Near-infrared (NIR) quantum dots (QDs) have emerged as an attractive bioimaging toolkit for exploring biological events because they can provide deep imaging penetration and low fluorescence background. However, the quantitation process of such NIR QDs generally relies on single-emission intensity change, which is susceptible to a variety of environmental factors. Herein, for the first time, we proposed a protein-directed co-template strategy to synthesize a NIR-based, dual-emission fluorescent nanohybrid (DEFN) constructed from far-red gold nanoclusters and NIR PbS QDs (AuNCs-PbS-QDs). The convenient protein-directed co-template synthesis avoids the tedious chemical coupling and modification required in conventional preparation approaches of DEFNs. Additionally, the dual-emission signals of AuNCs-PbS-QDs exhibit two well-resolved emission peaks (640 and 813 nm) separated by 173 nm, which can eliminate environmental interferences by the built-in correction of ratiometric signal, resulting in a more favorable system for bioimaging and biosensing. Next, the target-responsive capability of this NIR-based DEFN to ascorbic acid (AA) was discovered, enabling the proposed DEFN to ratiometrically detect AA with a linear range of 3-40 μM and a detection limit of 1.5 μM. This DEFN sensor possesses high selectivity, rapid response, and excellent photostability. Moreover, the feasibility of this NIR nanosensor has been fully proved by the ratiometric detection of AA for fruit internal quality assessment, in vitro cellular imaging, and in vivo imaging in nude mice.
Wine tasting is a multidimensional experience that includes contextual information from tasting environments. Formal sensory tastings are limited by the use of booths that lack ecological validity and engagement. Virtual reality (VR) can overcome this limitation by simulating different environmental contexts. Perception, sensory acceptability, and emotional responses of a Cabernet Sauvignon wine under traditional sensory booths, contextual environments, and VR simulations were evaluated and compared. Participants (N = 53) performed evaluations under five conditions: (1) traditional booths, (2) bright-restaurant (real environment with bright lights), (3) dark-restaurant (real environment with dimly lit candles), (4) bright-VR (VR restaurant with bright lights), and (5) dark-VR (VR restaurant with dimly lit candles). Participants rated the acceptability of aroma, sweetness, acidity, astringency, mouthfeel, aftertaste, and overall liking (9-point hedonic scale), and intensities of sweetness, acidity, and astringency (15-point unstructured line-scale). Results showed that context (booths, real, or VR) affected the perception of the wine’s floral aroma (dark-VR = 8.6 vs. booths = 7.5). Liking of the sensory attributes did not change under different environmental conditions. Emotional responses under bright-VR were associated with “free”, “glad”, and “enthusiastic”; however, under traditional booths, they were related to “polite” and “secure”. “Nostalgic” and “daring” were associated with dark-VR. VR can be used to understand contextual effects on consumer perceptions.
Protein acetylation of histone is an essential post-translational modification (PTM) mechanism in epigenetic gene regulation, and its status is reversibly controlled by histone acetyltransferases (HATs) and histone deacetylases (HDACs). Herein, we have developed a sensitive and label-free time-resolved luminescence (TRL) biosensor for continuous detection of enzymatic activity of HATs and HDACs, respectively, based on acetylation-mediated peptide/DNA interaction and Tb(3+)/DNA luminescent probes. Using guanine (G)-rich DNA-sensitized Tb(3+) luminescence as the output signal, the polycationic substrate peptides interact with DNA with high affinity and subsequently replace Tb(3+), eliminating the luminescent signal. HAT-catalyzed acetylation remarkably reduces the positive charge of the peptides and diminishes the peptide/DNA interaction, resulting in the signal on detection via recovery of DNA-sensitized Tb(3+) luminescence. With this TRL sensor, HAT (p300) can be sensitively detected with a wide linear range from 0.2 to 100 nM and a low detection limit of 0.05 nM. The proposed sensor was further used to continuously monitor the HAT activity in real time. Additionally, the TRL biosensor was successfully applied to evaluating HAT inhibition by two specific inhibitors, anacardic acid and C464, and satisfactory Z'-factors above 0.73 were obtained. Moreover, this sensor is feasible to continuously monitor the HDAC (Sirt1)-catalyzed deacetylation with a linear range from 0.5 to 500 nM and a detection limit of 0.5 nM. The proposed sensor is a convenient, sensitive, and mix-and-read assay, presenting a promising platform for protein acetylation-targeted epigenetic research and drug discovery.
Protein acetylation catalyzed by histone acetyltransferases (HATs) is significant in biochemistry and pharmacology because of its crucial role in epigenetic gene regulations. Herein, an antibody-free fluorescent nanosensor is developed for the facile detection of HAT activity based on acetylation protection against exopeptidase cleavage and super-quenching ability of nanomaterials. It is shown for the first time that HAT-catalyzed acetylation could protect the peptide against exopeptidase digestion. FITC-tagged acetylated peptide causes the formation of a nano-quenchers/peptide nano-complex resulting in fluorescence quenching, while the unacetylated peptide is fully degraded by exopeptidase to release the fluorophore and restore fluorescence. Four kinds of nano-quenchers, including core-shell magnetic graphitic nanocapsules (MGN), graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and gold nanoparticles (AuNPs), are comprehensively compared. MGN shows the best selectivity to recognize the acetylated peptide and the lowest detection limit because of its excellent quenching efficiency and magnetic enrichment property. With this MGN-based nanosensor, HAT p300 is detected down to 0.1 nM with wide linear range from 0.5 to 100 nM. This sensor is feasible to assess HAT inhibition and detect p300 activity in cell lysate. The proposed nanosensor is simple, sensitive, and cost-effective for HAT assay, presenting a promising toolkit for epigenetic research and HAT-targeted drug discovery.
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