Preparation and Sustained-Release Properties of Panax notoginseng Leaf Saponins-Loaded Multi-Walled Carbon Nanotubes/Chitosan Composite Gel

Abstract

: To address the intrinsic drawbacks of pure drug-loaded chitosan hydrogels—namely poor mechanical strength, severe initial burst release, and insufficient structural stability—this work developed a multi-walled carbon nanotube (MWCNT)/chitosan composite hydrogel loaded with Panax notoginseng leaf saponins (LPNS). Systematic characterization of its microstructure, stability, and sustained-release performance was conducted to provide experimental support for developing local delivery carriers for active ingredients of traditional Chinese medicine. The composite hydrogel was fabricated via ultrasonic dispersion coupled with physical crosslinking. MWCNT loading was optimized using visual appearance, swelling ratio, and mechanical properties as evaluation criteria, while LPNS loading was optimized based on encapsulation efficiency and drug loading capacity. Intermolecular interactions among components were analyzed via Fourier transform infrared spectroscopy (FT-IR). Swelling kinetics, thermal stability, and in vitro drug release profiles were investigated, and the release mechanism was elucidated through kinetic modeling. At optimal loadings of 0.045 g MWCNTs and 0.07 g LPNS, the resultant composite hydrogel was homogeneously dispersed, yielding a 37.2% improvement in tensile strength relative to pure chitosan hydrogel, alongside an encapsulation efficiency of 97.47% and drug loading capacity of 3.34%. It reached a swelling ratio of 491% after 4 h of immersion in pH 7.4 PBS, and retained structural integrity after 24 h of storage at both 4 °C and 60 °C, demonstrating markedly superior stability to the pure chitosan counterpart. The in vitro release profile featured a suppressed initial burst and prolonged sustained release, with 68.3% cumulative drug release at 48 h. The release kinetics best fitted the Higuchi model (R² = 0.9912), with a Fickian diffusion-dominated release mechanism. Collectively, the incorporation of MWCNTs effectively reinforces the mechanical strength and structural stability of chitosan hydrogels and significantly retards LPNS release. This composite hydrogel holds great promise for local sustained delivery of traditional Chinese medicine active ingredients