Self assembled temperature responsive surfaces for generation of cell patches for bone tissue engineering

One of the major challenges in the fabrication of tissue engineered scaffolds is the ability of the scaffold to biologically mimic autograft-like tissues. One of the alternate approaches to achieve this is by the application of cell seeded scaffolds with optimal porosity and mechanical properties. However, the current approaches for seeding cells on scaffolds are not optimal in terms of seeding efficiencies, cell penetration into the scaffold and more importantly uniform distribution of cells on the scaffold. Also, recent developments in scaffold geometries to enhance surface areas, pore sizes and porosities tend to further complicate the scenario. Cell sheet-based approaches for cell seeding have demonstrated a successful approach to generate scaffold-free tissue engineering approaches. However, the method of generating the temperature responsive surface is quite challenging and requires carcinogenic reagents and gamma rays. Therefore, here, we have developed temperature responsive substrates by layer-by-layer self assembly of smart polymers. Multilayer thin films prepared from tannic acid and poly N-isopropylacrylamide were fabricated based on their electrostatic and hydrogen bonding interactions. Cell attachment and proliferation studies on these thin films showed uniform cell attachment on the substrate, matching tissue culture plates. Also, the cells could be harvested as cell patches and sheets from the scaffolds, by reducing the temperature for a short period of time, and seeded onto porous scaffolds for tissue engineering applications. An enhanced cell seeding efficiency on scaffolds was observed using the cell patch-based technique as compared to seeding cells in suspension. Owing to the already pre-existent cell-cell and cell-extracellular matrix interactions, the cell patch showed the ability to reattach rapidly onto scaffolds and showed enhanced ability to proliferate and differentiate into a bone-like matrix.