Abstract:
Hydroxyapatite (HA) is the main inorganic component of bone and dentin, and their non-stoichiometric compositions and plate-shaped morphology is responsible for their bioactivity and osteoconductive nature. Collagenous (CPs) and non-collagenous proteins (NCPs) facilitate mineralization and regulate structural properties of
HA through their side-chains. The bioactivity of synthetic HA does not usually match with the HA found in bone
and, therefore, there is a need to understand the role of biomolecules in bone mineralization in order to develop
non-stoichiometric plate-shaped HA for bone grafts. Role of several amino acids has been investigated but the
role of L-his has been rarely investigated under physiological conditions even though it is a part of HA inhibitor
proteins, like albumin, amelogenin, and histidine-rich proteins. In this study, L-his and L-glu were used to modify
the structural properties of HA in different experimental conditions and buffer systems (tris and hepes). The
results showed that L-his was able to regulate the plate-shaped morphology of HA in every experimental condition, unlike the L-glu, where the crystal morphology was regulated by experimental conditions. Both amino
acids behaved differently in DI water, tris, and hepes buffer, and the media used influenced the precipitation time
and structural properties of HA. Hepes and tris buffers also influenced the HA precipitation process. Overall, the
studies revealed that L-his may be used as an effective regulator of plate-shaped morphology of HA, instead of
large NCPs/proteins, for designing biomaterials for bone regeneration applications and the choice of buffer
system is important in designing and evaluating the systems for mineralization. In cell culture studies, mouse
osteoblast precursor cells (MC3T3-E1) showed highest proliferation on the bone-like plate-shaped HA, among all
the HA samples investigated.
