Preparation, characterization, bioactivity, and safety evaluation of PEI-modified PLGA nanoparticles loaded with polysaccharide from Cordyceps militaris

Yong Chong Cao polysaccharides (CSPs) are extracted from Cordyceps militaris which has a wide range of pharmacological effects, especially in immune regulation. However, CSPs face certain drawbacks, including rapid metabolism and poor bioavailability, which hinder their use. The objective of this research was to enhance the preparation parameters of polyetherimide (PEI)-modified poly lactic-co-glycolic acid (PLGA), PLGA-PEI, which encapsulated CSP nanospheres using response surface methodology; investigate their properties; and evaluate their impact on RAW26.4 cells. The CSP-PLGA-PEI nanospheres were synthesized using the double emulsion solvent evaporation technique, and the best preparation conditions were determined to be a 0.5% concentration of poloxamer 188 (F68) (W/V), an organic phase (O) to water phase (W1) ratio (V/V) of 7:1, an external water (W2) to primary emulsion (PE) ratio (V/V) of 8:1, and a PLGA to PEI ratio (W/W) of 20:1, achieving a maximum encapsulation efficiency (EE) of 64.98%. The CSP-PLGA-PEI nanoparticles exhibited a nearly spherical form with a smooth exterior, were uniform in size, and demonstrated clear sustained release properties and consistent stability. Macrophages are important immune cells in innate immunity, and have remarkable polarization. CSP-PLGA-PEI nanospheres showed a good promoting effect on the activation of macrophages in our present study. In addition, CSP-PLGA-PEI nanospheres were much more effectively swallowed by RAW264.7 so that its promoting effect on immune regulation was higher than that of CSP. CSP-PLGA-PEI nanoparticles were able to effectively activate ROS signaling in zebrafish in vivo experiments and induce an immune response in their organism. Finally, CSP-PLGA-PEI nanospheres showed the potential to become a new type of immune enhancer or immune enhancement adjuvant.