Integratable opto-microfluidic devices for sensitive detection of bio-analytes

The expensive fabrication of current optical microfluidic devices is a barrier to the successful implementation of these devices in low-cost, high-sensitivity biosensing systems. Organic photodiodes (OPDs) have great potential for application as photodetectors in integrated microfluidic devices due to their uncomplicated optical alignment, thin device architecture, precise control of the active area and simple device fabrication onto glass or polymer substrates. Recent developments in OPDs have resulted in new photoactive materials, such as poly[N-9´-heptadecanyl-2,7-carbazolealt- 5,5-(4´,7´-di-2-thienyl-2´,1´,3´-benzothiadiazole)] (PCDTBT), that have improved detectivity and stability. These unique optoelectronic characteristics enhance the detection sensitivity of OPD-integrated microfluidic biosensors while maintaining simple, inexpensive device fabrication. To realise point-of-care (POC) detection of bio-analytes, the complexity of optical instrumentation must be minimised. Chemiluminescence (CL) offers an attractive solution to microfluidic analyte detection because it precludes the use of excitation light sources and emission filters. However, the low intensity of light emitted from CL reactions demands the use of highly sensitive photodetectors. Therefore, investigations of strategies to enhance CL assays and the combination of CL with PCDTBT-based detectors are the motivating factors for this work. Additionally, the enrichment of target organisms using a high-efficiency recovery method provides a route to optically detect bio-analytes at concentrations as low as hundreds or tens of organisms in a sample. This doctoral thesis focuses on the following challenges: (i) demonstrate sensitive CL detection using a PCDTBT-based photodetector, (ii) investigate the integration of multiple OPDs in high-throughput microfluidic chips to realise multiplexed CL detection and (iii) explore methods for enhancing the sensitivity of opto-microfluidic detection. The progress made towards addressing these challenges is summarised below. Article I reported the design and fabrication of an integrated optical microfluidic device employing a PCDTBT-based photodetector. The response of the OPD to CL light was enhanced by optimising the thickness of the photoactive layer and the hole transport layer. The current-voltage response due to detection of a medically relevant protein analyte was characterised. Further demonstration of quantitative CL detection with the optimised OPD was conducted in Article II. The opto-microfluidic device was found to exhibit a linear response over four orders of magnitude, with a detection limit of approximately tens of picograms per millilitre and a detection sensitivity of approximately hundreds of picograms per millilitre. Moreover, high reproducibility and specificity to CL detection was observed, indicating the capability of the integrated OPD for POC applications. Article III developed a multiplexed CL detection platform by integrating multiple PCDTBT OPDs with a high-throughput microfluidic chip. The fabricated device is compatible with mass production methods. The analytical performance of the OPD pixel was characterised for the detection of individual waterborne pathogens. Article IV performed a series of parallel CL detection experiments to demonstrate the simultaneous detection of multiple waterborne pathogens in one water sample. Rapid multiplexed analysis and extension to complex samples were demonstrated. Article V investigated the enhancement of CL detection by incorporating standard gold nanoparticles into a simple, inexpensive opto-microfluidic device. The limit of detection for an environmentally relevant protein analyte was ∼200 times lower than previously reported CL sensors using other OPD designs. The remarkable stability and specific detectivity of the PCDTBT OPD was also characterised. Article VI presented a high-efficiency bio-analyte recovery system by incorporating multiple counter-flow filtration units. A high concentrating ratio was obtained with a short processing time. The filtration system showed recovery efficiencies above 80% for waterborne protozoa at environmentally realistic concentrations in real environmental water samples. A compact filter made of multiple counter-flow units arranged into a cascade-like structure is also shown. The separation of water particulates from the target protozoan organisms was addressed to enhance the recovery performance of conventionally used filters

Microfluidics for Biosensing and Diagnostics

Efforts to miniaturize sensing and diagnostic devices and to integrate multiple functions into one device have caused massive growth in the field of microfluidics and this integration is now recognized as an important feature of most new diagnostic approaches. These approaches have and continue to change the field of biosensing and diagnostics. In this Special Issue, we present a small collection of works describing microfluidics with applications in biosensing and diagnostics

Smartphone-based food diagnostic technologies: A review

A new generation of mobile sensing approaches offers significant advantages over traditional platforms in terms of test speed, control, low cost, ease-of-operation, and data management, and requires minimal equipment and user involvement. The marriage of novel sensing technologies with cellphones enables the development of powerful lab-on-smartphone platforms for many important applications including medical diagnosis, environmental monitoring, and food safety analysis. This paper reviews the recent advancements and developments in the field of smartphone-based food diagnostic technologies, with an emphasis on custom modules to enhance smartphone sensing capabilities. These devices typically comprise multiple components such as detectors, sample processors, disposable chips, batteries and software, which are integrated with a commercial smartphone. One of the most important aspects of developing these systems is the integration of these components onto a compact and lightweight platform that requires minimal power. To date, researchers have demonstrated several promising approaches employing various sensing techniques and device configurations. We aim to provide a systematic classification according to the detection strategy, providing a critical discussion of strengths and weaknesses. We have also extended the analysis to the food scanning devices that are increasingly populating the Internet of Things (IoT) market, demonstrating how this field is indeed promising, as the research outputs are quickly capitalized on new start-up companies

Micro/Nano-Chip Electrokinetics

Micro/nanofluidic chips have found increasing applications in the analysis of chemical and biological samples over the past two decades. Electrokinetics has become the method of choice in these micro/nano-chips for transporting, manipulating and sensing ions, (bio)molecules, fluids and (bio)particles, etc., due to the high maneuverability, scalability, sensitivity, and integrability. The involved phenomena, which cover electroosmosis, electrophoresis, dielectrophoresis, electrohydrodynamics, electrothermal flow, diffusioosmosis, diffusiophoresis, streaming potential, current, etc., arise from either the inherent or the induced surface charge on the solid-liquid interface under DC and/or AC electric fields. To review the state-of-the-art of micro/nanochip electrokinetics, we welcome, in this Special Issue of Micromachines, all original research or review articles on the fundamentals and applications of the variety of electrokinetic phenomena in both microfluidic and nanofluidic devices

Miniaturization of fluorescence sensing in optofluidic devices

International audienceSuccessful development of a micro-total-analysis system (μTAS, lab-on-a-chip) is strictly related to the degree of miniaturization, integration, autonomy, sensitivity, selectivity, and repeatability of its detector. Fluorescence sensing is an optical detection method used for a large variety of biological and chemical assays, and its full integration within lab-on-a-chip devices remains a challenge. Important achievements were reported during the last few years, including improvements of previously reported methodologies, as well as new integration strategies. However, a universal paradigm remains elusive. This review considers achievements in the field of fluorescence sensing miniaturization, starting from off-chip approaches, representing miniaturized versions of their lab counter-parts, continuing gradually with strategies that aim to fully integrate fluorescence detection on-chip, and reporting the results around integration strategies based on optical-fiber-based designs,optical layer integrated designs, CMOS-based fluorescence sensing, and organic electronics. Further successful development in this field would enable the implementation of sensing networks in specific environments that, when coupled to Internet of-Things (IoT) and artificial intelligence (AI), could provide real-time data collection and, therefore, revolutionize fields like health, environmental, and industrial sensing

マルチキャピラリーガラスプレートとポリジメチルシロキサンマイクロアレイを用いたマイクロイムノアッセイプラットフォームの開発

首都大学東京, 2014-09-30, 博士（工学）首都大学東

Doctor of Philosophy

dissertationMonitoring and remediation of environmental contaminants (biological and chemical) form the crux of global water resource management. There is an extant need to develop point-of-use, low-power, low-cost tools that can address this problem effectively with min­ imal environmental impact. Nanotechnology and microfluidics have made enormous ad­ vances during the past decade in the area of biosensing and environmental remediation. The "marriage" of these two technologies can effectively address some of the above-mentioned needs [1]. In this dissertation, nanomaterials were used in conjunction with microfluidic techniques to detect and degrade biological and chemical pollutants. In the first project, a point-of-use sensor was developed for detection of trichloroethylene (TCE) from water. A self-organizing nanotubular titanium dioxide (TNA) synthesized by electrochemical anodization and functionalized with photocatalytically deposited platinum (Pt/TNA) was applied to the detection. The morphology and crystallinity of the Pt/TNA sensor was characterized using field emission scanning electron microscope, energy dis­ persive x-ray spectroscopy, and X-ray diffraction. The sensor could detect TCE in the concentrations ranging from 10 to 1000 ppm. The room-temperature operation capability of the sensor makes it less power intensive and can potentially be incorporated into a field-based sensor. In the second part, TNA synthesized on a foil was incorporated into a flow-based microfluidic format and applied to degradation of a model pollutant, methylene blue. The system was demonstrated to have enhanced photocatalytic performance at higher flow rates (50-200 ^L/min) over the same microfluidic format with TiO2 nanoparticulate (commercial P25) catalyst. The microfluidic format with TNA catalyst was able to achieve 82% fractional conversion of 18 mM methylene blue in comparison to 55% in the case of the TiO2 nanoparticulate layer at a flow rate of 200 L/min. The microfluidic device was fabricated using non-cleanroom-based methods, making it suitable for economical large-scale manufacture. A computational model of the microfluidic format was developed in COMSOL Multiphysics® finite element software to evaluate the effect of diffusion coefficient and rate constant on the photocatalytic performance. To further enhance the photocatalytic performance of the microfluidic device, TNA synthesized on a mesh was used as the catalyst. The new system was shown to have enhanced photocatalytic performance in comparison to TNA on a foil. The device was then employed in the inactivation of E. coli O157:H7 at different flow rates and light intensities (100, 50, 20, 10 mW/cm2). In the second project, a protocol for ultra-sensitive indirect electrochemical detection of E. coli O157:H7 was reported. The protocol uses antibody functionalized primary (magnetic) beads for capture and polyguanine (polyG) oligonucleotide functionalized sec­ ondary (polystyrene) beads as an electrochemical tag. The method was able to detect concentrations of E. coli O157:H7 down to 3 CFU/100 mL (S/N=3). We also demonstrate the use of the protocol for detection of E. coli O157:H7 seeded in wastewater effluent samples

Concentration of Phosphorylated Proteins Using Modified PMMA Microanalytical Devices

This work describes the application of PMMA-based microanalytical devices for the affinity-type preconcentration of posttranslational modified proteins (PTMs). The choice of poly(methyl methacrylate), PMMA, is based on its biocompatibility, its functional methyl ester group for potential modification, and its extensive applications to create biological microelectromechanical systems (BioMEMS). Developing methodologies for preconcentration of PTMs is important for cancer diagnosis due to PTMs’ influence in the regulatory mechanism underlying the early stage of apoptosis or regulated cell death. Towards this goal, nitroavidin which can reversibly binds to biotin (and biotinylated proteins), was prepared using reported procedure and was characterized using several techniques such as UV-Visible spectroscopy, sodium dodecyl sulfate−polyacrylamide gel electrophoresis (SDS-PAGE), enzyme-linked immunosorbent assay (ELISA), and Western blot experiments. UV-Visible spectroscopy experiments showed reversible binding of nitroavidin towards the biotin analogue 2-(4’-hydroxyazobenzene) benzoic acid, HABA. From mass spectrometry studies, nitrotyrosine was confirmed to be present in the prepared nitroavidin through an observed photoinduced chemical fragmentation. SPR experiments revealed decrease in binding of nitroavidin towards biotinylated proteins (the equilibrium dissociation constant obtained for the biotin−nitroavidin interactions is higher, KD = 4 x 10–6 M, than biotin-avidin interactions, KD = 1 x 10–13 M). Also, there was an observed efficiency of 23 ± 1% for the capture process of biotinylated proteins on nitroavidin−functionalized PMMA open microchannels, while high capture efficiency (96 ± 0.5%) for bound biotinylated proteins were observed on PMMA microchannels with fabricated microposts. To further improve the efficiency of capture and release processes, PMMA ultra-high-aspect-ratio nanostructures (UHRANs) were employed to provide higher surface-to-volume reactor bed. These PMMA UHRANs were fabricated in our group using previously reported template-based anodization. PMMA nanopillars or nanoposts were developed using photopolymerization between the methyl methacrylate monomer and initiator, while PMMA nanotubes were fabricated using PMMA melt. These nanostructures were UV-modified to promote formation of surface carboxylic acids (pendant −COOH). The confirmation of surface –COOH functionalization on these surfaces was achieved using different surface labeling techniques such as thallium (I) ethoxide and sulfosuccinimidyl-4-o-(4,4-dimethoxytrityl) butyrate (sulfo-SDTB) and were determined using several techniques such as confocal fluorescence microscopy, UV-Visible spectroscopy, AFM, SEM, and XPS

Advances in Optofluidics

Optofluidics a niche research field that integrates optics with microfluidics. It started with elegant demonstrations of the passive interaction of light and liquid media such as liquid waveguides and liquid tunable lenses. Recently, the optofluidics continues the advance in liquid-based optical devices/systems. In addition, it has expanded rapidly into many other fields that involve lightwave (or photon) and liquid media. This Special Issue invites review articles (only review articles) that update the latest progress of the optofluidics in various aspects, such as new functional devices, new integrated systems, new fabrication techniques, new applications, etc. It covers, but is not limited to, topics such as micro-optics in liquid media, optofluidic sensors, integrated micro-optical systems, displays, optofluidics-on-fibers, optofluidic manipulation, energy and environmental applciations, and so on