Porous and Chemically Functional Polymeric Hydrogel Microspheres for Improved Biomacromolecular Conjugation

Porous and chemically functional polymeric hydrogel microspheres for improved biomacromolecular conjugation

Eric Liu, Sukwon Jung, Chang-Hyung Choi² and Hyunmin Yi¹

 

¹ Department of Chemical and Biological Engineering, Tufts University

4 Colby St. Medford, MA 02155 USA

hyunmin.yi@tufts.edu, (TEL) 617-627-2195

² Cosmetic Science and Technology Division, Daegu Haany University

1 Haanydaero, Gyeongsan-si, Gyeongsangbuk-Do, Korea (Zip code 712-715)

changhyung.choi@gmail.com (TEL) 82 053 819 7721

Suspension arrays of biofunctionalized polymeric hydrogel microparticles hold significant potential for rapid and reliable biosensing and biodiagnostics, yet there exist several critical hurdles in the existing fabrication technologies.  We demonstrate a robust and tunable micromolding method to fabricate chemically functional poly(acrylamide-co-acrylic acid) (p(AAm-co-AA)) hydrogel microspheres with uniform dimensions and controlled porous network structures.  The inherently batch processing-based nature of our micromolding process offers several distinct advantages over microfluidic fabrication processes; for example accommodating a variety of fabrication parameters including monomer systems with slow polymerization rates, without the need for surfactants, delicate flow control, or viscosity tuning.  The p(AAm-co-AA) microspheres with abundant carboxylate functional groups are fabricated via surface tension-induced droplet formation in patterned poly(dimethylsulfoxide) (PDMS) molds and photo-induced radical polymerization.  To demonstrate chemical functionality, we enlisted a rapid EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS)) chemistry for fluorescent labeling of the microspheres with a small molecule dye fluorescein glycine amide.  Epifluorescence imaging and image analysis illustrate the uniform incorporation of carboxylate groups within the microspheres and rapid kinetics without diffusion limitation.  Furthermore, confocal imaging of the conjugation of the p(AAm-co-AA) microspheres with fluorescent protein R-phycoerythrin (M.W. 240 kDa, D_h ~11nm) demonstrate the highly porous nature of the microspheres as well as the utility of the microspheres and the EDC/NHS scheme for facile biomacromolecular conjugation and rapid biosensing.  Finally, we also report our recent results on thorough investigation on the effects of two potent conjugation handles, namely AA and a potent aminopolysaccharide chitosan, on the pH-dependent conjugation efficiency, mesh size and biomacromolecular conjugation kinetics of the hydrogel microspheres fabricated via a rapid microcapillary device technology.  Here, we utilized simple size-based multiplexing to further demonstrate orthogonal one-pot conjugation of multiple proteins on microspheres with either AA or chitosan conjugation handles.  Combined, these results illustrate significant potential for our fabrication-conjugation strategy in the development of biofunctionalized polymeric hydrogel microspheres toward rapid biosensing, bioprocess monitoring, and biodiagnostics.