Biomedical subjects

Lei Su

Publications and source records attributed to Lei Su.

13 recordsLinked to original sources

PubMed2006

Electrochemical properties of carbon nanotube (CNT) film electrodes prepared by controllable adsorption of CNTs onto an alkanethiol monolayer self-assembled on gold electrodes.

This paper describes electrochemical properties, such as electrode reactivity, electrode dimensions, and interfacial capacitance, of multiwalled carbon nanotube (MWNT) film electrodes prepared by controllable adsorption of the MWNTs onto the self-assembled monolayer (SAM) of n-octadecyl mercaptan (C18H37SH) deposited onto Au electrodes. The adsorption of the MWNTs onto the SAM-modified Au electrode substantially restores heterogeneous electron transfer between bare Au electrode and redox species in solution phase that is almost totally blocked by the SAM of C18H37SH, and as a result, the prepared MWNT/SAM-modified electrode possesses good electrode reactivity without a remarkable barrier to heterogeneous electron transfer. In addition, the surface coverage of the MWNTs is readily controlled by adjusting the immersion time for the adsorption of the MWNTs onto the SAM of C18H37SH, which essentially endows the prepared MWNT/SAM-modified electrodes with tunable electrode dimensions ranging from a nanoelectrode array to a macro-sized conventional electrode. On the other hand, the MWNT/SAM-modified electrode is found to possess a largely reduced interfacial capacitance, as compared with the MWNT film electrodes prepared with existing methods by directly confining the MWNTs onto electrode surface. This demonstration offers a new approach to fabrication of stable MWNT film electrodes with excellent electrochemical properties that are believed to be very attractive for electrochemical studies and electroanalytical applications.

Journal Article↗

PubMed2006

[Study on the screening of lactamase and its fermentation conditions].

(-)-gamma-Lactam is one of the key starting materials for the synthesis (-)-cabovir and (-)-abacavir, which serve as two powerful antiviral agents. The production of gamma-lactam using enzymatic resolution of racemic gamma-lactam was attempted in the paper. 20 out of 69 strains capable of producing lactamase were screened from soil samples collected in several districts throughout Beijing; particularly N-actylphenylalanine was used as sole carbon source in the screening method. It was found by chiral HPLC analysis that strain L29-9 was able to enantioselectively hydrolyze the (+)-isomer in the racemic lactam, thus giving the desired (-)-gamma-lactam with high enantiomeric excess (> 70%). Ferment conditions of strain L29-9, including carbon source, nitrogen source, pH, and culturing time, were studied and the optimum conditions were as follows: citric acid 2 g/L, yeast extract 5 g/L, pH 7.0, culturing for 40h. Biotransformation using whole cells of the strain was inducted at 30 degrees C for 12h, giving (-)-gamma-lactam as enantiopure product with yield up to 40% and 99.5% e.e.

Amidohydrolases↗

PubMed2006

[Clinical value of monitoring CD14+ monocyte human leukocyte antigen (locus) DR levels in the early stage of sepsis].

OBJECTIVE: To explore the relationship of monitoring CD14(+) monocyte human leucocyte antigen (locus) DR (HLA-DR) and the outcome in the early stage of sepsis. METHODS: Thirty-six definitely diagnosed septic patients in intensive care unit (ICU) were included. CD14(+) monocyte HLA-DR levels were detected by flow cytometer on the first day of the study, and acute physiology and chronic health evaluation II (APACHE II) scores were evaluated. Their clinical values in predicting the outcome of the disease were assessed through correlation analysis. RESULTS: Among 36 sepsis patients CD14(+) monocyte HLA-DR level<30% was found in 6 patients (16.67%). The average APACHE II score was 24.17+/-4.45 (r=0.212, P=0.687), all of them die, CD14(+) monocyte HLA-DR level <40% was 27.78% (10/36), the scores of APACHE II score was 23.50+/-4.30 (r=-0.0251, P=0.484), and the mortality rate was 80% (8/10). CONCLUSION: CD14(+) monocyte HLA-DR level <30% is an immunosuppressive index. In predicting the outcome of sepsis, it might be better than APACHE II scores. Immunosuppression is primarily found in the early stage of sepsis, suggesting that the classical compensatory anti-inflammatory response syndrome (CARS) hypothesis needs to be revised and improved.

APACHE↗

PubMed2005

Microbend-induced mode coupling in a graded-index multimode fiber.

We present a theoretical analysis of the mode coupling effects at a microbend along a graded-index (GI) multimode fiber (MMF). By matching the incident and excited mode fields at the microbend, we obtain the coupling coefficients among the guided modes at different microbending conditions. The theoretical results compare well with the experimental results from near-field measurements on a GI MMF subject to microbending. The usefulness of our theory is demonstrated with two applications: (i) an explanation of the operation principle of a wavelength-switchable fiber laser that contains a fiber Bragg grating in a GI MMF and (ii) quantification of the function of a microbend-based mode scrambler.

Journal Article↗

PubMed2005

Continuous on-line monitoring of extracellular ascorbate depletion in the rat striatum induced by global ischemia with carbon nanotube-modified glassy carbon electrode integrated into a thin-layer radial flow cell.

This study describes a novel analytical system integrating in vivo microdialysis sampling with a radial thin-layer flow cell with a single-walled carbon nanotube (SWNT)-modified glassy carbon electrode as working electrode for continuous and on-line monitoring of ascorbate depletion in the rat striatum induced by global ischemia. The SWNTs, especially those after vacuum heat treatment at 500 degrees C, are found to be able to enhance the electron-transfer kinetics of ascorbate oxidation at a low potential (ca. -50 mV) and possess a strong ability against electrode fouling. These properties essentially make it possible to determine ascorbate with a good stability and high selectivity against catecholamines and their metabolites and other electroactive species of physiological levels. While being integrated with in vivo microdialysis to assemble an on-line analytical system, the electrode is proved useful for continuous and sensitive monitoring of the basal dialysate level of ascorbate and its depletion in the rat striatum induced by global ischemia. The basal dialysate level of ascorbate is determined to be 5.0 +/- 0.5 microM (n = 5) and a 50 +/- 10% (n = 3) depletion is recorded for the basal ascorbate after 4 h of global ischemia.

Animals↗

PubMed2005

Molecular films of water-miscible ionic liquids formed on glassy carbon electrodes: characterization and electrochemical applications.

This letter describes the formation and possible electrochemical applications of molecular films of water-miscible imidazolium-based ionic liquids (ILs) on glassy carbon (GC) electrodes. X-ray photoelectron spectroscopy (XPS) and electrochemical results indicate that the water-miscible ILs used in this study can interact with the GC electrode and form molecular films on the electrode surface. The formed molecular films are found to possess striking electrochemical properties such as electrocatalysis toward ascorbic acid (AA) and the capability to facilitate direct electron transfer of horseradish peroxidase (HRP). This demonstration would pave the way for new electrochemical applications of water-miscible ILs and is envisaged to be useful for the investigation of the electrochemical properties of water-miscible ILs in aqueous media provided the same counteranion is used as the supporting electrolyte.

Journal Article↗

PubMed2005

[Clinical value of computed tomography and fluorine-18 fluorodeoxyglucose positron remission tomography in diagnosis of mediastinal metastasis of non small cell lung cancer].

OBJECTIVE: To compare the clinical values of computed tomography (CT) and fluorine-18 fluorodeoxyglucose positron remission tomography (FDG-PET) in diagnosis of mediastinal metastasis of non-small cell lung cancer (NSCLC). METHODS: Sixty patients with respectable NSCLC underwent CT and FDG-PET with an interval of 2 weeks and then underwent thoracotomy for clearance of the lymph nodes or biopsy of the mediastinal lymph nodes via mediastinoscopy. The specimens of mediastinal lymph node underwent HE staining and PCNA/Ki67 immunohistochemical staining. The sensitivity, specificity, accuracy, positive prediction value, and negative prediction value in diagnosis of metastasis of mediastinal lymph nodes of these 2 procedures were compared. RESULTS: The sensitivity, specificity, accuracy, positive prediction value, and negative prediction value in diagnosis of metastasis of mediastinal lymph nodes were 92.3%, 87.5%, 91.2%, 96.0%, and 77.7% respectively for FDG-PET, and were 76.9%, 50.0%, 70.6%, 83.3%, and 40.0% respectively for CT. The sensitivity rate was 98% for CT plus FDG-PET. CONCLUSION: PET is superior to CT in diagnosis of metastasis of NSCLC to mediastinal lymph nodes. PET + CT significantly increases the sensitivity in diagnosis.

Aged↗

PubMed2005

Bioelectrochemically functional nanohybrids through co-assembling of proteins and surfactants onto carbon nanotubes: facilitated electron transfer of assembled proteins with enhanced faradic response.

Preparation and bioelectrochemical properties of functional nanohybrids through co-assembling of hemeproteins (i.e., horseradish peroxidase, hemoglobin, myoglobin and cytochrome c) and surfactants onto carbon nanotubes (CNTs) are described. The prepared protein-surfactant-CNT nanohybrids are found to possess facilitated interfacial electron transfer of the proteins with enhanced faradic responses. The enhancements are ascribed for the first time to the properties of the surfactants for facilitation of protein electrochemistry and the improved portion of electroactive proteins assembled, of which the latter assignment is closely associated with the electrochemical and structural properties of the nanotubes and the three-dimensional architecture of the CNT film confined onto the glassy carbon electrode. It is proposed that the single and/or small bundles of the nanotubes in the CNT film electrode can be rationally functionalized with surfactants to be functional nanoelectrodes capable of facilitating electron transfer of proteins. The three-dimensional confinement of these functional nanowires onto the GC electrode essentially increases the portion of electroactive proteins assembled in the nanohybrids. These properties of the protein-surfactant-CNT nanohybrids, combined with the bioelectrochemical catalytic activity, could make them useful for development of bioelectronic devices and investigation of protein electrochemistry at functional interfaces.

Carbon↗

PubMed2005

Cryopreservation of cynomolgus monkey (Macaca fascicularis) spermatozoa in a chemically defined extender.

AIM: To establish a method for cynomolgus monkey sperm cryopreservation in a chemically defined extender. METHODS: Semen samples were collected by electro-ejaculation from four sexually mature male cynomolgus monkeys. The spermatozoa were frozen in straws by liquid nitrogen vapor using egg-yolk-free Tes-Tris mTTE synthetic extender and glycerol as cryoprotectant. The effects of glycerol concentration (1 %, 3 %, 5 %, 10 % and 15 % [v/v]) and its equilibration time (10 min, 30 min, 60 min and 90 min) on post-thaw spermatozoa were examined by sperm motility and sperm head membrane integrity. RESULTS: The post-thaw motility and head membrane integrity of spermatozoa were significantly higher (P0.05) for 5 % glycerol (42.95 +/- 2.55 and 50.39+/- 2.42, respectively) than those of the other groups (1%: 19.19 +/- 3.22 and 24.84 +/- 3.64; 3%: 34.23 +/- 3.43 and 41.37 +/- 3.42; 10%:15.68 +/- 2.36 and 21.39 +/- 3.14; 15%: 7.47 +/- 1.44 and 12.90 +/- 2.18). The parameters for 30 min equilibration(42.95 +/- 2.55 and 50.39 +/- 2.42) were better (P0.05) than those of the other groups (10 min: 31.33 +/- 3.06 and 38.98 +/- 3.31; 60 min: 32.49 +/- 3.86 and 40.01 +/- 4.18; 90 min: 31.16 +/- 3.66 and 38.30 +/- 3.78). Five percent glycerol and 30 min equilibration yielded the highest post-thaw sperm motility and head membrane integrity. CONCLUSION: Cynomolgus monkey spermatozoa can be successfully cryopreserved in a chemically defined extender, which is related to the concentration and the equilibration time of glycerol.

Animals↗

PubMed2005

Electrochemistry and electroanalytical applications of carbon nanotubes: a review.

This review addresses recent developments in electrochemistry and electroanalytical chemistry of carbon nanotubes (CNTs). CNTs have been proved to possess unique electronic, chemical and structural features that make them very attractive for electrochemical studies and electrochemical applications. For example, the structural and electronic properties of the CNTs endow them with distinct electrocatalytic activities and capabilities for facilitating direct electrochemistry of proteins and enzymes from other kinds of carbon materials. These striking electrochemical properties of the CNTs pave the way to CNT-based bioelectrochemistry and to bioelectronic nanodevices, such as electrochemical sensors and biosensors. The electrochemistry and bioelectrochemistry of the CNTs are summarized and discussed, along with some common methods for CNT electrode preparation and some recent advances in the rational functionalization of the CNTs for electroanalytical applications.

Journal Article↗

PubMed2004

Sol-gel-derived ceramic-carbon nanotube nanocomposite electrodes: tunable electrode dimension and potential electrochemical applications.

Nanocomposite electrodes made of sol-gel-derived ceramic-carbon nanotube are fabricated by doping mutliwalled carbon nanotubes (MWNTs) into a silicate gel matrix. The electrochemical behavior and potential electrochemical applications of the ceramic-carbon nanotube nanocomposite electrodes (CCNNEs) are also studied. The as-prepared CCNNEs exhibit a tunable dimension ranging from conventional electrode to nanoelectrode ensemble (NEE), depending on the amount of the MWNT dispersed in the silica sol and finally doped within the gel matrix. A high content of the MWNT (i.e., higher than 1.5 mg/mL in the sol) leads to the formation of the CCNNE characteristic of an electrode of conventional dimension, while a low content (typically lower than 0.10 mg/mL) essentially yields the CCNNE like a nanoelectrode ensemble. The NEE is demonstrated to possess good electrocatalytic activity toward the oxidation of ascorbic acid (AA), and the CCNNE of conventional dimension is found to possess remarkable electrocatalytic activity toward the oxidation of glutathione (both reduced and oxidized forms, GSH and GSSG). These properties of the CCNNEs essentially offer a new electrochemical approach for the detection of AA, GSH, and GSSG. The possible essence of the tailor-made dimensions of the CCNNEs is also presented and discussed.

Journal Article↗

PubMed2004

Differential expression of S100 gene family in human esophageal squamous cell carcinoma.

PURPOSE: To study the differential expression of the S100 gene family at the RNA level in human esophageal squamous cell carcinoma (ESCC), and to find the relationship of the S100 gene family with ESCC. METHODS: Firstly, the specific primers were designed for the different S100 genes with Software Primer 3, which required that both primer sequences of each S100 gene were from two different exons respectively. Then, the differential expression of 16 S100 genes was examined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) in 62 cases of ESCC versus the corresponding normal esophageal mucosa. All RT-PCR products were analyzed by 1.5% agarose gel. With Fluor-S MultiImager and Multi-Analyst software, the electrophoresis images were evaluated with statistics analysis using SAS 8.1 software. RESULTS: Eleven out of 16 S100 genes were significantly downregulated ( p<0.05) in ESCC versus the normal counterparts such as S100A1, S100A2, S100A4, S100A8, S100A9, S100A10, S100A11, S100A12, S100A14, S100B, and S100P genes. Only the S100A7 gene in the S100 family was markedly upregulated ( p<0.05). Moreover, the S100B gene was significantly correlated with histological differentiation of ESCC ( p=0.0247), and the deregulation of some S100 genes was closely correlated ( p<0.05), such as S100A10/S100A11, S100A2/S100A8, S100A2/S100A14, S100A8/S100A14, and S100A2/S100P etc. CONCLUSIONS: The S100 gene family is closely associated with ESCC.

Carcinoma, Squamous Cell↗

PubMed2002

Vitrification of Yunnan Yellow Cattle oocytes: work in progress.

The objective of this study was to provide a simple cryopreservation method for oocytes from Yunnan Yellow Cattle and facilitate preservation efforts in this native Chinese breed, which is threatened by agricultural modernization. Cumulus-oocyte complexes (COCs) were collected from slaughterhouse ovaries and matured in vitro for 22-24 h, then selected for cryopreservation. Vitrification in open pulled straws (OPS) or in microdrops on a cooled metal surface (solid surface vitrification, SSV) was compared. The OPS vitrification solution consisted of 20% ethylene glycol (EG) and 20% DMSO. The SSV solution was a mixture of 35% EG, 5% polyvinyl-pyrrolidon (PVP) and 0.4 M trehalose. Vitrified and warmed oocytes were either fertilized in vitro or parthenogenetically activated. The rates of cleavage and development to blastocysts of fertilized oocytes following OPS versus SSV were not statistically different (38.3 and 12.5% versus 35.8 and 6.0%, respectively). The corresponding rates of parthenogenetic development to blastocysts were also not different (8.2 versus 3.5%, respectively). Development to blastocysts of non-vitrified controls following fertilization was significantly higher than that of the vitrified oocytes (22.6%, P < 0.05). These results demonstrate for the first time, that although both OPS and SSV procedures reduced embryonic development, Yunnan Yellow Cattle oocytes are capable of developing to blastocysts following cryopreservation.

Animals↗