PNIPAAm-Grafted-Collagen as an Injectable, In Situ Gelling, Bioactive Cell Delivery Scaffold

We synthesized two thermoresponsive, bioactive cell scaffolds by decorating the backbone of type I bovine collagen with linear chains of poly(N-isopropylacrylamide) (PNIPAAm), with the ultimate aim of providing facile delivery via injection and support of retinal pigment epithelial (RPE) cells into the back of the eye for the treatment of retinal degenerative diseases. Both scaffolds displayed rapid, subphysiological phase transition temperatures and were capable of noninvasively delivering a liquid suspension of cells that gels in situ forming a cell-loaded scaffold, theoretically isolating treatment to the injection site. RPE cells demonstrated excellent viability when cultured with the scaffolds, and expulsion of cells arising from temperature-induced PNIPAAm chain collapse was overcome by incorporating a room-temperature incubation period prior to scaffold phase transition. These results indicate the potential of using PNIPAAm-grafted-collagen as a vehicle for the delivery of therapeutic cells to the subretinal space.