Optical microchip array biosensor for multiplexed detection of bio-hazardous agents

Challenges and perspectives of multi-virus biosensing techniques: A review

In the context of globalization, individuals have an increased chance of being infected by multiple viruses simultaneously, thereby highlighting the importance of developing multiplexed devices. In addition to sufficient sensitivity and rapid response, multi-virus sensing techniques are expected to offer additional advantages including high throughput, one-time sampling for parallel analysis, and full automation with data visualization. In this paper, we review the optical, electrochemical, and mechanical platforms that enable multi-virus biosensing. The working mechanisms of each platform, including the detection principle, transducer configuration, bio-interface design, and detected signals, are reviewed. The advantages and limitations, as well as the challenges in implementing various detection strategies in real-life scenarios, were evaluated. Future perspectives on multiplexed biosensing techniques are critically discussed. Earlier access to multi-virus biosensors will efficiently serve for immediate pandemic control, such as in emerging SARS-CoV-2 and monkeypox cases.

Prussian Blue Sensor for Bacteria Detection in Personal Protection Clothing

Biological hazards can be defined as substances that endanger the life of any living organism, most notably humans, and are often referred to as biohazards. Along with the use of personal protective equipment (PPE), early detection of contact is essential for the correct management and resolution of a biological threat, as well as lower mortality rates of those exposed. Herein, Prussian blue (PB) was evaluated as a functional compound applied on polyester knits to act as an on-site sensor for bacteria detection. In order to study the best compound concentration for the intended application, polymeric solutions of 0.5, 1 and 2 g/L were developed. The three conditions tested displayed high abrasion resistance (>2000 cycles). The bacterial sensing capacity of the coated knits was assessed in liquid and solid medium, with the functionalised substrates exhibiting the capability of detecting both Gram-positive and Gram-negative bacteria and changing colours from blue to white. Evaluation of water repellence and chemical penetration resistance and repellence was also performed in polyester functionalised with PB 0.5 and 1 g/L. Both knits showed a hydrophobic behaviour and a capacity to resist to penetration of chemicals and level 3 repellence effect for both acid and base chemicals.

Multiplex Biosensing for Simultaneous Detection of Mutations in SARS-CoV-2

COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) has become the world's largest public health emergency of the past few decades. Thousands of mutations were identified in the SARS-CoV-2 genome. Some mutants are more infectious and may replace the original strains. Recently, B.1.1.7(Alpha), B1.351(Beta), and B.1.617.2(Delta) strains, which appear to have increased transmissibility, were detected. These strains accounting for the high proportion of newly diagnosed cases spread rapidly over the world. Particularly, the Delta variant has been reported to account for a vast majority of the infections in several countries over the last few weeks. The application of biosensors in the detection of SARS-CoV-2 is important for the control of the COVID-19 pandemic. Due to high demand for SARS-CoV-2 genotyping, it is urgent to develop reliable and efficient systems based on integrated multiple biosensor technology for rapid detection of multiple SARS-CoV-2 mutations simultaneously. This is important not only for the detection and analysis of the current but also for future mutations. Novel biosensors combined with other technologies can be used for the reliable and effective detection of SARS-CoV-2 mutants.

Deep UV Formation of Long-Term Stable Optical Bragg Gratings in Epoxy Waveguides and Their Biomedical Sensing Potentials

In this article, we summarize our investigations on optimized 248 nm deep ultraviolet (UV) fabrication of highly stable epoxy polymer Bragg grating sensors and their application for biomedical purposes. Employing m-line spectroscopy, deep UV photosensitivity of cross-linked EpoCore thin films in terms of responding refractive index change is determined to a maximum of Δn = + (1.8 ± 0.2) × 10⁻³. All-polymer waveguide Bragg gratings are fabricated by direct laser irradiation of lithographic EpoCore strip waveguides on compatible Topas 6017 substrates through standard +1/-1-order phase masks. According near-field simulations of realistic non-ideal phase masks provide insight into UV dose-dependent characteristics of the Bragg grating formation. By means of online monitoring, arising Bragg reflections during grating inscription via beforehand fiber-coupled waveguide samples, an optimum laser parameter set for well-detectable sensor reflection peaks in respect of peak strength, full width at half maximum and grating attenuation are derived. Promising blood analysis applications of optimized epoxy-based Bragg grating sensors are demonstrated in terms of bulk refractive index sensing of whole blood and selective surface refractive index sensing of human serum albumin.

On-Chip Optical Detection of Viruses: A Review

The current outbreak of the coronavirus disease-19 (COVID-19) pandemic worldwide has caused millions of fatalities and imposed a severe impact on our daily lives. Thus, the global healthcare system urgently calls for rapid, affordable, and reliable detection toolkits. Although the gold-standard nucleic acid amplification tests have been widely accepted and utilized, they are time-consuming and labor-intensive, which exceedingly hinder the mass detection in low-income populations, especially in developing countries. Recently, due to the blooming development of photonics, various optical chips have been developed to detect single viruses with the advantages of fast, label-free, affordable, and point of care deployment. Herein, optical approaches especially in three perspectives, e.g., flow-free optical methods, optofluidics, and surface-modification-assisted approaches, are summarized. The future development of on-chip optical-detection methods in the wave of emerging new ideas in nanophotonics is also briefly discussed.

Current Trends in the Biosensors for Biological Warfare Agents Assay

Biosensors are analytical devices combining a physical sensor with a part of biological origin providing sensitivity and selectivity toward analyte. Biological warfare agents are infectious microorganisms or toxins with the capability to harm or kill humans. They can be produced and spread by a military or misused by a terrorist group. For example, Bacillus anthracis, Francisella tularensis, Brucella sp., Yersinia pestis, staphylococcal enterotoxin B, botulinum toxin and orthopoxviruses are typical biological warfare agents. Biosensors for biological warfare agents serve as simple but reliable analytical tools for the both field and laboratory assay. There are examples of commercially available biosensors, but research and development of new types continue and their application in praxis can be expected in the future. This review summarizes the facts and role of biosensors in the biological warfare agents' assay, and shows current commercially available devices and trends in research of the news. Survey of actual literature is provided.

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.

Evanescent field refractometry in planar optical fiber

This Letter demonstrates a refractometer in integrated optical fiber, a new optical platform that planarizes fiber using flame hydrolysis deposition (FHD). The unique advantage of the technology is survivability in harsh environments. The platform is mechanically robust, and can survive elevated temperatures approaching 1000°C and exposure to common solvents, including acetone, gasoline, and methanol. For the demonstrated refractometer, fabrication was achieved through wet etching an SMF-28 fiber to a diameter of 8 μm before FHD planarization. An external refractive index was monitored using fiber Bragg gratings (FBGs), written into the core of the planarized fiber. A direct comparison to alternative FBG refractometers is made, for which the developed platform is shown to have comparable sensitivity, with the added advantage of survivability in harsh environments.

Surface functionalization allowing repetitive use of optical sensors for real-time detection of antibody-bacteria interaction

In this study, sensor surface functionalization allowing the repetitive use of a sensing device was evaluated for antibody-based detection of living bacteria using an optical planar Bragg grating sensor. To achieve regenerable immobilization of bacteria specific antibodies, the heterobifunctional cross-linker N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) was linked to an aminosilanized sensor surface and subsequently reduced to expose sulfhydryl groups enabling the covalent conjugation of SPDP-activated antibodies via disulfide bonds. The immobilization of a capture antibody specific for Staphylococcus aureus on the sensor surface as well as specific binding of S. aureus could be monitored, highlighting the applicability of optical sensors for the specific detection of large biological structures. Reusability of bacteria saturated sensors was successfully demonstrated by cleaving the antibody along with bound bacteria through reduction of disulfide bonds and subsequent re-functionalization with activated antibody, resulting in comparable sensitivity towards S. aureus.

Analytical solution for transient electroosmotic flow in a rotating microchannel

An analytical solution is developed for the unsteady flow of fluid through a parallel rotating plate microchannel, under the influence of electrokinetic force using the Debye–Hückel (DH) approximation.

Point-of-care diagnostics for ricin exposure

A long-sought milestone in the defense against bioterrorism is the development of rapid, simple, and near-patient assays for diagnostic and theranostic purposes. Here, we present a powerful test based on a host response to a biological weapon agent, namely the ricin toxin. A signature for exposure to ricin was extracted and characterized in mice and then integrated into a plastic microfluidic cartridge. This enabled early diagnosis of exposure to ricin in mice using a drop of whole blood in less than 1 h and 30 min. The cartridge stores the reagents and implements all of the steps of the analysis, including mRNA extraction from a drop of blood, followed by tens of parallel RT-qPCR reactions. The simple and low-cost microfluidic cartridge developed here may find other applications in point-of-care diagnostics.

Real-time and label-free analyte detection in a flow-through mode using immobilized fluorescent aptamer/quantum dots molecular switches

Inspired by the goal to create a biosensor with designer specificity for real-time detection of unlabeled analytes in a flow-through mode, we designed a miniature flow cell with interchangeable quartz window carrying immobilized aptamer/quantum dot molecular switches as a part of a portable fluorescent setup. The inner surface of the 1.5mm ID, 12µl flow cell quartz window has been modified with the aptamer sensing complexes containing highly-fluorescent quantum dots. The aptamer complexes were designed as molecular switches to undergo conformational change and release fluorescent label upon interaction with the flow of the analyte, causing fluorescence decrease. The specificity of the sensor was designed to address the light chain of Botulinum Neurotoxin A and Ricin Toxin A chain, which could be specifically and repeatedly detected in the flow of 60µl/min with sensitivity comparable to other real-time detection methods. The specifics of quantum dots use as fluorescent labels for continuous monitoring under constant UV illumination were outlined. The possibility for multispecific sensing was explored by testing of bi-specific sensor. This work shows the possibility of surface-bound aptamer sensing for flow-through analyte detection and provides a useful tool to perform surface fluorescent studies in real-time. The flexibility of the described design allows for sensor specificity change through altering the specificity of the aptamer. Future work should address response quantification. The described sensing approach can be adapted to a number of environmental or clinical targets.

A critical review of anaesthetised animal models and alternatives for military research, testing and training, with a focus on blast damage, haemorrhage and resuscitation

Military research, testing, and surgical and resuscitation training, are aimed at mitigating the consequences of warfare and terrorism to armed forces and civilians. Traumatisation and tissue damage due to explosions, and acute loss of blood due to haemorrhage, remain crucial, potentially preventable, causes of battlefield casualties and mortalities. There is also the additional threat from inhalation of chemical and aerosolised biological weapons. The use of anaesthetised animal models, and their respective replacement alternatives, for military purposes -- particularly for blast injury, haemorrhaging and resuscitation training -- is critically reviewed. Scientific problems with the animal models include the use of crude, uncontrolled and non-standardised methods for traumatisation, an inability to model all key trauma mechanisms, and complex modulating effects of general anaesthesia on target organ physiology. Such effects depend on the anaesthetic and influence the cardiovascular system, respiration, breathing, cerebral haemodynamics, neuroprotection, and the integrity of the blood-brain barrier. Some anaesthetics also bind to the NMDA brain receptor with possible differential consequences in control and anaesthetised animals. There is also some evidence for gender-specific effects. Despite the fact that these issues are widely known, there is little published information on their potential, at best, to complicate data interpretation and, at worst, to invalidate animal models. There is also a paucity of detail on the anaesthesiology used in studies, and this can hinder correct data evaluation. Welfare issues relate mainly to the possibility of acute pain as a side-effect of traumatisation in recovered animals. Moreover, there is the increased potential for animals to suffer when anaesthesia is temporary, and the procedures invasive. These dilemmas can be addressed, however, as a diverse range of replacement approaches exist, including computer and mathematical dynamic modelling of the human body, cadavers, interactive human patient simulators for training, in vitro techniques involving organotypic cultures of target organs, and epidemiological and clinical studies. While the first four of these have long proven useful for developing protective measures and predicting the consequences of trauma, and although many phenomena and their sequelae arising from different forms of trauma in vivo can be induced and reproduced in vitro, non-animal approaches require further development, and their validation and use need to be coordinated and harmonised. Recommendations to these ends are proposed, and the scientific and welfare problems associated with animal models are addressed, with the future focus being on the use of batteries of complementary replacement methods deployed in integrated strategies, and on greater transparency and scientific cooperation.

Quantitative and sensitive RNA based detection of Bacillus spores

The fast and reliable detection of bacterial spores is of great importance and still remains a challenge. Here we describe a direct RNA-based diagnostic method for the specific detection of viable bacterial spores which does not depends on an enzymatic amplification step and therefore is directly appropriate for quantification. The procedure includes the following steps: (i) heat activation of spores, (ii) germination and enrichment cultivation, (iii) cell lysis, and (iv) analysis of 16S rRNA in crude cell lysates using a sandwich hybridization assay. The sensitivity of the method is dependent on the cultivation time and the detection limit; it is possible to detect 10 spores per ml when the RNA analysis is performed after 6 h of enrichment cultivation. At spore concentrations above 10(6) spores per ml the cultivation time can be shortened to 30 min. Total analysis times are in the range of 2-8 h depending on the spore concentration in samples. The developed procedure is optimized at the example of Bacillus subtilis spores but should be applicable to other organisms. The new method can easily be modified for other target RNAs and is suitable for specific detection of spores from known groups of organisms.

Dip biosensor based on localized surface plasmon resonance at the tip of an optical fiber

A dip biosensor is realized by depositing metallic nanoparticles onto the tip of a cleaved optical fiber. Light coupled into the fiber interacts with the localized surface plasmons within the nanoparticles at the tip; a portion of the scattered light recouples into the optical fiber and is analyzed by a spectrometer. Characterization of the sensor demonstrates an inverse relationship between the sensitivity and the number of particles deposited onto the surface, with smaller quantities leading to greater sensitivity. The results obtained showed also that by depositing nanoparticles with distinct localized surface plasmon resonance signatures with limited overlap, as for the case of gold and silver nanospheres, a multiplexed dip biosensor can be realized by simply functionalizing the different nanoparticles with different antibodies after the fashion of an immunoassay. In this way different localized surface plasmons resonance bands responsive to different target analytes can be separately monitored, as further presented below, requiring a minimal quantity of reagents both for the functionalization process and for the sample analysis.

Single domain antibodies for the detection of ricin using silicon photonic microring resonator arrays

Ricin is a lethal protein toxin derived from the castor bean plant. Given its notorious history as a biowarfare agent and homicidal weapon, ricin has been classified as a category B bioterrorism agent. Current ricin detection methods based on immunoassays lack the required sensitivity and specificity for many homeland security surveillance applications. Importantly, many conventional antibody-based methodologies are unable to distinguish ricin from RCA 120, a nontoxic protein also found in the castor bean plant. Single domain antibodies (sdAbs), which are recombinantly derived from immunized llamas, are known to have high affinities for ricin A or B chains and low cross-reactivity with RCA 120. Herein, we demonstrate the use of silicon photonic microring resonators for antibody affinity profiling and one-step ricin detection at concentrations down to 300 pM using a 15 min, label-free assay format. These sdAbs were also simultaneously compared with a commercial anti-RCA IgG antibody in a multicapture agent, single target immunoassay using arrays of microrings, which allowed direct comparison of sensitivity and specificity. A selected sdAb was also found to exhibit outstanding specificity against another biotoxin, saporin, which has mechanism of action similar to ricin. Given the rapidity, scalability, and multiplexing capability of this silicon-based technology, this work represents a step toward using microring resonator arrays for the sensitive and specific detection of biowarfare agents.

Microfluidic chips with reversed-phase monoliths for solid phase extraction and on-chip labeling

The integration of sample preparation methods into microfluidic devices provides automation necessary for achieving complete micro total analysis systems. We have developed a technique that combines on-chip sample enrichment with fluorescence labeling and purification. Polymer monoliths made from butyl methacrylate were fabricated in cyclic olefin copolymer microdevices and used for solid phase extraction. We studied the retention of fluorophores, amino acids and proteins on these columns. The retained samples were subsequently labeled with both Alexa Fluor 488 and Chromeo P503, and unreacted dye was rinsed off the column before sample elution. Additional purification was obtained from the differential retention of proteins and fluorescent labels. A linear relation between the eluted peak areas and concentrations of on-chip labeled heat shock protein 90 samples demonstrated the utility of this method for on-chip quantitation. Our fast and simple method of simultaneously concentrating and labeling samples on-chip is compatible with miniaturization and desirable for automated analysis.

A rapid label-free method for quantitation of human immunodeficiency virus type-1 particles by nanospectroscopy

Infection of cells with human immunodeficiency virus type-1 (HIV-1) results in the production of both infectious and non-infectious virions. At present, several assays are available for the quantitation of virus particles based on the presence of either viral capsid protein or nucleic acid. However, the ability to detect the total number of virus particles, both infectious and non-infectious, has been an elusive goal that would advance the study of virus assembly and egress. A rapid optical detection scheme for real-time label-free quantitation of HIV-1 virus particles was developed. Virions produced in cell cultures transfected transiently were evaluated with a nanospectroscopic assay. Quantitation with the optical detection scheme correlated with routine conventional assays. Nanospectroscopy can be used for the detection of both infectious and non-infectious, wild type and mutant strains of HIV-1 in solution at concentrations as low as 7×10(10)particles/ml, requiring volumes as small as 2 μl per assay, and in significantly less time than standard techniques. This assay provides a rapid, reliable system for quantifying virus particles in solution and could be applied to the study of viral particle production in cell culture.

Recent advances in multiplex immunoassays

The present review reports on the lastest developments in multiplex immunoassays. The selected examples are classified through their detection strategy (fluorescence, chemiluminescence, colorimetry or labeless) and their assay format (standard microtiter plate, polymeric membranes and glass slides). Finally, the degree of integration in a complete system, incorporating fluid handling and detection was also taken into account.