Xianxiang Liu

An ultrasensitive electrochemical impedance sensor for a special BRCA1 breast cancer gene sequence based on lambda exonuclease assisted target recycling amplification

A label-free, target recycling electrochemical impedance spectroscopy (EIS) DNA sensor has been developed for detection of a model related to the BRCA1 breast cancer gene with a detection limit of 0.05 nM.

CE-ESI-MS coupled with dynamic pH junction online concentration for analysis of peptides in human urine samples.

In this article, an approach has been developed for the analysis of some small peptides with similar pI values by CE‐ESI‐MS based on the online concentration strategy of dynamic pH junction. The factors affected on the separation, detection and online enrichment, such as BGE, injection pressure, sheath flow liquid and separation voltage have been investigated in detail. Under the optimum conditions, i.e. using 0.5 mol/L formic acid (pH 2.15) as the BGE, preparing the sample in 50 mM ammonium acetate solution (pH 7.5), 50 mbar of injection pressure for 300 s, using 7.5 mM of acetic acid in methanol–water (80% v/v) solution as the sheath flow liquid and 20 kV as the separation voltage, four peptides with similar pI values, such as L‐Ala‐L‐Ala (pI=5.57), L‐Leu‐D‐Leu (pI=5.52), Gly‐D‐Phe (pI=5.52) and Gly‐Gly‐L‐Leu (pI=5.52) achieved baseline separation within 18.3 min with detection limits in the range of 0.2–2.0 nmol/L. RSDs of peak migration time and peak area were in the range of 1.45–3.57 and 4.93–6.32%, respectively. This method has been applied to the analysis of the four peptides in the spiked urine sample with satisfactory results.

Affinity capillary electrophoresis coupling with partial filling technique and field‐amplified sample injection for enantioseparation and determination of DL‐tetrahydropalmatine

A novel, simple and sensitive method for the enantioseparation and determination of DL‐tetrahydropalmatine (DL‐THP) was developed using ACE in combination with partial filling technique and field‐amplified sample injection. A chiral selector, i.e. BSA, was used for the enantioseparation of DL‐THP in ACE. Effects of BSA concentration, pH and separation voltage on the effectiveness of the enantiomer separation were evaluated. In an optimal condition, D‐ and L‐THP were completely enantio‐separated in less than 9 min by partially filling an electrophoretic capillary with 50 μmol/L BSA (50 mbar, 100 s) and carrying out an electrophoresis with 20 mmol/L phosphate buffer (pH 7.4) at 15 kV. The sensitivity was further improved by making use of field‐amplified sample injection to lower the LOD (defined as S/N=3) down to 6 ng/mL. Real samples were also tested and promising results for the determination of DL‐THP enantiomers were obtained.

Achyranthes bidentata polysaccharides activate the Wnt/β-catenin signaling pathway to promote chondrocyte proliferation

Achyranthes bidentata polysaccharides (ABPS) are the active components of Radix Achyranthis Bidentatae (AB), which has been extensively used in Traditional Chinese medicine (TCM) in the treatment of osteoarthritis (OA). Our previous study provided evidence that ABPS regulated the G1/S transition to promote chondrocyte proliferation. However, the precise mechanisms involved remain to be elucidated. In the present study, we aimed to investigate the effects of ABPS on the Wnt/β‑catenin signaling pathway in chondrocytes. Chondrocytes, obtained from the knee cartilage of Sprague-Dawley rats, were identified by type II collagen immunohistochemistry. ABPS upregulated the expression of Wnt-4, Frizzled-2, β-catenin and cyclin D1, and downregulated the expression of glycogen synthase kinase 3β (GSK-3β), as shown by reverse transcription PCR (RT-PCR) and western blot analysis. Using immunofluorescence, we also found that ABPS induced β-catenin nuclear translocation. Importantly, the expression of β-catenin and cyclin D1 was partly inhibited by Dickkopf-1 (DKK-1), an inhibitor of the Wnt/β-catenin signaling pathway. In addition, we found that ABPS increased the expression of type II collagen in chondrocytes. These results suggest that ABPS promote chondrocyte proliferation by activating the Wnt/β-catenin signaling pathway.

Achyranthes bidentata polysaccharides induce chondrocyte proliferation via the promotion of the G1/S cell cycle transition

Achyranthes bidentata polysaccharides (ABPS) are the major bioactive constituents of Radix Achyranthes bidentata (AB), which has been widely used in traditional Chinese medicine for the treatment of osteoarthritis. However, the molecular mechanisms behind the therapeutic effect of ABPS remain unclear. In the present study, chondrocytes were isolated from Sprague-Dawley rats. The effects of ABPS on the G1/S cell cycle transition in primary chondrocytes were investigated. The chondrocytes treated with and without ABPS were analyzed and it was observed that ABPS treatment was able to enhance chondrocyte proliferation in a dose- and time-dependent manner and promote the progression of chondrocyte cell cycle proliferation via the promotion of the G1 to S phase transition. Furthermore, using RT-PCR and western blot analysis, ABPS were observed as significantly upregulating the expression of cyclin D1 and the cyclin-dependent kinases (CDKs) CDK4 and CDK6. These results suggest that ABPS are able to promote chondrocyte proliferation via the promotion of the G1/S cell cycle transition.

Solid‐phase extraction‐field‐amplified sample injection coupled with CE‐ESI‐MS for online pre‐concentration and quantitative analysis of brain‐gut peptides

In order to improve the sensitivity of CE‐ESI‐MS for the analysis of brain‐gut peptides, a solid‐phase extraction combined with field‐amplified sample injection was used for the pre‐concentration of the brain‐gut peptides. Compared with the conventional pressure injection method, the sensitivity in the detection of brain‐gut peptides was improved more than 100‐fold. The possible factors affecting sample stacking, such as the sample matrix, the composition and the length of the water column, the types and the volumes of eluent, have been investigated in detail. Under the optimum conditions, the detectable concentration of brain‐gut peptides was found to be as low as 0.02 μM. A linear response concentration for the detection was developed in the range of 0.08–25 μmol/L. A real sample of human cerebrospinal fluids, which was spiked with brain‐gut peptides, was also examined in order to evaluate the reliability of the proposed approach. The recovery of the method was in a range from 69.2 to 85.4%. The method was found to be reliable, accurate and potentially applicable for clinical drug analysis.

Experimental study on the suppression of sodium nitroprussiate-induced chondrocyte apoptosis by Tougu Xiaotong Capsule (透骨消痛胶囊)-containing serum

ObjectiveTo study the mechanism of action of Tougu Xiaotong Capsule (透骨消痛胶囊, TGXTC) ex vivo in suppressing chondrocyte (CD) apoptosis induced by sodium nitroprussiate (SNP).MethodsThirty New Zealand rabbits, 2 months old, were randomized by lottery into five groups, six in each: the blank group treated with saline, the positive control group treated with Zhuanggu Guanjie Pill (壮骨关节丸, 70 mg/kg), and the three experimental groups, EGA, EGB, and EGC, treated with low dose (35 mg/kg), moderate dose (70 mg/kg), and high dose (140 mg/kg) of TGXTC, respectively. All treatments were administered via gastrogavage twice a day for 3 days. Arterial blood was collected from the abdominal aorta and drug or drug metabolites-containing serum was prepared. CDs obtained from knee joints of 16 four-week-old New Zealand rabbits were cultured to the third passage and confirmed by toluidine blue staining. SNP of various final concentrations (0, 0.5, 1.0, and 2.0 mmol/L) was used to induce CD apoptosis, and the dosage-effect relationship of SNP in inducing CD apoptosis was determined. Serum samples from the blank, control, and three dosages of TGXTC-treated rabbits were tested in the CD culture in the presence of SNP. Cell apoptosis was determined by Hoechst 33342 staining, viability of CDs was quantified by MTT, CD apoptosis rate was determined by annexin V-FITC/PI staining, levels of p53 and Bcl-2 mRNA expression in CDs were determined with RT-PCR, and contents of caspase-3 and caspase-9 proteins were determined by colorimetry.ResultsCD apoptosis was induced by SNP at all concentrations tested and in a dose-dependent manner. The SNP concentration of 1 mmol/L and treatment duration of 24 h appeared to be optimal and were selected for the study. Serum samples from the positive control rabbits and from the two higher doses of TGXTC-treated rabbits showed reduction of SNP-induced CD apoptosis, decrease in p53 mRNA expression, inhibition of catalytic activities of caspase-3 and caspase-9, and increase in Bcl-2 mRNA expression when compared with the serum from the blank group (P<0.05).ConclusionTGXTC-containing sera antagonized SNP-induced CD apoptosis and the molecular basis for the action was associated with up-regulation of Bcl-2, down-regulation of p53 expression, and inhibition of caspase-3 and caspase-9 catalytic activities.

A bio-inspired sensor coupled with a bio-bar code and hybridization chain reaction for Hg2+ assay

In this article, a bio-inspired DNA sensor is developed, which is coupled with a bio-bar code and hybridization chain reaction. This bio-inspired sensor has a high sensitivity toward Hg(2+), and has been used to assay Hg(2+) in the extraction of Bauhinia championi with good satisfaction.

Determination of the epimerization rate constant of amygdalin by microemulsion electrokinetic chromatography.

A new method for separation and determination of amygdalin and its epimer (neoamygdalin) in the epimerization of amygdalin by MEEKC is proposed. For the chiral separation of amygdalin and neoamygdalin, a running buffer composed of 80 mM sodium cholate, 5.0% v/v butan‐1‐ol, 0.5% v/v heptane and 94.5% v/v 30 mM Na2B4O7 buffer (pH 9.00) is proposed. Under optimum conditions, the basic separation of amygdalin and neoamygdalin can be achieved within 7 min. The calibration curve for amygdalin showed excellent linearity in the concentration range of 20–1000 μg/mL with a detection limit of 5.0 μg/mL (S/N=3). The epimerization rate constant of amygdalin in basic microemulsion was first determined by monitoring the concentration changes of amygdalin, and the epimerization rate constant of amygdalin was found to be 2×10−3 min−1 at 25°C under the above optimum microemulsion conditions.

Overexpression of Shox2 Leads to Congenital Dysplasia of the Temporomandibular Joint in Mice

Our previous study reported that inactivation of Shox2 led to dysplasia and ankylosis of the temporomandibular joint (TMJ), and that replacing Shox2 with human Shox partially rescued the phenotype with a prematurely worn out articular disc. However, the mechanisms of Shox2 activity in TMJ development remain to be elucidated. In this study, we investigated the molecular and cellular basis for the congenital dysplasia of TMJ in Wnt1-Cre; pMes-stop Shox2 mice. We found that condyle and glenoid fossa dysplasia occurs primarily in the second week after the birth. The dysplastic TMJ of Wnt1-Cre; pMes-stop Shox2 mice exhibits a loss of Collagen type I, Collagen type II, Ihh and Gli2. In situ zymography and immunohistochemistry further demonstrate an up-regulation of matrix metalloproteinases (MMPs), MMP9 and MMP13, accompanied by a significantly increased cell apoptosis. In addition, the cell proliferation and expressions of Sox9, Runx2 and Ihh are no different in the embryonic TMJ between the wild type and mutant mice. Our results show that overexpression of Shox2 leads to the loss of extracellular matrix and the increase of cell apoptosis in TMJ dysplasia by up-regulating MMPs and down-regulating the Ihh signaling pathway.