in a concentration of 3.42 10⁴ CFU g⁻¹ (allowable minimum level established by the United States Food and Drug Administration, FDA). Protein A, which is present on the cell wall of S. aureus, selectively binds IgG from rabbit serum and loads the bacteria onto the surface of the MagRobots. The selective isolation of S. aureus is confirmed using a mixed suspension of S. aureus and Escherichia coli (E. coli). Moreover, this fuel‐free system based on magnetic robots does not affect the natural milk microbiota or add any toxic compound resulting from fuel catalysis. This system can be used to isolate and transport efficiently S. aureus and discriminate it from nontarget bacteria for subsequent identification. Finally, this system can be scaled up for industrial use in food production.
Herein, a general procedure for the synthesis of multifunctional MRs, which simultaneously exhibit i) chiral, ii) magnetic, and iii) fluorescent properties in combination with iv) self‐propulsion, is reported. Self‐propelled Ni@Pt superparamagnetic microrockets have been functionalized with fluorescent CdS quantum dots carrying a chiral host biomolecule as β‐cyclodextrin (β‐CD). The “on‐the‐fly” chiral recognition potential of MRs has been interrogated by taking advantage of the β‐CD affinity to supramolecularly accommodate different chiral biomolecules (i.e., amino acids). As a proof‐of‐concept, tryptophan enantiomers have been discriminated with a dual‐mode (optical and electrochemical) readout. This approach paves the way to devise intelligent cargo micromachines with “built‐in” chiral supramolecular recognition capabilities to elucidate the concept of “enantiorecognition‐on‐the‐fly”, which might be facilely customized by tailoring the supramolecular host–guest encapsulation.
Rapid and accurate diagnosis of COVID-19 plays an essential role in the current epidemic prevention and control. Despite the promise of nucleic acid and antibody tests, there is still a great challenge to reduce the misdiagnosis, especially for asymptomatic individuals. Here we report a generalizable method for highly specific and ultrasensitive detection of serum COVID-19-associated antigens based on an aptamer-assisted proximity ligation assay. The sensor is based on binding two aptamer probes to the same protein target that brings the ligation DNA region into close proximity, thereby initiating ligation-dependent qPCR amplification. Using this system, serum nucleocapsid protein has been detected quantitatively by converting protein recognition into a detectable qPCR signal using a simple, homogeneous and fast detection workflow in ∼2 hours. In addition, this system has also been transformed into a universal platform for measuring specific interactions between spike S1 and its receptor ACE2, and more importantly demonstrated the feasibility for screening and investigation of potential neutralizing aptamers. Since in vitro selection can obtain aptamers selective for many COVID-19-associated antigens, the method demonstrated here will serve as an important tool for the diagnosis and therapeutics of COVID-19.
A large-scale diagnosis of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) is essential to downregulate its spread within as well as across communities and mitigate the current outbreak of the pandemic novel coronavirus disease 2019 (COVID-19). Herein, we report the development of a rapid (less than 5 min), low-cost, easy-to-implement, and quantitative paper-based electrochemical sensor chip to enable the digital detection of SARS-CoV-2 genetic material. The biosensor uses gold nanoparticles (AuNPs), capped with highly specific antisense oligonucleotides (ssDNA) targeting viral nucleocapsid phosphoprotein (N-gene). The sensing probes are immobilized on a paper-based electrochemical platform to yield a nucleic-acid-testing device with a readout that can be recorded with a simple hand-held reader. The biosensor chip has been tested using samples collected from Vero cells infected with SARS-CoV-2 virus and clinical samples. The sensor provides a significant improvement in output signal only in the presence of its target—SARS-CoV-2 RNA—within less than 5 min of incubation time, with a sensitivity of 231 (copies μL–1)⁻¹ and limit of detection of 6.9 copies/μL without the need for any further amplification. The sensor chip performance has been tested using clinical samples from 22 COVID-19 positive patients and 26 healthy asymptomatic subjects confirmed using the FDA-approved RT-PCR COVID-19 diagnostic kit. The sensor successfully distinguishes the positive COVID-19 samples from the negative ones with almost 100% accuracy, sensitivity, and specificity and exhibits an insignificant change in output signal for the samples lacking a SARS-CoV-2 viral target segment (e.g., SARS-CoV, MERS-CoV, or negative COVID-19 samples collected from healthy subjects). The feasibility of the sensor even during the genomic mutation of the virus is also ensured from the design of the ssDNA-conjugated AuNPs that simultaneously target two separate regions of the same SARS-CoV-2 N-gene.
Detection of SARS-CoV-2 using RT–PCR and other advanced methods can achieve high accuracy. However, their application is limited in countries that lack sufficient resources to handle large-scale testing during the COVID-19 pandemic. Here, we describe a method to detect SARS-CoV-2 in nasal swabs using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and machine learning analysis. This approach uses equipment and expertise commonly found in clinical laboratories in developing countries. We obtained mass spectra from a total of 362 samples (211 SARS-CoV-2-positive and 151 negative by RT–PCR) without prior sample preparation from three different laboratories. We tested two feature selection methods and six machine learning approaches to identify the top performing analysis approaches and determine the accuracy of SARS-CoV-2 detection. The support vector machine model provided the highest accuracy (93.9%), with 7% false positives and 5% false negatives. Our results suggest that MALDI-MS and machine learning analysis can be used to reliably detect SARS-CoV-2 in nasal swab samples. SARS-CoV-2 is reliably detected in nasal swab samples using mass spectrometry and machine learning analysis.
The current outbreak of the pandemic coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) demands its rapid, convenient, and large-scale diagnosis to downregulate its spread within as well as across the communities. But the reliability, reproducibility, and selectivity of majority of such diagnostic tests fail when they are tested either to a viral load at its early representation or to a viral gene mutated during its current spread. In this regard, a selective ‘naked-eye’ detection of SARS-CoV-2 is highly desirable, which can be tested without accessing any advanced instrumental techniques. We herein report the development of a colorimetric assay based on gold nanoparticles (AuNPs), those when capped with suitably designed thiol modified antisense oligonucleotides (ASOs) specific for N-gene (nucleocapsid phosphoprotein) of SARS-CoV-2, could be used for diagnosing positive COVID-19 cases within 10 minutes from the isolated RNA samples. The thiol modified ASO capped AuNPs agglomerate selectively in the presence of its target RNA sequence of SARS-CoV-2 and demonstrate a change in its surface plasmon resonance (SPR). Further, the addition of RNaseH cleaves the RNA strand from the RNA-DNA hybrid leading to a visually detectable precipitate from the solution mediated by the additional agglomeration among the AuNPs. The selectivity of the assay has been monitored in presence of MERS-CoV viral RNA with a limit of detection of 0.18 ng/µL of RNA having SARS-CoV-2 viral load. Thus, the current study reports a selective, and visual ‘naked-eye’ detection of COVID-19 causative virus, SARS-CoV-2, without the requirement of any sophisticated instrumental techniques.
Coronavirus disease 2019 (COVID-19) is a newly emerging human infectious disease caused by acute respiratory syndrome coronavirus 2 (SARS-CoV-2, previously called 2019-nCoV). Based on the rapid increase in the rate of human infection, the World Health Organization (WHO) has classified the COVID-19 outbreak as a pandemic. Because no specific drugs or vaccines for COVID-19 are yet available, early diagnosis and management are crucial for containing the outbreak. Here, we report a field-effect transistor (FET)-based biosensing device for detecting SARS-CoV-2 in clinical samples. The sensor was produced by coating graphene sheets of FET with a specific antibody against SARS-CoV-2 spike protein. The performance of the sensor was determined using antigen protein, cultured virus, and nasopharyngeal swab specimens from COVID-19 patients. Our FET device could detect SARS-CoV-2 spike protein at concentrations of 1 fg/ml in PBS and 100 fg/ml clinical transport medium. In addition, the FET sensor successfully detected SARS-CoV-2 in culture medium (limit of detection [LOD]: 1.6 x 10¹ pfu/ml) and clinical samples (LOD: 2.42 x 10² copies/ml). Thus, we have successfully fabricated a promising FET biosensor for SARS-CoV-2; our device is a highly sensitive immunological diagnostic method for COVID-19 that requires no sample pretreatment or labeling.
Extraction of nucleic acids in microsystems is of significance for biomedical applications, but the current extraction methods generally require sophisticated microchannels and external equipment, hindering their practical applications. In this work, we have demonstrated a simple, versatile and efficient approach to extract nucleic acids in microsystems by developing cationic branched polyethyleneimine (PEI)‐functionalized tubular micromotors. The as‐developed tubular micromotors are fabricated by a two‐step process combining the template‐assisted electrodeposition and carbodiimide chemistry, and contain an inner catalytic Pt layer, a middle magnetic Ni layer and an outer cationic PEI layer. They exhibit autonomous bubble‐propelled motion in aqueous hydrogen peroxide solutions, which can be guided by an external magnetic field, and the surface charges can be reversibly modulated by changing the pH value of the solution. Consequently, the as‐developed tubular micromotors can selectively absorb nucleic acids from acidic solutions and desorb them into alkaline solutions, leading to the extraction of nucleic acids with high efficiency without external stirring. Furthermore, they can be operated in a microchannel chip without the aid of a pumping system. Our results indicate that this PEI‐functionalized tubular micromotor platform provides a novel, simple and versatile microsystem nucleic acid extraction technology, holding considerable promise for important practical applications.
In this research magnetite was synthesized by coprecipitation method, in which solution of NH4OH was added into the solution containing a mixture of Fe2+/Fe3+ (molar ratio 1:2) until pH 11 under strong ultrasonic agitation for 30 min. The black sediment of magnetite was filtered, washed and dried. The product was then modified by using oleic acid to prevent agglomeration. Chitosan was prepared by deacetilization of chitin, whereas chitin was extracted from shrimp shell. In the synthesis of nanocomposite, 0.5 g of chitosan and 1.5 g of oleic acid modified magnetite were introduced into 100 mL of 2% acetic acid solution, followed by sonication treatment for 10 min and magnetic stirring for 20 min. In order to perform the cross-linkage reaction, solution of 2% glutaraldehyde was added into the mixture at temperature of 40 °C for 3 h. The composite was collected by magnetic separation, followed by washing with distilled water and ethanol in a row. The product was dried and characterized by XRD, FTIR, TEM and VSM methods. The result showed that the composite had good crystal structure with a cubic inverse spinel structure, monodisperse and quasi sphere in shape with diameter of 20–25 nm. It had high saturation magnetization (43.4 emu/g) and superparamagnetic property.
A perspective review of recent strategies involving the use of nano/micro-vehicles to address key challenges associated with delivery and (bio)sensing at the cellular level is presented. The main types and characteristics of the different nano/micro-vehicles used for these cellular applications are discussed, including fabrication pathways, propulsion (catalytic, magnetic, acoustic or biological) and navigation strategies, and relevant parameters affecting their propulsion performance and sensing and delivery capabilities. Thereafter, selected applications are critically discussed. Emphasis is made on enhancing extra- and intra-cellular-biosensing capabilities, fast cell internalization, rapid inter- or intra-cellular movement, efficient payload delivery, and targeted on-demand controlled release towards greatly improved monitoring and modulation of cellular processes. The critical discussion of selected breakthrough applications illustrates how these smart multifunctional nano/microdevices operate as nano/micro-carriers and sensors at the intra- and extra cellular level. These advances allow both real-time biosensing of relevant targets and processes even at single cell level, and the delivery of different cargoes (drugs, functional proteins, oligonucleotides and cells) for therapeutics, gene silencing/transfection, and assisted fertilization, while overcoming challenges faced by current affinity biosensors and delivery vehicles. Key future challenges, envisioned opportunities and future perspectives of this remarkably exciting field are discussed.
For natural microswimmers, the interplay of swimming activity and external flow can promote robust motion, e.g. propulsion against ("upstream rheotaxis") or perpendicular to the direction of flow. These effects are generally attributed to their complex body shapes and flagellar beat patterns. Here, using catalytic Janus particles as a model experimental system, we report on a strong directional response that occurs for spherical active particles in a channel flow. The particles align their propulsion axes to be nearly perpendicular to both the direction of flow and the normal vector of a nearby bounding surface. We develop a deterministic theoretical model of spherical microswimmers near a planar wall that captures the experimental observations. We show how the directional response emerges from the interplay of shear flow and near-surface swimming activity. Finally, adding the effect of thermal noise, we obtain probability distributions for the swimmer orientation that semi-quantitatively agree with the experimental distributions.
Viral diseases are perpetual threats to human and animal health. Detection and characterization of viral pathogens require accurate, sensitive, and rapid diagnostic assays. For field and clinical samples, the sample preparation procedures limit the ultimate performance and utility of the overall virus diagnostic protocols. This study presents the development of a microfluidic device embedded with porous silicon nanowire (pSiNW) forest for label‐free size‐based point‐of‐care virus capture in a continuous curved flow design. The pSiNW forests with specific interwire spacing are synthesized in situ on both bottom and sidewalls of the microchannels in a batch process. With the enhancement effect of Dean flow, this study demonstrates that about 50% H5N2 avian influenza viruses are physically trapped without device clogging. A unique feature of the device is that captured viruses can be released by inducing self‐degradation of the pSiNWs in physiological aqueous environment. About 60% of captured viruses can be released within 24 h for virus culture, subsequent molecular diagnosis, and other virus characterization and analyses. This device performs viable, unbiased, and label‐free virus isolation and release. It has great potentials for virus discovery, virus isolation and culture, functional studies of virus pathogenicity, transmission, drug screening, and vaccine development.
Viral infectious diseases can erupt unpredictably, spread rapidly, and ravage mass populations. Although established methods, such as polymerase chain reaction, virus isolation, and next-generation sequencing have been used to detect viruses, field samples with low virus count pose major challenges in virus surveillance and discovery. We report a unique carbon nanotube size-tunable enrichment microdevice (CNT-STEM) that efficiently enriches and concentrates viruses collected from field samples. The channel sidewall in the microdevice was made by growing arrays of vertically aligned nitrogen-doped multiwalled CNTs, where the intertubular distance between CNTs could be engineered in the range of 17 to 325 nm to accurately match the size of different viruses. The CNT-STEM significantly improves detection limits and virus isolation rates by at least 100 times. Using this device, we successfully identified an emerging avian influenza virus strain [A/duck/PA/02099/2012(H11N9)] and a novel virus strain (IBDV/turkey/PA/00924/14). Our unique method demonstrates the early detection of emerging viruses and the discovery of new viruses directly from field samples, thus creating a universal platform for effectively remediating viral infectious diseases.
Towards addressing the need for detecting and eliminating biothreats, we describe a micromotor-based approach for screening, capturing, isolating and destroying anthrax simulant spores in a simple and rapid manner with minimal sample processing. The B. globilli antibody-functionalized micromotors can recognize, capture and transport B. globigii spores in environmental matrices, while showing non-interactions with excess of non-target bacteria. Efficient destruction of the anthrax simulant spores is demonstrated via the micromotor-induced mixing of a mild oxidizing solution. The new micromotor-based approach paves a way to dynamic multifunctional systems that rapidly recognize, isolate, capture and destroy biological threats.
Providing information about single virus particles has for a long time been mainly the domain of electron microscopy. More recently, technologies have been developed-or adapted from other fields, such as nanotechnology-to allow for the real-time quantification of physical virion particles, while supplying additional information such as particle diameter concomitantly. These technologies have progressed to the stage of commercialization increasing the speed of viral titer measurements from hours to minutes, thus providing a significant advantage for many aspects of virology research and biotechnology applications. Additional advantages lie in the broad spectrum of virus species that may be measured and the possibility to determine the ratio of infectious to total particles. A series of disadvantages remain associated with these technologies, such as a low specificity for viral particles. In this review we will discuss these technologies by comparing four systems for real-time single virus particle analysis and quantification.
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.
Influenza A virus (IAV) possesses a high infectivity and pathogenicity, and can lead to severe respiratory infection with similar symptoms caused by some other common respiratory viruses. Lateral flow assay (LFA) has been widely deployed in remote settings as a rapid and reliable approach for point-of-care detection of infectious pathogens. However, it still remains challenging to detect IAV virions using LFA from clinical samples such as nasopharyngeal or throat swabs, because their various components and high viscosity can decrease flow velocity and lead to the nonspecific adsorption of nanoparticle labels on the sensing membrane. Herein, we demonstrated a magnetic quantum dot nanobeads (MQBs) based LFA for magnetic enrichment and fluorescent detection of IAV virions in clinical specimens. In this study, MQBs were synthesized and then conjugated with IAV-specific antibody to efficiently enrich IAV virions from complex biological matrix, but also serve as highly bright fluorescent probes in lateral flow strips. This assay can achieve quantitative detection of IAV virions with a low limit of detection down to 22 pfu mL–1 within 35 minutes, and show good specificity between influenza B virus and two adenovirus strains. Furthermore, the presented platform was able to directly detect IAV virions spiked in nasopharyngeal swab dilution, indicating its stability and feasibility in clinical applications. Thus, this point-of-care detection platform holds great promise as a broadly applicable approach for the rapid diagnosis of influenza A.
We have developed a new three-dimensional (3D) surface for use in biosensors that is based on modified novel thorns-like polyelectrolytes (3D-PETx), which comprises of poly-l-lysine (PLL) appended with multitude oligo (ethylene glycol) (OEG) and biotin moieties. It tethered to the sensor surface by PLL, while the OEG-biotin chains are forced to stretch away from the surface for target detections. Due to its 3D structure, the number of the OEG-biotin per surface unit is markedly increased compared to conventional 2D polyelectrolytes (2D-PET) coating. Their antifouling property and sensing performance for human IgG and PSA were compared with the 2D-PET by BioLayer Interferometry (Blitz), Surface Plasmon Resonance (SPR), microfluidic devices and Enzyme-Linked ImmunoSorbent Assay (ELISA). Experimental results show that 3D-PETx presents higher sensitivity for biomarker detection both in buffer and in serum and provides an almost non-fouling surface even in undiluted serum. In addition, a sensitive PSA detection was achieved in undiluted serum with a LOD down to 0.6 ng/mL. The successful immunosensing in undiluted serum demonstrate the potential of the 3D-PETx coating for real clinical applications.
Timely detection and diagnosis are urgently needed to guide epidemiological measures, infection control, antiviral treatment, and vaccine research. In this review, biomarkers/indicators for diagnosis of coronavirus disease 2019 (COVID-19) or detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the environment are summarized and discussed. It is concluded that the detection methods targeting antibodies are not suitable for screening of early and asymptomatic cases since most patients had an antibody response at about 10 days after onset of symptoms. However, antibody detection methods can be combined with quantitative real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) to significantly improve the sensitivity and specificity of diagnosis, and boost vaccine research. Fast, sensitive and accurate detection methods targeting antigens need to be developed urgently. Various specimens for diagnosis or detection are compared and analyzed. Among them, deep throat saliva and induced sputum are desired for RT-qPCR test or other early detection technologies. Chest computerized tomography (CT) scan, RT-qPCR, lateral flow immunochromatographic strip (LFICS) for diagnosis of COVID-19 are summarized and compared. Specially, potential electrochemical biosensor, surface enhanced Raman scattering (SERS)-based biosensor, and artificial intelligence (AI) assisted diagnosis of COVID-19 are emphasized. Finally, some commercialized portable detection device, current challenges and future directions are discussed.
The pneumonia outbreak of coronavirus disease 2019 (COVID-19) represents a global issue. The bidimensional material graphene has captured much attention due to promising antimicrobial applications and has also demonstrated antiviral efficacy. In response to this global outbreak, we summarized the current state of knowledge of graphene and virus interaction as well as possible successful applications to fight COVID-19. Antibody-conjugated graphene sheets can rapidly detect targeted virus proteins and can be useful for large population screening, but also for the development of environmental sensors and filters, given the low cost of graphene materials. The functionalized graphene has demonstrated a good viral capture capacity that, combined with heat or light-mediated inactivation, could be used as a disinfectant. Graphene sensors arrays can be implemented on standard utility textiles and drug efficacy screening. Thanks to its high versatility, we foresee that graphene may have a leading role in the fight against COVID-19.
Recently, a novel coronavirus (SARS-CoV-2; coronavirus disease 2019, COVID-19) has emerged, rapidly spreading and severely straining the capacity of the global health community. Many nations are employing combinations of containment and mitigation strategies, where early diagnosis of COVID-19 is vital in controlling illness progression and limiting viral spread within the population. Thus, rapid and accurate methods of early detection are vital to contain COVID-19 and prevent further spread and predicted subsequent infectious waves of viral recurrence in future. Immediately after its initial characterization, Chinese and American Centers for Disease Control and Prevention (CDCs) rapidly employed molecular assays for detection of COVID-19, mostly employing real-time polymerase chain reaction (RT-PCR) methods. However, such methods require specific expensive items of equipment and highly trained analysts, requiring upwards of 4-8 hours to process. These requirements coupled with associated financial pressures may prevent effective deployment of such diagnostic tests. Loop mediated isothermal amplification (LAMP) is method of nucleic acid amplification which exhibits increased sensitivity and specificity are significantly rapid, and do not require expensive reagents or instruments, which aids in cost reduction for coronavirus detection. Studies have shown the successful application of LAMP assays in various forms to detect coronavirus RNA in patient samples, demonstrating that 1-10 copies of viral RNA template per reaction are sufficient for successful detection, ∼100-fold more sensitive than conventional RT-PCR methods. Importantly, studies have also now demonstrated the effectiveness of LAMP methodology in the detection of SARS-CoV-2 RNA at significantly low levels, particularly following numerous improvements to LAMP assay protocols. We hypothesise that recent advancements in enhanced LAMP protocols assay perhaps represent the best chance for a rapid and robust assay for field diagnosis of COVID-19, without the requirement of specialized equipment and highly trained professionals to interpret results. Herein, we present our arguments with a view to disseminate such findings, to assist the combat of this virus that is proving so devastating. We hope that this strategy could be applied rapidly, and confirmed for viability with clinical samples, before being rolled out for mass-diagnostic testing in these current times.
The novel SARS-CoV-2 virus has very high infectivity, which allows it to spread rapidly around the world. Attempts at slowing the pandemic at this stage depend on the number and quality of diagnostic tests performed. We propose that the olfactory epithelium from the nasal cavity may be a more appropriate tissue for detection of SARS-CoV-2 virus at the earliest stages, prior to onset of symptoms or even in asymptomatic people, as compared to commonly used sputum or nasopharyngeal swabs. Here we emphasize that the nasal cavity olfactory epithelium is the likely site of enhanced binding of SARS-CoV-2. Multiple non-neuronal cell types present in the olfactory epithelium express two host receptors, ACE2 and TMPRSS2 proteases, that facilitate SARS-CoV-2 binding, replication, and accumulation. This may be the underlying mechanism for the recently reported cases of smell dysfunction in patients with COVID-19. Moreover, the possibility of subsequent brain infection should be considered which begins in olfactory neurons. In addition, we discuss the possibility that olfactory receptor neurons may initiate rapid immune responses at early stages of the disease. We emphasize the need to undertake research focused on additional aspects of SARS-CoV-2 actions in the nervous system, especially in the olfactory pathway.
COVID-19 has spread globally since its discovery in Hubei province, China in December 2019. A combination of computed tomography imaging, whole genome sequencing, and electron microscopy were initially used to screen and identify SARS-CoV-2, the viral etiology of COVID-19. The aim of this review article is to inform the audience of diagnostic and surveillance technologies for SARS-CoV-2 and their performance characteristics. We describe point-of-care diagnostics that are on the horizon and encourage academics to advance their technologies beyond conception. Developing plug-and-play diagnostics to manage the SARS-CoV-2 outbreak would also be useful in preventing future epidemics.
A new fluorescence micromotors-based immunoassay (FMIm) has been developed for procalcitonin (PCT) determination as an early sepsis diagnostic analytical tool. The micromotors combine the high binding capacity of the specific antibod-ies onto their polymeric polypyrrol (PPy) outer layer, with their magnetic guidance (Ni layer) and self-propulsion by catalytic generation of oxygen bubbles (PtNPs inner layer), to actively recognize the PCT antigen. This FMIm allowed a sensitive (LOD = 0.07 ng mL-1) and direct PCT determination in clinical samples from very low birth weight infants (VLBWI) with sepsis suspicion, using small volumes of sample (25 µL) in a clinically relevant range of concentrations (0.5 – 150 ng mL-1). The good agreement between PCT levels obtained by our micromotor-based method and routine im-munofluorescence Hospital determination, demonstrates the feasibility for the analysis in VLBWI samples and its poten-tial as point-of-care diagnostic tool for sepsis.
Based on the exceptional and new opened biosensing possibilities of self-propelled micromotors, a micromotor-based immunoassay (MIm) has smartly been designed for C-reactive protein (CRP) determination in plasma of preterm infants with sepsis suspicion.
The design of the micromotors involved the electrosynthesis of a carbon-based outer layer (for antibody functionalization), an intermediate Ni layer (for magnetic guidance and stopped flow operations) and PtNPs inner catalytic layer (for catalytic bubble propulsion).
Micromotors biofunctionalization on the outer layer (using carbon black (CB), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs), and biocompatible propulsion capabilities, were carefully studied. Magnetic rGO/Ni/PtNPs micromotors exhibited the most efficient and reproducible (CV = 9%) anti-CRP functionalization, controlled stopped-flow operations as well as efficient bubble propulsion (1% H2O2, 1,5% NaCh, speed 140 μm s⁻¹). Analytical performance of MIm was excellent, allowing the direct (without dilution), sensitive (LOD = 0.80 μg/mL), and accurate CRP determination (Er = 1%) in hardly available preterm babies’ plasma samples with suspected sepsis using very low volumes (<10 μL) and in just 5 min of on-the-fly bioassay.
Overall, the results obtained allowed the fast and reliable sepsis diagnostics in preterm babies’ individuals with suspected sepsis, not only proving the usefulness of the approach as its potential utilization as point-of-care device for clinical analysis but drawing new horizons in extremely low sample volumes-based diagnostics.
Spontaneous periodicity is widely found in many biological and synthetic systems, and designing colloidal motors that mimic this feature may not only facilitate our understanding of how complexity emerges, but also enables applications that benefit from a time-varying activity. However, there is so far no report on a colloidal motor system that shows controllable and spontaneous oscillation in speeds. Inspired by previous studies of oscillating silver microparticles, we report silver-PMMA Janus colloidal motors that moved, interacted with tracers, and exhibited negative gravitaxis all in an oscillatory fashion. Its dynamics, including pulsating speeds and magnitude, as well as whether moving forward in a pulsating or continuous mode, can be systematically modulated by varying chemical concentrations, light intensity, and the way light was applied. A qualitative mechanism is proposed to link the oscillation of Janus colloidal motors to ionic diffusiophoresis, while nonlinearity is suspected to originate from a sequence of autocatalytic decomposition of AgCl, and its slow buildup in the presence of H2O2 and light. The generation of light-absorbing Ag nanoparticles is suspected to be the key. This study therefore establishes a robust model system of chemically driven, oscillatory colloidal motors, with which complex, emergent phenomena can be explored.
Bubble-propelled micromotors with well-engineered hierarchical porous structures are developed by a simple and flexible strategy for efficient water decontamination. Controllably and spontaneously evolved double emulsions from microfluidics are used as templates for continuous fabrication of the micromotors in one-step. The micromotors possess interconnected hierarchical porous structures with two well-aligned microscale pores incorporated in nano-porous matrix. The opening hole of one microscale pore at the bottom of micromotor is decorated with Fe3O4@Ag nanoparticles to decompose H2O2 for bubble-propelled motion. Due to their hydrophobic and magnetic hierarchical porous matrix, the micromotors can be used for capture of oil pollutants in water, and then easy recovery by using a magnetic field. Moreover, the micromotors can be flexibly functionalized by simply incorporating functional nanoparticles into the hierarchical porous structures for efficient water decontamination. This is demonstrated by modifying their hierarchical porous structures with thiol-modified SiO2 nanoparticles for efficient removal of heavy metal ions in water. These bubble-propelled hierarchical porous micromotors show great power as tools for efficient decontamination of polluted water. Moreover, the approach based on microfluidic emulsions is promising for continuous and controllable fabrication of novel micromotors with well-engineered structures and advanced functions.
MCS-MA-TEPA microparticles, with 251.22 mg g−1 of adsorption capacity for Cd(II), higher than most of the counterparts, were first fabricated by chemical coprecipitation, spray drying, and Michael addition reaction, without any cross-linker participation. These Fe3O4-nanoparticle-embedded microparticles of 5.95 μm in size, derived from modifications by methyl acrylate (MA) and tetraethylenepentamine (TEPA) on magnetic chitosan (MCS) microparticles, were of plum-pudding-like and wrinkle-like topography portrayed by TEM and SEM. Such features were beneficial to adsorbent recycling and Cd(II) capture. BET examinations illustrated 6.084 m2 g−1 of specific surface area, 0.015 mL g−1 of pore volume, and 6.536 nm of pore diameter. FTIR, VSM, XRD, TEM-SAED, TG, and DTG characterizations were indicative of successful synthesis, satisfactory magnetism, well-defined architecture, and good thermostability. Optimal adsorption parameters for Cd(II) were determined via batch experiments. Thermodynamic parameters and adsorption data fitting implied an exothermic, spontaneous, monolayer, and chemisorption process. XPS analyses confirmed a potential adsorption mechanism that N and O atoms on microparticles chelated with Cd(II) ions in solutions. Additionally, MCS-MA-TEPA-Cd(II) microparticles were magnetically separated easily and had outstanding reusability even after five-time recycling, with a slight adsorption capability loss (< 12%). Altogether, MCS-MA-TEPA microparticles might serve as a promising adsorbent for contaminated water scavenging.
Inspired by natural biological machines, lots of effort has been invested in developing artificially functional micromotors which can convert energy into movement for carrying out tasks in diverse areas. Here, we present a capillary microfluidic system with dual inner injections for one-step generation of composite structured polymer micromotors with two distinct cores of platinum (Pt) nanoparticle-integrated and iron oxide (Fe3O4) nanoparticle-dispersed hydrogels. Because the flow rates of the pre-polymerized fluids can be precisely tuned in the microfluidics, the diameters of the micromotors as well as the sizes and numbers of the inner cores can be well tailored to optimize the parameters of the resultant micromotors. When exposed to a hydrogen peroxide (H2O2) medium, the Pt-integrated cores of the micromotors could provide propulsion by expelling bubbles produced from the catalytic decomposition of H2O2, while the Fe3O4-dispersed cores could impart magnetic guidance for the micromotors. Benefiting from the close cooperation of these two types of cores, the micromotors were imparted with a strong propulsion and prominent recyclability for the delivery of both microscale and macroscale objects. These results manifest that this kind of composite micromotors have great diversity in various applications.
In this work, we present a simple droplet microfluidic approach for generating graphene oxide (GO) hydrogel composite particles for oil decontamination. By stepwise solvent exchanges, the resulted hydrophilic GO hydrogel composite particles were transferred into organic media without any chemical modifications. As the GOs were locked tightly in hydrogel network, they were hardly changed during the processes of solvent exchanges. Thus, their polar surfaces remained in direct contact with the exchanged organic media, which indicated that the transferred GO particles were capable of effectively adsorbing polar impurities. Attractively, by encapsulating hollow cores and additional magnetic nanoparticles into the emulsion templates during the fabrication, the GO hydrogel composite particles were imparted with hierarchical porous structures and controllable movement capability, both of which could improve their efficiency of impurities adsorbing. These features make the GO hydrogel composite particles described here ideal for oil decontamination.
Zika virus (ZIKV) infection is an emerging pandemic threat to humans that can be fatal in newborns. Advances in digital health systems and nanoparticles can facilitate the development of sensitive and portable detection technologies for timely management of emerging viral infections. Here we report a nanomotor-based bead-motion cellphone (NBC) system for the immunological detection of ZIKV. The presence of virus in a testing sample results in the accumulation of platinum (Pt)-nanomotors on the surface of beads, causing their motion in H2O2 solution. Then the virus concentration is detected in correlation with the change in beads motion. The developed NBC system was capable of detecting ZIKV in samples with virus concentrations as low as 1 particle/μL. The NBC system allowed a highly specific detection of ZIKV in the presence of the closely related dengue virus and other neurotropic viruses, such as herpes simplex virus type 1 and human cytomegalovirus. The NBC platform technology has the potential to be used in the development of point-of-care diagnostics for pathogen detection and disease management in developed and developing countries.
Food poisoning caused by bacteria is a major cause of disease and death worldwide. Herein we describe the use of Janus micromotors as mobile sensors for the detection of toxins released by enterobacteria as indicators of food contamination. The micromotors are prepared by a pickering emulsion approach and rely on the simultaneous encapsulation of platinum nanoparticles -for enhanced bubble-propulsion- and receptor-functionalized quantum dots (QDs) for selective binding with the 3-deoxy-d-manno-oct-2-ulosonic acid target in the endotoxin molecule. Lipopolysaccharides (LPS) from Salmonella enterica were used as target endotoxins, which upon interaction with the QDs induce a rapid quenching of the native fluo-rescence of the micromotors in a concentration-dependent manner. The micromotor assay can readily detect concentrations as low as 0.07 ng mL-1 of endotoxin, which is far below the level considered toxic to humans (275 µg mL-1). Micromotors have been successfully applied for the detection of Salmonella toxin in food samples in 15 minutes compared to several hours required by existing Gold Standard method. Such ultrafast and reliable approach holds considerable promise for food contamination screening while awaiting the results of bacterial cultures in a myriad of food safety and security defense applications
While chemical communication plays a key role in diverse natural processes, the intelligent chemical communication between synthetic nanomotors remains unexplored. Here we demonstrate the design and operation of bio-inspired synthetic nanomotors capable of chemical communication among themselves that influences their propulsion behavior. The chemical message is sent from a moving 'activator' motor to a nearby 'activated' (receiver) one, and involves release of silver ions from a Janus PS/Ni/Au/Ag 'activator' motor to the 'activated' Janus SiO2/Pt nanomotor. The transmitted silver signal is translated rapidly into a dramatic speed change associated with the enhanced catalytic activity of 'activated' motors. The concept of establishing chemical communication between different synthetic nanomotors paves the way to intelligent nanoscale robotic systems that are capable of cooperating with each other.
Micromotors are important for a wide variety of applications. Here, we develop a microfluidic approach for one-step fabrication of Janus self-propelled micromotor with multiple functions. By fine tuning the fabrication...
Immunosensors are biosensors based on interactions between an antibody and antigen on a transducer surface. Either antibody or antigen can be the species immobilized on the transducer to detect antigen or antibody, respectively. Because of the strong binding forces between these biomolecules, immunosensors present high selectivity and very high sensitivity, making them very attractive for many applications in different science fields. Electrochemical immunosensors explore measurements of an electrical signal produced on an electrochemical transductor. This signal can be voltammetric, potentiometric, conductometric or impedimetric. Immunosensors utilizing electrochemical detection have been explored in several analyses since they are specific, simple, portable, and generally disposable and can carry out in situ or automated detection. This review addresses the potential of immunosensors destined for application in food and environmental analysis, and cancer biomarker diagnosis. Emphasis is given to the approaches that have been used for construction of electrochemical immunosensors. Additionally, the fundamentals of immunosensors, technology of transducers and nanomaterials and a general overview of the possible applications of electrochemical immunosensors to the food, environmental and diseases analysis fields are described.
RT-qPCR allows sensitive detection of viral particles of both infectious and noninfectious viruses in water environments, but cannot discriminate non-infectious from infectious viruses. In this study, we aimed to optimize RT-qPCR-based detection of chlorine-inactivated human norovirus (NoV) and pepper mild mottle virus (PMMoV) in suspension by pretreatment with an optimal combination of a monoazide and a detergent that can efficiently penetrate damaged viral capsids. Four methods were compared to determine the efficacy of chlorine disinfection (at 1, 3, and 5 min mg/L): (A) RT-qPCR alone, (B) RT-qPCR assay preceded by magnetic bead separation for enrichment of viral particles (MBS-RT-qPCR), (C) MBS-RT-qPCR assay with pretreatment with propidium monoazide (PMA-MBS-RT-qPCR), and (D) PMA-MBS-RT-qPCR assay with pretreatment with sodium lauroyl sarcosinate (INCI-PMA-MBS-RT-qPCR). On the basis of a PMA optimization assay, 200 and 300 μM PMA were used in subsequent experiments for NoV GII.4 and PMMoV, respectively. Optimal INCI concentrations, having minimal influence on NoV GII.4 and PMMoV, were found to be 0.5% and 0.2% INCI, respectively. For NoV GII.4, there were significant differences (P < 0.05) in log10 genome copies between the PMA-treated and the INCI + PMA-treated samples (log10 genome copies differed by 1.11 and 0.59 log10 for 3 and 5 min mg/L of chlorine, respectively). For PMMoV, INCI induced differences in log10 genome copies of 0.92, 1.18, and 1.86, for 1, 3, and 5 min mg/L of chlorine, respectively. Overall, the results of this study indicate that an optimal combination of PMA and INCI could be very useful for evaluating disinfection methods in water treatment strategies.
Light, as an external stimulus, is capable of driving the motion of micro/nanomotors (MNMs) with the advantages of reversible, wireless and remote manoeuvre on demand with excellent spatial and temporal resolution. This review focuses on the state-of-the-art light-driven MNMs, which are able to move in liquids or on a substrate surface by converting light energy into mechanical work. The general design strategies for constructing asymmetric fields around light-driven MNMs to propel themselves are introduced as well as the photoactive materials for light-driven MNMs, including photocatalytic materials, photothermal materials and photochromic materials. Then, the propulsion mechanisms and motion behaviors of the so far developed light-driven MNMs are illustrated in detail involving light-induced phoretic propulsion, bubble recoil and interfacial tension gradient, followed by recent progress in the light-driven movement of liquid crystalline elastomers based on light-induced deformation. An outlook is further presented on the future development of light-driven MNMs towards overcoming key challenges after summarizing the potential applications in biomedical, environmental and micro/nanoengineering fields.
Magnetocatalytic hybrid Janus micromotors encapsulating phenylboronic acid (PABA) modified graphene quantum dots (GQDs) are described herein as ultrafast sensors for the detection of deadly bacteria endotoxins. A bottom-up approach was adopted to synthesize an oil-in-water emulsion containing the GQDs along with a high loading of platinum and iron oxide nanoparticles on one side of the Janus micromotor body. The two different "active regions" enable highly efficient propulsion in the presence of hydrogen peroxide or magnetic actuation without the addition of a chemical fuel. Fluorescence quenching was observed upon the interaction of GQDs with the target endotoxin (LPS), whereby the PABA tags acted as highly specific recognition receptors of the LPS core polysaccharide region. Such adaptive hybrid operation and highly specific detection hold considerable promise for diverse clinical, agrofood, and biological applications and integration in future lab-on-chip technology.
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.
A rapid and efficient micromotor-based bacteria killing strategy is described. The new antibacterial approach couples the attractive antibacterial properties of chitosan with the efficient water-powered propulsion of magnesium (Mg) micromotors. These Janus micromotors consist of Mg microparticles coated with the biodegradable and biocompatible polymers poly(lactic-co-glycolic acid) (PLGA), alginate (Alg) and chitosan (Chi), with the latter responsible of the antibacterial properties of the micromotor. The distinct speed and efficiency advantages of the new micromotor-based environmental-friendly antibacterial approach have been demonstrated in various control experiments by treating drinking water contaminated with model Escherichia coli (E.coli) bacteria. The new dynamic antibacterial strategy offers dramatic improvements in the antibacterial efficiency, compared to static chitosan-coated microparticles (e.g., 27-fold enhancement), with a 96% killing efficiency within 10 min. Potential real-life applications of these chitosan-based micromotors for environmental remediation have been demonstrated by the efficient treatment of seawater and fresh water samples contaminated with unknown bacteria. Coupling the efficient water-driven propulsion of such biodegradable and biocompatible micromotors with the antibacterial properties of chitosan, holds great considerable promise for advanced antimicrobial water treatment operations.
The self-motile Janus colloids are important for enabling a wide variety of micro-technology applications as well as for improving our understanding of the mechanisms of motion of artificial micro- and nano-swimmers. We present here a novel type of micro/nano-motors which possess a reversed Janus structure of an internal catalytic "chemical engine". The catalytic material (here platinum (Pt)) is embedded within the interior of the mesoporous silica (mSiO2) based hollow particles, and triggers the decomposition of H2O2 when suspended in an aqueous peroxide (H2O2) solution. The pores/gaps at the non-catalytic (Pt) half-hemisphere allow the exchange of chemical species in solution between the exterior and the interior of the particle. By varying the diameter of the particles, we observed size dependent motile behavior in the form of: enhanced diffusion for 500 nm particles, and self-phoretic motion, towards the non-metallic part, for 1.5 µm and 3 µm ones. The direction of motion was rationalized by a theoretical model based on self-phoresis. For the 3 µm particles, a change in the morphology of the porous part is observed, which is accompanied by a change in the mechanism of propulsion via bubble nucleation and ejection, as well as a change in the direction of motion.
2D molybdenum disulfide (MoS2) is herein explored as an advanced surface material in the fabrication of powerful tubular microengines. The new catalytic self-propelled open-tube bilayer microengines have been fabricated using a template electrodeposition and couple the unique properties of sp2 hybridized MoS2 with highly reactive inner granular Pt catalytic structures. The MoS2/metal microengines display extremely efficient bubble propulsion, reflecting the granular structure of the inner catalytic platinum or gold layers (compared to the smooth metal surfaces of common micromotors). The efficient movement of functionalized MoS2 micromotors can address challenges imposed by slow mass transport processes involved in various applications of MoS2. The delocalized electron network of the MoS2 outer layer facilitates π-π stacking interactions and endows the tubular microengines with a diverse array of capabilities. These are demonstrated here for efficient loading and release of the drug doxorubicin, and rapid and sensitive "OFF-ON" fluorescent detection of important nucleic acids (miRNA-21) and proteins (thrombin) using microengines modified with dye-labeled single-stranded DNA and aptamer, respectively. Such coupling of the attractive capabilities of 2D-MoS2 nanosheets with rapidly moving microengines provides an opportunity to develop multifunctional micromachines for diverse biomedical applications ranging from efficient drug delivery to the detection of important bioanalytes.
A novel Janus micromotor-based strategy for the direct determination of diphenyl phthalate (DPP) in food and biological samples is presented. Mg/Au Janus micromotors are employed as novel analytical platforms for the degradation of the non-electroactive DPP into phenol, which is directly measured by difference pulse voltammetry on disposable screen-printed electrodes. The self-movement of the micromotors along the samples result in the generation of hydrogen microbubbles and hydroxyl ions for DPP degradation. The increased fluid transport improves dramatically the analytical signal, increasing the sensitivity while lowering the detection potential. The method has been successfully applied to the direct analysis of DPP in selected food and biological samples, without any sample treatment and avoiding any potential contamination from laboratory equipment. The developed approach is fast (~5 min) and accurate with recoveries of ~100%. In addition, efficient propulsion of multiple Mg/Au micromotors in complex samples has also been demonstrated. The advantages of the micromotors assisted technology i.e., disposability, portability and the possibility to carry out multiple analysis simultaneously hold considerable promise for its application in food and biological control in analytical applications with high significance.
An effective and rapid bacterial killing nanotechnology strategy based on lysozyme-modified fuel-free nanomotors is demonstrated. The efficient antibacterial property of lysozyme, associated with the cleavage of glycosidic bonds of peptidoglycans present in the bacteria cell wall, has been combined with ultrasound (US)-propelled porous gold nanowire (p-AuNW) motors as biocompatible dynamic bacteria nanofighters. Coupling the antibacterial activity of the enzyme with the rapid movement of these p-AuNWs, along with the corresponding fluid dynamics, promotes enzyme-bacteria interactions and prevents surface aggregation of dead bacteria, resulting in a greatly enhanced bacteria-killing capability. The large active surface area of these nanoporous motors offers a significantly higher enzyme loading capacity compared to non-porous AuNWs, which results in a higher antimicrobial activity against Gram-positive and Gram-negative bacteria. Detailed characterization studies and control experiments provide useful insights into the underlying factors controlling the antibacterial performance of the new dynamic bacteria nanofighters. Rapid and effective killing of the Gram-positive Micrococcus lysodeikticus bacteria (69-84% within 1-5 min) is demonstrated.
Specifically capturing and restraining residual circulating tumor cells (CTCs) in cancer patients are the sine qua non for safely and effectively preventing cancer metastasis, to which the current chemotherapy has been limited due to its toxicity. Moreover, because of CTCs’ rarity and low activity, the current technology for capturing CTCs based solely on a single surface biomarker has limited capacity and is used mainly for in vitro diagnosis. Here, it is possible to sequentially conjugate two CTCs antibodies (aEpCAM and aSlex) to the functionalized dendrimers to specifically capture human hepatocellular CTCs in both artificial and clinical patient blood samples, and restrain their activities. The molecular entities of the conjugates are demonstrated by various means. The dual antibody conjugate captured CTCs threefold more than the single counterparts from the high concentrations of interfering red blood cells or leukocytes, as well as from the blood of liver cancer patients, and exhibits the superiority to their single counterparts in down-regulating the captured CTCs. These results collectively provide the strong evidence that two antibodies can be compatibly conjugated to a nanomaterial, resulting in an enhanced specificity in restraining CTCs in blood.
A motor-based autonomous microsensor is proposed for in situ visualization immunoassay of cancer biomarker through motion readout or tag counting. The microsensor is prepared by functionalizing a newly designed gold nanoparticle-modified self-propelled polyaniline/Pt (AuNP/PANI/Pt) micromotor with capture antibody. The autonomous movement of microsensor in the fuel-enhanced sample mixture results in fast and selective recognition of protein target and subsequently loading of the secondary antibody-modified glycidyl methacrylate microspheres (GMA), which slows down the movement of the sensing microengine. The velocity of microsensor and the number of GMA conjugated on microsensor can be conveniently visualized using optical microscopy. They are negatively and positively correlated with the target concentration, respectively. Therefore, the microsensor can conveniently distinguish the concentration of carcinoembryonic antigen in a range of 1-1000 ng/mL. The motor-based microsensor can easily be prepared in batch using AuNP/PANI/Pt. The whole detection procedure for protein target can be completed in 5 min without any washing and separation step. This method shows considerable promise for diverse clinical and diagnostic applications.
Enrichment of viruses is essential for making high dose viral stocks for vaccines and virus-related researches. Since the widely used ultracentrifugation for concentrating viral stock requires ultra-high speed rotation, it easily destroys the activity of some viruses, for instance, hepatitis c virus (HCV), which has a fragile structure and low virus titer. We introduce a novel method to concentrate HCV virus in stock by using a hierarchically self-organized monolithic nanoporous membrane made by stepwise anodization. The pores at the top part of the membrane have very regular sizes that are suitable for the perfect filtration of the virus particles in the stock. On the other hand, the remaining part has large pores that maintain high flux and mechanical strength of the membrane under high pressure (up to 10 bar). The enrichment efficiency of HCV in crude stocks by using the membrane became over 91%, which is four times higher than that (~22%) obtained by conventionally used centrifugation. A very high efficiency results from the perfect filtration and no damage to the virion particles during the enrichment process, whereas significant damage to the HCV occurs during centrifugation. The hierarchically self-organized monolithic nanoporous membrane could be effectively employed for concentrating various fragile viruses in stocks, for instance, rabies virus and human immunodeficiency virus in addition to HCV virus.