Entrapment of Saccharomyces cerevisiae and 3T3 fibroblast cells into blue light cured hydrogels Swati Mishra, 1 Frank J. Scarano, 2 Paul Calvert 1 1 Department of Bioengineering, University of Massachusetts Dartmouth, N. Dartmouth, Massachusetts 02747 2 Department of Medical Laboratory Science, University of Massachusetts Dartmouth, N. Dartmouth, Massachusetts 02747 Received 23 February 2012; accepted 7 March 2012 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.a.34204 Abstract: Hydrogels, containing yeast cells or fibroblast cells, were fabricated using blue light-induced polymeriza- tion technique. The cell-loaded prepolymer formulation was comprised of poly(ethyleneglycol) diacrylate (more than or equal to 50% v/v), 0.5 wt % Eosin Y and 0.5 wt % triethanola- mine as the base oligomer, photo-initiator, and co-initiator, respectively. The two model cell lines, Saccharomyces cere- visiae and NIH 3T3 fibroblasts maintained high viability pre- and post-processing. Several bioassays have demonstrated the unaffected intracellular and extracellular activities of the cells entrapped within the hydrogels. Scanning electron microscopy confirmed the proliferation of S. cerevisiae cells that were entrapped and cultivated for 48 h in growth media, which validated the favorable microenvironment and nutrient transport in these gels. Upon entrapment, fibroblast cells remain viable upto 12 h, however they failed to attach within the crosslinked network, thus no further proliferation was observed. The tunable properties of this hydrogel system project it as a useful matrix for specialized biohy- brids. V C 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A:000–000, 2012. Key Words: blue light, polyethylene glycol diacrylate, S. cere- visiae, immobilization, hydrogels How to cite this article: Mishra S, Scarano FJ, Calvert P. 2012. Entrapment of Saccharomyces cerevisiae and 3T3 fibroblast cells into blue light cured hydrogels. J Biomed Mater Res Part A 2012:00A:000–000. INTRODUCTION Immobilized cell technology has been exploited for various applications including industrial bio-transformations, 1 pro- duction of peptide antibiotics, 2 detoxification of biochemi- cals, 3 water and air purification, 4 medical analytics, and clin- ical diagnostics. 5 Compared to free cells, the immobilization of cells allows convenient operation for long-term applica- tions as well as better recovery of the support, stability, reusability, and volumetric productivity. 6 The cells may be attached to a scaffold or carrier surface, trapped within a scaffold with a pore size much smaller than the cell dimen- sions or embedded within a soft gel matrix. 7 A widely used batch production technique involves tank fermentation of animal cells attached to circulating micro- bead carriers. This provides for the attachment-dependence of the cells and at the same time allows rapid exchange with the bulk fluid. For many small-scale applications, it would be more attractive to use a static scaffold with entrapped cells and fluid channels, modeled on an organ such as the pancreas. The cells are thus confined in a dis- crete phase that allows exchange of nutrients, oxygen, and metabolic waste with the bulk phase without direct con- tact. 8 This approach has been explored in various areas of medical science, for example, treatment of diabetes, 9 pro- duction of biologically important chemicals, 10 evaluation of anti-human immune deficiency virus (HIV) drugs, 11 produc- tion of monoclonal antibodies, 12 and development of bio-ar- tificial liver. 13 Entrapment in a hydrogel matrix is attractive because the cells are protected from contamination by microorgan- isms and the gel can be tuned to control what molecules reach the cells. Some fundamental requirements of such kind of hydrogel matrices include good permeability, hydro- philic character, chemical, mechanical and thermal stability, and insolubility in the liquid environment. 14 Ideally, hydro- gels can be viewed as a crosslinked solution of water-solu- ble polymer. In this case, the chain length between cross- links will determine the cut-off size for molecules diffusing through the gel, but this chain length will usually have a broad distribution. Nano-size pores (1–10 nm) in highly crosslinked hydrogels permit the diffusion of small mole- cules, such as glucose, oxygen, and enzyme substrates while preventing the escape of larger molecules like whole cells and enzymes. This phenomenon has been utilized in the de- velopment of immune-protective implants where immunoi- solation is a primary consideration. 15 Many gels also have a two-phase structure arising from local micro-crystallization or ordering or from phase separation during gelation. This Correspondence to: S. Mishra; e-mail: swatimishra.iitd@gmail.com Contract grant sponsor: National Textile Center; contract grant number: F06-MD14 V C 2012 WILEY PERIODICALS, INC. 1