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Ge photodiodes with ultra-high responsivities have been demonstrated with gold nanoparticle assistance. The responsivity can reach a value of 37.7 A/W, which corresponds to a gain of 76. Such a high responsivity originates from the amassment of photo-generated holes in Ge under the boundary of gold nanoparticles, which reduces the barrier for electron tunneling from metal to the hole-amassment Ge ring areas. The depletion layer thinning due to hole amassment is not only proved by band diagram simulation but also confirmed by capacitance measurement.

A capacitive biosensor for the detection of protein A was developed. Gold electrodes were fabricated by thermal evaporation and patterned by photoresist photolithography. A layer-by-layer (LbL) assembly of thiourea (TU) and HAuCl4 and chemical reduction was utilized to prepare a probe with a different number of layers of TU and gold nanoparticles (AuNPs). The LbL-modified electrodes were used for the immobilization of human IgG. The binding interaction between human IgG and protein A was detected as a decrease in capacitance signal, and that change was used to investigate the correlation between the height of the LbL probe and the sensitivity of the capacitive measurement. The results showed that the initial increase in length of the LbL probe can enhance the amount of immobilized human IgG, leading to a more sensitive assay. However, with thicker LbL layers, a reduction of the sensitivity of the measurement was registered. The performance of the developed system under optimum set-up showed a linearity in response from 1 × 10−16 to 1 × 10−13 M, with the limit detection of 9.1 × 10−17 M, which could be interesting for the detection of trace amounts of protein A from affinity isolation of therapeutic monoclonal antibodies.

The development of powerful techniques for sensitive detection of nucleic acids has attracted much attention for fabricating accurate biosensors in various fields, such as genomics, clinical diagnostics, and forensic sciences. Up to now, different systems have been introduced, the majority of which are expensive, time-consuming, and relatively low selectivity/limit of detection. These limitations caught our attention to fabricate a nucleic acid responsive system by combining three layers of signal amplification strategy, namely a split proximity circuit (SPC), a catalytic hairpin assembly (CHA), and a DNA hydrogel. Herein, by SPC operation, two initiators and a target strand were assembled and activated the CHA reaction in the presence of three 5′-cytosine (C)-rich hairpins. Then, produced C-rich embedded three-way junction structures could form i-motif structures under acidic environment followed by a transition from sol to gel state. To acquire a quantitative and colorimetric measurement, gold nanoparticles (GNPs) were used that encapsulated and sediment by the gel formation. The resulting platform detected the target with a limit of detection of 1 pM and considerable selectivity. Image 1 • DNA nanotechnology has sparked the construction of the many nanostructures in biosensing platform. • The present study enabled fabrication of a colorimetric nucleic acid responsive biosensor via LOD as low as 1 pM. • Three amplification strategies are implemented in this assay, namely SPC, CHA, and DNA hydrogel that provide high sensitivity and selectivity. • Monitoring of various targets, such as nucleic acid, metabolites, cancer cells, and sites of infection can be considered for this assay. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the ability of the haloarchaeon Haloferax volcanii to produce Ag and Au nanoparticles (NPs) and to characterize the obtained material in order to find relevant properties for future potential applications. Methods and Results: Nanoparticles were produced by incubating H. volcanii cells with the corresponding metal salt. In the presence of precursor salts, cultures evidenced a colour change associated to the formation of metallic nanostructures with plasmonic bands located in the visible range of the spectrum. X-ray fluorescence analysis confirmed the presence of Ag and Au in the NPs which were spherical, with average sizes of 25 nmol l-1 (Ag) and 10 nmol l-1 (Au), as determined by electronic microscopy. Fourier transformed infrared spectroscopy indicated that both types of NPs showed a stable protein capping. Ag NPs evidenced antibacterial activity and Au NPs improved the specificity of polymerase chain reaction reactions. Au and Ag NPs were able to reduce 4-nitrophenol when incubated with NaBH4. Conclusions: Haloferax volcanii is able to synthesize metallic NPs with interesting properties for technological applications. Significance and Impact of the Study: Our data demonstrate the ability of H. volcanii to synthesize metal NPs and constitutes a solid starting point to deepen the study and explore novel applications. [ABSTRACT FROM AUTHOR]

Understanding the energy transfer dynamics in fluorescein-gold nanoparticle systems is crucial for future optoelectronic devices based on energy transfer. Dominant energy transfer mechanisms including the dipole-dipole (FRET) and dipole-surface energy transfer (SET) are investigated. We have compared the measured performance values with the theoretical predictions for both FRET and SET models, specifically the importance of interactions between various scales. It has been shown that the highly sensitive FRET process is limited and focused on the Förster radius range (R0), while the high efficiency of the SET over longer distances provides better resolution than the FRET process. The detection and quantitation of the energy transfer mechanism might be to playing a critical role in improving spatial resolution, distance range, and spectral sensitivity for biophysical studies. Graphical abstract [ABSTRACT FROM AUTHOR]

The development of a stable nanobioconjugate based on gold nanoparticles (AuNPs) linked to single-strand DNA (ssDNA) is reported for amplification of the electrochemical signal of a Zika virus (ZIKV) genetic material-based bioassay, with high sensitivity. The genosensor was assembled either at a screen-printed gold electrode (SPAuE) or a screen-printed carbon electrode decorated with hierarchical gold nanostructures (SPCE/Au), with Ru3+ as an electrochemical reporter. The genosensor response, interrogated by differential pulse voltammetry (DPV) at the transient current density, was linear from 10 to 600 fM and from 500 fM to 10 pM of the target, with a sensitivity of 2.7 and 2.9 μA cm−2 M−1 and a limit of detection of 0.2 and 33 fM at the SPAuE and SPCE/Au, respectively. The resultant genosensor detected ZIKV genetic material in raw serum samples from infected patients, with no sample pretreatment in a polymerase chain reaction amplification-free assay. The proposed ultrasensitive nanobioconjugate-based system offers a step forward to the diagnosis of the ZIKV, closer to the patient, and holds the potential for signal amplification in biosensing of a myriad of applications. Graphical abstract [ABSTRACT FROM AUTHOR]

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Background: With the enormous increment of globalization and global warming, it is expected that the number of newly evolved infectious diseases will continue to increase. To prevent damage due to these infections, the development of a diagnostic method for detecting a virus with high sensitivity in a short time is highly desired. In this study, we have developed a disposable electrode with high-sensitivity and accuracy to evaluate its performances for several target viruses. Results: Conductive silicon rubber (CSR) was used to fabricate a disposable sensing matrix composed of nitrogen and sulfur-co-doped graphene quantum dots (N,S-GQDs) and a gold-polyaniline nanocomposite (AuNP-PAni). A specific anti-white spot syndrome virus (WSSV) antibody was conjugated to the surface of this nanocomposite, which was successfully applied for the detection of WSSV over a wide linear range of concentration from 1.45 × 102 to 1.45 × 105 DNA copies/ml, with a detection limit as low as 48.4 DNA copies/ml. Conclusion: The engineered sensor electrode can retain the detection activity up to 5 weeks, to confirm its long-term stability, required for disposable sensing applications. This is the first demonstration of the detection of WSSV by a nanofabricated sensing electrode with high sensitivity, selectivity, and stability, providing as a potential diagnostic tool to monitor WSSV in the aquaculture industry. [ABSTRACT FROM AUTHOR]

In this study, for the first time in literature, an impedimetric biosensor technology was developed to determine Heat Shock Protein‐47 (HSP‐47) for the characterization of primary skin fibroblast cells. Gold nanoparticle electrodes (GNPE) were modified with amino‐functionalized graphene oxide layers and anti‐HSP‐47 were immobilized on this layer. The performance of the biosensor was tested with real samples as cell lysates. The low detection limit (LOD) and the linear detection limit (LOQ) of the biosensor were calculated as 9.47 pg/mL and 3.23 pg/mL, respectively. Linear measurement range was obtained between 10–160 pg/mL HSP‐47. The reproducibility of the biosensor was good. [ABSTRACT FROM AUTHOR]

Phototherapy is a minimally invasive oncological treatment strategy in which photon energy is delivered to the tumor tissue. Gold nanoparticles (GNPs) can enhance photothermal or photodynamic phenomena when excited by a wavelength beam in the range of UV-IR. GNPs are used in phototherapy for cancer cell treatment by controlling the physical and chemical conditions. Given the growing application of GNPs for the treatment of breast cancer, predicting the behavior of cancer cells during exposure to GNPs is of prime importance. However, the prediction might be far from reality due to the inherent complexities associated with the conditions of the treatment methods and the mechanisms involved in cell toxicity. This study provides general information by collecting data on the cytotoxicity of GNPs along with this process. Data mining was performed using a mathematical modeling method called SA-LOOCV-GRBF. In this study, eight parameters including particle size, zeta potential, concentration of GNPs in the cell culture medium, incubation time, light exposure time, maximum wavelength absorbance (MAW) of GNPs, irradiation beam wavelength (IW) and light source power density (PD) were measured. In this modeling, these parameters were considered as model inputs, and the cell viability of breast cancer cells after treatment was treated as the model output. As a result, the physical and chemical properties of GNPs as well as their application conditions wield influence on cytotoxicity. The results help select the desired condition for these nanoparticles in the phototherapy of breast cancer cells. [ABSTRACT FROM AUTHOR]

The conception and development of a new electrochemical sensor is reported for the detection of metformin (MET). Zinc ferrite and copper oxide nanostructure (ZnFe2O4-CuO) and gold nanoparticles (AuNPs) have been used to prepare a nanocomposite in modifying a glassy carbon electrode (GCE). The unique ZnFe2O4-CuO/Au nanocomposite was applied as a sensor for the determination of traces of MET by some electroanalytical techniques. Experimental parameters affecting the results were investigated and optimized. Under the optimum conditions and at a working potential of 0.85 V (vs. Ag/AgCl/3.0 M KCl), the sensor response is linear in the MET range of 1.0 nmol L−1 to 1.0 μmol L−1 MET. The limit of detection (LOD) is 0.3 nmol L−1 (at an S/N ratio of 3) and the sensitivity is 1.13 μA μmol L−1 cm−2. The sensor was applied to the determination of MET in real samples where it gave acceptable results. [ABSTRACT FROM AUTHOR]

Antibiotic resistance in Staphylococcus aureus and Pseudomonas aeruginosa has become a worldwide problem. Various types of antibiotics have been used to control these bacterial infections. However, antibiotic resistance and infection recurrence urge the need to develop new antimicrobials, instead of using the traditional antibiotics. The shortage of new antibiotics has prompted research into chemicals that could act as adjuvants and enhance the efficacy of available antibiotics. Many classes of antibiotics form complexes with metal cations, which can either enhance or hinder their activity. The aim of this study was to determine the effect of AuNPs against Pseudomonas aeruginosa sp. and Staph. aureus MRSA16. Different doses of AuNPs including four concentrations: 0.3 µg/ml, 0.6 µg/ml, 0.8µg /ml and 1 µg/ml of AuNPs were used to check antibacterial activity. Inhibition zones were studied using agar well diffusion method was used. AuNPs showed higher inhibition growth against Staph. aureus MRSA16 than P. aeruginosa, which could form the basis for future therapeutic applications. [ABSTRACT FROM AUTHOR]

We present an electrochemical sandwich‐type assay based on the splitting of an aptamer into two fragments. Gold nanoparticles are modified with one of the fragments and a redox polyelectrolyte. The first is used as the recognition element, while the other for the electrochemical signal generation. The split‐aptamer used here can detect adenosine, used as a model system for recognizing small molecules. The multiple binding sites on the nanoparticle, along with the high number of redox probes, yield a selective and sensitive assay for adenosine, achieving a limit of detection of 3.1 nM and a linear range up to 75 nM. The obtained results are analyzed in terms of the nanoparticle and electrode architectures. The assay can be easily extended to other small molecules and sandwich assays, representing a promising tool for detecting metabolites at the nanomolar level. [ABSTRACT FROM AUTHOR]

A simple and ultrasensitive flow injection chemiluminescence competitive immunoassay based on gold nanoparticle‐loaded enzyme for the detection of chloramphenicol (CAP) residues in shrimp and honey has been developed. Due to their good biocompatibility and large specific surface area, carboxylic resin beads can be used as solid phase carriers to immobilize more coating antigens (Ag). In addition, gold nanoparticles could provide an effective matrix for loading more CAP antibody and horseradish peroxidase, which would effectively catalyze the system of luminol–p‐iodophenol (PIP)–H2O2. A competitive immunoassay strategy was used for detection of CAP, in which CAP in the sample would compete with the coating Ag for the limited antibodies, leading to a chemiluminescence (CL) signal decrease with increase in CAP concentration. A wide linear range 0.001–10 ng ml−1 (R2 = 0.9961) was obtained under optimized conditions, and the detection limit (3σ) was calculated to be 0.33 pg ml−1. This method was also been successfully applied to determine CAP in shrimp and honey samples. The immunosensor proposed in this study not only has the advantages of high sensitivity, wider linear range, and satisfactory stability, but also expands the application of flow injection CL immunoassay in antibiotic detection. [ABSTRACT FROM AUTHOR]

Time–temperature indicators (TTIs) can monitor the quality and safety of food. A new temperature–time point comparison method was proposed to match TTIs with food. This method omits the step of calculating activation energy (Ea). It only compares the difference between TTI response time and food shelf life to determine their matching degree. Taking gold nanoparticle‐based TTIs and muffins as experimental objects, the new and the traditional matching methods were used to match the absorbance of TTI and the peroxide value of muffins. The two results are not significantly different. TTIs with gelatin solution and gold precursor solution concentration of 150.00 and 2.05 mg/mL, respectively, can show the quality of muffins. TTIs changed from light yellow to pink and finally appeared deep purple. The deep purple represented spoilage and inedibility of muffins. Comparing Ea of food and that of TTIs can preliminarily evaluate their matching degree, improving the experiment efficiency. Hence, it is reasonable to use the traditional matching method in most cases, and use the new method only when Ea of food cannot be obtained. Practical Application: The deterioration rate of food is usually calculated by developing kinetic models of characteristic quality parameters. When the reaction rate is unavailable or inaccurate, the activation energy of food cannot be obtained. In this case, it is impossible to match TTIs with food based on the traditional method. This research develops a new matching method and helps TTIs and food to be matched without considering activation energy. It will promote the application of TTIs in more products. [ABSTRACT FROM AUTHOR]

Prevalent contamination of water by cadmium ion (Cd2+) brings environmental risk, which threatening to human health including renal dysfunction, reduced lung capacity, and some cancers. It calls for rapid, sensitive and selective protocol to analyze Cd2+ on field. In this work, specific Raman probe is rationally designed by gold nanoparticles (AuNPs) functionalized with tripeptide glutathione (GSH) and Rhodamine 6G (R6G) (denoted as R6G/GSH/AuNPs), which is explored for indirectly determining trace Cd2+ in river water. Based on chelating interaction between GSH and Cd2+ to form tetrahedral Cd(SG) 4, which trends easy detachment from R6G/GSH/AuNPs. With increasing Cd2+ concentration, the Raman probe without protection of GSH happens due aggregation and Raman signal of R6G increases correspondingly. The R6G/GSH/AuNPs-based Raman detection of Cd2+ in river water shows rapidness, excellent sensitivity, selectivity and good repeatability. Limit of detection of 10 ppb with a widely linear range of 0.5–20 ppm could be achieved. It could be perspective that such Raman probe could be extended to be used for on-site monitoring trace Cd2+ in river water system. [ABSTRACT FROM AUTHOR]

Objectives: Granulosa cells are associated with steroidogenesis and ovarian function in females. Aims of the study are to understand the effects of gold nanoparticles (AuNP) on steroidogenesis and apoptotic pathway associated genes in buffalo granulosa cells. Results: The AuNP were prepared chemically and thereby characterized by transmission electron microscope (TEM) imaging, absorbance and dynamic light scattering (DLS) measurements for hydrodynamic diameter and zeta potential. The cultured buffalo granulosa cells (BGC) were co-incubated with AuNP in two concentrations (2 × 109 and 2 × 1010 AuNP/ml) for 24 h. Treatment of BGC with AuNP significantly modulated the steroidogenesis associated genes (3β-Hsd and Cyp19A1) expression and progesterone accumulation in the culture fluid. AuNP affected the apoptotic pathway in BGC by affecting the gene expression of Caspase-3, Bad and Bax. The AuNP did not exert oxidative stress through anti-oxidant induction & lipid peroxidation in the buffalo GC. Conclusions: AuNP may modulate the endocrine system by having impact on the steroidogenesis pathway and also have the potential to affect apoptotic pathway in a buffalo granulosa cell model. [ABSTRACT FROM AUTHOR]

• Banana peel and derivatives showed great potentials for gold recovery. • Lipid elimination boosted the adsorption capacity and selectivity. • Lipid-free biomass exhibited pH-dependent nanoparticle formation property. • High-purity metallic gold (>99%) was obtained via adsorption-incineration. In this study, banana peel (BP) and its derivatives after sequential extraction of biochemical components were evaluated for selective recovery of gold. In-depth instrumental characterizations including XPS, FTIR, XRD and HR-TEM were performed to understand the adsorption mechanisms. The biomass after lipid extraction, BP-L, demonstrated very good affinity and selectivity towards gold. In multi-metal systems containing 100 mg/L of Pt(IV), Au(III), Pd(II), Zn(II), Co(II), Ni(II) and Li(I), the selectivity coefficient increased from 978.45 in BP to 2034.70 in BP-L. Moreover, the equilibrium gold uptake was improved and reached 475.48 ± 3.08 mg/g owing to reduction-coupled adsorption mechanisms. The BP-L also showed improved gold nanoparticle formation properties that were pH-dependent. In a strategic adsorption-combined incineration process, metallic gold reaching 99.96% in purity was obtained. The BP and its derivative, BP-L have thus shown potentials for multiple applications in the areas of precious metal recovery and nanoscience. [ABSTRACT FROM AUTHOR]

An electrochemical sensor for amoxicillin (AMX) detection based on reduced graphene oxide (RGO), molecular imprinted overoxidized polypyrrole (MIOPPy) modified with gold nanoparticles (AuNPs) is described in this work. The electrochemical behavior of the imprinted and non‐imprinted polymer (NIP) was carried out by cyclic voltammetry (CV) and impedance spectroscopy (IS). The structure and morphology of the prepared MIP sensor were characterized by scanning electron microscopy (SEM), UV‐Visible, Fourier transform infrared spectroscopy (FTIR) and its experimental parameters such as monomer and template concentration, pH buffer solution, incubation time of AMX and AuNPs, scan rate as well as electropolymerization scan cycles were optimized to improve the performance of the sensor. The peak current obtained at the MIP electrode was proportional to the AMX concentration in the range from 10−8 to 10−3 mol L−1 with a detection limit and sensitivity of 1.22 10−6 mol L−1 (Signal to noise ratio=3) and 2.52×10−6 μAmol−1 L, respectively. It was also found that this sensor exhibited reproducibility and excellent selectivity against molecules with similar chemical structures. Besides, the analytical application of the AMX sensor confirms the feasibility of AMX detection in milk and human serum. [ABSTRACT FROM AUTHOR]

According to the American Cancer Society, colorectal cancer remains one of the leading cause of cancer death in the US. It is an urgent need to explore new strategies to combat colorectal cancer. Hence, the current study was aimed to systematically review the original published articles to assess the efficacy of biogenic gold nanoparticles (AuNPs) against colorectal cancer cells for the first time. The electronic databases involving Cochrane, Web of Science, ProQuest, PubMed, Embase, Scopus, and Science Direct were searched for the articles published up to 19 June 2019. Different natural sources including bacterium, alga, plant, and fungus were applied for bioreduction of AuNPs. Besides, most of the studies reported the size distribution of AuNPs less than 50 nm with different morphologies. However, most of the studies reported spherical shaped AuNPs. This study revealed that although several studies reported less toxicity of biogenic AuNPs, most of studies represented significant anticancer activity of biogenic AuNPs against colorectal cancer cells through in vitro model. We provided strong preliminary evidence indicating the considerable anticancer potential of biogenic AuNPs against colorectal cancer cells. Future studies should be conducted on in vivo efficacy of biogenic AuNPs against colorectal cancer cells. [ABSTRACT FROM AUTHOR]

An enzyme-free dual catalytic DNA circuit for amplified detection of nucleic acids has been developed. The system functions based on a cyclic self-assembly of two auxiliary hairpins (H1 and H2) and three biotinylated hairpin oligonucleotides (H3, H4 and H5), in the format of two molecular circuits. In the upstream circuit, a target initiator (I) besides H1 and H2 hairpins constructs H1-H2 duplexes that trigger the operation of a subsequent circuit. In the downstream circuit, the H1-H2 duplex initiates cascaded self-assembly reactions, produces triplex H3-H4-H5, as sensing system, and releases the H1-H2 duplex as the catalyst for the self-assembly of additional hairpins. The H3-H4-H5 triplex acts as the scaffolds for assembling and orienting the streptavidin-functionalized gold nanoparticles (SA-AuNPs) into a lattice-like arrangement that generates a DNA-SA-AuNP cross-linked network, resulting in a dramatic pale red-to-blue color change. By ingeniously engaging two catalytic circuits with feedback amplification capabilities, the system can detect the target nucleic acid with an LOD value of 5 femtomolar and unambiguously discriminate spurious targets (i.e. targets containing substitution, insertion, and deletion nucleotides) without instrumentation. Simple and convenient operation of the assay makes the DNA circuit appropriate for point-of-care monitoring in resource-constrained settings. [ABSTRACT FROM AUTHOR]

Plasmonic nanoparticles (NPs) adsorbing onto helical bacteria can lead to formation of NP helicoids with micron scale pitch. Associated chiroptical effects can be utilized as bioanalytical tool for bacterial detection and better understanding of the spectral behavior of helical self‐assembled structures with different scales. Here, we report that enantiomerically pure helices with micron scale of chirality can be assembled on Campylobacter jejuni, a helical bacterium known for severe stomach infections. These organisms have right‐handed helical shapes with a pitch of 1–2 microns and can serve as versatile templates for a variety of NPs. The bacteria itself shows no observable rotatory activity in the visible, red, and near‐IR ranges of electromagnetic spectrum. The bacterial dispersion acquires chiroptical activity at 500–750 nm upon plasmonic functionalization with Au NPs. Finite‐difference time‐domain simulations confirmed the attribution of the chiroptical activity to the helical assembly of gold nanoparticles. The position of the circular dichroism peaks observed for these chiral structures overlaps with those obtained before for Au NPs and their constructs with molecular and nanoscale chirality. This work provides an experimental and computational pathway to utilize chiroplasmonic particles assembled on bacteria for bioanalytical purposes. [ABSTRACT FROM AUTHOR]

A novel optical immunosensor for the screening of ampicillin (Amp) residues has been developed. The biosensor is based on fiber optic particle plasmon resonance detection and uses an enhancement method called as fiber optic nanogold-linked immunosorbent assay (FONLISA) for the sensitive detection of antibiotics. A commercial antibody which had a higher affinity for ampicillin than for other β-lactam antibiotics was chosen. A surface competitive binding assay was used in which a fixed concentration of antibiotic-conjugated gold nanoparticles (AuNPs) competes with free unlabeled antibiotic molecules to measure the amount of binding with antibody molecules immobilized on an optical fiber. The synthesis of the 11-mercaptoundecanoic acid (MUA)-ampicillin conjugate facilitates the attachment of the Amp molecules to AuNPs via MUA which acts as a linker between them. This AuNP–Amp conjugate was then used for the detection of β-lactam antibiotics. The practical limit of detection obtained for Amp was 0.74 ppb (7.4 × 10−10 g/mL) which is lower than the recommended maximum residue limit (MRL) for β-lactams. The method also shows a wide linear range of 4 orders. Its applicability to the determination of ampicillin in spiked milk samples has been demonstrated with good recovery and reproducibility. [ABSTRACT FROM AUTHOR]

Pharmacotherapy and imaging are two critical facets of cancer therapy. Carbon nanotubes and their modified species such as magnetic or gold nanoparticle conjugated ones they have been introduced as good candidates for both purposes. Gold nanoparticles enhance effects of X-rays during radiotherapy. Nanomaterial-mediated radiofrequency (RF) hyperthermia refers to using RF to heat tumors treated with nanomaterials for cancer therapy. The combination of hyperthermia and radiotherapy, synergistically, causes a significant reduction in X-ray doses. The present study was conducted to investigate the ability and efficiency of the multi-walled carbon nanotubes functionalized with magnetic Fe3O4 and gold nanoparticles (mf-MWCNT/AuNPs) for imaging and cancer therapy. The mf-MWCNT/AuNPs were utilized for imaging approaches such as ultrasounds, CT scan, and MRI. They were also examined in thermotherapy and radiotherapy. The MCF-7 cell line was used as an in vitro model to study thermotherapy and radiotherapy. The mf-MWCNT/AuNPs are beneficial as a contrast agent in imaging by ultrasounds, CT scan, and MRI. They are also radio waves and X-rays absorbent and enhance the efficiency of thermotherapy and radiotherapy in the elimination of cancer cells. The valuable properties of mf-MWCNT/AuNPs in radio- and thermotherapies and imaging strategies make them a good candidate as a multimodal tool in cancer therapy. [ABSTRACT FROM AUTHOR]

Purpose: The tools to trigger dendritic cell (DC) activation and to verify DC migration in vivo are important for directing DC immunotherapy toward successful treatment. We evaluated whether tumor cell-derived exosome (TEX)-stimulated DC migration into lymph node (LN) in mouse could be tracked using gold nanoparticle (GN)-labeling and ultrasound (US)-guided photoacoustic imaging (PAI).Procedures: GFP-transduced DC2.4 cells were used. RFP-tagged TEXs were purified from a stable 4T1 cell line overexpressing the exosomal CD63-RFP fusion protein. The TEX uptake by DCs was visualized using confocal laser scanning microscopy. GNs with surface plasmon resonance at 808 nm were used for DC-labeling. DCs that migrated into axillary LN were longitudinally monitored by US-guided PAI and analyzed by silver staining and immunohistochemistry.Results: TEXs were easily internalized in DCs, increased proliferation and migration capacities, and upregulated co-stimulatory molecules, CCR7 and TNF-α without cytotoxicity. The GN-labeling exerted no adverse effects on the biological functions of DCs. US-guided PAI and DC-labeling allowed for sensitive and longitudinal monitoring of TEX-stimulated DC migration toaxillary LN.Conclusions: TEXs efficiently activated DCs and GN-labeled DC migration into LN was successfully monitored using US-guided PAI, suggesting that TEXs are a good source for DC activation and US-guided PAI is a cost-effective and easy-to-use imaging modality for noninvasive tracking of DCs. [ABSTRACT FROM AUTHOR]

In the present study, pectin‐coated gold nanoparticles (GNPs) were used as a candidate for curcumin drug delivery. The effect of the size of synthesized GNPs was examined, as an important factor on the yield of drug delivery. For this purpose, three different sizes of GNPs were first synthesized using a chemical method. The synthesized nanoparticles were then coated with pectin biopolymer. Finally, curcumin drug was loaded in a pectin@GNPs complex. Various methods such as UV–vis spectrophotometry, dynamic light scattering, scanning electron microscopy and Fourier‐transform infrared spectroscopy were used to characterize the synthesized GNPs and pectin@GNPs. The encapsulation efficiency and the release percentage of the drug were calculated for two different pH values. Further, an antibacterial study was conducted. The results revealed that 100 nm GNPs had the highest encapsulation efficiency. An investigation of the release rate of curcumin drug at 37°C for 48 h indicated that the amount of drug released was higher in acidic pH than at pH 7.4 with a slow release rate. The electronic structure and the adsorption properties of pectin–GNPs complex were examined using the density functional theory method. [ABSTRACT FROM AUTHOR]

Ligand exchange was triggered at toluene/water emulsion interface between homogeneous gold nanoparticles (Au NPs) with triphenylphosphine (PPh3) and D-penicillamine (D-PA), resulted in amphiphilic Janus Au NPs with both phosphine and thiolate ligands. TEM and XRD analyses indicate that the product is composed of Au nanocrystals in an average diameter of about 3.7 nm. XPS, FTIR, Raman, and 1H NMR analyses demonstrate that the Au NPs are protected with hydrophilic D-PA molecules and lipophilic PPh3 ligands in a molecular ratio of ca. 1.8. The NOESY analysis and contact angle measurement further suggest that the D-PA and PPh3 molecules are spontaneously separated to form compartmentalized hydrophilic and lipophilic regions on the individual Au NPs, which exhibit good catalytic performance and recyclability on the reduction of 4-nitrophenol. The results demonstrate that amphiphilic Janus Au NPs can be synthesized by partly exchange of PPh3 with D-PA at toluene/water emulsion interface and are potentially applicable for other phosphine/thiolate pairs to modify Au NPs. [ABSTRACT FROM AUTHOR]

Suspended gold nanoparticle in water medium starts to warm up under nanosecond laser irradiation and creates a bubble around itself. The present study aims at evaluating the amount of nanoparticle size reduction at boiling temperature, the temperature variations of the nanoparticle, and its medium and finally the bubble formation moment. To this aim, Mie theory was used to calculate the absorption cross section of the nanoparticle in proximity of the bubble. Heat transfer equations were applied to determine the temperature of the nanoparticle and water. In addition, hydrodynamic equations were initiated to evaluate the expansion of the bubble. Then, these three groups of equations were coupled together and solved numerically. Based on the results, the bubble forms at the critical pressure and consequently due to the slow bubble velocity, temperature gradient in the medium is observed. Further, slight pulse width variations play a significant role on the nanoparticle temperature. The calculation of the nanoparticle heating associated with the creation of the bubble helps in controlling nanoparticle size and understanding the nanoscale heat transfer processes. [ABSTRACT FROM AUTHOR]

A high-affinity monoclonal antibody (mAb) has been prepared and separately a gold nanoparticle (AuNP)-based and a near-infrared (NIR) fluorescence-based lateral flow immunoassay (LFA) developed for determination of 5-hydroxyflunixin residue in raw milk. The AuNP and IRDye® 800CW were used to label anti-5-hydroxyflunixin mAb to form the AuNP-mAb and NIR dye-mAb conjugates, respectively. Quantitative determination of 5-hydroxyflunixin was achieved by imaging the optical or fluorescence intensity of the AuNP-mAb and NIR dye-mAb captured on the test line. As a result, the detection limits of the AuNP-based LFA and NIR dye-based LFA were 0.82 and 0.073 ng/mL in raw milk, respectively. The considerable improvement on assay sensitivity of the NIR-based LFA can be attributed to the lower background and less antibody consumption per test than that of the AuNP-based LFA. The spiking experiment by the NIR-based LFA yielded 85.7–112.6% recovery with a relative standard deviation below 14%, indicating that it has satisfactory assay accuracy and precision. Furthermore, the analytical results of actual samples by the NIR dye-based LFA were consistent with that by instrumental analysis. Therefore, these results demonstrated that the NIR dye is an ideal alternative label to the conventional AuNP for the development of LFA for veterinary drugs in animal-origin food. [ABSTRACT FROM AUTHOR]

The potential of cassava (Manihot esculenta Crantz.) for simultaneous Hg and Au phytoextraction was explored by investigating Hg and Au localization in cassava roots through Micro-Proton Induced X-Ray Emission, High-Resolution Transmission Electron Microscopy (HR-TEM) and X-Ray Diffractometry (XRD). The effect of Hg and Au in the cyanogenic glucoside linamarin distribution was also investigated using Matrix Assisted Laser Desorption Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (MALDI-FT-ICR-MS) imaging. Hg was located mainly in the root vascular bundle of plants grown in 50 or 100 μmol L−1 Hg solutions. Au was localized in the epidermis and cortex or in the epidermis and endodermis for 50 and 100 μmol L−1 Au solutions, respectively. For 50 μmol L−1 solutions of both Hg and Au, the two metals were co-localized in the epidermis. When the Hg concentrations were increased to 100 μmol L−1, Au was still localized to a considerable extent in the epidermis while Hg was located in all root parts. HR-TEM and XRD revealed that Au nanoparticles were formed in cassava roots. MALDI-FT-ICR-MS imaging showed linamarin distribution in the roots of control and plants and metal-exposed plants thus suggesting that linamarin might be involved in Hg and Au uptake and distribution. [ABSTRACT FROM AUTHOR]

Rapid increasing outbreak of Hepatitis E virus (HEV) shows an urgent need of HEV detection. Instead of time consuming and expensive RT-qPCR, an efficient and quick monitoring system is in utmost demand which can be comparable with the RT-qPCR in term of reliability and detection limit. An advanced platform for immunoassay has been constructed in this study by a nanozyme that constitutes anti-HEV IgG antibody-conjugated gold nanoparticles (Ab-AuNPs) as core and in situ silver deposition on the surface of Ab-AuNPs as outer shell. The virus has been entrapped on the nanocomposites while the silver-shell has decomposed back to the silver ions (Ag+) by adding a tetramethylbenzidine (TMBZ) and hydrogen peroxide (H 2 O 2) which indirectly quantifies the target virus concentration. Counterpart to only applying nanozyme, by incorporation of the enhanced effect of Ag shell on the AuNP-based nanozyme, the advance deposition has been confirmed to prove the signal amplification mechanism in the proposed immunoassay. Most importantly, the sensor performances have examined on the HEV, collected from the HEV-infected monkey over a period of 45 days. It was successfully correlated with the standard RT-qPCR data, showing the applicability of this immunoassay as a real-time monitoring on the HEV infection. The in situ formation of AuNPs@Ag as nanozyme in this capture immunoassay leads to a promising advancement over the conventional methods and nanozyme-based immunoassay in real application which can be a good substitute of RT-qPCR in near future. Image 1 • In situ silver deposition on surface of gold nanoparticles was prepared. • An advanced platform for immunoassay has amplified signal significantly. • HEV was successfully detected from fecal sample from HEV-infected monkey. • Sensor performance was correlated with their standard RT-qPCR data. [ABSTRACT FROM AUTHOR]

Protein glycosylation is an important post-translational modification and glycoproteins are associated with many crucial metabolic progresses of life. In order to detect glycoproteins sensitively, we propose a gold nanoparticles (GNPs) enumeration method based on boronate affinity sandwich system, which is constructed between the boronic acid polymer functionalized magnetic nanoparticles (Fe 3 O 4 @MPS@VPBA NPs) and 4-mercaptophenylboronic acid modified GNPs (GNPs-MPBA) by the targeted glycoproteins as the linker. Therefore, the sandwich complex is formed, resulting in the decrease of GNPs-MPBA counts in the solution. Based on the dark-field microscope (DFM) imaging technique, the sensitive GNPs enumeration assay is developed for glycoproteins quantitation. Immunoglobulin (IgG), as one of the important glycoproteins, is introduced to evaluate the proposed method. A low detection limit of 1.22 ng mL−1 for IgG analysis is obtained. The result indicates that the proposed GNPs enumeration method offers a simple, effective, label-free and highly sensitive strategy without signal amplification. It also possesses great potential for various target molecules determination at the single-particle level in the future. Image 1 • A gold nanoparticles enumeration method is established for glycoprotein detection for the first time. • A specific boronate affinity sandwich system is constructed for glycoprotein assay. • A wider linear range of 10 ng mL−1 to 10 μg mL−1 and lower detection limit of 1.22 ng mL−1 are attained.. • The potential practicality is verified by analyzing IgG in complex serum samples. [ABSTRACT FROM AUTHOR]

In this study, a tunable biosensor using the localized surface plasmon resonance (LSPR), controlling the distance between fluorescent CdZnSeS/ZnSeS quantum dots (QDs) and gold nanoparticles (AuNPs) has been developed for the detection of virus. The distance between the AuNPs and QDs has been controlled by a linkage with a peptide chain of 18 amino acids. In the optimized condition, the fluorescent properties of the QDs have been enhanced due to the surface plasmon effect of the adjacent AuNPs. Successive virus binding on the peptide chain induces steric hindrance on the LSPR behavior and the fluorescence of QDs has been quenched. After analyzing all the possible aspect of the CdZnSeS/ZnSeS QD-peptide-AuNP nanocomposites, we have detected different concentration of influenza virus in a linear range of 10−14 to 10−9 g mL−1 with detection limit of 17.02 fg mL−1. On the basis of the obtained results, this proposed biosensor can be a good alternative for the detection of infectious viruses in the various range of sensing application. Image 1 • Tunable LSPR-based biosensor was developed by a fluorescent QDs and AuNPs, linked with a customized peptide. • Virus binding on the peptide chain induces restrictions on the LSPR transfer, resulting quenching. • Applying this sensor, influenza virus was detected in a wide linear range of 10−14 to 10−9 g mL−1. • This stable and covalently designed sensor shows excellent sensitivity with a detection limit of 17.02 fg mL−1. [ABSTRACT FROM AUTHOR]

Au LIII edge X-ray absorption spectroscopic measurements were carried out over a series of Au nanoparticles embedded glasses with SnO2 and SeO2. The results obtained from EXAFS and XANES confirms the typical characteristics and structure of gold nanoparticles in these glasses. Raman analysis was performed to understand the structure of the glass. XANES data reveal that these glasses show Au0 and Au+1 oxidation state depending on reducing agent. EXAFS refinements were performed using ARTEMIS software to calculate bond lengths, R-factor and Debye–Waller factor on these glasses. [ABSTRACT FROM AUTHOR]

The bionanocomplexes of proteins and nanoparticles are promising bionanomaterials for medical purposes like the sensitive and the selective diagnostic devices, as well as, the modern therapeutic agents. The presence of the noble metals allows for obtaining the plasmonic effect and for generating the surface-enhanced Raman scattering phenomenon (SERS). The knowledge of the nanoparticle interaction with the protein molecule is extremely necessary for the development of the suitable product. The interaction of the bionanocomplex components can cause the conformational changes in the protein structure and the modification of surface properties of the nanoparticles. In the case of the binding of the gold nanoparticles with the enzymes, it is critical to preserve the catalytic activity, which is connected with maintaining the proper molecule structure. In the presented study, the Fourier transform infrared spectroscopy was used for the investigation of the interaction and the structural properties of the cholesterol oxidase (ChOX)—the gold nanoparticles bionanocomplex. The ChOX is one of the most important enzymes for the medical diagnostics and the promising antibacterial agent. The infrared spectra of the AuNP-ChOX bionanocomplex and the ChOX in different forms (the solid and the suspended in the buffer) are presented and discussed. The obtained spectra include the considerable number of the absorption lines identified and attributed to the corresponding chemical bonds and the functional groups of the protein. The analysis of the obtained infrared spectra revealed the important information about the changes of the protein structure after the immobilization on the gold nanoparticles. Moreover, it allows to recognize the differences in the structure of the protein in a different environment, which is of great importance in the context of bionanotechnology. [ABSTRACT FROM AUTHOR]

Herein, we report a new probe for the determination of the concentration of NF-κB p50, one kind of DNA-binding transcription factors (TFs), by using Exonuclease III (Exo III)-aided amplification and gold nanoparticle mediated fluorescence intensity. Since TFs play critical roles in various biological processes, the detection of TFs can provide a lot of useful biological information for studding gene expression regulation related disease. In our system, in the presence of transcription factor, Exo III based amplification reaction was trigged. This enzymatic digestion results in the release of intermediate DNA and ultimately liberating the fluorophore (which, separated from the quencher of AuNP and BHQ2, now fluoresces). The released intermediate DNA then hybridizes with another strand3, whence the cycle starts anew. So, the fluorescence intensity reflects the NF-κB p50 concentration with a detection limit of 1.32 pM. Importantly, this method might be further extended to selectively detect various dsDNA-binding proteins by simply changing the binding-site sequences of strand1/strand2 duplex probes. Schematic presentation of the probe for ultrasensitive detection of NF-κB p50. In this probe, AuNP was employed as the frame and fluorophore Cy3 was used as the signal output element. Image 1 • We report a new strategy here for detecting NF-κB p50 concentration. • This strategy coupled DNA duplexes on AuNP surface with Exo III-aided amplification technique. • This strategy exhibits a good sensitivity with a limit of detection (LOD) of 1.32 pM. • This strategy has the potential for screening transcription factor inhibitors for drug research and development. [ABSTRACT FROM AUTHOR]

A biocompatible natural polysaccharide (PSP001) isolated from the fruit rind of Punica granatum was conjugated with L-cysteine (Y) to be used as a skeleton for the fabrication of fluorescent gold nanoclusters (AuNCs) represented as PSP-Y-AuNCs. With an average size of ~ 6 nm, PSP-Y-AuNCs demonstrated high quantum yield (31%), with a pH-sensitive fluorescence emission behavior. An emission maximum of 520 nm was obtained at acidic pH, which was blue shifted with increasing pH. This feature provides the possibilities for accurate ratiometric pH imaging. The PSP-Y-AuNCs not only demonstrated excellent biocompatibility with cancer cells and isolated peripheral lymphocytes and red blood cells but also demonstrated to be an active molecular imaging probe with appealing cellular uptake efficiency. The investigations with BALB/c mice further confirmed the non-toxic nature and in vivo imaging potential of the AuNCs. Estimation of the bio-distribution on solid tumor bearing syngeneic murine models revealed a tumor-targeted enhanced fluorescence emission pattern which is attributed to the pH responsive fluorescence behavior and the acidic microenvironment of the tumor. These findings were further confirmed with an impressive tumor accumulation pattern displayed in a xenograft of human cancer bearing nude mice. On account of their impressive biocompatibility and photophysical features, PSP-Y-AuNCs can exploited for the real-time fluorescence imaging of cancer tissues. [ABSTRACT FROM AUTHOR]

A method for rapid and accurate determination of avian pathogenic Escherichia coli serotype O78 (APEC O78) by the gold nanoparticle-labeled lateral flow strip method, entitled molecule capturer analysis system (MCAS), is described. Target virulence-associated gene of APEC O78 is adopted as the analyte. After pre-amplification with the designed functional primer set, numerous new-formed amplicons are simultaneously labeled with fluorescein isothiocyanate (FITC) and digoxin. AuNPs with a diameter of 18 nm and the characteristic plasmonic peak at 526 nm are utilized for labeling. These two labels of FITC and digoxin are further captured and measured with the AuNP-labeled lateral flow strip, and the AuNPs are retained on the test line through the immunoreaction for signal output. Under optimized conditions, this MCAS protocol can determine the target APEC O78 with excellent determination limit of 4.3 cfu mL−1 based on the optical density of AuNPs on the test line of lateral flow strips. The working range is 2.52 × 101 to 1.63 × 107 cfu mL−1. Spiked serum samples are rapid and accurately measured, and the results are highly correlated with those of the real-time PCR. With this MCAS protocol, rapid and on-site determination of APEC O78 can be realized without expensive instruments or professional personnel. This MCAS protocol can be easily applied to other analytes by just replacing the traditional primer set with functionalization primer set. [ABSTRACT FROM AUTHOR]

An automated acquisition system for collecting a large number of electron holograms, to improve the statistical precision of phase analysis, was developed. A technique for shifting the electron beam in combination with stage movement allows data to be acquired over a wide area of a TEM-specimen grid. Undesired drift in the hologram position, which may occur during the hologram acquisition, can be corrected in real time by automated detection of the interference-fringe region in an image. To demonstrate the usefulness of the developed automated hologram acquisition system, gold nanoparticles dispersed on a carbon foil were observed with a 1.2-MV atomic resolution holography electron microscope. The system could obtain 1024 holograms, which provided phase maps for more than 500 nanoparticles with a lateral resolution of 0.14 nm, in just 1 h. The observation results revealed an anomalous increase in mean inner potential for a particle size smaller than 4 nm. The developed automated hologram acquisition system can be applied to improve the precision of phase measurement by averaging many phase images, as demonstrated by single particle analysis for biological entities. Moreover, the system makes it possible to study electrostatic potential of catalysts and other functional nanoparticles at atomic resolution. [ABSTRACT FROM AUTHOR]

Featured Application: According to our results, AuNPs with thermal stability and antioxidant property prepared through biogenic approaches have potential use in food preservation. We have developed a "green" method for fabricating gold nanoparticles (AuNPs) through biogenic approaches. The proposed method has the advantages of facile preparation under ecofriendly conditions. AuNPs encapsulated in carbon nanosheets, and exhibiting high thermal stability, were fabricated by autoclaving pectin-capped AuNPs, which were subsequently collected through high-speed centrifugation and redispersed in aqueous solution. The 1,1-diphenyl-2-picrylhydrazy (DPPH) radical scavenging assay indicated that our prepared AuNPs exhibited more prolonged antioxidant capacity than pristine apple extracts. Electron paramagnetic resonance (EPR) spectra showed that approximately 80% of DPPH radicals were scavenged by the pectin-capped AuNPs at a concentration of 3 mg/mL. According to our results, AuNPs prepared through biogenic approaches have potential use in the food industry. [ABSTRACT FROM AUTHOR]

Polyhydroxylated fullerene derivatives (fullerenols: C60(OH)12 and C60(OH)36) exhibit excellent stabilizing matrices for gold nanoparticles. Au:C60(OH)12 and Au:C60(OH)36 form hydrophilic colloids and are well dispersed in H2O, even though C60(OH)12 itself is barely dissolved in H2O. It was estimated that C60(OH)12 forms a two‐ to three‐layered structure with 3D O−H⋅⋅⋅O hydrogen‐bonding networks, surrounding approximately 3 nm‐sized Au NPs. The thus‐prepared Au:C60(OH)n colloids exhibited a high catalytic activity toward the reduction of 4‐nitrophenol to 4‐aminophenol. The short induction period as well as kinetic and thermodynamic parameters indicated the dynamic mobility of the fullerenol matrix and the hydrophobic nature of the interface between the Au surface and the matrix. [ABSTRACT FROM AUTHOR]

This study proposes the synthesis of a type of anticancer nanoparticle, aptamers and Au nanoparticle (Apt-Au)-modified Morin pH-sensitive liposome (MSL), which exhibits targeting properties. Tumors are difficult to cure because their microenvironment varies from that of normal tissue; its pH is lower than that of normal tissue, which generally impedes the effectiveness of drugs. Thus, pH-responsive drugs have attracted extensive attention. Gold nanoparticles (AuNPs) show potential as drug carriers because of their small size, good biocompatibility, easy surface modification, and strong cell penetration. Apt-Au@MSL exhibits excellent monodispersity and tumor-targeting properties and can be released in partly acidic environment via dialysis. We screened our model cancer cell by MTT assay and found that SGC-7901 cells can effectively suppress proliferation. In vivo results demonstrate that the administration of Apt-Au@MSL could inhibit tumor growth in xenograft mouse models. H&E staining and TUNEL assay further confirmed that Apt-Au@MSL can promote tumor apoptosis. Apt-Au@MSL may induce apoptosis by triggering overproduction of reactive oxygen species (ROS) and regulating multiple signal crosstalk. Both blood biochemistry tests and H&E staining suggested that these materials exhibit negligible acute toxicity and good biocompatibility in vivo. With its powerful function, Apt-Au@MSL can be used as a target-based anticancer material for future clinical cancer treatment. [ABSTRACT FROM AUTHOR]

Gold nanoparticle-core spherical nucleic acids (AuNP core-SNAs), by virtue of the programmable nature of oligonucleotides, have yielded access to the innovative strategies for targeted biodiagnostics. Here, DNA-directed self-assembly of AuNP core-SNAs has been used to design a colorimetric method to sense HIV-1 viral nucleic acid. This strategy utilizes an oligonucleotide with sequence of 5′-untranslated region (5′ UTR) of the HIV-1 RNA genome anchored on the surface of AuNPs and a complementary linker strand with a palindromic sequence tail. In the absence of HIV-1 target nucleic acid the complementary linker induces self-assembly of SNAs based on sequence symmetry in the free palindromic tail which can bridge two DNA double helices. While in the presence of the target DNA, due to linker-target duplex formation, the colloidal stability and the red color of the SNAs solution are preserved. Picomole amounts of target DNA can easily be detected with the naked eyes. A 95-mer synthetic DNA strand with the same sequence of HIV-1 viral RNA was utilized for positive control of HIV-1 RNA. The selectivity of the selected linker was satisfactory up to 90% match. Image 1 • A simple colorimetric method to detect HIV-1 nucleic acid is developed. • Palindromic nature of the designed linker made a single component self-assembly system. • The detection is based on the inhibitory effect of the target HIV genome on AuNP core-SNAs assembly. • The method may be generalized to any nucleic acid targets with palindromic regions in their genome. [ABSTRACT FROM AUTHOR]

In this study, a sensitive nicotinamide adenine dinucleotide (NADH) biosensor based on Au‐Copper oxide nanocomposite modified carbon ceramic electrode (Au−CuO/CCE) was introduced. The developed NADH biosensor was prepared by controlled electrodeposition of copper and Au nanoparticles on the surface of a renewable CCE and was turned to Au−CuO/CCE by cycling the potential in alkaline media. The prepared electrode was carefully characterized with scanning electron microscopy, X‐ray diffraction, atomic force microscopy and cyclic voltammetry techniques. According to scan rate study, surface coverage (Γ) of the fabricated Au−CuO/CCE was calculated to be 1.54×10−8 mol cm−2 which was 3 time more than CuO/CCE. The fabricated electrode is well stable which could be reliably utilized for the determination of NADH with amperometry technique over the concentration range of 1–29 μM with sensitivity and detection limit (S/N=3) of 0.1025 μA μM−1 and 0.09 μM respectively. The prepared biosensor was used for NADH determination in serum samples with fast response time and satisfactory analytical results. [ABSTRACT FROM AUTHOR]

In this study, a new HAP/rGO/AuNPs-AO modified carbon electrode (GCE) was fabricated for amperometric detection of ascorbic acid. The HAP/rGO/AuNPs composite was prepared by one-step hydrothermal method. The large specific surface area, strong adsorption and excellent biocompatibility of HAP nanowires enabled fast, stable and accurate detection of ascorbic acid. As array of quantum dot, AuNPs had strong electrocatalytic activity in addition to good adsorption to enzymes, which could provide high sensitivity and low limit of detection for biosensor. Then rGO ensured that current signal could be quickly transferred from the composite to electrode. Under the optimum conditions, the prepared biosensor demonstrated a wide linear range from 0.39 to 36 mM (R2 = 0.99845), a low limit of detection (3.39 μM, S/N = 3) and a high sensitivity (15.949 mA moL−1) with good selectivity, stability (10.8%) and repeatability (3.9%), which might providing a reasonable and reliable way for ascorbic acid detection. [ABSTRACT FROM AUTHOR]

Ultrathin films consisting of titanium oxide and gold nanoparticles were prepared using a combination of the surface sol–gel process and liquid/liquid interfacial precipitation. The composite films had a titanium oxide/gold nanoparticle layer/titanium oxide film structure, comprising a gold nanoparticle thin-film layer sandwiched within titanium oxide films of nanometer-order thickness. Upon heating the titanium oxide–gold nanoparticle composite films to 450 °C, they underwent a phase change from the amorphous to the anatase phase, which was confirmed via Raman scattering analysis. It was observed that, even after heating, the plasmonic absorption band due to the presence of gold nanoparticles was maintained in the composite films. The photocatalytic degradation efficiencies of methylene blue dye were evaluated in films under 520 nm light irradiation. The results suggested that the sandwich-like structure of this titanium oxide/gold nanoparticle layer/titanium oxide is promising for the visible-light-induced degradation of methylene blue dye. Highlights: A series of titanium oxide–gold nanoparticle composite thin films with nanometer thickness were prepared. Formation of anatase titanium oxide ultrathin film was confirmed by Raman scattering analysis. Sandwich-like structured titanium oxide/gold nanoparticle layer/titanium oxide composite ultrathin films is promising for the visible-light-driven photocatalyst. [ABSTRACT FROM AUTHOR]

Authors report on a new fluoro-graphene-plasmonic nanohybrid aptamer-based fluorescent nanoprobe for cocaine. To construct the nanoprobe, newly synthesized glutathione-capped ZnS/Ag2Se quantum dots (QDs) were first conjugated to graphene oxide (GO) to form a QD-GO nanocomposite. The binding interaction resulted in a fluorescence turn-ON. Thereafter, cetyltrimethylammonium bromide (CTAB)-gold nanoparticles (AuNPs) were directly adsorbed on the QD-GO nanocomposite to form a novel QD-GO-CTAB-AuNP nanohybrid assembly that resulted in a fluorescence turn-OFF. Streptavidin (strep) was then adsorbed on the QDs-GO-CTAB-AuNP nanohybrid assembly which allowed binding to a biotinylated MNS 4.1 anticocaine DNA aptamer (B) receptor. The addition of cocaine into the strep-B-QDs-GO-CTAB-AuNP aptamer nanoprobe system aided affinity to the aptamer receptor and in turn turned on the fluorescence of the nanoprobe in a concentration-dependent manner. Under optimum experimental conditions, we found the strep-B-QD-GO-CTAB-AuNP to be far superior in its sensitivity to cocaine than the tested strep-B-QDs (no GO and CTAB-AuNPs), strep-B-QD-CTAB-AuNP (no GO) and strep-B-QD-GO (no CTAB-AuNP). In addition, the investigation of localized surface plasmon resonance (LSPR) amplified signal from tested plasmonic NPs shows that CTAB-AuNPs was far superior in amplifying the fluorescence signal of the nanoprobe. A detection limit of 4.6 nM (1.56 ng.mL−1), rapid response time (~2 min) and excellent selectivity against other drugs, substances and cocaine metabolites was achieved. The strep-B-QD-GO-CTAB-AuNP aptamer-based fluorescent nanoprobe was successfully applied for the determination of cocaine in seized adulterated cocaine samples. [ABSTRACT FROM AUTHOR]

Electrochemical assay for analysis of cell surface glycan expression is reported. Mannose on human breast cancer cells (type MCF-7) is selected as the glycan model. Gold nanoparticles are modified with binding aptamer for MCF-7 cells and act as electrochemical probe. The analysis of cell surface glycan expression follows a traditional sandwich protocol. Concanavalin A that can specifically recognize mannose is immobilized onto MnO2 nanosheets modified electrode for the capture of MCF-7 cells. Then, the modified gold nanoparticles are immobilized onto the electrode via the binding between MCF-7 cell and aptamer on the gold nanoparticles. The aptamer on the gold nanoparticles reacts with molybdate. More specifically, the reaction of the phosphate backbone of aptamer with molybdate results in the formation of a redox-active molybdophosphate precipitate and generates an electrochemical current. The current intensity at 0.20 V (vs. Ag/AgCl) is recorded to test the linear range of the assay. The assay shows an obvious response to MCF-7 cells with a wide linear range from 1.0 × 103 to 1.0 × 106 cells mL−1 and a limit of detection down to 300 cells mL−1. The assay can be used to selectively monitor the change of mannose expression on cell surfaces upon the treatment with the N-glycan inhibitor. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate IL-dependent PDT of GNPs using two water-soluble IL-type PSs to develop promising PSs with a suitable delivery system for PDT. The synthesis of IL-type PSs (PS1 and PS2) and GNPs (GNP1 and GNP2) was straightforward (Figures S1-S7, Supporting Information). The wt % of organic and inorganic contents in each GNP were used to calculate exact amount of each PS on corresponding GNP (GNP1 contains 492 nmol/mg PS1; GNP2 contains 573 nmol/mg PS2), and used in further cell study.[24] GNP1 had 11-fold higher photoactivity than GNP2 in which different result between GNP1 and GNP2 might be attributed by the faster drug delivery effect of GNP1 compared with GNP2 based on the corresponding each IL-type PS ability. [Extracted from the article]

An electrochemical immunosensing platform capable of detecting Immunoglobulin G (IgG) concentration as low as femtograms was developed based on signal amplification strategy. The immunosensing platform was fabricated using self-assembled monolayers (SAM) of 11- mercaptoundecanoic acid (MUDA) on a gold disc electrode. The covalent immobilization of antibody was achieved through the bonding of a carboxyl group of MUDA and amino group of antibody using [1-ethyl-3-(3-dimethylaminopropyl) carbodiimide] (EDC) and N-hydroxysuccinimide (NHS) chemistry. The formation of SAM and antibody immobilization was analyzed using cyclic voltammetry and electrochemical impedance spectroscopy. The gold nanoparticles conjugated with horseradish peroxidase-labeled secondary antibodies were used as nanolabels, to increase the sensitivity and catalytic efficiency of the immunosensor. The sandwich immunocomplex formed on the electrode surface produced an electrocatalytic response through the reduction of hydrogen peroxide in the presence of thionin. The fabricated immunosensor exhibited two linear ranges that included IgG concentrations of 10 fg mL−1 to 0.1 ng mL−1 and 0.1 to 100 ng mL−1 respectively. [ABSTRACT FROM AUTHOR]