Detection of Extremely Low Concentrations of Biological Substances Using Near-Field Illumination

Improvement of Sensitivity and Speed of Virus Sensing Technologies Using nm- and μm-Scale Components

Various viral diseases can be widespread and cause severe disruption to global society. Highly sensitive virus detection methods are needed to take effective measures to prevent the spread of viral infection. This required the development of rapid virus detection technology to detect viruses at low concentrations, even in the biological fluid of patients in the early stages of the disease or environmental samples. This review describes an overview of various virus detection technologies and then refers to typical technologies such as beads-based assay, digital assay, and pore-based sensing, which are the three modern approaches to improve the performance of viral sensing in terms of speed and sensitivity.

Nanodiagnostics: A review of the medical capabilities of nanopores

Modern diagnostics strive to be accurate, fast, and inexpensive in addition to properly identifying the presence of a disease, infection, or illness. Early diagnosis is key; catching a disease in its early stages can be the difference between fatality and treatment. The challenge with many diseases is that detectability of the disease scales with disease progression. Since single molecule sensors, e.g., nanopores, can sense biomolecules at low concentrations, they have the potential to become clinically relevant in many of today's medical settings. With nanopore-based sensing, lower volumes and concentrations are required for detection, enabling it to be clinically beneficial. Other advantages to using nanopores include that they are tunable to an enormous variety of molecules and boast low costs, and fabrication is scalable for manufacturing. We discuss previous reports and the potential for incorporating nanopores into the medical field for early diagnostics, therapeutic monitoring, and identifying relapse/recurrence.

A Survey of Analytical Techniques for Noroviruses

As the leading cause of acute gastroenteritis worldwide, human noroviruses (HuNoVs) have caused around 685 million cases of infection and nearly $60 billion in losses every year. Despite their highly contagious nature, an effective vaccine for HuNoVs has yet to become commercially available. Therefore, rapid detection and subtyping of noroviruses is crucial for preventing viral spread. Over the past half century, there has been monumental progress in the development of techniques for the detection and analysis of noroviruses. However, currently no rapid, portable assays are available to detect and subtype infectious HuNoVs. The purpose of this review is to survey and present different analytical techniques for the detection and characterization of noroviruses.

Immunosensor Based on Long-Period Fiber Gratings for Detection of Viruses Causing Gastroenteritis

Since the norovirus is the main cause of acute gastroenteritis all over the world, its fast detection is crucial in medical diagnostics. In this work, a rapid, sensitive, and selective optical fiber biosensor for the detection of norovirus virus-like particles (VLPs) is reported. The sensor is based on highly sensitive long-period fiber gratings (LPFGs) coated with antibodies against the main coat protein of the norovirus. Several modification methods were verified to obtain reliable immobilization of protein receptors on the LPFG surface. We were able to detect 1 ng/mL norovirus VLPs in a 40-min assay in a label-free manner. Thanks to the application of an optical fiber as the sensor, there is a possibility to increase the user’s safety by separating the measurement point from the signal processing setup. Moreover, our sensor is small and light, and the proposed assay is straightforward. The designed LPFG-based biosensor could be applied in both fast norovirus detection and in vaccine testing.

A Novel Diagnostic System for Infectious Diseases Using Solid-State Nanopore Devices

Nanopore-based diagnostic systems are a promising tool for counting viruses in a specimen one by one. However, despite intensive R&D efforts, it remains difficult to recognize virus subtypes by nanopore devices. We thus propose a novel diagnostic system that combines a specialized virus recognition procedure with a nanopore detection procedure. This recognition procedure consists of three steps: 1) capture target viruses using specific probes for recognition; 2) release captured targets; and 3) detect released targets by nanopore. Proof-of-concept tests are conducted using avidin-modified fluorescent particles (as a model for viruses) and biotin-modified alkane thiol (as a model for probes). The avidin-modified particles are confirmed to be captured on electrode by biotin-modified probes and then, the particles are electrochemically released from the electrode. Consequently, the released particles are successfully detected by nanopore devices. Furthermore, the concept is also proved by using human influenza viruses (H1N1, A/PR/8/34) and sugar chain (6'-sialyllactose)-modified probes. This suggests that our concept is applicable to various infectious diseases by changing probes (ligands).

The Antigenic Topology of Norovirus as Defined by B and T Cell Epitope Mapping: Implications for Universal Vaccines and Therapeutics

Human norovirus (HuNoV) is the leading cause of acute nonbacterial gastroenteritis. Vaccine design has been confounded by the antigenic diversity of these viruses and a limited understanding of protective immunity. We reviewed 77 articles published since 1988 describing the isolation, function, and mapping of 307 unique monoclonal antibodies directed against B cell epitopes of human and murine noroviruses representing diverse Genogroups (G). Of these antibodies, 91, 153, 21, and 42 were reported as GI-specific, GII-specific, MNV GV-specific, and G cross-reactive, respectively. Our goal was to reconstruct the antigenic topology of noroviruses in relationship to mapped epitopes with potential for therapeutic use or inclusion in universal vaccines. Furthermore, we reviewed seven published studies of norovirus T cell epitopes that identified 18 unique peptide sequences with CD4- or CD8-stimulating activity. Both the protruding (P) and shell (S) domains of the major capsid protein VP1 contained B and T cell epitopes, with the majority of neutralizing and HBGA-blocking B cell epitopes mapping in or proximal to the surface-exposed P2 region of the P domain. The majority of broadly reactive B and T cell epitopes mapped to the S and P1 arm of the P domain. Taken together, this atlas of mapped B and T cell epitopes offers insight into the promises and challenges of designing universal vaccines and immunotherapy for the noroviruses.

Optimization of a waveguide-mode sensing chip for an ultraviolet near-field illumination biosensor

A waveguide-mode sensor with a planar sensing chip, consisting of two waveguiding layers and a glass substrate, is a promising candidate for a near-field illumination biosensor. Aiming at using fluorescent labeling induced by ultraviolet light, we optimize the structure of a waveguide-mode sensing chip, based on the mechanism for enhancing ultraviolet near-field light revealed by numerical calculations. Candidates of optimal materials are also presented. The chip optimized as above should be able to enhance the intensity of ultraviolet near-field light 25 times as high as an Al surface plasmon resonance sensing chip.

Multi-Normalization and Interpolation Protocol to Improve Norovirus Immunoagglutination Assay from Paper Microfluidics with Smartphone Detection

Norovirus (NoV) is one of the leading causes of acute gastroenteritis, affecting 685 million people per year around the world. The best preventive measure is to screen water for possible NoV contamination, not from infected humans, preferably using rapid and field-deployable diagnostic methods. While enzyme immunoassays (EIAs) can be used for such detection, the low infectious dose as well as the generally inferior sensitivity and low titer of available NoV antibodies render critical challenges in using EIAs toward NoV detection. In this work, we demonstrated smartphone-based Mie scatter detection of NoV with immunoagglutinated latex particles on paper microfluidic chips. Using only three different concentrations of anti-NoV-conjugated particles, we were able to construct a single standard curve that covered seven orders of magnitude of NoV antigen concentrations. Multiple normalization steps and interpolation procedures were developed to estimate the optimum amount of antibody-conjugated particles that matched to the target NoV concentration. A very low detection limit of 10 pg/mL was achieved without using any concentration or enrichment steps. This method can also be adapted for detection of any other virus pathogens whose antibodies possess low sensitivity and low antibody titer.

Recent Advances in Biosensor Development for Foodborne Virus Detection

Outbreaks of foodborne diseases related to fresh produce have been increasing in North America and Europe. Viral foodborne pathogens are poorly understood, suffering from insufficient awareness and surveillance due to the limits on knowledge, availability, and costs of related technologies and devices. Current foodborne viruses are emphasized and newly emerging foodborne viruses are beginning to attract interest. To face current challenges regarding foodborne pathogens, a point-of-care (POC) concept has been introduced to food testing technology and device. POC device development involves technologies such as microfluidics, nanomaterials, biosensors and other advanced techniques. These advanced technologies, together with the challenges in developing foodborne virus detection assays and devices, are described and analysed in this critical review. Advanced technologies provide a path forward for foodborne virus detection, but more research and development will be needed to provide the level of manufacturing capacity required.