A novel fluorescence platform for specific detection of tetracycline antibiotics based on [MQDA-Eu3+] system.

Tetracycline antibiotics (TCs) are extensively used in clinical medicine, animal husbandry, and aquaculture because of their cost-effectiveness and high antibacterial efficacy. However, the presence of TCs residues in the environment poses risks to humans. In this study, an inner filter effect (IFE) fluorescent probe, 2,2'-(ethane-1,2-diylbis((2-((2-methylquinolin-8-yl)amino)-2-oxoethyl)azanediyl))diacetic acid (MQDA), was developed for the rapid detection of Eu3+ within 30 s. And its complex [MQDA-Eu3+] was successfully used for the detection of TCs. Upon coordination of a carboxyl of MQDA with Eu3+ to form a [MQDA-Eu3+] complex, the carboxyl served as an antenna ligand for the effective detection of Eu3+ to intensify the emission intensity of MQDA via "antenna effect", the process was the energy absorbed by TCs via UV excitation was effectively transferred to Eu3+. Fluorescence quenching of the [MQDA-Eu3+] complex was caused by the IFE in multicolor fluorescence systems. The limits of detection of [MQDA-Eu3+] for oxytetracycline, chlorotetracycline hydrochloride, and tetracycline were 0.80, 0.93, and 1.7 µM in DMSO/HEPES (7:3, v/v, pH = 7.0), respectively. [MQDA-Eu3+] demonstrated sensitive detection of TCs in environmental and food samples with satisfactory recoveries and exhibited excellent imaging capabilities for TCs in living cells and zebrafish with low cytotoxicity. The proposed approach demonstrated considerable potential for the quantitative detection of TCs.

A naked-eye visible aluminium (III)-based complex fluorescence sensor for sensitive detection of mesotrione.

Mesotrione, which is a kind of herbicide to control broad-leaved weeds, has been increasingly used due to its excellent selectivity, rapid process and low toxicity. However, the excessive application of mesotrione have led to widespread contamination. Herein, a turn-on competitive coordination-based fluorescent probe, 2-hydroxy-1-(9-purin)-methylidenehydrazinenaphthalene (HPM), has been successfully synthesized. HPM could effectively detect Al3+ in CH3OH/HEPES (1/9, v/v) with low limit of detection (LOD) being 0.2 µM via coordination. HPM also exhibited excellent imaging capabilities for Al3+ in living cells with low cytotoxicity. On the basis of the competitive coordination of HPM with Al3+, the [HPM-Al3+] complex could also serve as a potential fluorescence sensor for detecting mesotrione with the LOD of 0.2 µM. Furthermore, [HPM-Al3+] complex was applied for the detection of mesotrione in real samples and test paper. Finally, the mechanism of [HPM-Al3+] for sensing mesotrione was investigated deeply as well. This work designed a new convenient method for on-site detection of mesotrione without the large-scale equipment or complicated pre-treatment.

Sensitive fluorescence assay for the detection of glyphosate with NACCu2+ complex.

Glyphosate is widely used as an herbicide in weed control. However, the excessive use and residue of glyphosate adversely affect the environment. Thus, a rapid and highly sensitive system must be developed for glyphosate detection. Herein, a novel turn-on fluorescent probe was designed and synthesized for glyphosate, that is N-butyl-1,8-naphthalimide-4-hydrazino-6-isopropyl-chromone (NAC). The fluorescence of NAC was quenched by the addition of Cu2+ to form NACCu2+ complex in dimethyl sulfoxide/2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (DMSO/HEPES, 9/1, v/v, pH = 7.0). Upon the addition of glyphosate, the fluorescence of NACCu2+ was recovered through chelation between Cu2+ and glyphosate. The NACCu2+ complex exhibited the desired linearity of glyphosate concentration under optimum conditions in the range of 0-40 µM with a low detection limit of 36 nM. Based on competitive coordination, NACCu2+ exhibited good sensitivity and selectivity for glyphosate. Moreover, NAC was successfully utilized to detect glyphosate in tap water, local water from Songhua River, soil, maize, and soybean with convenient operations, indicating a promising application in pesticide residue detection.