Development of Nanofiber and Surface Plasmon Resonance Sensors for VOCs, Biochemical, and Bacterial Analysis

It is important to monitor potential exposure to various chemicals and toxicants that may adversely affect both human and environmental health. Biosensors have been developed to identify and quantify these analytes of interest in early warning systems and diagnosis devices. This dissertation implements nanomaterials, such as nanofibers and nanoparticles, into the biological recognition element of a biosensor for selectively and sensitively to detect trace analytes in either gas, liquid, or solid phases.This dissertation is an agglomeration of several different projects that investigates the novel applications of nanomaterials into biosensor designs with two major application focuses: nanofibers and surface plasmon resonance (SPR) The first half of this dissertation focuses on the application of nanofiber surfaces for sensor developments. The nanofibers were fabricated through electrospinning and incorporated into various sensor designs. The first project develops polyaniline nanofibers into a chemiresistor sensor for sensitive detection of VOCs (small chain alcohols) by employing variants of reduced graphene oxides. The second project applies the nanofiber property of high surface area to volume ratio to maximize surface adsorption of EDTA-functionalized silver nanoparticles (AgNPs) as the biorecognition element of this sensor. The EDTA-AgNPs formulates a nickel ion bridge for selective capture and release of NTA and His tagged proteins that can be detected through fluorescent spectroscopy. The second half of this dissertation transitions into the application of surface plasmon resonance for the development of biosensor signal transducers. The third project focused on combining the potential of 3D printing with gold nanoparticles (AuNPs) to create a novel integrated localized SPR (LSPR) sensor surface capable of sensitive protein detection. The synthesis of gold nanoparticles in-situ on a 3D printed prism surface enables the fabrication of a biosensor device for the disposable field of site usage with qualities comparable performances with sensors using commercial optical prisms. The last project focuses on developing an SPR experimental model of a double lipid bilayer membrane. This model mimics the unique structure of the double lipid bilayer membrane system found in the chloroplast, mitochondria, and gram-negative bacteria. This novel experimental model combined with SPR analysis creates a biosensor platform that enables the interrogation of chemical and protein interactions at interfaces such as the gram-negative bacteria cell wall and membrane system

Advances in Microtechnology for Improved Cytotoxicity Assessment

In vitro cytotoxicity testing is essential in the pharmaceutical and environmental industry to study the effects of potential harmful compounds for human health. Classical assays present several disadvantages: they are commonly based on live-death labelling, are highly time consuming and/or require skilled personnel to be performed. The current trend is to reduce the number of required cells and the time during the analysis, while increasing the screening capability and the accuracy and sensitivity of the assays, aiming single cell resolution. Microfabrication and surface engineering are enabling novel approaches for cytotoxicity assessment, offering high sensitivity and the possibility of automation in order to minimize user intervention. This review aims to overview the different microtechnology approaches available in this field, focusing on the novel developments for high-throughput, dynamic and real time screening of cytotoxic compounds.Funding support from: University of the Basque Country (PIF16/204), the funding support from Gobierno de España, Ministerio de Economía y Competitividad, with Grant No. BIO2016-80417-P (AEI/FEDER, UE) and Gobierno Vasco under grand IT1271-19

Recent Advancements in the Technologies Detecting Food Spoiling Agents

To match the current life-style, there is a huge demand and market for the processed food whose manufacturing requires multiple steps. The mounting demand increases the pressure on the producers and the regulatory bodies to provide sensitive, facile, and cost-effective methods to safeguard consumers’ health. In the multistep process of food processing, there are several chances that the food-spoiling microbes or contaminants could enter the supply chain. In this contest, there is a dire necessity to comprehend, implement, and monitor the levels of contaminants by utilizing various available methods, such as single-cell droplet microfluidic system, DNA biosensor, nanobiosensor, smartphone-based biosensor, aptasensor, and DNA microarray-based methods. The current review focuses on the advancements in these methods for the detection of food-borne contaminants and pathogens

Methods for immobilizing receptors in microfluidic devices: A review

In this review article, we discuss state-of-the-art methods for immobilizing functional receptors in microfluidic devices. Strategies used to immobilize receptors in such devices are essential for the development of specific, sensitive (bio)chemical assays that can be used for a wide range of applications. In the first section, we review the principles and the chemistry of immobilization techniques that are the most commonly used in microfluidics. We afterward describe immobilization methods on static surfaces from microchannel surfaces to electrode surfaces with a particular attention to opportunities offered by hydrogel surfaces. Finally, we discuss immobilization methods on mobile surfaces with an emphasis on both magnetic and non-magnetic microbeads, and finally, we highlight recent developments of new types of mobile supports

Organic-based field effect transistors for protein detection fabricated by inkjet-printing

Altres ajuts: CERCA Programme/Generalitat de Catalunya.Biosensors based on Organic Field-Effect Transistors (OFETs) have attracted increasing attention due to the possibility of rapid, label-free, and inexpensive detection. Among all the different possibilities, inkjet-printed top-gate organic Field Effect Transistors-Based Biosensors (BioFETs) using a polymeric gate insulator have been seldom reported. In this work, a systematic investigation in terms of topographical and electrical characterization was carried out in order to find the optimal fabrication process for obtaining a reliable polymer insulator. Previous studies have demonstrated that the best electrical performance arises from the use of the perfluoropolymer Cytop™[12,13,14]. Consequently, a simple immobilization protocol was used to ensure the proper attachment of a model biomolecule onto the Cytop's hydrophobic surface whilst keeping its remarkable insulating properties with gate current in the range of dozens of pico-amperes. The top-gate inkjet-printed BioFETs presented in this study operate at threshold voltages in the range of 1-2 V and show durability even when exposed to oxygen plasma, wet amine functionalization treatments, and aqueous media. As a preliminary application, the inkjet-printed top-gate BioFETs is used for monitoring an immunoreaction by measuring changes in the drain current, paving the way for further use of this device in the immunosensing field

NANOENGINEERED SURFACES AND CARBON NANOTUBE CONJUGATED MICROWIRE BIOSENSOR FOR MICROBIAL CONTROL AND DETECTION

M.S

THREE-DIMENSIONAL BIOPATTERNING TECHNOLOGY AND APPLICATION FOR ENZYME-BASED BIOELECTRONICS

Integration of biomaterials with 3-D micro/nano devices and systems offers exciting opportunities for developing miniature bioelectronics with enhanced performances and advanced modes of operation. However, the limited wetting property of such small scale 3-D structures (Cassie-Baxter wetting) presents a potential challenge in these developments considering most biological materials require storage in buffered aqueous solutions due to their inherently narrow stability window. In this thesis research, an electrowetting-assisted 3-D biomanufacturing technology has been developed enabling highly selective and programmable biomolecular assembly on 3-D device components. The successful integration of microscale 3-D device structures created via conventional microfabrication techniques with a nanoscale molecular assembly of Tobacco mosaic virus (TMV), enabled hierarchical and modular material assembly approaches for creating highly functional and scalable enzyme-integrated microsystems components. The potential limitation in 3-D bio-device integration associated with the surface wettability has been investigated by adapting Si-based micropillar arrays (μPAs) as model 3-D device structures, and a cysteine-modified TMV (TMV1cys), as the biomolecular assembler which can functionalize onto electrode surfaces via a self-assembly. The comparative studies using μPAs of varying pillar densities have provided clear experimental evidence that the surface coverage of TMV1cys self-assembly on the μPA is strongly correlated with structural density, indicating the structural hydrophobicity as a key limiting factor for 3-D bio-device integration. The 3-D electro-bioprinting (3D-EBP) technology developed in this work leverages the hydrophobic surface wettability by adapting a capacitive wettability-control technique, known as electrowetting. The biological sample liquid was selectively introduced into the microcavities using a custom-integrated bioprinting system, allowing for patterning of the TMV1cys self-assembly on the μPA substrates without the limitations of the structural density. The functional integrity of the TMV1cys post 3D-EBP allowed conjugations of additional biological molecules within the 3-D substrates. Particularly in this work, immobilization of glucose oxidase (GOx) has been achieved via a hierarchical on-chip immobilization method incorporating 3D-EBP. Combined with the enhanced and scalable enzymatic reaction density on-chip and the electrochemical conversion strategies, the innovative 3D biomanufacturing technology opens up new possibilities for next-generation enzyme-based bioelectronics

Correlating the Effect of Dynamic Variability in the Sensor Environment on Sensor Design

This dissertation studies the effect of biofluid dynamics on the electrochemical response of a wearable sensor for monitoring of chronic wounds. The research investigates various dynamic in vivo parameters and correlates them with experimentally measured behavior with wound monitoring as a use case. Wearable electrochemical biosensors suffer from several unaddressed challenges, like stability and sensitivity, that need to be resolved for obtaining accurate data. One of the major challenges in the use of these sensors is continuous variation in biofluid composition. Wound healing is a dynamic process with wound composition changing continuously. This dissertation investigates the effects of several in vivo biochemical and environmental parameters on the sensor response to establish actionable correlations. Real-time assessment of wound healing was carried out through longitudinal monitoring of uric acid and other wound fluid characteristics. A textile sensor was designed using a simple fabrication approach combining conductive inks with a polymeric substrate, for conformal contact with the wound bed. A −1 cm−2, establishing the applicability of the sensor for measurements in the physiologically relevant range. The sensor was also found to be stable for a period of 3 days when subjected to physiological and elevated temperatures (37oC and 40oC) confirming its relevance for long-term monitoring. A direct correlation between sensor response and the dynamic parameters was seen, with the results showing a ~20% deviation from the accurate UA reading. The results confirmed that as a consequence of these parameters temporally changing in the wound environment, the sensor response will be altered. The work develops mathematical models correlating this effect on sensor response to allow for real-time sensor calibration. The clinical validation studies established the feasibility of UA measurement by the developed electrochemical sensor and derive correlations between the wound chronicity and UA levels. The protocols developed in this work for the design, fabrication, and calibration of the sensor to correct for the dynamic in vivo behavior can be extended to any wearable sensor for improved accuracy