Surface Of AuNPs Research Articles

Atomic structure and optical properties of color centers of silver in AgAu/glass irradiated by UV laser

A study of the structural states of silver in glass after Ag+↔Na+ ion-exchange and further irradiation with different numbers of UV laser pulses has been performed using Ag K-edge XANES combined with DFT simulations and the processing of Ag K-EXAFS. Theoretical Ag K-edge XANES, calculated for DFT-generated structural models, showed high sensitivity to the number of nearest oxygen neighbors of the absorbing Ag+ ion, to changes in the corresponding interatomic distances RAg-O (changes ≳ 0.05 Å) and bond angles (changes ≳ 10° at apical Ag in atomic chain O–Ag–O), and to the presence of Ag+ ions among the second neighbors of Ag. The effect of more distant O and Si neighbors can be considered negligible. The applied combination of complementary techniques for structural analysis of the color centers of silver in glass has revealed that, after ion-exchange, Ag+ ions are predominantly present in glass in the form of dimers, in which the two Ag+ ions are separated by an interatomic distance, RAg-Ag, of 3.4 Å. Other interatomic distances RAg-O in the dimers have also been obtained. It has been determined that, under laser irradiation with the number of pulses up to 1000, only a small proportion (up to 10%) of Ag+ ions in glass samples is reduced from the states of isolated ions and the revealed Ag dimers present after Ag+↔Na+ ion-exchange. The reduced Ag atoms form monometallic Ag NPs and are also deposited on the surface of Au NPs, forming bimetallic AgAu NPs with a solid solution structure. The processes of the formation, growth, and dissolution of monometallic Ag NPs and bimetallic AgAu NPs with increasing number of laser pulses are discussed. Analysis of the blue shifts of ca. 20 nm of localized surface plasmon resonances (LSPRs) of Ag NPs with increasing number of UV laser pulses up to 1000 revealed that these shifts occurred due to a decrease in the average size of optically visible Ag NPs caused by the growth of initially less visible small Ag NPs (≲5 nm) and partial dissolution of the largest particles.

Bioactivated and PEG-Protected Circa 2nm Gold Nanoparticles for in Cell Labelling and Cryo-Electron Microscopy.

Advances in cryo-electron microscopy (EM) enable imaging of protein assemblies within mammalian cells in a near native state when samples are preserved by cryogenic vitrification. To accompany this progress, specialized EM labelling protocols must be developed. Gold nanoparticles (AuNPs) of 2nm are synthesized and functionalized to bind selected intracellular targets inside living human cells and to be detected in vitreous sections. As a proof of concept, thioaminobenzoate-, thionitrobenzoate-coordinated gold nanoparticles are functionalized on their surface with SV40 Nuclear Localization Signal (NLS)-containing peptides and 2kDa polyethyleneglycols (PEG) by thiolate exchange to target the importin-mediated nuclear machinery and facilitate cytosolic diffusion by shielding the AuNP surface from non-specific binding to cell components, respectively. After delivery by electroporation into the cytoplasm of living human cells, the PEG-coated AuNPs diffuse freely in the cytoplasm but do not enter the nucleus. Incorporation of NLS within the PEG coverage promotes a quick nuclear import of the nanoparticles in relation to the density of NLS onto the AuNPs. Cryo-EM of vitreous cell sections demonstrate the presence of 2nm AuNPs as single entities in the nucleus. Biofunctionalized AuNPs combined with live-cell electroporation procedures are thus potent labeling tools for the identification of macromolecules in cellular cryo-EM.

Plasmon enhanced photocatalytic degradation of 4-chlorophenol using zinc oxide nanorods decorated with gold nanoparticles as supported catalysts under natural sunlight

The photocatalytic degradation of 4-chlorophenol (4-CP) was evaluated under natural sunlight using zinc oxide nanorods (ZnO NRs) and gold nanoparticles (AuNPs) decorated ZnO NRs catalysts. Microwave-assisted hydrothermal growth of ZnO NRs followed by photoinduced deposition of AuNPs on ZnO NRs was carried out to fabricate the ZnO-Au catalysts. The photocatalytic degradation of 4-CP with different AuNPs sizes and surface coverage obtained from varying Au loading on ZnO NRs was studied. 0.1 mM AuNPs concentration exhibited the best result, with a degradation efficiency of 97% for 10 ppm of 4-CP within 180 min. The degradation enhancement for the ZnO-Au catalysts was owing to enhanced absorption in the visible region. The visible-light-induced localized surface plasmon resonance property of AuNPs reduced the recombination and promoted the electrons and holes separation. The substantial change in the binding energy of the valance band maximum exhibited the charge transfer from AuNPs to ZnO NRs. Photocatalytic degradation of four different concentrations (10, 50, 100, and 200 ppm) of 4-CP was studied. During the photocatalytic degradation, various hydroxylated intermediates formed, namely hydroquinone, benzoquinone, 4-chlorocatechol, and 4-chlororesorcinol. The photocatalytic results indicate that the ZnO-Au catalyst is a promising candidate for environmental decontamination of organic pollutants in the aqueous media.

Synthesis and characterization of polyethyleneimine/silk fibroin/gold nanoparticle nanocomposites: Potential application as a gene carrier in breast cancer cell lines

There is a need in advancing the design of non-viral gene carriers, thus herein using the pulsed laser ablation in liquid (PLAL) technique, polyethyleneimine-capped gold nanoparticles (PEI-AuNPs) were synthesized and then combined with Bombyx mori silk fibroin (SF) to form the nanocomposites (PEI-SF-AuNPs). After the characterization analyses were carried out, PEI-AuNPs and PEI-SF-AuNPs were tested for their in vitro biocompatibility in MCF-7 and MDA-MB231 breast cancer cells. Finally, the transfection capability of the selected group was observed. PEI capping enabled the cationic modification of the AuNP surface and SF reduced the surface charge (from 35 to 4 mV). PEI-AuNPs were highly monodispersed in shape and size (8–9 nm). The nanoparticle group synthesized in 5% (w/v) PEI concentration (PEI-AuNP5) had increased cytotoxicity as compared to the group synthesized in 1% (w/v) PEI concentration (PEI-AuNP1), but the conjugation of SF with PEI-AuNPs alleviated this cytotoxic tendency significantly. The group (PEI-AuNP1) with the most negligible cytotoxicity proved to be successful in the transfection of siRNA analog, i.e., siGLO green transfection indicator. Overall, the PEI-AuNP1 nanocomposites could be suggested as potent siRNA carriers due to the above beneficial properties in gene-based breast cancer therapies.

Fate of the capping agent of biologically produced gold nanoparticles and adsorption of enzymes onto their surface

Enzymotherapy based on DNase I or RNase A has often been suggested as an optional strategy for cancer treatment. The efficacy of such procedures is limited e.g. by a short half-time of the enzymes or a low rate of their internalization. The use of nanoparticles, such as gold nanoparticles (AuNPs), helps to overcome these limits. Specifically, biologically produced AuNPs represent an interesting variant here due to naturally occurring capping agents (CA) on their surface. The composition of the CA depends on the producing microorganism. CAs are responsible for the stabilization of the nanoparticles, and promote the direct linking of targeting and therapeutic molecules. This study provided proof of enzyme adsorption onto gold nanoparticles and digestion efficacy of AuNPs-adsorbed enzymes. We employed Fusarium oxysporum extract to produce AuNPs. These nanoparticles were round or polygonal with a size of about 5 nm, negative surface charge of about − 33 mV, and maximum absorption peak at 530 nm. After the adsorption of DNAse I, RNase A, or Proteinase K onto the AuNPs surface, the nanoparticles exhibited shifts in surface charge (values between − 22 and − 13 mV) and maximum absorption peak (values between 513 and 534 nm). The ability of AuNP-enzyme complexes to digest different targets was compared to enzymes alone. We found a remarkable degradation of ssDNA, and dsDNA by AuNP-DNAse I, and a modest degradation of ssRNA by AuNP-RNase A. The presence of particular enzymes on the AuNP surface was proved by liquid chromatography–mass spectrometry (LC–MS). Using SDS-PAGE electrophoresis, we detected a remarkable digestion of collagen type I and fibrinogen by AuNP-proteinase K complexes. We concluded that the biologically produced AuNPs directly bound DNase I, RNase A, and proteinase K while preserving their ability to digest specific targets. Therefore, according to our results, AuNPs can be used as effective enzyme carriers and the AuNP-enzyme conjugates can be effective tools for enzymotherapy.

Promoting effect of trace amount of Pd for p-CNB hydrogenation in Pd-Au/TiO2 bimetallic catalyst

Pd-Au bimetallic catalysts supported on TiO2 with traces of Pd for p-chloronitrobenzene (p-CNB) hydrogenation were prepared by the deposition-precipitation method. It is found that the ultra-low loading of Pd can improve significantly the catalytic activities of Pd-Au/TiO2 bimetallic catalyst compared with Au/TiO2. The minimal loading of Pd favors the Au dispersion and leads the Au NPs with small size. The existence of a large number of Au/Pd interfaces and the interaction between Au and Pd make Au NPs surface electron-enriched (Auδ-) and the Pd positively charged (Pdn+). The synergetic effect of Auδ-, Pdn+, and Pd0 improves the catalytic performance of 0.01 %Pd-0.5 %Au/TiO2. For 0.01 %Pd-0.5 %Au/TiO2, the p-CNB conversion is 99.9 %, with p-CAN selectivity of 98.6 %. After eight circles of reuse, the conversion of p-CNB and the selectivity of p-CAN is still as high as 98.18 and 99.97 %, respectively, indicating the good stability of 0.01 %Pd-0.5 %Au/TiO2. Through twenty times scale-up preparation or after sixty days of storage, our catalysts still maintain excellent catalytic performance in p-CNB reduction, demonstrating the promising prospects of 0.01 %Pd-0.5 %Au/TiO2 for industrial applications. This work offers a facile method to design bimetallic noble metal catalysts with excellent catalytic activities and good reusability, and clarifies their potential applications in industry.

Facile generation of surface diversity in gold nanoparticles

Surface chemistry is a key determinant of the physico-chemical and biological properties of gold nanoparticles (AuNPs). The introduction of chemical diversity in the surface of AuNPs is usually accomplished by place-exchange reactions using incoming ligands containing the desired terminal functional groups. As an alternative approach, we present here a simple, practical methodology to modify the surface of gold nanoparticles that allows the preparation of AuNPs stabilized with polyethyleneglycol (PEG) ligands with different surface chemistries using AuNPs stabilized with thiol-PEG-amino ligands as starting material. The surface modification reaction involves the acylation of the terminal amino groups in the ligand with an organic acid anhydride in an aqueous buffer. In addition to a full surface modification, this method also allows the synthesis of AuNPs with tailored mixed surfaces, containing two or more different functional groups, each of them at the desired extent. The ease of the experimental conditions for the reaction, purification, and for determining the level of surface modification makes this strategy an attractive alternative to current methods for the preparation of AuNPs with diverse surface chemistry.

Controlled Temporal Release of Serum Albumin Immobilized on Gold Nanoparticles.

Proteins adsorbed to gold nanoparticles (AuNPs) form bioconjugates and are critical to many emerging technologies for drug delivery, diagnostics, therapies, and other biomedical applications. A thorough understanding of the interaction between the immobilized protein and AuNP is essential for the bioconjugate to perform as designed. Here, we explore a correlation between the number of solvent-accessible thiol groups on a protein and the protein desorption rate from the AuNP surface in the presence of a competing protein. The chemical modification of human serum albumin (HSA) was carried out to install additional free thiols using Traut's reagent and create a library of HSA analogues by tailoring the molar excess of the Traut's reagent. We pre-adsorbed HSA variants onto the AuNP surface, and the resulting bioconjugates were then exposed to IgG antibody, and protein exchange was monitored as a function of time. We found that the rate of HSA displacement from the AuNP correlated with the experimentally measured number of accessible free thiol groups. Additionally, bioconjugates were synthesized using thiolated analogues of bovine serum albumin (BSA) and suspended in serum as a model for a complex sample matrix. Similarly, desorption rates with serum proteins were modulated with solvent-accessible thiols on the immobilized protein. These results further highlight the key role of Au-S bonds in the formation of protein-AuNP conjugates and provide a pathway to systematically control the number of free thiols on a protein, enabling the controlled release of protein from the surface of AuNP.

Anchoring Au on UiO-66 surface with thioglycolic acid for simultaneous SERS detection of paraquat and diquat residues in cabbage

SERS sensors based on metal-organic frameworks (MOFs) have garnered considerable attention in trace pesticide residue detection. UiO-66/AuNPs suspension substrates were fabricated by introducing thioglycolic acid (TGA) as a binder to modify the surface of AuNPs to facilitate their electrostatic assembly with UiO-66 prepared through hydrothermal reaction. The proposed substrates were used for quantitative and simultaneous analysis of paraquat and diquat in cabbage. Diquat and paraquat in actual cabbage samples were individually analysed with detection of limits (LOD) of 6 μg/L and 3 μg/L, respectively, and validated with recoveries ranging from 92.65 to 118.34%. Furthermore, the UiO-66/AuNPs substrate was able to differentiate between paraquat and diquat mixtures, even for the concentrations in the cabbage extracts differed by a factor of 100. The proposed UiO-66/AuNPs substrate provides a potentially useful tool for the trace determination of pesticide residues in the practical food safety analysis

Fabrication of Gold Nanoparticles and Cinnamaldehyde-Functionalized Paper-Based Films and Their Antimicrobial Activities against White Film-Forming Yeasts.

During storage and fermentation of kimchi, white film-forming yeasts (WFY) are generated on the surface of kimchi under various conditions. These yeasts include Candida sake, Pichia kudriavzevii, Kazachstania servazzii, Debaryomyces hansenii, and Hanseniaspora uvarum. Because of the off-odor and texture-softening properties of WFY that degrade the quality of kimchi, a method to prevent WFY is required. In this study, cinnamaldehyde (CIN) and gold nanoparticles (AuNPs) with a large surface area were grafted on a paper surface, which was termed the "Paper_AuNPs_CIN" film. CIN is an antimicrobial agent that is approved for use in food applications. In the as-fabricated Paper_AuNPs_CIN film, antimicrobial CIN molecules were physically adsorbed to the surface of AuNPs and simultaneously chemically synthesized on the paper surface via the imine reaction. The Paper_AuNPs_CIN film exhibited greater antimicrobial activity against the three WFY strains than a Paper_CIN film (which contains only CIN molecules). Since more CIN molecules were adsorbed to the large surface area of the paper-reduced AuNPs, the Paper_AuNPs_CIN film exhibited a higher antimicrobial activity. Using AuNPs and CIN simultaneously to inhibit the growth of WFY is a novel approach that has not yet been reported. The morphology and elemental mapping of the functionalized films were examined via scanning electron microscopy and energy-dispersive spectroscopy, elemental composition was analyzed via inductively coupled plasma optical emission spectroscopy, and chemical bonding and optical properties were investigated via Fourier transform infrared spectroscopy and diffuse reflectance spectroscopy. Additionally, agar-well diffusion assays were used to determine the antimicrobial activity against three representative WFY strains: C. sake, P. kudriavzevii, and K. servazzii.

Aptamer-based detection of serotonin based on the rapid in situ synthesis of colorimetric gold nanoparticles

Abstract Serotonin, a neurotransmitter that affects brain function, is associated with cancer progression, thus making it a potential biomarker. Despite the increasing efforts and ideas for gold nanoparticle (AuNP)-based colorimetric detection over the years, preparing AuNPs and sensing targets are separate processes, and this incurs more time to operate and produces excess waste. Herein, we report a simple, sensitive, and rapid colorimetric detection method for serotonin based on the in situ formation of AuNP. When only the aptamer is present, it can prevent chloride-induced aggregation of AuNPs because it easily binds to the freshly synthesized AuNPs through its exposed bases to increase the positive charge of the AuNP surfaces. When a complex of serotonin and its aptamer is formed, this complex disturbs the adsorption between aptamers and AuNPs, resulting in reduced stability of AuNPs and easy aggregation of nanoparticles. Therefore, serotonin was measured by color change, consistent with the change in peak intensity in the UV-vis absorption spectrum. The sensor demonstrated good sensitivity with a detection limit of 1 ng/mL (5.7 nM) for serotonin, which is comparable to or better than that of other aptamer-based colorimetric detection methods, further exhibiting the requisite selectivity against possible interferents. These results serve as a basis for developing other biosensors using aptamer-mediated in situ growth of AuNPs.

Photothermal-Enhanced Modulation of Cellular Membrane Potential Using Long-Wavelength-Activated Gold Nanoflowers.

In mammalian cells, plasma membrane potential plays vital roles in both physiology and pathology and it is controlled by a network of membrane-resident ion channels. There is considerable interest in the use of nanoparticles (NPs) to control biological functions, including the modulation of membrane potential. The photoexcitation of gold NPs (AuNPs) tethered close to the plasma membrane has been shown to induce membrane depolarization via localized heating of the AuNP surface coupled with the opening of voltage-gated sodium channels. Previous work has employed spherical AuNPs (AuNS) with absorption in the 500-600 nm range for this purpose. However, AuNP materials with absorption at longer wavelengths [e.g., near-infrared (NIR)] would enable greater tissue penetration depth in vivo. We show here the use of new anisotropic-shaped AuNPs [gold nanoflowers (AuNFs)] with broad absorption spanning into the NIR part of the spectrum (∼650-1000 nm). The AuNFs are directly synthesized with bidentate thiolate ligands, which preserves the AuNF's shape and colloidal stability, while facilitating conjugation to biomolecules. We describe the characterization of the AuNF particles and demonstrate that they adhere to the plasma membrane when bioconjugated to PEGylated cholesterol (PEG-Chol) moieties. The AuNF-PEG-Chol mediated the depolarization of rat adrenal medulla pheochromocytoma (PC-12) neuron-like cells more effectively than AuNS-PEG-Chol and unconjugated AuNS and AuNF when photoexcited at ∼561 or ∼640 nm. Importantly, AuNF induction of depolarization had no impact on cellular viability. This work demonstrates anisotropic AuNFs as an enabling nanomaterial for use in cellular depolarization and the spatiotemporal control of cellular activity.

Polydopamine-coated i-motif DNA/Gold nanoplatforms for synergistic photothermal-chemotherapy

The combination of photothermal therapy with chemotherapy has gradually developed into promising cancer therapy. Here, a synergistic photothermal-chemotherapy nanoplatform based on polydopamine (PDA)-coated gold nanoparticles (AuNPs) were facilely achieved via the in situ polymerization of dopamine (DA) on the surface of AuNPs. This nanoplatform exhibited augmented photothermal conversion efficiency and enhanced colloidal stability in comparison with uncoated PDA shell AuNPs. The i-motif DNA nanostructure was assembled on PDA-coated AuNPs, which could be transformed into a C-quadruplex structure under an acidic environment, showing a characteristic pH response. The PDA shell served as a linker between the AuNPs and the i-motif DNA nanostructure. To enhance the specific cellular uptake, the AS1411 aptamer was introduced to the DNA nanostructure employed as a targeting ligand. In addition, Dox-loaded NPs (DAu@PDA-AS141) showed the pH/photothermal-responsive release of Dox. The photothermal effect of DAu@PDA-AS141 elicited excellent photothermal performance and efficient cancer cell inhibition under 808 nm near-infrared (NIR) irradiation. Overall, these results demonstrate that the DAu@PDA-AS141 nanoplatform shows great potential in synergistic photothermal-chemotherapy.

SOD-Functionalized gold nanoparticles as ROS scavenger and CT contrast agent for protection and imaging tracking of mesenchymal stem cells in Idiopathic pulmonary fibrosis treatment

Development of functionalized nanoplatforms to simultaneously facilitate imaging tracking of transplanted stem cells and enhance their therapeutic efficacy through weakening oxidative stress damage has been a challenge in stem cell-based therapy. Herein, superoxide dismutase (SOD)-engineered gold nanoparticles (AuNPs), SOD@Au NS, was developed for collectively acting as a reactive oxygen species (ROS) scavenger and a computed tomography (CT) contrast agent for simultaneous protection and imaging tracking of mesenchymal stem cells (MSCs) in idiopathic pulmonary fibrosis (IPF) therapy. In this strategy, SOD, a key antioxidant enzyme that detoxifies intracellular ROS, was modified on the surface of AuNPs and then encapsulated into polyphosphazene nanospheres to overcome the poor cell membrane penetration and chemical stability of SOD, thereby promoting the survival of MSCs in a harsh inflammatory microenvironment by ROS elimination. What’s more, SOD@Au NS where the assembly of an AuNP payload in a polyphosphazene core provides strong contrast enhancement in CT imaging owing to the dense packing of AuNP. After cellular uptake of SOD@Au NS, the labeled MSCs could be detected by CT technology, achieving continuous monitoring of the distribution and migration of MSCs for 18 days after transplantation in the IPF model mouse. Furthermore, we evaluated the long-term metabolism and safety of SOD@Au NS following transplantation of the stem cells into the alveolar interstitium. Consequently, this work may provide a novel insight into the development of safe and effective strategies to trace and protect transplanted stem cells, thus facilitating the subsequent preclinical research and clinical translation of stem cell-based IPF treatment.

Localized formation of highly surface-active gold nanoparticle on intrinsic Nickel containing carbon black and its scanning electrochemical microscopy interrogation and electrocatalytic oxidation of hydrazine

Gold nanoparticles (AuNPs) anchored carbon-nanomaterial chemically modified electrodes have been widely used for electrocatalytic applications. Indeed, only a fraction of AuNPs surface is found to be active, while most of the surface is inactive in nature. Thus, it is a challenging research to prepare active AuNPs suitable for electrocatalytic applications. Herein, we present a low-cost intrinsic nickel-containing carbon black (CB-Niint, int= intrinsic nickel) modified glassy carbon electrode as an efficient matrix for forming highly active AuNPs (GCE/CB-Niint@AuNPs). Specific electrocatalytic oxidation of hydrazine has been used as a model system to compare the active sites of the AuNPs. Various carbon nanomaterials like SWCNT, MWCNT, carbon nanofiber, and graphite nanopower-modified electrodes and externally deposited Ni (Niext) on the carbon-modified electrodes were examined as controls for the AuNPs formation and hydrazine electrocatalytic activity. Amongst all, the CB-Niint matrix-modified electrode has shown the best electrocatalytic activity. The GCE/CB-Niint@AuNPs was subjected to various physicochemical characterizations like FESEM, TEM, Raman, IR, XPS, and scanning electrochemical microscopy (SECM) using a Eu3+/2+ redox probe. Meanwhile, with Fe(CN)63−, ex-situ derivatization of Niext as Ni-hexacyanoferrate, CB@Niext-HCF, was specifically inferred. It has been revealed that AuNPs form an intrinsic Au-Niint alloy system on the interstitial position of CB-Niint. On the other hand, a bulk layer-like AuNPs morphology was observed with the CB-Niext modified electrode case. This unique structural feature of the CB-Niint@AuNPs sets a new trend in AuNPs-based chemically modified electrode preparation and electrochemical applications. As a proof of concept, selective electrochemical sensor application of hydrazine with a current sensitivity of 4.37 mA mM−1 cm−2, which is about 5-10 times higher than the majority of the conventional AuNPs-modified electrodes, without any common interference from H2O2, uric acid, ascorbic acid, dopamine, and cysteine, was demonstrated.

Flexible biosensor based on signal amplification of gold nanoparticles-composite flower clusters for glucose detection in sweat

Flexible non-invasive glucose monitoring sensor addresses the limitations of intermittent detection and provides the opportunity for optimal therapeutic interventions. However, the low sensitivity of non-invasive sensors restricted their wide applications. In this study, a facile and versatile three-dimensional flexible glucose sensor based on nano-material signal amplification through the structural design and surface modification of sensing electrodes was constructed. Tannic acid-3-aminopropyltriethoxysilane (TA-APTES) coatings were prepared on the activated carbon cloth (aCC) via Michael addition and Schiff base reactions, followed by in situ reductions of gold nanoparticles (AuNPs) to yield AuNPs/TA-APTES/aCC electrodes. Subsequently, glucose oxidases (GOx) were immobilized at the surface of AuNPs to form the sensor. The GOx AuNPs/TA-APTES/aCC sensors exhibit high sensitivity, low detection limit, and fast response rate. The advantage of the GOx AuNPs/TA-APTES/aCC sensors is further illustrated by the excellent stability and the performance in sweat samples with complex components. The design concept of the GOx AuNPs/TA-APTES/aCC for flexible biosensors could potentially drive the development of flexible skin-mountable sensors for monitoring glucose in biofluids.

Preparation and Evaluation of 64Cu-Radiolabled Dual-Ligand Multifunctional Gold Nanoparticles for Tumor Theragnosis.

Gold nanoparticles (AuNPs) are cutting-edge platforms for combined diagnostic and therapeutic approaches due to their exquisite physicochemical and optical properties. Using the AuNPs physically produced by femtosecond pulsed laser ablation of bulk Au in deionized water, with a capping agent-free surface, the conjugation of functional ligands onto the AuNPs can be tunable between 0% and 100% coverage. By taking advantage of this property, AuNPs functionalized by two different types of active targeting ligands with predetermined ratios were fabricated. The quantitatively controllable conjugation to construct a mixed monolayer of multiple biological molecules at a certain ratio onto the surface of AuNPs was achieved and a chelator-free 64Cu-labeling method was developed. We report here the manufacture, radiosynthesis and bioevaluation of three different types of dual-ligand AuNPs functionalized with two distinct ligands selected from glucose, arginine-glycine-aspartate (RGD) peptide, and methotrexate (MTX) for tumor theragnosis. The preclinical evaluation demonstrated that tumor uptakes and retention of two components AuNP conjugates were higher than that of single-component AuNP conjugates. Notably, the glucose/MT- modified dual-ligand AuNP conjugates showed significant improvement in tumor uptake and retention. The novel nanoconjugates prepared in this study make it possible to integrate several modalities with a single AuNP for multimodality imaging and therapy, combining the power of chemo-, thermal- and radiation therapies together.

Photothermal catalytic H2 production over hierarchical porous CaTiO3 with plasmonic gold nanoparticles

The synergistic promotion by photocatalysis and thermocatalysis is a promising approach for sustainable hydrogen (H2) production. Herein, we rationally design a perovskite-based catalyst with three-dimensionally ordered macroporous structure (3DOM CaTiO3-Au) for photothermal catalytic H2 production from different substrates. The hierarchical 3DOM structure facilitates light harvesting and mass diffusion of the substrates, while the gold nanoparticles (Au NPs) promote charge separation. The photogenerated and hot electrons are oriented accumulated on the surface of Au NPs. The non-metallic gold species [Au(I)] show more activity for H2 evolution. As a result, 3DOM CaTiO3-Au exhibits excellent activity for H2 production from glycerol and other substrates with hydroxyl groups. The present work demonstrates a feasible approach to improve sustainable H2 production by rationally designing and fabricating efficient photothermal catalysts.

An inner filter effect-based fluorescent aptasensor for sensitive detection of kanamycin in complex samples using gold nanoparticles and graphene oxide quantum dots.

In this work, a label-free fluorescent aptasensor based on the inner filter effect (IFE) between gold nanoparticles (AuNPs) and graphene oxide quantum dots (GOQDs) was developed for the detection of kanamycin in complex samples. AuNPs are capable of functioning as the fluorescence absorber of GOQDs because of the complementary overlap between their absorption spectra and the emission spectra of GOQDs. AuNPs can effectively quench the fluorescence of GOQDs via the IFE and modulate it with their aggregation state. In the presence of kanamycin, the aptamer is released from the surface of AuNPs, leading to their salt-induced aggregation and the fluorescence recovery of GOQDs. Under the optimum conditions, the fluorescence intensity of GOQDs was linearly proportional to the concentration of kanamycin over the range from 5 to 600 nM, with a detection limit of 3.6 nM. Moreover, the fluorescent aptasensor was successfully applied for kanamycin detection in complex samples (milk, honey and serum), which might hold great promise for kanamycin detection in food safety control and clinical research.

Sensitive detection of microRNA by dynamic light scattering based on DNAzyme walker-mediated AuNPs self-assembly.

As an important biomarker, microRNAs (miRNAs) play an important role in gene expression, and their detection has attracted increasing attention. In this study, a DNAzyme walker that could provide power to perform autonomous movement was designed. Based on the continuous mechanical motion characteristics of DNAzyme walker, a miRNA detection strategy for the self-assembly of AuNPs induced by the hairpin probe-guided DNAzyme walker "enzyme cleavage and walk" was established. In this strategy, DNAzyme walker continuously cleaved and walked on the hairpin probe on the surface of AuNPs to induce the continuous shedding of some segments of the hairpin probe. The remaining hairpin sequences on the surface of the AuNP pair with each other, causing the nanoparticles to self-assemble. This strategy uses the autonomous movement mechanism of DNAzyme walker to improve reaction efficiency and avoid the problem of using expensive and easily degradable proteases. Secondly, using dynamic light scattering technology as the signal output system, ultra-sensitive detection with a detection limit of 3.6 fM is achieved. In addition, this strategy has been successfully used to analyze target miRNAs in cancer cell samples.