Facile preparation of thermosensitive and water-soluble fluorescent polymer containing curcumin and its cell imaging

A novel thermosensitive and water-soluble fluorescent polymer PNIPAM-curcumin (P2) containing curcumin unit was synthesized through one-pot method. The chemical structure and optical properties of compounds and polymer were characterized and tested. As the results turned out that P2 displayed excellent water solubility, thermosensitivity and exhibited strong fluorescence emission band in water. Moreover, P2 was further investigated by MTT assay and live cell imaging with HeLa cells. P2 did not have cytotoxicity in concentration of 200?µg?·?mL^?1 within 48?h and the intracellular fluorescence intensity enhanced with the concentration of P2 varying from 0 to 500?µg?·?mL^?1. According to the experimental results, as a fluorescence probe, P2 synthesized does not only possess nice water solubility but also has the advantage of no cytotoxicity, and it can easily enter the cells, which indicates that it is a characteristic of high sensitivity and responsiveness. Therefore, P2 will have immense potential to be applied in biomedical fields.     

Folate-modified gold nanoclusters as near-infrared fluorescent probes for tumor imaging and therapy

Ultra-small gold nanoclusters (Au NCs) are highly promising materials for tumor imaging and therapy because of their low toxicity, intrinsic fluorescence, and the availability of multifunctional groups for covalent linkage of diverse bioactive molecules. Au NCs stabilized by bovine serum albumin (BSA) were prepared via an improved "green" synthetic routine. To ameliorate the selective affinity of Au NCs for high folate receptor (FR) expressing tumors, folic acid (FA) was immobilized on the surface of Au NCs. Subsequently, a near-infrared (NIR) fluorescent dye MPA was conjugated with Au-FA NCs for in vitro and in vivo fluorescence imaging. Similarly, Doxorubicin (DOX), a widely used clinical anticancer drug, was also conjugated to the folate-modified Au NCs to form a prodrug (Au-FA-DOX). Cellular and in vivo acute toxicity studies demonstrated the low toxicity of the Au-FA-MPA to normal cells and tissues. Additionally, in vitro and in vivo study of the dynamic behavior and targeting ability of Au-FA-MPA to different tumors validated the high selective affinity of Au-FA-MPA to FR positive tumors. With regard to the Au-FA-DOX, high anti-tumor activity was displayed by this pro-drug due to the FR mediated uptake. Herein, all of the results supported the potential of using ligand-modified Au NCs for tumor imaging and targeted therapy.     

双信号金纳米簇对三硝基甲苯的荧光分析

三硝基甲苯作为硝基芳香化合物的代表物,应用相当广泛。其对人体健康、生活环境均具有较大的危害,因此发展简单、便捷检测三硝基甲苯的分析方法非常有必要。利用环境友好的牛血清白蛋白和2-氨基嘌呤合成了双信号金纳米簇荧光探针,基于三硝基甲苯对金纳米簇荧光的淬灭作用,建立了一种检测三硝基甲苯的荧光分析新方法,检出限可达0.14μmol/L,该方法具有良好的灵敏度和选择性。     

Biomimetic one-pot synthesis of gold nanoclusters/nanoparticles for targeted tumor cellular dual-modality imaging

Biomimetic synthesis has become a promising green pathway to prepare nanomaterials. In this study, bovine serum albumin (BSA)-conjugated gold nanoclusters/nanoparticles were successfully synthesized in water at room temperature by a protein-directed, solution-phase, green synthetic method. The synthesized BSA-Au nanocomplexes have fluorescence emission (588 nm) of gold nanoclusters and surface plasmon resonance of gold nanoparticles. The BSA-Au nanocomplexes display non-cytotoxicity and excellent biocompatibility on MGC803 gastric cancer cells. After conjugation of folic acid molecules, the obtained BSA-Au nanocomplexes showed highly selective targeting for MGC803 cells and dual-modality dark-field and fluorescence imaging.     

金银纳米簇制备方法的研究进展

综述了金、银纳米簇新型的荧光纳米材料的制备方法的研究进展,比较了物理方法、化学方法和综合法,指出化学方法中的模板合成法与单分子层保护法能更有效地制备出优良性能的金、银纳米簇。     

Preparation of thermoresponsive fluorescent carbon dots for cellular imaging

Nowadays, carbon dots (CDs ) have aroused widespread interest due to their chemical stability, biocompatibility as well as low toxicity. Herein, polymerizable CD monomers were synthesized through amidation between hydrophobic CDs and methacryloyl chloride, which has emerged as a facile method for preparing various fluorescent CD monomers. The fluorescent polymerizable CDs were copolymerized with N‐ isopropylacrylamide (NIPAM ) to form thermoresponsive fluorescent nanoparticles. The poly(NIPAM ) (PNIPAM ) grafted hydrophobic CDs (CDs ‐g ‐PNIPAM ) have excellent dispersivity in water, rendering hydrophobic CDs with fluorescence properties in aqueous media. Moreover, CDs ‐g ‐PNIPAM nanocomposites show a remarkable thermoresponsive behavior, and the fluorescence intensity decreases progressively with increase in temperature. Cytotoxicity tests show that CDs ‐g ‐PNIPAM nanocomposites have great biocompatibility. When the CDs ‐g ‐PNIPAM nanocomposites were cultured with HaCaT cells at a concentration of 2000 µg mL ^?1, cell viability was maintained over 85%. Benefiting from the copolymerization of NIPAM , the excitation‐independent fluorescence of CDs ‐g ‐PNIPAM nanocomposites can be used for cellular labeling and show long‐term biostability in a cellular environment. © 2016 Society of Chemical Industry     

Facile synthesis of red-emitting lysozyme-stabilized Ag nanoclusters

A facile approach was developed to prepare positively charged and red-emitting lysozyme-stabilized Ag nanoclusters (Lys-AgNCs) using NaBH(4) as a reducing agent at room temperature. The Lys-AgNCs can be applied in the highly selective detection of Hg(2+).     

Local structure of fluorescent platinum nanoclusters

Fluorescent nanoclusters synthesized from a variety of noble metals have recently been reported in the scientific literature. Various characterization methods have been employed in their study, but uncertainty still remains regarding the local structure of such materials. Herein we present the results of employing X-ray absorption spectroscopy to probe the local structure and electronic properties of platinum nanoclusters reduced and stabilized using N,N-dimethylformamide. Most notable amongst these results is an apparent lack of metallic bonding in the samples studied; in light of these findings, it is proposed that a non-metallic platinum nanocluster is instead responsible for the observed fluorescence behaviour.     

First-principles investigation of ag-doped gold nanoclusters

Gold nanoclusters have the tunable optical absorption property, and are promising for cancer cell imaging, photothermal therapy and radiotherapy. First-principle is a very powerful tool for design of novel materials. In the present work, structural properties, band gap engineering and tunable optical properties of Ag-doped gold clusters have been calculated using density functional theory. The electronic structure of a stable Au(20) cluster can be modulated by incorporating Ag, and the HOMO-LUMO gap of Au(20-) (n)Ag(n) clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO. Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases. These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.     

Gd(III) functionalized gold nanorods for multimodal imaging applications

We demonstrate a novel noncovalent method for producing Gd(III)-functionalized gold nanorods as multimodal contrast agents for MRI and CT imaging. The ligand is connected to the surface of the gold nanorods by a noncovalent bond making the Gd(III) ions directly accessible to water molecules, and resulting in a longitudinal relaxivity as high as 21.3 mM(-1) s(-1). In addition, compared with spherical gold nanoparticles, gold nanorods have more binding sites for Gd(III) ions due to their large surface-to-volume ratio. Benefiting from the advantages of the new type of carry material and the novel fabrication approach, the multimodal imaging probes exhibit a high longitudinal relaxivity r(1) on the order of 1.1 × 10(7) mM(-1) s(-1) on a per-particle basis, which is 24 times higher than that of Gd(III)-ion-functionalized spherical gold nanoparticles. Furthermore, CT imaging shows that such nanoprobes could induce an efficient contrast enhancement when the gold concentration is at least equal to 1.31 mg ml(-1). These results demonstrate that the as-prepared Gd functionalized gold nanorods could provide a new and versatile platform for the development of multimodal imaging probes.     

Facile preparation of size-controlled gold nanoparticles using versatile and end-functionalized thioether polymer ligands

At present, thiol ligands are generally used whenever the classical Brust-Schiffrin two-phase method is employed to prepare metal nanoparticles. In general, the previous research was mainly focused on utilizing small molecular thiol compounds or thiol polymers as the stabilizers in organic phase to obtain small sized and uniform gold nanoparticles (Au NPs). Such preparations are usually associated with the problems of ligand exchange on the nanoparticle's surface due to strong Au-thiol interaction. Herein, we report an approach to produce fairly uniform Au NPs with diameters about 2-6 nm using thioether end-functional polymer ligands (DDT-PVAc and PTMP-PVAc) as the capping agents. These nanoparticles are thoroughly characterized using DLS, TEM, UV-Vis spectroscopy and other complementary techniques. The results indicate that multidentate thioether polymeric ligands (PTMP-PVAc) lead to formation of smaller but special 'multimer' morphology in organic phase; whereas fairly uniform nanoparticles are produced using monodentate thioether functionalized ligands (DDT-PVAc). Further modification of such polymer ligands to introduce the hydrophilic functionalities realizes the phase transfer of Au NPs from organic to aqueous media.     

Facile enzymatic preparation of fluorescent conjugated polymers of phenols and their application in sensing

The recognized drawback of utilizing metal catalysts for the synthesis of fluorescent conjugated polymers (CP) is the requirement for extensive purification to ensure complete removal of residual catalyst that would otherwise quench the fluorescence. In addition, typical synthesis of fluorescent CP involves multiple steps, monomers and solvents with varying levels of toxicity. This work demonstrates the possibility of utilizing oxidoreductase enzymes as the catalyst, for the one step polymerization of naturally occurring phenols to yield fluorescent conjugated polyphenols. The metal in the active site of the enzyme remains chelated during the synthesis allowing the polymers to be fluorescent as synthesized without the need for extensive purification. Three natural phenols, 4‐hydroxyphenylacetic acid, hydroxytyrosol, and chlorogenic acid were polymerized using Horseradish peroxidase as the biocatalyst. Spectroscopic techniques, UV–vis, Fourier transform infrared Spectroscopy–Attenuated Total Reflectance, and fluorescence, are used to characterize chemical structure and photoluminescence of these polymers. The polyphenols exhibit fluorescence with significant stokes shift in the range 30–100 nm rendering them useful in fluorescence quenching‐based sensors. Preliminary studies on use of these polymers, in the detection of nitro‐aromatic compounds in solution through using fluorescence‐quenching are also presented. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46496.     

Modeling cyclic voltammetry of electrode-immobilized gold nanoclusters

The interaction that occurs between a supporting electrolyte and electrode-immobilized gold nanoclusters (GNCs) in voltammetric experiments is modeled with equivalent circuits. Several new versions of the Randles circuit are developed that are shown to better represent the electrical behavior of the clusters including their rectification effect. When combined with the orthodox theory of Coulomb blockade, these circuits also allow the quantized charging seen in cluster CVs to be simulated. From such modeling, the ratio of the ionic charging time to the electronic charging time is identified as the crucial factor determining whether or not quantized charging is observed.     

The halogen analogs of thiolated gold nanoclusters

Is it possible to replace all the thiolates in a thiolated gold nanocluster with halogens while still maintaining the geometry and the electronic structure? In this work, we show from density functional theory that such halogen analogs of thiolated gold nanoclusters are highly likely. Using Au(25)X(18)(-) as an example, where X = F, Cl, Br, or I replaces -SR, we find that Au(25)Cl(18)(-) demonstrates a high similarity to Au(25)(SR)(18)(-) by showing Au-Cl distances, Cl-Au-Cl angles, band gap, and frontier orbitals similar to those in Au(25)(SR)(18)(-). DFT-based global minimization also indicates the energetic preference of staple formation for the Au(25)Cl(18)(-) cluster. The similarity between Au(m)(SR)(n) and Au(m)X(n) could be exploited to make viable Au(m)X(n) clusters and to predict structures for Au(m)(SR)(n).     

Microwave-assisted rapid synthesis of luminescent gold nanoclusters for sensing Hg2+ in living cells using fluorescence imaging

A microwave-assisted strategy for synthesizing dihydrolipoic acid (DHLA) capped fluorescent gold nanoclusters (AuNCs) has been developed. Irradiation with microwaves during synthesis enhanced the fluorescence quantum yield (QY) of AuNCs by about five-fold and shortened the reaction time from hours to several minutes. The as-synthesized DHLA-AuNCs possessed bright near-infrared fluorescence (QY: 2.9%), ultrasmall hydrodynamic diameter (3.3 nm), good colloidal stability over the physiologically relevant pH range of 5-10 as well as low cytotoxicity toward HeLa cells. Moreover, these DHLA-AuNCs were capable of sensing Hg(2+) through the specific interaction between Hg(2+) and Au(+) on the surface of AuNCs; the limit of detection (LOD) was 0.5 nM. A potential application in imaging intracellular Hg(2+) in HeLa cells was demonstrated by using spinning disc confocal microscopy.     

Biocompatible polydopamine fluorescent organic nanoparticles: facile preparation and cell imaging

Biocompatible fluorescent organic nanoparticles with tunable photoluminescence were prepared via the one-pot oxidation of polydopamine and subsequently utilized for cell imaging.     

Facile preparation of gold nanoparticle with diarylethene polymers by disodium malate and its photoreversible optical properties

We have developed a synthetic procedure of gold nanoparticle covered with polystyrene (Au-poly(St)) using organic acid salts, followed by a ligand exchange reaction. First, various chain lengths of polystyrenes (poly(St)s) bearing thiol-end group were used as the covering agent of gold nanoparticle prepared by reduction using trisodium citrate. The resulting nanoparticles with ca. 13 nm diameter were dispersed in toluene when the molecular weight of the ligand poly(St) is larger than 1200. Larger sized Au-poly(St) could be obtained using disodium malate instead of the citrate. The colloidal gold nanoparticle with ca. 40 nm diameter was easily prepared only by changing the reducing agent. Finally, we have demonstrated to prepare larger sized gold nanoparticle covered with a photochromic diarylethene polymer (Au-poly(DE)) that shows large change in local surface plasmon resonance absorption according to the photochromic reaction even in a solution.     

The preparation of polyaniline/gold nanocomposites by self-assembly and their electrochemical applications

Polyaniline/gold nanoparticles (PANI/AuNPs) nanocomposites were prepared using a simple self-assembly procedure. Polyvinyl pyrrolidone (PVP) was used as a stabilizing ligand of AuNPs and was shown to prevent the aggregation of AuNPs and to improve the affinity of AuNPs to PANI. By varying the ratio of PANI to AuNPs, the amount of loaded AuNPs was effectively controlled. UV–vis spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and electrochemical methods were used to characterize the nanocomposites. The nanocomposites showed electroactivity in neutral solution, making them promising candidates for various bioanalytical applications. A sensor constructed using PANI/AuNPs nanocomposites showed 6-fold higher electrocatalytic activity toward the oxidation of ascorbic acid than that composed of a pure PANI-modified electrode.     

Facile synthesis of fluorescent porous zinc sulfide nanospheres and their application for potential drug delivery and live cell imaging

Fabrication of intrinsically fluorescent porous nanocarriers that are simultaneously stable in aqueous solutions and photostable is critical for their application in drug delivery and optical imaging but remains a challenge. In this study, fluorescent porous zinc sulfide nanospheres were synthesized by a facile gum arabic-assisted hydrothermal procedure. The morphology, composition and properties of the nanospheres have been characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, N(2) adsorption-desorption analysis, thermal gravimetric analysis, fourier transform infrared spectrograph, optical measurement, dynamic light scattering, and cytotoxicity assay. They exhibit larger surface area, excellent colloidal stability, photostable fluorescent signals, and good biocompatibility, which makes them promising hosts for drug delivery and cellular imaging. The fluorescent dye safranine-T was employed as a drug model and loaded into the porous nanospheres, which were delivered to human cervical cancer HeLa cells in vitro for live cell imaging.     

A sensitive and selective near-infrared fluorescent probe for mercuric ions and its biological imaging applications

A new mercury(II) near-infrared region fluorescent probe 3,9-dithia-6-monoazaundecane-tricarbocyanine has been designed and synthesized. It consists of two functional moieties: the tricarbocyanine performs as the near-infrared region fluorophore, and the 3,9-dithia-6-monoazaundecane acts as the selected binding site for metal ions. The near-IR excitation and emission profiles of the probe can minimize cell and tissue damage and avoid native fluorescence from natural cellular species. It exhibits fluorescence increase upon the binding of the Hg(2+) based on the inhibition of the photoinduced electron transfer quenching mechanism. Excellent sensitivity and selectivity for mercuric ions are observed with this probe. The value of the system is demonstrated by its use in monitoring the real-time uptake of Hg(2+) within HepG2 cells and five day old zebrafish. The synthesis and remarkable properties of it help to extend the development of metal ions fluorescent probes for biological applications.