Detecting Pesticide Dodine by Displacement of Fluorescent Acridine from Cucurbit[10]uril Macrocycle

According to a simple guest-replacement fluorescence turn-on mechanism, we constructed a fluorescent probe system based on cucurbit[10]uril (Q[10]) and protonated acridine (AD) to detect the pesticide dodine (DD). Formation of a homoternary inclusion complex AD₂@Q[10] in both aqueous solution and solid state was studied by means of ¹H NMR spectroscopy and X-ray crystallography. Although AD can emit strong fluorescence in aqueous solution, the homoternary inclusion complex AD₂@Q[10] does not exhibit any fluorescence. Upon the addition of the pesticide DD into the aqueous solution of AD₂@Q[10], the AD molecules in the Q[10] cavity are displaced by the pesticide DD, and strong fluorescence recovers. The fluorescent probe system based on Q[10] and AD provided a wide determination of DD from 0 to 4.0 × 10^-5 mol·L^-1 with a low limit of detection of 1.827 × 10^-6 mol·L^-1. The guest-replacement fluorescence turn-on mechanism is also confirmed by ¹H NMR spectroscopy. Further, the fluorescent probe can directly detect DD residues in real agricultural products, and obvious fluorescence signal was observed under UV irradiation.

A fluorescent probe based on cucurbit[7]uril for the selective recognition of phenylalanine

Herein we describe a simple fluorescence quenching method for the selective recognition and determination of the amino acid phenylalanine (Phe). The use of ¹H NMR spectroscopy revealed that the alkaloid palmatine (PAL) can encapsulated partially into the cavity of cucurbit[7]uril (Q[7]) in aqueous solution to form a stable 1:1 host-guest inclusion complex. This host-guest complex exhibits fluorescence of moderate intensity. Interestingly, the addition of the Phe results in a dramatic quenching of the fluorescence intensity associated with the inclusion complex. By contrast, the addition of other natural amino acids resulted in no change in the fluorescence. Based on the linear relationship between the fluorescence intensity and the concentration of Phe, the detection of the concentration of Phe in aqueous solution is facile. Thus, a new fluorescence quenching method for the recognition and determination of the Phe has established herein.

Selective recognition and determination of phenylalanine by a fluorescent probe based on cucurbit[8]uril and palmatine

This paper demonstrated a simple and validated fluorescence enhancing method to selectively recognize and discriminate the amino acid phenylalanine (Phe). ¹H NMR spectroscopy reveal that the palmatine (PAL) can be encapsulated into the cucurbit [8]uril (Q [8]) in aqueous solution to form stable 1:2 host-guest inclusion complex PAL₂@Q [8], which exhibits moderate intensity fluorescence property. Interestingly, the addition of the Phe into the inclusion complex PAL₂@Q [8] leads to dramatically enhancing of the fluorescence intensity. In contrast, the addition of any other natural amino acids into the inclusion complex PAL₂@Q [8] gives no fluorescence variation. Furthermore, it is easy to detect the concentration of Phe in target aqueous solution according to the linear relationship between fluorescence intensity and concentration of the Phe.

Reversible Shape-Morphing and Fluorescence-Switching in Supramolecular Nanomaterials Consisting of Amphiphilic Cyanostilbene and Cucurbit[7]uril

We demonstrate a reversible shape-morphing with concurrent fluorescence switching in the nanomaterials which are complexed with cucurbit[7]uril (CB[7]) in water. The cyanostilbene derivative alone forms ribbon-like two-dimensional (2D) nanocrystals with bright yellow excimeric emission in water (λ_em =540 nm, Φ_F =42 %). Upon CB[7] addition, however, the ribbon-like 2D nanocrystals immediately transform to spherical nanoparticles with significant fluorescence quenching and blue-shifting (λ_em =490 nm, Φ_F =1 %) through the supramolecular complexation of the cyanostilbene and CB[7]. Based on this reversible fluorescence switching and shape morphing, we could demonstrate a novel strategy of turn-on fluorescence sensing of spermine and also monitoring of lysine decarboxylase activity.

A New Fluorometric Method for the Determination of Oxaliplatin Based on Cucurbit[7]uril Supramolecular Interaction

This paper proposed new competitive methods for fluorescence detection of the anti-cancer drug oxaliplatin. The methods were based on the competitive reaction of palmatine (PAL)/berberine (BER)/coptisine (COP) with oxaliplatin for the occupancy of cucurbit[7]uril (CB[7]) cavities. The results showed that the fluorescence intensity of PAL, BER, and COP regularly increased upon addition of CB[7] until a certain amount of oxaliplatin was added, at which stage the fluorescence intensity of the system quenched. Using the CB[7]–PAL, CB[7]–BER, and CB[7]–COP systems, linear ranges in the detection of oxaliplatin of 0.005–1.75, 0.010–1.50, and 0.020–1.05 μg mL–1, with detection limits of 2, 3, and 7 ng mL–1, respectively, were obtained. These results suggest that cucurbit[7]uril is a promising drug carrier for delivering and monitoring targeted oxaliplatin, with improved anti-tumour efficacy and reduced toxicity in normal tissues.