Nanohydroxyapatite Reinforced Chitosan Composite Hydrogel with Tunable Mechanical and Biological Properties for Cartilage Regeneration

B Y Santosh Kumar,G C Mohan Kumar,Arun M Isloor,Abdullah M Asiri,Inamuddin Inamuddin

doi:10.1038/s41598-019-52042-7

Abstract

With the continuous quest of developing hydrogel for cartilage regeneration with superior mechanobiological properties are still becoming a challenge. Chitosan (CS) hydrogels are the promising implant materials due to an analogous character of the soft tissue; however, their low mechanical strength and durability together with its lack of integrity with surrounding tissues hinder the load-bearing application. This can be solved by developing a composite chitosan hydrogel reinforced with Hydroxyapatite Nanorods (HANr). The objective of this work is to develop and characterize (physically, chemically, mechanically and biologically) the composite hydrogels loaded with different concentration of hydroxyapatite nanorod. The concentration of hydroxyapatite in the composite hydrogel was optimized and it was found that, reinforcement modifies the hydrogel network by promoting the secondary crosslinking. The compression strength could reach 1.62 ± 0.02 MPa with a significant deformation of 32% and exhibits time-dependent, rapid self-recoverable and fatigue resistant behavior based on the cyclic loading-unloading compression test. The storage modulus value can reach nearly 10 kPa which is needed for the proposed application. Besides, composite hydrogels show an excellent antimicrobial activity against Escherichia coli, Staphylococcus aureus bacteria’s and Candida albicans fungi and their cytocompatibility towards L929 mouse fibroblasts provide a potential pathway to developing a composite hydrogel for cartilage regeneration.

Highlights

Hydrogel, a three-dimensional cross-linked hydrophilic polymer network owing to the similarity in the structure and some attributes of soft tissue is widely used to develop scaffolds for tissue engineering[7,8]
The swelling strength could decrease as a function of hydroxyapatite indicating that reinforcement influences the additional crosslinking and it was verified by FTIR spectra
An essential improvement in the mechanical properties was found when Hydroxyapatite Nanorod (HANr) was incorporated into the CS matrix and the best results were found in CS/1.5HANr www.nature.com/scientificreports composite gels

Summary

Introduction

A three-dimensional cross-linked hydrophilic polymer network owing to the similarity in the structure and some attributes of soft tissue is widely used to develop scaffolds for tissue engineering[7,8]. One way to improve the mechanobiological characteristics of HAp is developing one-dimensional Hydroxyapatite Nanorod (HANr) This nanorod morphology favors the adhesion and proliferation of osteoblast and increase alkaline phosphatase activity of marrow stromal cells[25]. In view of the same, it was planned to prepare the hydroxyapatite nanorod from cuttlefish bone through the mechanochemical method and chitosan was blended with HANr to match the requirements. This CS/HANr composite network system provides state-of-the-art, where a part of the polymeric network tries to improve biocompatibility and another part anchors mechanical strength. Stirring was continued for another 10 h and the slurry obtained was dried and calcined in a muffle furnace at 800 °C with a heating rate of 5 °C/min for 4 h

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Conclusion