Peptide-mediated Aqueous Synthesis of NIR-II Emitting Ag2 S Quantum Dots for Rapid Photocatalytic Bacteria Disinfection.

Pathogenic microorganisms in the environment are a great threat to global human health. The development of disinfection method with rapid and effective antibacterial properties is urgently needed. In this study, a biomimetic silver binding peptide AgBP2 was introduced to develop a facile synthesis of biocompatible Ag2 S quantum dots (QDs). The AgBP2 capped Ag2 S QDs exhibited excellent fluorescent emission in the second near-infrared (NIR-II) window, with physical stability and photostability in the aqueous phase. Under 808 nm NIR laser irradiation, AgBP2-Ag2 S QDs can serve not only as a photothermal agent to realize NIR photothermal conversion but also as a photocatalyst to generate reactive oxygen species (ROS). The obtained AgBP2-Ag2 S QDs achieved a highly effective disinfection efficacy of 99.06 % against Escherichia coli within 25 min of NIR irradiation, which was ascribed to the synergistic effects of photogenerated ROS during photocatalysis and hyperthermia. Our work demonstrated a promising strategy for efficient bacterial disinfection.

Ultrasmall Pb:Ag2 S Quantum Dots with Uniform Particle Size and Bright Tunable Fluorescence in the NIR-II Window.

Ag2 S quantum dots (QDs) are well-known near-infrared fluorophores and have attracted great interest in biomedical labeling and imaging in the past years. However, their photoluminescence efficiency is hard to compete with Cd-, Pb-based QDs. The high Ag+ mobility in Ag2 S crystal, which causes plenty of cation deficiency and crystal defects, may be responsible mainly for the low photoluminescence quantum yield (PLQY) of Ag2 S QDs. Herein, a cation-doping strategy is presented via introducing a certain dosage of transition metal Pb2+ ions into Ag2 S nanocrystals to mitigate this intrinsic shortcoming. The Pb-doped Ag2 S QDs (designated as Pb:Ag2 S QDs) present a renovated crystal structure and significantly enhanced optical performance. Moreover, by simply adjusting the levels of Pb doping in the doped nanocrystals, Pb:Ag2 S QDs with bright emission (PLQY up to 30.2%) from 975 to 1242 nm can be prepared without altering the ultrasmall particle size (≈2.7-2.8 nm). Evidently, this cation-doping strategy facilitates both the renovation of crystal structure of Ag2 S QDs and modulation of their optical properties.

Fluorescent Detection of Phosphate in Aqueous Solution Based on Near Infrared Emission Ag2S QDs/Metal - Organic Shell Composite.

A novel fluorescence method for sensitive and selective detection of phosphate was developed based on near infrared emission Ag2S QDs/ Metal - Organic Shell Composite via the deposition of metal-organic (zinc-nitrogen) coordination shell around Ag2S QDs . Under optimal conditions described, the fluorescence intensity of the composite was decreased at 685 nm in the presence of phosphate, which was linearly related to the concentration of phosphate in the range of 0. 7 to 4.2 µM and 11.2 to 88.2 µM with the relative correlation coefficient of R2 = 0.998 and 0.987 respectively and detection limit as low as 6 nM. In addition, the proposed method was successfully utilized in serum samples, tap water and Yangtze River water samples with the recoveries ranged from 94.76 to 100.86 %, which presaged more opportunities for application in related bioassay and water sample researches.

Preoperative Detection and Intraoperative Visualization of Brain Tumors for More Precise Surgery: A New Dual-Modality MRI and NIR Nanoprobe.

In clinical practice, it is difficult to identify tumor margins during brain surgery due to its inherent infiltrative character. Herein, a unique dual-modality nanoprobe (Gd-DOTA-Ag2S QDs, referred as Gd-Ag2S nanoprobe) is reported, which integrates advantages of the deep tissue penetration of enhanced magnetic resonance (MR) imaging of Gd and the high signal-to-noise ratio and high spatiotemporal resolution of fluorescence imaging in the second near-infrared window (NIR-II) of Ag2S quantum dots (QDs). Due to the abundant tumor angiogenesis and the enhanced permeability and retention effect in the tumor, a brain tumor (U87MG) in a mouse model is clearly delineated in situ with the help of the Gd assisted T1 MR imaging and the intraoperative resection of the tumor is precisely accomplished under the guidance of NIR-II fluorescence imaging of Ag2S QDs after intravenous injection of Gd-Ag2S nanoprobe. Additionally, no histologic changes are observed in the main organs of the mouse after administration of Gd-Ag2S nanoprobe for 1 month, indicating the high biocompatibility of the nanoprobe. We expect that such a novel "Detection and Operation" strategy based on Gd-Ag2S nanoprobe is promising in future clinical applications.

Polyvalent Aptamer-Functionalized NIR-II Quantum Dots for Targeted Theranostics in High PD-L1-Expressing Tumors.

Ag2S quantum dots (QDs) show superior optical properties in the NIR-II region and display significant clinical potential with favorable biocompatibility. However, inherent defects of low targeting and poor solubility necessitate practical modification methods to achieve the theranostics of Ag2S QDs. Herein, we used rolling circle amplification (RCA) techniques to obtain long single-stranded DNA containing the PD-L1 aptamer and C-rich DNA palindromic sequence. The C-rich DNA palindromic sequences can specifically chelate Ag2+ and thus serve as a template to result in biomimetic mineralization and formation of pApt-Ag2S QDs. These QDs enable specific targeting and illuminate hot tumors with high PD-L1 expression effectively, serving as excellent molecular targeted probes. In addition, due to the high NIR-II absorption of Ag2S QDs, pApt-Ag2S QDs exhibit remarkable photothermal properties. And besides, polyvalent PD-L1 aptamers can recognize PD-L1 protein and effectively block the inhibitory signal of PD-L1 on T cells, enabling efficient theranostics through the synergistic effect of photothermal therapy and immune checkpoint blocking therapy. Summary, we enhance the biological stability and antibleaching ability of Ag2S QDs using long single-stranded DNA as a template, thereby establishing a theranostic platform that specifically targets PD-L1 high-expressing inflamed tumors and demonstrates excellent performance both in vitro and in vivo.

0D/2D heterojunction constructed by Ag2S quantum dots anchored on graphdiyne (g-CnH2n-2) nanosheets for wide spectrum photocatalytic H2 evolution.

Precisely crafting heterojunctions for efficient charge separation is a major obstacle in the realm of photocatalytic hydrogen evolution. A 0D/2D heterojunction was successfully fabricated by anchoring Ag2S quantum dots (Ag2S QDs) onto graphdiyne (GDY) nanosheets (Ag2S QDs/GDY) using a straightforward physical mixing technique. This unique structure allows for excellent contact between GDY and Ag2S QDs, thereby enhancing the rate of charge transfer. The light absorption capabilities of Ag2S QDs/GDY extend up to 1200 nm, enabling strong absorption of light, including infrared. Through DFT calculations and in-situ XPS analysis, it was demonstrated that incorporating Ag2S QDs onto GDY effectively modulates the electronic structure, promotes an internal electric field, and facilitates directional electron transfer. This directed electron transfer enhances the utilization of electrons by GDY and Ag2S QDs, with the added benefit of Ag2S QDs serving as electron reservoirs for efficient photocatalytic hydrogen evolution. A 7 %Ag2S QDs/GDY composite exhibited impressive efficiency and stable performance in photocatalytic hydrogen evolution (2418 µmol g-1 h-1), which is much higher than that of GDY and Ag2S QDs. This study conclusively demonstrates that the 0D/2D heterojunction formed by GDY and Ag2S QDs can establish high-quality contact and efficient charge transfer, ultimately enhancing photocatalytic performance.

Cerasome Versus Liposome: A Comparative Pharmacokinetic Analysis Following Intravenous Administration into Rats.

Background: Cerasomes, due to their external siloxane network, demonstrate markedly higher physicochemical stability and, therefore, easier handling and storage than liposomes. Objectives: The main objective of this study was to compare the pharmacokinetics (PK) of cerasome and liposome following intravenous administration. The PK of PEGylated and non-PEGylated cerasomes was also compared to see whether the presence of a hydrophilic siloxane network on the surface of cerasomes can play the role of polyethylene glycol (PEG) in increasing the blood circulation of these vesicles. Methods: Silver sulfide (Ag2S) quantum dots (Qds)-loaded PEGylated and non-PEGylated cerasomes and PEGylated liposomes were fabricated and thoroughly characterized in terms of particle size, polydispersity index, zeta potential, entrapment efficiency, and in vitro stability. For pharmacokinetic evaluation, the free Qds and the selected formulations were intravenously injected into rats, and blood samples were collected for up to 72 hours. Pharmacokinetic parameters were calculated by the non-compartmental method. Results: Both cerasomal and liposomal carriers significantly improved the PK of Qds. For example, the elimination half-life (t1/2) and the area under the plasma concentration-time curve from time 0 to time infinity (AUC0-∞) for the free Qds were 4.39 h and 8.01 µg/mL*h and for cerasomal and liposomal formulations were 28.82 versus 26.95 h and 73.25 versus 62.02 µg/mL*h, respectively. However, compared to each other, the plasma concentration-time profiles of PEGylated cerasomes and liposomes displayed similar patterns, and the statistical comparison of their pharmacokinetic parameters did not show any significant difference between the two types of carriers. For PEGylated cerasomes, t1/2 and AUC0-∞ values were respectively 1.6 and 3.3 times greater than the classic cerasome, indicating that despite the presence of a hydrophilic siloxane network, the incorporation of PEG is necessary to reduce the clearance of cerasomes. Conclusions: The comparable PK of PEGylated cerasomes and liposomes, along with the higher physicochemical stability of cerasomes, can be considered an important advantage for the clinical application of cerasomes. Additionally, the easy surface functionalizing ability of cerasomes confers a dual advantage over liposomes. The study findings also showed that the presence of a hydrophilic siloxane network on the surface of cerasomes alone is not enough to make them circulate long.

Ultrasonic enhancement of microdroplet-based interfacial reaction for improving the synthesis of Ag2S QDs.

Ag2S quantum dots (QDs) have aroused extensive concerns in intravital imaging field due to their merits of narrow bandgap, low biological toxicity and decent fluorescence emission properties in the second near-infrared (NIR-II) window. However, low quantum yield (QY) and poor uniformity of Ag2S QDs are still main obstacles for its application. In this work, a novel strategy of utilizing ultrasonic field is presented, which can enhance the microdroplet-based interfacial synthesis of Ag2S QDs. The ultrasound increases the presence of ions at the reaction sites by enhancing the ion mobility in the microchennels. Therefore, the QY is enhanced from 2.33 % (optimal QY without ultrasound) to 8.46 %, which is the highest value of Ag2S ever reported without ion-doping. Also, the decrease of the corresponding full width at half maximum (FWHM) from 312 nm to 144 nm indicates the obvious uniformity improvement of the obtained QDs. Further mechanism exploration illustrates that ultrasonic cavitation significantly increases the interfacial reaction sites by splitting the droplets. Meanwhile, the acoustic flow field strengthens the ion renewal at the droplet interface. Consequently, the mass transfer coefficient increases by more than 500 %, which is favorable to improve both the QY and quality of Ag2S QDs. This work serves both fundamental research and practical production for the synthesis of Ag2S QDs.

Efficient detection for Nitrofurazone based on novel Ag2S QDs/g-C3N4 fluorescent probe.

In the paper, a novel fluorescent probe based on Ag2S QDs/g-C3N4 composite was synthesized by loading Ag2S quantum dots (Ag2S QDs) on the surface of g-C3N4 through in-situ synthesis method and developed to detect Nitrofurazone (NFZ) sensitively. The results showed that the linear detection range of Ag2S QDs/g-C3N4 to NFZ was 0-30 µM, with a low detection limit of 0.054 µM. The results of time-fluorescence-resolved spectroscopy and UV-vis absorption spectroscopy exhibited that the possible detection mechanism of Ag2S QDs/g-C3N4 to NFZ was proposed to be Internal Filtration Effect (IFE). Moreover, Multiwfn wavefunction analysis was employed to uncover the possible interaction between the Ag2S QDs/g-C3N4 and NFZ, thereby further revealing the fluorescence detection mechanism from the scale of atoms. Combining experiments and theoretical calculations, we proposed the sensing mechanism of the formation of non-fluorescent ground state complex linked by hydrogen bonds. This work indicated that the Ag2S QDs/g-C3N4 composite processed the ability to detect NFZ efficiently and sensitively.

Synthesis and Bioapplications of Ag2 S Quantum Dots with Near-Infrared Fluorescence.

Quantum dots (QDs) with near-infrared fluorescence (NIR) are an emerging class of QDs with unique capabilities owing to the deeper tissue penetrability of NIR light compared with visible light. NIR light also effectively overcomes organism autofluorescence, making NIR QDs particularly attractive in biological imaging applications for disease diagnosis. Considering latest developments, Ag2 S QDs are a rising star among NIR QDs due to their excellent NIR fluorescence properties and biocompatibility. This review presents the various methods to synthesize NIR Ag2 S QDs, and systematically discusses their applications in biosensing, bioimaging, and theranostics. Major challenges and future perspectives concerning the synthesis and bioapplications of NIR Ag2 S QDs are discussed.

In vitro interaction of glutathione S-transferase-pi enzyme with glutathione-coated silver sulfide quantum dots: A novel method for biodetection of glutathione S-transferase enzyme.

Quantum dots (QD) are being evaluated as inorganic nanoparticles for both in vitro and in vivo optical imaging. They are also used as sensors or vehicles for targeted drug delivery combined with optical imaging. In this study, we demonstrated that glutathione-coated Ag2 S QDs (GSH-Ag2 S QDs) act as a substrate analogue of glutathione S-transferase (GST) enzymes for the first time in the literature. The GSTs belong to a major group of detoxification enzymes involved in the detoxification metabolism responsible for the protection of cells against reactive oxygen species (ROS) or electrophiles. GST isozymes are impaired in the various diseases such as neurological diseases and cancer. We evaluated the interaction of GST-pi enzyme with GSH-Ag2 S QDs, which have never been studied in the literature before, using both fluorometric and spectrophotometric methods. Our data showed that GSH-Ag2 S QDs gave reaction with GST enzyme as a substrate analogue. In conclusion, our data may help to guide researchers for further development of sensing systems for GST activity which is impaired in various diseases including cancer.