Yandi Hang

Diketopyrrolopyrrole-Based Ratiometric/Turn-on Fluorescent Chemosensors for Citrate Detection in the Near-Infrared Region by an Aggregation-Induced Emission Mechanism

This work reports two new diketoprrrolopyrrole-based fluorescent chemosensors (DPP-Py1 and DPP-Py2) using symmetrical diamides as recognition groups for selective and fast detection of citrate in the near-infrared region. To our delight, DPP-Py1 is a ratiometric sensor, whereas DPP-Py2 is a turn-on fluorescent sensor. It is worth noting that DPP-Py1 has higher accuracy and sensitivity with a relatively lower detection limit (1.8 × 10(-7) M) and better stability in different pH buffers than DPP-Py2. Scanning electron microscopy, dynamic light scattering analyses, (1)H NMR titration, and 2D-NOESY NMR suggested that the fluorescence increment of the probes DPP-Py1 and DPP-Py2 for citrate could probably originate from aggregation-induced emission (AIE) on the basis of the complexation of the pyridinium-based symmetrical diamides, DPPs, with carboxyl anions of citrate. Our work may provide a simpler and faster means for qualitative and quantitative analysis of citrate through an AIE mechanism.

Probing sugar–lectin recognitions in the near-infrared region using glyco-diketopyrrolopyrrole with aggregation-induced-emission

This study describes the construction of aggregation-induced-emission (AIE)-based glycosyl probes for the sensitive and selective detection of sugar-lectin interactions in the near-infrared (NIR) region. Mannosyl and galactosyl diketopyrrolopyrrole (DPP) derivatives were effectively synthesized by the Cu(I)-catalyzed azide-alkyne 1.3-dipolar cycloaddition reaction. We observed that these glycodyes had typical AIE behaviors in a semi-aqueous solution with a strong fluorescence (FL) emission in the NIR region. In a buffer solution, the glycosyl DPPs at the quenching state showed sharply increased FL upon addition of a selective lectin that recognizes the glycosyl moiety of the compounds with nanomolar limits of detection. In contrast, addition of unselective lectins, proteins and ions did not fluctuate the FL. Scanning electron microscopy analyses suggested that the FL generation could probably be a result of AIE of the glyco-DPPs upon complexation with lectins. These glyco-DPPs, to the best of our knowledge, represent the first fluorogenic AIE-based probes that can sense lectins in the NIR region, providing insights for the further extension towards low-background in vivo targeted imaging of tissues that express a lectin.

Diketopyrrolopyrrole-based ratiometric fluorescent probe for the sensitive and selective detection of cysteine over homocysteine and glutathione in living cells

A new fluorescent probe (DPP-AC) based on diketopyrrolopyrrole with an acrylate group was designed and synthesized for the sensitive and selective detection of biological thiols. The acrylate group of DPP-AC as the receptor moiety displayed obvious ratiometric changes from red to yellow upon the addition of cysteine (Cys), and the change in fluorescence ratio (I552/I664) was over 20-fold. The limit of detection towards Cys was calculated as 84 nM; much lower than the normal concentration in living cells. More importantly, DPP-AC had outstanding selectivity towards cysteine over homocysteine (Hcy), glutathione (GSH) and other amino acids. DPP-AC was successfully employed to detect endogenous Cys in Hela cells and discriminate Cys from Hcy and GSH in living cells.

Dimethoxy triarylamine-derived terpyridine–zinc complex: a fluorescence light-up sensor for citrate detection based on aggregation-induced emission

Citrate is a vital metabolite in the Krebs cycle of nearly every aerobic cell. The abnormality in its levels in biological systems is closely associated with some diseases. Facile and efficient approaches for citrate recognition and quantification are thus in great demand. In this paper, a new sensitive and highly selective fluorescence light-up sensor (DTPA-TPY-Zn) for citrate detection has been developed by integrating an AIE motif (DTPA-TPY) with Zn2+. This probe can detect citrate in a fast and simple way by a one-step straightforward assay. It shows significant fluorescence enhancement with a relatively low detection limit (3.5 × 10−7 M). The fluorescence turn-on mechanism is ascribed to the complexation of DTPA-TPY-Zn with citrate as well as the aggregation-induced emission (AIE) properties of dimethoxy triarylamine-terpyridine (DTPA-TPY), which is confirmed using the 1H NMR and mass spectra (MS), scanning electronic microscopy and dynamic light scattering measurements. In addition, the quantification of citrate in urine makes DTPA-TPY-Zn an effective fluorometric probe for the citrate detection in real samples.

Dibenzo[a,c]phenazine-derived near-infrared fluorescence biosensor for detection of lysophosphatidic acid based on aggregation-induced emission

A new near-infrared sensitive and highly selective fluorescence turn-on detector for lysophosphatidic acid has been developed based on a dibenz[a,c]phenazine unit with aggregation-induced emission, in which the limit of detection is as low as 4.47 × 10−7 M.

Targetable N-annulated perylene-based colorimetric and ratiometric near-infrared fluorescent probes for the selective detection of hydrogen sulfide in mitochondria, lysosomes, and serum

Hydrogen sulfide (H2S) serves an effective role in biological systems as the acknowledged third endogenous gasotransmitter, so it makes great sense to detect and analyze H2S sensitively and quantitatively in subcellular environments, such as in mitochondria and lysosomes where H2S is widespread and functions as the mediator. Considering the excellent photophysical properties and multiple modification sites, N-annulated perylene (NP) was firstly chosen as the fluorophore to design a series of colorimetric and ratiometric near-infrared (NIR) fluorescent probes for the sensitive and selective detection of H2S. The probes showed near-infrared fluorescence at 681 nm in the absence of H2S. But with the addition of H2S, the NIR fluorescence decreased sharply and a new fluorescence peak at approximately 481 nm dramatically increased in a short response time, which could be clearly observed using the naked eye. Their large ratiometric fluorescence changes (about 200 nm), excellent selectivity and stability would be helpful for its detection in biological systems, and the limit of detection of the probe was calculated down to 139 nM. The reaction mechanism was studied as well. The targetable probes (Mito-NPNM and Lyso-NPNM) were also successfully employed to detect endogenous H2S in the mitochondria and lysosomes of living cells respectively. Besides, these probes were successfully applied to quantify H2S at low concentrations in serum where H2S levels are of great significance as an important indicator of various diseases.

A red fluorescent turn-on chemosensor for Al3+ based on a dimethoxy triphenylamine benzothiadiazole derivative with aggregation-induced emission

Aluminum is a known neurotoxin to organisms and believed to cause Alzheimers disease, osteomalacia, and breast cancer. Therefore, effective tools for Al3+ recognition are in great demand. In this study, a new, sensitive, and highly selective red turn-on chemosensor (TB-COOH) for Al3+ was prepared by combining the dimethoxy triarylamine benzothiadiazole motif and carboxyl group, where the benzothiadiazole derivative functioned as an aggregation-induced emission (AIE) moiety and the carboxyl motif functioned as the recognition site for Al3+. This chemosensor showed significant fluorescence enhancement upon selective addition of Al3+ and a relatively low detection limit (1.5 × 10−7 M). The fluorescence turn-on mechanism was ascribed to the aggregation of TB-COOH after complexation with Al3+, which was confirmed by 1H NMR and FT-IR spectroscopies and scanning electronic microscopy. Furthermore, benefiting from its good water solubility and biocompatibility, imaging detection and real-time monitoring of Al3+ in living HeLa cells were successfully achieved.

A pH-sensitive multifunctional fluorescent probe based on N-annulated perylene for the sensitive and selective detection of hypochlorous acid

Hypochlorous acid (HOCl) is a representative reactive oxygen species (ROS), which play important roles in signaling and homeostasis. And it is also an important cobleaching agent and disinfectant in industry and life. Therefore, it is of significant importance to detect HOCl accurately for the diagnosis or treatment of various diseases and the protection of the environment. Considering its excellent photophysical properties, N-annulated perylene (NP) was chosen as the fluorophore to design a multifunctional fluorescent probe for the sensitive and selective detection of HOCl for the first time. Benefiting from the introduction of a piperazine moiety, the probe became pH-sensitive due to the photo-induced electron transfer (PET) process. In a neutral environment, PNPM was a turn-on probe towards HOCl with a limit of detection of 31.7 nM. However, PNPM became a ratiometric fluorescent probe under weakly acidic conditions with a better limit of detection (15.3 nM). This amazing property meant that the probe possessed the ability to detect pH and HOCl at the same time. Therefore, PNPM was successfully employed to detect HOCl in fetal bovine serum and different water samples, where it could also monitor the pH values of the solution, showing its huge potential in practical applications.

A light-up fluorescent probe for citrate detection based on bispyridinum amides with aggregation-induced emission feature

Citrate is an important intermediate in the citric acid cycle, a vital metabolic pathway for animals, plants and bacteria. It is of great significance to detect its levels in human beings because several diseases may cause the abnormal of citrate. In this paper, a new turn-on fluorescent sensor (TPE-Py) using the classic tetraphenylethylene (TPE) as the aggregation-induced emission (AIE) fluorophore and bipyridinium-based amides as the recognition receptor has been synthesized for the detection of citrate. The probe exhibits good selectivity and sensitivity to citrate with a relatively low detection limit (1.0 × 10-7M). The enhancement of the fluorescence is relevant with the AIE property based on the complexation of TPE-Py with citrate caused by the hydrogen bonding and electrostatic interactions between the bipyridinium diamides and citrate, which has been proved by 1H NMR and mass spectra titration, scanning electronic microscope and dynamic light scattering analyses. More importantly, the quantification of citrate in artificial urine may develop TPE-Py fluorometric probe for the citrate detection in real biosystems.

Galactose functionalized diketopyrrolopyrrole as NIR fluorescent probes for lectin detection and HepG2 cell targeting based on aggregation-induced emission mechanism

Since the elucidation that sugar-lectin interactions contribute to the understanding of “Glycomics”, how to construct glycosensors with rapid response, excellent sensitivity and selectivity is of intense research interest. Herein, we report the design of three NIR emissive glyco-probes based on diketopyrrolopyrrole (DPPs) conjugated with two (DPPG), four (DPPF-G) and six (DPPS-G) galactose groups. All three molecules could probe lectins with excellent sensitivity and selectivity. The increase of glyco-DPP emission in NIR region upon interaction with lectin is due to the aggregates formation induced by sugar-lectin interactions, which have been verified by dynamic light scattering (DLS) and scanning electronic microscope (SEM) analysis. Due to the multiple glyco-ligands on DPPS-G, it has been successfully used to stain HepG2 cells through interactions between galactose and asialogly-coprotein (ASGP-R), which are overexpressed on the surface of HepG2 cells.