TiO₂, CeO₂, and TiO₂-CeO₂ nanoparticles incorporated 2.5D chitosan hydrogels: Gelation behavior and cytocompatibility

In this study, gelation behavior and cytocompatibility of 2.5D chitosan hydrogels were investigated in the presence of TiO₂, CeO₂ and TiO₂-CeO₂ composite nanoparticles. Chemical co-precipitation method was used for nanoparticle synthesis and they were heat treated at 600 °C and 700 °C. Gelation of the chitosan solutions was carried out at 37 °C in the presence of glycerol phosphate and genipin as crosslinkers. The gelation time of chitosan was decreased by all of the nanoparticles whereas its elastic modulus was increased by nanoparticles addition. Chitosan solutions containing CeO₂ or TiO₂-CeO₂ nanoparticles showed faster gel formation compared to chitosan solutions containing only TiO₂ nanoparticles. CeO₂@700 °C nanoparticles decreased the gelation time by 46% and increased elastic modulus by 14%. Average pore diameter of the hydrogel decreased from 127 ± 62 μm to 77 ± 33 μm, water uptake decreased 21% and thermal stability increased in the presence of CeO₂@700 °C nanoparticles compared to chitosan hydrogel. Cell viability results indicated that chitosan hydrogels with or without nanoparticles created 2.5D environment supporting cellular proliferation approximately 1.5 times more than TCPS due to their high porous surfaces. Immunofluorescence images were also supported cell viability results. Therefore, CeO₂ or TiO₂-CeO₂ composite nanoparticles incorporated 2.5D chitosan hydrogels may be alternative tissue engineering materials with their fast gelation, ease of use, low cost, light transparency, and cytocompatibility.