Advanced guar gum/polyvinyl alcohol/CS-MnP smart hydrogel for promoting osteoblastic proliferation

Exposed bone fractures (EBFs) require multifunctional biomaterials capable of simultaneously providing structural adaptability, physicochemical stability, and biological support under dynamic physiological conditions. In this study, a smart multi-network hydrogel (HD hydrogel) composed of guar gum, polyvinyl alcohol, gelatin, collagen, tannic acid, and manganese phosphate/chitosan organo-inorganic complex (CS-MnP) was developed and compared with a Control hydrogel lacking the bioactive components. CS-MnP exhibited spherical and quasi-spherical morphologies with an average diameter of 232 nm ± 70 nm by SEM, aZ-average of 160 nm, and a multimodal nanoscale distribution by DLS. FTIR and EDS analyses confirmed phosphate incorporation and interactions between Mn-containing species and chitosan functional groups. The HD hydrogel exhibited enhanced physicochemical and rheological performance compared with the Control hydrogel, including porosity (0.85-0.88 vs 0.75-0.82), improved water absorption (47.16% vs 40.38%), faster self-healing (40-90 s vs ∼3 min), and superior rheological recovery (90%-95% modulus restoration after cyclic deformation). Furthermore, HD hydrogel maintained structural stability in PBS for up to 24 h, whereas the Control hydrogel underwent structural collapse before 8 h. Thermal resistance was also improved, with the HD hydrogel maintaining structural integrity up to ∼69 °C compared to ∼62 °C for the Control formulation, while also exhibiting enhanced low-temperature stability by resisting freezing down to -18 °C, compared to -16 °C for the Control hydrogel. Both hydrogels exhibited non-Newtonian shear-thinning behavior and high wettability (contact angle <20°). Cytocompatibility assay using MC3T3-E1 pre-osteoblast demonstrated cell viability values above 70%, while scratch assay revealed concentration-dependent modulation of cellular migration. Collectively, the synergistic integration of dynamic borate-diol crosslinking, hydrogel bonding, and CS-MnP-mediated interactions resulted in a mechanically adaptive, stimuli-responsive, and biologically compatible hydrogel system with promising potential as an auxiliary material for EBF treatment.