Smart and Functional Interfaces for Sensitive SPR Biosensing Towards Biomedical Applications

The aim of this thesis is to develop Surface Plasmon Resonance (SPR) methods that improve biosensing performance, in particular the sensitivity and selectivity of the analysis and their adaptation for biomedical applications to samples with complex background. This is of significant importance in translating the biosensor technologies to deliver the same results as the conventional methods but in a more accessible, efficient, and economical manner. The first study exploited SPR as a DNA biosensor for the detection of Malaria Plasmodium falciparum parasite with the hybridization chain reaction (HCR), which resulted in the formation of self-assembled target DNA nanostructures for signal enhancement. The sensitivity was further improved by using gold nanoparticles (AuNPs) for additional signal amplification. Tests with human blood plasma indicated the results were comparable to analyses in buffer, despite noticeable non-specific binding from the plasma. The concern of non-specific binding was systematically investigated in the second study where an antifouling surface consists of supported lipid bilayer membranes (SLBs) and protein A was developed for detection of trace amount of proteins in undiluted human serum. Specifically, cholera toxin (CT) spiked into the serum was used as the target, and advanced interface was further extended to immunosensing of immunoglobulin G (IgG). In the third study, SPR biosensor was employed in combination of bright field microscopy to characterize cellular apoptosis. HeLa cells undergoing apoptosis induced by hydrogen peroxide (H2O2) were monitored by SPR and the signals were compared to microscopic analysis of the morphological changes. SPR study revealed a decreased signal as cell confluency decreases, with the rates increasing as H2O2 concentration increases. An abnormality was found at high concentrations when both apoptosis and necrosis were induced. A mathematical model was proposed to explain SPR response where a non- uniform adsorbed layer was partially responsible. The significance of this thesis is that a number of high performing biosensing approaches have been developed and demonstrated. In addition to the advantages of SPR (e.g. label-free, real-time biomolecules binding, and portability), these methods have paved the way towards realizing effective sensing in biomedical research, especially in the early detection of infectious diseases and in the treatment of cancers

Integrated optical fluorescence multi-sensor system

Research on fluorescence-based integrated optical immunoassay multisensing systems has gained growing interest in the last ten years. This is because the systems have the potential to simultaneously detect multiple analytes in a single measurement, and the techniques involved are fast, robust and cost-effective. Therefore they have the potential to replace conventional chromatographic techniques, as the monitoring systems for the rapid assessment of water or food samples. Other areas, such as clinical diagnostics or forensic science also have a demand for highly multiplexed analytical systems. This thesis presents a novel 32-analyte integrated optical fluorescence-based multisensor, and its integration to an automated multi-bio-sensing system. This system is primarily used for detecting organic pollutants in river water. A detailed study was also carried out with a CCD detector system, used to replace the fibre collection and photodiode array system and allow straight forward extension to more than 32 analytes. A direct comparison between these two systems is also presented

On-chip food safety monitoring: multi-analyte screening with imaging surface plasmon resonance-based biosensor

Food safety is an increasing health concern, recognised and promoted by many institutions across the globe. Food products can be contaminated with pathogenic microorganisms, environmental pollutants, veterinary drug residues, allergens and toxins. Public health concerns which have been raised in relation to hazardous agents found in food include, among others, increased cancer risk, endocrine, reproductive and neurobehavioral systems disruption, teratogenesis, antibiotic resistance and even death in cases of allergic reactions and acute poisoning. Some of the food hazardous agents (e.g. pathogenic microorganisms and toxins) can even be used as biological warfare, spread through food and agricultural chains. Thus, an adequate detection of these compounds is also important for biosecurity. In order to safeguard consumers’ health, legislations have been put in place both in the US and the EU. These laws specify for each health threatening compound the maximal acceptable amounts in different food products. Besides health issues, food safety and quality has an economical impact on the food industry, where quality control expenses amount to about 1.5 – 2 % of the total sales. Since more and more food products nowadays contain multiple and processed ingredients, which are often shipped from different parts of the world, and share common production lines and storage spaces, food safety and quality monitoring becomes a challenging task. Traditional analytical methods require dedicated laboratories, equipment and highly trained personnel for detection and identification of each type of hazardous agent (e.g. antibiotics, bacteria, allergens). These techniques are also time-consuming and often expensive. There is a growing need for multi-analyte screening methods, which will enable rapid and simultaneous detection of multiple compounds in complex food samples. In recent years, biosensors have been applied successfully to food analysis, incorporating the same bioassay principals as traditional methods with transducers (optical, electrochemical, etc) in novel, usually miniaturized, integrated analytical devices. However, most of these biosensors still lack the desired level of the multiplexicity. Recent developments in the field of Surface Plasmon Resonance (SPR) technology in the direction of high-throughput systems and multi-analyte measurements present a promising alternative for the existing systems. One of such systems is imaging SPR (iSPR); it enables real-time and label free read-out of spatially modified surfaces (e.g. microarrays). The aim of this study was to develop an iSPR–based biosensor, for simultaneous and quantitative detection of different health-threatening compounds in food. To obtain a comprehensive overview on the analytical applicability of such a system, several points were addressed. The intrinsic sensor properties, such as optical sensitivity and robustness, of the iSPR instrument were studied. Further on, both direct and competitive immunoassay formats for high and low molecular weight compounds detection using the iSPR platform were evaluated. Then, the iSPR-based biosensor was applied for detection of regulated substances in food such as antibiotic residues in milk and allergens in cookies and chocolates. Finally, the most common drawback of using SPR for screening in complex biological matrices, the nonspecific binding to the sensor chip surface, was tackled. The sensitivity of both high and low molecular weight compounds was proven to be sufficient for some of the hazardous agents detection at the maximum residue levels, established in the EU legislation, as was demonstrated by simultaneous detection of seven antibiotic residues in milk and twelve allergens in cookies and dark chocolates. The analysis time takes about 10 minutes and provides quantitative information on multiple targets, producing a fingerprint (allergenic fingerprint for instance) of the tested food. This detailed food profile contributes to the decision making process on the quality and safety of foods, basing it on the total picture of all target compounds present. In order for iSPR-based biosensing to reach its full potential and to become a widely applied routine analytical tool, the instrumental cost needs to be reduced and the analysis further simplified, becoming cost-effective and approachable to non-trained personnel. An additional drawback in analytical applications of a SPR sensor is the nonspecific binding of the matrix components of complex samples to the sensor surface. Many assays based on SPR fail due to inapplicability to measure in “real” samples. As a possible solution to this problem, sensor chip surface engineering was suggested in this thesis. A nanopatterned filter layer covering the sensor chip surface was found to be effective in reducing nonspecific binding when the measurements were performed in “raw” samples by keeping the non-soluble aggregates and big sample matrix components beyond the sensing region of the SPR. With respect to other existing biosensors, iSPR still lags behind in terms of sensitivity and portability. In summary, the results of this study demonstrate that iSPR-based biosensor is a versatile platform, which can be applied for a wide variety of fundamentally different analytes and offers several advantages over already existing methods. SPR detection principle eliminates the need in labelling and the instrumental set-up allows automated analysis. High multiplexing capabilities and short measurement times are obtained with no need for complex and time consuming sample preparation steps. By using iSPR-based biosensor, one can obtain robust and quantitative information on the target analyte concentration, in real time and with high specificity (or broad spectrum, depending on the assay). In conclusion, on-chip screening using iSPR, described here, presents a powerful analytical approach towards food safety and quality monitoring which satisfies the current need in rapid and multi-analytical devices. <br/

Wearable technology for one health: Charting the course of dermal biosensing

Over the last decade, a significant paradigm shift has been observed towards leveraging less invasive biological fluids—such as skin interstitial fluid (ISF), sweat, tears, and saliva—for health monitoring. This evolution seeks to transcend traditional, invasive blood-based methods, offering a more accessible approach to health monitoring for non-specialized personnel. Skin ISF, with its profound resemblance to blood, emerges as a pivotal medium for the real-time, minimally invasive tracking of a broad spectrum of biomarkers, thus becoming an invaluable asset for correlating with blood-based data. Our exploration delves deeply into the development of wearable molecular biosensors, spotlighting dermal sensors for their pivotal roles across both clinical and everyday health monitoring scenarios and underscoring their contributions to the holistic One Health initiative. In bringing forward the myriad challenges that permeate this field, we also project future directions, notably the potential of skin ISF as a promising candidate for continuous health tracking. Moreover, this paper aims to catalyse further exploration and innovation by presenting a curated selection of seminal technological advancements. Amidst the saturated landscape of analytical literature on translational challenges, our approach distinctly seeks to highlight recent developments. In attracting a wider spectrum of research groups to this versatile domain, we endeavour to broaden the collective understanding of its trajectory and potential, mapping the evolution of wearable biosensor technology. This strategy not only illuminates the transformative impact of wearable biosensors in reshaping health diagnostics and personalized medicine but also fosters increased participation and progress within the field. Distinct from recent manuscripts in this domain, our review serves as a distillation of key concepts, elucidating pivotal papers that mark the latest advancements in wearable sensors. Through presenting a curated collection of landmark studies and offering our perspectives on the challenges and forward paths, this paper seeks to guide new entrants in the area. We delineate a division between wearable epidermal and subdermal sensors—focusing on the latter as the future frontier—thereby establishing a unique discourse within the ongoing narrative on wearable sensing technologies

Wearable Skin-Worn Enzyme-Based Electrochemical Devices: Biosensing, Energy Harvesting, and Self-Powered Sensing

Integrating enzymes with wearable electrochemical systems delivers extraordinary functional devices, including biosensors and biofuel cells (BFCs). Strategies employing enzyme-based bioelectronics represent a unique foundation of wearables because of specific enzyme recognition and catalytic activities. Therefore, such electrochemical biodevices on various platforms, e.g., tattoos, textiles, and wearable accessories, are interesting. However, these devices need effective power sources, requiring combining effective energy sources, such as BFCs, onto compact and conformal platforms. Advantageously, bioenergy-harvesting BFCs can also act as self-powered sensors, simplifying wearable systems. Challenges pertaining to energy requirements and the integration of biocatalysts with electrodes should be considered. In this chapter, we detail updated advancement in skin-worn devices, including biosensors, BFCs, and self-powered sensors, along with engineering designs and on-skin iontophoretic strategies to extract biofluids. Crucial parameters including mechanical/material aspects (e.g., stretchability), electrochemistry, enzyme-related views (e.g., electron shuttles, immobilization, and behaviors), and oxygen dependency will be discussed, along with outlooks. Understanding such challenges and opportunities is important to revolutionize wearable devices for diverse applications

Thin film integrated optical waveguides for biosensing using local evanescent field detection

2010 Spring.Includes bibliographic references.Covers not scanned.Print version deaccessioned 2022.A waveguide is a high refractive index material that is surrounded by lower refractive index cladding. This waveguide structure can be used to carry light confined to the high refractive index core. Surrounding the core of the waveguide is a decaying evanescent light field that extends into the cladding layers. The intensity profile of the evanescent field is dependent on the refractive index of the cladding. The changes in the local intensity of the evanescent field can be used to detect refractive index changes near the core of the waveguide. A high refractive index film deposited on a flat, low refractive index .substrate can be used to form a waveguide with a planar geometry. The planar design allows the upper cladding refractive index to be modified by attaching proteins or patterning organic films. This design also allows the evanescent field intensity to be measured using near field scanning optical microscopy or a silicon photo detector array. The fabrication and characterization of a waveguide device with a coupled light source was accomplished. The evanescent field response to thin films of patterned photoresist was found using NSOM. Light intensity measured at the surface of the .sample showed significant response to the presence of the photoresist features. Light response to a protein affinity assay was found and results indicated that protein concentration could be inferred from local evanescent field measurements. A buried silicon photo detector was fabricated and characterized. The results show the field responds in a significant matter to uniform and pattered features on the waveguide core

State of the art on the SARS-CoV-2 toolkit for antigen detection: one year later

The recent global events of COVID-19 in 2020 have alerted the world to the risk of viruses and their impacts on human health, including their impacts in the social and economic sectors. Rapid tests are urgently required to enable antigen detection and thus to facilitate rapid and simple evaluations of contagious individuals, with the overriding goal to delimitate spread of the virus among the population. Many efforts have been achieved in recent months through the realization of novel diagnostic tools for rapid, affordable, and accurate analysis, thereby enabling prompt responses to the pandemic infection. This review reports the latest results on electrochemical and optical biosensors realized for the specific detection of SARS-CoV-2 antigens, thus providing an overview of the available diagnostics tested and marketed for SARS-CoV-2 antigens as well as their pros and cons

Hydrogel microparticles for biosensing

Due to their hydrophilic, biocompatible, and highly tunable nature, hydrogel materials have attracted strong interest in the recent years for numerous biotechnological applications. In particular, their solution-like environment and non-fouling nature in complex biological samples render hydrogels as ideal substrates for biosensing applications. Hydrogel coatings, and later, gel dot surface microarrays, were successfully used in sensitive nucleic acid assays and immunoassays. More recently, new microfabrication techniques for synthesizing encoded particles from hydrogel materials have enabled the development of hydrogel-based suspension arrays. Lithography processes and droplet-based microfluidic techniques enable generation of libraries of particles with unique spectral or graphical codes, for multiplexed sensing in biological samples. In this review, we discuss the key questions arising when designing hydrogel particles dedicated to biosensing. How can the hydrogel material be engineered in order to tune its properties and immobilize bioprobes inside? What are the strategies to fabricate and encode gel particles, and how can particles be processed and decoded after the assay? Finally, we review the bioassays reported so far in the literature that have used hydrogel particle arrays and give an outlook of further developments of the field. Keywords: Hydrogel; Biosensor; Microparticle; Multiplex assayNovartis Institutes of Biomedical Research (Presidential Fellowship)Novartis Institutes of Biomedical Research (Education Office)National Cancer Institute (U.S.) (Grant 5R21CA177393-02)National Science Foundation (U.S.) (Grant CMMI-1120724)Institute for Collaborative Biotechnologies (Grant W911NF-09-0001)United States. Army Research Offic

Transforming Early Microbial Detection: Investigating Innovative Biosensors for Emerging Infectious Diseases

The recent global pandemic has highlighted an increase in the prevalence of communicable diseases caused by pathogens. The swift transmission of these diseases within a short timeframe presents a substantial risk to public health worldwide. The inefficiency of traditional diagnostic instruments, which need a time-consuming and complex process in the laboratory, is a significant obstacle to medical care. Currently, there is a high need for the advancement of early detection in order to rapidly diagnose infectious diseases and provide on-site results. This is crucial for prompt and early intervention to improve treatment outcomes. This also provides rapid testing and high-quality microbiological detection, comparable to laboratory standards, in a matter of minutes. Prompt diagnosis and subsequent treatment optimization aid in controlling the spread of infectious diseases. Currently, ongoing techniques and methods are used in the advancements of early detection through biosensors. This review examines the integration of early diagnostics with biosensors, specifically in relation to emerging and re-emerging infectious diseases, challenges, and the future perspective