(585am) 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.