Physalis polysaccharide-sericin nanocarriers for controlled alpha-lipoic acid delivery and improved human sperm cryopreservation

The development of delivery systems that deliver ALA as a cryoprotectant to sperm in a controlled manner could provide a promising strategy to minimize the toxicity associated with direct use of alpha-lipoic acid (ALA) during cryopreservation. Therefore, the aim of this study was to design and evaluate a nanocarrier based on sericin (SER) and a polysaccharide extracted from Physalis alkekengi for ALA encapsulation in a way that minimizes the toxicity resulting from direct use of ALA by controlling the release. To find the optimal ratio of SER and polysaccharide (pro/poly), a polysaccharide-SER-based nanocarrier (Ph-SER-NC) was synthesized using different ratios of pro/poly. Then, based on the optimization results, Ph-SER-NC was synthesized by the nanoprecipitation method, and ALA was loaded into the nanocarriers by direct system of dissolution into the aqueous phase (ALA-Ph-SER-NC). Its physicochemical characteristics were determined by the dynamic light scattering (DLS) technique. Furthermore, Fourier transform infrared spectroscopy (FTIR) was used to characterize the chemical composition, molecular properties, and surface adsorption of functional groups of the ALA-Ph-SER-NC. Then, the effects of ALA-Ph-SER-NC on biological properties after cryopreservation were investigated. The results showed that the optimal ratio of pro/poly for Ph-SER-NC synthesis was 1:2, and the resulting Ph-SER-NC had a Z-average and PDI of 109 nm and 0.21, respectively. After ALA loading, the physicochemical properties of the ALA-Ph-SER-NC, including Z-average, PDI, and zeta potential of 186.9 nm, 0.456, and − 11.8 mV, were determined, respectively. The encapsulation efficiency for ALA was determined to be 93.7%. Biological evaluation showed that at concentrations of 0.02 and 0.05 mmol/mL, the ALA-Ph-SER-NC group significantly improved sperm parameters, including increases of approximately 26% in total motility, 24% in morphology, and 12% in viability, along with a 28% reduction in DNA fragmentation index (DFI). The results indicated that ALA-Ph-SER-NC, through controlled release of ALA, preserved key biological properties of sperm. Thus, the synthesized ALA-Ph-SER-NC offers a novel and effective approach to preserve sperm quality during cryopreservation in men at risk of reduced fertility.