Biomimetic Hydroxyapatite Crystallization in Gelatin Nanoparticles Synthesized Using a Miniemulsion Process

Graphical Abstract

A biomimetic approach for the synthesis of hybrid hydroxyapatite (HAP)/gelatin nanoparticles using gelatin nanoparticles synthesized via the inverse miniemulsion process as template is reported. The formation of HAP in the nanoconfinement follows Ostwald's rule of stages, where initially formed amorphous calcium phosphate transforms into single crystalline HAP. Such a hybrid material represents a very promising candidate for application in tissue engineering.

Abstract

Here, we report a novel biomimetic strategy to synthesize hydroxyapatite (HAP) inside of crosslinked gelatin nanoparticles, which serve as a nanoenvironment for crystal growth in the aqueous phase. The synthesis of gelatin nanoparticles with the inverse miniemulsion technique is very intriguing because of the flexibility offered by the technique in tailoring the properties of the gelatin nanoparticles. It can be shown that the nanoenvironment promotes a different growth environment for the crystal because of the confinement inside the particle. The formation of HAP inside the particles follows Ostwald's rule of stages. At first an amorphous phase is formed, which itself has a great potential to be used as a resorbable bone substitute. This further transforms into single crystalline HAP via an octacalcium phosphate intermediate. The solution-mediated transformation into the HAP phase without any calcination step is studied in detail using transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements.