Cell harvesting on robust smart thermosensitive pseudo-double networks prepared by one-step procedure

• The pseudo-ordered hydrogels obtained are based on thermosensitive poly vinyl caprolactam (pVCL) and were successfully functionalized with hydrophobic unit by copolymerization with hexyl methacrylate (HMA) in molar percentages ranging between 0 and 23.2. • Tough-thermosensitive hydrogels that simulate the compositional asymmetry of double network (DN) hydrogels were obtained in a single-step due to the difference in reactivity of the precursors used (methacrylates vs. vinyl lactams). • As the HMA content increases, the obtained hydrogels show gradual lower thermosensitivity and swelling capacity to the detriment of higher transparency and strength. These systems reached an elastic modulus in compression mode higher than 1 MPa with 5 mol % HMA and with a water content close to 60 % at 20 °C, giving rise to "ultra-stiff" hydrogels. • The evaluated samples have shown cytocompatibility with the C2C12-GFP cell line with a progressive delay in terms of cell proliferation with the increasing hydrophobicity of the hydrogels. • Hydrogels obtained with percentages lower than 3 mol % HMA showed similar cell proliferation and cell detachment capability as the control hydrogel, while higher percentages on the basis of their exceptional mechanical properties suggest the possibility of their application in implants for regeneration of demanding tissues. In this work, pseudo-double networks (pseudo-DN) based on N- vinyl caprolactam (VCL, major component, precursor of thermosensitive chains) and hexyl methacrylate (HMA, minor component, hydrophobic) have been prepared by using single step approach. The adjective pseudo refers to the fact that through the simultaneous copolymerization of VCL and HMA with different relative reaction kinetics, in the presence of an appropriate mixture of crosslinkers, networks with complex structures that tend towards DN-type structures are obtained. Hydrogels have been prepared with HMA/VCL molar ratios from 0 to 23.2 mol %. The series of hydrogels prepared show a composition-dependent behaviour in terms of thermosensitivity, swelling at temperatures below the Volume Phase Transition Temperature (VPTT) value, mechanical properties and performance during the cell culture experiments. More precisely, hydrogels with low percentages of HMA show elastic moduli under compression tests slightly lower than 1 MPa and presented a high thermal response (high swelling below the VPTT) allowing in addition the non-aggressive detachment of cell monolayer by controlled decrease of temperature. As the percentage of HMA increases, the elastic modulus increases, obtaining improved mechanical properties (reaching values in the range 1–3 MPa), thermosensitivity decreases (low swelling below VPTT) and a progressive delay in cell proliferation is also observed, being still cytocompatible. In this sense, hydrogels with low percentages of HMA (up 2.7 mol %) allow cell proliferation and transplantation similar to the control sample.