A cholesteric chiral artificial receptor L5 was synthesized, which recognized and cooperated with Ag + in metal ions, and a rapid method for detecting Ag + was established in food. It was found by fluorescence spectroscopy analysis that the L5 could recognize Ag + in DMSO solution; with the help of fluorescence and UV titration, job test and interference test to verify its recognition pattern, and founded that the L5 and guest Ag + were combined with 1:1 coordination ratio. Then, the recognition mechanism between L5 and guest Ag + was explored by measures of nuclear magnetic titration, infrared spectroscopy, electron microscopy and computer molecular simulation. It was speculated that the carbonyl oxygen atom near the amide of the MeO-PhCONH group and the carbonyl oxygen atom of the –COOCH 3 group cooperated with Ag + throµgh electrostatic gravitational interaction. This method was used to establish the detection of Ag + in food in which the detection limit of L5 for Ag + was derived as 0.13 µmol/L, and the silver ions in wolfberry, milk powder,wheat flour, tea leaf and soybean were accurately detected. This method can be used to quantify Ag + content in actual samples accurately and efficiently.
Objective. To investigate the potential of L5 peptide-guided pretargeting approach to identify GPC3-expressing hepatocellular carcinoma (HCC) using ultrasmall superparamagnetic iron oxide (USPIO) as the MR probe. Methods. Immunofluorescence with carboxyfluorescein- (FAM-) labeled L5 peptide was performed in HepG2 cells. Polyethylene glycol-modified USPIO (PEG-USPIO) and its conjugation with streptavidin (SA-PEG-USPIO) were synthesized, and their hydrodynamic diameters, zeta potential, T2 relaxivity, and cytotoxicity were measured. In vitro and in vivo two-step pretargeting MR imaging was performed on HepG2 cells and tumor-bearing mice after the administration of biotinylated L5 peptide (first step), followed by SA-PEG-USPIO (second step). Prussian blue staining was performed to assess iron deposition in tumors. Results. The high specificity of L5 peptide for GPC3 was demonstrated. Generation of SA-PEG-USPIO nanoparticles with good biocompatibility (an average hydrodynamic diameter of 35.97 nm and a zeta potential of −7.91 mV), superparamagnetism (R2 = 0.1039 × 103 mM−1s−1), and low toxicity was achieved. The pretargeting group showed more enhancement than the nonpretargeting group both in vitro (60% vs 20%, ) and in vivo (32% vs 6%, ). Substantial iron deposition was only observed in HepG2 cells and tumors in the pretargeting group. Conclusion. L5 peptide-guided, two-step pretargeting approach with USPIO as the MR imaging probe is a lucrative strategy to specifically identify GPC3-expressing HCC.
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