The aim of the present study is to evaluate the synergistic antimicrobial effect of the propolis encapsulated into alginate nanoparticles (ALg NPs) against different pathogenic bacteria. The morphological analysis using TEM revealed that, the propolis-ALg NPs are spherical, discrete and have a small particle size (13 nm) in the nanometer scale. FTIR studies showed a spectral change of the characteristic absorption's bands of ALg NPs after encapsulationbeing encapsulated with propolis. A high negative zeta potential value is obtained for propolis-ALg NPs, which indicates to thea high suspension stability of the prepared formulation. The dielectric study showed a decrease in the dielectric constant (ε'), dielectric loss (ε″) and conductivity (σ) values after the incorporation of the propolis into Alg NPs. Thus, these observations referred toconfirm the successful encapsulation of propolis within ALg NPs.
On the other hand, the propolis-ALg NPs showed the highest antimicrobial activity against all examined pathogens in comparison with propolis alone or antibiotic (Clindamycin). Therefore, these results indicated that the propolis exhibited a synergistic antibacterial activity against different bacterial strains when used in combination with ALg NPs.