Xiaowei Cao

A near-infrared fluorescent turn-on probe for fluorescence imaging of hydrogen sulfide in living cells based on thiolysis of dinitrophenyl ether

We have constructed a novel NIR fluorescent turn-on hydrogen sulfide probe suitable for fluorescent imaging in living cells based on thiolysis of dinitrophenyl ether.

A Near-Infrared Fluorescence Turn-On Sensor for Sulfide Anions

The first NIR fluorescent sensor for sulfide anions was constructed based on the displacement approach. The sensing ensemble is composed of a cyanine dye, a piperazine linker, an 8-aminoquinoline ligand, and copper. The favorable attributes of the sensor include a large NIR fluorescence turn-on signal in aqueous ethanol, high sensitivity, and high selectivity. The transition-metal-based displacement strategy may open an avenue for development of NIR fluorescent sensors for a wide variety of anion targets.

Ratiometric Sensing of Fluoride Anions Based on a BODIPY-Coumarin Platform

Based on a new coumarin-BODIPY platform, compound 4 was rationally designed and synthesized as a novel ratiometric fluorescent sensor for fluoride anions. The sensor exhibited a large red shift (88 nm) in absorption and a drastic ratiometric fluorescent response (I(472)/I(606) = 17.4) to fluoride anions. Density function theory and time-dependent density function theory calculations were conducted to rationalize the optical response of the sensor.

A Ratiometric Fluorescent Probe for Thiols Based on a Tetrakis(4-hydroxyphenyl)porphyrin–Coumarin Scaffold

In this work, we have designed and synthesized the compound Ratio-HPSSC, based on a tetrakis(4-hydroxyphenyl)porphyrin-coumarin scaffold, as a new ratiometric fluorescent probe for thiols. The ratiometric probe Ratio-HPSSC is highly selective and sensitive to thiols. Importantly, the novel ratiometric probe exhibited a remarkable change in emission color from red to blue. This key feature allows Ratio-HPSSC to be employed for thiol detection by simple visual inspection. Furthermore, we have demonstrated that Ratio-HPSSC is suitable for ratiometric fluorescence imaging of thiols in living cells. We believe that the new ratiometric probe will find interesting applications in chemistry, biology, and medicine.

Double Functional Group Transformations for Fluorescent Probe Construction: A Fluorescence Turn-On Probe for Thioureas

The development of fluorescent probes has attracted continuing attention due to the simplicity and high sensitivity of fluorescence detection. Recently, analyte-mediated organic reactions have been extensively employed to design a wide variety of fluorescent probes. In many reaction-based fluorescent probes, the fluorescence properties of the dyes are regulated by a single functional group. Thus, only a single functional group transformation is involved in the analytemediated reactions for the fluorescence response (Figure 1, top). However, the development of fluorescent probes based on a single functional group transformation with high selectivity is still very challenging, since structurally and chemically related analytes may compete with the same key functional group in the probes. For instance, a fluorescent probe with an electrophilic carbonyl group is known to react with strong nucleophiles, such as Cys and CN . Consequently, the probe has poor selectivity for these distinct analytes. On the other hand, fluorescence turn-on probes may be designed based on the double functional group transformation strategy provided that the fluorescence intensity of a dye is suppressed by two different functional groups (Figure 1, bottom). Obviously, the intense fluorescence is restored only after both functional groups are transformed by the target analyte. However, if neither, or only one, functional group is transformed by other analytes, the fluorescence of the dye may remain very dim. Thus, a double functional group transformation strategy may allow the probe to show selectivity for the target analyte over other potentially competing species that can incite no, or only single, functional group transformation on the probe. This design approach, in principle, may be favorable for improvement of selectivity, as double and single functional group transformation products may have discrete emission profiles. Thioureas have been widely used as fungicides or accelerators of sprouting in dormant tubers in agriculture and as vulcanization accelerators in industry. However, the toxicity of thioureas is associated with diseases, such as dermatitis, pulmonary edema, chronic goitrogenic difficulties, and thyroid and liver tumors. Thus, it is critical to detect thioureas. To the best of our knowledge, fluorescence turn-on probes for thioureas that can operate in aqueous solution have not been previously developed. In this contribution, we report the development of the first fluorescence turn-on thiourea probe 1 (Scheme 1) by the double functional group transformation strategy. Probe 1 is composed of a coumarin dye, a carbonyl group, and a bromide group. The choice of the carbonyl and bromide groups is based on the following considerations: 1) The carbonyl group may significantly decrease the fluorescence of the coumarin dye due to the intersystem crossing from singlet (n, p*) to triplet state (p, p*). In addition, the bromide moiety is also a well-known fluorescence quencher in light of its heavy atom effect. Thus, these two fluorescence [a] Prof. W. Lin, X. Cao, L. Yuan, Y. Ding State Key Laboratory of Chemo/Biosensing and Chemometrics College of Chemistry and Chemical Engineering, Hunan University Changsha, Hunan 410082 (P.R. China) Fax: (+86) 731-88821464 E-mail : weiyinglin@hnu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201000244. Figure 1. Top: development of reaction-based fluorescence turn-on probes by the single functional group transformation approach. Bottom: development of reaction-based fluorescence turn-on probes by the double functional group transformation strategy.