Evaluation of Cytotoxicity of Green Synthesized Strontium Fluorapatite Nanoparticles on Human Gingival Fibroblasts: An In Vitro Study

nontoxic, pollution-free, economical, and sustainable.Recently, hydroxyapatite NPs (HAp NPs) have been developed for remineralization of enamel.However, they lack strength, are brittle and have low solubility. 10Previous studies replacing calcium ions in hydroxyapatite with strontium ions have reported increased reactivity, solubility, and fluoride release. 11,12Thus, a nanosystem of strontium-doped hydroxyapatite with fluoride may work synergistically to remineralize enamel.With the recent growing interest in the development of NPs, toxicity of these materials is a concern. 13Wide range of published literature evaluating cytotoxicity of NPs using different cell lines, IntroductIonSynthesis of nanoparticles (NPs) and their application in various fields have led to the forefront of research. 1NPs have found their way into several biomedical applications such as drug delivery, diagnostic tools, and even cancer treatment. 2In dentistry, various applications include dental implants, restorative materials, prevention of caries and white spot lesions, teeth whitening, antisensitivity agents, and polishing agents. 3anoparticles (NPs) may be organic (dendrimers, liposomes, etc.), carbon-based (fullerenes, carbon quantum dots), or inorganic (metals, ceramics, or semiconductors). 4NPs have a high surface-tovolume ratio and hence offer several advantages such as accelerated adsorption rate, extended half-life period, and increased drug concentration. 5NPs are synthetically developed by either topdown or bottom-up approaches.In top-down approaches, bulk materials are divided into nanostructures and include procedures such as mechanical milling, laser ablation, and electro-explosion. 6In bottom-up methods, NPs are assembled from corresponding atoms and molecules through chemical or biological procedures such as sol-gel process, laser pyrolysis, chemical reduction, etc. 7 However, all these chemical methods lead to environmental pollution, largescale energy consumption, and adverse health issues. 8reen synthesis employs environment-friendly materials such as plant extracts and microorganisms, which behave as reducing agents to reduce metal ions to metallic NPs. 9 It is