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Biosensors & Chemical Analysis (Publications)

Multiplexed In Vitro Selection Of Aptamers Using Nanoporous Sol-Gel Arrays With Integrated Microheaters

Our current methodology utilizes nanoporous silica-based sol-gel droplets to confine different target proteins in microfluidic chambers that are arrayed at specific positions along a micro-channel. Sol-gel is not only suitable for immobilization of large amounts of proteins in a 3-dimensional environment, but also allows protein-nucleic acid interactions. In this study, we created a SELEX-on-a-chip device harboring an array of sol-gel droplets with separate microheaters built underneath each droplet for multiplex binding and partitioning steps of the SELEX procedure. Sol-gel droplets allow the competitive binding of nucleic acid aptamers to different target proteins in each droplet, while the microheaters provides local heating to disrupt aptamer-protein interaction and allow selective elution of aptamers from each droplet.

Prion Protein Detection with Nanomechanical Resonators

Arrays of micromechanical resonators were fabricated and used as biosensors for detecting prion proteins, that when over-produced cause Mad Cow Disease and similar diseases in sheep (Scrapie) and humans (Creutzfeldt-Jakob Disease). In order to improve sensitivity to very low concentrations of prions, a nanoparticle-based technique was used to essentially make the prions heavier, and easier to detect with the resonators. This research was published by Madhukar Varshney et al. in the journal Analytical Chemistry DOI:10.1021/ac702153p

Integration of Microfluidics to Electrospray Ionization Mass Spectrometry Using a Chip-Embedded SU-8 Eectrospray Tip

We present two methods for creating polymeric microfluidic devices integrated with electrospray tips for use with mass spectrometry. SU-8 was used to create microfluidic channels and electrospray tips. The planar electrospray tips were located at the end of microfluidic channels and were formed using standard photolithography. The encapsulation of the microfluidic channels was accomplished by using thermal and press bonding between two SU-8 layers, or by employing a sacrificial layer removal technique. We successfully coupled these microfluidic chips to a mass spectrometer. In particular, the microfluidic device fabricated with the sacrificial layer removal method shows satisfactory electrospray stability.