Hydroxyapatite nanoparticles formed under a wet mechanochemical method

Abstract

Hydroxyapatite (HA) nanoparticles were synthesized using a wet mechanochemical method without a calcination process. Dicalcium phosphate dihydrate (CaHPO ·2H O) and calcium carbonate (CaCO ) were mixed and milled in a planary mill using ethanol or water as liquid media in the two different synthesized routes. Effects of rotation speed and milling time on the final products formed have been studied. Experimental results showed that HA phase having a characteristic of low crystallinity could be formed under the synthesis route using water. The original phases of both starting chemicals were remained without HA formation in the synthesis route using ethanol. Particle size and morphology of HA nanoparticles were obviously depended on optimum conditions of rotation speed and milling time. Differences on phase formation in both synthesized routes have been considered and discussed based on occurring chemical reaction possibilities. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 679-688, 2017.

Synthesis and characterization of biomimetic bioceramic nanoparticles with optimized physicochemical properties for bone tissue engineering

“…Further analysis of functional groups using FTIR studies confirmed the absence of impurities and contaminations in synthesized nanoparticles which displayed absorption bands similar to the biological apatite ( Figs. 7 Accordingly, in this study, the water percentage along with the total milling time was increased. This is critical, in particular for nHA because of its smaller crystal size which renders it more sensitive to the incorporation of impurities such as nitrate, calcite, H 2 O, and CO 3 into PO sites.…”

“…For example, nHA with high crystallinity has been reported to exhibit a lower degradation rate, a higher shear strength, a more stable bone integration, and to accelerate bone healing in critical size defects. It has been reported that a prolonged milling time increases XRD peaks intensities and overall broadening corresponding to the reduction in crystallite size and increase in crystallinity ratio 7,18 (Figs. 35,37 For this purpose, milling time was one of the selected processing variables in this study to modify the crystallinity ratio.…”

“…43 Furthermore, these elemental impurities can fill the defect sites in calcium-deficient nHA. 7 During the synthesis of HA, the required level of hydroxyl groups should be available for effective generation of single-phase HA, which is usually supplied through a dry mechano-chemical reaction between precursor powders. 1 and 2).…”

“…48 The impact of calcining temperature on structural groups has also been observed where a lower temperature (≤500 C) has resulted in a broader phosphate band (at 1000 cm −1 ) and absence of hydroxyl band (at 3670 and 631 cm −1 ) in nHA. 7,48 In addition, high temperature rather than increasing the chance of decomposition, can result in coalescence of bioceramic nanoparticles with a remarkable decrease in SSA, increase in grain size, and decrease in porosity that would have adverse biological consequences. 49 Further increase in temperature leads to dehydroxylation as a result of the separation of structural OH − group with corresponding changes in absorption bands at 630 and 3572 cm −1 .…”

“…As such, improvement of synthesis methods and biomaterials properties is the interest of many studies. 7 However, the complexity of synthesis procedure, high cost, poor reproducibility, difficult control of processing variables, low-yield end product, and high byproducts are common technical challenges during synthesis methods. 3,4 To that end, different synthesis methods have been introduced using a wide range of precursor raw materials (e.g., CaHPO 4 , Ca 2 P 2 O 7 , CaCO 3 , CaO, Ca(OH) 2 , etc.).…”