Various types of fluorescent nanoparticles have been proposed for the detection of veterinary drug residues in food. However, structure-induced fluorescence nanoparticles with biodegradability and the capacity to conjugate with molecular recognition elements are lacking. Here, a biodegradable tryptophan-phenylalanine dipeptide-based nanomaterial was assembled and modified with a sulfadimethoxine aptamer ( [email protected] ). Then, a novel and efficient fluorescence sensing strategy, based on [email protected] and BHQ1-labeled single-stranded DNA ( [email protected] ), was developed for sulfadimethoxine determination. Under optimal conditions, the fluorescence was linear in the range of 0–200 ng/mL sulfadimethoxine with a detection limit of 1.47 ng/mL (S/N = 3). Satisfactory recoveries of standard additions were found between 92.88 % and 114.15 % for water and milk samples with a relative standard deviation less than 5.0 %, suggesting that the proposed fluorescence sensing strategy can be applied reliably in sulfadimethoxine analysis of liquid foods.
A novel multifunctional nano-drug delivery system based on reversal of peptide charge was successfully developed for anticancer drug delivery and imaging. Mesoporous silica nano-particles (MSN) ~50 nm in diameter were chosen as the drug reservoirs, and their surfaces were modified with HIV-1 transactivator peptide-fluorescein isothiocyanate (TAT-FITC) and YSA-BHQ1. The short TAT peptide labeled with FITC was used to facilitate intranuclear delivery, while the YSA peptide tagged with the BHQ1 quencher group was used to specifically bind to the tumor EphA2 membrane receptor. Citraconic anhydride (Cit) was used to invert the charge of the TAT peptide in neutral or weak alkaline conditions so that the positively charged YSA peptide could combine with the TAT peptide through electrostatic attraction. The FITC fluorescence was quenched by the spatial approach of BHQ1 after the two peptides bound to each other. However, the Cit-amino bond was unstable in the acidic atmosphere, so the positive charge of the TAT peptide was restored and the positively charged YSA moiety was repelled. The FITC fluorescence was recovered after the YSA-BHQ1 moiety was removed, and the TAT peptide led the nano-particles into the nucleolus. This nano-drug delivery system was stable at physiological pH, rapidly released the drug in acidic buffer, and was easily taken up by MCF-7 cells. Compared with free doxorubicin hydrochloride at an equal concentration, this modified MSN loaded with doxorubicin molecules had an equivalent inhibitory effect on MCF-7 cells. This nano-drug delivery system is thus a promising method for simultaneous cancer diagnosis and therapy.
Pengfei Ma,Hua Ye,Hualin Guo,Xiaoyuan Ma,Lin Yue,Zhouping Wang
Herein, for the first time, a novel truncation strategy for aptamers’ sequences based on molecular docking was reported for the first time. T-2 toxin and AFB 1 aptamers were employed as models and fluorescence polarization was used to measure the affinity of aptamers. The T-2 toxin aptamer (T40) with 40 bases and the AFB 1 aptamer with 32 bases were successfully obtained with increased affinities compared with original aptamers. Meanwhile, circular dichroism, FAM-BHQ1 dual labeled T40, enzyme digestion, and molecular dynamics simulation were performed to investigate the binding mechanism between aptamer T40 and T-2 toxin. Finally, based on MnO 2 nanosheet and the fluorescence amplification effect of SYBR Green I, simplified and rapid fluorescence detection of T-2 toxin was achieved with a detection range of 0.03 nM to 30 nM, indicating the great potential of aptamer in practical detection applications.
危险品化学品经营许可证（带存储）