Gold-silica quantum rattles for multimodal imaging and therapy.

Gold quantum dots exhibit distinctive optical and magnetic behaviors compared with larger gold nanoparticles. However, their unfavorable interaction with living systems and lack of stability in aqueous solvents has so far prevented their adoption in biology and medicine. Here, a simple synthetic pathway integrates gold quantum dots within a mesoporous silica shell, alongside larger gold nanoparticles within the shell's central cavity. This "quantum rattle" structure is stable in aqueous solutions, does not elicit cell toxicity, preserves the attractive near-infrared photonics and paramagnetism of gold quantum dots, and enhances the drug-carrier performance of the silica shell. In vivo, the quantum rattles reduced tumor burden in a single course of photothermal therapy while coupling three complementary imaging modalities: near-infrared fluorescence, photoacoustic, and magnetic resonance imaging. The incorporation of gold within the quantum rattles significantly enhanced the drug-carrier performance of the silica shell. This innovative material design based on the mutually beneficial interaction of gold and silica introduces the use of gold quantum dots for imaging and therapeutic applications.

Positively Charged Gold Quantum Dots: An Nanozymatic "Off-On" Sensor for Thiocyanate Detection.

The concentration of thiocyanate (SCN-) in bodily fluids is a good indicator of potential and severe health issues such as nasal bleeding, goiters, vertigo, unconsciousness, several inflammatory diseases, and cystic fibrosis. Herein, a visual SCN- sensing method has been developed using the enzyme-like nature of positively charged gold quantum dots (Au QDs) mixed with 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2). This research also reports a new method of synthesizing positively charged Au QDs directly from gold nanoparticles through a hydrothermal process. Microscopic imaging has showed that the Au QDs were 3-5 nm in size, and the emission wavelength was at 438 nm. Au QDs did not display any enzyme-like nature while mixed up with TMB and H2O2. However, the nanozymatic activity of Au QDs appeared when SCN- was included, leading to a very low detection limit (LOD) of 8 nM and 99-105% recovery in complex media. The steady-state kinetic reaction of Au QDs showed that Au QDs had a lower Michaelis-Menten constant (Km) toward H2O2 and TMB, which indicates that the Au QDs had a higher affinity for H2O2 and TMB than horseradish peroxidase (HRP). A mechanism study has revealed that the scavenging ability of hydroxyl (•OH) radicals by the SCN- group plays an important role in enhancing the sensitivity in this study. The proposed nanozymatic "Off-On" SCN- sensor was also successfully validated in commercial milk samples.

High-Performance Wearable Sensor Inspired by the Neuron Conduction Mechanism through Gold-Induced Sulfur Vacancies.

Practical application of wearable gas-sensing devices has been greatly inhibited by the poorly sensitive and specific recognition of target gases. Rapid charge transfer caused by rich sensory neurons in the biological olfactory system has inspired the construction of a highly sensitive sensor network with abundant defect sites for adsorption. Herein, for the first time, we demonstrate an in situ formed neuron-mimic gas sensor in a single gas-sensing channel, which is derived from lattice deviation of S atoms in Bi2S3 nanosheets induced by gold quantum dots. Due to the favorable gas adsorption and charge transfer properties arising from S vacancies, the fabricated sensor exhibits a significantly enhanced response value of 5.6-5 ppm NO2, ultrafast response/recovery performance (18 and 338 s), and excellent selectivity. Furthermore, real-time visual detection of target gases has been accomplished by integrating the flexible sensor into a wearable device.

The effect of gold quantum dots/grating-coupled surface plasmons in inverted organic solar cells.

We studied the effect of gold quantum dots (AuQDs)/grating-coupled surface plasmon resonance (GC-SPR) in inverted organic solar cells (OSCs). AuQDs are located within a GC-SPR evanescent field in inverted OSCs, indicating an interaction between GC-SPR and AuQDs' quantum effects, subsequently giving rise to improvement in the performance of inverted OSCs. The fabricated solar cell device comprises an ITO/TiO2/P3HT : PCBM/PEDOT : PSS : AuQD/silver grating structure. The AuQDs were loaded into a hole transport layer (PEDOT : PSS) of the inverted OSCs to increase absorption in the near-ultraviolet (UV) light region and to emit visible light into the neighbouring photoactive layer, thereby achieving light-harvesting improvement of the device. The grating structures were fabricated on P3HT:PCBM layers using a nanoimprinting technique to induce GC-SPR within the inverted OSCs. The AuQDs incorporated within the strongly enhanced GC-SPR evanescent electric field on metallic nanostructures in the inverted OSCs improved the short-circuit current and the efficiency of photovoltaic devices. In comparison with the reference OSC and OSCs with only green AuQDs or only metallic grating, the developed device indicates enhancement of up to 16% power conversion efficiency. This indicates that our light management approach allows for greater light utilization of the OSCs because of the synergistic effect of G-AuQDs and GC-SPR.

Cold Atmospheric Plasma and Gold Quantum Dots Exert Dual Cytotoxicity Mediated by the Cell Receptor-Activated Apoptotic Pathway in Glioblastoma Cells.

Brain cancer malignancies represent an immense challenge for research and clinical oncology. Glioblastoma is the most lethal form of primary malignant brain cancer and is one of the most aggressive forms commonly associated with adverse prognosis and fatal outcome. Currently, combinations of inorganic and organic nanomaterials have been shown to improve survival rates through targeted drug delivery systems. In this study, we developed a dual treatment approach using cold atmospheric plasma (CAP) and gold quantum dots (AuQDs) for brain cancer. Our results showed that CAP and AuQDs induced dual cytotoxicity in brain cancer cells via Fas/TRAIL-mediated cell death receptor pathways. Moreover, combination treatment with CAP and AuQDs suppressed the motility and sphere-formation of brain cancer cells, which are recognized indicators of cancer aggressiveness. Taken together, the application of AuQDs can improve the efficiency of CAP against brain cancer cells, posing an excellent opportunity for advancing the treatment of aggressive glioblastomas.

Two-Dimensional Gold Quantum Dots with Tunable Bandgaps.

Metallic gold nanoparticles (Au NPs) with multilayer Au atoms are useful for plasmonic, chemical, medical, and metamaterial application. In this article, we report the opening of the bandgap in substrate-supported two-dimensional (2D) gold quantum dots (Au QDs) with monolayer Au atoms. Calculations based on density functional theory suggest that 2D Au QDs are energetically favorable over 3D Au clusters when coated on hexagonal boron nitride (BN) surfaces. Experimentally, we find that BN nanotubes (BNNTs) can be used to stabilize 2D Au QDs on their cylindrical surfaces as well as Au atoms, dimers, and trimers. The electrically insulating and optically transparent BNNTs enable the detection of the optical bandgaps of the Au QDs in the visible spectrum. We further demonstrate that the size and shapes of 2D Au QDs could be atomically trimmed and restructured by electron beam irradiation. Our results may stimulate further exploration of energetically stable, metal-based 2D semiconductors, with properties tunable atom by atom.

A new "turn-on" fluorescent sensor based on gold quantum dots and silver nanoparticles for lamotrigine detection in plasma.

A simple and rapid method for the quantification of lamotrigine (LTG) was developed using 4-aminothiophenol-stabilized gold quantum dots (4-ATP-AuQDs) and amidosulfonic acid-capped silver nanoparticles (ASA-AgNPs) as a new fluorescence resonance energy transfer (FRET) probe. 4-ATP-AuQDs and ASA-AgNPs were synthesized and characterized by UV-Vis and fluorescence spectroscopy, and transmission electron microscopy. Since the emission spectra of 4-ATP-AuQDs have good overlaps with the absorption spectra of ASA-AgNPs, the fluorescence of the AuQDs was significantly quenched in the presence of AgNPs as a result of FRET. However, when LTG was added, a significant fluorescence enhancement was observed owing to the remarkable aggregation of ASA-AgNPs, which could take ASA-AgNPs away from 4-ATP-AuQDs. This method could selectively detect LTG with a detection limit of 4.0ngmL-1 in standard aqueous solution and good linearity was obtained over the range 0.02-0.5µgmL-1 (R=0.9989). The proposed method was successfully applied for the determination of LTG in spiked human plasma samples with a limit of detection of 0.3µgmL-1 and a linear range of 0.5-6.0µgmL-1. The method was also successfully applied to quantify LTG in real plasma samples from epileptic patients receiving LTG.

Demonstration of Calreticulin Expression in Hamster Pancreatic Adenocarcinoma with the Use of Fluorescent Gold Quantum Dots.

BACKGROUND: There is dire need for discovery of novel pancreatic cancer biomarkers and of agents with the potential for simultaneous diagnostic and therapeutic capacity. This study demonstrates calreticulin expression on hamster pancreatic adenocarcinoma via bio-conjugated gold quantum dots (AuQDs). MATERIALS AND METHODS: Hamster pancreatic adenocarcinoma cells were cultured, fixed and incubated with fluorescent AuQDs, bio-conjugated to anti-calreticulin antibodies. Anti-calreticulin and AuQDs were produced in-house. AuQDs were manufactured to emit in the near-infrared. Cells were further characterized under confocal fluorescence. RESULTS: AuQDs were confirmed to emit in the near-infrared. AuQD bio-conjugation to calreticulin was confirmed via dot-blotting. Upon laser excitation and post-incubation with bio-conjugated AuQDs, pancreatic cancer cell lines emitted fluorescence in near-infrared. CONCLUSION: Hamster pancreatic cancer cells express calreticulin, which may be labelled with AuQDs. This study demonstrates the application of nanoparticle-based theranostics in pancreatic cancer. Such biomarker-targeting nanosystems are anticipated to play a significant role in the management of pancreatic cancer.