Coralline Halimeda opuntia algae-derived bio-hydroxyapatite enhances the bioactivity of piezoelectric tissue engineering scaffolds

Abstract

Biomaterials are increasingly being used to promote tissue repair after wounds. Coralline algae have been reported as valuable sources of hydroxyapatite (HAp). The identification and characterization of Halimeda opuntia with high calcium carbonate content from the Indian Ocean have been performed. Bio-hydroxyapatite (Bio-HAp) was synthesized through a combined process of pyrolysis followed by a hydrothermal treatment. The effect of pyrolysis temperature on the critical properties of the HAp such as Ca/P ratio, morphology and presence of trace elements was assessed. It was found that a calcination temperature of 900 °C produced Bio-HAp with a Ca/P of 1.57 ± 0.01, which is non-stoichiometric and calcium-deficient, similar to the HAp integrated in bone. HAp can integrate with bone without causing any local or systemic toxicity, inflammation or foreign body response, thus we have loaded the synthesized Bio-HAp into piezoelectric PHBV/PDX electrospun mat and assessed the behaviour of human dermal fibroblasts (HDF) and human pre-osteoblasts (HoB) in co-culture at different cell densities. Increasing Bio-HAp content from 1 % to 5 % increased fiber diameter due to fiber melting. Bio-HAp enhanced differentiation of HDF promoting mineralisation with Ca/P ratios of 1.93 ± 0.17 and 1.80 ± 0.18 at 1 % and 5 % HAp content respectively. The mineralisation process was more prominent on scaffolds with Bio-HAp compared to the controls (0 % HAp and synthetic-HAp) with both HDF only and HDF/HoB.