AVS 52nd International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI-MoP

Paper BI-MoP40
In Situ Optical Characterization of an Electrodeposited Biopolymer Film

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Biomaterial Interfaces Poster Session
Presenter: S.B. Beatty, University of Maryland
Authors: S.B. Beatty, University of Maryland
J.J. Park, University of Maryland
E.C. Dreyer, University of Maryland
G.W. Rubloff, University of Maryland
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We have previously demonstrated spatially selective, voltage-programmable deposition of the polysaccharide chitosan onto patterned electrodes in low pH solution. We have previously shown that chitosan, an amine rich biopolymer, serves as a useful platform for coupling and conjugation of biomolecules as well as a platform for bioassays and enzymatic catalysis. We have developed an optical reflectivity technique for real-time, in-situ monitoring of the electrodeposition process, demonstrated in a combinatorial deposition cell in concert with real-time electrical (current, voltage) and environmental (pH, temperature) measurements. A beam splitter separates a HeNe laser beam into a reference beam and an incident beam onto the electrodeposition surface in solution. A chopper separates the reflected beam from the surface and the reference beam in time, while both impinge on the same reversed bias Si photodetector. The resulting signal is analyzed to extract the ratio of reflected to reference beam intensities, averaged over an appropriate portion of the chopper period, providing a real-time measure of the reflectivity. Chitosan deposition on the Au electrode decreases reflectivity by about 16% for 1 micron chitosan thickness, with noise levels suggesting a thickness sensitivity of 60nm. Film growth rates vary with current density as seen in reflectivity and confirmed by ex-situ post-process characterization using profilometry and AFM. The reflectivity indicates three stages in chitosan film growth. We plan to extend the technique for use in a confocal optical microscope so that dynamic behavior at active bioreaction sites in a microfluidic network can be monitored.