A colorimetric-aptamer-based assay for the determination of enrofloxacin through triggering the aggregation of gold nanoparticles.

Although enrofloxacin (ENR) is a widely used broad-spectrum antibiotic in veterinary medicine, its residues in animals can pose a risk to human health. Thus, we developed a new method for detecting ENR based on aptamers and AuNPs. In the absence of ENR, the aptamers attached to the surface of the AuNPs via electrostatic interactions to protect the AuNPs from NaCl, and the solution remained red. Conversely, the aptamer bonded with ENR, leading the aptamer to detach from the AuNP surface, and the color of the solution changed from red to blue. Based on this principle, ENR can be qualitatively detected by the naked eye and quantitatively detected by measuring the absorbance ratio at 650 nm and 530 nm. The experimental results showed a good linear relationship within the ENR concentration range of 0-400 nM, with a limit of detection (LOD) of 1.72 nM, which is satisfactory for detection in food safety. Additionally, this method has also been successfully applied to the detection of ENR in tap water, river water, milk, serum and urine, with good recovery rates and RSD values of less than 7%, indicating its great potential for ENR detection in environmental water samples. More importantly, the combination of this method with a smartphone platform provided great convenience for on-site and visual detection of ENR, offering promising applicability prospects.

A fluorescence probe with targeted mitochondria for detecting hydrogen peroxide in vitro and in diabetic mice.

We designed and prepared probe W-1 for the detection of H2O2. W-1 showed excellent selectivity for H2O2 and was accompanied by colorimetric signal changes. The excellent linear relationship between fluorescence intensity and H2O2 concentration (0-100 µM) provided favorable conditions for its quantitative detection. In addition, the combination of portable test strips with a smartphone platform provided great convenience for on-site visual detection of H2O2. Moreover, W-1 possessed targeting mitochondria property and could be applied to image the exogenous and endogenous H2O2 in cells to distinguish normal cells and cancer cells. Lastly, W-1 was used for monitoring the H2O2 fluctuation of the diabetic process in mice, and the results showed an increase in H2O2 levels in diabetes. Therefore, the probe provided a tool for understanding the pathological and physiological mechanisms of diabetes by imaging H2O2.

Development of the near-infrared fluorescence probe for detection of ONOO- and its application in vitro and vivo.

Diabetes has become one of the most common endocrine and metabolic diseases threatening human health, which can induce mitochondrial dysfunction and exacerbate the excessive production of reactive oxygen species (ROS). Among them, ONOO- level fluctuation was closely related to diabetes. Hence, it is of great significance to develop a near-infrared fluorescence probe for visualizing ONOO- level fluctuations in diabetes. In this paper, we constructed a fluorescence probe YBL with dicyano-isophorone derivative as fluorophore and diphenyl phosphate as ONOO- response site, which can detect ONOO- with the low detection limit (39.8 nM) and exhibit excellent selectivity and sensitivity. The probe YBL has been applied to monitor intracellular ONOO- level fluctuations. Meanwhile, the image results showed that high sugar promoted the increase of ONOO- level in cells. More important, the probe YBL can be used for imaging in mice, and the results showed that content of ONOO- was increased in diabetic mice. Therefore, the probe YBL provided a tool for understanding diabetes progression by imaging ONOO-.

The highly selective and sensitive fluorescence probe for detection of copper (II) ions and its bioimaging in vitro and vivo.

We designed and developed the probe W-3 for detection of Cu2+. The results showed probe can selectively detect Cu2+, accompanied by noticeable color change. The probe can detect the Cu2+ in water samples and drinks based on absorption detection. In addition, the combination of portable test paper and the smartphone platform obtained great convenience for on-site and visual detection of Cu2+, with satisfactory sensitivity and reliability. More importantly, the fluorescence probe W-3 can be used for the detection of Cu2+ in cells and mice. Therefore, the W-3 provided potential chemical tools for detecting Cu2+ in vitro and vivo.

Multifunctional fluorescence probe for simultaneous detection of viscosity, polarity, and ONOO- and its bioimaging in vitro and vivo.

Intracellular microenvironment (viscosity and polarity) and peroxynitrite ions (ONOO-) are involved in maintaining cell morphology, cell function, and signaling so that it is crucial to explore their level changes in vitro and vivo. In this work, we designed and synthesized a mitochondria-targeted fluorescence probe XBL for monitoring the dynamic changes of viscosity, polarity, and ONOO- based on TICT and ICT mechanism. The fluorescence spectra showed obvious changes for polarity at 500 nm as well as ONOO- and viscosity at 660 nm, respectively. The XBL can image simultaneously viscosity, polarity, and ONOO- in cells, and the results showed excess ONOO- leaded to the increase of viscosity in mitochondrial. The ferroptosis process was accompanied by increase of intracellular viscosity and ONOO- levels (or decrease of polarity), which allowed us to better understand the relevant physiological and pathological processes. The XBL can distinguish normal cells and cancerous cells by the fluorescence intensity changes in green and red channels, and image viscosity in inflamed mice. Thus, XBL can provided the chemical tool to understand the physiological and pathological mechanisms of disease by simultaneous detection of viscosity, polarity and ONOO-.

Development of peroxynitrite-responsive fluorescence probe for recognition of drug-induced liver injury.

Peroxynitrite (ONOO-) as an active substance, is produced during normal physiological process, which plays an important role in maintaining cell REDOX balance and cell function. Moreover, the peroxynitrite is involved in many diseases and especially can be used as a biomarker of drug-induced liver injury (DILI). Therefore, in this work, we synthesized a fluorescent probe JQ-3 for detecting ONOO-. The results showed the probe JQ-3 possessed excellent selectivity, fast response time (10 min) and low detection limit (32 nM). The probe JQ-3 is almost unaffected by pH, showing the potential application in biological systems. Moreover, the probe JQ-3 can be successfully used for the detection of exogenous and endogenous ONOO- in living cells and zebrafish. At the same time, the DILI was successfully recognized by visualizing ONOO- with JQ-3 in living cells and zebrafish. Therefore, the probe JQ-3 provides a potential tool for detecting ONOO- to understand physiological and pathology processes of disease.

A highly selective probe for ratiometric imaging peroxynitrite in living cells and in vivo.

In this study, we constructed and displayed a ratiometric fluorescent probe JQ-2 for detecting ONOO-. The probe JQ-2 showed a ratiometric signal for visualizing ONOO- with a rapid response and high selectivity over a panel of biological analytes. Moreover, the JQ-2 has near-infrared emission (657 nm), which provides an excellent basis for the practical application in biological systems. The probe JQ-2 possessed low cytotoxicity and excellent cell membrane permeability, which can specifically visualize the exogenous and endogenous ONOO- in vitro and vivo by emission in two channels. Meanwhile, JQ-2 can be used for diagnosing drug-induced liver injury by visualizing and monitoring the fluctuations of endogenous ONOO-. Therefore, JQ-2 provided a potential tool for precisely detecting the fluctuation of ONOO- in biological systems to understand physiological and pathological process.

Finding a resveratrol analogue as potential anticancer agent with apoptosis and cycle arrest.

Resveratrol has been extensively studied as the anti-cancer agent. A variety of resveratrol analogues have been developed with structural modification to improve its bioactivity. In this work, resveratrol analogues, compound 1-4, were designed and synthesized with the Stille-Heck reaction. These results showed compound 1-4 had better anticancer effect than that of parent resveratrol. Especially compound 1 ((E)-4,4'-(ethene-1,2-diyl)bis(3-methylphenol)) displayed the excellent cytotoxicity and high selectivity. The mechanism research indicated compound 1 inhibited cell proliferation by binary paths of cell cycle arrest in S phase regulated by cyclin A1/A2 and apoptosis induction mediated by Bax/Bcl2 in a prooxidant manner.

Finding an efficient tetramethylated hydroxydiethylene of resveratrol analogue for potential anticancer agent.

With the improvement and advance in cancer diagnosis and treatment, the cancer is still a major cause of morbidity and mortality throughout the world. Obviously, new breakthroughs in therapies remain be urgent needed. In this work, we designed and synthesized the compound 1-4, namely resveratrol analogues with methylation of hydroxy distyrene, to further explore its new anti-cancer potential. Encouragingly, compound 1 ((E)-4,4'-(ethene-1,2-diyl)bis(3,5-dimethylphenol)) exhibited cytotoxicity superior to resveratrol in MCF 7 cells. More importantly, the compound 1 showed greater toxicity to tumor cells than that to normal cells, which proved that it could selectively kill tumor cells. The favorable results encouraged us to explore the inhibitory mechanism of compound 1 on MCF 7 cells. The research finding indicated the compound 1 inhibited tumor cell proliferation by both arresting cell cycle in S phase and apoptosis via a prooxidant manner. In addition, the results further verified compound 1 caused cell cycle arrest in S phase and apoptosis by down-regulation of the cycling A1/cycling A2 expression and the rise of Bax/Bcl-2 ratio in a p21-dependant pathway in MCF 7 cells. Therefore, these results are helpful for the effective design of anticancer reagents and the better understanding of their mechanism of action.

Rational design of a "dual lock-and-key" supramolecular photosensitizer based on aromatic nucleophilic substitution for specific and enhanced photodynamic therapy.

Photosensitizing agents are essential for precise and efficient photodynamic therapy (PDT). However, most of the conventional photosensitizers still suffer from limitations such as aggregation-caused quenching (ACQ) in physiological environments and toxic side-effects on normal tissues during treatment, leading to reduced therapeutic efficacy. Thus, integrating excellent photophysical properties and accurate carcinoma selectivity in a photosensitizer system remains highly desired. Herein, a "dual lock-and-key" supramolecular photosensitizer BIBCl-PAE NPs for specific and enhanced cancer therapy is reported. BIBCl-PAE NPs are constructed by encapsulating a rationally designed glutathione (GSH)-activatable photosensitizer BIBCl in a pH-responsive diblock copolymer. In normal tissues, BIBCl is "locked" in the hydrophobic core of the polymeric micelles due to ACQ. Under the "dual key" activation of low pH and high levels of GSH in a tumor microenvironment, the disassembly of micelles facilitates the reaction of BIBCl with GSH to release water-soluble BIBSG with ideal biocompatibility, enabling the highly efficient PDT. Moreover, benefiting from the Förster resonance energy transfer effect of BIBSG, improved light harvesting ability and 1O2 production are achieved. In vitro and vivo experiments have demonstrated that BIBCl-PAE NPs are effective in targeting and inhibiting carcinoma. BIBCl-PAE NPs show superior anticancer efficiency relative to non-activatable controls.

Correction: Rational design of a "dual lock-and-key" supramolecular photosensitizer based on aromatic nucleophilic substitution for specific and enhanced photodynamic therapy.

[This corrects the article DOI: 10.1039/D0SC01122C.].

Designing dichlorobinaphthoquinone as a prooxidative anticancer agent based on hydrogen peroxide-responsive in situ production of hydroxyl radicals.

Compared with normal cells, cancer cells harbor increased levels of reactive oxygen species (ROS) including hydrogen peroxide (H2O2), and therefore are more vulnerable to further ROS production. This biochemical difference favors the idea of developing new powerful selective prooxidative anticancer agents. However, it still remains a challenge to design them by targeting this difference. Herein, we report the designed dichlorobinaphthoquinone as a prooxidative anticancer agent which is capable of exploiting increased levels of H2O2 of cancer cells to produce in situ lethal hydroxyl radicals (HO•) and thereby kill them selectively, a design strategy inspired from Zhu et al.'s work on the molecular mechanism for metal-independent production of HO•.

A near-infrared fluorescent probe for direct and selective detection of cysteine over homocysteine and glutathione.

In this work, we have designed and synthesized the fluorescent probe 1, which showed a highly selective and sensitive response to Cys over Hcy/GSH in the test. Moreover, the color of probe solution has changed dramatically from colorless to pink with the addition of Cys within 10 min. Meanwhile, the fluorescence intensity exhibited perfectly positive correlation with concentration of Cys from 0 to 200 µM, which offered the important condition for quantitative analysis. Finally, the bioimaging and fluorescence response of probe 1 for fetal calf serum are a powerful safeguard for practical detection of Cys. Therefore, this near-infrared probe will be of great benefit for detecting Cys in the biological systems.

Chain elongation analog of resveratrol as potent cancer chemoprevention agent.

Resveratrol is identified as a natural cancer chemoprevention agent. There has been a lot of interest in designing and developing resveratrol analogs with cancer chemoprevention activity superior to that of parent molecule and exploring their action mechanism in the past several decades. In this study, we have synthesized resveratrol analogs of compounds A-C via conjugated chain elongation based on isoprene unit retention strategy. Remarkably, cytotoxic activity analysis results indicated that compound B possesses the best proliferation inhibition activity for NCI-H460 cells in all the test compounds. Intriguingly, compound B displayed a higher cytotoxicity against human non-small cell lung cancer cells (NCI-H460) compared to normal human embryonic lung fibroblasts (MRC-5). Afterward, flow cytometry analysis showed that compound B would induce cell apoptosis. We further researched the action mechanism. When NCI-H460 cells were incubated by compound B for 6 or 9 h, respectively, the intracellular reactive oxygen species (ROS) level was enhanced obviously. With elevation of intracellular ROS level, flow cytometry measurement verified mitochondrial transmembrane potential collapse, which was accompanied by the up-regulation of Bax and down-regulation of Bcl-2. More interestingly, compound B increased the expression of caspase-9 and caspase-3, which induced cell apoptosis. Moreover, compound B arrested cell cycle in G0/G1 phase. These are all to provide useful information for designing resveratrol-based chemoprevention agent and understanding the action mechanism.

Nucleus-staining with biomolecule-mimicking nitrogen-doped carbon dots prepared by a fast neutralization heat strategy.

Biomolecule-mimicking nitrogen-doped carbon dots (N-Cdots) were synthesized from dopamine by a neutralization heat strategy. Fluorescence imaging of various cells validated their nucleus-staining efficiency. The dopamine-mimicking N-Cdots "trick" nuclear membranes to achieve nuclear localization and imaging.

Carbon Quantum Dots for Zebrafish Fluorescence Imaging.

Carbon quantum dots (C-QDs) are becoming a desirable alternative to metal-based QDs and dye probes owing to their high biocompatibility, low toxicity, ease of preparation, and unique photophysical properties. Herein, we describe fluorescence bioimaging of zebrafish using C-QDs as probe in terms of the preparation of C-QDs, zebrafish husbandry, embryo harvesting, and introduction of C-QDs into embryos and larvae by soaking and microinjection. The multicolor of C-QDs was validated with their imaging for zebrafish embryo. The distribution of C-QDs in zebrafish embryos and larvae were successfully observed from their fluorescence emission. the bio-toxicity of C-QDs was tested with zebrafish as model and C-QDs do not interfere to the development of zebrafish embryo. All of the results confirmed the high biocompatibility and low toxicity of C-QDs as imaging probe. The absorption, distribution, metabolism and excretion route (ADME) of C-QDs in zebrafish was revealed by their distribution. Our work provides the useful information for the researchers interested in studying with zebrafish as a model and the applications of C-QDs. The operations related zebrafish are suitable for the study of the toxicity, adverse effects, transport, and biocompatibility of nanomaterials as well as for drug screening with zebrafish as model.

Influence of side chain structure changes on antioxidant potency of the [6]-gingerol related compounds.

[6]-Gingerol and [6]-shogaol are the major pungent components in ginger with a variety of biological activities including antioxidant activity. To explore their structure determinants for antioxidant activity, we synthesized eight compounds differentiated by their side chains which are characteristic of the C1-C2 double bond, the C4-C5 double bond or the 5-OH, and the six- or twelve-carbon unbranched alkyl chain. Our results show that their antioxidant activity depends significantly on the side chain structure, the reaction mediums and substrates. Noticeably, existence of the 5-OH decreases their formal hydrogen-transfer and electron-donating abilities, but increases their DNA damage- and lipid peroxidation-protecting abilities. Additionally, despite significantly reducing their DNA strand breakage-inhibiting activity, extension of the chain length from six to twelve carbons enhances their anti-haemolysis activity.

Tailoring 3,3'-dihydroxyisorenieratene to hydroxystilbene: finding a resveratrol analogue with increased antiproliferation activity and cell selectivity.

Four novel compounds were designed by "tailoring" 3,3'-dihydroxyisorenieratene (a natural carotenoid) based on an isoprene unit retention truncation strategy. Among them, the smallest molecule 1 (2,3,6,2',3',6'-hexamethyl-4,4'-dihydroxy-trans-stilbene) was concisely synthesized in a one-pot Stille-Heck tandem sequence, and surfaced as a promising lead molecule in terms of its selective antiproliferative activity mediated by blocking the NCI-H460 cell cycle in G1 phase. Additionally, theoretical calculations and cell uptake experiments indicate that the unique polymethylation pattern of compound 1 significantly induces a conformational change shift out of planarity and increases its cell uptake and metabolic stability. The observation should be helpful to rationally design resveratrol-inspired antiproliferative agents.

Extraordinary radical scavengers: 4-mercaptostilbenes.

In the past decade, there was a great deal of interest and excitement in developing more active antioxidants and cancer chemoprevention agents than resveratrol, a naturally occurring stilbene. In this work, eight resveratrol-directed 4-mercaptostilbenes were constructed based on the inspiration that thiophenol should be a stronger radical scavenger than phenol, and their reaction rates with galvinoxyl (GO(.)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(.)) radicals in methanol and ethyl acetate were measured by using stopped-flow UV/Vis spectroscopy at 25 °C. Kinetic analysis demonstrates that 4-mercaptostilbenes are extraordinary radical scavengers, and the substitution of the 4-SH group for the 4-OH group in the stilbene scaffold is an important strategy to improve the radical-scavenging activity of resveratrol. Surprisingly, in methanol, some of the 4-mercaptostilbenes are 10(4)-times more active than resveratrol, dozens of times to hundreds of times more effective than known antioxidants (α-tocopherol, ascorbic acid, quercetin, and trolox). The detailed radical-scavenging mechanisms were discussed based on acidified-kinetic analysis. Addition of acetic acid remarkably reduced the GO(.) and DPPH(.) radical-scavenging rates of the 4-mercaptostilbenes in methanol, a solvent that supports ionization, suggesting that the reactions proceed mainly through a sequential proton loss electron transfer mechanism. In contrast, an interesting acid-promoted kinetics was observed for the reactions of the 4-mercaptostilbenes with DPPH(.) in ethyl acetate, a solvent that weakly supports ionization. The increased ratio in rates is closely correlated with the electron-rich environment in the molecules, suggesting that the acceleration could benefit from the contribution of the electron transfer from the 4-mercaptostilbenes and DPPH(.). However, the addition of acetic acid had no influence on the GO(.)-scavenging rates of the 4-mercaptostilbenes in ethyl acetate, due to the occurrence of the direct hydrogen atom transfer. Our results show that the radical-scavenging activity and mechanisms of 4-mercaptostilbenes depends significantly on the molecular structure and acidity, the nature of the attacking radical, and the ionizing capacity of the solvent.

Synthesis and biological evaluation of hydroxylated 3-phenylcoumarins as antioxidants and antiproliferative agents.

Based on the observed biological activities of coumarins and resveratrol, we synthesized fourteen hydroxylated 3-phenylcoumarins (stilbene-coumarin hybrids) including six novel ortho-hydroxy-methoxy substituted derivatives, 1-14, by Perkin reaction. We characterized these compounds concerning their antioxidant activity against 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced pBR322 DNA strand breakage, and their antiproliferative effects on human promyelocytic leukemia HL-60 and human lung adenocarcinoma epithelial A549 cells. Structure-activity relationship information suggests that the introduction of ortho-hydroxy-methoxy groups and ortho-dihydroxy groups on the aromatic A ring could efficiently improve antiproliferative activity. Interestingly, a new derivative, 6-methoxy-7-hydroxy-3-(4'-hydroxyphenyl)coumarin, 9, behaved as a poor antioxidant but appeared to be the most potent antiproliferative agent among the compounds examined, and this activity was mediated by deregulation in cell cycle and induction of apoptosis.