Unexpected higher corrosion in the gas phase region of metals caused by calcium and magnesium ions compared to sodium ions.

In the marine environment, Na+ ions have been the focus of attention owing to their high content, which is one of the important factors causing marine corrosion. With reference to the content of macro ions in seawater, circular iron samples were semi-immersed in 0.04 M MgCl2 and 0.6 M NaCl solutions containing different proportions of ethanol. Unexpectedly, we observed more severe corrosion effects in the gas phase region and at the gas-liquid interface of metal samples semi-immersed in the MgCl2 solution. Although the concentration of the MgCl2 solution was only 1/15 of that of the NaCl solution, the iron corrosion induced by MgCl2 was significantly more severe than that caused by NaCl when the ethanol content was increased. Mg2+ ions outperform Na+ ions in metal gas phase corrosion. Especially in the oxygen content of the gas phase corrosion product, MgCl2 caused an increase by up to 52.7%, while NaCl only resulted in a 10.3% increase. Ethanol is normally regarded as a corrosion inhibitor and exists in the liquid phase. Interestingly, in the gas phase and at the gas-liquid interface, ethanol aggravated rather than reducing iron corrosion, particularly in the presence of Mg2+ ions. In addition, we observed that Ca2+ ions produced more severe corrosion effects.

Unexpected iron corrosion by excess sodium in two-dimensional Na-Cl crystals of abnormal stoichiometries at ambient conditions.

At ambient conditions, we found salt crystals formed from unsaturated solutions on an iron surface; these salt crystals had abnormal stoichiometries (i.e. Na2Cl and Na3Cl), and these abnormal crystals with Cl:Na of 1/2-1/3 could enhance iron corrosion. Interestingly, we found that the ratio of abnormal crystals, Na2Cl or Na3Cl, with ordinary NaCl was relative to the initial NaCl concentration of the solution. Theoretical calculations suggest that this abnormal crystallisation behaviour is attributed to the different adsorption energy curves between Cl--iron and Na+-iron, which not only promotes Na+ and Cl- adsorbing on the metallic surface to crystallise at unsaturated concentration but also induces the formation of abnormal stoichiometries of Na-Cl crystals for different kinetic adsorptionprocess. These abnormal crystals could also be observed on other metallic surfaces, such as copper. Our findings will help elucidate some fundamental physical and chemical views, including metal corrosion, crystallisation and electrochemical reactions.

Heterojunction structured BiOCl-Bi2S3 nanosheets as mitochondria-targeted near-infrared photothermal and photodynamic therapy agent.

Mitochondria-targeted phototherapy, especially combined photothermal therapy (PTT) and photodynamic therapy (PDT), has been regarded as an attractive strategy for the treatment of tumor. In this study, a facile approach to prepare two-dimensional (2D) BiOCl-Bi2S3 nanostructures was developed, where Bi2S3 quantum dots were doped in/on the ultrathin BiOCl nanosheets, forming a p-n heterojunction. The BiOCl-Bi2S3 shows favorable photothermal conversion efficiency (32%) and synergistically reactive oxygen species (ROS) generating capability under near-infrared (NIR) irradiation. Moreover, the conjugation of synthetic targeting ligand to the surface of BiOCl-Bi2S3 endows the heterojunction effective tumor targeting ability and selective mitochondrial accumulation. The combined cancer targeting ability and synergistic PTT/PDT permit enhanced cooperative phototherapeutic efficiency of the 2D heterojunction. This study provides an attractive way for designing new class of heterostructure materials for potential applications in subcellular-targeted phototherapy.

Progress in infrared spectroscopy as an efficient tool for predicting protein secondary structure.

Infrared (IR) spectroscopy is a highly sensitive technique that provides complete information on chemical compositions. The IR spectra of proteins or peptides give rise to nine characteristic IR absorption bands. The amide I bands are the most prominent and sensitive vibrational bands and widely used to predict protein secondary structures. The interference of H2O absorbance is the greatest challenge for IR protein secondary structure prediction. Much effort has been made to reduce/eliminate the interference of H2O, simplify operation steps, and increase prediction accuracy. Progress in sampling and equipment has rendered the Fourier transform infrared (FTIR) technique suitable for determining the protein secondary structure in broader concentration ranges, greatly simplifying the operating steps. This review highlights the recent progress in sample preparation, data analysis, and equipment development of FTIR in A/T mode, with a focus on recent applications of FTIR spectroscopy in the prediction of protein secondary structure. This review also provides a brief introduction of the progress in ATR-FTIR for predicting protein secondary structure and discusses some combined IR methods, such as AFM-based IR spectroscopy, that are used to analyze protein structural dynamics and protein aggregation.

Evolution of the protein corona affects macrophage polarization.

When nanoparticles (NPs) come into contact with bioenvironments, a protein corona forms on the NP surface. Previous reports showed that the constituents of the corona change with time. However, how different protein corona compositions influence cells, especially immune cells, has received less attention. Macrophages are important immune cells that can be polarized into a pro-inflammatory (M1) or anti-inflammatory (M2) phenotype. In this study, AuNPs were incubated with human plasma for different periods to obtain time-related AuNP-coronas, and the influences of time-related AuNP-coronas on macrophage polarization were investigated. The macrophage morphology, biomarkers, cytokine secretion studies show that the pristine AuNPs and 4 h-AuNP-corona induced macrophage cells into M2 phenotype, while the co-incubation of 12 h-AuNP-corona and macrophage cells result in M1 phenotype. Further proteomic analysis showed that the compositions of protein corona were changing constantly after AuNPs contacted with plasma. When the incubation time increased to 12 h, the immune proteins in protein corona were increased significantly, which play a key role in modulation of the different macrophages polarization. Our findings demonstrated that plasma incubation time is an important parameter that needs to be taken into account in the study of nano-immune interactions and safe use of NPs in biological systems. Moreover, our finding can be a new efficient strategy for activating inflammatory or anti-inflammatory in medical treatment.

CaCO3-Encapsulated Au Nanoparticles Modulate Macrophages toward M1-like Phenotype.

Macrophage cells are plastic and can be polarized into opposing phenotypes, pro-inflammatory (M1-like cells) or anti-inflammatory (M2-like cells). Reprograming of M2-like cells into M1 phenotype will contribute significantly to combatting cancer. Gold nanoparticles (AuNPs) are intensively studied in various fields for their distinctive photo-chemical properties. However, the immune response of AuNPs is still unclear. In this study, AuNPs and CaCO3-encapsulated Au nanoparticles (Au@CaCO3 NPs) were synthesized as stimuli for macrophage modulation. Co-incubation of AuNPs and macrophages leads to a dramatically elongated macrophage cell morphology. Moreover, increased expression of M2 biomarker and M2-inducing cytokines suggests that AuNPs induce macrophage polarization toward M2 phenotype. More interestingly, the co-incubation of Au@CaCO3 NPs and macrophage cells resulted in a round cellular morphology and induced the secretion of M1 biomarker and inflammatory cytokines. Our studies demonstrate that the strategy of CaCO3-encapsulated Au nanoparticles can be used in modulating the polarization of M1 macrophages. Our strategy provides an efficient method for activating inflammation in macrophages, which will be useful for the application of nanoparticles in cancer therapy.

Labeled-protein corona-coated Bi2S3 nanorods targeted to lysosomes for bioimaging and efficient photothermal cancer therapy.

One of the main diseases contributing to human death are malignant tumors. Phototherapy is a promising approach for cancer therapy, and functional nanoparticles with targeting ligands are commonly used to improve the therapeutic efficiency. However, recent studies have shown that nanoparticles in contact with a biological fluid can rapidly form a "protein corona" on their surface, which will remarkably decrease the targeting ability. Here, we describe the preparation of hybrid nanomaterials with Bi2S3 nanorods as the core, and fluorescein-isothiocyanate and folic acid-modified human serum albumin (HSA-FITC-FA) as the shell. By using fluorescent binding label (FITC) and imaging techniques, we discovered the image of the cell lysosomes, indicating that the photothermal therapy agent was predominantly targeted to and accumulated in lysosomes. Combined with photothermal therapy agent (Bi2S3 nanorods) and targeting ligand (FA), the obtained product shows enhanced photothermal therapy under near-infrared region laser irradiation. Additionally, SDS-PAGE shows that the modified HSA shell could remarkably reduce the reabsorption of protein corona from blood serum, minimized the adverse effect of protein corona on targetability. Taken together, the results indicate that our strategy has the potential for preparing efficient photothermal nanomaterials with image-guided subcellular organelle-targeting cancer cell ablation ability.

In situ generation of biocompatible amorphous calcium carbonate onto cell membrane to block membrane transport protein - A new strategy for cancer therapy via mimicking abnormal mineralization.

Herein, our aim is to develop a drug-free method without obvious side effects to treat cancer through biomineralization of biocompatible inorganic nanomaterials targeting onto cells' membrane to block transport proteins. We selected chondroitin sulfate as optimal target agent and linker to induce the in situ biomineralization of exogenous Ca2+ and CO32- at safe concentration to generate biocompatible calcium carbonate (CaCO3) nanostructures targeting onto cancer cells' membrane. The in vitro and in vivo assays indicated that the generated CaCO3 nanostructures could significantly inhibit the proliferation of cancer cells. Mechanism studies demonstrated that the mineralized CaCO3 nanostructures could bind with 66 membrane proteins. Deeply research revealed that the CaCO3 nanostructures could mainly block transport proteins, e.g. sodium/potassium-transporting ATPase, leading to the collapse of the mitochondrial membrane potential and the increase of the lactate dehydrogenase release into medium, and finally modulated cell cycle and induced the apoptosis of cancer cells. Our results may introduce promising possibilities for efficient and specific cancer treatment by producing biocompatible nanomaterials to block transport proteins.

Obtaining information about protein secondary structures in aqueous solution using Fourier transform IR spectroscopy.

Fourier transform IR (FTIR) spectroscopy is a nondestructive technique for structural characterization of proteins and polypeptides. The IR spectral data of polymers are usually interpreted in terms of the vibrations of a structural repeat. The repeat units in proteins give rise to nine characteristic IR absorption bands (amides A, B and I-VII). Amide I bands (1,700-1,600 cm(-1)) are the most prominent and sensitive vibrational bands of the protein backbone, and they relate to protein secondary structural components. In this protocol, we have detailed the principles that underlie the determination of protein secondary structure by FTIR spectroscopy, as well as the basic steps involved in protein sample preparation, instrument operation, FTIR spectra collection and spectra analysis in order to estimate protein secondary-structural components in aqueous (both H2O and deuterium oxide (D2O)) solution using algorithms, such as second-derivative, deconvolution and curve fitting. Small amounts of high-purity (>95%) proteins at high concentrations (>3 mg ml(-1)) are needed in this protocol; typically, the procedure can be completed in 1-2 d.

Antineoplastic activities of protein-conjugated silver sulfide nano-crystals with different shapes.

In this paper, antineoplastic activities of protein-conjugated silver sulfide nano-crystals with different shapes were described in detail. Transmission electron microscope analysis demonstrated that stable and well-disperse protein-conjugated silver sulfide nano-particles, nano-rods, and nano-wires could be prepared by aqueous chemistry method. The Fourier transform infrared spectrograph analysis indicated the strong coordination between silver sulfide surfaces and -OH and -NH groups in bovine serum albumin. The antineoplastic activities of protein-conjugated silver sulfide nano-crystals were examined by cell viability analysis, optical and electron microscopy methods. The results showed that nano-particles, nano-rods and nano-wires could inhibit the proliferations of human hepatocellular carcinoma Bel-7402 cells and C6 glioma cells, and the activities were size-dependent.

Shape-controlled synthesis of protein-conjugated silver sulfide nanocrystals and study on the inhibition of tumor cell viability.

Stable protein-conjugated silver sulfide nanoparticles, nanorods and nanowires have been prepared by an aqueous chemistry method and the study results showed they had potential applications for tumor treatment.