Facile synthesis of gold nanostars for the duplex detection of pesticide residues in grapes using SERS.

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.

[Remodeling of tumor stroma combined with photothermal therapy in the treatment of triple-negative breast cancer].

Objective: Polyethylene glycol-modified gold nanostar particles (GNS-PEG) were constructed to investigate whether the degradation of extracellular matrix in triple-negative breast cancer could improve the tumor delivery of GNS-PEG and enhance the efficacy of photothermal therapy. Methods: GNS-PEG were constructed and characterized for physicochemical properties as well as photothermal properties. At the cellular level, the cytotoxicity of halofuginone (HF) and the effect of photothermal therapy were detected. Mouse model of triple negative breast cancer was established by subcutaneous inoculation of 4T1 cells in BALB/c nude mice. Five injections of HF were given via tail vein (HF group), and tumor sections were stained with Masson stain and immunohistochemical staining for transforming growth factor ß1 (TGFß1), α-smooth muscle actin (α-SMA) and CD31 to observe the effect of tumor stromal degradation. Five injections of HF via tail vein followed by GNS-PEG (HF+ GNS-PEG group) were applied to determine the content of gold in tumor tissues by inductively coupled plasma mass spectrometry. The tumor sites of the mice in the GNS-PEG and HF+ GNS-PEG groups were irradiated with NIR laser and the temperature changes were recorded with an IR camera. The tumour growth and weight changes of mice in each group were observed. Ki-67 immunohistochemical staining, TdT-mediated dUTP nick-end labeling and HE staining were performed on tumor tissue sections from each group to observe tumor proliferation, apoptosis and necrosis. HE staining was performed on heart, liver, spleen, lung and kidney tissues from each group to observe the morphological changes of cells. Results: GNS-PEG nanoparticles showed a multi-branched structure with a particle size of 73.5±1.4 nm. The absorption peak of GNS was 810 nm, which is in the near infrared region. The photothermal conversion rate of GNS-PEG was up to 79.3%, and the photothermal effect could be controlled by the laser energy. HF has a concentration-dependent cytotoxicity, with a cell survival rate being as low as (22.8±2.6)% at HF concentration of up to 1 000 nmol/L. The photothermal effect of GNS-PEG was significant in killing tumor cells, with a cell survival rate of (32.7±5.2)% at the concentration of 25 pmol/L. The collagen area fraction, TGFß1 integrated optical density and α-SMA integrated optical density in the tumor tissues of mice in the HF group were (2.1±0.2)%, 3.1±0.4 and 5.2±1.9, respectively, which were lower than those of the control group (all P<0.01), and the vessel diameter was 8.6±2.9 µm, which was higher than that of the control group (P<0.05). In the HF+ GNS-PEG group, the concentration of gold in tissues was 52.4 µg/g, higher than that in the GNS-PEG group (15.9 µg/g, P<0.05). After laser irradiation, the temperature of the tumor site in the HF+ GNS-PEG group was significantly higher than that in the GNS-PEG group. At the 4th minute, the temperatures of the tumor site in the GNS-PEG and HF+ GNS-PEG groups were 51.5 ℃ and 57.7 ℃ respectively; the tumor volume in the HF+ GNS-PEG group was effectively suppressed. The body weights of the mice in each group did not change significantly during the monitoring period. No significant abnormalities were observed in the main organs of the mice in the GNS-PEG group, but some hepatocytes in the HF and HF+ GNS-PEG groups showed edema and degeneration. Conclusion: The remodeling of extracellular matrix in triple-negative breast cancer could significantly improve the intratumoral delivery of GNS-PEG and thus achieve better photothermal therapy effect.

Iodide-Mediated Etching of Gold Nanostar for the Multicolor Visual Detection of Hydrogen Peroxide.

A multicolor visual method for the detection of hydrogen peroxide (H2O2) 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 H2O2. Under the optimized conditions, the absorption peak Δλ had a good linear relationship with the concentration of H2O2 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 H2O2 in tap water samples. This method offered a promising visual method for point-of-care testing of H2O2-related biomarkers.

Smartphone-based immunochemical sensor exploiting peroxidase-like activity of ligand-capped gold nanostars: A proof-of-concept detection of Mycobacterium bovis.

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 104 - 106 CFU/mL, enabling detection of M. bovis at concentrations as low as 7.2·103 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.

Nanoplasmonics Enabling Cancer Diagnostics and Therapy.

In this paper, we highlight several advances our laboratory has developed in the pursuit of cancer diagnostics and therapeutics by integrating plasmonics, photonics, and nanotechnology. We discuss the development and applications of plasmonics-active gold nanostar (GNS), a uniquely shaped nanoparticle with numerous branches that serve to greatly amplify the thermal generation at resonant wavelengths. GNS has also been successfully used in tumor imaging contexts from two-photon fluorescence to surface-enhanced Raman scattering (SERS) sensing and imaging. Finally, GNS has been coupled with immunotherapy applications to serve as an effective adjuvant to immune checkpoint inhibitors. This combination of GNS and immunotherapy, the so called synergistic immuno photo nanotherapy (SYMPHONY), has been shown to be effective at controlling long-lasting cancer immunity and metastatic tumors.

Nanostars Carrying Multifunctional Neurotrophic Dendrimers Protect Neurons in Preclinical In Vitro Models of Neurodegenerative Disorders.

A challenge in neurology is the lack of efficient brain-penetrable neuroprotectants targeting multiple disease mechanisms. Plasmonic gold nanostars are promising candidates to deliver standard-of-care drugs inside the brain but have not been trialed as carriers for neuroprotectants. Here, we conjugated custom-made peptide dendrimers (termed H3/H6), encompassing motifs of the neurotrophic S100A4-protein, onto star-shaped and spherical gold nanostructures (H3/H6-AuNS/AuNP) and evaluated their potential as neuroprotectants and interaction with neurons. The H3/H6 nanostructures crossed a model blood-brain barrier, bound to plasma membranes, and induced neuritogenesis with the AuNS, showing higher potency/efficacy than the AuNP. The H3-AuNS/NP protected neurons against oxidative stress, the H3-AuNS being more potent, and against Parkinson's or Alzheimer's disease (PD/AD)-related cytotoxicity. Unconjugated S100A4 motifs also decreased amyloid beta-induced neurodegeneration, introducing S100A4 as a player in AD. Using custom-made dendrimers coupled to star-shaped nanoparticles is a promising route to activate multiple neuroprotective pathways and increase drug potency to treat neurodegenerative disorders.

Ratiometric ECL sensor based on Apt-AuNS@Lu nanoprobe for analyzing cell swelling-induced ATP release.

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 K2S2O8 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 K2S2O8, 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 (AptC), 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 K2S2O8 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.

Electrochemical Biosensor Based on l-Arginine and rGO-AuNSs Deposited on the Electrode Combined with DNA Probes for Ultrasensitive Detection of the Gastric Cancer-Related PIK3CA Gene of ctDNA.

Gene biomarkers of circulating tumor DNA (ctDNA) in liquid biopsies have been explored for use in the precise diagnosis of tumors. There is a great clinical need to realize the ultrasensitive detection of gene biomarkers in ctDNA. Here we reported that an ultrasensitive label-free biosensor was developed for the detection of the gastric cancer-related PIK3CA gene of ctDNA in peripheral blood. The polymeric l-arginine and graphene oxide-wrapped gold nanostars (rGO-AuNSs) were prepared and deposited on the glass electrode. The capturing DNA probes for the PIK3CA gene were prepared and successfully immobilized on the rGO-AuNS-modified electrode surface via π-π interaction among the rGO-AuNS composites and DNA probes. The resultant electrochemical sensor was effectively applied to detect the PIK3CA gene of ctDNA via the hybridization between the capturing DNA probe and ctDNA, the result of which showed that the biosensor exhibited desirable sensitivity, stability, and a wider dynamic response in a ctDNA concentration range from 1.0 × 10-20 to 1.0 × 10-10 M (R2 = 0.997). Moreover, the low limit of detection of 1.0 × 10-20 M (S/N = 3) indicates the biosensor owns satisfactory detection sensitivity. Fourteen PIK3CA genes and two PIK3CA gene mutations were detected in 60 clinical ctDNA samples of gastric cancer patients by using the developed biosensor. In conclusion, this ultrasensitive label-free electrochemical biosensor possesses a significant application prospect in the detection of the PIK3CA gene in ctDNA and in early screening for gastric cancer in the near future.

The Effect of Capping Agents on Gold Nanostar Stability, Functionalization, and Colorimetric Biosensing Capability.

Capping agents (organic ligands, polymers, and surfactants) are pivotal for stabilizing nanoparticles; however, they may influence the surface chemistry, as well as the physico-chemical and biological characteristics, of gold nanostar (AuNS)-based biosensors. In this study, we proved that various capping agents affected capped and bioconjugated AuNS stability, functionality, biocatalysis, and colorimetric readouts. Capped and bioconjugated AuNSs were applied as localized surface plasmon resonance (LSPR)-based H2O2 sensors using glucose oxidase (GOx) as a model enzyme. Furthermore, our analyses revealed that the choice of capping agent influenced the properties of the AuNSs, their stability, and their downstream applications. Our analyses provide new insights into factors governing the choice of capping agents for gold nanostars and their influences on downstream applications with conjugated enzymes in confined environments.

Photoemission of Plasmonic Gold Nanostars in Laser-Controlled Electron Current Devices for Technical and Biomedical Applications.

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.

Synergistic photothermal-photodynamic-chemotherapy toward breast cancer based on a liposome-coated core-shell AuNS@NMOFs nanocomposite encapsulated with gambogic acid.

A multifunctional nanoplatform with core-shell structure was constructed in one-pot for the synergistic photothermal, photodynamic, and chemotherapy against breast cancer. In the presence of gambogic acid (GA) as the heat-shock protein 90 (HSP90) inhibitor and the gold nanostars (AuNS) as the photothermal reagent, the assembly of Zr4+ with tetrakis (4-carboxyphenyl) porphyrin (TCPP) gave rise to the nanocomposite AuNS@ZrTCPP-GA (AZG), which in turn, further coated with PEGylated liposome (LP) to enhance the stability and biocompatibility, and consequently the antitumor effect of the particle. Upon cellular uptake, the nanoscale metal - organic framework (NMOF) of ZrTCPP in the resulted AuNS@ZrTCPP-GA@LP (AZGL) could be slowly degraded in the weak acidic tumor microenvironment to release AuNS, Zr4+, TCPP, and GA to exert the synergistic treatment of tumors via the combination of AuNS-mediated mild photothermal therapy (PTT) and TCPP-mediated photodynamic therapy (PDT). The introduction of GA serves to reduce the thermal resistance of the cell to re-sensitize PTT and the constructed nanoplatform demonstrated remarkable anti-tumor activity in vitro and in vivo. Our work highlights a facile strategy to prepare a pH-dissociable nanoplatform for the effective synergistic treatment of breast cancer.

Multimodal Imaging-Guided Spatiotemporal Tracking of Photosensitive Stem Cells for Breast Cancer Treatment.

Stem cell therapy has shown great potential in treating a wide range of diseases including cancer. The real-time tracking of stem cells with high spatiotemporal resolution and stable imaging signals remains the bottleneck to evaluate and monitor therapeutic outcomes once transplanted into patients. Here, we developed a photosensitive mesenchymal stem cell (MSC) loaded with mesoporous silica-coated gold nanostars (MGNSs) integrated with indocyanine green for spatiotemporal tracking and imaging-guided photothermal therapy (PTT) in treating breast cancers. The MGNS served as a stable imaging probe with multifunctional properties for photoacoustic imaging (PAI), fluorescence imaging, and PT imaging. Owing to the excellent PT stability of MGNSs, long-term three-dimensional (3D) PAI was achieved to monitor stem cells in real time at the tumor site, while the tumor structure was imaged using 3D B-mode ultrasound imaging. PAI revealed that the photosensitive stem cells reached the widest distribution area at the tumor site post 24 h of intratumoral injection, which was further confirmed via two-dimensional (2D) PT and fluorescence imaging. With this optimal cell distribution window, in vivo studies showed that the photosensitive stem cells via both intratumoral and intravenous injections successfully inhibited breast cancer cell growth and decreased the tumor recurrence rate post PTT. Our results support that this photo-integrated platform with stable optical properties is promising to achieve real-time tracking and measure the cell distribution quantitatively with high spatiotemporal resolution for stem cell therapy.

Fast synthesis of gold nanostar SERS substrates based on ion-track etched membrane by one-step redox reaction.

Surface-enhanced Raman scattering (SERS), due to its high detecting sensitivity and rapid data acquisition ability, has been considered as a powerful technique for label-free ultrasensitive detection of chemical and biochemical analytes. As an important part, the uniform SERS substrate is the prerequisite for this technology being used in all the related areas. Therefore, seeking the fast, convenient and low-cost way to obtain the SERS substrate with high performance and reproducibility never stops in recent decades. In this work, the PC membrane with uniform nanopores obtained by ion irradiation and chemical etching (i.e., ion-track etched PC membrane) was first used to prepare the gold nanostar SERS substrate. The monolayer gold nanostars can be obtained through a one-step redox reaction on the surface of the PC membrane, which not only can act as the base of SERS substrate but also can work as the reaction adjuster. By optimizing the growth conditions, the SERS substrate with uniform monolayer gold nanostars can be fabricated without any complicated procedures and costly equipment fast (in 20 mins). Meanwhile, the prepared flexible gold nanostar SERS substrate exhibits excellent Raman performance, which can effectively detect the analyte R6G with the concentration as low as 1 × 10-10 M and the SERS enhancement factors can be around 3.70 × 105. The new facile SERS substrate preparation method is cost-effective, convenient, fast and easily scale up, which can satisfy the requests of the real applications in many fields.

Design and synthesis of gold nanostars-based SERS nanotags for bioimaging applications.

Surface-enhanced Raman spectroscopy (SERS) nanotags hold a unique place among bioimaging contrast agents due to their fingerprint-like spectra, which provide one of the highest degrees of detection specificity. However, in order to achieve a sufficiently high signal intensity, targeting capabilities, and biocompatibility, all components of nanotags must be rationally designed and tailored to a specific application. Design parameters include fine-tuning the properties of the plasmonic core as well as optimizing the choice of Raman reporter molecule, surface coating, and targeting moieties for the intended application. This review introduces readers to the principles of SERS nanotag design and discusses both established and emerging protocols of their synthesis, with a specific focus on the construction of SERS nanotags in the context of bioimaging and theranostics.

Development of surface-enhanced Raman scattering-based immunoassay platforms using hollow Au nanostars for reliable SARS-CoV-2 diagnosis.

We developed a novel surface-enhanced Raman scattering (SERS)-based SARS-CoV-2 assay platform using hollow Au nanostars to realize high-sensitivity diagnosis of SARS-CoV-2. The assay was performed using SARS-CoV-2 lysate as the target in a wide dynamic range with virus concentrations ranging from 0 to 104 PFU/ml and has a limit of detection (LOD) of 5.1 PFU/ml. This LOD value shows 100 times and 10 times better sensitivity compared to the LODs measured on the same sample using a commercially available rapid kit and enzyme-linked immunosorbent assay, respectively. Therefore, we believe that this SERS-based SARS-CoV-2 assay platform has high diagnostic accuracy for early or asymptomatic infected patients with low virus concentrations. Furthermore, the probability of a false-negative diagnosis is likely to be very low.

Gold nanostar as an ultrasensitive colorimetric probe for picomolar detection of lead ion.

The sensitivity for analytes of interest is vital for environment protection and food safety. Here, we propose an extremely sensitive assay toward Pb2+ by using gold nanostars (GNSs) as probes based on the catalytic activity of Pb on etching gold atoms after being reduced in the presence of 2-mercaptoethanol (2-ME) and sodium thiosulfate. GNSs were prepared by using 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid as both the reducing and capping agents, enabling high stability and sensitivity for quantitation of Pb2+. Upon increasing Pb2+ concentration over the range of 0-10 µM, GNS solution color changed from greenish-blue to blue to purple to red, and eventually to colorless. The color change can be distinguished by naked eye at the Pb2+ concentration as low as 200 pM. Through monitoring longitudinal localized surface plasmon of GNSs, Pb2+ could be detected with a limit of detection of 1.5 pM, and the working range is 2 pM-1 µM. The ultra-high sensitivity of our assay stems from the high catalysis of Pb on etching gold on tips and branches in the presence of 2-ME and sodium thiosulfate, leading to the shape deformation to spherical gold nanoparticle and the corresponding significant changes in their optical properties. The assay provides high selectivity of Pb2+ over the tested interfering metal ions like Cu2+. With high sensitivity and selectivity, the assay was efficiently validated by analyzing water samples and monitoring the migration of Pb2+ from the tested container to water.

Modeling of Laser-Induced Plasmon Effects in GNS-DLC-Based Material for Application in X-ray Source Array Sensors.

An important direction in the development of X-ray computed tomography sensors in systems with increased scanning speed and spatial resolution is the creation of an array of miniature current sources. In this paper, we describe a new material based on gold nanostars (GNS) embedded in nanoscale diamond-like carbon (DLC) films (thickness of 20 nm) for constructing a pixel current source with photoinduced electron emission. The effect of localized surface plasmon resonance in GNS on optical properties in the wavelength range from UV to near IR, peculiarities of localization of field and thermal sources, generation of high-energy hot electrons, and mechanisms of their transportation in vacuum are investigated. The advantages of the proposed material and the prospects for using X-ray computed tomography in the matrix source are evaluated.

Development of cellulose Nanofiber-based substrates for rapid detection of ferbam in kale by Surface-enhanced Raman spectroscopy.

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 (R2 = 0.89). The enhancement factor of the SERS substrate was calculated to be ~ 104 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.

Photoelectrochemical immunoassay platform based on MoS2 nanosheets integrated with gold nanostars for neuron-specific enolase assay.

MoS2 nanosheets were prepared by exfoliating MoS2 bulk crystals with ultrasonication in N-methylpyrrolidone and were integrated with gold nanostars (AuNS) to fabricate an AuNS/MoS2 nanocomposite. All nanomaterials were characterized by transmission electron microscope, scanning electron microscope, ultraviolet-visible spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. AuNS/MoS2 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 MoS2 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/MoS2/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.

Stellate Plasmonic Exosomes for Penetrative Targeting Tumor NIR-II Thermo-Radiotherapy.

Multifunctional gold (Au)-based nanomaterials with high atomic number (symbol Z) and strong absorbance in the second near-infrared window (NIR-II) property are emerging as promising candidates for tumor thermo-radiotherapy. The main limitations of applying Au-based nanomaterials to biomedical studies include the absence of active tumor-targeting ability, penetrating efficiency, and stability. In this study, we present a novel type of tumor cell-derived stellate plasmonic exosomes (TDSP-Exos) for penetrative targeted tumor NIR-II thermo-radiotherapy and photoacoustic imaging. The TDSP-Exos are abundantly and easily produced by the incubation of tumor cells with gold nanostars, based on which gold nanostars promote the exocytosis of exosomes from tumor cells. Compared with bare gold nanostars, the TDSP-Exos exhibit pronounced accumulation in deep tumor tissues and perform well in both PA imaging and NIR-II thermo-radiotherapy against the tumor. Moreover, the TDSP-Exos improve tumor hypoxia to enhanced radiotherapy by NIR-II photothermal therapy. This work indicates that the tumor cell-derived exosomes have the potential to function as a universal carrier of photothermal agents for targeted tumor NIR-II thermo-radiotherapy.