Functionalized gold nanoparticle supported sensory mechanisms applied in detection of chemical and biological threat agents: a review

Single-Domain Antibody-Gold Nanoparticle Bioconjugates as Immunosensors for the Detection of Hantaviruses

INTRODUCTION

Hantavirus, a zoonotic pathogen, causes severe syndromes like hemorrhagic fever with renal syndrome (HFRS), sometimes fatal in humans. Considering the importance of detecting the hantavirus antigen, the construction of an immunosensor is essential. The structural and functional characteristics of camelid nanobodies (VHHs) encourage their application in the areas of nanobiotechnology, therapeutics, diagnostics, and basic research. Therefore, this study aimed to standardize stable bioconjugates using gold nanoparticles (AuNPs) and VHHs, in order to develop immunobiosensors for the diagnosis of hantavirus infection.

METHODS

Immobilized metal affinity chromatography (IMAC) was performed to obtain purified recombinant anti-hantavirus nucleocapsid nanobodies (anti-prNΔ85 VHH), while AuNPs were synthesized for bioconjugation. UV-visible spectrophotometry and transmission electron microscopy (TEM) analysis were employed to characterize AuNPs.

RESULTS

The bioconjugation stability parameters (VHH-AuNPs), analyzed by spectrophotometry, showed that the ideal pH value and VHH concentration were obtained at 7.4 and 50 μg/mL, respectively, after addition of 1 M NaCl, which induces AuNP aggregation. TEM performed before and after bioconjugation showed uniform, homogeneous, well-dispersed, and spherical AuNPs with an average diameter of ~ 14 ± 0.57 nm. Furthermore, high-resolution images revealed a thin white halo on the surface of the AuNPs, indicating the coating of the AuNPs with protein. A biosensor simulation test (dot blot-like [DB-like]) was performed in stationary phase to verify the binding and detection limits of the recombinant nucleocapsid protein from the Araucária hantavirus strain (prN∆85).

DISCUSSION

Using AuNPs/VHH bioconjugates, a specific interaction was detected between 5 and 10 min of reaction in a dose-dependent manner. It was observed that this test was sensitive enough to detect prNΔ85 at concentrations up to 25 ng/μL. Considering that nanostructured biological systems such as antibodies conjugated with AuNPs are useful tools for the development of chemical and biological sensors, the stability of the bioconjugate indicates proficiency in detecting antigens. The experimental results obtained will be used in a future immunospot assay or lateral flow immunochromatography analysis for hantavirus detection.

Gold Nanoparticles AuNP Decorated on Fused Graphene-like Materials for Application in a Hydrogen Generation

The search for a sustainable, alternative fuel source to replace fossil fuels has led to an increased interest in hydrogen fuel. This combustible gas is not only clean-burning but can readily be produced via the hydrolysis of sodium borohydride. The main drawback of this reaction is that the reaction occurs relatively slowly and requires a catalyst to improve efficiency. This study explored a novel composite material made by combining gold nanoparticles and fused graphene-like materials (AuFGLM) as a catalyst for generating hydrogen via sodium borohydride. The novel fused graphene-like material (FGLM) was made with a sustainable dextrose solution and by using a pressure-processing method. Imaging techniques showed that FGLM appears to be an effective support template for nanoparticles. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize and determine the size, shape, and structure of nanoparticles and composites. The TEM study characterized the fused carbon backbone as it began to take on a rounder shape. The TEM images also revealed that the average diameter of the gold nanoparticle was roughly 23 nm. The FTIR study confirmed O-H, C-C, and C=O as functional groups in the materials. The EDS analysis showed that the composite contained approximately 6.3% gold by weight. The crystal structures of FGLM and AuFGLM were identified via P-XRD analysis. Various reaction conditions were used to test the catalytic ability of AuFGLM, including various solution pHs, temperatures, and doses of NaBH₄. It was observed that optimal reaction conditions included high temperature, an acidic solution pH, and a higher dose of NaBH₄. The activation energy of the reaction was determined to be 45.5 kJ mol^-1, and it was found that the catalyst could be used multiple times in a row with an increased volume of hydrogen produced in ensuing trials. The activation energy of this novel catalyst is competitive compared to similar catalysts and its ability to produce hydrogen over multiple uses makes the material an exciting choice for catalyzing the hydrolysis of NaBH₄ for use as a hydrogen fuel source.

Quantitative and qualitative analyses of metal ions in food and water by using a multicolor sensor array and chemometrics

Rapid and accurate detection of toxic metal ions is the key to combating food contamination and environmental pollution. In sensor arrays, gold nanoparticles play a crucial role in monitoring metal ions based on surface plasmon resonance. However, identifying metal ions with unknown concentrations in a complex system through this assay is difficult because of its monotonous color change and weak anti-interference ability. To overcome these limitations, a sensitive, flexible, low-cost, and multicolor sensor array was designed herein. The applicability of the sensor array for the qualitative and quantitative analyses of metal ions in food and water was also verified. The developed sensor array could classify 14 metal ions (Cu²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Cr³⁺, Co²⁺, Ba²⁺, K⁺, Tl⁺, Pb²⁺, and Hg²⁺) of unknown concentration with an accuracy of 100%. In addition, partial least squares models were established to quantify Tl⁺, Pb²⁺, and Hg²⁺ in water and rice samples, with square correlation coefficients (R²) of 0.9991, 0.9742, and 0.9731, respectively. This method can be used for accurate quantitative and qualitative analyses of heavy metal ions in water and food.

Micro and Nano Interdigitated Electrode Array (IDEA)-Based MEMS/NEMS as Electrochemical Transducers: A Review

Micro and nano interdigitated electrode array (µ/n-IDEA) configurations are prominent working electrodes in the fabrication of electrochemical sensors/biosensors, as their design benefits sensor achievement. This paper reviews µ/n-IDEA as working electrodes in four-electrode electrochemical sensors in terms of two-dimensional (2D) planar IDEA and three-dimensional (3D) IDEA configurations using carbon or metal as the starting materials. In this regard, the enhancement of IDEAs-based biosensors focuses on controlling the width and gap measurements between the adjacent fingers and increases the IDEA's height. Several distinctive methods used to expand the surface area of 3D IDEAs, such as a unique 3D IDEA design, integration of mesh, microchannel, vertically aligned carbon nanotubes (VACNT), and nanoparticles, are demonstrated and discussed. More notably, the conventional four-electrode system, consisting of reference and counter electrodes will be compared to the highly novel two-electrode system that adopts IDEA's shape. Compared to the 2D planar IDEA, the expansion of the surface area in 3D IDEAs demonstrated significant changes in the performance of electrochemical sensors. Furthermore, the challenges faced by current IDEAs-based electrochemical biosensors and their potential solutions for future directions are presented herein.

Implication of Nanoparticles to Combat Chronic Liver and Kidney Diseases: Progress and Perspectives

Liver and kidney diseases are the most frequently encountered problems around the globe. Damage to the liver and kidney may occur as a result of exposure to various drugs, chemicals, toxins, and pathogens, leading to severe disease conditions such as cirrhosis, fibrosis, hepatitis, acute kidney injury, and liver and renal failure. In this regard, the use of nanoparticles (NPs) such as silver nanoparticles (AgNPs), gold nanoparticles (AuNPs), and zinc oxide nanoparticles (ZnONPs) has emerged as a rapidly developing field of study in terms of safe delivery of various medications to target organs with minimal side effects. Due to their physical characteristics, NPs have inherent pharmacological effects, and an accidental buildup can have a significant impact on the structure and function of the liver and kidney. By suppressing the expression of the proinflammatory cytokines iNOS and COX-2, NPs are known to possess anti-inflammatory effects. Additionally, NPs have demonstrated their ability to operate as an antioxidant, squelching the generation of ROS caused by substances that cause oxidative stress. Finally, because of their pro-oxidant properties, they are also known to increase the level of ROS, which causes malignant liver and kidney cells to undergo apoptosis. As a result, NPs can be regarded as a double-edged sword whose inherent therapeutic benefits can be refined as we work to comprehend them in terms of their toxicity.

Advances in Noble-Metal Nanoparticle-Based Fluorescence Detection of Organophosphorus Chemical Warfare Agents

Efficient and simple detection of chemical warfare agents (CWAs) is an essential step in minimizing the potentially lethal consequences of chemical weapons. CWAs are a family of organic chemicals that are used as chemical weapons because of their enormous severity and lethal effects when faced with unforeseen challenges. To stop the spread of CWAs, it is critical to develop a platform that detects them in a sensitive, timely, selective, and minimally invasive manner. Rapid advances in the demand for on-site sensors, metal nanoparticles, and biomarker identification for CWAs have made it possible to use fluorescence as a precise real-time and point-of-care (POCT) testing technique. For POCT-based applications, the new capabilities of micro- and nanomotors offer enormous prospects. In recent decades, significant progress has been made in the design of fluorescent sensors and the further development of noble metal nanoparticles for the detection of organophosphorus CWAs, as described in this review. Through this work, recent attempts to fabricate sensors that can detect organophosphorus CWAs through changes in their fluorescence properties have been summarized. Finally, an integrated outlook on how noble metal nanoparticles could be used to develop smart sensors for organophosphorus CWAs that communicate with and control electronic devices to monitor and improve the health of individuals.

Gold-based nanoplatform for a rapid lateral flow immunochromatographic test assay for gluten detection

Background

Gluten, a food allergen, is available in foods derived from wheat, rye and barley. It damages the small intestine and causes celiac disease. Herein, we designed a rapid immunochromatographic lateral flow test assay for detecting the gluten contents of raw materials. In this rapid test, the presence of gluten was screened through the capturing of gliadin (a toxic component of gluten) by two identical gliadin monoclonal antibodies. One of the antibodies was immobilized on the membrane in the test zone as a capture reagent. The other antibody was labeled with gold nanoparticles (AuNPs) as a detector reagent.

Results

Gold nanoparticles with a size of about 20 nm were synthesized and conjugated to the gliadin monoclonal antibodies. The detection limit of the experimental assay was 20 ppm and positive results were visualized after 15 min using only 40 μL of the extracted sample for each test. Analysis of different flour samples identified the best sensitivity and specificity of the lateral flow test strip (LFTS).

Conclusion

The experimental LFTS is an easy-to-use and rapid method for the screening of gluten level in raw materials. The LFTS may be employed to ensure the safety of foods.

Role of Capping Agent for the Colorimetric and Fluorescent Sensing of Different Materials Using Metal Nanoparticles

Background:

The selection of capping agent depends on the method of synthesis, nature of nanoparticles (NPs), and type of the compounds to be analyzed. Therefore, different types of capping agents such as surfactants, drugs, amino acids, fatty acids, and polymers are used to increase stability of NPs, avoid aggregation, keep NPs away from one another, thereby achieving desired morphology as well as the size of NPs.

Introduction:

Recently, the fabrication of NPs has been extensively carried out using synthetic chemical routes in a wide range of materials. In this review, a comprehensive assessment of the colorimetric and fluorescent sensing of metal nanoparticles using different capped agents, such as surfactants, drugs, amino acids, fatty acids, and polymers has been summarized for the present and future strategies.

Method:

For the synthesis of metal nanoparticles, different methods, metals, and a variety of capping agents are used to obtain new properties and explore opportunities for innovative applications.

Result:

Capping agents perform their significant role as stabilizers to avoid the over-growth and coagulation of nanoparticles.

Conclusion:

Capping agents play an essential role in the colorimetric and fluorescent sensing of metal nanoparticles for particular analytes.

3D-Printed, Portable, Fluorescent-Sensing Platform for Smartphone-Capable Detection of Organophosphorus Residue Using Reaction-Based Aggregation Induced Emission Luminogens

Development of an easy-to-use, low-cost, household device can help the consumer quickly identify an organophosphorus (OP) residue concentration level. In this work, we demonstrate a 3D-printed, portable, fluorescent-sensing platform for smartphone-capable detection of OPs in vegetables. For development of the proposed device, we utilize the smartphone for capturing the strong thiol-activated fluorescence, which was produced by hydrolysis of OPs in the presence of alkali. The thiol-responsive AIEgen (maleimide-functionalized tetraphenylethylene) was non-emissive in both solution and the solid state but could be readily lighted up by the click addition of thiol to its MI pendant. An android application "Detection" has been developed on the basis of the gray value to analyze the different concentration levels of OPs in vegetable samples. The gray value was linearly related with the concentration of five kinds of organophosphorus residue, ranging from 0 to 20 μg/mL. It was also applied for determination of OPs residue in the leaves of cowpea, celery, and Chinese cabbage. Different from acetylcholinesterase enzyme-based sensors for poor stability under high temperature, the proposed method was a direct detection method for OPs and can be used for rapid monitoring of OPs residue concentration levels before LC-MS analysis.

Recent Trends in Noble Metal Nanoparticles for Colorimetric Chemical Sensing and Micro-Electronic Packaging Applications

Noble metal NPs are highly attractive candidates because of their unique combination of physical, chemical, mechanical, and structural properties. A lot of developments in this area are still fascinating the materials research community, and are broadly categorized in various sectors such as chemical sensors, biosensors, Förster resonance energy transfer (FRET), and microelectronic applications. The related function and properties of the noble metals in these areas can be further tailored by tuning their chemical, optical, and electronic properties that are influenced by their size, shape, and distribution. The most widely used Au and Ag NPs in dispersed phase below 100 nm exhibit strong color change in the visible range which alters upon aggregation of the NPs. The chemical sensing of the analyte is influenced by these NPs aggregates. In this article, we have summarized the uniqueness of noble metal NPs, their synthesis methods, nucleation and growth process, and their important applications in chemical sensing, microelectronic packaging, and Förster resonance energy transfer.

FEAST of biosensors: Food, environmental and agricultural sensing technologies (FEAST) in North America

We review the challenges and opportunities for biosensor research in North America aimed to accelerate translational research. We call for platform approaches based on: i) tools that can support interoperability between food, environment and agriculture, ii) open-source tools for analytics, iii) algorithms used for data and information arbitrage, and iv) use-inspired sensor design. We summarize select mobile devices and phone-based biosensors that couple analytical systems with biosensors for improving decision support. Over 100 biosensors developed by labs in North America were analyzed, including lab-based and portable devices. The results of this literature review show that nearly one quarter of the manuscripts focused on fundamental platform development or material characterization. Among the biosensors analyzed for food (post-harvest) or environmental applications, most devices were based on optical transduction (whether a lab assay or portable device). Most biosensors for agricultural applications were based on electrochemical transduction and few utilized a mobile platform. Presently, the FEAST of biosensors has produced a wealth of opportunity but faces a famine of actionable information without a platform for analytics.

Visualization of O2/ATP cross-talk in living cells with a smart fluorescent nanoprobe

Herein, we propose a dual-responsive fluorescent nanoprobe to visualize the cross-talk between O2 and adenosine triphosphate (ATP) in living cells. We hope it will be a helpful tool for the further understanding of cellular metabolism and further facilitating risk warning in the process of adaptation to consistent environmental pressures in premalignant lesions.

Plasmonic Sensors for Monitoring Biological and Chemical Threat Agents

Sensors are excellent options owing to their ability to figure out a large number of problems and challenges in several areas, including homeland security, defense, medicine, pharmacology, industry, environment, agriculture, food safety, and so on. Plasmonic sensors are used as detection devices that have important properties, such as rapid recognition, real-time analysis, no need labels, sensitive and selective sensing, portability, and, more importantly, simplicity in identifying target analytes. This review summarizes the state-of-art molecular recognition of biological and chemical threat agents. For this purpose, the principle of the plasmonic sensor is briefly explained and then the use of plasmonic sensors in the monitoring of a broad range of biological and chemical threat agents is extensively discussed with different types of threats according to the latest literature. A conclusion and future perspectives are added at the end of the review.

Multiple tier detection of TNT using curcumin functionalized silver nanoparticles

The rapid, selective and sensitive detection of trinitrotoluene (TNT), which is widely used in terrorist activities and also a major environmental contaminant is prime concern for the scientific community dealing with environmental problems and national security. This paper described unprecedented CAgP based multiple tier probe employing U.V.–Vis., DLS & SERS techniques for highly selective, rapid and ultrasensitive detection of TNT up to 0.1 nM level. The as synthesized CAgP made possible the naked eye detection of TNT in the form of flakes in real time. The developed method due to its multiple tier approach utilizing the same sample could easily be extended to a high-throughput format and can be utilized for rapid and reliable trace detection of TNT, for on-site screenings in airports, analysis of forensic samples, and environmental analysis.

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TNT can interact with curcumin functionalized Ag NPs through p-donor-acceptor interaction.

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Curcumin functionalized Ag NPs can be used as an ultrasensitive optical probe for TNT detection.

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The probe has an excellent selectivity for TNT against other nitro compounds.

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The probe can detect TNT at multiple levels using U.V–Vis., DLS and SERS.

Discrimination of narcotic drugs in human urine based on nanoplasmonics combined with chemometric method

The detection of psychoactive substances is an important branch of modern analytical chemistry and has many legally and socially relevant implications. The use of a surface plasmon resonance (SPR)-based gene-nanoparticle system has emerged as a promising technique for the rapid and ultrasensitive detection of molecular species such as drugs of abuse in biofluids. However, the development of a viable screening tool for the detection of multiple classes of drugs in complex media is a considerable challenge because the existing techniques lack affinity toward certain species due to matrix interference. Our aim was to develop a simple optical sensor array for the classification of nine narcotic drugs in aqueous solution and human urine. The UV-vis spectra of DNA-gold nanoparticles in the presence of nine narcotic drugs (pentobarbital sodium, caffeine, morphine, remifentanil, fentanyl, ketamine, etomidate, carfentanil, and sulfentanyl) were distinctly different. Furthermore, the narcotic drugs present in aqueous solution and in human urine were classified correctly through partial least squares discriminant analysis (PLS-DA). Combination with a multi-sensor unit further improved the prediction accuracy of the PLS-DA models. The proposed method has potential for on-site drug detection and drug abuse screening.

Recent Advances of Plasmonic Gold Nanoparticles in Optical Sensing and Therapy

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Gold nanoparticles with special surface plasmon resonance have been widely used in sensing and therapy because of their easy preparation, unique optical properties, excellent biocompatibility, etc. The applications of gold nanoparticles in chemo/biosensing, imaging, and therapy reported in 2016-2019, are summarized in this review. Regarding the gold nanoparticle-based sensing or imaging, sensing mechanisms and strategies are provided to illustrate the concepts for designing sensitive and selective detection platforms. Gold nanoparticlemediated therapy is introduced by surface plasmon resonance-based therapy and delivery-based therapy. Beyond the sole therapeutic system, platforms through synergistic therapy are also discussed. In the end, discussion of the challenges and future trends of gold nanoparticle-based sensing and therapy systems is described.

Bioconjugated Plasmonic Nanoparticles for Enhanced Skin Penetration

Plasmonic nanoparticles (NPs) are one of the most promising and studied inorganic nanomaterials for different biomedical applications. Plasmonic NPs have excellent biocompatibility, long-term stability against physical and chemical degradation, relevant optical properties, well-known synthesis methods and tuneable surface functionalities. Herein, we review recently reported bioconjugated plasmonic NPs using different chemical approaches and loading cargoes (such as drugs, genes, and proteins) for enhancement of transdermal delivery across biological tissues. The main aim is to understand the interaction of the complex skin structure with biomimetic plasmonic NPs. This knowledge is not only important in enhancing transdermal delivery of pharmaceutical formulations but also for controlling undesired skin penetration of industrial products, such as cosmetics, sunscreen formulations and any other mass-usage consumable that contains plasmonic NPs.

Complementation of ELISA and an Interdigitated Electrode Surface in Gold Nanoparticle Functionalization for Effective Detection of Human Blood Clotting Defects

Developing an enhanced diagnosis using biosensors is important for the treatment of patients before disease complications arise. Improving biosensors would enable the detection of various low-abundance disease biomarkers. Efficient immobilization of probes/receptors on the sensing surface is one of the efficient ways to enhance detection. Herein, we introduced the pre-alkaline sensing surface with amine functionalization for capturing gold nanoparticle (GNP) conjugated to human blood clotting factor IX (FIX), and we demonstrated the excellent performance of the strategy. We have chosen the enzyme-linked immunosorbent assay (ELISA) and the interdigitated electrode (IDE), which are widely used, to demonstrate our method. The optimal amount for silanization has been found to be 2.5%, and 15-nm-sized GNPs are ideal and characterized. The limit of FIX detection was attained with ELISA at 100 pM with the premixed GNPs and FIX, which shows 60-fold improvement in sensitivity without biofouling, as compared to the conventional ELISA. Further, FIX was detected with higher specificity in human serum at a 1:1280 dilution, which is equivalent to 120 pM FIX. These results were complemented by the analysis on IDE, where improved detection at 25 pM was achieved, and FIX was detected in human serum at the dilution of 1:640. These optimized surfaces are useful for improving the detection of different diseases on varied sensing surfaces.

Spectrographic sensors for uranyl detection in the environment

More and more severe energy problem triggers extensive application of nuclear energy, and the adverse effects brought by nuclear materials such as uranyl to the environment are becoming the concern, as it has become a threat to human's health. Therefore, the detection of uranyl is increasingly important, which aims to make the application of uranium under surveillance and protection. A lot of detection methods employing varying materials based on different techniques for uranyl have been proposed including those using expensive and complicated instruments such as ICP-MS, ESI-MS, and neutron activation analysis etc. Those methods based on expensive instruments often provide quite low limit of detection (LOD) and excellent validity and repeatability, however, methods that are low-cost, convenient and rapid are in demand because these are satisfied characters for on-site and in-time determination. In the review, we discuss uranyl sensors based on spectrographic techniques, which is facile and promising for rapid assessment of uranium content in practical application. Spectrographic techniques including fluorescence, UV-vis spectrophotometry, resonance light scattering (RLS) and surface enhanced Raman scattering (SERS) are evaluated. In detail, the core materials that playing extremely important roles in detection performance are stated consisting of small molecule, biomolecule, polymer and nanomaterial.

Quenching of Luminol Fluorescence at Nano-Bio Interface: Towards the Development of an Efficient Energy Transfer System

Surface modified colloidal gold (Au) and silver (Ag) nanoparticles (NPs) were used as efficient quenchers of luminol (LH₂) fluorescence either in homogeneous aqueous medium or its noncovalent assembly with bovine serum albumin (BSA). The mechanism as well as the extent of fluorescence quenching was found to be strongly dependent on the nature of the nanoparticles. While simple static type fluorescence quenching mechanism was perceived with AuNP, a more complex protocol involving quenching sphere model was envisaged for AgNP quenching. Nevertheless, the magnitude of Stern-Volmer (SV) quenching constant (K_SV ~ 10⁸-10¹⁰ M^-1) was calculated to be ca. 10⁴ times more for surface quoted NPs in comparison with BSA-NP bioconjugates system. On the other hand, a highly efficient (E ≈ 95%) energy transfer (ET) process was predicted for LH₂ captured in the hydrophobic assembly with BSA in presence of AgNP as an acceptor. The ET efficiency is critically dependent on the concentration of BSA and nicely correlated with the extent of NP surface coverage. However, fluorescence quenching on AuNP surface is relatively less responsive towards protein concentration, primarily due to the difference in surface activity as well as the mode of interaction of the protein with NPs. Graphical Abstract Energy transfer from excited luminol to metal nanoparticles is strongly modulated in presence of serum albumins.

In Situ Detection of Plasma Exosomal MicroRNA-1246 for Breast Cancer Diagnostics by a Au Nanoflare Probe

Breast cancer is the second cause of cancer mortality in women globally. Early detection, treatment, and metastasis monitoring are of great importance to favorable prognosis. Although conventional diagnostic methods, such as breast X-ray mammography and image positioning biopsy, are accurate, they could cause radioactive or invasive damage to patients. Liquid biopsy as a noninvasive method is convenient for repeated sampling in clinical cancer prognostic, metastatic evaluation, and relapse monitoring. MicroRNAs encased in exosomes circulating in biofluids are promising candidate cancer biomarkers because of their cancer-specific expression profiles. Here, we report an in situ detection of microRNA-1246 (miR-1246) in human plasma exosomes as breast cancer biomarker by a nucleic acid functionalized Au nanoflare probe. Needing neither time-consuming and costly isolation of exosomes from the plasma sample nor transfection means, the Au nanoflare probe can directly enter the plasma exosomes to generate fluorescent signal quantitatively by specifically targeting miR-1246. Only 40 μL of plasma is needed to incubate 4 h with the probe, giving signal sensitive enough to distinguish samples of breast cancer to normal control. Using plasma miR-1246 level detected by our assay as a marker, we differentiated 46 breast cancer patients from 28 healthy controls with 100% sensitivity and 92.9% specificity at the best cutoff. This simple, accurate, sensitive, and cost-effective liquid biopsy by the Au nanoflare probe is potent to be developed as a noninvasive breast cancer diagnostic assay for clinical adaption.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Amine-functionalized diatom frustules: a platform for specific and sensitive detection of nitroaromatic explosive derivative

In the present study, an attempt was made to develop a proof of concept for the detection of nitroaromatic explosive derivatives through the photoluminescence (PL) quenching process using functionalized diatom frustules as a sensing platform. The diatom frustules are composed of nanostructured, highly porous biogenic silica material and emit strong, visible blue PL upon UV excitation. PL-active biosilica was isolated from the marine diatom Nitzschia sp. and was amine-functionalized to develop a sensing platform. Functionalized diatom frustules were further characterized using field emission scanning electron microscope and a series of spectroscopic methods. When nitroaromatic compounds were bound to the functionalized diatom frustules biosilica, the PL intensity from the functionalized biosilica was partially quenched due to the electrophilic nature of the nitro (-NO) groups. The quenching process confirmed the Meisenheimer complex formation and was investigated by using Fourier transform infrared spectroscopy and time-resolved photoluminescence studies. The developed platform was further evaluated for its sensitivity and specificity, and the limit of detection (LOD) of the assay was determined as 1 μM for a series of nitroaromatic explosive compounds. In conclusion, the developed sensing platform will have great utility in the development of on-site detection platforms for sensitive detection of warfare explosive nitroaromatic compounds from the environment.

Diagnosing human blood clotting deficiency

There are different clotting factors present in blood, carries the clotting cascade and excessive bleeding may cause a deficiency in the clotting Diagnosis of this deficiency in clotting drastically reduces the potential fatality. For enabling a sensor to detect the clotting factors, suitable probes such as antibody and aptamer have been used to capture these targets on the sensing surface. Two major clotting factors were widely studied for the diagnosis of clotting deficiency, which includes factor IX and thrombin. In addition, factor IX is considered as the substitute for heparin and the prothrombotic associated with the increased thrombin generation are taking into account their prevalence. The biosensors, surface plasmon resonance, evanescent-field-coupled waveguide-mode sensor, metal-enhanced PicoGreen fluorescence and electrochemical aptasensor were well-documented and improvements have been made for high-performance sensing. We overviewed detecting factor IX and thrombin using these biosensors, for the potential application in medical diagnosis.

A review on microscale polymerase chain reaction based methods in molecular diagnosis, and future prospects for the fabrication of fully integrated portable biomedical devices

Since the advent of microfabrication technology and soft lithography, the lab-on-a-chip concept has emerged as a state-of-the-art miniaturized tool for conducting the multiple functions associated with micro total analyses of nucleic acids, in series, in a seamless manner with a miniscule volume of sample. The enhanced surface-to-volume ratio inside a microchannel enables fast reactions owing to increased heat dissipation, allowing rapid amplification. For this reason, PCR has been one of the first applications to be miniaturized in a portable format. However, the nature of the basic working principle for microscale PCR, such as the complicated temperature controls and use of a thermal cycler, has hindered its total integration with other components into a micro total analyses systems (μTAS). This review (with 179 references) surveys the diverse forms of PCR microdevices constructed on the basis of different working principles and evaluates their performances. The first two main sections cover the state-of-the-art in chamber-type PCR microdevices and in continuous-flow PCR microdevices. Methods are then discussed that lead to microdevices with upstream sample purification and downstream detection schemes, with a particular focus on rapid on-site detection of foodborne pathogens. Next, the potential for miniaturizing and automating heaters and pumps is examined. The review concludes with sections on aspects of complete functional integration in conjunction with nanomaterial based sensing, a discussion on future prospects, and with conclusions. Graphical abstract In recent years, thermocycler-based PCR systems have been miniaturized to palm-sized, disposable polymer platforms. In addition, operational accessories such as heaters and mechanical pumps have been simplified to realize semi-automatted stand-alone portable biomedical diagnostic microdevices that are directly applicable in the field. This review summarizes the progress made and the current state of this field.

Recent advances in ambient mass spectrometry of trace explosives

Ambient mass spectrometry has evolved rapidly over the past decade, yielding a plethora of platforms and demonstrating scientific advancements across a range of fields from biological imaging to rapid quality control. These techniques have enabled real-time detection of target analytes in an open environment with no sample preparation and can be coupled to any mass analyzer with an atmospheric pressure interface; capabilities of clear interest to the defense, customs and border control, transportation security, and forensic science communities. This review aims to showcase and critically discuss advances in ambient mass spectrometry for the trace detection of explosives.

Noble metal nanostructures in optical biosensors: Basics, and their introduction to anti-doping detection

Nanotechnology has illustrated significant potentials in biomolecular-sensing applications; particularly its introduction to anti-doping detection is of great importance. Illicit recreational drugs, substances that can be potentially abused, and drugs with dosage limitations according to the prohibited lists announced by the World Antidoping Agency (WADA) are becoming of increasing interest to forensic chemists. In this review, the theoretical principles of optical biosensors based on noble metal nanoparticles, and the transduction mechanism of commonly-applied plasmonic biosensors are covered. We review different classes of recently-developed plasmonic biosensors for analytic determination and quantification of illicit drugs in anti-doping applications. The important classes of illicit drugs include anabolic steroids, opioids, stimulants, and peptide hormones. The main emphasis is on the advantages that noble metal nano-particles bring to optical biosensors for signal enhancement and the development of highly sensitive (label-free) biosensors. In the near future, such optical biosensors may be an invaluable substitute for conventional anti-doping detection methods such as chromatography-based approaches, and may even be commercialized for routine anti-doping tests.

Ligand exchange reactions on citrate-gold nanoparticles for a parallel colorimetric assay of six pesticides

A rapid parallel colorimetric method was developed for identification of six pesticides (acephate, phenthoate, profenofos, acetamiprid, chlorothalonil and cartap) via ligand exchange reactions on citrate-gold nanoparticles.

Investigations on the elasticity of functional gold nanoparticles using single-molecule force spectroscopy

In this focused review we turn our attention towards several approaches for detecting the elasticity of NPs, systematically summarizing the divergent elasticity values of distinct gold nanoparticles (AuNPs) with different surfaces.

Lipid-Coated Gold Nanoparticles and FRET Allow Sensitive Monitoring of Liposome Clustering Mediated by the Synaptotagmin-7 C2A Domain

Synaptotagmin (Syt) family proteins contain tandem C2 domains, C2A and C2B, which insert into anionic membranes in response to increased cytosolic Ca²⁺ concentration and facilitate exocytosis in neuronal and endocrine cells. The C2A domain from Syt7 binds lipid membranes much more tightly than the corresponding domain from Syt1, but the implications of this difference for protein function are not yet clear. In particular, the ability of the isolated Syt7 C2A domain to initiate membrane apposition and/or aggregation has been previously unexplored. Here, we demonstrate that Syt7 C2A induces apposition and aggregation of liposomes using Förster resonance energy transfer (FRET) assays, dynamic light scattering, and spectroscopic techniques involving lipid-coated gold nanoparticles (LCAuNPs). Protein-membrane binding, membrane apposition, and macroscopic aggregation are three separate phenomena with distinct Ca²⁺ requirements: the threshold Ca²⁺ concentration for membrane binding is lowest, followed by apposition and aggregation. However, aggregation is highly sensitive to protein concentration and can occur even at submicromolar Syt7 C2A; thus, highly sensitive assays are needed for measuring apposition without complications arising from aggregation. Notably, the localized surface plasmon resonance of the LCAuNP is sensitive to ≤10 nM Syt7 C2A concentrations. Furthermore, when the LCAuNPs were added into a FRET-based liposome apposition assay, the resultant energy transfer increased; possible explanations are discussed. Overall, LCAuNP-based methods allow for highly sensitive detection of protein-induced membrane apposition under conditions that miminize large-scale aggregation.

Detection of Pesticide Residues in Food Using Surface-Enhanced Raman Spectroscopy: A Review

Pesticides directly pollute the environment and contaminate foods ultimately being absorbed by the human body. Their residues contain highly toxic substances that have been found to cause serious problems to human health even at very low concentrations. The gold standard method, gas/liquid chromatography combined with mass spectroscopy, has been widely used for the detection of pesticide residues. However, these methods have some drawbacks such as complicated pretreatment and cleanup steps. Recent technological advancements of surface-enhanced Raman spectroscopy (SERS) have promoted the creation of alternative detection techniques. SERS is a useful detection tool with ultrasensitivity and simpler protocols. Present SERS-based pesticide residue detection often uses standard solutions of target analytes in conjunction with theoretical Raman spectra calculated by density functional theory (DFT) and actual Raman spectra detected by SERS. SERS is quite a promising technique for the direct detection of pesticides at trace levels in liquid samples or on the surface of solid samples following simple extraction to increase the concentration of analytes. In this review, we highlight recent studies on SERS-based pesticide detection, including SERS for pesticide standard solution detection and for pesticides in/on food samples. Moreover, in-depth analysis of pesticide chemical structures, structural alteration during food processing, interaction with SERS substrates, and selection of SERS-active substrates is involved.

Enhanced aerodynamic reach of vapor and aerosol sampling for real-time mass spectrometric detection using Venturi-assisted entrainment and ionization

Venturi-assisted ENTrainment and Ionization (VENTI) was developed, demonstrating efficient entrainment, collection, and transport of remotely sampled vapors, aerosols, and dust particulate for real-time mass spectrometry (MS) detection. Integrating the Venturi and Coandă effects at multiple locations generated flow and analyte transport from non-proximate locations and more importantly enhanced the aerodynamic reach at the point of collection. Transport through remote sampling probes up to 2.5 m in length was achieved with residence times on the order of 10^-2 s to 10^-1 s and Reynolds numbers on the order of 10³ to 10⁴. The Venturi-assisted entrainment successfully enhanced vapor collection and detection by greater than an order of magnitude at 20 cm stand-off (limit of simple suction). This enhancement is imperative, as simple suction restricts sampling to the immediate vicinity, requiring close proximity to the vapor source. In addition, the overall aerodynamic reach distance was increased by approximately 3-fold over simple suction under the investigated conditions. Enhanced aerodynamic reach was corroborated and observed with laser-light sheet flow visualization and schlieren imaging. Coupled with atmospheric pressure chemical ionization (APCI), the detection of a range of volatile chemical vapors; explosive vapors; explosive, narcotic, and mustard gas surrogate (methyl salicylate) aerosols; and explosive dust particulate was demonstrated. Continuous real-time Venturi-assisted monitoring of a large room (approximately 90 m² area, 570 m³ volume) was demonstrated for a 60-min period without the remote sampling probe, exhibiting detection of chemical vapors and methyl salicylate at approximately 3 m stand-off distances within 2 min of exposure.