Ultra-thin spin coated crosslinkable hydrogels for use in cell sheet recovery-synthesis, characterisation to application

The advantages of detaching adherent cells from thermoresponsive platforms over conventional cell detachment protocols has been well documented. This study focuses on the development of an alternative method to produce thermoresponsive surfaces for cell and cell sheet regeneration to already established techniques which are complex and expensive and may be inaccessible to many laboratories. A photcrosslinkable poly-N-isopropylacrylamide (pNIPAm) copolymer was synthesised and thin films of the copolymer were deposited using the operationally simple spin coating technique which were subsequently crosslinked upon exposure to ultraviolet (UV) irradiation. Characterisation of hydrogel properties and behaviour was achieved using UV spectroscopy, atomic force microscopy (AFM), advancing contact angle, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and white light interferometry analyses. Results indicate that 3T3 fibroblast cells adhere and proliferate to confluence on hydrogels of <30 nm thickness similar to controls but cell attachment onto hydrogels of >30 nm was comparatively poor. Confluent cell sheets were harvested from the sub 30 nm ultra-thin hydrogels upon temperature reduction within 10 min. Spin coating allows for the facile control of film thickness via variation of the depositing polymer solution concentration and therefore the routine fabrication of ultra-thin hydrogels capable of hosting cells to confluence is easily achievable.