Biomimetic and Aggregation-Driven Crystallization Route for Room-Temperature Material Synthesis: Growth of β-Ga₂O₃ Nanoparticles on Peptide Assemblies as Nanoreactors

The room-temperature synthesis of β-Ga2O3 nanocrystal was examined by coupling two biomimetic crystallization techniques, enzymatic peptide nanoassembly templating and aggregation-driven crystallization. The catalytic template of peptide assembly nucleated and mineralized primary β-Ga2O3 crystals and then fused them to grow single-crystalline and monodisperse nanoparticles in the cavity of the peptide assembly at room temperature. In this work, the peptide assembly was exploited as a nanoreactor with an enzymatic functionality catalyzing the hydrolysis of gallium precursors. In addition, the characteristic ring structure of peptide assembly is expected to provide an efficient dehydration pathway and crystallization control over the surface tension, which are advantageous for β-Ga2O3 crystal growth. This multifunctional peptide assembly could be applied for syntheses of a variety of nanomaterials that are kinetically difficult to grow at room temperature

An Efficient Strategy for Constructing Fluorescent Nanoprobes for Prolonged and Accurate Tumor Imaging

Activatable near-infrared (NIR) fluorescent probes possess advantages of high selectivity, sensitivity, and deep imaging depth, holding great potential in the early diagnosis and prognosis assessment of tumors. However, small-molecule fluorescent probes are largely limited due to the rapid diffusion and metabolic clearance of activated fluorophores in vivo. Herein, we propose an efficient and reproducible novel strategy to construct activatable fluorescent nanoprobes through bioorthogonal reactions and the strong gold–sulfur (Au–S) interactions to achieve an enhanced permeability and retention (EPR) effect, thereby achieving prolonged and high-contrast tumor imaging in vivo. To demonstrate the merits of this strategy, we prepared an activatable nanoprobe, hCy-ALP@AuNP, for imaging alkaline phosphatase (ALP) activity in vivo, whose nanoscale properties facilitate accumulation and long-term retention in tumor lesions. Tumor-overexpressed ALP significantly increased the fluorescence signal of hCy-ALP@AuNP in the NIR region. More importantly, compared with the small-molecule probe hCy-ALP-N3, the nanoprobe hCy-ALP@AuNP significantly improved the distribution and retention time in the tumor, thus improving the imaging window and accuracy. Therefore, this nanoprobe platform has great potential in the efficient construction of biomarker-responsive fluorescent nanoprobes to realize precise tumor diagnosis in vivo

Graphene Covalently Binding Aryl Groups: Conductivity Increases Rather than Decreases

Graphene functionalized via nitrophenyl groups covalently bonding to its basal plane is studied by Raman spectroscopy and electric transport measurements. The Raman spectra of functionalized graphene exhibit D mode and peaks derived from nitrophenyl groups, and the two fingerprints exhibit nearly the same distribution in the two-dimensional Raman maps over the whole graphene sheet. This result directly proves that the nitrophenyl groups bond to the graphene basal plane via σ-bonds. Electric transport measurements demonstrate that the modified graphene is significantly more conductive than intrinsic graphene. In the competition between charge transfer effect and scattering effect introduced by the nitrophenyl groups, the former one is dominant so that the conductivity of functionalized graphene is significantly enhanced as a result

Plasmon-Mediated Generation of Reactive Oxygen Species from Near-Infrared Light Excited Gold Nanocages for Photodynamic Therapy <i>in Vitro</i>

We have performed fundamental assays of gold nanocages (AuNCs) as intrinsic inorganic photosensitizers mediating generation of reactive oxygen species (ROS) by plasmon-enabled photochemistry under near-infrared (NIR) one/two-photon irradiation. We disclosed that NIR light excited hot electrons transform into either ROS or hyperthermia. Electron spin resonance spectroscopy was applied to demonstrate the production of three main radical species, namely, singlet oxygen (¹O₂), superoxide radical anion (O₂^–•), and hydroxyl radical (^•OH). The existence of hot electrons from irradiated AuNCs was confirmed by a well-designed photoelectrochemical experiment based on a three-electrode system. It could be speculated that surface plasmons excited in AuNCs first decay into hot electrons, and then the generated hot electrons sensitize oxygen to form ROS through energy and electron transfer modes. We also compared AuNCs’ ROS generation efficiency in different surface chemical environments under one/two-photon irradiation and verified that, compared with one-photon irradiation, two-photon irradiation could bring about much more ROS. Furthermore, <i>in vitro</i>, under two-photon irradiation, ROS can trigger mitochondrial depolarization and caspase protein up-regulation to initiate tumor cell apoptosis. Meanwhile, hyperthermia mainly induces tumor cell necrosis. Our findings suggest that plasmon-mediated ROS and hyperthermia can be facilely regulated for optimized anticancer phototherapy

The Big Red Shift of Photoluminescence of Mn Dopants in Strained CdS: A Case Study of Mn-Doped MnS−CdS Heteronanostructures

The Big Red Shift of Photoluminescence of Mn Dopants in Strained CdS: A Case Study of Mn-Doped MnS−CdS Heteronanostructure

Manganese Carbonyl-Loaded Hollow Mesoporous Silica Nanoparticles Coated with Neutrophil Membranes for Acute Kidney Injury Therapy

Acute kidney injury (AKI) has a very high incidence in hospitalized patients, but it lacks effective therapy clinically. Its pathogenesis is associated with capillary hypoperfusion around renal tubules, production of reactive oxygen free radicals (ROS), and infiltration of inflammatory cells. Endogenous carbon monoxide (CO) can protect cells or organs by vasodilation, anti-inflammation, and reducing oxidative stress injury. However, direct exogenous CO supplementation is difficult to control the exact dose, and excessive CO has obvious toxicity, which is difficult to be applied in clinical treatment. In this study, we constructed H2O2-responsive nanomedicine for CO therapy of AKI by loading manganese carbonyl (MnCO) onto the hollow mesoporous silicon nanoparticles (hMSN), which were coated with a neutrophil membrane with the insertion of phosphatidylserine (PS) into the membrane surface (MnCO@hMSN@NM-PS). MnCO@hMSN@NM-PS was located in the renal tubules of AKI through the biomimetic chemotaxis of the neutrophil membrane to the inflammation site and the active binding of PS to kidney injury molecule-1 (KIM-1), which was overexpressed in damaged renal tubular epithelial cells. MnCO@hMSN@NM-PS had a good protective effect on oxidative damage of renal tubular cells in vitro and glycerol-induced AKI in vivo. MnCO@hMSN@NM-PS offers hope for the treatment of AKI

Peptide–Au Cluster Probe: Precisely Detecting Epidermal Growth Factor Receptor of Three Tumor Cell Lines at a Single-Cell Level

Alterations in protein (e.g., biomarkers) expression levels have a significant correlation with tumor development and prognosis; therefore, it is desired to develop precise methods to differentiate the expression level of proteins in tumor cell lines, especially at the single-cell level. Here, we report a precise and versatile approach of quantifying the protein expression levels of three tumor cell lines in situ using a peptide–Au cluster probe. The probe (Au₅Peptide₃) consists of a peptide with a specific cell membrane epidermal growth factor receptor (EGFR) targeting ability and an Au cluster for both cell membrane EGFR imaging using confocal microscopy and cell membrane EGFR counting by laser ablation inductively coupled plasma mass spectrometry. Utilizing the peptide–Au cluster probe, we successfully quantify the EGFR expression levels of SMMC-7721, KB, and HeLa cells at a single-cell level and differentiate the EGFR expression levels among these cell lines. The peptide–Au cluster probe, with the ability to differentiate the protein expression level of different cell lines, shows exceptional promise for providing reliable predictive and prognostic information of tumors at a single-cell level

Serial Silver Clusters Biomineralized by One Peptide

The artificial peptide with amino acid sequence CCYRGRKKRRQRRR was used to biomineralize serial Ag clusters. Under different alkaline conditions, clusters with red and blue emission were biomineralized by the peptide, respectively. The matrix-assisted laser desorption/ionization time-of-flight mass spectra implied that the red-emitting cluster sample was composed of Ag28, while the blue-emitting cluster sample was composed of Ag5, Ag6, and Ag7. The UV–visible absorption and infrared spectra revealed that the peptide phenol moiety reduced Ag+ ions and that formed Ag clusters were captured by peptide thiol moieties. The phenol reduction potential was controlled by the alkalinity and played an important role in determining the Ag cluster size. Circular dichroism observations suggested that the alkalinity tuned the peptide secondary structure, which may also affect the Ag cluster size

A Peptide-Coated Gold Nanocluster Exhibits Unique Behavior in Protein Activity Inhibition

Gold nanoclusters (AuNCs) can be primed for biomedical applications through functionalization with peptide coatings. Often anchored by thiol groups, such peptide coronae not only serve as passivators but can also endow AuNCs with additional bioactive properties. In this work, we use molecular dynamics simulations to study the structure of a tridecapeptide-coated Au₂₅ cluster and its subsequent interactions with the enzyme thioredoxin reductase 1, TrxR1. We find that, in isolation, both the distribution and conformation of the coating peptides fluctuate considerably. When the coated AuNC is placed around TrxR1, however, the motion of the highly charged peptide coating (+5e/peptide) is quickly biased by electrostatic attraction to the protein; the asymmetric coating acts to guide the nanocluster’s diffusion toward the enzyme’s negatively charged active site. After the AuNC comes into contact with TrxR1, its peptide corona spreads over the protein surface to facilitate stable binding with protein. Though individual salt bridge interactions between the tridecapeptides and TrxR1 are transient in nature, the cooperative binding of the peptide-coated AuNC is very stable, overall. Interestingly, the biased corona peptide motion, the spreading and the cooperation between peptide extensions observed in AuNC binding are reminiscent of bacterial stimulus-driven approaching and adhesion mechanisms mediated by cilia. The prevailing AuNC binding mode we characterize also satisfies a notable hydrophobic interaction seen in the association of thioredoxin to TrxR1, providing a possible explanation for the AuNC binding specificity observed in experiments. Our simulations thus suggest this peptide-coated AuNC serves as an adept thioredoxin mimic that extends an array of auxiliary structural components capable of enhancing interactions with the target protein in question

Detection of pH Change in Cytoplasm of Live Myocardial Ischemia Cells via the ssDNA-SWCNTs Nanoprobes

Myocardial ischemia is featured by a significant increase in the cytoplasm proton concentration, and such a proton change may be applied as an index for earlier ischemic heart disease diagnostics. But such a pH change in a live heart cell is difficult to monitor as a normal fluorescent probe cannot specifically transport into the cytoplasm of an ischemic cell. This is because the heart cell contains condensed myofibrils which are tight barriers for a normal probe to penetrate. We design fluorescent probes, single-strand DNA wrapped single-wall carbon nanotubes (ssDNA-SWCNTs), where the ssDNA is labeled by the dye molecule hexachloro-6-carboxyfluorescein (HEX). This nanoprobe could transport well into a live heart cell and locate in the cytoplasm to sensitively detect the intracellular pH change of myocardial ischemia. Briefly, protons neutralize the negative charges of nanoprobes in the cytoplasm. This will weaken the stability of nanoprobes and further tune their aggregation. Such aggregations induce the HEX of some nanoprobes condensed together and further result in their fluorescence quenching. The nanoprobes are advantaged in penetrating condensed myofibrils of the heart cell, and their fluorescence intensity is sensitive to the proton concentration change in the live cell cytoplasm. This new method may provide great assistance in earlier cardiopathy diagnosis in the future