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CdSe/CdS/ZnS quantum dots (QDs) have been successfully encapsulated into poly(ethylene oxide) (PEO)-based polymeric micelle/silica dual layers via interfacial templating condensation. The encapsulation follows a green and straightforward microemulsion mechanism that directly proceeds in a near-neutral pH aqueous environment. No detriment to the optical properties of QDs is observed during encapsulation. The core–shell nanoparticles generated possess a polymeric micelle framework with a single QD encapsulated in the hydrophobic micellar core, an ultrathin (

Imaging of transduced cells and tissues is valuable in developing gene transfer vectors and evaluating gene therapy efficacy. We report here a simple method to use bright and photostable quantum dots to label baculovirus, an emerging gene therapy vector. The labeling was achieved through the non-covalent interaction of glutathione-capped CdTe quantum dots with the virus envelope, without the use of chemical conjugation. The quantum dot labeling was nondestructive to viral transduction function and enabled the identification of baculoviral vector-transduced, living cells based on red fluorescence. When the labeled baculoviral vectors were injected intravenously or intraventricularly for in vivo delivery of a transgene into mice, quantum dot fluorescence signals allow us monitor whether or not the injected tissues were transduced. More importantly, using a dual-color whole-body imaging technology, we demonstrated that in vivo viral transduction could be evaluated in a real-time manner in living mice. Thus, our method of labeling a read-to-use gene delivery vector with quantum dots could be useful towards the improvement of vector design and will have the potential to assess baculovirus-based gene therapy protocols in future.

A small molecule, glucosamine, is used as targeting moiety for insulin-secreting beta cell separation in artificial cell mixtures and tissue samples. The specificity of glucosamine allows it to be used in cell sorting applications. In addition, a thrombin-specific cleavable peptide was used as an intermediary to release nanoparticles from cell surfaces to facilitate cell attachment and proliferation.

In multi-interfacial polyelectrolyte complexation (MIPC), fusion of nascent fibers from multiple interfaces brings the interfaces to a point from which a composite fiber is drawn. MIPC applied to two, three, and four polyelectrolyte complex interfaces leads to various patterned multicomponent fibers. Cells encapsulated in these fibers exhibit migration, aggregation and spreading in relation to the initial cell or matrix pattern.

We investigated the interactions of different types of human and porcine renal proximal tubule-derived cells with core-shell CdSe@ZnS quantum dots (QDs) coated with polymerized histidine-formaldehyde (pHF). The results revealed that porcine and human proximal tubule cells showed a markedly different uptake behavior. This applied to flat epithelial monolayers, as well as to proximal tubules formed on two-dimensional (2D) surfaces in vitro. Primary human cells were most sensitive to the cytotoxic effects of QDs, but displayed inter-donor variability, which appeared to depend on the state of differentiation. The results suggested that human proximal tubule-derived cells were more appropriate than porcine cells for in vitro nanotoxicology. Primary human cells might be suitable when their state of differentiation and inter-donor variability were well-controlled. Furthermore, the results suggested that gel-free proximal tubules formed in vitro could be used as test system to address uptake and transport of nanometer-sized particles in human renal structures.

Water-soluble and stable quantum dots (QDs), CdTe and CdZnSe, are applied for ultrasensitive Pb(2+) detection. These QDs are capped with glutathione (GSH) shells. GSH and its polymeric form, phytochelatin, are employed by nature to detoxify heavy metal ions. As a result of specific interaction, the fluorescence intensity of GSH-capped QDs is selectively reduced in the presence of heavy metal ions such as Pb(2+). The detection limit of Pb(2+) is found to be 20 nM due to the superior fluorescence properties of QDs. Detailed studies by spectroscopy, microscopy, and dynamic light scattering show that competitive GSH binding of Pb(2+) with the QD core changed both the surface and photophysical properties of the QDs. Fluorescence of QDs is quenched, and QD aggregation occurs. Coupling the GSH-capped QDs with a high-throughput detection system, we have developed a simple scheme for quick and ultrasensitive Pb(2+) detection without the need for additional electronic devices. In the presence of ionic mixtures, our system is still capable of Pb(2+) detection with a detection limit as low as 40 nM. The system only becomes less sensitive when the ionic mixture is present at a very high concentration (i.e., > or =50 microM).

Here, we report a general and facile method for effective layer-by-layer exfoliation of transition metal dichalcogenides (TMDs) and graphite in water by using protein, bovine serum albumin (BSA) to produce single-layer nanosheets, which cannot be achieved using other commonly used bio- and synthetic polymers. Besides serving as an effective exfoliating agent, BSA can also function as a strong stabilizing agent against reaggregation of single-layer nanosheets for greatly improving their biocompatibility in biomedical applications. With significantly increased surface area, single-layer MoS2 nanosheets also exhibit a much higher binding capacity to pesticides and a much larger specific capacitance. The protein exfoliation process is carefully investigated with various control experiments and density functional theory simulations. It is interesting to find that the nonpolar groups of protein can firmly bind to TMD layers or graphene to expose polar groups in water, facilitating the effective exfoliation of single-layer nanosheets in aqueous solution. The present work will enable to optimize the fabrication of various 2D materials at high yield and large scale, and bring more opportunities to investigate the unique properties of 2D materials and exploit their novel applications.

Protein–flavin interactions modify the chemistry of the flavin, ‘tuning’ it to its biological function. In order to understand protein interactions with reduced flavins, the Raman spectrum of reduced FAD was recorded at pH values where the reduced isoalloxazine is neutral and anionic. Reduced isoalloxazine is a weaker Raman scatterer than oxidized isoalloxazine by at least an order of magnitude in both ionization states. Substitution of exchangeable protons for deuterium, the effect of ionization and DFT calculations allowed the assignment of the observed Raman bands to normal modes of vibration. Copyright © 2004 John Wiley & Sons, Ltd.

The 12S subunit of transcarboxylase is a 338 000 Da hexamer that transfers carboxlylate from methylmalonyl-CoA (MM-CoA) to biotin; in turn, the biotin transfers the carboxylate to pyruvate on another subunit, the 5S. Here, Raman difference microscopy is used to study the binding of substrate and product, and their analogues, to single crystals of 12S. A single crystal is the medium of choice because it provides Raman data of unprecedented quality. Crystalline ligand-protein complexes were formed by cocrystallization or by the soaking in/soaking out method. Raman difference spectra were obtained by subtracting the spectrum of the apo crystal from that of a crystal with the substrate or product bound. Raman difference spectra from crystals with the substrate bound are dominated by bands from the protein's amide bonds and aromatic side chain residues. In contrast, Raman difference spectra involving the product, propionyl-CoA, are dominated by modes from the ligand. These results show that substrate binding triggers a conformational change in 12S, whereas product binding does not. The conformational change involves an increase in the amount of alpha-helix since markers for this secondary structure are prominent in the difference spectra of the substrate complex. The number of MM-CoA ligands bound per 12S hexamer can be gauged from the intensity of the MM-CoA Raman features and the fact that the protein concentration in the crystals is known from X-ray crystallographic data. Most crystal samples had six MM-CoAs per hexamer although a few, from different soaking experiments, contained only 1-2. However, both sets of crystals showed the same degree of protein conformational change, indicating that the change induced by the substrate is cooperative. This effect allowed us to record the Raman spectrum of bound MM-CoA without interference from protein modes; the Raman spectrum of a 12S crystal containing 2 MM-CoA ligands per hexamer was subtracted from the Raman spectrum of a 12S crystal containing six MM-CoA ligands per hexamer. The conformational change is reversible and can be controlled by soaking out or soaking in the ligand, using either concentrated ammonium sulfate solutions or the solution used in the crystallization trials. Malonyl-CoA also binds to 12S crystals and brings about conformational changes identical to those seen for MM-CoA; in addition, butyryl-CoA binds and behaves in a manner similar to propionyl-CoA. These data implicate the -COO- group on MM-CoA (that is transferred to biotin in the reaction on the intact enzyme) as the agent bringing about the cooperative conformational change in 12S.

Colloidal orthorhombic AgGaS2 nanocrystals are synthesized from a mixture of Ag(S2CNEt2) and Ga(S2CNEt2)3 and a coordinating solvent such as dodecanethiol, hexadecanethiol, oleylamine, and hexadecylamine (Ar, 280 °C, 2 h).

An effective separation process is developed to remove free protein from the protein-protected gold clusters via co-precipitation with zinc hydroxide on their surface. After dialysis, the purified clusters exhibit an enhanced fluorescence for improved sensitive detection and selective visualization.

Various flavoenzymes can form charge-transfer (CT) complexes with their substrates or analogs. The CT bands are red-shifted from the flavin absorption bands. In the present study, under the resonance Raman condition when 647.1 nm excitation was used, resonance Raman spectra were obtained for three CT complexes formed by 3,4-dihydroxybenzoic acid (protocatechuic acid, PCA) with the flavoenzymes old yellow enzyme I (OYE I), 12-oxophytodienoate 10,11-reductase (LeOPR I) and dihydroorotate dehydrogenase A (DHOD A). Many flavin ring modes were intensity-enhanced under these conditions, although to varying degrees. However, the Raman intensity enhancements of the PCA modes were highly selective. Using phenolate binding to OYE I as a model system, and deuterium substitution in PCA, the enhanced modes were identified as benzene in-plane ring modes containing contributions from C–H bending. The intensity enhancement for these modes is up to several thousand-fold. The mechanism for the selective intensity enhancement is not understood. Although the CT absorption bands for PCA binding to OYE I, DHOD A and LeOPR I are very similar, the positions of the Raman modes of bound PCA and their response to deuterium substitution are distinct. This demonstrates that the Raman data can detect differences in the chemistry of the CT binding sites that are not apparent in the absorption spectral data. Copyright © 2001 John Wiley & Sons, Ltd.

Monomeric sarcosine oxidase, from a bacterial source, is a 43.8 kDa flavoenzyme that catalyzes the oxidation of sarcosine (N-methylglycine). The enzyme forms charge-transfer (CT) complexes with substrate analogs such as (methylthio)acetic acid (MTA), pyrrole-2-carboxylic acid (PCA) and (methylseleno)acetic acid (MSA). The structure of sarcosine oxidase complexed to either of the former two ligands has been solved recently and shows that the ligands are binding close to the re face of the isoalloxazine ring. More structural detail can be adduced from Raman spectroscopic studies of these complexes. These involve collecting Raman difference data using 647.1 nm excitation, a wavelength that is in the resonance or pre-resonance regime with regard to the CT bands. Selective intensity enhancements are observed and the difference spectra reveal a rich assortment of isoalloxazine modes and a few features due to the bound ligands. Within the CT complexes, intensity enhancement for the isoalloxazine ring vibrations is typically 1–2 orders of magnitude and is greatest for vibrations associated with the N5—C4a—C10a—N1 region of the ring. This identifies the region of the isoalloxazine ring that receives the charge transfer from the ligand and confirms, at the same time, that this region is a prime candidate for nucleophilic attack or electron transfer in any reaction scheme. Intensity enhancements for the ligand modes are much higher, typically a few thousand-fold. Isotopic substitutions combined with quantum mechanical and vibrational calculations were used to identify the ligand modes showing high intensity enhancement. For MTA and MSA these are the methyl symmetric bending and methylene wag. For PCA the pyrrole ring CH deformations show the highest intensity enhancement. Copyright © 2001 John Wiley & Sons, Ltd.

Highly emissive and air-stable AgInS2-ZnS quantum dots (ZAIS QDs) with quantum yields of up to 20% have been successfully synthesized directly in aqueous media in the presence of polyacrylic acid (PAA) and mercaptoacetic acid (MAA) as stabilizing and reactivity-controlling agents. The as-prepared water-dispersible ZAIS QDs are around 3 nm in size, possess the tetragonal chalcopyrite crystal structure, and exhibit long fluorescence lifetimes (100 ns). In addition, these ZAIS QDs are found to exhibit excellent optical and colloidal stability in physiologically relevant pH values as well as very low cytotoxicity, which render them particularly suitable for biological applications. Their potential use in biological labelling of baculoviral vectors is demonstrated.

This paper reports a simple and scalable method for the synthesis of highly fluorescent Ag, Au, Pt, and Cu nanoclusters (NCs) based on a mild etching environment made possible by phase transfer via electrostatic interactions. Using Ag as a model metal, a simple and fast (total synthesis time < 3 h) phase transfer cycle (aqueous → organic (2 h incubation) → aqueous) has been developed to process originally polydisperse, nonfluorescent, and unstable Ag NCs into monodisperse, highly fluorescent, and extremely stable Ag NCs in the same phase (aqueous) and protected by the same thiol ligand. The synthetic protocol was successfully extended to fabricate highly fluorescent Ag NCs protected by custom-designed peptides with desired functionalities (e.g., carboxyl, hydroxyl, and amine). The facile synthetic method developed in this study should largely contribute to the practical applications of this new class of fluorescence probes.

Novel mesoscopic organic nanosheets were developed by functionalizing bulk 2D organic covalent framework polymers with small molecules. The water-soluble fluorescent nanosheets are promising as nanocarriers for biological applications. Accepted version

The interaction of water-soluble cationic porphyrin meso -tetrakis(4- N -methylpyridinyl)porphyrin (TMPyP) manganese derivatives with DNA was demonstrated by their catalytic activity on the luminolH 2 O 2 chemiluminescence (CL) system. The catalytic activity of Mn-TMPyP on the CL reaction was markedly enhanced when the complex was bound to DNA. The native form of DNA and thermally denatured DNA show the same degrees of enhancement. Different degrees of enhancement were obtained when Mn-TMPyP interacted with RNA and polynucleotides, whereas the interaction of nucleotides and bases with Mn-TMPyP had no effect on its catalytic activity. To examine the effect of the peripheral group of the porphyrin on its bonding properties, the interaction of manganese tetrakis(4-aminophenyl)porphyrin (Mn-TPPA 4 ), manganese tetrakis(carboxylphenyl)porphyrin (Mn-TPPC 4 ), manganese tetrakis(sulphophenyl)porphyrin (Mn-TPPS 4 ) and manganese tetrakis(4-trimethylaminophenyl)porphyrin (Mn_TAPP) with DNA was tested. Only the Mn-TPPA 4 -catalysed CL reaction was significantly enhanced. The effects of the native form of DNA and thermally denatured DNA on the Mn-TPPA 4 -catalysed CL reaction were very different to that on the Mn-TMPyP-catalysed CL reaction. With a fixed concentration of Mn-TMPyP there was a saturated concentration of DNA with respect to the metalloporphyrin (M-P). The binding number of M-P to DNA was estimated. Optimum conditions of the M-PDNA complex-catalysed luminol CL reaction were evaluated by using a flow-injection system. The use of the analytical parameters of the phenomenon as a means of determining DNA was examined. The detection limit (signal-to-noise ratio > 3) of DNA was 0.20 ng ml −1 . The relative standard deviation ( n = 11) of the determination of 10 ng ml −1 DNA was 2.6%.

A simple label-free method for the detection of Hg(2+) ions with high selectivity and sensitivity has been developed by using fluorescent Au NCs in aqueous media. The sensing mechanism was based on the high-affinity metallophilic Hg(2+)-Au(+) interactions, which effectively quenched the fluorescence of Au NCs.

A simple, one-pot, "green" synthetic route, based on the "biomineralization" capability of a common commercially available protein, bovine serum albumin (BSA), has been developed for the preparation of highly stable Au nanocrystals (NCs) with red emission and high quantum yield.

We have developed a new synthetic method for producing high-quality quantum dots (QDs) in aqueous solution for biological imaging applications. The glutathione-capped CdTe, ZnSe and Zn 1-x Cd x Se alloyed QDs derived are tunable in fluorescence emissions between 360 nm and 700 nm. They show high quantum yields (QYs) of up to 50%, with narrow bandwidths of 19-55 nm. The synthesis of glutathione-capped QDs is simple and cost-effective compared to the conventional organometallic approaches. It can be easily scaled up for the commercial production of alloyed nanocrystals of various compositions. We have also demonstrated the fabrication of magnetic quantum dots (MQDs) through a seed-mediated approach. The formation and assembly of these bifunctional nanocomposites have been elucidated by high-resolution transmission electron microscopy (HRTEM). The MQDs exhibit superparamagnetism and tunable emissions characteristic of the components in this hybrid system. We have created biocompatible silica-coated MQDs that effectively target the cell membranes.

Water-soluble, silane-functionalized ZnO nanocrystals were synthesized with improved colloidal stability, and their photostability was controlled for the selective detection of aldehydes.

We report on large three-photon absorption (3PA) in glutathione-capped ZnS semiconductor nanocrystals (NCs), determined by both Z-scan and transient transmission techniques with 120-fs laser pulses. The monodispersed, water-soluble ZnS NCs are synthesized by a modified protocol with a mean diameter of 2.5 nm. Their 3PA cross-section is determined to be around 2.7x10^-78 cm^6s^2photon^-2 at an optimal wavelength of commercial Ti:sapphire femtosecond lasers. This value is nearly one order of magnitude greater than that of CdS NCs, and four to five orders of magnitude higher than those of the previously reported common UV fluorescent dyes., 15 pages, 4 figures

In the field of nanoscience, the ability to prepare high-quality nanocrystals is crucial for fundamental research and technology development. Herein, we review a general route for the colloidal preparation of monodisperse nanocrystals, which is divided into five different stages, namely (i) nucleation, (ii) growth, (iii) Ostwald ripening, (iv) surfactant capping and (v) precipitation. Each of the five stages is discussed in detail to provide a comprehensive understanding of the mechanism behind nanocrystal formation and the subsequent processing steps. We put emphasis on the classical theories and experimental techniques that are most frequently practiced. These are useful for the successful design and fabrication of nanocrystals with properties that are beneficial for use in a plethora of technological applications.

Near-IR ultrafast pulse laser and confocal microscope are combined to create a multiphoton multichannel non-linear imaging technique, which allows in situ 3-D characterization of nonfluorescent nanoparticles in biological systems. We observed intense CARS signals generated from various metal oxides due to their high third-order nonlinear susceptibilities (Chi(3)), which do not depend on the vibrational resonance but on the electronic resonance. We show that fine and ultrafine particles of metal oxides in alveolar macrophage cells may be imaged in vitro using CARS and multiphoton fluorescence microscopy with highest optical resolution for extended periods without photobleaching effects. The advantage of the epi-detection over the forward detection for imaging sub-micron particles has been investigated.

AgGaS2 (AGS) nanocrystals that exist in the orthorhombic phase were successfully prepared for the first time through a one-pot colloidal synthetic strategy using suitable coordinating solvents. These orthorhombic AGS nanocrystals were found to display great potential in visible-light-driven photocatalysis.

By using a Raman microscope, we show that it is possible to probe the conformational states in protein crystals and crystal fragments under growth conditions (in hanging drops). The flavin cofactor in the enzyme para -hydroxybenzoate hydroxylase can assume two conformations: buried in the protein matrix (“in”) or essentially solvent-exposed (“out”). By using Raman difference spectroscopy, we previously have identified characteristic flavin marker bands for the in and out conformers in the solution phase. Now we show that the flavin Raman bands can be used to probe these conformational states in crystals, permitting a comparison between solution and crystal environments. The in or out marker bands are similar for the respective conformers in the crystal and in solution; however, significant differences do exist, showing that the environments for the flavin's isoalloxazine ring are not identical in the two phases. Moreover, the Raman-band widths of the flavin modes are narrower for both in and out conformers in the crystals, indicating that the flavin exists in a more limited range of closely related conformational states in the crystal than in solution. In general, the ability to compare detailed Raman data for complexes in crystals and solution provides a means of bridging crystallographic and solution studies.

In this communication, we present the colloidal preparation of ternary CuGaS2 (CGS) nanocrystals that exhibit elongated morphologies and possess the metastable wurtzite crystal structure. A facile noninjection-based synthetic strategy was utilized wherein dithiocarbamate complexes of copper and gallium were thermally decomposed in the presence of dodecanethiol. The anisotropic CGS nanocrystals were found to display promising photocatalytic behaviour under visible-light illumination.

In this article, the very recent progress of various functional inorganic nanomaterials is reviewed including their unique properties, surface functionalization strategies, and applications in biosensing and imaging-guided therapeutics. The proper surface functionalization renders them with stability, biocompatibility and functionality in physiological environments, and further enables their targeted use in bioapplications after bioconjugation via selective and specific recognition. The surface-functionalized nanoprobes using the most actively studied nanoparticles (i.e., gold nanoparticles, quantum dots, upconversion nanoparticles, and magnetic nanoparticles) make them an excellent platform for a wide range of bioapplications. With more efforts in recent years, they have been widely developed as labeling probes to detect various biological species such as proteins, nucleic acids and ions, and extensively employed as imaging probes to guide therapeutics such as drug/gene delivery and photothermal/photodynamic therapy.

Highly emissive and air-stable AgInS2–ZnS quantum dots (ZAIS QDs) with quantum yields of up to 20% have been successfully synthesized directly in aqueous media in the presence of polyacrylic acid (PAA) and mercaptoacetic acid (MAA) as stabilizing and reactivity-controlling agents. The as-prepared water-dispersible ZAIS QDs are around 3 nm in size, possess the tetragonal chalcopyrite crystal structure, and exhibit long fluorescence lifetimes (>100 ns). In addition, these ZAIS QDs are found to exhibit excellent optical and colloidal stability in physiologically relevant pH values as well as very low cytotoxicity, which render them particularly suitable for biological applications. Their potential use in biological labelling of baculoviral vectors is demonstrated.

Engineering the structure and/or composition of Pt nanoparticles has been an effective approach to improve the catalytic activity on a mass basis. Herein we demonstrate for the first time the synthesis of core-shell CdSe@Pt nanocomposites at different CdSe/Pt molar ratios. By reducing platinum precursors with sodium citrate in the presence of previously formed CdSe nanocrystals in aqueous phase, uniform core-shell CdSe@Pt nanocomposites are obtained as the dominant product. These core-shell CdSe@Pt nanocomposites exhibit superior catalytic activity toward reactions in direct methanol fuel cells (DMFCs). The inner-placed CdSe core is helpful for saving a substantial amount of valuable platinum metal. In addition, this core-shell structure also offers a vivid example for investigation of the lateral strain effect of the substrate on the deposited layers, and its influence on the catalytic activity of metal catalysts.

We present a demonstration of the unambiguous determination of two-photon absorption (2PA) and three-photon absorption (3PA) in semiconductor quantum dots in the vicinity of E0/2, where E0 denotes the peak position of the lowest exciton energy. In the spectral region where photon energies ℏω≥E0/2, the 2PA cross section is determined by open-aperture Z scans with femtosecond laser pulses at relatively lower irradiances, and then the 3PA cross section is extracted from the Z scans measured at higher irradiances. As photon energies are less than but near E0/2, multiphoton-excited photoluminescence techniques have to be employed in conjunction with open-aperture Z scan to distinguish between 2PA and 3PA.

Three-photon absorption (3PA) and three-photon-excited photoluminescence (3PE-PL) of ZnSe/ZnS and copper-doped ZnSe/ZnS core-shell quantum dots (QDs) in aqueous solutions have been unambiguously determined by Z-scan and 3PE-PL measurements with 200-fs laser pulses at 1000 nm. The 3PA cross-section is as high as 3.5 x 10(-77) cm6 s2 photon(-2) for 4.1 nm-sized, copper-doped ZnSe/ZnS QDs, while their below-band-edge PL is found to be nearly cubic dependent on the excitation intensity, with efficiency enhanced by approximately 20 fold compared to the undoped ZnSe/ZnS QDs.

Auger recombination, quantized Auger rate, and intraband absorption of two-photon-excited carriers in colloidal CdSe quantum dots have been investigated systematically with femtosecond Z scans and transient absorption measurements. The Auger constant is revealed to be on the order of 10−30cm6s−1, while the intraband absorption cross sections are found to be in the range of 10−18–10−17cm2. The authors’ experimental evidence demonstrates that the Auger recombination or the intraband absorption takes place under the condition that the average electron-hole pair per quantum dot is in excess of the unity.