(17c) Polyelectrolyte Multilayer Assembly of Elastin-like Polymer Conjugates for Creating Multilayered Cellular Architectures

Both tissue engineering and biological science will benefit from a generalized methodology to create multilayered cellular architectures that mimic tissue structures found in vivo. Our group has previously reported a novel approach to create in vitro multi-layered cellular constructs comprised of alternating layers of cells and biocompatible polyelectrolyte multilayer (PEM) scaffolds. Elastin-like polypeptides (ELPs) are tandemly-repeated polymers derived from a portion of the primary sequence of mammalian elastin. ELPs have previously been used for protein purification, nucleic acid delivery, and thermally-mediated targeting of solid tumors. We sought to exploit two compelling properties of recombinant ELPs, namely (1) precise control over macromolecular structure for site-specific chemical modification and (2) excellent biocompatibility, to produce layered cellular assemblies using PEMs composed of ELP-polyelectrolyte conjugates. The elastin-like polypeptide (GVGVP)40 was produced in E. coli and purified by the inverse temperature transition purification method. The ELP was conjugated with poly(acrylic acid) and poly(ethyleneimine) using standard carbodiimide activation chemistry. These conjugates were characterized by FTIR spectroscopy, mass spectroscopy, and the ninhydrin assay. These results demonstrate a reaction yield of 50%, with a conjugation ratio of 1:1, for both reactions. These conjugates were used to construct layered, three-dimensional hepatocyte-PEM-hepatocyte and hepatocyte-PEM-endothelial cell constructs. Hepatocyte-specific urea and albumin production were quantified under a variety of conditions. The ELP-PEM multilayers enhanced albumin and urea production by 2.5-fold and 1.5-fold, respectively, in hepatocyte-PEM-hepatocyte constructs. These results indicate that the ELP-PEMs may represent a promising class of biomaterials for a variety of tissue engineering applications.