Engineering macroporous hydrogels via the degradation of embedded microspheres

Typical hydrogels used in tissue engineering applications inhibit the diffusion of large molecular weight molecules, such as growth factors. The mass transport of these large molecular weight molecules is vital to cell viability within the gels. Macroporous hydrogels are a solution to this poor protein diffusion. However, current macroporous hydrogels are formed under harsh or toxic conditions limiting their application. This work outlines a procedure in which macroporous hydrogels are formed via the enzymatic degradation of embedded carboxymethyl cellulose (CMC) microspheres. These microspheres were formed via emulsion polymerization of methacrylated CMC using ammonium persulfate (APS) and N,N,N',N'-tetramethylethylenediamide (TEMED) as in initiator system. In addition, protein diffusion experiments were conducted using the model proteins, cellulase and bovine serum albumin (BSA), for both macroporous and control PEG-DM hydrogels. It was found that convective mass transport within the macropores dramatically increased the mass transport of these model proteins through the gels.