Characterization of Electrodeposited Chitosan: an Interfacial Layer for Bio-assembly and Sensing

Abstract

Microfluidics and Lab-on-a-Chip devices have revolutionized the field of analytical biology. To fully optimize the potential of the microfluidic environment it is critical to be able to isolate reactions in specific locations within a channel. One solution is found using chitosan, an amine-rich biopolymer with pH responsive solubility. Induction of hydrolysis at patterned electrodes within the fluidic channel provides a means to spatially control the pH, thus enabling biochemical functionalization that is both spatially and temporally programmable. While chitosan electrodeposition has proven to be reliable at producing films, its growth characteristics are not well understood. In situ optical characterization methods of laser reflectivity, fluorescence microscopy and Raman spectroscopy have been employed to understand the growth rate inter diffusion and lateral resolution of the deposition process. These techniques have also been implemented in determining where a molecule bound to an amine site of the polymer is located within the film. Currently, electrodeposited chitosan films are primarily used for tethering of biomolecules in the recreation of metabolic pathways. Beyond just a biomolecular anchor, chitosan provides a way to incorporate inorganic nanoparticles. These composite structures enable site-specific sensors for the identification of small molecules, an important aspect to many Lab-on-a-Chip applications. New methods for creating spatially localized sites for surface enhanced Raman spectroscopy (SERS) has been developed. These methods have been optimized for particle density and SERS enhancement using TEM and Raman spectroscopy. Through optimization, a viable substrate with retained chitosan amine activity capable of integration into microfluidics has been developed.