AuNCs-Catalyzed Hydrogen Selenide Oxidation: Mechanism and Application for Headspace Fluorescent Detection of Se(IV)

The excellent fluorescence property of Au nanoclusters (AuNCs) has received great attention for various chemosensing and biorelated applications, but the sample matrix is still an important problem that causes undesirable fluorescence variation. On the one hand, hydride generation (HG) is an effective strategy to separate the target analyte from the complex sample matrices, but the implementation of HG with AuNC-based fluorescent assays was not realized. On the other hand, due to the ultrasmall size of AuNCs and good catalytic performance of Au, AuNCs are also featuring intriguing catalytic applications. Herein, we proposed a new type of AuNC-based fluorescence assay for Se(IV) detection, in which hydride generation of Se(IV) was coupled with the fluorescence/catalytic dual functions of AuNCs. In a batch hydride generation mode, Se(IV) was first converted to volatile H₂Se. When it spread in the headspace to contact with AuNCs supported paper, AuNC-catalyzed oxidation of H₂Se by O₂ to yield elemental selenium occurred, which further deposited on the surface of AuNCs to induce fluorescence quenching. The catalytic effect of AuNCs was studied in depth via both experimental and theoretical (density functional theory) investigations. Three main steps for H₂Se oxidation were identified, with energy barriers in the presence of AuNCs significantly lower than those without. Benefiting from the reduced matrix interference by hydride generation and the unique catalysis/fluorescence of AuNCs, the proposed assay featured high selectivity, good sensitivity, and simplicity, with successful applications for selenium detection in real samples.

miR-25 Mediates Retinal Degeneration Via Inhibiting ITGAV and PEDF in Rat

BACKGROUND

Age-related macular degeneration (AMD) is the main cause of irreversible blindness in the elderly. Oxidative stress in retinal pigment epithelium (RPE) is deemed to play a pivotal role in the pathogenesis of AMD. miR-25 functions as an essential modulator in response to oxidative-stress in several cell types, but its function in RPE cells is poorly understood.

OBJECTIVE

To explore the roles of miR-25 in RPE cells and in the development of AMD.

METHODS

A rat model of retinal degeneration was induced by sodium iodate (SI). Subretinal injection of antagomiR-25 was performed for the intervention while the scramble as control. Visual responses were recorded with Electroretinogram (ERG). TUNEL assay was performed to detect apoptosis. Phagosome quantification in vivo was performed to evaluate RPE cell function. Oxygen-glucose deprivation treatment was performed to mimic in vitro oxidative stress. Gene expression at mRNA level and protein level were performed by quantitative polymerase chain reaction (qPCR) and Western Blot, respectively. The pigment epithelium derived factor (PEDF) level in the cultured medium was measured by Enzyme-linked immunosorbent assay (ELISA). The interaction between miR-25 and integrin αV (IGTAV) / PEDF 3'UTR was examined by dual luciferase assay. Chromatin immunoprecipitation (ChIP) assay was performed to examine its transcriptional regulation of miR-25.

RESULTS

Oxidative stress up-regulated miR-25 in RPE cells in very early stage, accompanied by decreased phagocytosis and reduced growth factor secretion in those cells. Such changes preceded RPE cell apoptosis and visual impairment in the SItreated rats. Furthermore, antagomiR-25 intervention effectively rescued RPE cells from degeneration in such model. The increased miR-25 was confirmed to mediate RPE degeneration through direct targeting IGTAV and PEDF. On the other hand, upstream, miR-25 was found to be up-regulated by STAT3 signaling under oxidative stress in both in vivo and in vitro models.

CONCLUSION

Our findings demonstrate that, in SI-treated rats, oxidative stress activates STAT3 signaling which up-regulates miR-25 expression, in a very early stage. The increased miR-25 then inhibits ITGAV and PEDF expressions, resulting in RPE phagocytosis dysfunction and then RPE apoptosis and visual impairment as observed in patients with AMD. These findings lead us to a better understanding of AMD pathogenesis, and suggest that miR-25 could be a potential therapeutic target for oxidative stress related RPE diseases, like AMD.

The recruitment of extra-intestinal cells to the injured mucosa promotes healing in radiation enteritis and chemical colitis in a mouse parabiosis model

Mucosal healing occurs through migration and proliferation of cells within injured epithelium, yet these processes may be inadequate for mucosal healing after significant injury where the mucosa is denuded. We hypothesize that extra-intestinal cells can contribute to mucosal healing after injury to the small and large intestine. We generated parabiotic pairs between wild-type and tdTomato mice, which were then subjected to radiation-induced enteritis and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. We now show that as compared with singleton mice, mice with a parabiotic partner were protected against intestinal damage as revealed by significantly reduced weight loss, reduced expression of pro-inflammatory cytokines, reduced enterocyte apoptosis, and improved crypt proliferation. Donor cells expressed CD45-, Sca-1+, c-kit+, and CXCR4+ and accumulated around the injured crypts but did not transdifferentiate into epithelia, suggesting that extra-intestinal cells play a paracrine role in the healing response, while parabiotic pairings with Rag1-/- mice showed improved healing, indicating that adaptive immune cells were dispensable for mucosal healing. Strikingly, ablation of the bone marrow of the donor parabionts removed the protective effects. These findings reveal that the recruitment of extra-intestinal, bone marrow-derived cells into the injured intestinal mucosa can promote mucosal healing, suggesting novel therapeutic approaches for severe intestinal disease.

Analysis of radioactive waste generated during the cyclotron production of 99mTc

Past and prospective shortages of medical radioisotopes have driven recent developments in the direct production of ^99mTc via the ¹⁰⁰Mo(p,2n)^99mTc reaction. The cyclotron-based production method has been shown to successfully produce ^99mTc, however trace impurities present in the enriched molybdenum target can also lead to the unintended creation of other radioisotopes which constitute waste. The isotopic composition of the waste has to be investigated in order to determine how it can be handled, transported and safely stored. In this article, we report which waste radioisotopes are created alongside ^99mTc during target irradiation. Results are based on the gamma spectroscopy of waste produced. Significant complexities in the emission spectra made automated identification of radioisotopes inaccurate; complexities were resolved using a manual radioisotope identification procedure. The impact of target composition, integrated beam current and duration of target irradiation on the waste produced was studied. Results indicate that an average of 0.059  ±  0.003 GBq of waste is generated per 1 GBq of ^99mTc produced. Two-thirds of the total waste activity produced was attributed to ⁹⁹Mo (T _1/2  =  66 h) alone, while a total of fifty radioisotopes were found in the waste. Long-lived isotopes (T _1/2  >  2 months) constituted only 1% of the total waste activity at end of beam (EOB). In conclusion, it was determined that the waste generated during cyclotron-based ^99mTc production was acceptably low for routine clinical production.

Disposable Paper-Based Analytical Device for Visual Speciation Analysis of Ag(I) and Silver Nanoparticles (AgNPs)

A disposable, instrument-free, height readout paper-based analytical device (HR-PAD) based on a paper strip inkjet-printed with CdTe quantum dots (QDs) was developed for the sensitive speciation analysis of Ag⁺ and silver nanoparticles (AgNPs). When the paper strip is immersed into a sample solution, capillary action draws it through the surface and any Ag⁺ in the solution quenches the fluorescence of CdTe QDs via a cation exchange reaction between Ag⁺ and the CdTe QDs, with the height of the quenched band being proportional to the concentration of Ag⁺. In contrast, fluorescence quenching cannot be observed when only AgNPs are present in solution. Thus, the concentration of AgNPs can be obtained by subtracting the Ag⁺ content from the total silver determined by the HR-PAD after digestion with HNO₃. Under optimized conditions, the methodology provides high selectivity, sensitivity, and accuracy for the detection of Ag⁺ or AgNPs in various samples, even at concentrations as low as 0.05 mg L^-1. Precisions of 4.5% and 2.2% RSDs were achieved at concentrations of 1 mg L^-1 and 7 mg L^-1 of Ag⁺, respectively. Compared to conventional methods, this approach is inexpensive and user-friendly and eliminates the need for expensive and sophisticated detection instruments. The practicality of the method was demonstrated via the speciation analysis of AgNPs and Ag⁺ in river water and 12 commercial products with satisfactory results.

DNA-modulated photosensitization: current status and future aspects in biosensing and environmental monitoring

Recently, photosensitized oxidation has been explored in many fields of research and applications, such as photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT). Although the photosensitized generation of ROS features emerging applications, controllable management of the photosensitization process is still sometimes problematic. DNA has long been considered the carrier for genetic information. With the in-depth study of the chemical properties of DNA, the molecular function of DNA is gradually witnessed by the scientific community. Undoubtedly, the selective recognition nature of DNA endows them excellent candidate modulators for photosensitized oxidation. According to current research, reports on DNA regulation of photosensitized oxidation can be roughly divided into two categories in principle: P-Q quenching pair-switched photosensitization and host-guest interaction-switched photosensitization. In this review, the development status of these two analytical methods will be summarized, and the future development direction of DNA-modulated photosensitization in biosensing and environmental monitoring will also be prospected.

Plasma-catalysed reaction Mn+ + L–H → MOFs: facile and tunable construction of metal–organic frameworks in dielectric barrier discharge

A fast, energy-saving and green strategy was proposed for preparing diverse and fine-tuned metal–organic frameworks in either DMF or ethanol, catalyzed by liquid-phase plasma generated via dielectric barrier discharge.

Universal and label-free photosensitization colorimetric assays enabled by target-induced termini transformation of dsDNA resistant to Exo III digestion

A label-free and universal colorimetric assay was developed via the combination of CHA, Exo III digestion, and photosensitization colorimetry.

Cerium-based UiO-66 metal–organic frameworks explored as efficient redox catalysts: titanium incorporation and generation of abundant oxygen vacancies

For the first time, UiO-66(Ce) was endowed with greatly improved redox photocatalytic activity via Ti incorporation, based on the formation of oxygen vacancies.

Expanding DNA nanomachine functionality through binding-induced DNA output for application in clinical diagnosis

Herein, we describe two homogeneous conversion systems that can convert protein recognition into the release of predesigned output DNA for the activation of DNA nanomachines.

Phosphorescent Carbon Dots for Highly Efficient Oxygen Photosensitization and as Photo-oxidative Nanozymes

Materials for photosensitized oxygen activation are extremely important for a suite of photodynamic applications in biomedical, analytical, and energy sectors. Carbon-based photosensitizers are attractive for their low cost and high stability, but most of them such as fullerene and graphene quantum dots suffer from low efficiency, and the rational design of carbon-based photosensitizers remains a challenge. Given the similar chemical origin of phosphorescence and photosensitization, we herein synthesized a series of nitrogen-doped carbon dots (C-dots) and confirmed that their photo-oxidation activity correlated with their phosphorescence quantum yields, providing a direction for the rational designing of such materials. Compared to other carbon nanomaterials and molecular photosensitizers, these C-dots have the highest activity, and they can finish oxidation reactions in a few seconds. The excellent photosensitized oxygen activation makes these water-soluble C-dots a promising oxidase-mimicking nanozyme for photodynamic antimicrobial chemotherapy and other applications.

Molecular mechanisms of azole resistance in Candida tropicalis isolates causing invasive candidiasis in China

OBJECTIVE

We investigated molecular mechanisms responsible for azole resistance in Candida tropicalis isolates.

METHODS

We studied 507 C. tropicalis isolates causing invasive candidiasis from ten hospitals over 5 years. Antifungal susceptibility was determined by broth microdilution methods. Point mutations in the C. tropicalis ERG11 gene that may confer azole resistance were explored and verified. The expression levels of ERG11, CYTb, MDR1 and CDR1 genes were compared in 20 fluconazole-susceptible and 20 fluconazole-resistant isolates.

RESULTS

Fluconazole-susceptible, -susceptible dose-dependent and -resistant strains accounted for 76.7% (389/507), 10.5% (53/507) and 12.8% (65/507) of C. tropicalis isolates, respectively. The ERG11 mutation A395T/W occurred in 10.7% (54/507) of isolates, all of which were resistant to fluconazole. The nucleotide mutation C461T/Y was the second most common (50/507 isolates, 9.9%), and all isolates carrying C461T/Y also had the mutation A395T/W. However, the presence of C461T did not contribute to the azole-resistant phenotype. Substitutions V125A, Y257H and G464S (<2% of isolates), which were reported for the first time in C. tropicalis, also conferred fluconazole non-susceptible phenotypes. Compared with fluconazole susceptible isolates, fluconazole-resistant isolates had higher ERG11 (fold expression level 1.42 versus 0.79, p < 0.01) but lower CYTb (fold expression level 1.26 versus 2.67, p < 0.01) gene expression levels. Three azole-resistant isolates carrying the wild-type ERG11 gene had higher levels of CDR1 and MDR1 expression.

CONCLUSIONS

ERG11 missense mutations were the major mechanism responsible for azole resistance in C. tropicalis isolates, but overexpression of ERG11, CDR1 and MDR1, as well as reduced expression of CYTb, also contributed to resistance.

Enriching Mn-Doped ZnSe Quantum Dots onto Mesoporous Silica Nanoparticles for Enhanced Fluorescence/Magnetic Resonance Imaging Dual-Modal Bio-Imaging

Multimodal imaging is more suitable for disease diagnosis because of its ability to provide more complementary and accurate information over single-mode imaging. Mn-doped quantum dots (QDs), especially Mn-doped ZnS (ZnSe) QDs, possess unique fluorescent and magnetic properties and are thus attractive for fluorescence/magnetic resonance imaging (MRI) dual-mode imaging. However, the optimal dopant (Mn²⁺) concentration for maximizing the fluorescence of QDs is relatively low for the MRI imaging. Herein, based on the large Stokes shift of Mn-doped ZnSe QDs, an enrichment strategy with mesoporous silica (MSN) loading was explored for constructing a highly luminescent/paramagnetism Mn-doped ZnSe QDs assembly (MSN@QDs) for improved MRI/optical dual-model imaging. After assembly, the loading density of QDs in MSNs was estimated to be 152 ± 12. Upon loading, the fluorescence of the MSN@QDs assembly was enriched along with QDs (enrichment factor of ∼143). Because of the large Stokes shift (∼200 nm), no appreciable concentration quenching was observed. Meanwhile, the T₁ MR contrast was also increased both in vitro and in vivo through improved local Mn²⁺ concentration, realizing MRI signal enrichment. In fluorescence imaging investigations, MSN@QDs showed better performance over both single QDs and equivalent numbers of MSN-free single QD. Therefore, this enrichment strategy allowed simultaneous signal enhancement of the two imaging modes of Mn-doped ZnSe QDs.

Miniaturized point discharge-radical optical emission spectrometer: A multichannel optical detector for discriminant analysis of volatile organic sulfur compounds

In this work, we proposed a miniaturized point discharge-radical optical emission spectrometer (PD-RES) as a multichannel optical detector for discriminant analysis of various volatile organic sulfur compounds (VOSCs). Under appropriate experimental conditions, the unique molecular emission of CS radical in the vicinity of 257.6 nm was recorded, as well as the atomic emission lines of C at 193.1 nm and 247.8 nm, the molecular emission of C₂ radical around 231.5 nm and CN radical nearby 384.8 nm. They were utilized as five optical channels for precise qualification and discrimination. Linear discriminant analysis (LDA) and principal component analysis (PCA) further demonstrated the robustness of this detector for discriminant analysis: 95 unknown samples from ten typical VOSCs were classified with accuracy of 98.9%. This proposed detector was further successfully applied to the discrimination of different concentrations of CS₂ in air samples and two types of isomers (functional group isomer and carbon-chain isomer).

Sustained pain hypersensitivity in the stressed colon: Role of mast cell-derived nerve growth factor-mediated enteric synaptic plasticity

BACKGROUND

Sustained pain hypersensitivity is the hallmark of stressed colon which could be partially explained by central sensitization with synaptic plasticity, the key mechanism of memory. We previously identified that synaptic plasticity of enteric nerve system (ENS) contributed to peripheral pain maintaining in the gut. However, the mechanisms of enteric "memory" formation remain elusive.

METHODS

In this study, rats were exposed to water avoidance stress (WAS) or sham stress (SS), with cromolyn sodium or physiological saline injected intraperitoneally 30 minutes before stress every day. The abdominal withdrawal reflex scores, mesenteric afferent nerve activity, enteric neural c-fos expression, and enteric synaptic plasticity were assessed, and mast cell infiltration and degranulation. Furthermore, colonic mucosal mediators-induced enteric synaptic plasticity and the role of mast cell-derived nerve growth factor (NGF), tryptase, and histamine were investigated via ex vivo longitudinal muscle-myenteric plexus (LMMP) organotypic culture.

KEY RESULTS

It is shown that mast cell stabilizing inhibited WAS-induced visceral hypersensitivity through enhancing visceral pain threshold, decreasing spontaneous and distention-induced mesenteric afferent firing, and downregulating enteric neural activation (c-fos). Importantly, WAS led to evident enteric synaptic plasticity, but decreased by cromolyn. Water avoidance stress-derived mucosal supernatants markedly enhanced the c-fos expression and enteric synaptic plasticity in LMMP tissues, which could be eliminated by mast cell inhibition or NGF neutralization, but not tryptase or histamine blocking.

CONCLUSIONS & INFERENCES

In conclusion, mast cells/NGF pathway may be the key regulator of synaptic plasticity of ENS and participate in the formation of chronic stress-induced sustained visceral hypersensitivity.

Point discharge microplasma reactor for high efficiency conversion of H2S to SO2 for speciation analysis of sulfide and sulfite using molecular fluorescence spectrometry

A low temperature plasma integrating the merits of small size, simple operation and rich active particles has good performance in analytical chemistry. In this work, a point discharge microplasma was used as a reactor to facilitate the gaseous conversion reaction from H₂S to SO₂ with an excellent efficiency as high as 95%. By coupling this reactor with a fluorescence spectrometer, the speciation analysis of sulfide and sulfite was achieved in a simple, chromatographic separation-free, time-saving and practical way. Specifically, with the discharge off, only sulfite was quantified; with discharge on, both sulfide and sulfite were quantified; and with a simple subtraction, the speciation analysis could be easily attained. By the acidification process, a limit of detection of 7.7 μM by the proposed method was obtained for both sulfide and sulfite in aqueous medium, and this method was successfully utilized to analysis of real samples.

Aggregation-induced phosphorescence enhancement of Mn-doped ZnS quantum dots: the role of dot-to-dot distance

Assembled nanoparticles promote many applications in optics due to their instinct properties. The aggregation-induced phosphorescence enhancement (AIPE) of Mn-doped ZnS quantum dots (QDs) is widely used in biosensing, but the mechanism of such an enhancement is still unproven. This study explores the mechanism of the interesting finding of AIPE of Mn-doped ZnS QDs. To induce the aggregation of QDs, the method of electrostatic assembly was explored herein: negatively charged QDs were aggregated with protamine and positively charged QDs were aggregated with heparin. Using several ligands with hierarchical molecular weights for capping Mn-doped ZnS QDs, it was found that the AIPE of Mn-doped ZnS QDs was exponentially dependent on the dot-to-dot distance in aggregates. Together with detailed analysis of both the steady- and transient-state luminescence behaviors of Mn-doped ZnS QDs before and after aggregation, charge transfer from one dot (surface traps) to another (dopant bands) was identified as the driving factor for AIPE. Moreover, the d-band of the Mn2+ dopants was essential for the AIPE since it acts as the acceptor for the transferred charge from neighboring QDs. These conclusions can significantly contribute for better understanding of this interesting luminescence mechanism and future designing of the most suitable sensing systems.

Optical sensing at the nanobiointerface of metal ion-optically-active nanocrystals

Optically-active nanocrystals (such as quantum dots and plasmonic noble metal nanoparticles) have received great attention due to their size-tunable optical properties. The indicator displacement assay (IDA) with optically-active nanocrystals has become a common practice for optical sensor development, since no sophisticated surface functionalization of nanoparticles is required. Among the IDA-based optical sensors, the use of metal ions as receptors seems to be attractive. Therefore, in this review, the research progress of optical sensing at the nanobiointerface of metal ion-optically-active nanocrystals has been summarized. In particular, metal ion-mediated selective recognition has been summarized here based on the classical Hard-Soft-Acid-Base (HSAB) principle, which has been seldom mentioned before. Most of the references were therefore categorized according to their located place based on the HSAB theory. Besides, several metal ion modulation strategies that were not related to the HSAB theory (e.g., redox modulation) were also included. Finally, due to the cross-talk of metal ions in selective recognition, we have also summarized sensor array development based on multiple metal ion receptors in IDA sensing with optically-active nanocrystals. Several interesting applications of the IDA sensing with metal ions as receptors and optically-active nanocrystals as indicators are presented, with specific emphasis on the design principles and photophysical mechanisms of these probes.

Copper Ion Assisted Photochemical Vapor Generation of Chlorine for Its Sensitive Determination by Sector Field Inductively Coupled Plasma Mass Spectrometry

A novel, reliable, and sensitive approach for the determination of chlorine by sector field inductively coupled plasma mass spectrometry (SF-ICPMS) using photochemical vapor generation for sample introduction is presented. Methyl chloride is generated from different chlorine species in a flow-through photochemical reactor using a 1% solution of acetic acid containing 7.5 μg g^-1 of Cu²⁺. The volatile product is directed by an argon carrier gas to a gas-liquid separator and introduced into the instrument. A sample flow rate at 1.7 mL min^-1 and a 45 s irradiation time provided a 74-fold enhancement in sensitivity compared to conventional nebulization. A blank-limited detection limit of 0.5 ng g^-1 for chloride, suitable for quantitation at trace levels, was achieved. The proposed method was validated by analysis of two certified reference materials, NIST SRM 1568b rice flour and SRM 1571 orchard leaves, with satisfactory results, as well as three varieties of bottled water, achieving spike recoveries between 101% and 105%.

Analysis of (CAG)n expansion in ATXN1, ATXN2 and ATXN3 in Chinese patients with multiple system atrophy

Multiple system atrophy (MSA) is a complex and multifactorial neurodegenerative disease, and its pathogenesis remains uncertain. Patients with MSA or spinocerebellar ataxia (SCA) show overlapping clinical phenotypes. Previous studies have reported that intermediate or long CAG expansions in SCA genes have been associated with other neurodegenerative disease. In this study, we screened for the number of CAG repeats in ATXN1, 2 and 3 in 200 patients with MSA and 314 healthy controls to evaluate possible associations between (CAG)_n in these three polyQ-related genes and MSA. Our findings indicated that longer repeat lengths in ATXN2 were associated with increased risk for MSA in Chinese individuals. No relationship was observed between CAG repeat length in the three examined genes and age at onset (AO) of MSA.

Ratiometric Phosphorescent Probe for Thallium in Serum, Water, and Soil Samples Based on Long-Lived, Spectrally Resolved, Mn-Doped ZnSe Quantum Dots and Carbon Dots

Thallium (Tl) is an extremely toxic heavy metal and exists in very low concentrations in the environment, but its sensing is largely underexplored as compared to its neighboring elements in the periodic table (especially mercury and lead). In this work, we developed a ratiometric phosphorescent nanoprobe for thallium detection based on Mn-doped ZnSe quantum dots (QDs) and water-soluble carbon dots (C-dots). Upon excitation with 360 nm, Mn-doped ZnSe QDs and C-dots can emit long-lived and spectrally resolved phosphorescence at 580 and 440 nm, respectively. In the presence of thallium, the phosphorescence emission from Mn-doped ZnSe QDs could be selectively quenched, while that from C-dots retained unchanged. Therefore, a ratiometric phosphorescent probe was thus developed, which can eliminate the potential influence from both background fluorescence and other analyte-independent external environment factors. Several other heavy metal ions caused interferences to thallium detection but could be efficiently masked with EDTA. The proposed method offered a detection limit of 1 μg/L, which is among the most sensitive probes ever reported. Successful application of this method for thallium detection in biological serum as well as in environmental water and soil samples was demonstrated.

Low-Temperature and Atmospheric Pressure Sample Digestion Using Dielectric Barrier Discharge

A new sample digestion method using a double layer and coaxial dielectric barrier discharge (DBD) digestion reactor was developed for the sensitive determination of trace elements in rice samples. All the operation parameters of the DBD microplasma and other digestion conditions were carefully optimized. Three DBD-digestion modes were investigated for real matrix samples, including H₂O-DBD-digestion, H₂O₂-DBD-digestion, and HNO₃-DBD-digestion systems. Among the three modes, the H₂O-DBD-digestion system provides a suitable digestion of sample without any additional chemicals, achieving environmental friendly sample treatment and eliminating the potential interferences. Under the optimized conditions, limits of detection for Mg, Mn, Zn, Cd, Cr, Co, and As were in the range of 0.01-0.35 ng g^-1 by inductively coupled plasma mass spectrometry (ICPMS). The accuracy of the proposed method was checked by analysis of a certified reference material (GBW10043) and spiked samples with satisfactory results (83-113% recoveries).

Phosphorescent inner filter effect-based sensing of xanthine oxidase and its inhibitors with Mn-doped ZnS quantum dots

Large bandgap semiconductor ZnS QDs (Mn-doped) were explored for inner filter effect-based sensing of xanthine oxidase and its inhibitors, due to the maximum spectral overlap between the absorption of uric acid (the enzymatic product of xanthine oxidase) and the excitation of Mn-doped ZnS QDs.

Selective reduction-based, highly sensitive and homogeneous detection of iodide and melamine using chemical vapour generation-atomic fluorescence spectrometry

A selective reduction-based method was proposed for the sensitive detection of iodide and melamine using chemical vapour generation (CVG) coupled with atomic fluorescence spectrometry (AFS).

In situ formation of nano-CdSe as a photocatalyst: cadmium ion-enhanced photochemical vapour generation directly from Se(vi)

The in situ formation of nano-CdSe as a photocatalyst enhances the efficiency of the photochemical generation of gaseous Se-containing species.

Enhancement of photoredox catalytic properties of porphyrinic metal–organic frameworks based on titanium incorporation via post-synthetic modification

PCN-224 is endowed with greatly enhanced photocatalytic performance for both oxidation and reduction via incorporation of titanium as a metal node.

A Target-Triggered DNAzyme Motor Enabling Homogeneous, Amplified Detection of Proteins

We report here the concept of a self-powered, target-triggered DNA motor constructed by engineering a DNAzyme to adapt into binding-induced DNA assembly. An affinity ligand was attached to the DNAzyme motor via a DNA spacer, and a second affinity ligand was conjugated to the gold nanoparticle (AuNP) that was also decorated with hundreds of substrate strands serving as a high-density, three-dimensional track for the DNAzyme motor. Binding of a target molecule to the two ligands induced hybridization between the DNAzyme and its substrate on the AuNP, which are otherwise unable to spontaneously hybridize. The hybridization of DNAzyme with the substrate initiates the cleavage of the substrate and the autonomous movement of the DNAzyme along the AuNP. Each moving step restores the fluorescence of a dye molecule, enabling monitoring of the operation of the DNAzyme motor in real time. A simple addition or depletion of the cofactor Mg²⁺ allows for fine control of the DNAzyme motor. The motor can translate a single binding event into cleavage of hundreds of substrates, enabling amplified detection of proteins at room temperature without the need for separation.

Exploring the tunable excitation of QDs to maximize the overlap with the absorber for inner filter effect-based phosphorescence sensing of alkaline phosphatase

The inner filter effect (IFE) is an effective way for fluorescence modulation and thus has been extensively explored for the development of fluorescence assays. Theoretically, the key to maximize the sensitivity of IFE-based fluorescence assays is to enlarge the overlap between the absorption of the absorber and the excitation/emission of the fluorophore. Therefore, in this work, the tunable excitation of quantum dots (QDs) was explored for screening of the IFE pair having the best IFE-based assay sensitivity. A series of QDs, including CdTe QDs with different sizes, carbon dots, Cu-doped CdS QDs, and Mn-doped ZnS QDs, were investigated. PNPP (p-nitrophenylphosphate) was chosen as the absorber since its absorption overlapped with the above QDs. Besides, it can be catalytically converted to p-nitrophenol (PNP) by alkaline phosphatase (ALP) together with an absorption spectrum change (red-shift). Interestingly, it was found that the IFE efficiency of different PNPP-QD pairs increased almost linearly with the corresponding spectral overlap, and Mn-doped ZnS QDs were eventually chosen for the IFE assay of ALP because of the maximum spectral overlap and thus the best sensitivity. A simple and sensitive turn-on phosphorescence ALP assay was developed, with a detection limit of 4 × 10^-4 U L^-1. Because of the high sensitivity, we also found that ALP of different origins possessed different enzymatic activities. The developed ALP phosphorescence assay was successfully employed for the analysis of ALP in serum samples.