Effect of Citric Acid Surface Modification on Solubility of Hydroxyapatite Nanoparticles

Abstract

Worldwide, there is an amplified interest in nanotechnology-based approaches to develop efficient nitrogen, phosphorus, and potassium fertilizers to address major challenges pertaining to food security. However, there are significant challenges associated with fertilizer manufacture and supply as well as cost in both economic and environmental terms. The main issues relating to nitrogen fertilizer surround the use of fossil fuels in its production and the emission of greenhouse gases resulting from its use in agriculture; phosphorus being a mineral source makes it nonrenewable and casts a shadow on its sustainable use in agriculture. This study focuses on development of an efficient P nutrient system that could overcome the inherent problems arising from current P fertilizers. Attempts are made to synthesize citric acid surface-modified hydroxyapatite nanoparticles using wet chemical precipitation. The resulting nanohybrids were characterized using powder X-ray diffraction to extract the crystallographic data, while functional group analysis was done by Fourier transform infrared spectroscopy. Morphology and particle size were studied using scanning electron microscopy along with elemental analysis using energy-dispersive X-ray diffraction spectroscopy. Its effectiveness as a source of P was investigated using water release studies and bioavailability studies using Zea mays as the model crop. Both tests demonstrated the increased availability of P from nanohybrids in the presence of an organic acid compared with pure hydroxyapatite nanoparticles and rock phosphate.

Exploring phosphorus fertilizers and fertilization strategies for improved human and environmental health

“…However, adding chemically produced chelating agents or organic acids to soils increases the solubility of P under laboratory conditions, but the impact on P availability and crop productivity is low or absent under pot or field conditions (Smit et al 2013 and references herein). Nevertheless, the use of citric acid to coat the surface of the synthetic version of the naturally occurring P source, nano hydroxyapatite, enhanced P availability, and improved root development, shoot growth, and cob yield in maize (Samavini et al 2018). Notably, the process of synthesizing nano hydroxyapatite involves increasing the solution pH, which could affect P solubility.…”

“…Nanotechnology has been applied to modulate P solubility, relative to highly water-soluble P forms [e.g., monoammonium phosphate, diammonium phosphate, and triple superphosphate (to reduce solubility)] and highly insoluble phosphate rock (to increase solubility). Accordingly, the synthesis of "nano-P" (nanoscale hydroxyapatite) has been reported (e.g., Liu and Lal 2014;Samavini et al 2018). Nano-hydroxyapatite is produced in a stepwise reaction of calcium hydroxide or calcium chloride and phosphoric acid (H 3 PO 4 ).…”

“…Where enhancement of P uptake is required, nano-hydroxyapatite can be further improved by in situ addition of organic acids. Samavini et al (2018) added citric acid during the synthesis stage of nano-hydroxyapatite, modifying the surface of the nano-hydroxyapatite and generating more discrete and stabilized particles, compared with pure nano-hydroxyapatite. P release from pure nanohydroxyapatite was 50% greater than from phosphate rock.…”

Tailoring the morphological features of sol–gel synthesized mesoporous hydroxyapatite using fatty acids as an organic modifier

“…Upon further increasing the temperature, the morphology of HAP nanoparticles changes from rod-shaped to spherical. 38 Some of the organic modiers such as citric acid, ethylenediamine tetraacetic acid, and trisodium citrates, Tween 20, and polyethylene glycol MW 600, cetyltrimethylammonium bromide (CTAB) were shown to control the size, shape, morphology and pores of the HAP particles during their synthesis. [39][40][41] Though many water-soluble organic compounds and aqueous extract of many plants have been used as a green chelating agent to modify the surface of the hydroxyapatite nanoparticles, such nanoparticles are also produced in various fascinating shapes and evaluated for various applications.…”

Size effect of nano-hydroxyapatite on proliferation of odontoblast-like MDPC-23 cells

“…The results agree with the finding of Shi et al about the effect of nano-HAP on MG-63 cells 38) . Referring to other studies, we assume that nano-HAPs provide a higher surface per HAP volum for cell growth than c-HAP, which may result in increased cellular adherence and proliferation 39,40) . Additionally, smaller HAP nanoparticles could enter into cells more easily and stimulate cell growth 41) .…”