Formulation and characterization of pH-responsive pickering emulsions stabilized by soy protein isolate/nicotinamide mononucleotide complexes for controlled drug release

pH-responsive emulsion stabilizer can be used as an ideal Pickering emulsion type drug embedding and sustained release. However, achieving an optimal balance of particle wettability and size, emulsion stability, and drug encapsulation efficiency remains challenging. This study delves into the potential of soy protein isolate (SPI) and nicotinamide mononucleotide (NMN) complexes as pH-responsive stabilizers for Pickering emulsions, aiming to optimize particle properties, emulsion stability, and drug encapsulation efficiency for biomedical applications. Our findings illustrate that 1.5 wt% NMN concentration yields the optimal SPI/NMN composite particle properties, contributing to enhanced emulsion stability. The stability was further improved at pH 7 with the addition of 0.01 mol/L sodium chloride. SPI/NMN complexes under these conditions formed a unique three-dimensional network within the continuous phase, evidenced by 3D-laser confocal microscopy. Furthermore, at this NMN concentration, the emulsion thermal stability index peaked at 73.2% above the initial value, accompanied by optimal water-holding capacity (82.5%) and surface coverage (89.23%). Exploring drug encapsulation, we observed that 2% ibuprofen dosage in the microspheres results in drug loading and encapsulation efficiencies of 33.5% and 89.6%, respectively. Importantly, the SPI/NMN-embedded ibuprofen exhibited pH-responsive behavior, with increased release in alkaline conditions and reduced release in acidic ones, signifying potential for pH-targeted drug delivery. The SPI/NMN-embedded ibuprofen showed pH-responsive behavior, with enhanced release at alkaline pH values and reduced release under acidic conditions, suggesting potential utility in pH-targeted drug delivery applications.