Unusual Hypochlorous Acid (HClO) Recognition Mechanism Based on Chlorine–Oxygen Bond (Cl−O) Formation

One of the most important endogenous reactive oxygen species, hypochlorous acid (HClO), is involved in numerous pathological and physiological processes. Herein, a near-infrared fluorescence probe (CyHR) was designed and synthesized for ultrafast (within 0.2 s), sensitive (limit of detection=39.44 nm ), and selective response to HClO. The reaction mechanism was systematically analyzed by MS, ¹H NMR spectroscopy, HPLC-MS techniques, and theoretical calculations. The results indicated that HClO can be recognized by CyHR, which is based on chlorine–oxygen (Cl−O) bond formation. To the best of our knowledge, this study is the first to find Cl−O bonds among organic aromatic compounds, given that Cl−O bonds are common among inorganics. Through biological experiments, CyHR was successfully applied to image exogenous and endogenous HClO in macrophage cells (RAW 264.7). Thus, CyHR is a promising tool for HClO-related physiological and pathological studies and may provide a means for designing HClO-specific fluorescence probes.     

Multi-C−C/C−N-Coupled Light-Emitting Aliphatic Terpolymers: N−H-Functionalized Fluorophore Monomers and High-Performance Applications

To circumvent costly fluorescent labeling, five nonconventional, multifunctional, intrinsically fluorescent aliphatic terpolymers ( 1 – 5 ) have been synthesized by C−C/C−N-coupled, solution polymerization of two non-emissive monomers with protrusions of fluorophore monomers generated in situ. These scalable terpolymers were suitable for sensing and high-performance exclusion of Cu^II, logic function, and bioimaging. The structures of the terpolymers, in situ attachment of fluorescent monomers, aggregation-induced enhanced emission, bioimaging ability, and super adsorption were investigated by ¹H and ¹³C NMR, EPR, FTIR, X-ray photoelectron, UV/Vis, and atomic absorption spectroscopy, thermogravimetric analysis, high-resolution transmission electron microscopy, dynamic light scattering, solid-state fluorescence, fluorescence imaging, and fluorescence lifetime measurements, as well as by isotherm, kinetics, and thermodynamic studies. The geometries and electronic structures of the fluorophores and the absorption and emission properties of the terpolymers were examined by DFT, time-dependent DFT, and natural transition orbital analyses. For 1 , 2 , and 5 , the limits of detection were determined to be 1.03×10⁻⁷, 1.65×10⁻⁷, and 1.77×10⁻⁷ m , respectively, and the maximum adsorption capacities are 1575.21, 1433.70, and 1472.21 mg g⁻¹, respectively.     

Polyethylenimine‐Based Nanogels for Biomedical Applications

Nanogels (NGs) are 3‐dimensional (3D) networks composed of hydrophilic or amphiphilic polymer chains, allowing for effective and homogeneous encapsulation of drugs, genes, or imaging agents for biomedical applications. Polyethylenimine (PEI), possessing abundant positively charged amine groups, is an ideal platform for the development of NGs. A variety of effective PEI‐based NGs have been designed and much effort has been devoted to study the relationship between the structure and function of the NGs. In particular, PEI‐based NGs can be prepared either using PEI as the major NG component or using PEI as a crosslinker. This review reports the recent progresses in the design of PEI‐based NGs for gene and drug delivery and for bioimaging applications with a target focus to tackle the diagnosis and therapy of cancer.     

Facile Synthesis of Mg2+‐Doped Carbon Dots as Novel Biomaterial Inducing Cell Osteoblastic Differentiation

Carbon dots (CDs), as an emerging fluorescent nanomaterial with low toxicity, has been widely applied in various bio‐related fields. However, investigations on their capabilities in guiding osteogenic differentiation are rarely seen, which has great significance in osteoporosis therapy and bone regeneration. Herein, for the first time, a new kind of Mg²⁺‐doped CDs is facilely synthesized through a one‐step hydrothermal method from metal gluconate salts. The CDs can serve as nanocarrier of Mg²⁺ ions entering into cells, and the bioessential metal ions subsequently stimulate osteoblastic differentiation by improving alkaline phosphatase (ALP) activity and upregulation related mRNA expression. Noteworthy, the raw material has almost negligible performance on osteoblastic differentiation compared to Mg‐CDs, which is due to the ultrasmall sizes of CDs and the efficient uptake by cells. Moreover, benefitting from the fluorescence properties, Mg‐CDs can also be applied as cell labeling agents. This work proposes a new strategy to synthesize multifunctional metal ion‐doped CDs, which might had great potential in serving as promising nanodrugs for bone loss therapy.     

Bio-safety assessment of carbon quantum dots,N-doped and folic acid modified carbon quantum dots: A systemic comparison

The carbon quantum dots(CQDs) and their functionalized materials are promising in biomedical field because of their unique properties;meanwhile,a growing concern has been raised about the potential toxicity of these modified materials in biosystem.In this study,we synthesized original CQDs and two common functionalized CQDs including N-doped CQDs(NCQDs) and folic acid-modified CQDs(FACQDs),and compared the toxicity and biocompatibility with each other in vitro and in vivo.L929,C6 and normal cell MDCK were selected to detect the adverse reaction of these materials in vitro.No acute toxicity or obvious changes were noted from in vitro cytotoxicity studies with the dose of these CQD materials increasing to a high concentration at 1 mg/mL.Among these materials,the FA-CQDs show a much lower toxicity.Moreover,in vivo toxicity studies were performed on the nude mice for 15 days.The experimental animals in 10 or 15 mg/kg groups were similar with animals treated by phosphate buffer solution(PBS) after 15 days.The results of the multifa rious biochemical parameters also suggest that the functionalized products of CQDs do not influence the biological indicators at feasible concentration.Our findings in vitro and in vivo through toxicity tests demonstrate that CQDs and their modified materials are safe for future biological applications.     

Overview of Syntheses and Molecular-Design Strategies for Tetrazine-Based Fluorogenic Probes

Various bioorthogonal chemistries have been used for fluorescent imaging owing to the advantageous reactions they employ. Recent advances in bioorthogonal chemistry have revolutionized labeling strategies for fluorescence imaging, with inverse electron demand Diels–Alder (iEDDA) reactions in particular attracting recent attention owing to their fast kinetics and excellent specificity. One of the most interesting features of the iEDDA labeling strategy is that tetrazine-functionalized dyes are known to act as fluorogenic probes. In this review, we will focus on the synthesis, molecular-design strategies, and bioimaging applications of tetrazine-functionalized fluorogenic probes. Traditional Pinner reaction and “Pinner-like” reactions for tetrazine synthesis are discussed here, as well as metal-catalyzed C–C bond formations with convenient tetrazine intermediates and the fabrication of tetrazine-conjugated fluorophores. In addition, four different quenching mechanisms for tetrazine-modified fluorophores are presented.     

Conjugated polymer nanoparticles with aggregation induced emission characteristics for intracellular Fe3+ sensing

In this article, a novel zwitterionic conjugated polyelectrolyte containing tetraphenylethene unit was synthesized via Pd‐catalyzed Sonogashira reaction. The resulting polymer (P2), which exhibited typical aggregation‐induced emission (AIE) properties, was weakly fluorescent in dilute DMSO solution and showed bright fluorescence emissions when aggregated in DMSO/water mixtures or fabricated into conjugated polymer nanoparticles (CPNs). The nanoparticles from P2 could be prepared by reprecipitation method with an average diameter around 23 nm. Notably, the cell‐staining efficiencies of lipid‐P2 nanoparticles could be enhanced with lipid encapsulation and these nanoparticles were endocytosed via caveolae‐mediated and clathrin‐mediated endocytosis pathways. Furthermore, the lipid‐P2 nanoparticles with low cytotoxicity, high photostability and efficient cell staining ability could be employed for in vitro detection of Fe³⁺ ions in A549 cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1686–1693     

Carboranes as a Tool to Tune Phosphorescence

Phosphorescent transition‐metal complexes (PTMCs) have attracted great interest because of their excellent properties which may lead to promising applications in optoelectronics. In recent years, carboranes have been demonstrated to be a novel and effective tool to tune phosphorescence of PTMCs. This Concept article deals with the advances of carborane‐functionalized PTMCs for potential optical applications. The discussions are focused on the design strategies and synthetic procedures leading to carborane‐functionalized PTMCs, the influence of carboranes on the optical properties of PTMCs, and the promising optical applications of this interesting class of phosphorescent materials.     

A New Fluorescence Turn-On Probe for Aluminum(III) with High Selectivity and Sensitivity,and its Application to Bioimaging

The development of novel selective probes with high sensitivity for the detection of Al³⁺ is widely considered an important research goal due to the importance of such probes in medicine, living systems and the environment. Here, we describe a new fluorescent probe, N′-(4-diethylamino-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (1), for Al³⁺. Probe 1 was evaluated in a solution of acetonitrile/water (1:1 v/v). Compared with previously reported probes for Al³⁺, probe 1 can be synthesized easily and in high yield. A Job plot confirmed that probe 1 is able to complex Al³⁺ in a 1:1 ratio, and the binding constant was determined to be 4.25×10⁸ m⁻¹. Moreover, the detection limit was as low as 6.7×10⁻⁹ m, suggesting that probe 1 has a high sensitivity. Common coexistent metal ions, such as K⁺, Co²⁺, Ca²⁺, Ba²⁺, Ni²⁺, Pb²⁺, Hg²⁺, Ce²⁺, Zn²⁺, Cd²⁺, Fe³⁺, showed little or no interference in the detection of Al³⁺ in solution, demonstrating the high selectivity of the probe. Finally, the ability of probe 1 to act as a fluorescent probe for Al³⁺ in living systems was evaluated in Gram-negative bacteria, Escherichia coli, and confocal laser scanning microscopy confirmed its utility. The results of this study suggest that 1 has appropriate properties to be developed for application as a fluorescent probe of Al³⁺ for use in biological studies.