Dynamic carboxymethyl chitosan prodrug hydrogel precisely mediates robust therapy on wound infection.

Dynamic antibacterial polysaccharide prodrug hydrogels are in great demand for treatment of wound infection owing to their unique advantages such as excellent biocompatibility, superior antimicrobial property as well as favorable wound healing capacity. Herein, this work highlights the successful development of a dynamic carboxymethyl chitosan (CMC) prodrug hydrogel, which is facilely constructed through Schiffer base reaction between antibacterial components (amikacin and CMC) and crosslinker (dialdehyde PEG). Moderate dynamic imine linkages endow the hydrogel with excellent injectable and self-healing capability as well as targeted on-demand drug release in slightly alkaline condition at infected wound. All ingredients and their strong intermolecular interactions endow the hydrogel with favorable swelling and moisture retention capability. Moreover, the covalent and non-covalent interactions also endow the hydrogel with superior adhesion and mechanical property. These attractive characteristics enable hydrogel to effectively kill pathogens, promote wound healing and reduce side effects of amikacin. Thereby, such a dynamic CMC prodrug hydrogel may open a new avenue for a robust therapy on wound infection, greatly advancing their use in clinics.

Synthesis of a novel photochemical and thermoresponsive diblock biomaterial with end-functionalized zinc porphyrin.

Porphyrin compound-based photochemical molecules and biomaterials have been synthesized for photosensitivity and bioimaging experiments. However, most porphyrin photosensitizers have limited application in biological environments owing to severe aggregation in aqueous solutions. In the present study, we prepared amphipathic and photosensitive copolymers using zinc porphyrin via consecutive atom transfer-free radical polymerizations (ATRPs) comprising photoresponsive and thermosensitive chain segments. Furthermore, we evaluated the photocatalytic activity of the copolymer for methylene blue (MB) in water. Methods: First, we synthesized a photoresponsive ain segment of poly (6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate) (ZnPor-PAzo); then, ZnPor-PAzo was used as a macroinitiator and was polymerized with N-isopropylacrylamide (NIPAM) via ATRPs to obtain a novel photochemical and thermoresponsive diblock biomaterial with end-functionalized zinc porphyrin [(ZnPor-PAzo)-PNIPAMs]. Results: The polydispersity index (M w/M n) of (ZnPor-PAzo)-PNIPAMs was 1.19-1.32. Furthermore, its photoresponsive and thermosensitive characteristics were comprehensively studied. Discussion: The end-functionalized diblock copolymer (ZnPor-PAzo)-PNIPAM exhibits obvious fluorescence and efficient photocatalytic activity for aqueous MB under visible light.

Rapid and sensitive UHPLC-MS/MS methods for dietary sample analysis of 43 mycotoxins in China total diet study.

INTRODUCTION: Mycotoxins are toxic metabolites produced by fungi that commonly contaminate foods. As recommended by the World Health Organization, total diet study (TDS) is the most efficient and effective way to estimate the dietary intakes of certain chemical substances for general populations. It requires sensitive and reliable analytical methods applicable to a wide range of complex food matrices and ready-to-eat dishes. OBJECTIVES: A novel strategy with high selectivity and sensitivity, incorporating three methods based on ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS), was designed for measuring 43 mycotoxins in dietary samples in a China TDS. METHODS: The 43 mycotoxins were divided into 3 groups for analysis to achieve better performance. For each group, an UHPLC-MS/MS method was developed to determine the target compounds after clean-up by solid phase extraction. A total of 21 isotope internal standards were employed for accurate quantitation. Method validation in terms of linearity, selectivity, sensitivity, accuracy, and precision was performed for all the 43 mycotoxins in 12 complex food matrices. RESULTS: The limits of detection (LODs) and limits of quantitation (LOQs) were 0.002-1 ng mL-1 and 0.006-3 ng mL-1, respectively. The method recoveries of the 43 mycotoxins spiked in 12 food categories were in the range of 60.3%-175.9% after internal standard correction, with relative standard deviations (RSDs) below 13.9%. For practical application, this method was utilized for 72 dietary samples collected from 6 provinces in the 6th China TDS. More than 80% of the samples were found contaminated by mycotoxins. DON, SMC, FB1, ZEN, BEA, ENNB1, and ENNB were most detected. CONCLUSIONS: The proposed methods with high sensitivity, accuracy, and robustness provide powerful tools for multi-mycotoxin monitoring and dietary exposure assessment, allowing 43 mycotoxins, including some emerging mycotoxins, to be accurately investigated in a total diet study for the first time.

Dietary exposure to fumonisins and ochratoxins in the Chinese general population during 2007-2020: Results from three consecutive total diet studies.

As widespread contaminants, fumonisins (FBs) and ochratoxins (OTs) in food may cause public health threat. In this study, the dietary exposures to FBs and OTs in the Chinese general population were investigated by means of a total diet study (TDS) approach. A total of 672 composite dietary samples were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) in three consecutive China total diet studies from 2007 to 2020. Combining with the national consumption data, estimated dietary exposure to FBs and OTs were assessed and compared with health-based guidance values (HBGVs). The estimated daily intakes (EDIs) of FBs were 55-237 ng/kg bw/day at the upper bound accounting 2.77%-17.4% of provisional maximum tolerable daily intake (PMTDI). Cereals were the greatest contributor to fumonisin exposure. For ochratoxin A (OTA), the EDIs were 0.65-5.72 ng/kg bw/day at the upper bound accounting 4.67%-40.8% of provisional tolerable weekly intake (PTWI). Although the estimated exposures were well below their respective HBGVs in general, they were found to exceed HBGVs in sporadic regions. Moreover, there was a remarkable increase in the dietary exposure to fumonisin B3 (FB3) and ochratoxin B (OTB) over the last decade that is worth further attention.

Dietary Exposure to Fumonisins and Health Risk Assessment in the Sixth China Total Diet Study - China, 2015-2020.

INTRODUCTION: Fumonisins are a group of widespread mycotoxins mainly existing in staple foods. Their toxicological effects on humans cause worldwide public health threat. During 2015-2020, the 6th China Total Diet Study (TDS) was conducted to study the dietary exposure to fumonisins in the Chinese adult population. METHODS: Fumonisins were analyzed by LC-MS/MS in 288 composite dietary samples collected from 24 provincial-level administrative divisions. After combining the national consumption data with analytical results, estimated daily intakes (EDIs) were assessed and compared with health-based guide values (HBGV). RESULTS: In the 6th China TDS, the highest fumonisin B (FBs) levels were found in staple foods/cereals among the 12 food categories. EDI of FBs was 104.9 ng/kg of body weight (bw)/day at the upper bound accounting 5.25% of the provisional maximum tolerable daily intake set by Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives. Among the 12 food categories, cereals and cereal products were the greatest contributor to FB exposure at 95%. CONCLUSION: Although the estimated exposure to FBs in the 6th China TDS were well below the HBGV for FBs in general, it was 2 times higher than the exposure in the 5th China TDS. Furthermore, the exposure to FB3 has increased remarkable and is worth further attention in China.

Synthesis of a biodegradable branched copolymer mPEG-b-PLGA-g-OCol and its pH-sensitive micelle.

An amphiphilic biodegradable branched copolymer, mPEG-b-PLGA-g-OCol, was synthesized by grafting copolymer (methoxy polyethylene glycol)-b-Poly (l,d-lactic-co-glycolic acid) (mPEG-b-PLGA) on oligomeric collagen (OCol), to form a branched structure with mPEG-b-PLGA as side chain and OCol as backbone. mPEG-b-PLGA and mPEG-b-PLGA-g-OCol were both amphipathic and can self-assemble into micelles in aqueous solution. The mPEG-b-PLGA-g-OCol micelles showed pH-sensitive behaviors and the particle size below 100 nm in slightly acidic environment such as tumor tissue milieu interieur to perform passive targeting. Observed by SEM, when the solution pH increased from 5 to 9, the morphology of mPEG-b-PLGA-g-OCol micelles changed from small spheres to larger ones to rings. For biodegradable mPEG-b-PLGA-g-OCol, the micelles will gradually degrade in body. Further, doxorubicin (DOX) was effectively loaded in the micelles with drug loading and encapsulation efficiency of 3.48% and 25.8%, respectively. To evaluate antineoplastic effect of DOX-laden micelles in vitro, MTT test, flow cytometry and CLSM were performed and found that DOX-laden micelles exhibited higher cellular proliferation inhibition against HeLa cells. These features indicated that the mPEG-b-PLGA-g-OCol micelles were potential drug carrier for cancer therapy.

[Evaluation based on the results of international proficiency tests for aflatoxins and analysis of keypoint detection].

OBJECTIVE: To analyze the results of international proficiency tests for aflatoxin determination and to identify the requirement of quality assurance and control in mycotoxin analysis. METHODS: By the use of Z-scores, the results of aflatoxins from international proficiency tests were analyzed and the critical control points in experimental operation were discussed. RESULTS: The absolute values of the Z-scores of aflatoxins were less than 2, indicating that the results from the laboratory were satisfactory. The sampling and testing method had very important effects on the detection results. CONCLUSION: The results of the international proficiency tests of aflatoxins suggested that to strengthen the critical control points in the experimental operation can effectively improve the accuracy and reliability of the determination results.

Unprecedentedly High Activity and/or High Regio-/Stereoselectivity of Fluorenyl-Based CGC Allyl-Type η3:η1-tert-Butyl(dimethylfluorenylsilyl)amido Ligated Rare Earth Metal Monoalkyl Complexes in Olefin Polymerization.

A series of fluorenyl-based constrained-geometry-configuration (CGC) allyl-type rare earth metal monoalkyl complexes bearing the divalent anionic η3:η1-tert-butyl(dimethylfluorenylsilyl)amido (η3:η1-FluSiMe2NtBu) ligand (η3:η1-FluSiMe2NtBu)Ln(CH2SiMe3)(THF)2 (1-3) have been synthesized via the alkane elimination reaction between the FluHSiMe2NHtBu ligand and rare earth metal tri(trimethylsilylmethyl) complexes Ln(CH2SiMe3)3(THF)n. Their structures are characterized by means of NMR spectrum, elemental analyses, and X-ray diffraction. These complexes 1-3 are isostructural and isomorphous, and each of them adopts a distorted-trigonal-bipyramidal configuration containing one η3:η1-FluSiMe2NtBu ligand, one CH2SiMe3 ligand, and two THF molecules. Unlike traditional CGC allyl-type rare earth metal complexes showing no or low activity and regio-/stereoselectivity in styrene or MMA polymerization, these complexes 1-3 exhibit high catalytic activities and/or high regio-/stereoselectivities in the cis-1,4-polymerization of isoprene and myrcene or in the syndiotactic polymerization of styrene under the aid of different activators (borate or borane) and AlR3. The in situ 1H NMR spectra suggest that the exchanges of chelating ligands such as alkyl groups and divalent anionic η3:η1-FluSiMe2NtBu ligands between rare earth metal centers and Al centers result in the formation of a heterobimetallic tetraalkylaluminate complex R2Al(µ-R)2Ln(R)(µ-R)2AlR2, which is activated by activators to form a divalent cationic species [Ln(µ-R)2AlR2]2+ as a catalytically active species in the coordination-insertion polymerization of olefins.

Development of Sensitive and Reliable UPLC-MS/MS Methods for Food Analysis of Emerging Mycotoxins in China Total Diet Study.

With the climatic changes that have taken place during the last decade, the spectrum of fungal pathogens as well as mycotoxins has considerably changed. As a result, some emerging mycotoxins have been shown to occur frequently in agricultural products. In this study, a sensitive and reliable method for the determination of 10 emerging mycotoxins (beauvericin, enniatin A, enniatin A1, enniatin B, enniatin B1, alternariol, alternariol monomethyl ether, altenuene, tentoxin, and tenuazonic acid) in 12 different food matrices (cereals, legumes, potatoes, meats, eggs, aquatic foods, dairy products, vegetables, fruits, sugars, beverages, and alcohol beverages) was developed and validated. After a simple extraction, a one-step sample clean-up by a HLB solid phase extraction (SPE) column was sufficient for all 12 food matrices prior to analysis with ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Isotope internal standards 13C-TeA, TEN-d3, and 13C-AFB2 were used for accurate quantification. Validation in terms of linearity, selectivity, sensitivity, accuracy, and precision (intra and inter-day variability) were evaluated for the 10 mycotoxins in all selected matrices. The sensitivity varied from 0.0004 to 0.3 ng mL-1 (limits of detection) and from 0.002 to 0.9 ng mL-1 (limits of quantitation). The recoveries of 10 mycotoxins in fortified samples were from 60.6% to 164% including very low spiking levels in all 12 food matrices, with relative standard deviations (RSDs) less than 12%. The proposed methodology was applied to the analysis of 60 samples collected from five provinces within the 6th China Total Diet Study with the results discussed in detail. The advantages of sensitivity, accuracy, and robustness made it a powerful tool for emerging mycotoxin monitoring and dietary exposure assessment.

[Occurrences of mycotoxins in human breast milk in 15 provinces in China in 2011].

OBJECTIVE: To investigate contamination levels of 10 mycotoxins in human breast milk from 15 provinces in China. METHODS: The human milk breast samples were collected from 15 provinces in China by aid of the second National Breast Milk Survey. After the pooled samples were made, concentrations of 10 main mycotoxins in breast milk pooled samples were measured by a UPLC-MS/MS with isotope dilution. RESULTS: aflatoxins B_1, aflatoxins M_1, deoxynivalenol, deepoxydeoxynivalenol, fumonisin B1 and fumonisin B2 were detected in breast milk samples of some provinces, while zearalenone, α-zearalenol, ß-zearalenol and ochratoxin A were not detected in all the samples. CONCLUSION: The average load levels in human body of mycotoxins in human milk form Chinese general populations are relatively low. However, the effects of aflatoxins, deoxynivalenol and fumonisins on health risks for the baby should be paid attention.

Synthesis and characterization of Eu(III) complexes of modified d-glucosamine and poly(N-isopropylacrylamide).

A series of chain-end functional polymers composed of poly(N-isopropylacrylamide) (PNIPAM) and 2-amino-2-deoxy-d-glucopyranose(d-glucosamine, GA) was synthesized via atom transfer radical polymerization (ATRP). Novel fluorescent complexes of glucosamine-PNI- PAM/Eu(III) were then formed by chelation of the polymers and europium(III) ions. The aqueous solutions of the polymers and its Eu(III) complexes exhibited a lower critical solution temperatures (LCSTs), and which were approximately equal to body temperature. Cell viability assays suggested that these thermosensitive polymers and Eu(III) complexes showed excellent biocompatibility in vitro.

Carbon dots for fluorescent detection of α-glucosidase activity using enzyme activated inner filter effect and its application to anti-diabetic drug discovery.

Recently, α-glucosidase inhibitor has been widely used in clinic for diabetic therapy. In the present study, a facile and sensitive fluorescent assay based on enzyme activated inner filter effect (IFE) on nitrogen-doped carbon dots (CDs) was first developed for the detection of α-glucosidase. The N-doped CDs with green emission were prepared by a one-step hydrothermal synthesis and gave the fluorescence quantum yield of 30%, which were used as the signal output. Through α-glucosidase catalysis, 4-nitrophenol was released from 4-nitrophenyl-α-d-glucopyranoside (NGP). Interestingly, the absorption of 4-nitrophenol and the excitation of CDs were completely overlapping. Due to its great molar absorptivity, 4-nitrophenol was capable of acting as a powerful absorber to affect the fluorescent signal of CDs (i.e. IFE). By converting the absorption signals into fluorescence signals, the facile fluorescence assay strategy could be realized for α-glucosidase activity sensing, which effectively avoided the complex modification of the surface of CDs or construction of the nanoprobes. The established IFE-based sensing platform offered a low detection limit of 0.01 U/mL (S/N = 3). This proposed sensing approach has also been expanded to the inhibitor screening and showed excellent applicability. As a typical α-glucosidase inhibitor, acarbose was investigated with a low detection limit of 10-8 M. This developed method enjoyed many merits including simplicity, lost cost, high sensitivity, good reproducibility and excellent selectivity, which also provided a new insight on the application of CDs to develop the facile and sensitive biosensor.

Simultaneous Determination of Multiple Intracellular Primary Metabolites by Ultrahigh Performance Liquid Chromatography Coupled with a Q Exactive HF Mass Spectrometer.

In this study, we established an ultrahigh-performance liquid chromatography-Q Exactive HF MS (UHPLC-HF MS) method for the simultaneous determination of 25 targeted metabolites relating to a broad coverage of central metabolic pathways, such as glycolysis pathway, tricarboxylic acid cycle (TCA), serine biosynthesis pathway (SSP), glutaminolysis pathway, and closely related biosynthetic reactions. A Shodex Asahipak NH2P-50 2D column was used to separate the targeted compounds, and Full MS + PRM detection using an electrospray ionization source in negative mode was employed. The method also integrated a sample purification step by passing through a Waters Sirocco 96 plate to remove protein impurities, ensuring the better resolution and sensitivity of the proposed method. The calibration curves of the method showed good linearity within the range of 1-10 000 µg L-1 with the correlation coefficient no less than 0.99. The method can be used for routine quantification of primary metabolites in a wide variety of cell extract samples. With the help of the method, for the first time, we successfully separate the isomers of 3-phosphoglycerate (3-PG) and 2-phosphoglycerate (2-PG), which lay the groundwork for the accurate quantification of metabolites of the tumor cells, the study of PGAM1 inhibitors, and the development of neotype anticancer drugs.

Facile and ultrasensitive fluorescence sensor platform for tumor invasive biomaker ß-glucuronidase detection and inhibitor evaluation with carbon quantum dots based on inner-filter effect.

Early detection and diagnosis have great practical significances for the effective prevention and treatment of cancer. In this study, we developed a novel, facile and ultra-sensitive fluorescence assay for the determination of tumor invasive biomarker ß-glucuronidase (GLU) based on the inner-filter effect (IFE). The nitrogen-doped carbon quantum dots (N-CQDs) with green photoluminescence were employed as the fluorophore in IFE, and 4-nitrophenyl-ß-D-glucuronide (PNPG) was used to act as GLU substrate, and GLU catalytic product (p-nitrophenol (PNP)) was capable of acting as the robust absorber in IFE to turn off the fluorescence of N-CQDs due to the complementary overlap between the absorption of PNP and the excitation of N-CQDs. Thus, signal of GLU activity could be recorded by the fluorescence intensity of N-CQDs. Unlike other fluorescence sensing mechanism such as fluorescence resonance energy transfer (FRET) or photoinduced electron transfer (PET), IFE has no requirement for electron or energy transfer process or any chemical modification of fluorophore, which makes our assay more flexible and simple. The proposed method exhibited a good linear relationship from 1UL(-1) to 60UL(-1) (R(2)=0.9967) with a low detection limit of 0.3UL(-1). This method was also successfully applied to the analysis of serum samples and the inhibitor screening from natural product. The developed sensor platform was proven to be reliable, facile, sensitive, and selective, making it promising as a candidate for GLU activity detection in clinic tumor diagnose and anti-tumor drug screening.

In vitro toxicological evaluation of ethyl carbamate in human HepG2 cells.

Ethyl carbamate (EC) is a multi-site carcinogen in experiment animals and probably carcinogenic to humans (IARC group 2A). The present study was designed to investigate the cytotoxicity effect of EC on human hepatoma G2 (HepG2) cells. The results revealed that EC inhibited the viability of HepG2 cells significantly in a dose-dependent manner. Further analysis indicated that high concentration of EC induced cell apoptosis, inhibited the G1 to S phase transition along with increased expression of p53 and p21 and decreased the expression of cyclin E and Cdk 2, but no significant change in p27 expression was observed, which were evidenced by both real time PCR and western blotting analyses. Moreover, the results of the DCFH-DA assay suggested that oxidative stress was involved in the cytotoxic effects of EC. Altogether, the present work indicated that p21, cyclin E and Cdk2, which were regulated by p53, might account for the effect of EC on cell viability and cell cycle arrest, but p27 was not involved in the pathway in HepG2 cells treated with EC.

End-Functionalized Poly(N-isopropylacrylamide) with d-Glucosamine through Different Initiator from C-1 and C-2 Positions via Atom Transfer Radical Polymerization.

Regioselective modification of d-glucosamine (2-amino-2-deoxy-d-glucopyranose, GA) through C-1 and C-2 positions to synthesized thermo-responsive D-Glucosamine-poly(N-iso-propylacrylamide) (PNIPAM) via atom transfer radical polymerization (ATRP) was investigated for the first time. Two different schemes of the synthesis for GA derivatives (GA-PNIPAM (i) and (ii)) with well-defined structures using 3,4,6-tri-o-acetyl-2-deoxy-2-phthalimido-ß-d-glucopyranose and 1,3,4,6-tetra-o-acetyl-2-amino-2-deoxy-ß-d-glucopyranose intermediates were examined. The GA-PNIPAM (ii) had an amino at C-2 position, while there was a hydroxyl in GA-PNIPAM (i) at this position. Both the resulting oligomers (i) and (ii) had a narrow dispersity, and no significant cytotoxic response of copolymers (i) and (ii) was observed in the cell line over the concentration range from 0.1 µg/mL to 1000 µg/mL at any of the exposure times. In addition, it was discovered that GA-PNIPAM (i) and (ii) inhibited the proliferation of Human Hepatocellular Carcinoma Cells HepG2 as the concentration and the time changed, and the inhibitory activity of polymer (ii) was higher than that of he (i). The results suggest that the GA-PNIPAM polymers show excellent biocompatibility in vitro.

Synthesis and characterization of aminoporphyrin-end-functionalized poly(N-isopropylacrylamide) with photodynamic and thermoresponsive effects.

The novel aminoporphyrin-end-functionalized poly(N-isopropylacrylamide) (PNIPAM) polymer H2N-TPP-PNIPAM (TPP = 5,10,15,20-tetraphenyl-21H,23H-porphyrin) behaves as a multifunctional platform that displays a photodynamic effect, thermosensitivity, and fluorescence properties. The polymer was designed by using an asymmetrical aminoporphyrin (i.e., H2N-TPP-Cl) as the initiator for the atom-transfer radical polymerization of N-isopropylacrylamide (NIPAM). The polydispersity index (PDI) obtained by gel-permeation chromatography indicated that the molecular-weight distribution was narrow (1.09

Synthesis and characterization of Eu(III) complexes of modified cellulose and poly(N-isopropylacrylamide).

A series of thermo-responsive copolymers of poly(N-isopropylacrylamide) (PNIPAM) and cellulose were synthesized via atom transfer radical polymerization (ATRP) using N-isopropylacrylamide as the monomer, cellulose acetate as the initiator, and CuCl/tris(2-dimethylaminoethyl)amine (Me6TREN) as a catalytic system. The resulting polymers had a narrow range of polydispersity indexes 1.27-1.37, and molecular weights of 8600-17,300 g mol(-1). Novel functional complexes of cellulose-g-PNIPAM/Eu(III) with excellent thermosensitive and fluorescent properties were then formed by the chelation of copolymers and europium(III) ions. The maximum emission intensity of the complexes at 613 nm was enhanced by a factor of approximately 10 relative to that of the corresponding Eu(III) complexes. Additionally, the lower critical solution temperatures (LCSTs) of cellulose-g-PNIPAM/Eu(III) were slightly greater than those of the copolymers.