[Preparation, characterization, and in vitro anti-liver tumor activity of bufalin nanoparticles with Scrophularia ningpoensis polysaccharide and ursodeoxycholic acid as carriers].

Bufalin(BF)has a significant anti-tumor effect, but its clinical application is severely restricted by its high toxicity and poor water solubility. In this study, Scrophularia ningpoensis polysaccharide(SNP)and ursodeoxycholic acid(UDCA) were synthesized into an SNP-UDCA conjugate. BF was encapsulated to prepare BF/SNP-UDCA nanoparticles(NPs). The amphiphilic compound SNP-UDCA was synthesized via the one-step method, and its structure was characterized by Fourier-transform infrared spectroscopy(FT-IR)and proton nuclear magnetic resonance(~1H-NMR). The preparation process of BF/SNP-UDCA NPs was optimized through single-factor investigations. The encapsulation efficiency and drug-loading capacity of BF/SNP-UDCA NPs were determined by high-performance liquid chromatography(HPLC). The molecular form of BF/SNP-UDCA NPs was characterized by using a transmission electron microscope, X-ray diffraction(XRD), and differential scanning calorimeter(DSC). Additionally, the stability of BF/SNP-UDCA NPs was evaluated. The release behavior of BF/SNP-UDCA NPs at different pH values was determined by dialysis. The in vitro anti-tumor effect of BF/SNP-UDCA NPs was evaluated by MTT cytotoxicity assay, flow cytometry for apoptosis, and cellular uptake. The in vitro liver targeting was evaluated by measuring cellular uptake by laser confocal microscopy. The results demonstrated that the SNP-UDCA conjugate was successfully synthesized through an esterification reaction between SNP and UDCA. The preparation process of BF/SNP-UDCA NPs was as follows: the feed ratio of SNP-UDCA to BF was 2∶1, the ultrasonic time was 30 minutes, and the stirring time was two hours. The prepared BF/SNP-UDCA NPs were spherical in shape, with a particle size of(252.74±6.05)nm, an encapsulation efficiency of 65.00%±2.51%, and a drug-loading capacity of 6.80%±0.44%. The XRD and DSC results indicated that BF was encapsulated within the NPs and existed in a molecular or amorphous state. The short-term stability of BF/SNP-UDCA NPs and stability in DMEM medium are good, and their in vitro release behavior followed the first-order equation and was pH-dependent according to the in vitro experiment. Compared with BF, BF/SNP-UDCA NPs at the same concentration showed significantly stronger cytotoxicity and apoptotic effects on HepG2 cells(P<0.05, P<0.01). The uptake of coumarin 6(C6)/SNP-UDCA NPs in HepG2 cells was time-dependent and higher than that in HeLa cells at the same concentration of C6/SNP-UDCA NPs. Moreover, after treatment with SNP, the uptake of C6/SNP-UDCA NPs in HepG2 cells decreased. In conclusion, the preparation process of BF/SNP-UDCA NPs was simple and feasible. BF/SNP-UDCA NPs could enhance the targeting ability and inhibitory effect of BF on liver cancer cells. This study will provide a foundation for liver-targeting nanoformulations of BF.