Injectable Osteogenic and Antibacterial Pastes for Improved Bone Repair

Abstract

Bone defects and diseases have a huge impact on the human population worldwide. According to a report about 19% of Pakistan’s population have osteoporosis while 64% have osteopenia that can lead to osteoporosis. Accidents, sports trauma, ageing and pathogenic infections like osteomyelitis result in the need for bone repair and regeneration. Tissue engineering solutions that can be applied through minimally invasive intrusion are of special interest for the ideal filling of complex defects which avoids the harms and infections related to open surgery. For bone repair and regeneration synthetic hydroxyapatite (HA) based injectable bone substitutes are highly promising. Nano sized HA (Nano-HA) has significant osteogenic potential from the clinical viewpoint because of its high surface area to volume ratio. Both wet and dry techniques have been reported for the synthesis of hydroxyapatite. These traditional techniques are time consuming, often require strict over reaction parameters, and often need high temperatures (for post processing or synthesis) and expensive precursors. In this work HA was synthesized using a novel flow synthesis set up. It is a very convenient technique due to its ease of use, continuous and rapid manner and high yield ability. ZnO and Co-precipitated HA-ZnO were also synthesized using a novel flow system based on near ambient conditions. Oxides such as Zinc Oxide show antibacterial behavior and are therefore of interest for use with HA to develop bi-functional materials. Traditional approaches rely on using HA based powders or granules in the defect site. Bony sites are prone to infections and often require major antibiotics for a long period of time. If the antibacterial nature is ensured at the defect site, in addition to bone being regenerated quickly and in a quality manner, persistent infections can be mitigated. This can reduce the risk of revision surgeries, implant removals and in worst cases amputations and deaths. Our proposed solution relies on a biocompatible chitosan paste as a binder and carrier for flow synthesized HA and ZnO particles. The potential solution has been developed in such a way that it maintains its putty form and can also be used as an injectable option providing maximum choices to the surgeon for defectxi site filing. HA is a known material bioactive material which facilitates bone formation and Zinc oxide is a known antibacterial agent. Our efforts have identified the mechanisms and processes required to develop this potential bifunctional material. The developed HA and/or ZnO containing chitosan-based composites were characterized using Fourier Transform InfraRed Spectroscopy (FTIR), X-ray Diffraction (XRD) and Electron Microscopy (SEM).