Thin polymer layers formed by polyelectrolyte multilayer techniques on biological surfaces

Thin polymer films were formed on models of tissue surfaces using polyelectrolyte multilayer techniques, to evaluate the feasibility of using such techniques to build barrier materials onto the surfaces of tissues to improve postsurgical healing, or on the surfaces of tissue-engineered implants. By incubating heterogeneous surfaces with a polycation, followed by a polyanion, layers of polyelectrolyte were deposited onto the surfaces, as confirmed by ellipsometry and water contact angle measurement. Particularly favorable properties were found using the polyelectrolytes polylysine and alginate, which are capable of forming complex gels at physiologic pH; whereas others have demonstrated linear growth in film thickness, with this system, exponential growth was observed under certain conditions, which may be very useful in the coating of heterogeneous surfaces. Surfaces that were treated with multilayer techniques included gelatin, fibroblast extracellular matrix, and fibrillar type I collagen. All surfaces tested were highly heterogeneous and highly adhesive to cells before treatment. The formed thin polymer layers were found to be relatively bioinert, and the thicknesses of the assembles were found to be correlated with bioinertness, such that interactions of cells with the underlying proteinaceous surface could be prevented. The thickness of the polymer layers could be changed by increasing the number of bilayers adsorbed and also by changing the treatment and washing conditions so as to enhance the formation of complex gels.