Background: Hydroxyapatite (HAp) is one of the most studied biomimetic method for biomedical applications. Especially, nano-HAp has been utilized for bone tissue engineering and various other orthopedic applications. HAp possesses different suitable properties such as bioactivity, biodegradability, and cell proliferation efficiency for bone tissue engineering applications. Yet, it lacks in self-antibacterial activity, high surface area, and target efficiency.
Results: In this direction, researchers have focused on exploring the required surface as well as the inherent properties of HAp at the nanoscale. These properties are largely dependent on the composition, size, and morphology of the nano-HAp. Hence, nano-HAp has been found to be an excellent candidate with an attractive combination of properties for selection and use in biomedical applications, those required to enhanced biological responses. Further, depending on the type of application, these factors can be tuned to optimize the performance.
Conclusion: In this review article, we focus on the chemical structure of HAp and the routes chosen and used for the synthesis of the nano-HAp. The role of various parameters in controlling synthesis at the nanoscale is presented and briefly discussed. In addition, we provide an overview of the various applications for the pristine and doped nano-HAp with recent examples in areas spanning the following: (i) bone tissue engineering applications, (ii) drug delivery applications, (iii) surface coatings, and (iv) scaffolds. The effect of chemical composition on the mechanical properties, surface properties, and biological properties are also highlighted. Nano-HAp is found to be highly proficient in its biomedical applications, especially bone tissue engineering applications. The nanosized properties enhance the biological responses. The dopant ions that replace the Ca ion into the hydroxyapatite (HAp) lattice play a crucial role in its biomedical applications.