*Article* **Hydroxyapatite Reinforced Polyvinyl Alcohol/Polyvinyl Pyrrolidone Based Hydrogel for Cartilage Replacement**

**Mallikarjun B. Jalageri \* and G. C. Mohan Kumar \***

Polymer Composites Laboratory, Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore 575025, India

**\*** Correspondence: mallikarjunbjalageri.187me008@nitk.edu.in (M.B.J.); mkumargc@nitk.edu.in (G.C.M.K.)

**Abstract:** Polyvinyl alcohol (PVA) and Polyvinyl Pyrrolidone (PVP) hydrogels are desirable biomaterials for soft tissue repair and replacement. However, the bio-inertness and poor cell adhesive potency of the PVA and PVP hinder the wide range of biomedical applications. In the present work, PVA and PVP were blended with a one-dimensional hydroxyapatite nanorod (HNr), and PVA/PVP/HNr composite hydrogel was synthesized by the freeze-thaw process. The developed hydrogels were characterized by Scanning Electron Microscope (SEM). The bio-ceramic nanohydroxyapatite content was optimized, and it was found that reinforcement improves mechanical strength as well as bioactivity. The compression strength values are 2.47 ± 0.73 MPa for the composite having 2 wt% of nanohydroxyapatite. The storage modulus was much higher than the loss modulus, which signifies the elastic dominancy similar to cartilage. Besides, the antimicrobial activity of nanohydroxyapatite reinforced PVA hydrogel towards bacterial species, *Escherichia coli* (*E. Coli*), *Staphylococcus aureus* (*S. aureus*) was satisfactory, and the in vitro biocompatibility response towards Human Mesenchymal stem cells(hMSC) after 72 h of culture confirms nanohydroxyapatite reinforced PVA/PVP hydrogels are the promising alternatives for next-generation cartilage substitutes.

**Keywords:** biomaterial; ceramic; freeze-drying; polymer; tissue
