Surface molecularly imprinted polymers (SMIPs) for selective adsorption of ampicillin sodium were synthesized using surface molecular imprinting technique with silica gel as a support. The physical and morphological characteristics of the polymers were investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), elemental analysis and nitrogen adsorption-desorption test. The obtained results showed that the SMIPs displayed great adsorption capacity (13.5 μg/mg), high recognition ability (the imprinted factor is 3.2) and good binding kinetics for ampicillin sodium. Finally, as solid phase extraction adsorbents, the SMIPs coupled with HPLC method were validated and applied for the enrichment, purification and determination of ampicillin sodium in real milk and blood samples. The averages of spiked accuracy ranged from 92.1% to 107.6%. The relative standard deviations of intra- and inter-day precisions were less than 4.6%. This study provides a new and promising method for enriching, extracting and determining ampicillin sodium in complex biological samples.

Downregulation of P-glycoprotein (P-gp) is implicated in the pathophysiology of inflammatory bowel disease (IBD). Berberine, a principal isoquinoline alkaloid extracted from Berberis species, has been reported to exhibit therapeutic potential in IBD. In this study, we used a dextran sulfate sodium (DSS)-induced colitis rat model to evaluate the effect of berberine on P-gp and explore its mechanism of action. Berberine treatment improved DSS-induced colitis symptoms, attenuated inflammatory markers (myeloperoxidase, tumor necrosis factor-α, and interleukin-1β and -6), and enhanced P-gp expression in a dose-dependent manner. Although colonic expression of the P-gp-related nuclear receptor pregnane X receptor and transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) were downregulated in the colitis model, gene and protein expression analysis revealed that berberine treatment only reversed the downregulation of Nrf2. In vitro studies using Caco-2 cells showed that the multidrug resistance 1 (MDR1) gene and P-gp protein were upregulated by berberine in a dose- and time-dependent manner. Significant upregulation of the MDR1 gene by berberine was abrogated by Nrf2 silencing, indicating that the Nrf2-mediated pathway was responsible for this activation. Luciferase assays using Caco-2 cells showed a dose-dependent increase in Nrf2 reporter gene activity following berberine treatment, with a significant twofold elevation at 2.5 μM berberine, suggesting that berberine is a strong Nrf2 activator. These results suggest the possible involvement of Nrf2-mediated upregulation of P-gp in the therapeutic effect of berberine on colitis and highlight the potential of P-gp and/or Nrf2 as new therapeutic targets for IBD.