Development of thermo-responsive polycaprolactone macrocarriers conjugated with Poly(N-isopropyl acrylamide) for cell culture.

Poly(N-isopropyl acrylamide) (PNIPAAm) is a well-known 'smart' material responding to external stimuli such as temperature. PNIPAAm was successfully conjugated to polycaprolactone (PCL) bead surfaces through amidation reaction. Functionalization steps were characterized and confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and Energy Dispersion Spectroscopy. PNIPAAm-conjugated PCL allowed human dermal fibroblast cells (HDF) and mesenchymal stem cells (MSC) to adhere, spread, and grow successfully. By reducing the temperature to 30 °C, more than 70% of HDF were detached from PNIPAAm-conjugated PCL macrocarriers with 85% viability. The cell detachment ratio by trypsin treatment was slightly higher than that induced by reduced temperature, however, cell detachment from PNIPAAm-conjugated macrocarriers by lowering the temperature significantly reduced cell death and increased both cell viability and the recovery potential of the detached cells. HDF attachment and detachment were also observed by Live-Dead staining and phase contrast imaging. The expression of extracellular matrix proteins such as Laminin and Fibronectin was also affected by the trypsinization process but not by the reduced temperature process. Taken together, our results showed that thermo-responsive macrocarriers could be a promising alternative method for the non-invasive detachment of cells, in particular for tissue engineering, clinical applications and the use of bioreactors.