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A complementary DNA (cDNA) was designed to simultaneously hybridize with the ochratoxin A (OTA) aptamer and the fumonisin B1 (FB1) aptamer to form a unique Y-shaped DNA structure and to achieve simultaneous detection. Gold nanorods (AuNRs) were used to immobilize thionine (Th), thiolated ferrocene (Fc), thiolated OTA aptamer (Apt1), and thiolated FB1 aptamer (Apt2), to form an amplified signal element and a recognition element. The Apt1-AuNRs-Th complex and the Apt2-AuNRs-Fc complex hybridize with cDNA to form a unique Y-DNA structure on a gold electrode. This produces two initial electrochemical signals [with 177 μΑ cm −2 near −0.2 V, and 3121 μΑ cm −2 near +0.46 V (vs. Ag/AgCl)] by differential pulse voltammetry. Upon addition of 0.1 ng mL −1 OTA and 0.1 ng mL −1 FB1, the aptamers bind the two toxins. This results in the release of Apt1-AuNRs-Th and Apt2-AuNRs-Fc, so the peak currents densities decrease to 115 μΑ cm −2 and 209 μΑ cm −2 . The assay allows simultaneous determination of OTA and FB1 in the 1.0 pg·mL −1 to 100 ng·mL −1 concentration ranges, with LODs of 0.47 and 0.26 pg·mL −1 . The assay is reproducible, stable and specific. It was applied to the determination of OTA and FB1 in spiked beer, with recoveries between 89.0% and 102.0%. Graphical abstract Schematic representation of OTA and FB 1 detection based on Apt 2 -AuNRs-Fc/Apt 1 -AuNRs-Th/cDNA/AuE. (AuNRs: Gold nanorods; Th: thionine; Fc: ferrocene; SH: thiol; BSA: Bovine serum albumin; cDNA: Complementary DNA; Apt 1 : Aptamer1; Apt 2 : Aptamer2; OTA: Ochratoxin A; FB 1 : Fumonisin B 1 ).

A colorimetric method is described for the determination of ferrous ion (Fe 2+ ) with high sensitivity and selectivity. The method is based on catalytic etching of gold nanorod (NR). In an acid condition, Fe 2+ reacts with H 2 O 2 to produce superoxide radical (O 2 •− ) that etches gold NRs from the low energy surface along the longitudinal direction preferentially. As a result, the changes in the absorption spectrum and color of gold NR can be measured and also can be detected visually. Under the optimal conditions, the assay has very low detection limit (13.5 nM) and a linear response in a concentration range of 75 to 1 μM. The method was applied to the determination of Fe 2+ in spiked samples of fetal bovine serum and also transferred to a kind of test stripe for use in fast practical applications. A unique colorimetric sensing method is demonstrated for the colorimetric detection of Fe 2+ , again based on the oxidation of gold nanorods which leads to the blue-shift of the absorption. Graphical abstract A unique colorimetric sensing method was shown for the colorimetric detection of Fe 2+ . Fe 2+ reacts with H 2 O 2 to generate superoxide radical that oxidize gold nanorods. This leads to a color change from blue-green to pink.

Plasmonic photothermal therapy (PPTT) is a cancer therapy in which gold nanorods are injected at the site of a tumor before near-infrared light is transiently applied to the tumor causing localized cell death. Previously, PPTT studies have been carried out on xenograft mice models. Herein, we report a study showing the feasibility of PPTT as applied to natural tumors in the mammary glands of dogs and cats, which more realistically represent their human equivalents at the molecular level. We optimized a regime of three low PPTT doses at 2-week intervals that ablated tumors mainly via apoptosis in 13 natural mammary gland tumors from seven animals. Histopathology, X-ray, blood profiles, and comprehensive examinations were used for both the diagnosis and the evaluation of tumor statuses before and after treatment. Histopathology results showed an obvious reduction in the cancer grade shortly after the first treatment and a complete regression after the third treatment. Blood tests showed no obvious change in liver and kidney functions. Similarly, X-ray diffraction showed no metastasis after 1 year of treatment. In conclusion, our study suggests the feasibility of applying the gold nanorods-PPTT on natural tumors in dogs and cats without any relapse or toxicity effects after 1 year of treatment.

Tailoring efficient nonlinear optical materials continues to be a topic of great interest in the scientific field. In this paper, we study the nonlinear response of graphene oxide nanosheets GO, gold nanorods AuNRs, and graphene oxide/gold nanorods hybrid nanocomposite GO@AuNRs respectively, GO was prepared by modified Hummer method while AuNRs were prepared by the seed-mediated method and GO@AuNRs prepared by simple ex-situ method. The nonlinear absorption was measured via open aperture Z scan using nanosecond pulses at 532 nm, The nonlinear absorption coefficients were measured for the proposed materials in colloidal and polymeric forms. The results show an enhancement of the nonlinear absorption and optical limiting of GO@AuNRs over GO and AuNRs. Furthermore, enhanced optical nonlinearity and stability are achieved in polymeric form compared to colloidal forms. These materials could potentially be used in optical limiting applications and photonic devices. Graphical abstract Article highlights The nonlinear optical absorption of three different materials—graphene oxide nanosheets (GO), gold nanorods (AuNRs), and a hybrid of the two known as GO@AuNRs—was examined in this study. The findings revealed that GO@AuNRs had better nonlinear absorption and optical limiting properties than GO and AuNRs alone. In addition, the materials' optical nonlinearity and stability were improved in the polymer-based form compared to their colloidal counterparts. These results imply that these materials have a promising future for use in optical limiting and photonic devices.

This work reports on the design, development, and characterization of novel magneto-plasmonic elastic liposomes (MPELs) of DPPC:SP80 (85:15) containing Mg0.75Ca0.25Fe2O4 nanoparticles coupled with gold nanorods, for topical application of photothermal therapy (PTT). Both magnetic and plasmonic components were characterized regarding their structural, morphological, magnetic and photothermal properties. The magnetic nanoparticles display a cubic shape and a size (major axis) of 37 ± 3 nm, while the longitudinal and transverse sizes of the nanorods are 46 ± 7 nm and 12 ± 1.6 nm, respectively. A new methodology was employed to couple the magnetic and plasmonic nanostructures, using cysteine as bridge. The potential for photothermia was evaluated for the magnetic nanoparticles, gold nanorods and the coupled magnetic/plasmonic nanoparticles, which demonstrated a maximum temperature variation of 28.9 °C, 33.6 °C and 37.2 °C, respectively, during a 30 min NIR-laser irradiation of 1 mg/mL dispersions. Using fluorescence anisotropy studies, a phase transition temperature (Tm) of 35 °C was estimated for MPELs, which ensures an enhanced fluidity crucial for effective crossing of the skin layers. The photothermal potential of this novel nanostructure corresponds to a specific absorption rate (SAR) of 616.9 W/g and a maximum temperature increase of 33.5 °C. These findings point to the development of thermoelastic nanocarriers with suitable features to act as photothermal hyperthermia agents.

The cancer mortality rate has increased, and conventional cancer treatments are known for having many side effects. Therefore, it is imperative to find a new therapeutic agent or modify the existing therapeutic agents for better performance and efficiency. Herein, a synergetic phototherapeutic agent based on a combination of photothermal and photodynamic therapy is proposed. The phototherapeutic agent consists of water-soluble cationic porphyrin (5,10,15,20-tetrakis(N-methylpyridinium-3-yl)porphyrin, TMePyP), and gold nanorods (AuNRs) anchored on graphene-oxide (GO) sheet. The TMePyP was initially synthesized by Adler method, followed by methylation, while GO and AuNRs were synthesized using Hummer’s and seed-mediated methods, respectively. The structural and optical properties of TMePyP were confirmed using UV-Vis, zeta analyzer, PL, FTIR and NMR. The formation of both GO and AuNRs was confirmed by UV-Vis-NIR, FTIR, TEM and zeta analyzer. TMePyP and AuNRs were anchored on GO to form GO@AuNRs-TMePyP nanocomposite. The as-synthesized nanocomposite was stable in RPMI and PBS medium, and, on irradiation, produced high heat than the bare AuNRs, with high photothermal efficiency. In addition, the nanocomposite produced higher singlet oxygen than TMePyP with high biocompatibility in the absence of light. These results indicated that the as-synthesized nanocomposite is a promising dual photodynamic and photothermal agent for cancer therapy.

A new comprehensive analytical approach based on single-particle inductively coupled plasma-sector field mass spectrometry (spICP-SFMS) and electrical asymmetric-flow field-flow-fractionation combined with multi-angle light scattering detection (EAF4-MALS) has been examined for the characterization of galactosamine-terminated poly(N-hydroxyethyl acrylamide)-coated gold nanorods (GNRs) in two different degrees of polymerization (DP) by tuning the feed ratio (short: DP 35; long: DP 60). spICP-SFMS provided information on the particle number concentration, size and size distribution of the GNRs, and was found to be useful as an orthogonal method for fast characterization of GNRs. Glycoconjugated GNRs were separated and characterized via EAF4-MALS in terms of their size and charge and compared to the bare GNRs. In contrast to spICP-SFMS, EAF4-MALS was also able of providing an estimate of the thickness of the glycopolymer coating on the GNRs surface.

Amyloid fibrils, which are closely associated with various neurodegenerative diseases, are the final products in many protein aggregation pathways. The identification of fibrils at low concentration is, therefore, pivotal in disease diagnosis and development of therapeutic strategies. We report a methodology for the specific identification of amyloid fibrils using chiroptical effects in plasmonic nanoparticles. The formation of amyloid fibrils based on α-synuclein was probed using gold nanorods, which showed no apparent interaction with monomeric proteins but effective adsorption onto fibril structures via noncovalent interactions. The amyloid structure drives a helical nanorod arrangement, resulting in intense optical activity at the surface plasmon resonance wavelengths. This sensing technique was successfully applied to human brain homogenates of patients affected by Parkinson’s disease, wherein protein fibrils related to the disease were identified through chiral signals from Au nanorods in the visible and near IR, whereas healthy brain samples did not exhibit any meaningful optical activity. The technique was additionally extended to the specific detection of infectious amyloids formed by prion proteins, thereby confirming the wide potential of the technique. The intense chiral response driven by strong dipolar coupling in helical Au nanorod arrangements allowed us to detect amyloid fibrils down to nanomolar concentrations.

In this study, a nanoporous cellulose paper-based SERS platform was developed to analyze multiplex hazardous pesticides including thiram (T1), tricyclazole (T2), and carbaryl (C) by surface enhanced Raman scattering (SERS). Gold nanorods (AuNRs) with different aspect ratios were synthesized and compared to achieve the highest SERS signals on paper-based SERS substrates. The advantage of the nanoporous cellulose nanofiber (CNF) matrix with nanoscale surface roughness is that it allows actual nanofiltration, resulting in a uniform and well-controlled AuNR distribution on the top portion of the CNF matrix. The as-prepared CNF–AuNR-based SERS platform exhibited an enhancement factor of 1.4 × 10 7 as well as the ability to simultaneously detect T1, T2, and C at concentrations as low as 1 nM, 100 nM, and 1 μM, respectively. In addition to analyzing triplex pesticide mixtures in solution, the SERS platform allows for a paper-based SERS swab for rapid trace detection on real-world surfaces. The detection limits for T1, T2, and C residues in apple peels were 6, 60, and 600 ng cm −2 , respectively, which are much lower than the maximum residue level requirement for apple peels (2000 ng cm −2 ). These results demonstrate that the low-cost, flexible, lightweight, paper-based SERS platform shows powerful potential for high SERS performance and on-site SERS analysis. Graphical abstract

Cancer is a grievous disease whose treatment requires a more efficient, non-invasive therapy, associated with minimal side effects. Gold nanoparticles possessing greatly impressive optical properties have been a forerunner in bioengineered cancer therapy. This theranostic system has gained immense popularity and finds its application in the field of molecular detection, biological imaging, cancer cell targeting, etc. The photothermal property of nanoparticles, especially of gold nanorods, causes absorption of the light incident by the light source, and transforms it into heat, resulting in tumor cell destruction. This review describes the different optical features of gold nanoparticles and summarizes the advance research done for the application of gold nanoparticles and precisely gold nanorods for combating various cancers including breast, lung, colon, oral, prostate, and pancreatic cancer.