Multifunctional bio-composite hydrogels: PolyAMPs-tuned hydroxyapatite-PVA/gelatin systems development and characterization

Nanostructured biomaterials exhibit phenomenal functions that can be used in biomedical applications. Hydrogels, while biocompatible, often lack the desired mechanical strength. However, incorporating nanomaterials into a three-dimensional polymeric network significantly improved their mechanical and thermal properties, making them suitable for bioengineering applications. This study distinguishes itself by demonstrating a distinct structure-property relationship in which the systematic optimization of a poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PolyAMPS or PAMPS) and hydroxyapatitereinforced triple-network polymer system. It contributes in enhancing the functional properties within the hydrogel architecture, revealing how polymer composition and bioceramic content collectively govern a non-conventional mechanism driven by polymer-ceramic interactions. In this study, a composite design was used to optimize the effect of the conductive material PAMPS on the mechanical strength of the polyvinyl alcohol (PVA)/Gelatin blend. The hydroxyapatite-modified triple-network nanocomposite hydrogel films (HA-TNNCH) were prepared by solution casting. The triple-network hydrogel (TNH), comprising PAMPS/PVA/Gelatin, demonstrated superior mechanical strength (71.34 MPa) at an optimized formulation of PAMPS (4 v/v%): PVA (7 w/v%): gelatin (3 w/v%). The incorporation of PAMPS introduces strong ionic interactions and physical crosslinking within TN architecture. Multiple HA concentrations (0.025 g, 0.050 g, 0.10 g, and 0.150 g) were tested to assess the effect on the physicochemical properties of the optimized TNH. A 0.10 g loading of HA NPs into the TNH increased the tensile strength of the HA-modified TNNCH films from 71.34 MPa (TNH) to 77.4 MPa. The independent variables, like polymer and nanoparticle concentrations, affect dependent variables, including swelling properties at various pH levels. However, HA NPs also shifted the contact angle to a slightly higher hydrophilic value (55.62°) upon incorporation of 0.025 g of HA compared to pristine TNH. The nanocomposite hydrogel exhibited an optimal water-holding capacity (SR = 267.3 %) at pH 9.0, compared to the pristine TNH. Increased swelling ratio upon HA reinforcement led to greater free volume and increased water affinity within the TNH. The prepared hydrogel and its nanocomposites were characterized using different analytical techniques. X-ray Diffraction confirmed the presence of crystalline HA phases within the hydrogel composite. Fourier Transform Infrared Spectroscopy confirmed the characteristic functionality of the nanocomposite hydrogel. Scanning Electron Microscopy revealed the porosity and successful incorporation of HA nanoparticles into TNH. The successful formation of TNH and HA-TNNCH was supported by mechanical testing using a Universal Testing Machine, which indicated crosslinking and load transfer. The reported nanocomposite hydrogel is a potential biomaterial for bone regeneration.