Optimization and evaluation of propolis liposomes as a promising therapeutic approach for COVID-19

The present work aimed to develop an optimized liposomal formulation for enhancing the anti-viral activity of propolis against COVID-19. Docking studies were performed for certain components of Egyptian Propolis using Avigan, Hydroxychloroquine and Remdesivir as standard antivirals against both COVID-19 3CL-protease and S1 spike protein. Response surface methodology and modified injection method were implemented to maximize the entrapment efficiency and release of the liposomal formulation. The optimized formulation parameters were as follow: LMC of 60 mM, CH% of 20% and DL of 5 mg/ml. At those values the E.E% and released % were 70.112% and 81.801%, respectively with nanosized particles (117 ± 11 nm). Docking studies revealed that Rutin and Caffeic acid phenethyl ester showed the highest affinity to both targets. Results showed a significant inhibitory effect of the optimized liposomal formula of Propolis against COVID-3CL protease (IC50 = 1.183 ± 0.06) compared with the Egyptian propolis extract (IC50 = 2.452 ± 0.11), P < 0.001. Interestingly, the inhibition of viral replication of COVID-19 determined by RT_PCR has been significantly enhanced via encapsulation of propolis extract within the liposomal formulation (P < 0.0001) and was comparable to the viral inhibitory effect of the potent antiviral (remdesivir). These findings identified the potential of propolis liposomes as a promising treatment approach against COVID-19.

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Conclusion
The present study has revealed the anti-viral potential of flavonoidal components of Egyptian propolis. Molecular docking has shown that all propolis components have high binding affinity to COVID 3-CL protease and spike protein compared to Avigan, hydroxychloroquine (HQ) and Remdesivir. An optimized liposomal formulation could guarantee both the enhanced delivery to the target cells and the improved cellular uptake of encapsulated propolis. To the best of our knowledge, that has been the first study that estimates the effect of a nanocarrier dosage form on the enhancement of the anti-viral effect of Egyptian propolis extract against Covid-19. Further clinical studies are being carried out to estimate the effeciency of the optimized formulation against COVID-19.

Keywords and materials: Propolis, Liposomes, COVID-19, 3CL-protease, Spike protein, RT-PCR, Lipoid S75 (70% phosphatidylcholine-containing fat free soybean phospholipids), Alcoholic extract of Propolis (PE), Cholesterol, Ethanol

excipients formulation