Comparison of crude nano-hydroxyapatite extracted from calcified seaweed in terms of composition, antibacterial activity, and cytotoxicity

Abstract

The objectives of this study were to synthesize nano-hydroxyapatite (nHAp) from red seaweed by an optimized and environmentally friendly thermal and chemical treatment method using minimal chemicals. Calcified tissues from seaweed were thermally treated to obtain calcium carbonate, which reacted with potassium dihydrogen phosphate to synthesize nHAp. Nano-hydroxyapatite materials, nHAp-Jr and nHAP-Co were produced from the seaweeds Jania rubens and Corallina officinalis, respectively. Results showed that the developed method successfully produced high yields of nHAp-Jr and nHAp-Co powders (>78 %). The crude composition of the synthesized nHAp-Jr and nHAp-Co materials was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), scan electron microscopic (SEM), Energy dispersive X-ray spectroscopy (EDAX), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), and thermal gravimetric analysis (TGA). XRD patterns confirmed the formation of nHAp and calcium phosphate phases. SEM images showed the nanoparticle size of nHAp-Jr and nHAp-Co with an average distribution of 16.70 ± 0.71 nm. EDAX spectra identified the relative similar elemental compositions of nHAp-Jr and nHAp-Co. BET and BJH patterns revealed relatively similar specific surface area, total pore volume and average pore diameter for mesoporous size nHAp powders (2–50 nm). Antibacterial activity of nHAp-Jr and nHAp-Co showed good efficacy against the caries-causing agent, Streptococcus mutans compared to ciprofloxacin using the modified XTT assay. Cytotoxicity testing of nHAp-Jr and nHAp-Co against WISH cell line using modified MTT assay confirmed the relevant antibacterial effects without any side effect on hepatocytes. This sustainable method produced nHAp compounds from seaweed that show promising antibacterial properties and biocompatibility, highlighting the potential for biomedical applications.