## 3 Results
### Doping of HA Nanoparticles
#### 3.3.1 Strontium-Doped Nano-Hydroxyapatite (Sr-Nano-HA)  
Strontium (Sr), a trace element with chemical properties similar to calcium (Ca), constitutes approximately 98% of its presence in osseous tissue [12]. Sr follows physiological pathways akin to calcium, with a pronounced tendency to accumulate in bones and teeth, where it supports mineral metabolism and structural integrity [11]. At low concentrations, Sr promotes bone formation by enhancing osteoblast activity, reducing bone resorption, and inhibiting osteoblast apoptosis. However, excessive Sr concentrations can disrupt bone remodeling by interfering with metabolic processes and inhibiting osteoclast apoptosis, which may adversely affect bone health [44].  
The incorporation of Sr\({}^{2+}\) ions into nano-hydroxyapatite (nano-HA) has been shown to significantly improve its biological properties. Sr\({}^{2+}\) doping enhances bioactivity, osteoinductivity, and protein adsorption, while also reducing cytotoxicity and increasing drug-loading potential [45]. [PERSON] et al. demonstrate that Sr-doped HA coatings on titanium substrates significantly improve cell adherence [46]. This improved cell attachment is crucial for applications in orthopedic and dental implants.  
Angiogenesis, a critical process linked to osteogenesis, is positively influenced by Sr\({}^{2+}\) doping, making Sr-nano-HA a promising material for hard tissue regeneration [44]. Sr-doped nano-HA has also been shown to enhance the regenerative capacity of biomaterials, resulting in the formation of abundant and mature bone tissue at defect  
\begin{table}
\begin{tabular}{c c c} \hline
**Ion** & **Effects of Doping Hydroxyapatite** & **References** \\ \hline \multirow{4}{*}{Strontium} & Reduced cytotoxicity, enhanced bio-protein & [PERSON] et al. (2023) [45], \\  & absorption, increased & [PERSON] et al. (2023) [47], \\  & osteoconductive capabilities & [PERSON] et al. (2021) [48] \\ \hline \multirow{2}{*}{Zinc} & Enhanced bioactivity, stimulation of osteogenic & [PERSON] et al. (2023) [44], [PERSON] et al. \\  & activity, antibacterial properties, promotion of & (2024) [49] \\  & fibroblast proliferation & \\ \hline \multirow{2}{*}{Magnesium} & Increased mineralization, enhanced & [PERSON] et al. (2023) [44] \\  & osseointegration capability, osteogenesis and & [PERSON] et al. (2014) [51] \\  & bone regeneration promotion & \\ \hline Silver & Antibacterial properties & [PERSON] et al. (2023) [53] \\ \hline \multirow{2}{*}{Selenium} & Enhanced osteoinductive properties, & [PERSON] et al. (2021) [56] \\  & oncolytic activity & \\ \hline \multirow{2}{*}{Boron} & Stimulation of osteoblasts, improved osteogenic & [PERSON] et al. (2018) [57], \\  & differentiation of mesenchymal stem cells & [PERSON] et al. (2020) [58], \\  & & [PERSON] et al. (2022) [59] \\ \hline \multirow{2}{*}{Cobalt} & Oxidative stress reduction, angiogenesis & [PERSON] et al. (2024) [60], \\  & promotion, antibacterial effect & [PERSON] (2016) [61], \\  & & [PERSON] et al. (2023) [62] \\ \hline \multirow{2}{*}{Copper} & Bacterial biofilm inhibitor, angiogenesis & [PERSON] et al. (2023) [62], \\  & promotion, increased biocompatibility & [PERSON] et al. (2024) [65], \\  & & [PERSON] et al. (2019) [67] \\ \hline \multirow{2}{*}{Iron} & Acceleration of mature bone formation, & \\  & enhanced bioactivity and solubility & [PERSON] (2021) [69], [PERSON] et al. (2013) [70] \\ \hline \multirow{2}{*}{Cerium} & Antibacterial properties, promotion of osteoblast & [PERSON] et al. (2023) [71], \\  & proliferation and differentiation & [PERSON] et al. (2011) [72] \\ \hline \multirow{2}{*}{Fluorine} & Antibacterial properties, stimulation of bone & [PERSON] et al. (2018) [74], \\  & formation, tooth decay prophylaxis & [PERSON] et al. (2021) [75] \\ \hline \end{tabular}
\end{table}
Table 2: Effect of doping hydroxyapatite with chosen ions.  
sites [47, 48]. These findings highlight its potential in addressing bone defects and improving implant integration.