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Quantum dots (QDs) have attracted extensive attention in biomedical applications， because of their broad excitation spectra, narrow and symmetric emission peaks etc. Furthermore, near-infrared (NIR) QDs have further advantages including low autofluorescence, good tissue penetration and low phototoxicity. In this work, the electrostatic interaction and fluorescence resonance energy transfer (FRET) between NIR CdTe/CdS QDs and cationic conjugated polymer (CCP) was studied for the first time. Based on the newly discovered phenomena and the result that hydrogen peroxide (H2O2) can efficiently quench the fluorescence of NIR CdTe/CdS QDs, a novel NIR ratiometric fluorescent probe for determination of H2O2 and glucose was developed. Under the optimized conditions, the detection limit of H2O2 and glucose assay were 0.1mM and 0.05mM (S/N=3), with a linear range of 0.2-4mM and 0.1-5mM, respectively. Because of the NIR spectrum, this ratiometric probe can be also applied for the determination of glucose in whole blood samples directly, providing a valuable platform for glucose sensing in clinic diagnostic and drug screening.

Reversible protein acetylation, one of the key types of post-translational modifications, is composed of histone acetylation and deacetylation, which is typically catalyzed by histone acetyltransferases (HATs) and histone deacetylases (HDACs) respectively. Herein, a label-free fluorescent method has been established for the homogeneous bioassay of HAT/HDAC activity and respective inhibitors. The proposed approach is primarily based on the electrostatic interaction between G-quadruplexes (G4s) and acetylation-related peptides, which results in marked change of fluorescent intensity of G4/Thioflavin T (ThT) complexes. This HAT (p300) activity assay is exceedingly sensitive and selective, with a linear range from 0.1 to 120nM and a detection limit of 0.05nM. Moreover, this biosensor is feasible to detect the HDAC (Sirt1) activity with a linear range from 1 to 450nM and a detection limit of 1nM. The potency of this assay is further demonstrated by detecting HAT/HDAC activity in cell lysates and evaluating HAT and HDAC-targeted inhibitors, C464 and EX 527, respectively. The proposed assay is convenient, label-free and cost-efficient, which is promising for HAT/HDAC-targeted epigenetic research and pharmaceutical development.