The composition, shape, size, and surface charge of the NPs can affect cellular interactions with biological systems. The TEM results indicate that the propolis-ALg NPs have a small particle size in the nanometer scale. Therefore, they can permeate through cell membranes more effectively. The zeta potential results indicate the high suspension stability of the propolis-ALg NPs due to the highly negative charges on the NPs surface which reducereduces the aggregations between the particles. Therefore, ALg NPs can enhance propolis stability and penetration power compared to the propolis solution. The FTIR studies showed a spectral change of the characteristic absorptions bands of Alg NPs after encapsulation with propolis. Furthermore, the dielectric spectroscopy studies confirmed a decrease within the dielectric loss and conductivity values and an increase in the relaxation time of the two processprocesses of propolis–ALg NPs as compared to Alg NPs. Therefore, these observations suggest the successful encapsulation of propolis within Alg NPs.
In addition to that, it iswas found that the encapsulation of propolis within ALg NPs significantly enhanced the antibacterial activity against all examined microorganisms as compared to propolis alone or the antibiotic (Clindamycin). Hence, in the present study, we have developed a negatively charged propolis-Alg NPs system as a promising antibacterial agent against a wide spectrum of microbes.