Stiffness and swelling characteristics of nanocellulose films in cell culture media

Nanocellulose is a material of interest for biomedical applications due to its morphological similarity with tissues’ own collagen. New cell culture substrates that mimic the human body tissue stiffness and extracellular matrix can be used to study cell behaviour in a way that is not possible for traditional plastic substrates. Five wood-based micro-and nanofibrillated cellulose films without additives were prepared to investigate the effects of nanocellulose charge density and fibril size on the mechanical properties of the films in liquids. Swelling behaviour of the films was studied in deionized water, in complete cell culture media (DMEM) and in CaCl2 solutions. Atomic force microscopy with a colloidal probe was used to measure Young’s modulus at the surface of the thin films submerged in the liquids. Cell culture media and CaCl2 solutions reduced the swelling of the films observed in deionized water, most probably due to a bridging effect by the calcium ions. The reduction was proportional to the charge of the particular nanocellulose. Young’s modulus in compression varied randomly on sample surfaces and appeared not to be directly related to topography of the films. In complete DMEM, the average Young’s modulus varied from 0.8 to 36.4 kPa, in the same stiffness range as two skin tissue layers, dermis and epidermis. Therefore, from mechanical properties point of view, these films seem suitable as cell culture substrates for skin tissue cells and could be used in skin tissue engineering.