The Evaluation of the particle size changes of oil-in-water microemulsions containing quercetin

Microemulsion is thermodinamically stable dispersed system. Its quality is characterized by particle size (10–200 nm) and polydispersity index (PDI≤0.5). Microemulsions can enhance solubility of poor water soluble drugs as quercetin. Quercetin is a natural flavonoid, known for its antioxidant, anti-inflammatory, antiviral, antifungal properties. The aim of this study was to evaluate the changes of the particle size of three different o/w microemulsions containing quercetin within 4 weeks. Three oil-in-water microemulsions (QME-EtOH, QME-Pg, QME-PEG-400) consisted of 3% of isopropyl myristate, 33% of purified water and 64% of mixture of labrasol and co-surfactant (5:1). Ethanol (EtOH), propylene glycol (Pg) and PEG-400 were used as co-surfactants. Quercetin was dissolved in microemulsion components. Average particle size and PDI were measured applying light scattering method. Measurements were carried out after formulation, after 2 and 4 weeks. After formulation, particle size of MEs was varying according co-surfactant type: ME containing EtOH was in the range of 1.5–5.6 nm, ME containing Pg – 28.2–141.8 nm and ME formulated with PEG-400 as co-surfactant was in the range of 78.8–615.1 nm. Particle size changes were observed in all ME after 2 and 4 weeks. It was determined, that after four weeks there were no 1.5–2.0 nm size particles in ME containing EtOH, but formation of 24.4–91.3 nm size new particles was observed. In the range of 2.3–2.7 nm were 1.8–9.7% less particles and in the range of 3.1–4.2 nm were 0.9–4.4% more particles than after formulation. Increase of particle size was observed in ME containing Pg: after four weeks 0.1–5.8% increase of particle number in the range of 50.8–164.2 nm was observed. It was obtained, that there were no particles in the range of 78.8–105.7 nm in ME containing PEG-400 after four weeks. In the range of 122.4–164.2 nm were 1.8–6.8% less .[...].