Simultaneous determination of gallic acid, methyl gallate, and 1,3,6-tri-O-galloyl-ß-d-glucose from Turkish galls in rat plasma using liquid chromatography-tandem mass spectrometry and its application to pharmacokinetics study.

Turkish galls (TG) is a traditional Uygur medicine typically used in clinics for dental disease and chronic ulcerative colitis. In this study, a novel liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous quantification of gallic acid, methyl gallate, and 1,3,6-tri-O-galloyl-ß-d-glucose in rat plasma, which are the major bioactive compounds of TG. After a feasible protein precipitation using acetonitrile for sample preparation, chromatographic separation was performed with a BDS Hypersil C18 column (2.1 × 100 mm, 5 µm) at 30°C, and water containing 10 mmol of ammonium acetate and acetonitrile was used as the mobile phase with a flow rate of 0.3 mL/min. The MS detector was operated in the selective reaction monitoring with negative-ionization mode. The results of the method validation, including selectivity, linearity, accuracy, precision, extraction recovery, matrix effect, and stability of the compounds in the biosamples, were all within the current acceptance criteria. The established method was successfully applied to the pharmacokinetics study of three analytes in rats after an oral administration of TG extract and laid the foundation for studying the active components and mechanism of TG in vivo.

Construction of H2O2-responsive asymmetric 2D nanofluidic channels with graphene and peroxidase-mimetic V2O5 nanowires.

The flexible two-dimensional (2D) nanosheet structure, high specific surface, and unique electrical properties make graphene an emerging nano-building block for molecule-responsive nanochannels. Herein, we report a novel graphene and V2O5 nanowire-based porous asymmetric membrane, which shows excellent catalytic performance and sensitive and quick response for H2O2. Poly(diallyldimethylammonium chloride)-functionalized graphene nanosheets were made into restacked lamellar film with porous structure and high anion selectivity. V2O5 nanowire, a kind of enzyme-mimetic nanomaterial, was mounted on one side of the graphene membrane through a sequential vacuum filtration method. The V2O5 nanowires on the membrane have high catalytic activities for H2O2 reduction, with the Michealis-Menten constant (KM) of 1.74 mM, better than various reported peroxidase-based nanocomposites and peroxidase mimics. This composite membrane showed quick response to H2O2 within 5 s, with good reproducibility and high operational stability. The responsive linear range was from 10 µM to 1 mM, with the detection limit of 9.5 µM. This fabrication of 2D layered nanomaterials and enzyme mimics could be extended for developing novel smart molecule-responsive devices. Graphical abstract ᅟ.

Sensitive nanochannel biosensor for T4 polynucleotide kinase activity and inhibition detection.

5'-Polynucleotide kinase is a crucial class of enzyme that catalyzes the phosphorylation of nucleic acids with 5'-hydroxyl termini. This process regulates many important cellular events, especially DNA repair during strand damage and interruption. The activity and inhibition of nucleotide kinase have proven to be an evident effect on cellular nucleic acid regulation and metabolism. Here, we describe a novel nanochannel biosensor for monitoring the activity and inhibition of T4 polynucleotide kinase (PNK), a famous member of the 5'-kinase family playing a major role in the cellular responses to DNA damage. On the basis of the functionalized nanochannel system and coupled λ exonuclease cleavage reaction, the nanochannel-sensing platform exhibits high sensitivity and convenience toward kinase analysis. Biotin-labeled dsDNA effectively blocks the streptavidin-modified nanochannel through forming a closely packed arrangement of DNA structure inside the channel. When dsDNA is phosphorylated by PNK and then immediately cleaved by λ exonuclease, the pore-blocking effect almost disappears. This PNK-induced microstructural distinctness can be directly and accurately monitored by the nanochannel system, which benefits from its high sensitivity to the change of the effective pore size. Furthermore, modification convenience and mechanical robustness also ensure the stability of the test platform. This as-proposed strategy exhibits excellent analytical performance in both PNK activity analysis and inhibition evaluation. The simple and sensitive nanochannel biosensor shows great potential in developing on-chip, high-throughput assays for fundamental biochemical process research, molecular-target therapies, and clinic diagnostics.

Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: an observational cohort study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) causes severe community and nosocomial outbreaks. Comprehensive data for serial respiratory viral load and serum antibody responses from patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not yet available. Nasopharyngeal and throat swabs are usually obtained for serial viral load monitoring of respiratory infections but gathering these specimens can cause discomfort for patients and put health-care workers at risk. We aimed to ascertain the serial respiratory viral load of SARS-CoV-2 in posterior oropharyngeal (deep throat) saliva samples from patients with COVID-19, and serum antibody responses. METHODS: We did a cohort study at two hospitals in Hong Kong. We included patients with laboratory-confirmed COVID-19. We obtained samples of blood, urine, posterior oropharyngeal saliva, and rectal swabs. Serial viral load was ascertained by reverse transcriptase quantitative PCR (RT-qPCR). Antibody levels against the SARS-CoV-2 internal nucleoprotein (NP) and surface spike protein receptor binding domain (RBD) were measured using EIA. Whole-genome sequencing was done to identify possible mutations arising during infection. FINDINGS: Between Jan 22, 2020, and Feb 12, 2020, 30 patients were screened for inclusion, of whom 23 were included (median age 62 years [range 37-75]). The median viral load in posterior oropharyngeal saliva or other respiratory specimens at presentation was 5·2 log10 copies per mL (IQR 4·1-7·0). Salivary viral load was highest during the first week after symptom onset and subsequently declined with time (slope -0·15, 95% CI -0·19 to -0·11; R2=0·71). In one patient, viral RNA was detected 25 days after symptom onset. Older age was correlated with higher viral load (Spearman's ρ=0·48, 95% CI 0·074-0·75; p=0·020). For 16 patients with serum samples available 14 days or longer after symptom onset, rates of seropositivity were 94% for anti-NP IgG (n=15), 88% for anti-NP IgM (n=14), 100% for anti-RBD IgG (n=16), and 94% for anti-RBD IgM (n=15). Anti-SARS-CoV-2-NP or anti-SARS-CoV-2-RBD IgG levels correlated with virus neutralisation titre (R2>0·9). No genome mutations were detected on serial samples. INTERPRETATION: Posterior oropharyngeal saliva samples are a non-invasive specimen more acceptable to patients and health-care workers. Unlike severe acute respiratory syndrome, patients with COVID-19 had the highest viral load near presentation, which could account for the fast-spreading nature of this epidemic. This finding emphasises the importance of stringent infection control and early use of potent antiviral agents, alone or in combination, for high-risk individuals. Serological assay can complement RT-qPCR for diagnosis. FUNDING: Richard and Carol Yu, May Tam Mak Mei Yin, The Shaw Foundation Hong Kong, Michael Tong, Marina Lee, Government Consultancy Service, and Sanming Project of Medicine.

The application of nanomaterials in controlled drug delivery for bone regeneration.

Bone regeneration is a complicated process that involves a series of biological events, such as cellular recruitment, proliferation and differentiation, and so forth, which have been found to be significantly affected by controlled drug delivery. Recently, a lot of research studies have been launched on the application of nanomaterials in controlled drug delivery for bone regeneration. In this article, the latest research progress in this area regarding the use of bioceramics-based, polymer-based, metallic oxide-based and other types of nanomaterials in controlled drug delivery for bone regeneration are reviewed and discussed, which indicates that the controlling drug delivery with nanomaterials should be a very promising treatment in orthopedics. Furthermore, some new challenges about the future research on the application of nanomaterials in controlled drug delivery for bone regeneration are described in the conclusion and perspectives part.

Sequence analysis of six enterovirus 71 strains with different virulences in humans.

Enterovirus 71 (EV71) infection is the main cause of hand, foot and mouth disease (HFMD) and has been associated with severe neurological diseases resulting in high mortalities. In this study, six EV71 strains isolated from patients with different clinical symptoms were sequenced and analyzed in a mouse model of EV71 infection. In a phylogenetic tree, based on the complete VP1 gene sequence, all six strains grouped into the C4 genotype. The sequence analysis revealed that there are nucleotide changes clustered in the internal ribosome entry site (IRES) element of the 5'-nontranslated region (5'-NTR), as well as amino acid differences clustered in the non-structural proteins. Importantly, we identified a unique amino acid difference (Val(1994)-Ile(1994)) that distinguished the more virulent strains, Anhui1 (Ah1), Henan1 (Hn1) and Henan2 (Hn2) from the less virulent strains, Chongqing1 (Cq1), Chongqing2 (Cq2) and Chongqing3 (Cq3). This amino acid difference is located in the finger domain of the viral RNA-dependent RNA polymerase 3D (3D(pol)). Furthermore, two-day-old Balb/c mice were inoculated with the Ah1, Hn1, Hn2, Cq1, Cq2 and Cq3 isolates by the intracerebral or intraperitoneal routes. All of the mice inoculated with Ah1, Hn1 and Hn2 isolates developed hind-leg paralysis and subsequently died. Mice inoculated with the Cq1, Cq2 or Cq3 isolates survived throughout the 21-day observation period. These results show that clinical isolates of EV71 associated with disease of different severity in humans have characteristic sequence differences and cause different mortality rates when inoculated into mice. These data also provide a rational basis to investigate the molecular determinants of EV71 pathogenesis using a reverse genetic approach.

[Transfection with a novel cationic gene carrier: PEI-PBLG].

This study mainly deals with cell transfection and cytotoxicity for PEI(10kD)-PBLG, a novel cationic copolymer, to observe its potential as a gene carrier. Size measurement and SEM were used to show the modality of the PEI-PBLG/pDNA complexes. Cytotoxicity of PEI (10kD)-PBLG was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay and compared with PEI(25kD)-PBLG, PEI(10kD), and PEI(25kD). Furthermore, pEGFP that can express the enhanced green fluorescent protein was chosen as a reporter to observe the transfection efficiency directly. Then, PEI (10kD)-PBLG/pEGFP complexes were transfected into several cell lines, such as Hela, COS-7, Vero-E6, and ECV-304, and effects of the transfection conditions were evaluated. The efficiencies were measured by FACS. Size measurement of complex particles indicated that PEI-PBLG/pDNA tended to form smaller nanoparticles compared with PEI/pDNA. The representative size of the PEI(10kD)-PBLG/pDNA complex was approximately 100 - 200 nm. SEM images showed that the particles were condense and compact. This can be suitable for their entry into cells. Cytotoxicity studies suggested that PEI (10kD)-PBLG had considerably lower toxicity than the other three materials. In the transfection tests, PEI (10kD)-PBLG/pDNA complexes could be transfected into all the cell lines that were tested. These provided the highest level of EGFP expression (45.02%) in Hela cells, which was considerably higher than that of PEI(10kD)/pEGFP (29.16%). Being less affected by the serum during transfection, PEI-PBLG/pDNA complexes offered greater biocompatibility than PEI. PEI-PBLG copolymer reduces the cytotoxicity of PEI, improves the transfection efficiency, and offers greater biocompatibility than PEI. It shows considerable potential as an efficient nonviral carrier for gene delivery.

Transendothelial movement of liposomes in vitro mediated by cancer cells, neutrophils or histamine.

A two-chamber culture system has been used to examine the ability of small liposomes to cross an endothelial cell barrier in response to various stimuli. Transendothelial transit of liposomes was almost negligible in the presence of intact, healthy endothelial cells (EC). Addition of histamine induced a concentration-dependent increase in the movement of liposomes across the EC monolayer. In the presence of polymorphonuclear neutrophils (PMNs), migrating in response to a chemotactic gradient of N-Formil-Met-Leu-Phe (fMLP), both liposomes and IgG crossed EC monolayer by a paracellular pathway, largely independent of an association with the PMNs. The presence of cancer cell, growing in the lower chamber or the presence of cancer cell-conditioned media, also resulted in the passage of liposome across the EC. We conclude that EC monolayers are sufficiently disrupted by several physiologically relevant stimuli to allow for the transendothelial passage of liposomes. These results have important implications for the therapeutic use of liposome in the treatment of cancer or other inflammatory processes.