Tao Li,Zhikun Gao,Ningwei Wang,Zhiping Zhou,Wanzhen Xu,Jianfeng Zheng,Wenming Yang
In this study, molecularly imprinted polymers with Mn-doped ZnS quantum dots (ZnS:Mn QDs) were prepared using dibutyl phthalate (DBP) as the template molecule, 3-aminopropyltriethoxysilane (APTES) as the functional monomer and the tetraethoxysilane (TEOS) as the cross-linker. ZnS:Mn QDs offer a readout signal to monitor the amount of DBP bound to the imprinted matrix and to evaluate the efficiency of imprinting. The products MIPs-ZnS:Mn QDs were characterized by transmission electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction and fluorescence spectroscopy. In addition, optical stability and the effect of pH on fluorescence intensity were evaluated. The obtained polymers can sensitively and selectively recognize template molecules in real samples via fluorescence intensity. The fluorescence intensity decreases linearly with increasing concentration in the range of 5.0–50 μmol L−1. It reaches a detection limit of 0.27 μmol L−1. The average recovery rate of DBP at three spiking levels is more than 98.1%.
Two chiral covalent organic polymers (R)-COP and (S)-COP, respectively, were synthesized by Schiff base reaction using tri(4-formyl phenoxy)cyanurate (TFPC) and (1R,2R)-( +)-1,2-Diphenyl-1,2-ethanediamine or (1S,2S)-( +)-1,2-Diphenyl-1,2-ethanediamine as the building blocks. Electrochemical sensors (R)-COP/GCE and (S)-COP/GCE were prepared by coating the two chiral COPs on the surface of glassy carbon electrode (GCE) to detect tryptophan enantiomers. The results showed that both (R)-COP/GCE and (S)-COP/GCE could effectively recognize L-tryptophan (L-Trp) and D-tryptophan (D-Trp). The experimental results indicate that heterochiral interaction had an advantage over homogeneous ones between D-(or L-)Trp and R-(or S-)COP/GCE. Moreover, it was found that there is higher recognition efficiency for tryptophan on (R)-COP/GCE than on (S)-COP/GCE. The obtained (R)-COP/GCE and (S)-COP/GCE electrodes were also used for the determination of tryptophan enantiomer excess (ee), and a good linear relationships were found between the peak current and ee% of tryptophan for both (R)-COP/GCE and (S)-COP/GCE electrodes. Through the optimization of experimental conditions, it is found that there is a good linear relationship between the D-tryptophan concentration on (R)-COP/GCE electrode and the oxidation current in the concentration range of 1 ~ 50 µM and 50 ~ 300 µM D-tryptophan. The detection limit of D-tryptophan was 0.1 µM on (R)-COP/GCE.
Jiayu Huang,Jian Meng,Shaohua Chen,Siyi Zhang,Tao Liu,Chao Li,Feng Wang
Herein, we have proposed a soft metal-phenolic capsule (sMPC)-based electrochemical immunoassay for ultrasensitive detection of Epstein-Barr virus capsid antigen IgA (EBVCA-IgA), a biomarker of nasopharyngeal carcinoma. Metal probes with large size contain a number of metal ions , which are very beneficial to signal amplification for anodic stripping voltammetry ; however, these probes easily precipitate due to their heavy weight, leading to low recognition efficiency and compromised performance. In this study, we demonstrate sMPCs fabricated by metal-coordination interactions exhibit unique surface behavior compared with their solid counterparts, which significantly enhance recognition efficiency and thus improve sensitivity despite of their micrometer size. Taking advantage of the sMPCs, the involved electrochemical immunoassay shows a much-improved sensitivity with an ultralow detection limit of 0.46 fM for EBVCA-IgA and can also be used in real sample analysis. So far as we know, this is the first report on a sMPC-based electrochemical strategy. Furthermore, it clarifies the potential effect of the rigidness of probes on the performance of an involved biosensor, which is meaningful to guide the design of other functional probes. The advantages of this method, including easy to fabrication, ultrasensitivity and good selectivity , ensure a promising potential in the point-of-care diagnostics of critical diseases.
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