## 3 Results  
Physical properties analysis was performed by determination of particle size distribution and zeta potential, as shown in Figures 5 and 6. Particle size distribution of PLA and PLGA nanoparticles indicated a mean particle size of approximately 44 nm and \(-25.2\) mv zeta potential, and mean particle size of 180 nm and \(-33.1\) mv for PLGA, respectively. After loading the antibiotic onto PLA/PLGA matrix, erythromycincin-loaded PLA nanoparticles were recorded around 325 nm in size, while drug-loaded PLGA nanoparticles were recorded approximately 258 nm in size, depending on the initial antibiotic concentration. Electro-kinetic potential measured at the exterior side of the colloidal nanostructures indicated zeta potential values of drug-loaded polymer nanoparticles of \(-11.3\) mv for PLA and \(-17.3\)mv for PLGA, respectively, which denoted the degree of rejection of similarly charged particles in dispersion. A higher zeta potential for nanoparticles indicates the stability of colloidal dispersions resisting nanoparticles aggregation. HPLC chromatograms are presented in Figure 7. It can be seen from the chromatogram of the samples that the retention times of erythromycincin are approximately the same as the retention times of erythromycincin in the reference chromatogram. The percentage content of erythromycinomycin A was calculated using the chromatogram shown in Figure 7a, as a reference, and the percentage content of erythromycincin B using the chromatogram shown in Figure 7b, as a reference. The amount of erythromycincin propionate in both samples was expressed as the sum of erythromycincin A and erythromycincin B and was 99.7% of the initial amount used to prepare antibiotic-loaded nanoparticles for both samples. We observed (Figure 8) that drug release from Ery-PLA was slowly more increased than from Ery-PLGA nanostructures. In the case of Ery-PLA, almost 55% of the antibiotic was controlled released within 4 h, and 75% was released within 2 days. In the case of erythromycincin-loaded PLGA nanoparticles, approximately 55% of drug was released within 4 h, while 75% was released within 3 days. These results evidenced that the antibiotic encapsulation into PLGA nanoparticles was a little bit slower than into PLA nanoparticles. Surface morphologies (Figure 9) exhibited spherical, rigid, and ring-shaped nanoparticles. This panel revealed regular and isolated nanoparticles attributed to lactic content, which prevent aggregates formation. The result of our investigation showed (Figure 10), in the case of Ery-PLA and Ery-PLGA samples, that the pure drug has an endothermic peak at around 150 \({}^{\circ}\)C, assigned to a melting point. The antibiotic melting peak disappeared for both antibiotic encapsulated PLA/PLGA nanoparticles thermographs, denoting the existence of erythromycincin and indicating a possible uniform distribution of the drug throughout the host polymer at the molecular stage. Figure 6: Distribution pattern of erythromycincin-loaded PLGA nanoparticles. Figure 7: HPLC chromatogram for erythromycinomycin references (**a**,**b**) and Ery-PLA/PLGA samples (**c**,**d**). Furthermore, the thermographs also revealed a reduction in both PLA and PLGA transition temperature concerning nano-encapsulation of erythromycinocin due to increase of particles size, in the case of which glass transition temperature is inversely proportional to the amorphous polymers particle size. FTIR spectra (Figure 11) of Ery-PLA and Ery-PLGA nano-architectures revealed chemical structure of drug-loaded polymer nanoparticles and peaks were almost similar. Figure 8: In vitro antibiotic release out of Ery-PLA/Ery-PLGA nanoparticles. Figure 10: Thermal analysis graph of (**A**) erythromycinocin (Ery), PLA, and erythromycinocin-loaded PLA (Ery-PLA); (**B**) erythromycinocin (Ery), PLGA, and erythromycinocin-loaded PLGA (Ery-PLGA). Figure 9: SEM images of (**A**) Ery-PLA and (**B**) Ery-PLGA.