## 3 Results and Discussion
At day 0, the pore volume was recorded at approximately 0.128 cm\({}^{3}\)/g, increasing to 0.613 cm\({}^{3}\)/g following the drug release study. This suggests that the release of the drug from the pores contributed to pore expansion, allowing more gas to adsorb on the surface during the second BET analysis. HA on the surface, leading to the formation of numerous smaller pores. The reprecipitation of material on the glass surface could explain the simultaneous increase in surface area and decrease in average pore size. Figure 5 shows the SEM images of the as-synthesized BG-V before and after the drug release studies. The first image (a) shows a smooth and dense surface at day 0, while the second image (b) shows the crystallization of the apatite layer on the surface of the BG. Figure 5b shows an increase in porosity which can be attributed to the degradation of BG as well as the release of the preloaded vancomycin. Figure 6 shows the SEM-EDS, which also confirms that the development of HA on the surface of BG-V as a spectrum of atom weight percentage of Si, Ca, and P went from 49.3%, 45%, and 10%, respectively, to 28.5%, 26.5%, and 17.5% after the drug release test was conducted in around 33 days. The ratio of Ca/P was observed to be 1.51 after immersion in PBS, the same ratio reported in other studies indicating the crystallization of apatite on the surface of the BG. The formation of a Ca/P ratio around 1.5 is particularly significant as it closely resembles the stoichiometric ratio found in natural bone minerals, suggesting that the bioactive glass has effectively facilitated the biomimetic mineralization process [34; 35]. Furthermore, the SEM-EDS analysis revealed the presence of a newly formed crystalline layer on the surface of the BG-V after immersion in PBS, which indicates the bioactive glass's capability to promote the deposition of HA. This is consistent with the XRD findings as it shows the crystalline layer that developed on the surface of BG-V after immersion in PBS and provides evidence for the ability of this material to deliver drugs and repair bone defects. These findings align with previous studies, where increased Ca, P, and O concentrations on the bioactive glass surface were shown to indicate HA formation. In a study conducted by [PERSON] et al., the Ca/P ratios reported were 1.78, 1.60, and 1.2, confirming HA deposition, with differences attributed to variations in the initial Ca and P content of the glass compositions [36]. Further supporting this, [PERSON] et al. observed HA development on the surface of bioactive glass evidenced by the increase in phosphate and calcium concentrations and a decrease in silicon concentration after immersion in SBF for seven days [37]. The drug release studies were conducted in PBS at physiological pH 7.4 to simulate in vivo conditions. Figure 7a shows the drug release observed on day 1, demonstrating a rapid initial release where approximately 20% of the vancomycin was released within the first few hours. This is followed by a plateau phase, indicating that the initial burst  
Figure 5: SEM images of BG-V before (**a**) the drug release study and after (**b**) the drug release study. Image (**b**) shows a more porous structure after drug release. corresponds to the release of drug molecules adsorbed on the surface, which occurs within 4 to 5 h.  
Figure 6: Atomic weight percentage of silicon, calcium, and phosphorous before and after drug release studies. Figure 7: Drug release (%) of vancomycin from BG-V for the duration of the experiment (**a**) and the release on the first day (**b**) drug release over 30 days. Figure 7b illustrates the cumulative vancomycin release over 30 days. While the initial phase mirrors the burst release as seen in Figure 5a, the long-term profile reveals a more gradual and sustained release pattern. The near-linear progression of drug release beyond the first day suggests a controlled diffusion mechanism or gradual degradation of the bioactive glass matrix, facilitating continuous drug delivery.