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.Topics: Biosensors; Cell and Molecular biology; Drug discovery and Drug delivery systems; Fluorescence; Fluorescence microscopy; Luminescence spectroscopy; Mass spectrometry; Metal clusters; Optical materials; Peptides and Proteins; Proteins; Spectra;

A facile method to synthesize ultrasmall-sized supermagnetic iron oxide nanoparticles with good monodispersity and high relaxivity is desired for magnetic resonance imaging (MRI) technology. Herein, we have developed a one-step method to direct the formation of superparamagnetic iron oxide nanoparticle (uBSPIO) using albumin under mild conditions. The resulting uBSPIO possess ultrasmall size (4.78 ± 0.55 nm) and super high MR relaxivity (444.56 ± 8.82 mM–1 s–1). After grafted by the luteinizing hormone release hormone peptide (LHRH), the uBSPIO could targeted and accumulated in the tumor site. Finally, the uBSPIOs had good stability and did not induce cytotoxicity in vitro or major organ toxicity in vivo. The uBSPIOs are promising contrast agents for MRI.Keywords: biomineralization; BSA; T2-weighted magnetic resonance imaging; ultrasmall superparamagnetic iron oxide;

Chronic lymphocytic leukaemia (CLL) is a rare blood cancer that always relapses as refractory disease and eventually leads to death. To date, therapeutic options for CLL patients are scarce and there is an urgent need to develop novel chemotherapeutics that are both effective and safe. Gold-containing compounds induce a lethal oxidative and endoplasmic reticulum stress response in cultured and primary CLL cells via inhibition of thioredoxin reductase (TrxR). However, traditional gold-containing medicines have revealed side effects during clinical applications. Therefore, safer gold-containing drugs are needed to overcome this challenge. In this study, a novel peptide templated gold cluster Au25Sv9 was synthesized and its therapeutic effect on CLL cells was evaluated. This nanocluster could induce cell apoptosis in MEC-1 cells in a dose-dependent manner which correlated with the uptake amount of clusters in cells. As expected, increasing intracellular reactive oxidative species (ROS) in MEC-1 cells was exhibited with the increase of cluster dosage. Further analyses demonstrated the underlying mechanism that the nanoclusters suppress the activity of TrxR1, increase the level of intracellular ROS, destroy the mitochondrial membrane potential and finally trigger the mitochondrial apoptotic pathway in MEC-1 cells. Furthermore, the direct interaction between Au25Sv9 clusters and TrxR1 was confirmed for the first time by isothermal titration calorimetry. These findings explored the preclinical efficacy and potential mechanism of gold clusters in CLL therapy and provided a fundamental reference for the development of other novel gold-containing chemotherapeutics to treat CLL.Download high-res image (179KB)Download full-size image

•Stable fluorescent gold clusters are constructed through in situ biomineralization of Au (III) by glucose oxidase.•Glucose oxidase serves as both a template and reducing agent.•A metal-cluster-based optical sensor is developed for Hg2+ detection with high selectivity and sensitivity.Mercury ion (Hg2+) pollution has deleterious effects on the environment and human health. Herein, through one-step biomimetic mineralization of metal salt with a natural protein, we develop an optical sensor system for Hg2+ detection with high selectivity and sensitivity. Glucose oxidase (GOD) serves as both a template and reducing agent to achieve the in situ biomineralization of Au (III), producing stable fluorescent GOD-conjugated gold clusters (GOD-AuCs) with a high yield. The probe above with a uniform core size of around 2.5 nm, has an obvious maximum fluorescence emission peak at 686 nm. GOD-AuCs exhibit good selectivity to Hg2+, in comparison to other metal ions including K+, Na+, Ca2+, Mg2+, Zn2+ and Cu2+. The reason might be that the existence of a small amount of Au+ (21%) on the surface of the cluster, permits strong metallophilic interaction between GOD-AuCs and Hg2+. It results in the instantaneous and remarkable fluorescence quench. Moreover, the intensity of fluorescence quench is found to be linearly depended on the concentration of Hg2+, with a detection limit of 7.5 μM. These favorable findings promise GOD-AuCs have a good potential in monitoring environmental Hg2+.Download high-res image (230KB)Download full-size image

Multi-modal imaging agents are desirable for tumor diagnosis because they can provide more information on the tumor than single-modal imaging agents. However, most reported multi-modal imaging agents are dual-modal agents rather than tri-modal agents; therefore, detailed information on the tumor may still be insufficient when such imaging agents are used. To ameliorate this issue, we synthesized a tri-modal imaging agent, composed of gold cluster and gadolinium oxide integrated nanoparticles (denoted as AuGds) using bovine serum albumin (BSA) as the template via a bio-mineralization method. The AuGds exhibit red fluorescence at ∼660 nm for optical imaging, strong X-ray absorption (around 700 HU) for CT imaging, and a high r1 value (∼12.39 mM−1 s−1) for MR imaging. After being chemically modified with folic acid (FA), the AuGds can specifically target folate receptors on KB tumor cells, and permit in vivo optical, MR, and CT imaging of xenografted tumors. By comparing these three imaging modalities, very clear structural and anatomical information on the in vivo tumor can be obtained. The AuGds show good biocompatibility, quick renal clearance, and do not induce normal tissue toxicity in vivo.

Bridging the gap between atoms and nanoparticles, noble metal clusters with atomic precision continue to attract considerable attention due to their important applications in catalysis, energy transformation, biosensing and biomedicine. Greatly different to common chemical synthesis, a one-step biomimetic synthesis of peptide-conjugated metal clusters has been developed to meet the demand of emerging bioapplications. Under mild conditions, multifunctional peptides containing metal capturing, reactive and targeting groups are rationally designed and elaborately synthesized to fabricate atomically precise peptide protected metal clusters. Among them, peptide-protected Au Cs (peptide–Au Cs) possess a great deal of exceptional advantages such as nanometer dimensions, high photostability, good biocompatibility, accurate chemical formula and specific protein targeting capacity. In this review article, we focus on the recent advances in potential theranostic fields by introducing the rising progress of peptide–Au Cs for biological imaging, biological analysis and therapeutic applications. The interactions between Au Cs and biological systems as well as potential mechanisms are also our concerned theme. We expect that the rapidly growing interest in Au Cs-based theranostic applications will attract broader concerns across various disciplines.

We have designed a novel peptide-Au cluster probe to specifically bind to αIIbβ3 integrin. As indicated by molecular dynamics (MD) simulations, the binding mode of the native ligand of αIIbβ3 integrin, γC peptide, can be realized by the designed probe. More importantly, the peptide-Au probe can provide multiple coating peptides to form additional salt bridges with protein, and the binding stability of the probe is comparable to the native ligand. The designed probe was then successfully synthesized. The specific binding in a cellular environment was validated by colocalization analysis of confocal microscopy. In addition, the binding affinity was confirmed by atomic force microscopy (AFM) based single molecule force spectroscopy. Our results suggest the combination of computational design and experimental verification can be a useful strategy for the development of nanoprobes.

Kidney disease is a worldwide health hazard. Noninvasive imaging modalities such as computed tomography are often used for diagnosis, to guide treatment, and to assess a disease state over the long-term. The physiology of the kidneys can be assessed with contrast agents. We present an albumin-stabilized Au cluster with red fluorescence and robust X-ray attenuation. In vivo studies revealed distribution of the Au clusters in the liver, spleen, and kidneys, with excretion mostly via the kidneys. Under optimal conditions, this agent can outline the anatomy of mouse kidneys on 2D and 3D computed tomography imaging, with clear visualization of the renal collecting system and ureters. This is a promising agent for kidney visualization and disease diagnosis.

We report for the first time seeing and counting integrin αIIbβ3 on a single-cell level. The proposed method is based on the using of the Au cluster probe. With the fluorescent property of Au24 cluster and the specific targeting ability of peptide, our probe can directly visualize integrin αIIbβ3 on the membrane of human erythroleukemia cells (HEL) via confocal microscopy. On the basis of the accurate formula of our probe (Au24Peptide8), the number of integrin αIIbβ3 can be precisely counted by quantifying the gold content on a single HEL cell via laser ablation inductively coupled plasma mass spectrometry. Our results reveal that the number of integrin αIIbβ3 on a single cell varies from 5.75 × 10–17 to 9.11 × 10–17 mol, because of the heteroexpression levels of αIIbβ3 on individual cells.

Mercury ion (Hg2+ ) pollution exists in water, soil, and food. By interacting with the thiol groups in protein, Hg2+ ions can accumulate in ways that cause serious damage to the central nervous system and threaten human health and natural environment. Undoubtedly, Hg2+ ion detection is a significant issue in environment and health monitoring. A variety of sensor platforms for Hg2+ ion detection based on organic molecules, DNA, oligonucleotides, inorganic materials, etc, have been reported. In this paper, an artificial peptide PHg, with a cluster bio-mineralize sequence (CCY) and a multi-charge hydrophilic sequence is designed as a template for the one-step synthesis of a peptide-Au cluster probe. Briefly: the peptide PHg in situ anchors Au ions to form a peptide-Au (I) intermediate and the reaction pH with NaOH is adjusted; after 12 h incubation at room temperature, the peptide PHg-Au nanocluster probe with red fluorescence is obtained. The probe has a super-small core size of approximately 1.26 nm and a maximum emission peak at 650 nm. The presence of Hg2+ ions cause the fluorescence of the probe to greatly decrease. Based on the differences in fluorescence intensity of the PHg-Au nanocluster in the absence and presence of Hg2+ ions, Hg2+ ions could be quantitatively detected in concentrations ranging from 5 nmol/L to 1 µmol/L. The limit of detection (LOD) is 7.5 nmol/L. Compared with some interference ions such as, K+, Mg2+, Ca2+, Pb2+, Ni2+, Fe3+, and Cu2+, the selectivity was excellent. The sensing of Hg2+ ion is not affected by the chelate agents: EDTA, which imparts a significant advantage in a range of applications. As a result, a simple, sensitive and selective fluorescent assay based on peptide PHg-Au cluster is developed for the detection of Hg2+ ions.

Positron emission tomography (PET) imaging has received special attention owing to its higher sensitivity, temporal resolution, and unlimited tissue penetration. The development of tracers that target specific molecules is therefore essential for the development and utility of clinically relevant PET procedures. However, 64Cu as a PET imaging agent generally has been introduced into biomaterials through macrocyclic chelators, which may lead to the misinterpretation of PET imaging results due to the detachment and transchelation of 64Cu. In this study, we have developed ultrasmall chelator-free radioactive [64Cu]Cu nanoclusters using bovine serum albumin (BSA) as a scaffold for PET imaging in an orthotopic lung cancer model. We preconjugated the tumor target peptide luteinizing hormone releasing hormone (LHRH) to BSA molecules to prepare [64Cu]CuNC@BSA-LHRH. The prepared [64Cu]Cu nanoclusters showed high radiolabeling stability, ultrasmall size, and rapid deposition and diffusion into tumor, as well as predominantly renal clearance. [64Cu]CuNC@BSA-LHRH showed 4 times higher tumor uptake compared with that of [64Cu]CuNC@BSA by analyzing the 64Cu radioactivity of tissues via gamma counting. The PET imaging using [64Cu]Cu nanoclusters as tracers showed more sensitive, accurate, and deep penetration imaging of orthotopic lung cancer in vivo compared with near-infrared fluorescence imaging. The nanoclusters provide biomedical research tools for PET molecular imaging.Keywords: 64copper nanoclusters; luteinizing hormone releasing hormone; orthotopic lung tumor; positron emission tomography imaging; tumor target;

Precisely quantifying the membrane protein expression level on cell surfaces is of vital importance for early cancer diagnosis and efficient treatment. We demonstrate that gold nanoparticle bioconjugated by a rationally designed peptide as nanoprobe possesses selective labeling and accurate quantification capacity of integrin GPIIb/IIIa on the human erythroleukemia cell line. Through selective recognition and marking of integrin, two-photon photoluminescence of the nanoprobe is exploited for direct observation of protein spatial distribution on cell membrane. More importantly, utilizing intrinsic enzyme-like catalysis property of the nanoprobe, the expression level of integrin on human erythroleukemia cells can be quantitatively counted in an amplified and reliable colorimetric assay without cell lysis and protein extraction process. In addition, the analysis of the correlation between the gold nanoparticle and the membrane protein via relevant inductively coupled plasma mass spectrometry measurement verifies the reliability of the new analytical method. It is anticipated that this facile and efficient strategy holds a great promise for a rapid, precise, and reliable quantification of interested functional membrane proteins on the cell surface.Keywords: enzyme-linked immunosorbent assay; gold nanoparticles; membrane protein quantification; nanozyme; two-photon imaging;

Au25 clusters stabilized by tridecapeptides were firstly synthesized, which can well penetrate the cell membrane and exactly locate in the cytoplasm. Hence the Au clusters significantly suppress the TrxR1 activity in the cytoplasm, and further induce the up-regulation of the activated PARP level which allows the tumor cell apoptosis to occur in a Au dose dependent manner.

Polyethylene glycol modified graphene oxide (GO-PEG) nanoparticles were prepared, which were positively charged and fairly stable in buffer solution. The GO-PEG nanoparticles possess a special affinity to the plasma membrane of live cells, and their yellowish-green fluorescence is sensitively responsive to the extracellular physiological solution in situ.

A probe composed of an aptamer and a silver cluster, where the aptamer targets mIgM of live cells and the silver cluster provides fluorescent imaging and mass quantification of mIgM of live cells, is presented. This new probe simultaneously provides accurate spatial and mass information of mIgM in live cells.

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.

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, in vitro, 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.Keywords: gold nanocages; hot electrons; photodynamic therapy; plasmon-enabled photochemistry; reactive oxygen species; two-photon

The unique honeycomb lattice structure of graphene gives rise to its outstanding electronic properties such as ultrahigh carrier mobility, ballistic transport, and more. However, a crucial obstacle to its use in the electronics industry is its lack of an energy bandgap. A covalent chemistry strategy could overcome this problem, and would have the benefits of being highly controllable and stable in the ambient environment. One possible approach is aryl diazonium functionalization.In this Account, we investigate the micromolecular/lattice structure, electronic structure, and electron-transport properties of nitrophenyl-diazonium-functionalized graphene. We find that nitrophenyl groups mainly adopt random and inhomogeneous configurations on the graphene basal plane, and that their bonding with graphene carbon atoms leads to slight elongation of the graphene lattice spacing. By contrast, hydrogenated graphene has a compressed lattice. Low levels of functionalization suppressed the electric conductivity of the resulting functionalized graphene, while highly functionalized graphene showed the opposite effect. This difference arises from the competition between the charge transfer effect and the scattering enhancement effect introduced by nitrophenyl groups bonding with graphene carbon atoms. Detailed electron transport measurements revealed that the nitrophenyl diazonium functionalization locally breaks the symmetry of graphene lattice, which leads to an increase in the density of state near the Fermi level, thus increasing the carrier density. On the other hand, the bonded nitrophenyl groups act as scattering centers, lowering the mean free path of the charge carriers and suppressing the carrier mobility.In rare cases, we observed ordered configurations of nitrophenyl groups in local domains on graphene flakes due to fluctuations in the reaction processes. We describe one example of such a superlattice, with a lattice constant nearly twice of that of pristine graphene. We performed comprehensive theoretical calculations to investigate the lattice and the electronic structure of the superlattice structure. Our results reveal that it is a thermodynamically stable, spin-polarized semiconductor with a bandgap of ∼0.5 eV.Our results demonstrate the possibility of controlling graphene’s electronic properties using aryl diazonium functionalization. Asymmetric addition of aryl groups to different sublattices of graphene is a promising approach for producing ferromagnetic, semiconductive graphene, which will have broad applications in the electronic industry.

To date, RNase degradation and endosome/lysosome trapping are still serious problems for siRNA-based molecular therapy, although different kinds of delivery formulations have been tried. In this report, a cell penetrating peptide (CPP, including a positively charged segment, a linear segment, and a hydrophobic segment) and a single wall carbon nanotube (SWCNT) are applied together by a simple method to act as a siRNA delivery system. The siRNAs first form a complex with the positively charged segment of CPP via electrostatic forces, and the siRNA–CPP further coats the surface of the SWCNT via hydrophobic interactions. This siRNA delivery system is non-sensitive to RNase and can avoid endosome/lysosome trapping in vitro. When this siRNA delivery system is studied in Hela cells, siRNA uptake was observed in 98% Hela cells, and over 70% mRNA of mammalian target of rapamycin (mTOR) is knocked down, triggering cell apoptosis on a significant scale. Our siRNA delivery system is easy to handle and benign to cultured cells, providing a very efficient approach for the delivery of siRNA into the cell cytosol and cleaving the target mRNA therein.

A bifunctional peptide was designed to in situ reduce Cu ions and anchor a Cu cluster. The peptide–Cu cluster probe, mainly composed of Cu14, emitted blue two-photon fluorescence under femtosecond laser excitation. Most important, the probe can specifically mark the nuclei of HeLa and A549 cells, respectively.

A terbium based fluorescent probe was synthesized by coordinating terbium ions with a designed oligonucleotides (5′-ATATGGGGGATAT-3′, termed GH5). GH5 improved the fluorescence of terbium ions by four orders of magnitude. The fluorescence enhancement of terbium ions by different oligonucleotides sequences indicated that the polyguanine loop of the hairpin GH5 is key to enhance terbium ion emission. The quantum yield of Tb–GH5 probe was 10.5% and the probe was photo-stable. The result of conductivity titration indicated that the stoichiometry of the probe is 3.5 Tb: 1 GH5, which is confirmed by fluorescence titration. This probe had high sensitivity and specificity for the detection of lead ions. The fluorescence intensity of this probe was linear with respect to lead concentration over a range 0.3–2.1 nM (R2 = 0.99). The limit of detection for lead ions was 0.1 nM at a signal-to-noise ratio of 3.

Luminescent silver nanoclusters were anchored by designed oligonucleotides. After hybridizing with human telomerase RNA template, the luminescence of the cluster decreased linearly with respect to the concentration of the complementary strand (25–250 nM). The cluster is therefore a potential candidate for human telomerase detection.

Graphene sheets were successfully functionalized with 4-nitrophenyl diazonium (NPD). Two dimensional Raman analysis demonstrated that the reaction preferred to happen on single-layer graphene rather than bi-layer or multi-layer, and the edges of graphene were more reactive than the central areas. Atomic force microscopy (AFM) indicated the aryl groups were covalently bonded to one side of the graphene basal plane in a perpendicular configuration. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) manifested that the modified graphene maintained the hexagonal symmetry but its microstructure changed. The main change was that the crystal lattice expanded compared with that of pristine graphene. Meanwhile, for the first time, a crystal lattice constant d ≈ 5.30 Å of functionalized graphene was obtained, which was approximately twice that of the pristine graphene's crystal lattice constant. This implied that the modified graphene had a super-lattice microstructure. Furthermore, the fast Fourier transform (FFT) of the modified graphene verified the formation of the super-lattice structures, and density functional theory (DFT) calculations showed the stability of the super-lattice structures. These modifications—elongation of crystal lattice constant and formation of super-lattice structures—may induce different electronic structures in graphene.

A bifunctional peptide containing a domain that targets cell nuclei and a domain with the ability to biomineralize and capture Au clusters is presented. The peptide–Au clusters exhibit red emission (λem = 677 nm) and specifically stain the nuclei of three cell lines.

Silver cluster–aptamer hybrids were mineralized via an artificially designed aptamer. The hybrids gave red emission when excited by light, and they successfully targeted the nucleus of live cells. This method is an effective approach to make cell target probes.

In this report, nanoprobes which could detect the femtogram level of arsenite ions in subcellular organelle of live cells are disclosed. The nanoprobes are composed of ssDNA and single-wall carbon nanotubes (SWCNTs), and the ssDNA is marked by a dye molecule. In a live cell, trace arsenite ions could interact with nanoprobes and significantly decrease the emission of the nanoprobes. With the help of a confocal microscope and cryo-electron microscopy, the lysosome target of the arsenite ion and nanoprobe is well described in high spatial resolution.Keywords: arsenite ion; femtogram; live cell; nanoprobe; ssDNA; SWCNTs

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.Keywords: conductivity; covalently bonding; graphene; nitrophenyl groups; Raman spectrum

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.Keywords: biomineralization; peptide; reduction potential; secondary structure; silver cluster

The red photoluminescence of Mn dopants in MnS−CdS heteronanostructures has been observed for the first time. The red photoluminescence at 650 nm derives from emission due to the 4T1 → 6A1 transition of Mn2+ dopants in a CdS matrix exposed to gigapascal-level lattice stress. HRTEM, FFT, XRD, and optical studies revealed that the lattice of Mn-doped CdS is compressed to match that of MnS when CdS crystallizes at the MnS surface to form MnS−CdS heteronanostructures. The photoluminescence decay times of such Mn dopants are on the order of nanoseconds because of the spin-flip interactions between Mn dopants and free carriers in the CdS matrix.

We developed a method to synthesize paramagnetic nanoparticles of Gd@C82(OH)22±2. Such nanoparticles are with ordered microstructures and have strong MRI proton relaxation in vitro/vivo. Compared with commercial Gd-DTPA, a 12× MRI relaxivity of Gd@C82(OH)22±2 nanoparticles with ordered microstructures was achieved in vitro. The small Gd@C82(OH)22±2 nanoparticles, ∼65nm, could easily escape the RES uptake in vivo; this opens the door for their clinical applications.

A bifunctional peptide was designed to in situ reduce Cu ions and anchor a Cu cluster. The peptide–Cu cluster probe, mainly composed of Cu14, emitted blue two-photon fluorescence under femtosecond laser excitation. Most important, the probe can specifically mark the nuclei of HeLa and A549 cells, respectively.

Polyethylene glycol modified graphene oxide (GO-PEG) nanoparticles were prepared, which were positively charged and fairly stable in buffer solution. The GO-PEG nanoparticles possess a special affinity to the plasma membrane of live cells, and their yellowish-green fluorescence is sensitively responsive to the extracellular physiological solution in situ.

Graphene sheets were successfully functionalized with 4-nitrophenyl diazonium (NPD). Two dimensional Raman analysis demonstrated that the reaction preferred to happen on single-layer graphene rather than bi-layer or multi-layer, and the edges of graphene were more reactive than the central areas. Atomic force microscopy (AFM) indicated the aryl groups were covalently bonded to one side of the graphene basal plane in a perpendicular configuration. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) manifested that the modified graphene maintained the hexagonal symmetry but its microstructure changed. The main change was that the crystal lattice expanded compared with that of pristine graphene. Meanwhile, for the first time, a crystal lattice constant d ≈ 5.30 Å of functionalized graphene was obtained, which was approximately twice that of the pristine graphene's crystal lattice constant. This implied that the modified graphene had a super-lattice microstructure. Furthermore, the fast Fourier transform (FFT) of the modified graphene verified the formation of the super-lattice structures, and density functional theory (DFT) calculations showed the stability of the super-lattice structures. These modifications—elongation of crystal lattice constant and formation of super-lattice structures—may induce different electronic structures in graphene.

Silver cluster–aptamer hybrids were mineralized via an artificially designed aptamer. The hybrids gave red emission when excited by light, and they successfully targeted the nucleus of live cells. This method is an effective approach to make cell target probes.

A bifunctional peptide containing a domain that targets cell nuclei and a domain with the ability to biomineralize and capture Au clusters is presented. The peptide–Au clusters exhibit red emission (λem = 677 nm) and specifically stain the nuclei of three cell lines.

Au25 clusters stabilized by tridecapeptides were firstly synthesized, which can well penetrate the cell membrane and exactly locate in the cytoplasm. Hence the Au clusters significantly suppress the TrxR1 activity in the cytoplasm, and further induce the up-regulation of the activated PARP level which allows the tumor cell apoptosis to occur in a Au dose dependent manner.

A probe composed of an aptamer and a silver cluster, where the aptamer targets mIgM of live cells and the silver cluster provides fluorescent imaging and mass quantification of mIgM of live cells, is presented. This new probe simultaneously provides accurate spatial and mass information of mIgM in live cells.