pH-Responsive Hydrogel Microspheres for Electrostatic Protein Adsorption and Hydrolysis of Organophosphorus Compounds.
Starger, Jesse L.
- I examined the facile fabrication and utilization of porous poly(acrylamide-co-acrylic acid) (p(AAm-co¬-AA)) hydrogel microspheres as a platform for the electrostatic adsorption and pH-responsive release of proteins. Hydrogel microspheres are ideal for various biological applications due to their non-fouling, biologically inert, and solution-like kinetic properties. Micromolding-based fabrication ... read moreof microspheres is a simple, robust, and inexpensive method that offers several advantages over emulsion or microfluidic schemes. Monodisperse microspheres are fabricated via surface tension-induced droplet formation and photoinduced radial polymerization in poly(dimethylsulfoxide) (PDMS) molds. In this study, bovine serum albumin (BSA) (M.W. 66.5 kDa) is enlisted as a model protein to examine the electrostatic binding and pH responsiveness of the p(AA-co¬-AAm) microspheres using Coomassie Brilliant Blue G-250 dye as an indicator. I found that the adsorption of proteins occurs when the pH of solution remains between the isoelectric point (pI) of the protein and the pKa of the carboxylic acid sites in the microspheres. Similarly, I applied the same method to characterize the adsorption, release, stability, and activity of organophosphorus hydrolase (OPH, M.W. 72 kDa), an important enzyme for the degradation of toxic organophosphorus compounds in pesticides and chemical warfare agents. Additionally, via EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide(NHS)) chemistry, I compared the results of the electrostatically bound OPH to the results of covalently conjugated OPH. These results demonstrate a pH-responsive system for a large range of application areas including hazardous waste and environmental remediation.read less