Particle Size and Distribution Modelling of Nanohydroxyapatite-in-gelatin Nanocomposite Microspheres by Surface Response Method

The effects of nanohydroxyapatite/gelatin (nHA/G) ratio, stirring rate and water/oilphase ratio (W/O ratio) on particle size and distribution of nanocompositemicrospheres based on nanohydroxyapatite-in-gelatin were investigated.Surface response model was used for tests design. The microspheres were fabricatedusing water-in-oil emulsion followed by their characterizations using optical microscopy,scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), X-raydiffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR).Statistical models with interaction terms were derived to model the particle size anddistribution of the microspheres. Addition of nHA to gelatin led to larger sizes ofmicrospheres, although the higher nHA/G ratio (0.5-1) led to their slightly smaller size.The data revealed that further increase in stirring rate resulted in microspheresize reduction. The results showed that at different stirring rates, W/O ratio has acteddifferently. By increasing in nHA/G ratio, the uniformity of the microspheres improved.The effect of stirring rate was dependent on nHA/G ratio. Various W/O ratios did notshow any significant effect on particle size distribution, and yet their higher ratiosenhanced the uniformity of particle size to some extent. Statistical analysis revealedthat the generated models are valid for modeling of the particle size and its distribution.SEM images showed that by addition of nHA to gelatin, the microspheres becomesmoother. At high ratios of nHA/G (>1) some cracks were observed on the surface ofthe microspheres. Calcium mapping of the surface and cross-section of themicrospheres confirmed the uniform distribution of nHA on the surface and within theirbulk. The XRD and FTIR studies showed that the fabrication process did not affect thechemical and physical characteristics of gelatin and nHA any longer.