Encapsulation of quercetin-loaded β-lactoglobulin for drug delivery using modified anti-solvent method

Many scientists use proteins as attractive bio-availability enhancers for natural compounds and pharmaceuticals which have poor water solubility, due to their natural abundance, amphiphilic nature, and desirable biocompatibility. Here, we investigate the preparation, characterization, and application of beta-Lactoglobulin (BLG) based nanoparticles for encapsulation of quercetin, systematically. We used anti-solvent method that is common for nano particle preparation of water-soluble proteins. The procedure involves partial unfolding of protein molecules, limited aggregation in the presence of anti-solvent, crosslinking via chemical linker, and refolding of the constituent monomers. The results showed that acetone anti-solvent has significant effect on accumulation of BLG-quercetin nanoparticles. Adjustment of acetone content to the value of 10% v/v (acetone/water) followed by mild evaporation led to a notable improvement in Encapsulation Efficiency (EE%) and Loading Efficiency (LE %), which raised LE to 13.9%. In addition, reducing glutaraldehyde amount to 50% of equivalent, led to toxicity reduction of the drug carrier system. The nanoparticles with a mean particle size of about 180-300 nm and semispherical appearance were approved using Atomic Force Microscopic (AFM) and Field Emission Scanning Electron Microscopy (FESEM) methods. Protein nanoparticles may be digested at different stages of the gas-trointestinal tract, depending on acidity, ionic strength, or specificity of proteases (pepsin and trypsin). This study suggested that BLG as a resistant protein to peptic digestion forms nanoparticles that are digestible (compared to untreated BLG) by pepsin. As a result, satisfactory controlled release was achieved under simulated fast condition, i.e., digestion in simulated gastric fluid (SGF) at pH = 2 and then in simulated intestinal fluid (SIF). Finally, the mechanism of drug release into the buffer environment was well-fitted by the Korsmeyear-Peppas kinetic model. The conclusions of this study may apply not only to quercetin-BLG system, but also to a wide variety of encapsulation systems involving water-soluble protein and hydrophobic target compound, with adequate LE and reduced toxicity.