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While slow release of chemicals has been widely applied for drug delivery, little work has been done on using
this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers
can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that
minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a
commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the
crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of
urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite
nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In
addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method
reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer
having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by in situ
coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area
to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash
drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for
its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is
demonstrated
