Shekhar Bhansali

Recent advances in ZnO nanostructures and thin films for biosensor applications: Review

Biosensors have shown great potential for health care and environmental monitoring. The performance of biosensors depends on their components, among which the matrix material, i.e., the layer between the recognition layer of biomolecule and transducer, plays a crucial role in defining the stability, sensitivity and shelf-life of a biosensor. Recently, zinc oxide (ZnO) nanostructures and thin films have attracted much interest as materials for biosensors due to their biocompatibility, chemical stability, high isoelectric point, electrochemical activity, high electron mobility, ease of synthesis by diverse methods and high surface-to-volume ratio. ZnO nanostructures have shown the binding of biomolecules in desired orientations with improved conformation and high biological activity, resulting in enhanced sensing characteristics. Furthermore, compatibility with complementary metal oxide semiconductor technology for constructing integrated circuits makes ZnO nanostructures suitable candidate for future small integrated biosensor devices. This review highlights recent advances in various approaches towards synthesis of ZnO nanostructures and thin films and their applications in biosensor technology.

A new magnetic bead-based, filterless bio-separator with planar electromagnet surfaces for integrated bio-detection systems

Abstract A new filterless bio-separator separating magnetic microbeads from a carrier fluid has been designed, fabricated, and characterized as a core component of biological cell sampling and detecting systems. To maximize the sampling capability, a planar electromagnet surface with a serpentine coil and semi-encapsulated permalloy has been realized. Using this bio-separator, antibody-coated magnetic beads have been successfully separated from the bio-buffer suspension solution and characterized in dynamic fluid flow. The magnetic characteristics of the bio-separator have been simulated and experimentally studied to establish and validate the design rules for fabrication. The realized filterless bio-separator has a high potential in biomedical and biological detection systems. It is especially useful in selective sampling and separation of small amounts of bio-molecules (e.g., antigen) for on-chip micro total analysis systems (μ-TAS) or remote detection systems.

Organic–Inorganic Hybrid Nanocomposite-Based Gas Sensors for Environmental Monitoring

Environmental Monitoring Ajeet Kaushik,*,†,‡ Rajesh Kumar,*,‡,§ Sunil K. Arya, Madhavan Nair,† B. D. Malhotra, and Shekhar Bhansali‡ †Center for Personalized Nanomedicine, Institute of Neuroimmune Pharmacology, Department of Immunology, Herbert Wertheim College of Medicine, Florida International University, Miami, Florida 33199, United States ‡Bio-MEMS Microsystems Laboratory, Department of Electrical and Computer Engineering, College of Engineering, Florida International University, Miami, Florida 33174, United States Department of Physics, Panjab University, Chandigarh 160014, India Bioelectronics Program, Institute of Microelectronics, A*Star, 11 Science Park Road, Singapore Science Park II, Singapore Department of Biotechnology, Delhi Technological University, Shahbad Daulatpur, Delhi 110042, India

Lung cancer and its early detection using biomarker-based biosensors.

1. Introduction 67831.1. Lung Cancer 67831.2. Causes, Genetic Changes, and TraditionalScreening of Lung Cancer 67831.3. Lung Cancer Biomarkers 67841.4. Biomarker Detection for Early Stage Screeningof Lung Cancer 67862. Matrix for Recognition Biomolecule Immobilization 67863. Electrochemical Transducers for Lung CancerBiomarker Detection 67983.1. Voltammetry-BasedBiosensorsforLungCancerBiomarker Detection 67993.1.1. Differential Pulse Voltammetry (DPV)-Based Lung Cancer Biomarker Detection 67993.1.2. Cyclic Voltammetry (CV)-Based LungCancer Biomarker Detection 68013.1.3. Linear Sweep Voltammetry (LSV)- andSquare Wave Voltammetry (SWV)-BasedLung Cancer Biomarker Detection 68033.2. Amperometric and Other ElectrochemicalTechniques-Based Lung Cancer BiomarkerDetection 68044. Optical Techniques-Based Lung Cancer BiomarkerDetection 68045. Other Techniques for Lung Cancer BiomarkerDetection 68056. Conclusions 6806Author Information 6807Biographies 6807Acknowledgment 6807Glossary 6807References 6808

Surface acoustic wave hydrogen sensor

The present invention provides a delay line SAW device fabricated on a lithium niobate substrate and coated with a bilayer of nanocrystalline or other nanomaterials such as nanoparticles or nanowires of palladiumn and metal free pthalocyanine which will respond to hydrogen gas in near real time, at low (room) temperature, without being affected by CO, O2, CH4 and other gases, in air ambient or controlled ambient, providing sensitivity to low ppm levels.

Development and Characterization of Microfluidic Devices and Systems for Magnetic Bead-Based Biochemical Detection

This paper presents the development and characterization of a generic microfluidic system for magnetic bead-based biochemical detection. Microfluidic and electrochemical detection devices such as microvalves, flow sensors, biofilters, and immunosensors have been successfully developed and individually characterized in this work. Magnetically driven microvalves, pulsed-mode microflow sensors, magnetic particle separators as biofilters, and electrochemical immunosensors have been sep-arately fabricated and tested. The fabricated microfluidic components have been surface-mounted on the microfluidic motherboard for fully integrated microfluidic biochemical detection system. A magnetic bio-bead approach has been adopted for both sampling and manipulating target biological molecules. Magnetic beads were used as both substrate of antibodies and carriers of target antigens for magnetic bead-based immunoassay, which was chosen as a proof-of-concept for the generic microfluidic bio-chemical detection system. The microfluidic and electrochemical immunosensing experiment results obtained from this work have shown that the biochemical sensing capability of the complete microfluidic subsystem is suitable for portable biochemical detection of bio-molecules. The methodology and system, which has been developed in this work, can be extended to generic bio-molecule detection and analysis systems by replacing antibody/antigen with appropriate bio receptors/reagents such as DNA fragments or oligonucleotides for application towards DNA analysis and/or high throughput protein analysis.

A low-temperature bonding technique using spin-on fluorocarbon polymers to assemble microsystems

A new low-temperature biochemically compatible polymer bonding process has been successfully developed. The bonding has been characterized for bond strength and chemical resistance. This technique has successfully addressed a major challenge in the development of microfluidic systems from discrete components by enabling the bonding of the components to the microfluidic motherboards at low temperatures and ensuring reliable, leak-proof and chemically inert bonding. This bonding technique uses a spin-on Teflon-like amorphous fluorocarbon polymer. The bonding technique lowers the bonding temperature (~160 °C), shows a good bond strength of 4.3 MPa in silicon-to-silicon, and has excellent chemical resistance to various chemicals used in microelectromechanical systems processing.

Sharpening of hollow silicon microneedles to reduce skin penetration force

In this research, hollow silicon microneedles with sharpened tips have been fabricated without any reduction to the needle shaft diameter. By sharpening the needles only at the tip and not over the entire length of the needle, their mechanical strength is maintained, while reducing the insertion force into skin. The process achieves this geometry by novel use photoresist depletion during DRIE. Microneedles of varying levels of tip sharpness were tested on human cadaver skin to measure their force of penetration. The results show a marked decrease of insertion force with progressive sharpening of microneedle tips, reducing more than 75 times in magnitude for extremely sharp tips. The toughness of human skin was derived to be approximately 24.28 kJ m?2.

Dithiobis(succinimidyl propionate) modified gold microarray electrode based electrochemical immunosensor for ultrasensitive detection of cortisol.

Gold microelectrode arrays functionalized with dithiobis(succinimidyl propionate) self-assembled monolayer (SAM) have been used to fabricate an ultrasensitive, disposable, electrochemical cortisol immunosensor. Cortisol specific monoclonal antibody (C-Mab) was covalently immobilized on the surface of gold microelectrode array and the sensors were exposed to solutions with different cortisol concentration. After C-Mab binding, unreacted active groups of DTSP were blocked using ethanol amine (EA) and label-free electrochemical impedance (EIS) technique was used to determine cortisol concentration. EIS results confirmed that EA/C-Mab/DTSP/Au based biosensor can accurately detect cortisol in the range of 1pM-100nM. The biosensor was successfully used for the measurement of cortisol in interstitial fluid in vitro. This research establishes the feasibility of using impedance based biosensor architecture for disposable, wearable cortisol detector.

Ionic liquid-mediated sol–gel coatings for capillary microextraction

Ionic liquid (IL)-mediated sol-gel hybrid organic-inorganic materials present enormous potential for effective use in analytical microextraction. This opportunity, however, has not yet been explored. One obstacle to materializing this prospect arises from high viscosity of ILs significantly slowing down sol-gel reactions. In this work, we developed a method that overcomes this hurdle and provides IL-mediated advanced sol-gel materials for capillary microextraction (CME). We examined two different ILs: (a) a phosphonium-based IL, trihexyltetradecylphosphonium tetrafluoroborate, and (b) a pyridinium-based ionic liquid, N-butyl-4-methylpyridinium tetrafluoroborate. These ILs were evaluated in conjunction with two types of hydroxy-terminated polymers: (a) two Si-OH terminated polymers (PDMS and BMPO), and (b) two C-OH terminated polymers (PEG and polyTHF) that differ in their sol-gel reactivity. Scanning electron microscopy results demonstrate that ILs can serve as porogenic agents in sol-gel reactions. The IL-mediated sol-gel coatings prepared with silanol-terminated polymers provided up to 28 times higher extractions in off-line CME-GC compared to analogous sol-gel coatings prepared without any IL in the sol solution. Contrary to this, the IL-mediated sol-gel coatings prepared with C-OH terminated polymers provided lower extraction efficiencies compared to their IL-free counterparts. These observations were explained by (a) lower sol-gel reactivity of C-OH groups in PEG and polyTHF compared to Si-OH groups in PDMS and in hydrolyzed alkoxysilane precursors and (b) extremely high viscosity of ionic liquids. This study shows that IL-generated porous morphology alone is not enough to provide effective extraction media: careful choice of the organic polymer and the precursor with close sol-gel reactivity must be made to ensure effective chemical bonding of the organic polymer to the created sol-gel material to be able to provide the desired sorbent characteristics. Additionally, IL-mediated sol-gel PDMS coatings provided run-to-run RSD values of 4.2-5.0% and detection limits ranging from 3.2 ng/L to 17.4 ng/L. PDMS sol-gels prepared without ILs provided RSD values of 2.8-14.1%, and detection limits ranging from 4.9 ng/L to 487.0 ng/L.