Sameer Singhal

Transmission SPR of Gold Nanoslit Array and Ultrasensitive Detection of a Retinol Binding Protein

Retinal-modified SAM-coated nanoslit array thin gold film was used for ultra-sensitive (picomolar) detection of a ligand protein (β-Lactoglobulin) with a transmission SPR mode. The transmission spectra of nanoslit arrays with varying periods were evaluated for nanostructure optimization with respect to primary peak position, shape and sensitivity. Sensitivity of this method, as measured in water, was estimated at 3 ng/mL, or approximately 130 picomolar. Additionally a monotonic shift in primary peak wavelength was observed with changing nanoslit periodicity. This type of in-plane nanoarray chip is currently being integrated with microfluidic platforms for chemical and/or biological sensing applications.

Enhancement of Electrochemical Performance of Bilirubin Oxidase Modified Gas Diffusion Biocathode by Porphyrin Precursor

Recent studies have focused on tailoring the catalytic currents of multicopper oxidase (MCO) enzymes-based biocathodes to enhance oxygen reduction. Biocathodes modified with natural substrates specific for MCO enzymes demonstrated drastic improvement for oxygen reduction. Performance of 1-pyrenebutanoic acid, succinimidyl ester (PBSE), and 2,5-dimethyl-1-phenyl-1H-pyrrole-3-carbaldehyde (Di-Carb) oriented bilirubin oxidase (BOx) modified gas diffusion biocathode has been highly improved by incorporating hematin, a porphyrin precursor as electron transfer enhancement moiety. Hematin modified electrodes demonstrated direct electron transfer reaction of BOx exhibiting larger O2 reduction in current density in phosphate buffer solution (pH 7.0) without the need of a mediator. A remarkable improvement in the catalytic currents with 2.5-fold increase compared to non-hematin modified oriented BOx electrodes was achieved. Moreover, a mediatorless and compartmentless glucose/O2 biofuel cell based on DET-type bioelectrocatalysis via the BOx cathode and the glucose dehydrogenase (GDH) anode demonstrated peak power densities of 1 mW/cm2 at pH 7.0 with 100 mM glucose/10 mM NAD fuel. The maximum current density of 1.6 mA/cm2 and the maximum power density of 0.4 mW/cm2 were achieved at 300 mV with nonmodified BOx cathode, while 3.5 mA/cm2 and 1.1 mW/cm2 of current and power density were achieved with hematin modified cathode. The performance improved 2.4 times which attributes to the hematin acting as a natural precursor and activator for BOx activity enhancement.

An In-Plane Nanofluidic Nanoplasmonics-Based Platform for Biodetection

This paper reports a new nanofluidic plasmonics-based sensing platform which can be readily integrated with microfluidics devices, and potentially enable an in-parallel transmission surface plasmon resonance (SPR), lab-on-chip sensing technology. The technology overcomes the current SPR size limitations through a combination of nanofluidics and nanoplasmonics in a rationally designed in-plane nanoslit array capable of concurrent plasmonic sensing and confined-flow for analyte delivery. This work is leveraged on our previous work of using nanoslit metal films for SPR sensing [1, 2], and the in-plane nanofluidic nanoplasmonic platform is different from recently reported nanohole-based nanofluidic plasmonics sensors [3, 4]. The work presented here includes an integrated device with nanofluidic nanoplasmonic arrays interfacing with microfluidic channels, and preliminary findings, from both theoretical and experimental fronts, of the device for bio-sensing.Copyright