Hofmeister effect enhanced SiO₂/gelatin-based hydrophobically associated hydrogels and their lubricating properties

In recent years, hydrogel materials with suitable energy dissipation mechanisms and excellent mechanical properties have attracted much attention in tissue engineering due to their ability to mimic the natural cartilage structure. However, in cartilage tissue's regeneration and repair process, hydrogel materials should also possess satisfactory lubrication properties and biocompatibility. Therefore, preparing biocompatible low friction, high toughness hydrogels remain a challenge. In this paper, a new strategy is proposed to use gelatin, acrylamide (AM), lauryl methacrylate (LMA) and SiO₂ to construct hydrophobically associated hydrogels, where gelatin was used as an emulsifier and SiO₂ was used to a nano-enhanced filler. Then the Hofmeister effect enhanced SiO₂/gelatin-based hydrophobically associated hydrogels were prepared by one-step immersion in ammonium sulfate solution. The results showed that the strong "salting out" effect of ammonium sulfate solution on gelatin led to further enhancement of the hydrophobic interactions between gelatin molecular chains, which significantly improved the mechanical properties and lubrication ability of the hydrogels. Furthermore, Calcein AM-PI fluorescent staining and haemolysis assays showed that the hydrogel had low cytotoxicity and good haemocompatibility, and ELISA and scratch assays confirmed the positive regulatory effect of the hydrogel on normal cell growth. The Hofmeister effect-enhanced SiO₂/gelatin-based hydrophobically associated hydrogels have potential applications in articular cartilage repair.