Effect of pectin on the crystallization of strontium substituted HA for bone reconstruction application

The biomacropolymers of bone extracellular matrix (ECM) guide the growth of hydroxyapatite (HA) with various ionic substitutions. Pectin, a plant polysaccharide with chemical similarities to ECM, was investigated for its potential to promote the crystallization of strontium-substituted HA (SH). The influence of pectin (0.5 and 1.0 wt%) on the in situ mineralization of SH (10 and 30 mol% calcium substitution with strontium) was studied. The preferential affinity of pectin to strontium over calcium favoured the incorporation of strontium in apatite, decreased crystal size (18.85-26.22 nm) and retained more pectin residues (8-16%). The residual pectin strongly interacted with small SH particles, resulting in high microhardness (0.43-0.85 GPa) and high surface charge (-32.1 to -30.3 mV), while weak interaction with large HA particles resulted in low microhardness (0.15-0.25 GPa) and low surface charge (-35.4 to -34.6 mV). The in vitro cellular study using human osteoblast-like MG-63 cells demonstrated that inorganic size and material crystallinity play a vital role in regulating osteogenesis. The study suggests that the synchronization of low pectin concentration (0.5 wt%) and high strontium substitution in HA (30 mol%) offers the desired microhardness and in vitro osteogenic properties to emulate natural bone.