## 3 Results and Discussion
### Antimicrobial Studies  
Following the confirmation of the presence of the drug molecules in the loaded MOFs using the above techniques, the antimicrobial properties of the loaded MOFs and their corresponding polymer-MOF composites were tested against Gram-positive and Gram-negative bacteria, using the inhibition zone assay (Figure 9) against the four selected bacterial strains. The zones of inhibition of pristine MOFs and polymers only are presented in Table 1, those of pure Met, Met-loaded MOFs and polymer composites are in Table 2 and those of pure Ceph, Ceph-loaded MOFs and polymer composites are in Table 3. \begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \multicolumn{4}{c}{**Inhibition Zone (mm)**} \\ \hline  & _S. epidermidis_ & _S. aureus_ & _E. coli_ & _A. baumanii_ \\ \hline Pristine MOF-5 & \(26\pm 1.5\) & \(28\pm 0\) & \(13\pm 1.1\) & \(13\pm 0.5\) \\ PLGA & \(51\pm 1.5\) & - & - & - \\ PCL & - & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Zones of inhibition of pristine MOF, PLGA and PCL against four bacterial strains. Figure 9: Images of the zones of inhibition on agar plates after microbial testing of the loaded composites against the strains of bacteria. The relevant areas are circulated where multiple tests were performed. The susceptibility of the bacterial strains to the pure drugs was first assessed. Ceph is widely used against Gram-positive bacteria, more than against Gram-negative bacteria, and this agrees with the zones of inhibition recorded in Table 3 below. The growth of _S. epidermidis_ and _S. aureus_ was largely inhibited by Ceph more than in the case of Gram-negative bacteria, _E. coli_ and _A. baumannii_[62; 63]. It was observed that _A. baumannii_ was not susceptible to Ceph, which is consistent with literature and previous studies that report the extreme resistance of this bacterial strain to cephalospor. Compared to the antimicrobial strength of Met, which is a first-class antibiotic, well-known for a relatively stronger antimicrobial reaction against both Gram-negative and Gram-positive bacteria [65], Met inhibited all bacterial strains, as shown below (Table 2). The pristine PLGA and PCL were also tested as controls, and there was no inhibition across all bacterial strains, apart from the PLGA that presented a large zone of inhibition against _S. epidermidis_ (Table 1). This is however expected and can be attributed to the antimicrobial properties of the glycolic and lactic acid composition of PLGA and the very high susceptibility of the Gram-positive _S. epidermidis_[66; 67; 68]. From Table 2, met@MOF-5 inhibited the growth of Gram-positive bacteria, _S. aureus_ and _S. epidermidis_, more than the Gram-negative bacteria, _E. coli_ and _A. baumannii_, and this is attributed to the strong resistance of Gram-negative bacteria to Met [69]. In the case of PLGA-met@MOF-5, it was observed that the zones of inhibition significantly decreased, with no inhibition against the resistant Gram-negative bacteria; however, the susceptible _S. epidermidis_ was largely inhibited [70], and this can be assigned to the slow release of drug molecules due to the degradability of the composite and the MOF before the release of the drug molecules. Compared with PCL-met@MOF-5, there was no inhibition against all strains of bacteria. This agrees with the data from the drug release studies displayed in Figure 8 above, which depicts the slower release of drugs from PCL composites in relatively lower concentrations. This is because PCL has a slower degradation rate and takes much longer to release the loaded MOFs carrying the drug molecules [52]. Ceph@MOF-5 reacted better against the Gram-positive bacteria than the resistant Gram-negative bacteria strains owing to the presence of the Ceph drug molecules, which is consistent with the findings of