Two-photon engineered polymer scaffolds for 3D migration studies

Presentation Date: 

Wednesday, November 29, 2006

Location: 

MRS Fall Conference 2006 (Cambridge, MA)
In tissue engineering, control of ligand-receptor-mediated interaction between cell and material is an underlying principle for designing biomaterials. Microfabrication techniques such as soft lithography have enabled researchers to study cell behavior extensively in two dimensions (2D) by controlling the spatial distribution of ligands on a micrometer and sub-micrometer scale. However, lack of an appropriate three-dimensional (3D) microfabrication technique with micrometer resolution has prevented from presenting cell adhesion ligands in an organized fashion in 3D. Thus, fabricating such a spatially selective 3D matrix that mimics the extracellular environment more than a 2D flat substrate is important to do a systematic study of various cell phenomena like cell spreading, adhesion, migration and proliferation. We fabricate three-dimensional polymer scaffolds by two-photon absorption (2PA) polymerization in an acrylic based resin caused by a tightly focused femtosecond laser beam. Upon simultaneous absorption of two photons by the photoinitiator, the resin undergoes a phase change from liquid to solid. Since this non-linear absorption is confined to the focal volume, three-dimensional microstructures can be fabricated by scanning the laser beam in the resin with a desired pattern. The resin used for 2PA polymerization consists of two triacrylate monomers and an acyl phosphine oxide photoinitiator. The latter absorbs two photons in the infrared and efficiently induces free radical polymerization process at the focal point. We use host-guest chemistry to functionalize resin with peptides, whose sequence can be varied to have specific interaction with cells. The triacrylate monomer is blended with a polypeptide containing an amino acid sequence of arginine-glycine-aspartate, which is known to promote cell adhesion. Microstructures with and without peptide are then made by 2PA polymerization. The adhesion of NIH-3T3 fibroblast cells on peptide treated and untreated structures, is investigated for spatial selectivity in three-dimensions using confocal microscopy. The use of two-photon absorption polymerization to fabricate peptide-functionalized microstructures opens the doors to new opportunities for investigation of cell migration in three dimensions.