Assembly of Anionic Conjugated Polymer with 6-O-Modified PNP-β-Galactoside for Fluorescence Logic-signal-based Multiplex Detections of Enzymes

Cinchona alkaloid copolymers as fluorimetric INHIBIT and colorimetric AND logic gates for detection of iodide

Four cinchona alkaloid-acrylamide water soluble copolymers with a mean hydrodynamic diameter of 3 nm were synthesised by free radical polymerization. The copolymers were characterised by 1H NMR, FTIR, GPC, DLS, UV-vis and fluorescence spectroscopy. A blue emission is observed with H+ switching of 185 and 175-fold for the quinidine and quinine copolymers, and 21 and 11-fold for the cinchonine and cinchonidine copolymers, while the presence of Cl-, Br- or I- causes fluorescence quenching. In emission mode, the copolymers function as fluorescent H+, X--driven INHIBIT logic gates (where X = Cl-, Br- or I-). In absorbance mode, the copolymers function as colorimetric H+, I--driven AND logic gates in 1 : 1 (v/v) THF/water with a 76-fold enhancement. The solution colour changes from colourless to yellow with formation of new absorbance bands at 288 nm and 353 nm due to a π-anion non-covalent charge transfer interaction. The copolymers may be useful as selective iodide sensors for medical and analytical diagnostics.

Graphene Quantum Dots and Enzyme-Coupled Biosensor for Highly Sensitive Determination of Hydrogen Peroxide and Glucose

In this paper, a simple and specific graphene quantum dots (GQDs)-based fluorescent biosensor adopted for the determination of glucose based on the combination of the enzyme-coupled method and fluorescence quenching mechanism is demonstrated. Glucose was oxidized by the enzyme glucose oxidase (GOx), forming hydrogen peroxide (H 2 O 2 ) via the catalysis by horseradish peroxidase (HRP). H 2 O 2 was then employed to oxidize phenol to quinone, which led to effective quenching effect in the GQDs⁻GOx⁻HRP⁻phenol system. By optimizing the reaction conditions of the GQDs-enzyme system, a linear relationship between the concentration of glucose and the fluorescence intensity over a range of 0.2⁻10 μ mol/L was obtained. The limit of detection for glucose is 0.08 μ mol/L. The present biosensor for the determination of glucose showed satisfactory reproducibility and accuracy in human serum samples. Since the enzymes have high specificity and unique affinity to the certain substance, the enzyme-coupled system promises a sensitive way for further detection of those chemicals which could be oxidized by enzymes and generated H 2 O 2 or glucose. GQDs and other fluorescent materials coupled with several enzymes can be applied to extensive sensing field.

A multiaddressable photochromic bisthienylethene with sequence-dependent responses: construction of an INHIBIT logic gate and a keypad lock

A photochromic bisthienylethene derivative (BIT) containing two imidazole units has been synthesized and fully characterized. When triggered by chemical ions (Ag(+)), protons, and light, BIT can behave as an absorbance switch, leading to a multiaddressable system. BIT exhibits sequence-dependent responses via efficient interaction of the specific imidazole unit with protons and Ag(+). Furthermore, an INHIBIT logic gate and a keypad lock with three inputs are constructed with the unimolecular platform by employing an absorption mode at different wavelengths as outputs on the basis of an appropriate combination of chemical and photonic stimuli.

Novel fluorescent biosensor for α-glucosidase inhibitor screening based on cationic conjugated polymers

A new fluorescent biosensor has been designed to screen α-glucosidase inhibitors (AGIs) sensitively by utilizing signal amplification effect of conjugated polymers. The fluorescence of cationic poly(fluorenylene phenylene) (PFP) was quenched in the presence of para-nitrophenyl-α-d-glucopyranoside and α-glucosidase, and turned on upon addition of AGIs. Thus, a new method was developed for AGIs screening based on the fluorescence turn-off/turn-on. The IC(50) values obtained for inhibitors were compared with that reported using absorption spectroscopy. All results present the new method is more sensitive and promising in screening AGIs and inhibitors of other enzymes whose hydrolysis product is 4-nitrophenol.