# Nanostructured Sr-Doped Hydroxyapatite: A Material with Antimicrobial Potential

## TL;DR

This study shows that strontium-doped hydroxyapatite nanocrystals can be made in an eco-friendly way and have antimicrobial properties, especially against certain bacteria.

## Contribution

The paper introduces an environmentally benign method to synthesize Sr-doped hydroxyapatite with confirmed antimicrobial activity.

## Key findings

- XRD and FT-IR confirmed the formation of pure monocrystalline SrHAp.
- SEM and TEM revealed nanorod and prismatic structures with sizes around 25 nm × 10 nm.
- SrHAp showed antimicrobial efficacy, particularly against Gram-positive bacteria like S. aureus and L. monocytogenes.

## Abstract

This research investigated the feasibility of producing strontium-doped nanocrystalline hydroxyapatite (SrHAp) through an environmentally benign synthesis approach and evaluated the antimicrobial activity of the resulting material. The synthesized nanomaterial was subjected to comprehensive characterization. The antimicrobial efficacy of SrHAp was tested against Gram-positive and Gram-negative bacterial strains. X-ray diffraction (XRD) analysis in combination with Fourier-transform infrared (FT-IR) spectroscopy confirmed the successful formation of pure monocrystalline SrHAp. The scanning electron microscopy (SEM) examination revealed two predominant morphological structures: nanorods and prismatic configurations of the SrHAp. Transmission electron microscopy (TEM) demonstrated that the rod-like SrHAp nanocrystals aggregate into elongated grain structures with a size of about 25 nm × 10 nm. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) analysis confirmed the presence and quantification of the concentrations of calcium, strontium, and phosphorus, while confirming the expected calcium–phosphorus ratio characteristic of hydroxyapatite. The study established that the positive surface charge of the material, with a point of zero charge near pH 10, is essential for its antimicrobial efficiency. These results suggest that SrHAp nanomaterials hold promise for biomedical applications, particularly as antimicrobial coatings for implants and scaffolds for bone tissue, where the prevention of infection is critical. Overall, despite its selective and material quantity-dependent antimicrobial efficacy, environmentally friendly synthesized SrHAp can be successfully applied as an effective controller of targeted microbial contamination, especially of Gram-positive bacterial species S. aureus, L. monocytogenes, S. Enteritidis, and A. baumanii.