Persulfidation maintains cytosolic G6PDs activity through changing tetrameric structure and competing cysteine sulfur oxidation under salt stress in Arabidopsis and tomato.

Glucose-6-phosphate dehydrogenases (G6PDs) are essential regulators of cellular redox. Hydrogen sulfide (H2 S) is a small gasotransmitter that improves plant adaptation to stress; however, its role in regulating G6PD oligomerization to resist oxidative stress remains unknown in plants. Persulfidation of cytosolic G6PDs was analyzed by mass spectrometry (MS). The structural change model of AtG6PD6 homooligomer was built by chemical cross-linking coupled with mass spectrometry (CXMS). We isolated AtG6PD6C159A and SlG6PDCC155A transgenic lines to confirm the in vivo function of persulfidated sites with the g6pd5,6 background. Persulfidation occurs at Arabidopsis G6PD6 Cystine (Cys)159 and tomato G6PDC Cys155, leading to alterations of spatial distance between lysine (K)491-K475 from 42.0 Å to 10.3 Å within the G6PD tetramer. The structural alteration occurs in the structural NADP+ binding domain, which governs the stability of G6PD homooligomer. Persulfidation enhances G6PD oligomerization, thereby increasing substrate affinity. Under high salt stress, cytosolic G6PDs activity was inhibited due to oxidative modifications. Persulfidation protects these specific sites and prevents oxidative damage. In summary, H2 S-mediated persulfidation promotes cytosolic G6PD activity by altering homotetrameric structure. The cytosolic G6PD adaptive regulation with two kinds of protein modifications at the atomic and molecular levels is critical for the cellular stress response.

Heterocyclic Boron Acid Catalyzed Dehydrative Amidation of Aliphatic/Aromatic Carboxylic Acids with Amines.

A commercially available and versatile dehydrative amidation catalyst, featuring a thianthrene boron acid structure, has been developed. The catalyst shows high catalytic activity to both aliphatic and less reactive aromatic carboxylic acid substrates, including several bioactive or clinical molecules with a carboxylic acid group.

Hydrogen sulfide improves salt tolerance through persulfidation of PMA1 in Arabidopsis.

KEY MESSAGE: A new interaction was found between PMA1 and GRF4. H2S promotes the interaction through persulfidated Cys446 of PMA1. H2S activates PMA1 to maintain K+/Na+ homeostasis through persulfidation under salt stress. Plasma membrane H+-ATPase (PMA) is a transmembrane transporter responsible for pumping protons, and its contribution to salt resistance is indispensable in plants. Hydrogen sulfide (H2S), a small signaling gas molecule, plays the important roles in facilitating adaptation of plants to salt stress. However, how H2S regulates PMA activity remains largely unclear. Here, we show a possible original mechanism for H2S to regulate PMA activity. PMA1, a predominant member in the PMA family of Arabidopsis, has a non-conservative persulfidated cysteine (Cys) residue (Cys446), which is exposed on the surface of PMA1 and located in cation transporter/ATPase domain. A new interaction of PMA1 and GENERAL REGULATORY FACTOR 4 (GRF4, belongs to the 14-3-3 protein family) was found by chemical crosslinking coupled with mass spectrometry (CXMS) in vivo. H2S-mediated persulfidation promoted the binding of PMA1 to GRF4. Further studies showed that H2S enhanced instantaneous H+ efflux and maintained K+/Na+ homeostasis under salt stress. In light of these findings, we suggest that H2S promotes the binding of PMA1 to GRF4 through persulfidation, and then activating PMA, thus improving the salt tolerance of Arabidopsis.

Occurrence of OCPs & PCBs and their effects on multitrophic biological communities in riparian groundwater of the Beiluo River, China.

Persistent Organic Pollutants (POPs) may exert adverse effects on human and ecosystem health. However, as an ecologically fragile zone with strong interaction between river and groundwater, the POPs pollution in the riparian zone has received little attention. The goal of this research is to examine the concentrations, spatial distribution, potential ecological risks, and biological effects of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the riparian groundwater of the Beiluo River, China. The results showed that the pollution level and ecological risk of OCPs in riparian groundwater of the Beiluo River were higher than PCBs. The presence of PCBs (Penta-CBs, Hexa-CBs) and CHLs, respectively, may have reduced the richness of bacteria (Firmicutes) and fungi (Ascomycota). Furthermore, the richness and Shannon's diversity index of algae (Chrysophyceae and Bacillariophyta) decreased, which could be linked to the presence of OCPs (DDTs, CHLs, DRINs), and PCBs (Penta-CBs, Hepta-CBs), while for metazoans (Arthropoda) the tendency was reversed, presumably as a result of SULPHs pollution. In the network analysis, core species belonging to bacteria (Proteobacteria), fungi (Ascomycota), and algae (Bacillariophyta) played essential roles in maintaining community function. Burkholderiaceae and Bradyrhizobium can be considered biological indicators of PCBs pollution in the Beiluo River. Note that the core species of interaction network, playing a fundamental role in community interactions, are strongly affected by POPs pollutants. This work provides insights into the functions of multitrophic biological communities in maintaining the stability of riparian ecosystems through the response of core species to riparian groundwater POPs contamination.

Spatiotemporal variations of water conservation function based on EOF analysis at multi time scales under different ecosystems of Heihe River Basin.

Water conservation function is a critical terrestrial ecosystem service in providing water supply and achieving water security, which has raised concerns under the pressure of climate change. However, the knowledge of variance on multi-time scale, spatiotemporal dynamic, and ecosystem variance of water conservation is insufficient. In this paper, the annual, monthly, and daily scales of water conservation and the spatiotemporal pattern of monthly water conservation were estimated based on the SWAT model from 2010 to 2020 in the Heihe River Basin (HRB). Additionally, EOF (Empirical orthogonal function) analysis was conducted to decompose the time series of water conservation function distribution into temporal coefficients and spatial patterns. The HRB was categorized into six representative ecosystems with three slope grades to illustrate the variance of water conservation function. The annual water conservation depth (WC) slightly decreased (-10.36 mm/10a) from 2010 to 2020, the monthly WC was dominated by the effects of seasonal variation, and the daily WC was highly nonlinear. The high variability and importance region is mainly located in the upstream and the central area of midstream, which deserves more attention for ecological management and priority protection. Moreover, the forest ecosystem is of the highest resilience and great ecological significance, which increased risk of reduced water conservation under the lack of precipitation. Even in a forest-dominated basin, water conservation can be impacted by other ecosystems with the strong influence of human activities. Our results provide scientific evidence for the improvement of water conservation capacity and making the adapted land use policy in Yellow River basins.

Precise Polishing and Electrochemical Applications of Quartz Nanopipette-Based Carbon Nanoelectrodes.

Quartz nanopipette-based carbon nanoelectrodes (CNEs) have attracted extensive attention in nanoscale electrochemistry due to their simple and efficient fabrication, chemically inert materials, flexible size (down to a few nanometers), and ultrathin insulating encapsulation. However, these pristine CNEs usually have significantly irregular morphology on the surface, which greatly limits the applications where inlaid nanodisks are urgently needed. To address this critical issue, we have developed a new precise polishing strategy using paraffin coating protection (i.e., avoiding breakage of quartz materials) and real-time monitoring with a high impedance meter (i.e., indicating electrode exposure) to produce flat carbon nanodisk electrodes. The surface flatness of polished CNEs has been confirmed by a combination of scanning electron microscopy, fast-scan cyclic voltammetry, and scanning electrochemical microscopy. As compared to the expensive focused ion beam processing, this strategy is competitive in terms of the low cost and availability of the equipment and enables the preparation of polished CNEs with sufficiently small size. The flattened CNEs have been exemplified for grafting molecular catalysts to achieve the durable catalysis of reactive molecules or for immobilizing single-particle electrocatalysts to measure the intrinsic activity under sufficient mass-transfer rates.

Shear Flows in Far-from-Equilibrium Strongly Coupled Fluids.

Although the viscosity of a fluid ranges over several orders of magnitude and is extremely sensitive to microscopic structure and molecular interactions, it has been conjectured that its (opportunely normalized) minimum displays a universal value which is experimentally approached in strongly coupled fluids such as the quark-gluon plasma. At the same time, recent findings suggest that hydrodynamics could serve as a universal attractor even when the deformation gradients are large and that dissipative transport coefficients, such as viscosity, could still display a universal behavior far from equilibrium. Motivated by these observations, we consider the real-time dissipative dynamics of several holographic models under large shear deformations. In all the cases considered, we observe that at late time both the viscosity-entropy density ratio and the dimensionless ratio between energy density and entropy density approach a constant value. Whenever the shear rate in units of the energy density is small at late time, these values coincide with the expectations from near equilibrium hydrodynamics. Surprisingly, even when this is not the case, and the system at late time is far from equilibrium, the viscosity-to-entropy ratio approaches a constant which decreases monotonically with the dimensionless shear rate and can be parametrically smaller than the hydrodynamic result.

Development of an Ultrasmall and Biocompatible Platinum Nanozyme Encapsulated by Zwitterionic Dendrimer for Highly Sensitive Detection of Glucose.

Many kinds of noble metal nanoparticles can mimic the peroxidase-like function of horseradish peroxidase, which results in their wide applications in bio-related detection and drug delivery. However, those metal nanoparticles usually have low stability and reduced catalytic activity in biological complex medium. Herein, a zwitterionic peroxidase-like enzyme has been developed, which has high stability in fibrinogen solutions and high sensitivity for glucose detection. Maleic anhydride, cysteamine, and zwitterionic peptide EKEKC (EK-5) were used to modify generation 5 poly(amido amine) dendrimers (G5 PAMAM) to prepare zwitterionic dendrimer G5MEKnC with nonfouling properties. Finally, the G5MEKnC-encapsulated platinum nanoparticles (Ptn-G5MEK50C) were prepared by entrapping the platinum nanoparticles (1.40 nm) in the catalytic centers in the interior of G5MEK50C. Pt55-G5MEK50C showed high stability in the buffer solution and the fibrinogen solution within 4 days. They also displayed high biocompatibility toward HeLa cells based on cytotoxicity results and morphological observations. Furthermore, the catalytic oxidation of 3,3',5,5'-tetramethylbenzidine with H2O2 by Pt55-G5MEK50C followed the Michaelis-Menten equation, which confirmed their peroxidase-like properties. The catalytic mechanism was due to the generation of •OH from H2O2. More importantly, the peroxidase-like ability of Pt55-G5MEK50C was successfully used to establish a method for the determination of glucose concentration with a broad linear range of 1-2000 µM and a low detection limit of 0.1 µM. This method was highly accurate for the determination of glucose concentration in plasma. The zwitterionic dendrimer template enhanced the properties of Pt55-G5MEK50C. Taken together, a new kind of biocompatible nanozyme has been developed and successfully used for the sensitive detection of glucose in bio-related medium.

Effects of heavy metals and hyporheic exchange on microbial community structure and functions in hyporheic zone.

The responses of microbial communities in hyporheic zone to the eco-hydrological process have been a hotspot in river ecological health research. However, the impact of different metal pollution levels and hyporheic exchange on the microbial communities are still unclear. In this study, we further explored the effects of different degrees of heavy metals pollution and the strength of hyporheic exchange on the structures and functions of microbial community in hyporheic zone sediment ecosystem. Sediments were collected from the Weihe River to determine the concentrations of heavy metals, grain size distribution, and hydraulic conductivity, and the microbial information were obtained by eDNA technology. The comprehensive pollution status of the study area was at the slight and moderate level. The hydraulic conductivity (Kv) varied between 0.20 and 3.65 (m/d). The microbial community structures had complex temporal and spatial heterogeneity. The microbial molecular ecological network had modular characteristics and significant differences in different periods (p < 0.05). Metabolic functional genes in microbial communities had the highest relative abundance. In particular, there is a significant negative correlation between heavy metals and microorganisms (p < 0.05), with Cu and Zn contributing the most to microbial community changes (p < 0.05). Moreover, grain size had a significant impact on microorganisms, heavy metals and grain size significantly affect the predictive functions of microbial communities. Our in-depth research on microorganisms in the hyporheic zone provides references for monitoring and bioremediation of aquatic ecosystems.

The impacts of China's crops trade on virtual water flow and water use sustainability of the "Belt and Road".

Since the "Belt and Road" initiative was put forward, the trade of crops between China and the countries have increased markedly. Agriculture is the most water-consuming sector, the trade of crops could influence national water availability via virtual water embodied in the products. In order to gain an in-depth understanding of the water use of crops traded in countries along the "Belt and Road", from the perspective of import and export of China's crops, based on the characteristics and driving factors of virtual water trade, we proposed the Water Use Potential Index (WUPI) to assess sustainability of countries and their crops, and constructed a more comprehensive virtual water trade research framework. Results showed that the import and export of virtual water in 64 countries was dominated by green virtual water content from 2001 to 2017, and China was in a virtual water trade surplus. The Association of South-East Asian Nations was China's leading importer and exporter. The level of agricultural available water resources, the proportion of the agricultural population, the scale of agricultural production and the virtual water intensity could promote the growth of virtual water trade in crops between China and countries along the "Belt and Road", while economic model and the population structure played a restraining role. In terms of water use potential, China and Kazakhstan had great sustainable water use potential for crops, and the trade structure of other countries still needed to be further optimized. Understanding the virtual water trade in crops can provide a reference for the rational planning of crop cultivation and water resource conservation.

Classification of microcalcification clusters in digital breast tomosynthesis using ensemble convolutional neural network.

BACKGROUND: The classification of benign and malignant microcalcification clusters (MCs) is an important task for computer-aided diagnosis (CAD) of digital breast tomosynthesis (DBT) images. Influenced by imaging method, DBT has the characteristic of anisotropic resolution, in which the resolution of intra-slice and inter-slice is quite different. In addition, the sharpness of MCs in different slices of DBT is quite different, among which the clearest slice is called focus slice. These characteristics limit the performance of CAD algorithms based on standard 3D convolution neural network (CNN). METHODS: To make full use of the characteristics of the DBT, we proposed a new ensemble CNN, which consists of the 2D ResNet34 and the anisotropic 3D ResNet to extract the 2D focus slice features and 3D contextual features of MCs, respectively. Moreover, the anisotropic 3D convolution is used to build 3D ResNet to avoid the influence of DBT anisotropy. RESULTS: The proposed method was evaluated on 495 MCs in DBT images of 275 patients, which are collected from our collaborative hospital. The area under the curve (AUC) of receiver operating characteristic (ROC) and accuracy of classifying benign and malignant MCs using decision-level ensemble strategy were 0.8837 and 82.00%, which were significantly higher than the experimental results of 2D ResNet34 (AUC: 0.8264, ACC: 76.00%) and anisotropic 3D ResNet (AUC: 0.8455, ACC: 76.00%). Compared with the results of 3D features classification in the radiomics, the AUC of the deep learning method with decision-level ensemble strategy was improved by 0.0435, and the F1 score was improved from 79.37 to 85.71%. More importantly, the sensitivity increased from 78.13 to 84.38%, and the specificity increased from 66.67 to 77.78%, which effectively reduced the false positives of diagnosis CONCLUSION: The results fully prove that the ensemble CNN can effectively integrate 2D features and 3D features, improve the classification performance of benign and malignant MCs in DBT, and reduce the false positives.

Metabolic footprint analysis of volatile metabolites to discriminate between different key time points in the fermentation and storage of starter cultures and probiotic Lactobacillus casei Zhang milk.

Interest has been growing in the co-fermentation of starter cultures with probiotic bacteria in milk. However, the representative metabolites and metabolic changes at different key time points during milk fermentation and storage in starter cultures and probiotic bacteria are still unclear. In this study, we used gas chromatography/mass spectrometry-based metabolomics to identify volatile metabolites and discriminate between 6 different time points [fermentation initiation (FI), fermentation curd (FC), fermentation termination (FT), storage 1 d (S1d), storage 7 d (S7d), and storage 14 d (S14d)] during the fermentation and storage of starter cultures and Lactobacillus casei Zhang milk. Of the 52 volatile metabolites identified, 15 contributed to discrimination of the 6 time points. Then, using the profile from the different time points, we analyzed pairwise comparisons (FI vs. FC; FC vs. FT; FT vs. S1d; S1d vs. S7d; S7d vs. S14d); these time-lapse comparisons showed metabolic progressions from one fermentation stage to the next. We found representative and exclusive metabolites at specific fermentation and storage time points. The greatest difference in metabolites occurred between FC and FT, and the metabolic profiles between S7d and S14d were most similar. Interestingly, decanoic acid, octanoic acid, and hexanoic acid reached their highest level at storage 14 d, indicating that the post-fermentation storage of fermented milk with L. casei Zhang may add more probiotic functions. This work provides detailed insight into the time-specific profiles of volatile metabolites and their dynamic changes; these data may be used for understanding and eventually predicting metabolic changes in milk fermentation and storage, where probiotic strains may be used.

Comparison of the effects of single probiotic strains Lactobacillus casei Zhang and Bifidobacterium animalis ssp. lactis Probio-M8 and their combination on volatile and nonvolatile metabolomic profiles of yogurt.

There has been a growing interest in cofermentation of starter cultures with probiotics in milk. In this study, we analyzed the effects of adding the single probiotics Lactobacillus casei Zhang (Zhang) or Bifidobacterium animalis ssp. lactis Probio-M8 (M8) or a combination of Zhang and M8 to starter cultures on volatile and nonvolatile metabolomic profiles after 14 d of storage at 4°C and compared using a liquid chromatography-tandem mass spectrometry (LC-MS) and GC-MS-based metabolomics approach. Principal component analysis, heatmap plots, and Spearman correlation results showed that Zhang alone had a greater effect on volatile and nonvolatile metabolomic profiles than M8 alone. The combination of Zhang and M8 had additive effects on the production of metabolites. For volatile metabolites, the levels of acetaldehyde, diacetyl, acetoin, and acetic acid were higher for the combination of Zhang and M8 compared with either single probiotic culture. Significantly increased nonvolatile components induced by adding Zhang were identified were enriched in the galactose, amino- and nucleotide sugar, fructose and mannose, purine, phenylalanine metabolism, and arginine biosynthesis pathways. The metabolism and biosynthesis of starch, sucrose, tyrosine, galactose metabolism, and aminoacyl-tRNA biosynthesis were significantly upregulated by adding the combination of Zhang and M8. This work provides a detailed insight into different effects of Zhang and M8 used alone or in combination on the volatile and nonvolatile metabolomic profiles of yogurts.

Evaluation of water conservation function of Danjiang River Basin in Qinling Mountains, China based on InVEST model.

With the shortage of water resources becoming a global concern, the water conservation function has become one of the most important service functions and the key factor in the sustainable development of watershed ecosystem. The Danjiang River Basin as an important source of water for the middle route of China's South-to-North Water Diversion Project, its water conservation function has attracted extensive public attention under global climate change. In this study, InVEST water yield model based on Budyko hydrological method was employed to analyze the spatio-temporal dynamics of water conservation, and the response of water conservation to climate, land use and soil changes for the period from 2000 to 2019. The results show that the water conservation of Danjiang River Basin tends to decrease under the comprehensive influence of various factors. The spatial analysis of the importance of water conservation identified Shangnan County, the southern part of Danfeng County and the northern part of Shanyang County as important water conservation areas in the study area, which should be regarded as the key and priority protection areas in the regional water resource and ecological protection. The study provides insights for sustainable water management and ecological protection policies, and the InVEST model with localized parameters can also be applied to other areas lacking climate, hydrological and geological data.

Nickel-Catalyzed Intramolecular Desulfitative C-N Coupling: A Synthesis of Aromatic Amines.

A nickel-catalyzed intramolecular C-N coupling reaction via SO2 extrusion is presented. The use of a catalytic amount of BPh3 allows the transformation to take place under much milder conditions (60 °C) than previously reported C-N coupling reactions by CO or CO2 extrusion (160-180 °C). In addition, this method displays good functional group tolerance and versatility, as it can be applied to the synthesis of dialkyl aryl amines, alkyl diaryl amines, and triaryl amines. The robustness of the desulfitative C-N coupling is demonstrated by three high-yielding gram-scale reactions.

Characterization of potentially probiotic lactic acid bacteria and bifidobacteria isolated from human colostrum.

Breast milk is the main source of nutrition for infants; it contains considerable microflora that can be transmitted to the infant endogenously or by breastfeeding, and it plays an important role in the maturation and development of the immune system. In this study, we isolated and identified lactic acid bacteria (LAB) from human colostrum, and screened 2 strains with probiotic potential. The LAB isolated from 40 human colostrum samples belonged to 5 genera: Lactobacillus, Bifidobacterium, Streptococcus, Enterococcus, and Staphylococcus. We also isolated Propionibacterium and Actinomyces. We identified a total of 197 strains of LAB derived from human colostrum based on their morphology and 16S rRNA sequence, among them 8 strains of Bifidobacterium and 10 strains of Lactobacillus, including 3 Bifidobacterium species and 4 Lactobacillus species. The physiological and biochemical characteristics of strains with good probiotic characteristics were evaluated. The tolerances of some of the Bifidobacterium and Lactobacillus strains to gastrointestinal fluid and bile salts were evaluated in vitro, using the probiotic strains Bifidobacterium lactis BB12 and Lactobacillus rhamnosus GG as controls. Among them, B. lactis Probio-M8 and L. rhamnosus Probio-M9 showed survival rates of 97.25 and 78.33% after digestion for 11 h in artificial gastrointestinal juice, and they exhibited growth delays of 0.95 and 1.87 h, respectively, in 0.3% bile salts. These two strains have the potential for application as probiotics and will facilitate functional studies of probiotics in breast milk and the development of human milk-derived probiotics.

Transcriptomic analysis suggests the inhibition of DNA damage repair in green alga Raphidocelis subcapitata exposed to roxithromycin.

Macrolide antibiotics are common contaminants in the aquatic environment. They are toxic to a wide range of primary producers, inhibiting the algal growth and further hindering the delivery of several ecosystem services. Yet the molecular mechanisms of macrolides in algae remain undetermined. The objectives of this study were therefore to: 1. evaluate whether macrolides at the environmentally relevant level inhibit the growth of algae; and 2. test the hypothesis that macrolides bind to ribosome and inhibit protein translocation in algae, as it does in bacteria. In this study, transcriptomic analysis was applied to elucidate the toxicological mechanism in a model green alga Raphidocelis subcapitata treated with 5 and 90 µg L-1 of a typical macrolide roxithromycin (ROX). While exposure to ROX at 5 µg L-1 for 7 days did not affect algal growth and the transciptome, ROX at 90 µg L-1 resulted in 45% growth inhibition and 2306 (983 up- and 1323 down-regulated) DEGs, which were primarily enriched in the metabolism of energy, lipid, vitamins, and DNA replication and repair pathways. Nevertheless, genes involved in pathways in relation to translation and protein translocation and processing were dysregulated. Surprisingly, we found that genes involved in the base excision repair process were mostly repressed, suggesting that ROX may be genotoxic and cause DNA damage in R. subcapitata. Taken together, ROX was unlikely to pose a threat to green algae in the environment and the mode of action of macrolides in bacteria may not be directly extrapolated to green algae.

Assessment of aquatic ecological health based on determination of biological community variability of fish and macroinvertebrates in the Weihe River Basin, China.

A healthy aquatic ecosystem plays an important role in the operation of nature and the survival of human beings. Understanding the mechanism of its interaction with the habitat process is conducive to formulating targeted ecological recovery plans. In this study, fish and macroinvertebrates were collected from 49 investigation sites in the Weihe River basin, China, during periods of the summer and the autumn of 2017. Cluster analysis and canonical correlation analysis (CCA) were used to analyze the similarity of community distribution of fish and macroinvertebrates and their response to environmental variables. The biological integrity index of fish (F-IBI) and benthic-macroinvertebrate (B-IBI) was introduced to evaluate the aquatic ecological health. The results showed that fish communities were more coherent than macroinvertebrate communities. The distinguished response to ecological factors was identified for fish and macroinvertebrates. The ecological factors of total nitrogen, conductivity and river width have significant effects on both fish and macroinvertebrate communities. In addition, the fish community was significantly influenced by chlorine, fluorine, pH and flow velocity, while the macroinvertebrate community was significantly influenced by bicarbonate and water depth. The differences in community structure and response to ecological factors between communities were amplified in their environmental quality scores. Although F-IBI and B-IBI tend to be consistent temporally, the correlation is not significant. B-IBI showed decreasing gradient of ecological health status in the downstream area, while F-IBI tended to be different across river systems, which further illustrated the differences in the response of fish and macroinvertebrates to environmental variables.

Zwitterionic Cross-Linked Biodegradable Nanocapsules for Cancer Imaging.

Zwitterionic cross-linked biodegradable nanocapsules (NCs) were synthesized for cancer imaging. A polylactide (PLA)-based diblock copolymer with two blocks carrying acetylenyl and allyl groups respectively was synthesized by ring-opening polymerization (ROP). Azide-alkyne "click" reaction was conducted to conjugate sulfobetaine (SB) zwitterions and fluorescent dye Cy5.5 onto the acetylenyl-functionalized first block of the diblock copolymer. The resulting copolymer with a hydrophilic SB/Cy5.5-functionalized PLA block and a hydrophobic allyl-functionalized PLA block could stabilize miniemulsions because of its amphiphilic diblock structure. UV-induced thiol-ene "click" reaction between a dithiol cross-linker and the hydrophobic allyl-functionalized block of the copolymer at the peripheral region of nanoscopic oil nanodroplets in the miniemulsion generated cross-linked polymer NCs with zwitterionic outer shells. These NCs showed an average hydrodynamic diameter ( Dh) of 136 nm. They exhibited biodegradability, biocompatibility and high colloidal stability. In vitro study indicated that these NCs could be taken up by MIA PaCa-2 cancer cells. In vivo imaging study showed that, comparing to a small molecule dye, NCs had a longer circulation time, facilitating their accumulation at tumors for cancer imaging. Overall, this work demonstrates the applicability of zwitterionic biodegradable polymer-based materials in cancer diagnosis.

Ultra-small biocompatible jujube polysaccharide stabilized platinum nanoclusters for glucose detection.

The development of noble ultra-small biocompatible Pt nanoclusters (Pt NCs) for glucose detection has been drawing great attention. Herein, ultra-small biocompatible jujube polysaccharide (JP) stabilized platinum nanoclusters (Ptn-JP NCs) are prepared using natural JP as a reducing and solubilizing agent. Ptn-JP NCs were studied for the colorimetric detection of glucose. Ptn-JP NCs (n = 50, 200 and 400) had an average particle diameter of 1-2 nm. Particularly, the measurements of hydrodynamic sizes of Ptn-JP NCs indicated that they maintained good stability in solution for one week. Pt200-JP NCs showed good biocompatibility, and were not toxic against HeLa cells at a high concentration of 400 µg mL-1. Furthermore, Pt200-JP NCs catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with H2O2 to produce blue oxidized TMB (oxTMB). This reaction followed typical Michaelis-Menten kinetics. More importantly, the glucose concentration could be sensitively detected by the color change, and this process was not interfered by other sugars. The linear range for glucose concentration was from 0.01 to 1 mM with a detection limit of 5.47 µM. The glucose concentrations of real samples of serum using Pt200-JP NCs were 9.2, 4.9 and 6.5 mM, respectively. The prepared Ptn-JP NCs have great potential in various biomedical detection methods.