Synthesis and Characterization of Gum Rosin Microspheres Containing Zinc Phthalocyanine Prepared by the Electrospraying Method

Gum rosin (GR) is a natural and renewable polymer resin obtained from pine trees with potential in medication delivery applications. This work uses electrospraying to obtain and characterize GR microspheres (eGR) containing zinc phthalocyanine (ZnPc), a synthetic blue-green macrocyclic chemical with photosensitive properties. Electrospraying effectively created uniform microspheres with high encapsulation efficiency. A ZnPc release profile was performed and it was observed that it was quickly evolved during the first 24 hours, reaching 0.438 mg per 100 mg of sample and peaking at 0.868 mg per 100 mg after 72 hours, with a further release rate slowdown, likely due to particle aggregation, gradually declining over several days. Nuclear magnetic resonance (NMR) analysis demonstrated the interaction between ZnPc and GR, confirming the successful microspheres formation. Zeta potential analysis indicated that both, eGR and eGR-ZnPc microspheres had negatively charged surfaces, likely due to anion adsorption or the presence of functional groups. The initial zeta potential values were -80.6 ± 3.3 mV for eGR and -74.1 ± 5.6 mV for eGR-ZnPc reflecting the high stability of microspheres. However, stability decreased after 120 hours due to particle aggregation, with a 70% drop in zeta potential after 360 hours. No significant differences were observed between formulations during stability tests.