The endocytosis of nano-Pt into non-small cell lung cancer H1299 cells and intravital therapeutic effect in vivo

Lung cancer remains the most common fatal malignant disease, and the 5-year survival rate of patients with metastasis is merely 6%. In this research, the platinum nanocluster (short for nano-Pt) was used for optical imaging without the help of other fluorescent probes and possess targeted antitumor activity as well as low systemic toxicity. The endocytic pathway and distribution of nano-Pt in non-small cell lung cancer NSCLC H1299 cells was explored by the means of quantitative and qualitative tests. Furthermore, the targeting capability and antitumor efficiency of nano-Pt was detected by intravital imaging experiment and antitumor experiment. The research implies that nano-Pt entered H1299 cells dominatingly through macropinocytosis and clathrin-dependent endocytosis pathway, and has significant antitumor efficiency, targeting properties and reliable safety for mouse tumor, indicating this nano-Pt has great potential for clinical diagnosis and therapy of NSCLC H1299 cells.

Surfactant-free synthesis of fluorescent platinum nanoclusters using HEPES buffer for hypochlorous acid sensing and imaging

A surfactant-free synthesis of noble-metal nanoclusters (NMNCs) with specific function has recently remained more attractive and superior in bio-applications. Herein, by employing the weak reducibility of non-toxic HEPES, we prepared novel water-soluble fluorescent HEPES@Pt NCs by a simple surfactant-free synthesis strategy for hypochlorous acid (HClO) sensing. The as-prepared Pt NCs featured ultra-small size (∼2 nm), bright blue fluorescence, high stability and biocompatibility, and the fluorescence of the Pt NC nanoprobe can be specifically quenched with hypochlorous acid by a static quenching process. Moreover, the surfactant-free Pt NC probe displays fascinating performances for HClO sensing, including fast response to HClO, high stability and specificity, and is further applied for imaging the fluctuations of the HClO concentration in living cells with satisfactory results for the first time. Thereby, we anticipate that it is a reliable and attractive approach to develop versatile NMNCs through the surfactant-free synthesis for further applications in biological research.

Synthesis of water-soluble, ultrabright Cu nanoclusters with core-shell structure via facile reduction approach for determination of 4-nitrophenol

In this work, we reported a facile reduction approach for fabrication of water-soluble and ultrabright Cu nanoclusters with core-shell structure. A certain amount of reducing agent as NaBH₄was introduced into the polyethyleneimine-stabilized Cu nanoclusters (CuNCs@PEI) system, which exhibited 4-fold fluorescence enhancement along with a blue shift of the emission peak. The variations of morphology, valence states and functional groups demonstrated that a Cu shell was formed surround CuNCs (defined as CuNCs-Cu@PEI), attributable to metal complex (PEI-Cu⁺and PEI-Cu²⁺) reduction. The effect of core-shell morphology on luminous and electron relaxation mechanism of CuNCs-Cu@PEI was investigated via temperature-dependent steady and time-resolved fluorescence measurements. The CuNCs-Cu@PEI with a high fluorescence quantum yields of 22.59% were able to homogeneously disperse in aqueous phase, indicating their potential applications in biological labeling, sensing and invivoimaging. Finally, the CuNCs-Cu@PEI was employed as a fluorescence probe to determine 4-nitrophenol, of which the detection limit was much lower than initial CuNCs@PEI.

Fluorescent platinum nanoclusters as correlative light electron microscopy probes

Correlative Imaging (CI) visualizes a single sample/region of interest with two or more imaging modalities. The technique seeks to elucidate information that may not be discernible by using either of the constituent techniques in isolation. Correlative Light Electron Microscopy (CLEM) can be employed to streamline workflows, i.e., using fluorescent signals in the light microscope (LM) to inform the user of regions which should be imaged with electron microscopy (EM). The efficacy of correlative techniques requires high spatial resolution of signals from both imaging modalities. Ideally, a single point should originate from both the fluorescence and electron density. However, many of the ubiquitously used probes have a significant distance between their fluorescence and electron dense portions. Furthermore, electron dense metal nanoparticles used for EM visualization readily quench any proximal adjacent fluorophores. Therefore, accurate registration of both signals becomes difficult. Here we describe fluorescent nanoclusters in the context of a CLEM probe as they are composed of several atoms of a noble metal, in this case platinum, providing electron density. In addition, their structure confers them with fluorescence via a mechanism analogous to quantum dots. The electron dense core gives rise to the fluorescence which enables highly accurate signal registration between epifluorescence and electron imaging modalities. We provide a protocol for the synthesis of the nanoclusters with some additional techniques for their characterization and finally show how they can be used in a CLEM set up.

Red-Fluorescent Pt Nanoclusters for Detecting and Imaging HER2 in Breast Cancer Cells

Overexpression of human epidermal growth factor receptor 2 (HER2) is associated with more frequent cancer recurrence and metastasis. Sensitive sensing of HER2 in living breast cancer cells is crucial in the early stages of cancer and to further understand its role in cells. Biomedical imaging has become an indispensable tool in the fields of early cancer diagnosis and therapy. In this study, we designed and synthesized platinum (Pt) nanocluster bionanoprobes with red emission (Ex/Em = 535/630 nm) for fluorescence imaging of HER2. Our Pt nanoclusters, which were synthesized using polyamidoamine (PAMAM) dendrimer and preequilibration, exhibited approximately 1% quantum yield and possessed low cytotoxicity, ultrasmall size, and excellent photostability. Furthermore, combined with ProteinA as an adapter protein, we developed Pt bionanoprobes with minimal nonspecific binding and utilized them as fluorescent probes for highly sensitive optical imaging of HER2 at the cellular level. More importantly, molecular probes with long-wavelength emission have allowed visualization of deep anatomical features because of enhanced tissue penetration and a decrease in background noise from tissue scattering. Our Pt nanoclusters are promising fluorescent probes for biomedical applications.

Layer-by-layer assembly of metal-organic framework nanosheets with polymer

Metal-organic framework (MOF) nanosheets are attracting more and more attention due to their tunable porous structure and two-dimensional shape. Adding MOF nanosheets into polymers can lead to improved properties, but the level of enhancement is usually thwarted by the difficulties in exfoliating and aligning these nanosheets within the polymer matrix. In order to establish a strategy for making polymer/MOF nanosheets composites with improved exfoliation and alignment, we combined MOF nanosheets and polymer using layer-by-layer (LbL) assembly for the first time. MOF nanosheets (ZIF67-L, leaf-like zeolitic imidazolate framework nanosheets) used in this study were functionalized with positively charged polyethylenimine, which could replace the original surface ligands and impart a positive charge on the nanosheet surface. These positively charged MOF nanosheets were then combined with negatively charged poly(acrylic acid) through ionic-bonding-assisted LbL assembly, generating a polymer composite with fully exfoliated and highly aligned MOF nanosheets.

Multifunctional fluorescent iron quantum clusters for non-invasive radiofrequency ablationof cancer cells

This work reports the potential of iron quantum clusters (FeQCs) as a hyperthermia agent for cancer, by testing its in-vitro response to shortwave (MHz range), radiofrequency (RF) waves non-invasively. Stable, fluorescent FeQCs of size ∼1 nm prepared by facile aqueous chemistry from endogenous protein haemoglobin were found to give a high thermal response, with a ΔT ∼50 °C at concentrationsas low as165 μg/mL. The as-prepared nanoclusters purified by lyophilization as well as dialysis showed a concentration, power and time-dependent RF response, with the lyophilized FeQCs exhibiting pronounced heating effects. FeQCs were found to be cytocompatible to NIH-3T3 fibroblast and 4T1 cancer cells treated at concentrations upto 1000 μg/mL for 24 h. Upon incubation with FeQCs and exposure to RF waves, significant cancer cell death was observed which proves its therapeutic ability. The fluorescent ability of the clusters could additionally be utilized for imaging cancer cells upon excitation at ∼450 nm. Further, to demonstrate the feasibility of imparting additional functionality such as drug/biomolecule/dye loading to FeQCs, they were self assembled with cationic polymers to form nanoparticles. Self assembly did not alter the RF heating potential of FeQCs and additionally enhanced its fluorescence. The multifunctional fluorescent FeQCs therefore show good promise as a novel therapeutic agent for RF hyperthermia and drug loading.

Fluorescence enhancement of gold nanoclustersviaZn doping for biomedical applications

Gold nanoclusters (NCs) have been widely used in bioimaging and cancer therapy due to their unique electronic structures and tunable luminescence. However, their weak fluorescence prevents potential biomedical application, and thus it is necessary to develop an effective route to enhance the fluorescence of gold NCs. In this work, we report the fluorescence enhancement of ultrasmall GSH-protected Au NCs by Zn atom doping. The fluorescence signal of Zn-doped Au NCs shows approximately 5-fold enhancement compared to pure Au NCs. Density functional theory (DFT) calculation shows that Zn doping can enhance the electronic states of the highest occupied molecular orbital (HOMO), leading to enhancement of visible optical transitions. In vitro experiments show that AuZn alloy NCs can enhance the cancer radiotherapy via producing reactive oxygen species (ROS) and don't cause significant cytotoxicity. In vivo imaging indicates AuZn alloy NCs have significant passive targeting capability with high tumor uptake. Moreover, nearly 80% of GSH-protected AuZn alloy NCs can be rapidly eliminated via urine excretion.

Fluorescence enhancement of gold nanoclusters via Zn doping.

Synthesis of Novel Hyperbranched Polybenzo-Bisthiazole Amide with Donor⁻Acceptor (D-A) Architecture, High Fluorescent Quantum Yield and Large Stokes Shift

Two novel highly fluorescent hyperbranched polybenzobisthiazole amides with a donor⁻acceptor architecture and large Stokes shift were rationally designed and synthesized. The chemical structures of the prepared hyperbranched polymers were characterized using Fourier Transform Infrared Spectroscopy (FTIR) analysis, Hydrogen Nuclear Magnetic Resonance (¹H-NMR) analysis, and Gel Permeation Chromatography (GPC) analysis. These two polymers were soluble in dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and their DMSO and DMF solutions emitted strong green light (517⁻537 nm) with high quantum yields (QYs) and large Stokes shifts. Their relative fluorescence QYs in the DMSO solution were calculated as 77.75% and 81.14% with the Stokes shifts of 137 nm (0.86 eV) and 149 nm (0.92 eV) for HP⁻COOH and HP⁻NH₂, respectively, using quinine sulfate as the standard. In the DMF solution, the QYs of HP⁻COOH and HP⁻NH₂ were calculated as 104.65% and 118.72%, with the Stokes shifts of 128 nm (0.79 eV) and 147 nm (0.87 eV), respectively. Their films mainly emitted strong blue light with the maximum emission wavelengths of 436 nm and 480 nm for HP⁻COOH and HP⁻NH₂, respectively. The Stokes shifts for HP⁻COOH and HP⁻NH₂ films were 131 nm (0.42 eV) and 179 nm (0.86 eV), respectively. They are promising candidates for luminescent solar concentrators and blue light emitting materials.

Hydrothermal synthesis of polyethylenimine-protected high luminescent Pt-nanoclusters and their application to the detection of nitroimidazoles

A novel one-step hydrothermal synthesis of highly fluorescent platinum nanoclusters protected by polyethylenimine (Pt-NCs@PEI) is described. The products are characterized well by UV-vis absorption, fluorescence spectra, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) imaging. The Pt-NCs@PEI possess high quantum yield at 28%, which is the relatively high one among the reported Pt-NCs; especially, the synthesis is in one-step and the reaction time is much shorter (<1 h) than the related methods. In addition, the Pt-NCs@PEI have large Stocks-shift (∼150 nm), high tolerability to the extreme pH and high ionic strengths, and excellent photo-stability under UV-vis irradiation, lay the foundation for the practical bio-applications. Finally, the obtained Pt-NCs@PEI are used to determine trace amount of metronidazole (MTZ) in buffer solution in showing a linear response over a concentration range of 0.25-300 μM and a low detection limit of 0.1 μM. Furthermore, the related investigation on response mechanism will be helpful to design and synthesize new metal nanoclusters as fluorescent probe to detect the trace amount of harmful medicine residuum as nitroimidazoles in human body.

Photochemically-assisted synthesis of non-toxic and biocompatible gold nanoparticles

This contribution describes the photochemically-assisted synthesis of aqueous colloidal suspensions of non-toxic and biocompatible spherical gold nanoparticles stabilized by branched polyethylenimine, or else Au-np-PEI. The method consists on 30min of photoexcitation (254nm, 16W) at room temperature of an aqueous diluted solution of chloroauric acid (HAuCl₄) containing PEI. While the UV irradiation forms the [Au⁽³⁺⁾Cl₄^-]* excited species that succesively transforms into zero valent Au, PEI controls the nucleation step of nanoparticles formation. Varying the PEI to Au molar ratio permits one to tune the size of nanoparticles between 100nm to 8nm. The obtained colloidal suspensions display an intense plasmonic absorption band at 520-530nm and positive zeta potentials greater than +20mV. The cells viability for in vitro tests performed with human connective tissues and human breast adenocarcinoma (MCF-7) cell lines is over 80% and 90%, respectively, when they are incubated with Au-np-PEI formulations (25μgmL^-1). The present photochemically-assisted synthesis is advantageous because it is fast and does not require for either hazardous or cytotoxic reductant agents and additional purification procedures.