Rapid synthesis of eggshell derived hydroxyapatite with nanoscale characteristics for biomedical applications

Abstract Utilizing eggshells to synthesize a value added product like nanocrystalline hydroxyapatite (HA) has received a lot of attention from researchers since they are composed of CaCO3 with biologically essential trace elements such as Mg, Si, etc. Different biomedical applications need HA with appropriate nanoscale characteristics like crystallinity, particle size, morphology, surface area, mesoporous nature, etc. The same can be achieved by tuning the reaction parameters, choosing a suitable mode of preparation and utilizing organic modifiers. Here, we report the rapid synthesis of eggshell derived HA in the presence different organic modifiers using a custom built microwave reactor employing the previously optimized parameters. The synthesis process is relatively rapid and gets completed in 5 min. The absence of an organic modifier yielded inhomogeneous size nanorods in the range of 40 – 600 nm. Ethylenediaminetetraacetic acid (EDTA) assisted synthesis resulted in a flower like 1.67 ± 0.12 μm sized HA. Whereas polyethylene glycol 6000 (PEG) and cetyltrimethylammonium bromide (CTAB) assisted synthesis produced aggregated nanorods of length 31 ± 8 and 68 ± 20 nm, respectively. While the synthesis with trisodium citrate dihydrate (TSC) resulted in needles of HA with typical length of 32 ± 8 nm. Presence of Na, Mg and Si trace elements are confirmed from the composition analysis. All the samples are found to be mesoporous in nature. The in vitro cell culture experiment carried out using fibroblast NIH 3T3 cell line clearly revealed equal or higher cell viability for the samples synthesized in presence of organic modifiers as compared to sample produced without organic modifier. Thus, from the present study we find that the synthesis of eggshell derived HA using different organic modifiers via a custom built microwave reactor can be a potential approach for the rapid preparation of precursor materials with suitable nanoscale characteristics for developing bone fillers, drug/protein delivery carriers, tissue engineering scaffolds, etc.