Gene-modified cell detachment on photoresponsive hydrogels strengthened through hydrogen bonding.

Photoresponsive hydrogels are potentially useful as drug delivery and cell culture media, but there has been no report on manipulation of cell attachment/detachment and gene transfection simultaneously on the surface of this single gel. In the present study, strong light sensitive hydrogels were prepared mechanically by photoinitiated copolymerization of spiropyran-containing monomer, 2-vinyl-4,6-diamino-1,3,5-triazine, hydrogen bonding monomer, oligo(ethylene glycol) methacrylate and polyethylene glycol diacrylate (PEGDA, Mn=575). The multiple hydrogen bondings of diaminotriazine residues could contribute to the increase in compressive strengths of the photosensitive hydrogels up to 5.1MPa. UV (365nm) irradiation led to detachment of adhered cells as a result of the increased surface hydrophilicity caused by a switch from hydrophobic spiropyran to hydrophilic merocyanine form. Furthermore, selective detachment of cells could also be achieved by UV light illumination on the specified gel surface. Hydrogen bonding between diaminotriazines were shown to tightly anchor the PVDT/pDNA complex particles on the gel surface, where reverse gene transfection was achieved. Following up with UV irradiation triggered the unharmful detachment of gene-modified cells from the gel surface. It is envisioned that this photosensitive hydrogel holds potential as a versatile platform for operating gene delivery and controlled harvest of desired cells for tissue engineering.