Ultrathin WO3 Nanosheets/Pd with Strong Metal-Support Interactions for Highly Sensitive and Selective Detection of Mustard-Gas Simulants.

Exposure to mustard gas can cause damage or death to human beings, depending on the concentration and duration. Thus, developing high-performance mustard-gas sensors is highly needed for early warning. Herein, ultrathin WO3 nanosheet-supported Pd nanoparticles hybrids (WO3 NSs/Pd) are prepared as chemiresistive sulfur mustard simulant (e.g., 2-chloroethyl ethyl sulfide, 2-CEES) gas sensors. As a result, the optimal WO3 NSs/Pd-2 (2 wt % of Pd)-based sensor exhibits a high response of 8.5 and a rapid response/recovery time of 9/92 s toward 700 ppb 2-CEES at 260 °C. The detection limit could be as low as 15 ppb with a response of 1.4. Moreover, WO3 NSs/Pd-2 shows good repeatability, 30-day operating stability, and good selectivity. In WO3 NSs/Pd-2, ultrathin WO3 NSs are rich in oxygen vacancies, offer more sites to adsorb oxygen species, and make their size close to or even within the thickness of the so-called electron depletion layer, thus inducing a large resistance change (response). Moreover, strong metal-support interactions (SMSIs) between WO3 NSs and Pd nanoparticles enhance the catalytic redox reaction performance, thereby achieving a superior sensing performance toward 2-CEES. These findings in this work provide a new approach to optimize the sensing performance of a chemiresistive sensor by constructing SMSIs in ultrathin metal oxides.

Highly Efficient Separation of Ethanol Amines and Cyanides via Ionic Magnetic Mesoporous Nanomaterials.

Simple and efficient sample pretreatment methods are important for analysis and detection of chemical warfare agents (CWAs) in environmental and biological samples. Despite many commercial materials or reagents that have been already applied in sample preparation, such as SPE columns, few materials with specificity have been utilized for purification or enrichment. In this study, ionic magnetic mesoporous nanomaterials such as poly(4-VB)@M-MSNs (magnetic mesoporous silicon nanoparticles modified by 4-vinyl benzene sulfonic acid) and Co2+@M-MSNs (magnetic mesoporous silicon nanoparticles modified by cobalt ions) with high absorptivity for ethanol amines (EAs, nitrogen mustard degradation products) and cyanide were successfully synthesized. The special nanomaterials were obtained by modification of magnetic mesoporous particles prepared based on co-precipitation using -SO3H and Co2+. The materials were fully characterized in terms of their composition and structure. The results indicated that poly(4-VB)@M-MSNs or Co2+@M-MSNs had an unambiguous core-shell structure with a BET of 341.7 m2·g-1 and a saturation magnetization intensity of 60.66 emu·g-1 which indicated the good thermal stability. Poly(4-VB)@M-MSNs showed selective adsorption for EAs while the Co2+@M-MSNs were for cyanide, respectively. The adsorption capacity quickly reached the adsorption equilibrium within the 90 s. The saturated adsorption amounts were MDEA = 35.83 mg·g-1, EDEA = 35.00 mg·g-1, TEA = 17.90 mg·g-1 and CN-= 31.48 mg·g-1, respectively. Meanwhile, the adsorption capacities could be maintained at 50-70% after three adsorption-desorption cycles. The adsorption isotherms were confirmed as the Langmuir equation and the Freundlich equation, respectively, and the adsorption mechanism was determined by DFT calculation. The adsorbents were applied for enrichment of targets in actual samples, which showed great potential for the verification of chemical weapons and the destruction of toxic chemicals.

Magnetic mesoporous Fe3O4@nSiO2@mSiO2 nanoparticles for high-throughput mass spectrometry detection of hydrolyzed products of organophosphorus nerve agents.

Rapid and accurate detection of hydrolyzed products of organophosphorus nerve agents (OPNAs) is an important method to effectively confirm the use of these agents. OPNAs are rapidly hydrolyzed to the methyl phosphonates (MPs) in the environment, which can be used as environmental traceability marker for OPNAs. Herein, magnetic mesoporous materials combined with real-time in situ mass spectrometry (MS) were used to achieve high-throughput detection of MPs. Novel magnetic mesoporous nanoparticles Fe3O4@nSiO2@mSiO2 were synthesized via co-condensation of tetraethyl orthosilicate and cetyltrimethylammonium bromide (CTAB) on the surface of nonporous silica-coated Fe3O4 under alkaline conditions. CTAB templates were removed by the reflux of ethanol (0.0375 mM ammonium nitrate) to form mesoporous SiO2, which has a large specific surface area of 549 m2 g-1 and an excellent magnetization strength of 59.6 emu g-1. A quick, cost-effective, rugged, and safe magnetic preparation method, magnetic QuEChERS, was established with magnetic mesoporous nanoparticles (Fe3O4@nSiO2@mSiO2) as adsorption materials for direct analysis in real-time and tandem MS (DART-MS/MS) of MPs in environmental samples. The method exhibits good linearity (R2 > 0.992) in the range of 20.0-4.00 µg mL-1, the limits of detection were <5.00 ng mL-1, the limits of quantification were <20.0 ng mL-1, and the extraction recoveries were 70.2-98.1%, with relative standard deviations (RSDs) in the range of 1.97-10.6%. Additionally, using this method, analysis of 70 environmental samples could be completed within 20 min. Then, the M-QuEChERS-DART-MS/MS method was applied to the 52nd Organisation for the Prohibition of Chemical Weapons (OPCW) environmental spiked samples analysis, where the accuracy was 95.2-116%, and the RSD was 1.16-7.83%. The results demonstrated that Fe3O4@nSiO2@mSiO2 based on the QuEChERS method can quickly and efficiently remove the matrix of environmental samples and when coupled with the DART-MS/MS can achieve high-throughput determination of MPs in environmental samples.

Simultaneous Quantification of Biomarkers for Bis-(2-chloroethyl) Sulfide and 1,2-Bis(2-chloroethylthio) Ethane Exposure in Human Urine at Trace Exposure Levels by Gas Chromatography Tandem Mass Spectrometry via Simultaneous Incubation and Extraction.

Sulfur mustard [HD; bis-(2-chloroethyl) sulfide] and other analogues are a kind of highly toxic vesicant and have been prohibited by the Organization for the Prohibition of Chemical Weapons (OPCW) since 1997. Exposures to HD could generate several adducts in the plasma and hydrolysis products in the urine, which are widely applied as biomarkers to identify HD exposure in forensic analysis. Several methods have been developed for the detection of related biomarkers. However, most methods are based on complex derivatization, and not enough attention is paid to HD analogues. A modified and convenient analytical method reported herein includes simultaneous incubation and organic solvent extraction. The biomarkers such as thiodiglycol and 1,2-bis (2-hydroxyethylthio) are transferred to HD and 1,2-bis(2-chloroethylthio) ethane via hydrochloric acid at the appropriate temperature. The analytes are analyzed by gas chromatography tandem mass spectrometry (GC-MS/MS) with 2-chloroethyl ethyl sulfide (2-CEES) applied as the internal standard. The interday and intraday study according to FDA rules has been achieved to evaluate the accuracy and precision of the method. The two targets are detected with a good linearity (R2 > 0.99) in the concentration ranges from 5 to 1000 ng/mL and 10 to 1000 ng/mL, with small relative standard deviations (RSD ≤6.62% and RSD ≤6.93%) and favorable recoveries between 90.3 and 107.3% and between 89.4 and 108.7%, respectively. The established method can be used for retrospective detection of sulfur mustards in biological samples and successfully applied in the biomedical proficiency testing organized by the OPCW.

[Determination of cyanogen chloride in organic and water matrices by gas chromatography-mass spectrometry based on thiol derivatization].

Cyanogen chloride (ClCN) has been widely used in industrial production. ClCN is also listed in the Schedule of the Chemical Weapons Convention (CWC). The use of traditional colorimetric analysis or gas chromatography for the detection of ClCN has been characterized by low efficiency and poor sensitivity. In this study, a method was established for the qualitative analysis and quantitative detection of ClCN in organic and water matrices by gas chromatography-mass spectrometry (GC-MS) based on thiol derivatization. 1-Butylthiol was selected as the optimal derivatization reagent. The optimal temperature for thiol derivatization in the organic matrices was 40 ℃ and the reaction time was 10 min. The pH for derivatization was approximately 9. The ClCN in the organic matrices was directly analyzed by GC-MS after derivatization. The conditions of ClCN derivatization in the water matrices were the same as those in the organic matrices. After the derivatization of ClCN, headspace-solid phase microextraction (HS-SPME) was employed during sample preparation for water matrices. Different temperatures for HS-SPME were explored, and the optimal temperature was found to be 55 ℃. The product of thiol derivatization was confirmed as butyl thiocyanate. The main fragmentation patterns and mass spectrometric cleavage pathway were investigated by GC-MS/MS. The quantitative determination of ClCN in organic and water matrices was conducted via the internal standard and external standard methods, respectively. ClCN showed good linearity in the corresponding ranges in the organic and water matrices. The correlation coefficients for both matrices were greater than 0.99. The linearities of ClCN in the organic and water matrices were in the range of 20-2000 µg/L and 20-1200 µg/L, respectively. An organic sample and water samples from different substrates were selected to verify the accuracy and precision of the method at three spiked levels. The average spiked recoveries of ClCN in the organic sample and water samples were 87.3%-98.8% and 97.6%-102.2%, respectively. The corresponding relative standard deviations (RSDs, n=6) were 2.1%-4.7% and 2.8%-4.2%. The derivatization method established in this study showed good reaction specificity. The method was successfully applied in the analysis of samples obtained from the Organisation for the Prohibition of Chemical Weapons (OPCW). The method established in this study for the detection of ClCN showed high sensitivity and precision, and could aid in the analysis and detection of ClCN in the environment.

Quantitative detection of ricin in beverages using trypsin/Glu-C tandem digestion coupled with ultra-high-pressure liquid chromatography-tandem mass spectrometry.

The toxic protein of ricin has drawn wide attention in recent years as a potential bioterrorism agent due to its high toxicity and wide availability. For the verification of the potential anti-terrorism activities, it is urgent for the quantification of ricin in food-related matrices. Here, a novel strategy of trypsin/Glu-C tandem digestion was introduced for quantitative detection of ricin marker peptides in several beverage matrices using isotope-labeled internal standard (IS)-mass spectrometry. The ricin in beverages was captured and enriched by biotinylated anti-ricin polyclonal antibodies conjugated to streptavidin magnetic beads. The purified ricin was cleaved using the developed trypsin/Glu-C tandem digestion method and then quantitatively detected by ultra-high-pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with isotope-labeled T7A and TG11B selected as IS. The use of trypsin/Glu-C digestion allows shorter peptides, which are more suitable for MS detection, to be obtained than the use of single trypsin digestion. Under the optimized tandem digestion condition, except for T7A in the A-chain, two resulting specific peptides of TG13A, TG28A from the A-chain and two of TG11B, TG33B from the B-chain were chosen as novel marker peptides with high MS response. The uniqueness of the selected marker peptides allows for unambiguous identification of ricin among its homologous proteins in a single run. The MS response of the four novel marker peptides is increased by more than 10 times compared with that of individual corresponding tryptic peptides. Both the marker peptides of A-chain T7A and B-chain TG11B were selected as quantitative peptides based on the highest MS response among the marker peptides from their individual chains. The limit of detection (LOD) of ricin is 0.1 ng/mL in PBS and 0.5 ng/mL in either milk or orange juice. The linear range of calibration curves for ricin were 0.5-300 ng/mL in PBS, 1.0-400 ng/mL in milk, and 1.0-250 ng/mL in orange juice. The method accuracy ranged between 82.6 and 101.8% for PBS, 88.9-105.2% for milk, and 95.3-118.7% for orange juice. The intra-day and inter-day precision had relative standard deviations (%RSD) of 0.3-9.4%, 0.7-8.9%, and 0.2-6.9% in the three matrices respectively. Furthermore, whether T7A or TG11B is used as a quantitative peptide, the quantitative results of ricin are consistent. This study provides not only a practical method for the absolute quantification of ricin in beverage matrices but also a new strategy for the investigation of illegal use of ricin in chemical weapon verification tasks such as OPCW biotoxin sample analysis exercises.

Fluoride reactivation-enabled sensitive quantification of tabun adducts on human serum albumin by GC-MS/MS via isotope dilution.

Organophosphorus nerve agents inhibit the cholinesterase activity by phosphylation of the active site serine. The resulting phosphylated cholinesterase and adducts on human serum albumin (HSA) are appropriate biomarkers for nerve agents exposure. Several methods have been developed for the detection of nerve agents, including fluoride reactivation or alkaline cleavage. It was previously thought that some nerve agents adducts to HSA could not be detected via fluoride regeneration. In our study, the results showed that tabun (GA) adducts of HSA could be detected by fluoride regeneration. The sample preparation included acetone precipitation, washing and SPE. Deuterated tabun (d5-GA) was applied as the internal standard. The product of regenerated fluorotabun is detected with a good linearity (R2 > 0.997) in the concentration range from 0.02 to 100.0 ng/ml, small relative standard deviation (≤6.89%) and favorable recoveries between 94.8 and 106.3%. The established preparation confirmed the fluorotabun was regenerated from the GA-HSA adducts.

Aqueous Gold Nanoparticles Generated by AC and Pulse-Power-Driven Plasma Jet.

In this study, we developed a simple-to-use approach based on an atmospheric pressure plasma jet to synthesize aqueous Au nanoparticles (AuNP). Special attention was paid to the different reaction dynamics and AuNP properties under AC and pulse-power-driven plasma jets (A-Jet and P-Jet, respectively). The morphology of the AuNP, optical emissions, and chemical reactions were analyzed. Further, a copper mesh was placed above the reaction cell to evaluate the role of electrons and neutral species reduction. A visible color change was observed after the A-Jet treatment for 30 s, while it took 3 min for the P-Jet. The A-Jet treatment presented a much higher AuNP growth rate and a smaller AuNP diameter compared with the P-Jet treatment. Further analysis revealed an increase in chemical concentrations (Cl- and H2O2) and liquid conductivity after plasma treatment, with a higher increased amplitude for the A-Jet case. Moreover, the electrons alone had little effect on AuNP generation, while neutral species showed a clear Au+ reduction effect, and a unique coupling effect between both reactions was observed. The different reaction dynamics between the A-Jet and P-Jet were attributed to their different local heating effects and different discharge power during the reaction.

LC-HRMS Screening and Identification of Novel Peptide Markers of Ricin Based on Multiple Protease Digestion Strategies.

Both ricin and R. communisagglutinin (RCA120), belonging to the type II ribosome-inactivating proteins (RIPs-Ⅱ), are derived from the seeds of the castor bean plant. They share very similar amino acid sequences, but ricin is much more toxic than RCA120. It is urgently necessary to distinguish ricin and RCA120 in response to public safety. Currently, mass spectrometric assays are well established for unambiguous identification of ricin by accurate analysis of differentiated amino acid residues after trypsin digestion. However, diagnostic peptides are relatively limited for unambiguous identification of trace ricin, especially in complex matrices. Here, we demonstrate a digestion strategy of multiple proteinases to produce novel peptide markers for unambiguous identification of ricin. Liquid chromatography-high resolution MS (LC-HRMS) was used to verify the resulting peptides, among which only the peptides with uniqueness and good MS response were selected as peptide markers. Seven novel peptide markers were obtained from tandem digestion of trypsin and endoproteinase Glu-C in PBS buffer. From the chymotrypsin digestion under reduction and non-reduction conditions, eight and seven novel peptides were selected respectively. Using pepsin under pH 1~2 and proteinase K digestion, six and five peptides were selected as novel peptide markers. In conclusion, the obtained novel peptides from the established digestion methods can be recommended for the unambiguous identification of ricin during the investigation of illegal use of the toxin.

A sensitive quantification approach for detection of HETE-CP adduct after benzyl chloroformate derivatization using ultra-high-pressure liquid chromatography tandem mass spectrometry.

Sulfur mustard (HD) reacts with human serum albumin (HSA) at Cys34 and produces a long-term biomarker of HD exposure. Here, we present a novel, sensitive, and convenient method for quantification of HD exposure by detection of HD-HSA adducts using pronase digestion, benzyl chloroformate (Cbz-Cl) derivatization, and ultra-high-pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). The HSA in HD-exposed plasma in vitro was precipitated with acetone and digested (2 h, 50 °C) with pronase to form the alkylated dipeptide, S-hydroxyethylthioethyl-CysPro (HETE-CP). The HETE-CP adduct was derivatized with Cbz-Cl to generate N-carbobenzoxy HETE-CP (HETE-C(Cbz)P). The derivatized product was analyzed by UHPLC-MS/MS. HD surrogate, 2-chloroethyl ethyl sulfide (2-CEES), was introduced as a non-isotope internal standard (ISTD) instead of traditional d8-HD for quantification. The method was found to be linear between 1.00 and 200 ng/mL HD exposure (R2 > 0.998) with precision of ≤ 9.0% relative standard deviation (RSD) and accuracy ranged between 97.1 and 111%. The limit of detection (LOD) is 0.500 ng/mL (S/N~5), over 15 times lower than that of the previous method (7.95 ng/mL). Time-consuming affinity purification or solid phase extraction (SPE) is not needed in the experiment and the operation takes less than 5 h. This study provides a new strategy and useful tool for retrospective analysis of HD exposure by HETE-CP biomarker detection. Graphical abstract Flow diagram for quantification of sulfur mustard exposure by detection of HETE-CP dipeptide adduct after benzyl chloroformate derivatization using ultra-high-pressure liquid chromatography tandem mass spectrometry.

Zwitterionic stealth peptide-protected gold nanoparticles enable long circulation without the accelerated blood clearance phenomenon.

Poly(ethylene glycol) (PEG), which is considered as a gold standard for surface modification of nanoparticles in biomedical applications, has been reported to encounter the accelerated blood clearance (ABC) phenomenon after repeated administration. Herein, as an ideal substitute for PEG, a zwitterionic peptide sequence of alternating negatively charged glutamic acid (E) and positively charged lysine (K) was designed as a good candidate for surface modification of nanoparticles without the ABC phenomenon in vivo. PEG-protected gold nanoparticles (AuNP-PEG) suffered from a serious ABC phenomenon with very fast blood clearance after repeated injection. Meanwhile, the plasma IgM and IgG levels were significantly increased after the repeated injection of AuNP-PEG. However, zwitterionic stealth peptide-protected gold nanoparticles (AuNP-EK10) could avoid the activation of the ABC phenomenon. The increase of IgM and IgG levels was not observed after the repeated injection of AuNP-EK10. More interestingly, compared to AuNP-PEG, more AuNP-EK10 could be accumulated in tumor tissues after repeated injection of the nanoparticles to tumor-bearing nude mice, which might be especially important for the design of drug nanocarriers in cancer therapy.

Design and Proof of Programmed 5-Aminolevulinic Acid Prodrug Nanocarriers for Targeted Photodynamic Cancer Therapy.

5-Aminolevulinic acid (ALA), the precursor of photosensitizer protoporphyrin IX (PpIX), is a U.S. FDA-approved photodynamic therapeutic agent. However, realizing efficient delivery of ALA is still a big challenge as it is hydrophilic and cannot be recognized and selectively accumulated in tumor cells. In this study, matrix metalloproteinase-2 (MMP-2) and pH dual-sensitive ALA prodrug nanocarriers were constructed as a programmed delivery strategy for the targeted delivery of ALA. The nanocarriers were prepared by the co-modification of gold nanoparticles (AuNPs) with hydrazone-linked ALA and MMP-2-activatable cell-penetrating peptides (CPPs). Cationic CPP RRRRRRRR (R8) was shielded by zwitterionic stealth peptide EKEKEKEKEKEKEKEKEKEK (EK10) via MMP-2 substrate peptide PLGLAG. The zwitterionic stealth peptide EK10 is designed to endow ALA prodrug nanocarriers with strong antifouling ability and prolonged circulation time. Upon arriving at the tumor tissue, the shielded cationic CPP R8 can be activated by tumor-microenvironment-overexpressed MMP-2, which enabled enhanced cellular uptake of ALA. The results of drug loading and release, cellular uptake, PpIX generation and accumulation, photodynamic cytotoxicity, and photodynamic tumor inhibition demonstrated that such tumor-microenvironment-sensitive ALA prodrug nanocarriers could be considered as potential candidates for targeted photodynamic cancer therapy.

Zwitterionic stealth peptide-capped 5-aminolevulinic acid prodrug nanoparticles for targeted photodynamic therapy.

5-Aminolevulinic acid (ALA) is a FDA-approved photodynamic therapy (PDT) precursor of protoporphyrin IX (PpIX) used for treating various cancers. However, the internalization of ALA is a big challenge due to its hydrophilic nature and low specificity to cancer cells. In this work, ALA conjugated prodrug nanoparticles were prepared by conjugation of thiolated stealth peptide sequence CPPPPEKEKEKEKEKEDGR and hydrazone-containing ALA to gold nanoparticles (AuNPs). Remarkable anti-fouling ability of ALA prodrug nanoparticles in complex environment was achieved owing to the zwitterionic stealth peptide sequence EKEKEKEKEK. The release of ALA could be greatly accelerated upon incubation of ALA prodrug nanoparticles in lysosomal/endosomal pH (pH 5.5). Meanwhile, the cellular internalization could be greatly enhanced by RGD moieties. MTT results demonstrated that ALA prodrug nanoparticles exhibited better photodynamic cytotoxicity than free ALA after light irradiation, suggesting enhanced photodynamic therapeutic efficacy.

Intracellular Dual Fluorescent Lightup Bioprobes for Image-Guided Photodynamic Cancer Therapy.

An intracellular dual fluorescent light-up bioprobe with aggregation-induced emission features and endogenously producing photosensitizer protoporphyrin IX (PpIX) abilities is designed and synthesized. The bioprobe is nonemissive in physiological environment. However, the bioprobe can selectively light up cancer cells with blue fluorescence of tetraphenylene (TPE) and red fluorescence of PpIX, owing to the release of TPE and methyl aminolevulinate after targeted internalization by cancer cells. Moreover, upon endogenous generation and accumulation of PpIX in cancer cells, efficient photodynamic ablation of cancer cells after light irradiation is demonstrated with easy regulation for optimal therapeutic efficacy. The design of such dual fluorescent light-up bioprobes might provide a new opportunity for targeted and image-guided photodynamic cancer therapy.