Yifeng Han

A depropargylation-triggered spontaneous cyclization based fluorescent “turn-on” chemodosimeter for the detection of palladium ions and its application in live-cell imaging

A novel depropargylation-triggered spontaneous cyclization reaction based fluorescent turn-on chemodosimeter for the detection of palladium ions has been rationally designed and developed. Based on the specific reactivity of the palladium promoted hydrolysis reaction, the probe exhibited a high selectivity and sensitivity for palladium ions. Furthermore, the probe was successfully used for fluorescence imaging of Pd2+ in living cells.

A reactive probe for Cu2+ based on the ESIPT mechanism and its application in live-cell imaging

A new reactive probe based on an excited-state intramolecular proton transfer (ESIPT) mechanism is reported for the selective detection of Cu2+ by the copper induced hydrolysis reaction. The probe is demonstrated to detect Cu2+ in living cells.

A Highly Specific Probe for Sensing Hydrogen Sulfide in Live Cells Based on Copper-Initiated Fluorogen with Aggregation-Induced Emission Characteristics

Here we reported the first fluorescent probe with aggregation-induced emission characteristics, namely AIE-S, for the detection of hydrogen sulfide (H2S) in live cells. The detection system is selective for complicated biological application and the response is fast enough to complete within seconds. Moreover, the probe exhibits the unique advantage of being immune to aggregation-caused quenching which is a detrimental phenomenon limiting the application of most current available H2S fluorescent probes. The detection mechanism was investigated and postulated to be S2- initiated de-coordination and thereafter aggregation of the AIE-S complex.

Combining the PeT and ICT mechanisms into one chemosensor for the highly sensitive and selective detection of zinc

A novel fluorescent sensor (ZS1) based on the dual-mechanism of PeT/ICT for the highly sensitive and selective detection of Zn2+ was designed and synthesized. ZS1 displays remarkable selectivity for Zn2+ with an enhanced red-shift in both absorption and emission, which results from the Zn2+-triggered deprotonation of its amide group. ZS1 could detect as low as 7.2 × 10−9 M Zn2+ with an association constant value of 6.27 × 104 M−1. More importantly, it displays specific and sensitive recognition of Zn2+ and especially avoids the interference of Cd2+ in aqueous solution. The probe was also demonstrated to detect Zn2+ in living cells.

A highly sensitive and water soluble fluorescent probe for rapid detection of hydrogen sulfide in living cells

A highly sensitive and specific fluorescent probe has been developed for the rapid detection of H2S in living cells. This probe exhibits the unique qualities of quick response, low detection limit, excellent water solubility and good membrane permeability. Its potential for biological applications has been demonstrated by imaging H2S in living cells.

Novel Fluorinated 8-Hydroxyquinoline Based Metal Ionophores for Exploring the Metal Hypothesis of Alzheimer’s Disease

Zinc, copper, and iron ions are involved in amyloid-beta (Aβ) deposition and stabilization in Alzheimers disease (AD). Consequently, metal binding agents that prevent metal-Aβ interaction and lead to the dissolution of Aβ deposits have become well sought therapeutic and diagnostic targets. However, direct intervention between diseases and metal abnormalities has been challenging and is partially attributed to the lack of a suitable agent to determine and modify metal concentration and distribution in vivo. In the search of metal ionophores, we have identified several promising chemical entities by strategic fluorination of 8-hydroxyquinoline drugs, clioquinol, and PBT2. Compounds 15-17 and 28-30 showed exceptional metal ionophore ability (6-40-fold increase of copper uptake and >2-fold increase of zinc uptake) and inhibition of zinc induced Aβ oligomerization (EC50s < ∼5 μM). These compounds are suitable for further development as drug candidates and/or positron emission tomography (PET) biomarkers if radiolabeled with (18)F.

A facile naphthalene-based fluorescent chemodosimeter for mercury ions in aqueous solution

A facile naphthalene-based fluorescence “turn-on” chemodosimeter, 2-((2-(vinyloxy)naphthalen-1-yl)methylene)-malononitrile (MS1), for rapid, selective and sensitive detection of Hg2+ by mercury-promoted hydrolysis of the vinylether group has been reported. The probe displayed a fast response time, and a sensitive fluorescence response (100-fold fluorescence enhancement) to the detection of Hg2+ in aqueous solution.

A highly sensitive hemicyanine-based fluorescent chemodosimeter for mercury ions in aqueous solution and living cells

A novel hemicyanine-based fluorescence turn-on chemodosimeter for Hg2+ by mercury triggered hydrolysis of the vinyl ether group has been reported. The probe has the unique advantages of easy-preparation, good water solubility, excellent selectivity, high sensitivity, and fast response time (∼60 s) towards Hg2+ in aqueous solution. Furthermore, the probe is demonstrated to be qualified to detect Hg2+ in living cells.

A new ESIPT-based fluorescent probe for highly selective and sensitive detection of hydrogen sulfide and its application in live-cell imaging

A new excited-state intramolecular proton transfer (ESIPT) based fluorescent probe for the detection of hydrogen sulfide has been reasonably designed and developed. The probe operates by H2S-mediated reduction of hydroxylamine to amine and exhibits high selectivity and sensitivity under mild conditions. Furthermore, the probe was successfully used for fluorescence imaging of H2S in living cells.

A Fluorogenic Probe for Ultrafast and Reversible Detection of Formaldehyde in Neurovascular Tissues

Formaldehyde (FA) is endogenously produced in live systems and has been implicated in a diverse array of pathophysiological processes. To disentangle the detailed molecular mechanisms of FA biology, a reliable method for monitoring FA changes in live cells would be indispensable. Although there have been several fluorescent probes reported to detect FA, most are limited by the slow detection kinetics and the intrinsic disadvantage of detecting FA in an irreversible manner which may disturb endogenous FA homeostasis. Herein we developed a coumarin-hydrazonate based fluorogenic probe (PFM) based on a finely-tailored stereoelectronic effect. PFM could respond to FA swiftly and reversibly. This, together with its desirable specificity and sensitivity, endows us to track endogenous FA in live neurovascular cells with excellent temporal and spatial resolution. Further study in the brain tissue imaging showed the first direct observation of aberrant FA accumulation in cortex and hippocampus of Alzheimers mouse model, indicating the potential of PFM as a diagnostic tool.