Development of chitosan-based Centella asiatica nanoparticles and their immunostimulatory activity through macrophage phagocytosis assay

Abstract Background Centella asiatica (L.) extract (ECA) has demonstrated immunostimulatory effects, with macrophages playing a key role in immune regulation. However, a significant proportion of bioactive compounds derived from natural sources exhibit poor aqueous solubility and may pose toxicity concerns, hindering their absorption and reducing their bioavailability. To address these limitations, nanotechnology-based drug delivery approaches have been explored, including the use of chitosan, a biocompatible polymer, as a carrier material. Methods Centella asiatica extract-loaded chitosan nanoparticles (NECA) were developed and evaluated in this study to investigate their physicochemical properties and immunostimulatory activity. The nanoparticles were formulated using the ionic gelation technique, followed by freeze-drying, with different concentrations of ECA and sodium tripolyphosphate as the crosslinking agents. Comprehensive characterization was conducted, including particle size analysis, morphological observation, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). Results The resulting NECA particles ranged in size from 136.4 to 451.6 nm, with encapsulation efficiencies of 79.47% to 89.27%. XRD analysis indicated a transformation of the material from crystalline to predominantly amorphous, which may enhance solubility. The immunostimulatory activity was assessed in Balb/c mice using the carbon clearance assay. Administration of NECA at doses of 100 and 200 mg/kg significantly increased macrophage phagocytic activity and resulted in higher lymph and liver indices compared with the control group ( p < 0.05). Conclusion These results demonstrate that NECA can enhance macrophage-mediated immune responses and may serve as a promising nanoparticle-based immunostimulant delivery system.