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In recent years, concerns have been raised regarding the contamination of grapes with pesticide residues. As consumer demand for safer food products grows, regular monitoring of pesticide residues in food has become essential. This study sought to develop a rapid and sensitive technique for detecting two specific pesticides (phosmet and paraquat) present on the grape surface using the surface-enhanced Raman spectroscopy (SERS) method. Gold nanostars (AuNS) particles were synthesized, featuring spiky tips that act as hot spots for localized surface plasmon resonance, thereby enhancing Raman signals. Additionally, the roughened surface of AuNS increases the surface area, resulting in improved interactions between the substrate and analyte molecules. Prominent Raman peaks of mixed contaminants were acquired and used to characterize and quantify the pesticides. It was observed that the SERS intensity of the Raman peaks changed in proportion to the concentration ratio of phosmet and paraquat. Moreover, AuNS exhibited superior SERS enhancement compared to gold nanoparticles. The results demonstrate that the lowest detectable concentration for both pesticides on grape surfaces is 0.5 mg/kg. These findings suggest that SERS coupled with AuNS constitutes a practical and promising approach for detecting and quantifying trace contaminants in food. PRACTICAL APPLICATION: This research established a novel surface-enhanced Raman spectroscopy (SERS) method coupled with a simplified extraction protocol and gold nanostar substrates to detect trace levels of pesticides in fresh produce. The detection limits meet the maximum residue limits set by the EPA. This substrate has great potential for rapid measurements of chemical contaminants in foods., (© 2024 Institute of Food Technologists.)

Glycinin is one of the most nutritious ingredients in soybean, but it is also an allergen that can cause allergic reactions in humans and animals, and even endanger life in severe cases. Therefore, it is imperative to develop a rapid and ultrasensitive detection method for glycinin. In order to achieve this goal, this experiment combined surface-enhanced Raman spectroscopy (SERS) technology with an economical, simple, fast and easy-to-carry immunochromatographic test strip, and successfully constructed an efficient sandwich immunochromatographic test strip. The immunoprobe of the test strip was covalently coupled by gold nanostars (AuNSs), Raman molecule 4-aminothiophenol (4-PATP) and rabbit polyclonal antibody. In this experiment, a gold nanostar immunochromatographic test strip for detecting glycinin was established. The detection limit of the test strip was 0.23 ng / mL, the recovery rate was 91.5-96.6 %, and the coefficient of variation was 1.61-6.15 %. In addition, the test strip had no cross reaction with whey protein, wheat protein, peanut protein, sesame protein and β-conglycinin, indicating that the detection method had good specificity and the ability to avoid false positive results. Hence, this experiment successfully prepared a rapid and sensitive test strip for glycinin., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A multicolor visual method for the detection of hydrogen peroxide (H 2 O 2 ) was reported based on the iodide-mediated surface etching of gold nanostar (AuNS). First, AuNS was prepared by a seed-mediated method in a HEPES buffer. AuNS shows two different LSPR absorbance bands at 736 nm and 550 nm, respectively. Multicolor was generated by iodide-mediated surface etching of AuNS in the presence of H 2 O 2 . Under the optimized conditions, the absorption peak Δλ had a good linear relationship with the concentration of H 2 O 2 with a linear range from 0.67~66.67 μmol L -1 , and the detection limit is 0.44 μmol L -1 . It can be used to detect residual H 2 O 2 in tap water samples. This method offered a promising visual method for point-of-care testing of H 2 O 2 -related biomarkers.

Bacterial pathogens represent a safety concern in the food industry, and this is amplified by the lack of sensing devices that can be applied on-site by non-trained personnel. In this study, peroxidase-mimicking activity of gold nanostars was exploited to develop a user-friendly colourimetric sensor. A smartphone was exploited as an image reader and analyser, empowered with a novel App developed in-house. The mobile App was evaluated and compared with a commercial smartphone App for its capability to quantify generated colourimetric signals. A major obstacle found with sensors relying on gold nanozymes is the fact that modification of the surface of gold nanoparticles with biorecognition elements generally lead to a suppression of their nanozyme activity. This drawback was overcome by introducing an autocatalytic growth step, which successfully restored the peroxidase-mimicking activity through generation of new gold nanoseeds acting as catalytic centres. A proof-of-concept using this sensing mechanism was developed targeting Mycobacterium bovis, a zoonotic pathogen primarily found in cattle but that can be transmitted to humans by consumption of contaminated food and cause tuberculosis disease. The resulting smartphone-based immunological sensor has shown promising results with a linear response between 10 4 - 10 6  CFU/mL, enabling detection of M. bovis at concentrations as low as 7.2·10 3  CFU/mL in buffer conditions. It is anticipated that the concept of the developed approach will have applicability in many fields relying on smartphone-based biosensing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

A novel ratiometric electrochemiluminescence (ECL) system based on gold nanostars (AuNSs) support was constructed for the determination of hypotonicity-induced ATP release from HepG2 cells. AuNS@Lu nanoprobe was used as anodic luminophore and K 2 S 2 O 8 as cathodic luminophore as well as anodic co-reactant. AuNS with the large specific surface was adopted to adsorb plentiful luminol to form solid-state probe and as affinity support to immobilize ATP aptamer (Apt). The obtained nanocomposite (Apt-AuNS@Lu) generated a strong ECL signal at + 0.4 V (vs. Ag/AgCl) with co-reactant K 2 S 2 O 8 , because of excellent conductivity and catalytic activity of AuNS. Furthermore, graphene oxide was reduced onto indium tin oxide (ITO) electrodes to facilitate the electron transfer. Following, polydopamine (PDA) film was formed via self-polymerization, improving stability and adhesion of the electrode surface. To immobilize ATP capture aptamer (Apt C ), abounding AuNSs were attached to RGO/PDA surface. When the sensor was incubated in the mixture solution of Apt-AuNS@Lu and target ATP, the ECL signal of Apt-AuNS@Lu increased with the increase of ATP concentration, meanwhile, the signal of K 2 S 2 O 8 declined. The ratio of the two luminophores was used for the quantitative determination of ATP. The linear range was 5 to 250 nM, and the limit of detection was 1.4 nM at (3σ)/S. The method was successfully applied to analyze ATP release from HepG2 cells stimulated by 0.45% NaCl hypotonic solution. The results showed that the release kinetics profile of ATP had a sigmoidal shape with rapid release within 10 min and then slowed. Compared to the isotonic groups, the intracellular ATP concentration was 3.7 ± 0.3 µM (n = 3) decreasing by 40.3% and the extracellular was 23.4 ± 1.2 nM (n = 3) increasing by 9.2 times in the hypotonicity for 10 min, which showed ATP release from cells and good agreement with commercial ELISA test. The proposed strategy would be beneficial to broadening application of ECL technology in studying cell biological functions., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The main goal of this work was to modify the previously developed blade-type planar structure using plasmonic gold nanostars in order to stimulate photofield emission and provide efficient laser control of the electron current. Localization and enhancement of the field at the tips of gold nanostars provided a significant increase in the tunneling electron current in the experimental sample (both electrical field and photofield emission). Irradiation at a wavelength in the vicinity of the plasmon resonance (red laser) provided a gain in the photoresponse value of up to 5 times compared to irradiation far from the resonance (green laser). The prospects for transition to regimes of structure irradiation by femtosecond laser pulses at the wavelength of surface plasmon resonance, which lead to an increase in the local optical field, are discussed. The kinetics of the energy density of photoinduced hot and thermalized electrons is estimated. The proposed laser-controlled matrix current source is promising for use in X-ray computed tomography systems.

This study developed a novel surface-enhanced Raman spectroscopy (SERS) method coupled with cellulose nanofiber (CNF)-based SERS wipers that were fabricated on quartz papers coated with a mixture of silver nanoparticle (AgNP) and gold nanostar (AuNS). A "drop-wipe-test" protocol was developed for rapid detection of pesticide residues in vegetables by SERS. Tremendously enhanced Raman scattering signals were obtained from the quartz/CNF/mixture (AgNP + AuNS) substrate, which were much higher than the paper/mixture (AgNP + AuNS) substrate. This method was used to detect ferbam on kale leaves within a few minutes and the detection limit was 50 μg/kg based on the PLS models (R 2  = 0.89). The enhancement factor of the SERS substrate was calculated to be ~ 10 4 with satisfactory reproducibility. Satisfactory SERS performance could be achieved within 1-month storage period. These results demonstrate that this CNF-based SERS/wiper method is a practical approach for rapid detection of chemical contaminants in fresh produce., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

MoS 2 nanosheets were prepared by exfoliating MoS 2 bulk crystals with ultrasonication in N-methylpyrrolidone and were integrated with gold nanostars (AuNS) to fabricate an AuNS/MoS 2 nanocomposite. All nanomaterials were characterized by transmission electron microscope, scanning electron microscope, ultraviolet-visible spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. AuNS/MoS 2 nanocomposites were coated onto a glassy carbon electrode (GCE) surface to construct a nanointerface for immobilizing neuron-specific enolase antibody (anti-NSE) thus forming a photoelectrochemical immunoassay system. AuNS can significantly promote the photoelectric conversion of MoS 2 nanosheets improving the performance for a photoelectrochemical assay. Being illuminated with white light LED and controlling the potential at 0.05 V (vs. SCE), the photocurrent generated from anti-NSE(BSA)/AuNS/MoS 2 /GCE using 0.15 mol L -1 ascorbic acid as electron donor can be recorded with amperometry and used as an output signal for NSE quantitative assay. Under optimized experimental conditions, the photocurrent variation for the affinity-binding NSE is proportional to the logarithm of NSE concentration in the range 5.0 pg mL -1    to 1.5 ng mL -1 with a detection limit of 3.5 pg mL -1 (S/N = 3). The practicability of the PEC immunoassay system was evaluated by determining NSE in clinical serum samples. The recoveries ranged from 93.0 to 103% for the determination of NSE in serum samples with a standard addition method. The PEC immunoassay system possesses good accuracy for determining NSE in real samples. Graphical abstract.

The overexpression of immunomarker programmed cell death protein 1 (PD-1) and engagement of PD-1 to its ligand, PD-L1, are involved in the functional impairment of cluster of differentiation 8 + (CD8 + ) T cells, contributing to cancer progression. However, heterogeneities in PD-L1 expression and variabilities in biopsy-based assays render current approaches inaccurate in predicting PD-L1 status. Therefore, PD-L1 screening alone is not predictive of patient response to treatment, which motivates us to simultaneously detect multiple immunomarkers engaged in immune modulation. Here, we have developed multimodal probes, immunoactive gold nanostars (IGNs), that accurately detect PD-L1 + tumor cells and CD8 + T cells simultaneously in vivo , surpassing the limitations of current immunoimaging techniques. IGNs integrate the whole-body imaging of positron emission tomography with high sensitivity and multiplexing of Raman spectroscopy, enabling the dynamic tracking of both immunomarkers. IGNs also monitor response to immunotherapies in mice treated with combinatorial PD-L1 and CD137 agonists and distinguish responders from those nonresponsive to treatment. Our results showed a multifunctional nanoscale probe with capabilities that cannot be achieved with either modality alone, allowing multiplexed immunologic tumor profiling critical for predicting early response to immunotherapies.

We demonstrated a novel nanocomposite based on fluorescent turn-on gold nanostars for simultaneous tumor targeting photothermal therapy (PTT) and feedback apoptosis imaging of the self-therapeutic effect. In this theranostic agent (AuNS@probe), gold nanostars (AuNSs) and fluorescent dye Atto 655, as a fluorophore/quencher pair, were conjugated to form intermolecular fluorescence quenching in virtue of the linkage of a caspase-3 responsive peptide. Folic acid targeting moiety facilitated the selective accumulation in cancer cells via receptor-mediated endocytosis. Upon photo irradiation, AuNS@probe demonstrated excellent photothermal effect and induced cell death with apoptosis related mechanism. The typical apoptosis-effector proteases, caspase-3, was subsequently activated and terminated intramolecular fluorescent quenching process. Obvious fluorescence recovery could be applied to precisely assess the activated caspase-3 expression and the real time therapeutic efficacy. This novel versatile nanocomposite could serve as a theranostic agent for tumor targeting PTT and also provide self-therapeutic monitoring for precise cancer therapeutic applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Light-triggered nanotheranostics opens a fascinating but challenging avenue to achieve simultaneous and highly efficient anticancer outcomes for multimodal therapeutic and diagnostic modalities. Herein, a multifunctional phototheranostics based on a photosensitizer-assembled graphene/gold nanostar hybrid (GO/AuNS-PEG) was developed for cancer synergistic photodynamic (PDT) and photothermal therapy (PTT) as well as effective photothermal imaging. The stable and biocompatible GO/AuNS-PEG composite displayed a high photothermal conversion efficiency due to the enhanced optical absorbance of both graphene and gold nanostars in the near-infrared (NIR) range. By tuning the absorption wavelength of GO/AuNS-PEG to that of Chlorin e6 (Ce6), GO/AuNS-PEG/Ce6 completely eliminated the EMT6 xenograft tumors by the tremendous synergistic anticancer efficiency of simultaneous PDT and PTT under a single NIR laser irradiation (660nm) in vivo. The underlying mechanism may be the enhanced cytoplasmic uptake and accumulation of GO/AuNS-PEG/Ce6 and the subsequent photodestruction of the lysosomal membrane and mitochondria. Moreover, GO/AuNS-PEG/Ce6 exhibited negligible side-effects on the body and other organs. These results demonstrate that the graphene/gold nanostar nanoconstruct provides a versatile and reliable integrated platform for the photo-controlled cancer theragnostic applications., Statement of Significance: This work demonstrated the application of graphene-Au Nanostars hybridized system (denoted as GO/AuNS-PEG) in single wavelength laser induced synergistic photodynamic (PDT) and photothermal therapy (PTT) and effective cancer photothermal/fluorescence multimode imaging. GO/AuNS-PEG showed excellent biocompatibility and high dual-enhanced photothermal efficiency under the near-infrared laser irradiation that was very promise for deep tumor imaging. By combining with the photosensitizer Chlorin e6, both in vitro and in vivo data confirmed the efficient photoablation of the EMT6 tumors through the synergistic PDT and PTT effect under the activation of a single wavelength laser., (Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Aim: To fabricate multimodal nanoconstruct that act as a single node for photoacoustic imaging (PAI) and photothermal therapy (PTT) in the fight against cancer., Materials & Methods: Dual plasmonic gold nanostars (DPGNS) were chemically synthesized by reducing gold precursor using ascorbic acid and silver ions as shape directing agent. PAI and PTT were performed using commonly available 1064 nm laser source on DPGNS embedded tumor xenografts on mice., Results & Conclusion: Photoacoustic amplitude increase with longer wavelength source and with silica coating of DPGNS. The in vivo photothermal capability of DPGNS resulted in a significant decrease in the tumor cellular area. DPGNS exhibited potential for single node diagnosis and therapy with longer wavelength facilitating deeper imaging and therapy.

In this work, mitochondria-targeting gold nanostar (AuNS) and anticarcinogen DOX were co-encapsulated in hyaluronic acid (HA) protective shell for tumor-targeting synergistic photothermal/chemo-therapy. Cationic peptide R 8 and mitochondria-targeting pro-apoptotic peptide TPP-KLA were co-decorated on AuNS to form AuNS-pep via Au-S bonds. Then, electronegative HA was further coated on the surface via electrostatic interaction for cancer cell targeting. During the coating process, DOX was also introduced via electrostatic interaction to obtain a versatile nanoplatform AuNS-pep/DOX@HA. It was found that the nanoplatform could be internalized into tumor cells via CD44 receptor-mediated recognition. Followed digestion by hyaluronidase (HAase), the therapeutic nanoplatform was able to release DOX for chemotherapy and mitochondria-targeting nanoheater AuNS-pep for near infrared (NIR) light triggered subcellular photothermal therapy (PTT). This tumor-targeting nanoplatform AuNS-pep/DOX@HA displayed prominent non-resistant or resistant tumor inhibition both in vitro and in vivo., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Gold nanoparticles are materials with unique optical properties that have made them very attractive for numerous biomedical applications. With the increasing discovery of techniques to synthesize novel nanoparticles such as star-shaped gold nanoparticles for biomedical applications, the safety and performance of these new nanomaterials must be systematically assessed before use. In this study, gold nanostars (AuNSTs) with multibranched surface structures were synthesized, and their influence on the cytotoxicity of human skin fibroblasts and rat fat pad endothelial cells (RFPECs) were assessed and compared with that of gold nanospheres (AuNSPs) with unbranched surfaces. Results showed that the AuNSPs with diameters of approximately 61.46 nm showed greater toxicity with fibroblast cells and RFPECs compared with the synthesized AuNSTs with diameters of approximately 33.69 nm. The AuNSPs were lethal at concentrations of 40 μg/mL for both cell lines, whereas the AuNSTs were less toxic at higher concentrations (400 μg/mL). The calculated IC50 (50% inhibitory concentration) values of the AuNSPs exposed to fibroblast cells were greater at 1 and 4 days of culture (26.4 and 27.7 μg/mL, respectively) compared with the RFPECs (13.6 and 13.8 μg/mL, respectively), indicating that the AuNSPs have a greater toxicity to endothelial cells. It was proposed that possible factors that could be promoting the reduced toxicity effects of the AuNSTs to fibroblast cells and RFPECs, compared with the AuNSPs may be size, surface chemistry, and shape of the gold nanoparticles. The reduced cell toxicity observed with the AuNSTs suggests that AuNSTs may be a promising material for use in biomedical applications., (© 2015 Wiley Periodicals, Inc.)

Gold nanomaterials promise a wide range of potential applications in chemical and biological sensing, imaging, and catalysis. In this paper, we demonstrate a facile method for room-temperature synthesis of gold nanostars (AuNSs) with a size of ~50 nm via seeded growth. Significantly, the AuNSs are found to have high light-scattering properties, which are successfully used as labels for sensitive and selective detection of nucleic acids and proteins by using exonuclease III (Exo III) as a biocatalyst. For DNA detection, the binding of targets to the functionalized AuNS probes leads to the Exo III-stimulated cascade recycling amplification. As a result, a large amount of AuNSs are released from magnetic nanoparticles (MNPs) into solution, providing a greatly enhanced light-scattering signal for amplified sensing process. Moreover, a binding-induced DNA three-way junction (DNA TWJ) is introduced to thrombin detection, in which the binding of two aptamers to thrombin triggers assembly of the DNA motifs and initiates the subsequent DNA strand displacement reaction (SDR) and Exo III-assisted cascade recycling amplification. The detection limits of 89 fM and 5.6 pM are achieved for DNA and thrombin, respectively, which are comparable to or even exceed that of the reported isothermal amplification methods. It is noteworthy that based on the DNA TWJ strategy the sequences are independent on target proteins. Additionally, the employment of MNPs in the assays can not only simplify the operations but also improve the detection sensitivity. Therefore, the proposed amplified light-scattering assay with high sensitivity and selectivity, acceptable accuracy, and satisfactory versatility of analytes provides various applications in bioanalysis., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The three-dimensional (3D) polarization-dependent optical property is one distinctive characteristic of the anisotropic metal nanoparticles. This has the potential applications in 3D polarization information encryption to detect the polarization information and single particle 3D orientation determination. Previous studies almost focus on the condition that the polarization orientation is in-plane. In the present paper, we systematically investigate the 3D polarization-dependent near- and far-field properties of a kind of fascinating anisotropic nanoparticle, i.e., gold nanostar (AuNS). It shows that the scattering spectra of the AuNS induced by arbitrary incident polarizations can be described as a linear superposition of a set of basic scattering spectra. And we introduce a trigonometric equation to reveal the inherent relationship between the scattering intensity and the 3D polarization orientation, which is universally independent of the size, shape, or surrounding medium of the nanostar. Furthermore, it is facile to synthesize AuNS with two pairs of orthogonal different-length arms, based on the 3D polarization dependence of the scattering trait, and using coordinate transformation, we have demonstrated that such AuNS is useful for designing single particle 3D orientation and rotational tracking sensor and orientation-unlimited polarization information detector. And the self-rotation problem of the gold nanorod, i.e., rotation around the gold nanorod's long axis cannot be resolved, can be solved by replacing it with AuNS. In addition, the precision of the 3D polarization angles and 3D orientation angles confirmed by our method is only with subdegree uncertainty. [ABSTRACT FROM AUTHOR]