Thermo-Responsive PNiPAAm-g-PEG Films for Controlled Cell Detachment

Abstract

A series of graft copolymers consisting of either poly(N-isopropylacrylamide) (PNiPAAm) or poly(N,N-diethylacrylamide) (PDEAAm) as a thermo-responsive component in the polymer backbone and poly(ethyleneglycol) (PEG) were immobilized as thin films and cross-linked on a fluoropolymer substrate using low-pressure argon plasma treatment. The surface-immobilized hydrogels exhibit a transition from partially collapsed to completely swollen, which is in the range of 32-35 degrees C and corresponds to the lower critical solution temperature of the soluble polymers. The hydrogels were used as cell carriers in culture experiments with L929 mouse fibroblast cells to probe for cell adhesion, proliferation, and temperature-dependent detachment of cell layers. The fibroblast cells adhere, spread, and proliferate on the hydrogel layers at 37 degrees C and become completely detached after reducing the temperature by 3 K. The cell release characteristics were further correlated to the swelling and collapsing behavior of the hydrogel films and the polymer solutions as measured in PBS solution and RPMI cell cultivation medium. It could be shown that, long before the swelling has completed upon temperature reduction, the cells detach. This can be attributed to the large content of PEG present in the hydrogel, which weaken the cell adhesion strength to the hydrogel layers.

Electron beam immobilization of functionalized poly(vinyl methyl ether) thin films on polymer surfaces – Towards stimuli responsive coatings for biomedical purposes

“…Both facts set apart PVME from PNiPAAm and NiPAAm containing copolymers as investigated in previous studies [4,21]. The influence of the cell culture medium to the transition behavior is expected to lower the transition temperature by 1-2 K [22]. The shown behavior of PVME thin films on polystyrene substrates corroborate the results of Hegewald et al [23] obtained for thicker layers of PVME directly prepared on silicon oxide surfaces.…”

Detachment of human endothelial cell sheets from thermo-responsive poly(NiPAAm-co-DEGMA) carriers

“…Experiments with L929 mouse fibroblasts, a simple and well-known cell line, were carried out on poly(NiPAAm-co-DEGMA) to ensure the comparability with previous studies on different thermoresponsive materials [9,10]. At 37°C cells adhere, spread, proliferate and reach confluence after 48 h (Figure 3 left) as observed on standard T25 cell culture dishes.…”

“…The resulting coatings respond with swelling and collapsing to small changes in the environmental temperature and can be used as cell culture carriers for harvesting cells and cell sheets without enzymatic or mechanical treatments [7][8][9][10]. Vascular endothelial cells receive a lot of attention in tissue engineering strategies as they mediate the interaction of flowing blood with other tissues [11].…”

Controlled Surface Initiated Polymerization of N‐Isopropylacrylamide from Polycaprolactone Substrates for Regulating Cell Attachment and Detachment

“…[51] However, if the RGD was attached to the middle section of the PMAA brush, cells were found to adopt a rounded morphology and focal adhesions concentrated toward the internal part of the cell. [51] Besides the already mentioned non-biofouling and cell adhesive brushes, there are also brushes that can be used to tune the cellular behavior, for instance by employing thermoresponsive polymers such as, PNIPAM [4][5][52][53][54][55][56] and poly(2-(2-methoxyethoxy)ethyl methacrylate-cooligo(ethylene glycol) methacrylate) (P(MEO 2 MA-co-OEGMA)). [52][53][54][57][58][59][60][61][62][63] These two polymers trigger a different cellular response above and below their critical solution temperature (LCST) due to a change in chain conformation and variations in intra-and intermolecular interactions around the LCST in these polymers.…”