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[Display omitted] • A novel ratiometric probe for hydrogen peroxide is reported. • The protein-based strategy converts off-on type response into the ratiometric one. • This method enables the portable detection with a 3D-printed miniaturized testing system. • Smartphone-based on-site detection of hydrogen peroxide in real milk samples was achieved. The on-site detection of hydrogen peroxide (H 2 O 2) is important for maintaining food safety as the ingestion of H 2 O 2 can lead to serious pathological conditions. However, most reported fluorescent probes require a fluorometer to ensure readable signal output and reliable detection result. Consequently, the fluorescent detection of H 2 O 2 can be realized only within a standard laboratory setting. Herein, we report a novel supramolecular strategy that can successfully convert the typical off-on response to H 2 O 2 into a ratiometric response, which allows the on-site detection of H 2 O 2 when used in conjunction with a smartphone-based 3D-printed miniaturized testing system. This method has acceptable sensitivity, good anti-interference ability, and desirable accuracy compared to a standard detection method. More importantly, this portable ratiometric method can be used to detect H 2 O 2 residue in commercial milk samples with the simple testing apparatuses. [ABSTRACT FROM AUTHOR]

A colorimetric and fluorescent dual probe for CO is designed and synthesized. The probe is capable of sensitive and specific detection of CO with naked-eye through colorimetric assay in phosphate buffer from colorless to yellow, which also features 75-fold turn-on fluorescence enhancement upon exciting at 480 nm with the detection limit of 26.3 nM. The probe shows great potential for sensing intracellular CO without the interference in living cell imaging. On the other hand, the probe could also be utilized as an efficient and convenient visual indicator for CO gas in air by naked eyes. [ABSTRACT FROM AUTHOR]

Monitoring of cysteine (Cys) is of significant importance for studying Cys-involved biological functions and clinically diagnosing Cys-related diseases. Recently, few fluorescent probes with two different reacting sites were reported to be capable of sensing different concentration ranges of Cys with distinct fluorescence signals, particularly suiting for bioimaging. However, due to relative sophisticated synthesis and moderate selectivity, the applications of these probes were still severely restricted. In this work, we proposed a novel probe design strategy by utilizing two same reacting groups, instead of two different reacting groups, to simplify the synthesis route and minimize the interference from competing species. Same reacting groups in a probe with different steric hindrances could exhibit different reactivities to Cys. This probe showed distinguishable fluorescence peak wavelengths towards low and high concentration ranges of Cys, giving green and blue emissions, respectively. Moreover, this probe was successfully applied for monitoring of Cys concentration in living cells. We believe this work provided a simpler strategy for dual-site fluorescent probes to sense difference concentration ranges of Cys, which may inspire more probe design in future. [Display omitted] • A novel fluorescent probe with dual acrylate sites was designed and synthesized. • The probe enables discrimination of different concentration ranges of cysteine. • Same reacting groups in one probe with different steric hindrances could exhibit different reactivities to cysteine. • This probe was successfully applied for monitoring of cysteine concentration in living cells. [ABSTRACT FROM AUTHOR]

Simultaneous detection of two or more biothiols by using fluorescent methods is in particular importance for biological research and disease diagnosis. Because (1) the variation of one biothiol level under specific cellular metabolism may lead to the change of another biothiol, and (2) several diseases such as Alzheimer's disease associate with joint action from two or more biothiols. In this paper, we provide an overview of the fluorescent probes with multiple channels that have been applied to simultaneous detection of biothiols. The present review highlights the basic characteristics of probes with multi-channel in the respect of design principle, photophysical process, sensing mechanism, sensing performance, and bioapplications. This review aims to offer a comprehensive summary for researchers to inspire new probe design, and also push forward the advancement of simultaneous detection of biothiols based on multi-channel probes. • The fluorescent probes with multiple channels for simultaneous detection of biothiols are reviewed. • The necessity of simultaneous detection of biothiols is introduced. • The design mechanism of fluorescent probes with multiple channels has been discussed and categorized. • The overall sensing performances and bioapplications of probes are summarized. [ABSTRACT FROM AUTHOR]

Closantel is widely used in the management of parasitic infestation in livestock, but is contraindicated in humans due to its high toxic to human retina. Thus, development of a fast and selective method for the detection of closantel residues in animal products is highly needed yet still challenging. In the present study, we report a supramolecular fluorescent sensor for closantel detection through a two-step screening process. The fluorescent sensor can detect closantel with a fast response (<10 s), high sensitivity, and high selectivity. The limit of detection is 0.29 ppm, which is much lower than the maximum residue level set by government. Moreover, the applicability of this sensor has been demonstrated in commercial drugs tablets, injection fluids, and real edible animal products (muscle, kidney, and liver). This work provides the first fluorescence analytical tool for accurate and selective determination of closantel, and may inspire more sensor design for food analysis. [Display omitted] • The first fluorescent detection method for closantel is reported. • This sensor can detect closantel with a fast response, high sensitivity, and high selectivity. • The limit of detection to closantel is 0.29 ppm. • This method enables on-site determination of closantel in real food samples. [ABSTRACT FROM AUTHOR]

Buprofezin (BUP) is an insect growth regulator widely used in agriculture to control hemipteran pests, particularly the melon aphid, Aphis gossypii , due to its efficiency and low toxicity. Although approved by the Chinese government, its maximum residue limit (MRL) in food is strictly regulated, and conventional techniques for detecting BUP have several limitations. Our study reports successful BUP detection using a supramolecular fluorescent probe DP@ALB, constructed with chalcone-based fluorescent dye DP and albumin as the host. The probe offers advantages such as low cost, visual signal output with high fluorescence color variation, rapid response, and high sensitivity. Additionally, portable test strips enable convenient on-site BUP detection and simplifying field monitoring of spiked real samples. The study achieves precise qualitative and quantitative BUP analysis in grape fruit, groundwater, and soil with satisfactory recoveries. Further, the biological applicability of sensor for the in vitro detection of BUP in L929 living cells was demonstrated. This research breakthrough overcomes the limitations of traditional analytical methods, offering an efficient and reliable approach for food and environmental monitoring and pesticide residue detection. • Supramolecular sensor showed ratiometric detection of buprofezin (0.003–1.000 mM). • DP dye higher emission resulted in brighter visual detection of buprofezin. • Detection limit for BUP was 2.67 μM, with an average recovery of 99.7%. • The portable testing devices were integrated for on-site detection of BUP. • Sensor successfully monitored BUP in real-world samples and L929 cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • This work reported the first ratiometric fluorescent probe for nitroxinil. • The probe enables fast, sensitive and selective detection of nitroxinil. • On-site analysis in real food samples was available by using paper strips. • Fluorescence imaging of nitroxinil in Hela cells was successfully achieved. Nitroxinil (NIT) is a widely using veterinary medicine to protect cattle and sheep yet may threaten human health when ingested through food chain. Developing fluorescent analytical methods in ratiometric manners was essential for the on-site detection and in-situ monitoring of NIT but still challenging. Here, we improved the indicator-displacement assay (IDA)-based method and designed the first ratiometric fluorescent probe for NIT by using an albumin host and an Aggregation-induced emission (AIE) guest. This probe exhibited fast response (10 s), high sensitivity (limit of detection: 4.6 ppb), good selectivity (over twelve medicines) and eye-discriminable fluorescent color change (green–red) upon responding to NIT. Based on these properties, this probe enabled quantitative determination of NIT in real food samples, on-site analysis via a paper-based test strip, and fluorescence imaging of NIT in living cells. [ABSTRACT FROM AUTHOR]