Switchable cholesterol recognition system with Diels–Alder reaction using molecular imprinting technique on self‐assembled monolayer

Self-Assembled Plasmonic Nanojunctions Mediated by Host-Guest Interaction for Ultrasensitive Dual-Mode Detection of Cholesterol

Herein, a fluorescence and surface-enhanced Raman spectroscopy dual-mode system was designed for cholesterol detection based on self-assembled plasmonic nanojunctions mediated by the competition of rhodamine 6G (R6G) and cholesterol with β-cyclodextrin modified on gold nanoparticles (HS-β-CD@Au). The fluorescence of R6G was quenched by HS-β-CD@Au due to the fluorescence resonance energy transfer effect. When cholesterol was introduced as the competitive guest, R6G in the cavities of HS-β-CD@Au was displaced to recover its fluorescence. Moreover, two of HS-β-CD@Au can be linked by one cholesterol to form a more stable 2:1 complex, and then, plasmonic nanojunctions were generated, which resulted in the increasing SERS signal of R6G. In addition, fluorescence and SERS intensity of R6G increased linearly with the increase in the cholesterol concentrations with the limits of detection of 95 and 74 nM, respectively. Furthermore, the dual-mode strategy can realize the reliable and sensitive detection of cholesterol in the serum with good accuracy, and two sets of data can mutually validate each other, which demonstrated great application prospects in the surveillance of diseases related with cholesterol.

Development of surface imprinted heterogeneous nitrogen-doped magnetic carbon nanotubes as promising materials for protein separation and purification

To promote the development of molecular imprinting technique in the separation and analysis of protein, novel bovine serum albumin (BSA) surface imprinted nitrogen-doped magnetic carbon nanotubes (N-MCNTs@MIPs) are developed by this paper. The imprinted materials are prepared by depositing polydopamine (PDA) on the surface of nitrogen-doped magnetic carbon nanotubes (N-MCNTs). N-MCNTs prepared by high temperature pyrolysis and chemical vapor deposition exhibit high specific surface area, positive hydrophilicity, abundant nitrogen functional groups and excellent magnetic properties. These characteristics are conducive to the increase of effective binding sites, the smooth development of the protein imprinting process in the aqueous phase, the improvement of the binding capacity and the simplification of the separation process. The amount of BSA adsorbing on the N-MCNTs@MIPs can reach 150.86 mg/g within 90 min. The imprinting factor (IF) is 1.43. The results of competitive adsorption and separation of fetal bovine serum showed that N-MCNTs@MIPs can specifically recognize BSA. The excellent reusability and separation ability for real sample prove that N-MCNTs@MIPs have the potential to be applied to the separation and purification of proteins in complex biological samples.

A molecularly imprinted polymer undergoing a color change depending on the concentration of bisphenol A

A molecularly imprinted system is introduced here whose color gradually changes as the analyte becomes rebound. The MIP was prepared from an acryloyl-modified β-cyclodextrin (β-CD), acrylamide (AAm), and N,N'-methylenebisacrylamide (MBAA), and imprinted with bisphenol A (BPA). The sensing capability of the MIP was first tested by potentiometry. A spin-coated gold plate coated with the MIP was used as a working electrode; the electrode can differentiate BPA from phenol or p-cresol, which were used as analogs of BPA. Next, a color-responsive system was fabricated by forming a hydrogel membrane containing the modified β-CD, AAm, and MBAA. A vesicle solution was prepared from N-(2-aminoethyl)pentacosa-10,12-diynamide by sonication and incorporated into the hydrogel. The blue polydiacetylene was formed by UV photopolymerization. In the presence of BPA, this system undergoes a color change from blue to red that is proportional to the degree of BPA rebinding. The color change is due to the contraction of the gel membrane that rebinding causes. The method works to 0.5 mM BPA concentration range. The detection limits for BPA are 0.1 mM on visual assessment and 50 μM on spectrophotometric readout. Graphical AbstractA molecular imprinting system is described whose color changes from blue to red as it binds bisphenol A. The degree of rebinding can be measured by detecting the color change of polydiacetylene vesicle. CD: cyclodextrin, BPA: bisphenol A.