Aggregation-induced emission-active antibacterial hydrogel with self-indicating ability for real-time monitoring of drug release process

Although antibacterial hydrogels are emerging as promising biomaterials for effective inhibition of bacterial infections, monitoring their dynamic release behaviors in a visual manner remains greatly challenging. Herein, non-conjugated luminescent polymers (NCLPs) with aggregation-induced emission (AIE) characteristics are used for the first time to develop a visualization strategy to monitor the release process of the drug-loaded hydrogel. The novel antimicrobial peptide polymers with intrinsic AIE effect, namely nanoengineered peptide-grafted hyperbranched polymers (NPGHPs), are encapsulated in an anionic polyelectrolyte to construct the AIE-active fluorescent polymeric hydrogel (NPGHPs/SA gel). Interestingly, the rigid environment mediated by hydrogen bonding and electrostatic interaction contributes to promoting the unconventional luminescence of fluorescent clusters. Moreover, the successive drug release process of NPGHPs/SA gel can be tracked in real time by using fluorescence microscopy. The hydrogel also has potent antibacterial activities against Gram-negative bacteria (E. coli, P. aeruginosa) and Gram-positive bacteria (S. aureus, B. subtilis). Overall, this work not only provides an advanced biomedical material with broad-spectrum antibacterial ability but also opens a facile avenue up for the investigation of drug release from gel systems.     

Dendritic polyurethane-based prodrug as unimolecular micelles for precise ultrasound-activated localized drug delivery

Ultrasound has been recognized as an exciting tool to enhance the therapeutic efficacy in tumor chemotherapy owing to the triggered drug release, facilitated intracellular drug delivery, and improved spatial precision. Aiming for a precise localized drug delivery, novel dendritic polyurethane-based prodrug (DOX-DPU-PEG) was fabricated with a drug content of 18.9% here by conjugating DOX onto the end groups of the functionalized dendritic polyurethane via acid-labile imine bonds. It could easily form unimolecular micelles around 38 nm. Compared with the non-covalently drug-loaded unimolecular micelles (DOX@Ph-DPU-PEG), they showed excellent pH/ultrasound dual-triggered drug release performance, with drug leakage of only 4% at pH 7.4, but cumulative release of 14% and 88% at pH 5.0 without and with ultrasound, respectively. The ultrasound responsiveness was attributed to the unique strawberry-shaped topological structure of the DOX-DPU-PEG, in which DOX was embedded in the skin layer of the hydrophobic DPU cores. With ultrasound, the DOX-DPU-PEG unimolecular micelles possessed enhanced tumor growth inhibition than free DOX but showed no obvious cytotoxicity on the tumor cells without ultrasound. Such feature makes them promising potential for precise localized drug delivery.     

一种基于萘酰亚胺的检测细胞内pH值的荧光探针及其生物成像应用

细胞内溶酶体的pH值对细胞自噬、吞噬、酶加工等各项生命活动有着重要影响.细胞核是真核细胞中最大的细胞器,控制着生物体内的遗传和代谢过程,参与代谢过程的酶对pH值的变化很敏感.因此,研究细胞体内的pH值变化至关重要.我们设计并以简单的两步反应合成了一种新型荧光探针NpH-1.该探针以萘酰亚胺作为荧光团,以吗啉基团作为对p...     

Accurate determination of the anticancer prodrug simmitecan and its active metabolite chimmitecan in various plasma samples based on immediate deactivation of blood carboxylesterases

Simmitecan (L-P) is an anticancer ester prodrug, which involves activation to chimmitecan (L-2-Z). In the current study, a liquid chromatography/tandem mass spectrometry-based method was developed for simultaneous determination of L-P and L-2-Z in various plasma samples. Because L-P is rapidly converted to L-2-Z by blood carboxylesterase during and after sampling, which hampers accurate determination of L-P and L-2-Z in the biological samples, different carboxylesterase inhibitors were tested. As a result, bis(4-nitrophenyl)phosphate gave the best results with respect to inhibitory capability, hemolysis, and matrix effects and was used to deactivate blood carboxylesterases when sampling. The plasma samples were precipitated with acetonitrile and the resulting supernatants were separated using a pulse gradient method on a C18 column. Irinotecan and camptothecin were used as internal standards for quantification of L-P and L-2-Z, respectively. Protonated L-P, L-2-Z and their internal standards were generated by electrospray ionization and their precursor-product ion pairs (m/z 599→124, 405→361, 587→195, and 349→305, respectively) were used for measurement. The newly developed bioanalytical assay processed favorable accuracy and precision with lower limits of quantification of 2.1 nM for L-P and 3.4 nM for L-2-Z, and was successfully applied to pharmacokinetic studies in tumor-bearing nude mice, rats, and dogs. There are substantial species differences in the ester activity. The experimental strategies illustrated in our report may be adopted for measurement of other prodrugs (including irinotecan) or drugs subject to ester hydrolysis, as well as their metabolites, in biological matrices.     

A new fluorescent probe with ultralow background fluorescence for imaging of endogenous cellular selenol under oxidative stress

A new fluorescent probe (Rhod-Sec) for selenol detection with ultralow background fluorescence have been developed in this paper, which showed a 380-fold off-on fluorescence response, and can be applied to visualize the fluctuation of selenol in HepG2 cells through LPS-induced cells oxidation resistance.     

一种基于查尔酮衍生物的荧光探针对巯基氨基酸的检测及细胞成像

生物硫醇(如半胱氨酸(Cys)、同型半胱氨酸(Hcy)及谷胱甘肽(GSH))与生物体和细胞中的许多生理和病理过程密切相关。荧光探针是对生物硫醇灵敏检测与成像的有力工具。本文合成了一种可检测生物硫醇的基于2′-羟基查尔酮荧光团开启型荧光探针1。探针中的2,4-二硝基苯磺酸酯基团既作为反应识别基团,又作为荧光猝灭基团。在DMSO/Tris(体积比8/2,pH=8.4)中,探针1与生物硫醇反应后释放出前体化合物3,3具有激发态分子内质子转移(ESIPT)和聚集诱导发光(AIE)特性,从而导致长波长荧光发射及较大的斯托克斯位移。探针1具有合成简单、灵敏度高、选择性高、细胞毒性低等优点,可以方便地检测溶液和活细胞中的生物硫醇。     

Biomarker-targeted fluorescent probes for breast cancer imaging

This review summarized fluorescent probes for breast cancer imaging according to different biomarkers probes recognized.     

A novel off-on fluorescent probe for specific detection and imaging of cysteine in live cells and in vivo

Cysteine(Cys) plays a pivotal role in many physiological and pathological processes,including detoxification and protein synthesis.The abnormal levels of Cys are linked to many diseases.In this study,a novel red-emitting off-on fluorescent probe Cys-TCF was masterly constructed for discriminative detection of Cys.After a series of experimental assessment,Cys-TCF displayed higher selectivity and sensitivity for Cys over other biothilols with a low detection limit(0.04 μmol/L).More notably,the pro...     

Emerging applications of near-infrared fluorescent metal nanoclusters for biological imaging

Recent advances in the development of near-infrared fluorescent metal nanoclusters for bioimaging applications have been thoroughly overviewed.     

Gas-phase acidity of sulfonamides: implications for reactivity and prodrug design

A computational study at the density functional theory level was performed on bioactive and model sulfonamides with the aim of determining the factors affecting the acidity of the sulfonamido group. The effects of introducing different substituents at either the para-aryl or the N¹-sulfonamide positions were independently analyzed. A linear correlation was found between sulfonamide acidity and the Hammett constants or charge of the SO₂ group of substituents at the para-aryl position. Most N¹-substituents were taken from bacteriostatic sulfonamide structures and presented a more complex behavior, possibly due to a conjugation of steric and electronic factors. In the latter situation, sulfonamide acidity and the charge of the SO₂ group were not linearly correlated. Interestingly, the acidity of the sulfonamido group was found to be correlated with the reactivity of sulfa drugs towards acylating agents. The implications for the design of suitable sulfonamide prodrugs are discussed.     

A bestatin-based fl uorescent probe for aminopeptidase N cell imaging

Aminopeptidase N (APN) is an important drug target and biomarker for various tumors. The current work characterizes a novel APN-targeted fluorescent probe (Bes-Green, 2) that manifests comparable inhibitory activity with Bestatin. This probe has capacity of tightly binding to the APN for imaging endogenous APN in living human ovarian clear cell carcinoma cells (ES-2) and has potential application in biological study of cellular APN.     

Sensing carboxylesterase 1 in living systems by a practical and isoform-specific fluorescent probe

A practical and isoform-specific fluorescent probe based on BIDIPY dye have been designed, synthesized and well characterized for sensing CES1 activities in various biological systems such as living cells, tissues and zebrafish.     

An efficient one-pot reaction for selective fluorimetric determination of cefpodoxime and its prodrug

Cefpodoxime proxetil (CFP), an oral third-generation cephalosporin, is a prodrug that is de-esterified in vivo to its active metabolite, cefpodoxime acid (CFA). Therefore, this study aimed to develop a facile and efficient one-pot reaction for selective and sensitive determination of CFA and its prodrug (CFP). The method was based on single-step reaction between CFP or CFA and 1,2-naphthoquinone-4-sulfonate (NQS) as a selective derivatizing reagent in alkaline medium without heating, extraction or reduction steps as usual for NQS derivatization reactions. The fluorescence of the formed NQS-derivative was monitored directly at emission wavelength of 440 nm after excitation at 330 nm. The method can easily be implemented in plating facilities by operators and/or incorporated in on-line derivatization reaction. The correlation coefficients of 0.9991 and 0.9984 were obtained in the concentration ranges of 50-2000 ng mL⁻¹ for CFA and CFP, respectively. The detection limits were 9.17 and 9.48 ng mL⁻¹ for CFA and CFP, respectively. The method was validated in accordance with the requirements of ICH guidelines and shown to be suitable for their efficient and sensitive determinations. The developed method was successfully applied for selective determination of CFP in pure form and in pharmaceutical dosage forms as well as CFA in human urine after single dose of CFP without prior need for separation. The method is valuable for quality control laboratories for monitoring of CFP and its active metabolite CFA.     

Synthesis of a (B12H11S) containing glucuronoside as potential prodrug for BNCT

A B₁₂H₁₁SH²⁻ containing glycoside of glucuronic acid has been prepared, for possible use as prodrug in BNCT. The synthesis was carried out by the Koenigs-Knorr reaction of the acetylated glucopyranosyluronate bromide with the nucleophile cyanoethylthioundecahydro-closo-dodecaborate(2−). After removal of the cyanoethyl-group, deacetylation and saponification of the reaction product tris(tetramethylammonium)-[S-(β-d-glucuronate)-thio] undecahydro-closo-dodecaborate(3−) could be prepared.     

A Hg(II)-specific probe for imaging application in living systems and quantitative analysis in environmental/food samples

Mercury ions are highly toxic and can accumulate along food chains in water, soil, crops and animals. Effective detection of mercury ions in various media is of great significance for maintaining the ecological environment and protecting people’s health. In this work, a mercury ions specific fluorescent probe was developed by a simple one-step reaction of commercial substrates of 4-chloro-7-nitro-2,1,3-benzoxadiazole and 1-(2-aminoethyl)-4-methylpiperazine. Investigation on sensing behavior showed that this probe had high sensitivity and selectivity towards mercury ions. Furthermore, this probe could be used as a tool to track the level of mercury ions in living system. In living cells, the probe with green emission emitted a bright red fluorescence when it was bound to mercury ions. In Arabidopsis thaliana, similar red emission could be detected from the root tip and stalk when A. thaliana was grown in culture medium containing mercury ions. The imaging in zebrafish showed that mercury ions were mainly concentrated in the stomach and head of zebrafish. Especially, this probe could be applied in quantitative analysis of mercury ions in tap water, green tea, sea shrimp and soil. This work provided a practical tool for the detection of mercury ions in living systems and quantitative analysis in real samples.     

Regioselective synthesis and initial evaluation of a folate receptor targeted rhaponticin prodrug

To improve the therapeutic effect of rhaponticin(RHA),a folate receptor(FR) targeted RHA prodrug was designed and regioselectively synthesized by utilizing a hydrophilic peptide spacer linked to folic acid(FA) via a releasable disulfide linker.A series of biological evaluation was investigated in vitro and in vivo.The positive results of biological investigations warrant further preclinical study before this novel targeted chemotherapeutic is considered for clinical investigation.     

A novel fluorescent probe with a large Stokes shift for real-time imaging mitochondria in different living cell lines

Fluorescent dyes with large Stokes shift play a key role in avoiding self-quenching and scattered light of dyes in the process of biological imaging. In this work, a novel mitochondria-targetable fluorescent dye (PI-C2) with large Stokes shift (e. g. Maximum value is 219 nm in DMSO) have been developed. Compared to the commercial mitochondria probes MTR and MTG (Less than 30 nm in various solution), the newly constructed PI-C2 has a much larger Stokes shift in various solutions (169–219 nm in various solutions). Furthermore, the probe can successfully be applied for sensing mitochondria, and exhibited excellent photostability in different living cell lines. The novel fluorescent platform with the large Stokes may be extended to construct powerful fluorescent probes with large Stokes shift for detecting a wide variety of biomolecules in mitochondria.     

Long-term super-resolution imaging of mitochondrial dynamics

Monitoring dynamics of mitochondria has become an essential approach to explore the function of mitochondria in living cells with the emergence of super-resolution fluorescence microscopy. However, long-term super-resolution imaging of mitochondria is still challenging due to the lack of photostable fluorescent probes and stable mitochondria-specific markers which are not affected by the changes of mitochondrial membrane potential. Here, we introduce a method for long-term imaging mitochondrial dynamic through the SNAP-tag fluorogenic probe based on 4-azetidinyl-naphthalimide derivatives. Using structured illumination microscopy (SIM), we observed the fusion and fission of mitochondria over a course of 16 min at 109 nm resolution. Furthermore, the interactions as well as fusion between mitochondria and lysosomes were studied during mitophagy at the nanoscale. Convincingly, the combination of SNAP-tag fluorogenic probes and super-resolution fluorescence microscopy will offer a new way to monitor dynamic mitochondria in living cells.     

A logic gate-based fluorogenic probe for Hg detection and its applications in cellular imaging

A new colorimetric and fluorogenic probe (RN₃) based on rhodamine-B has been successfully designed and synthesized. It displays a selective response to Hg²⁺ in the aqueous buffer solution over the other competing metals. Upon addition of Hg²⁺, the solution of RN₃ exhibits a ‘naked eye’ observable color change from colorless to red and an intensive fluorescence with about 105-fold enhancement. The changes in the color and fluorescence are ascribed to the ring-opening of spirolactam in rhodamine fluorophore, which is induced by a binding of the constructed receptor to Hg²⁺ with the association and dissociation constants of 0.22 × 10⁵ M⁻¹ and 25.2 μM, respectively. The Job's plot experiment determines a 1:1 binding stoichiometry between RN₃ and Hg²⁺. The resultant “turn-on” fluorescence in buffer solution, allows the application of a method to determine Hg²⁺ levels in the range of 4.0–15.0 μM, with the limit of detection (LOD) calculated at 60.7 nM (3σ/slope). In addition, the fluorescence ‘turn-off’ and color ‘fading-out’ happen to the mixture of RN₃-Hg²⁺ by further addition of I⁻ or S²⁻. The reversible switching cycles of fluorescence intensity upon alternate additions of Hg²⁺ and S²⁻ demonstrate that RN₃ can perform as an INHIBIT logic gate. Furthermore, the potential of RN₃ as a fluorescent probe has been demonstrated for cellular imaging.     

A GSH-responsive PET-based fluorescent probe for cancer cells imaging

An efficient PET-based probe, in which the ferrocene quencher and the naphthalimide fluorophore are linked by a disulfide bond, has been developed. This probe can be activated by GSH with fluorescence a turn-on response for blocking the PET process. In addition, it was successfully applied for distinguishing cancer cells from normal cells