Human Gastric Carcinoma BGC-823 Research Articles

Ursolic Acid Protects Against Proliferation and Inflammatory Response in LPS-Treated Gastric Tumour Model and Cells by Inhibiting NLRP3 Inflammasome Activation.

BackgroundInflammation is considered as one of the hallmarks of cancer development and progression. Ursolic acid (UA) showed strong effects as an anti-inflammatory and antioxidant. However, the anti-cancer effects of ursolic acid require further study.MethodsThis study aimed to investigate the role of ursolic acid in a lipopolysaccharide (LPS)-treated gastric tumour mouse model and in a human gastric carcinoma cell line (BGC-823 cells). This study also aimed to confirm whether ursolic acid can protect against proliferation and the inflammatory response induced by LPS, by inhibiting the activation of the NLRP3 inflammasome via the NF-κB pathway.ResultsThe present study demonstrated that ursolic acid significantly attenuated LPS-treated proliferation in a gastric tumour mouse model and the human gastric carcinoma BGC-823 cell line, reduced the expression of the NLRP3 inflammasome and suppressed the release of pro-inflammatory cytokines. In addition, ursolic acid inhibited the LPS-induced activation of NF-κB. Furthermore, the NF-κB pathway regulated the activation of the NLRP3 inflammasome.ConclusionIn conclusion, these results demonstrated that ursolic acid could suppress proliferation and the inflammatory response in an LPS-induced mouse gastric tumour model and human BGC-823 cells by inhibiting the activation of the NLRP3 inflammasome via the NF-κB pathway. This indicates that ursolic acid can be a potential therapeutic agent for the treatment of gastric cancer.

Concomitant modulation of PTEN and Livin in gastric cancer treatment.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and Livin are important in the development of gastric cancer (GC). PTEN and Livin are involved in the regulation of tumor cell proliferation, migration and apoptosis. The modulation of PTEN or Livin has been investigated extensively in various cancer models. However, no studies have been performed to evaluate the combined effect of concurrently modulating these two genes on the development of GC. In the present study, the BGC823 human gastric carcinoma cell line was transfected with a dual gene modified vector (pCL-neo-PTEN-siLivin) in parallel with single gene modified vectors (pCL‑neo‑PTEN or pRNAT‑U6.1‑siLivin), and an empty control vector. Dual gene modulation (pCL‑neo‑PTEN‑siLivin) had a more marked effect on the inhibition of cell proliferation, induction of apoptosis, and reduction of cell penetration in Matrigel, compared with either single gene alone or empty vector transfection. In a xenograft nude mouse model, the inoculation of pCL‑neo‑PTEN‑siLivin‑transfected BGC823 cells led to a markedly reduced tumor burden, compared with that in all other inoculation groups. In conclusion, the overexpression of PTEN concomitant with Livin gene silencing was confirmed as a feasible and effective invitro and invivo gene modulation method, which may represent a potential therapeutic strategy for the treatment of GC.

125I-F56 Peptide as Radioanalysis Agent Targeting VEGFR1 in Mice Xenografted with Human Gastric Tumor.

125I-Radiolabeled F56 peptide was designed as a radioactive analogue of F56 (peptide WHSDMEWWYLLG) to bind with VEGFR1 receptor. It was synthesized in high radiochemical yield and specific activity. The in vitro stability of 125I-F56 was tested, and the bioactivity of 125I-F56 was confirmed by both cell uptake and binding affinity measurement in VEGFR1 positive BGC-823 cells. The time-radioactivity relationship and biodistribution of 125I-F56 tracer were conducted using nude mice bearing human gastric carcinoma BGC-823, by noninvasive micro-SPECT/CT imaging. The tracer's tumor uptake was further confirmed by autoradiography and HE stain of 125I-F56 in tumor tissues ex vivo. Those results demonstrated that 125I-F56 holds great potential as a diagnostic agent in both molecular imaging and radioanalysis probe for gastric cancer.

Synthesis and antitumor activity of novel substituted uracil-1′(N)-acetic acid ester derivatives of 20(S)-camptothecins

A series of novel substituted uracil-1′(N)-acetic acid esters (6–20) of camptothecins (CPTs) were synthesized by the acylation method. These new compounds were evaluated for in vitro antitumor activity against tumor cell lines, A549, Bel7402, BGC-823, HCT-8 and A2780. In vitro results showed that most of the derivatives exhibited comparable or superior cytotoxicity compare to CPT (1) and topotecan (TPT, 2), with 12 and 13 possessing the best efficacy. Four compounds, 9, 12, 13 and 16, were selected to be evaluated for in vivo antitumor activity against H22, BGC-823 and Bel-7402 in mice. In vivo testing results indicated that 12 and 13 had antitumor activity against mouse liver carcinoma H22 close to Paclitaxel and cyclophosphamide. 12 had similar antitumor activity against human gastric carcinoma BGC-823 in nude mice compared to irinotecan (3) and possessed better antitumor activity against human hepatocarcinoma Bel-7402 in nude mice than 2. It is also discovered that 12 showed a similar mechanism but better inhibitory activity on topoisomerase I (Topo I) compared to 2. These findings indicate that 20(S)-O-fluorouracil-1′(N)-acetic acid ester derivative of CPTs, 12, could be developed as an antitumor drug candidate for clinical trial.

Expression and characterization of bifunctional fusion proteins possessing antitumor and thrombolytic function for targeting therapy.

It is a usual clinical phenomenon that cancer patients are prone to thrombosis. Until now, there have been no efficient methods or appropriate drugs to prevent and cure tumor thrombus. ΔSEC2, N-terminal deletion of 17 amino acids and C-terminal deletion of 132 amino acids, retained antitumor activity of SEC2. ΔSak, N-terminal deletion of 10 amino acids, had thrombolytic activity and specificity advantages. By utilizing bioactivities of ΔSEC2 and ΔSak, ΔSEC2-ΔSak and ΔSak-ΔSEC2 were constructed. Octreotide is a tumor targeting peptide and it can be combined with somatostatin (SST) receptors of tumor surface in ligand-receptor binding way. It can be used to increase specificity for tumor therapy. Based on previous studies, DNA sequence encoding octreotide gene was inserted into plasmid pET-28a-Δsec2-Δsak and pET-28a-Δsak-Δsec2. After expression and purification, fusion proteins could significantly stimulate proliferation of mouse spleen lymphocyte, obviously inhibit the growth of human gastric carcinoma BGC-823, and have thrombolytic activity, indicating that fusion proteins retained bioactivities of staphylococcal enterotoxin C2 and Sak. Furthermore, tumor binding capacity of fusion protein was confirmed through the coimmunoprecipitation method. The result showed that they could bind SST receptor 2 antibody, indicating that fusion proteins could be specifically targeted to tumor surface. It has important significance and may be used for targeted therapy.

Effects of Radioactive Seeds 125 I through Interstitial Implantation on Neoplasm Invasiveness in Xenograft Nude Mice Model of Human Gastric Carcinoma BGC-823

Objective To study the inhibitory effect of radioactive seeds 125I through interstitial implantation on neoplasm invasiveness,and analyze possible mechanisms.Methods The BGC-823cells were subcutaneously injected into the right anterior armpit of BALB/C nude mice in order to establish the model of metastatic tumor.The mice of metastatic tumor were randomly divided into control group and experimental group,and mice from the experimental group were treated by interstitial implantation of 125I for 30,60and 90days,respectively.The tumor inhibitory effect was detected by measuring tumor weigh,size and lung metastasis nodules.The levels of telomerase protein in metastatic tumor,VEGF and bFGF in serum were measured by ELISA,and the expression of p-Erk1/2in tumor was analyzed by Western blot.Results Compared with the control group,tumor weight,size,lung metastasis nodules,and the levels of telomerase protein in metastatic tumor,VEGF and bFGF in serum were significantly decreased due to 125I interstitially implanted.Meanwhile,the expression of p-Erk1/2in tumor was downregulated(P0.05or P0.01),especially for 90-day treatment.Conclusion It could be the mechanism that Erk signal pathway in volved in neoplasm invasiveness is inhibited by radioactive seeds 125I through interstitial implantation in xenograft nude mice of human gastric carcinoma.

Ziyuglycoside II-induced apoptosis in human gastric carcinoma BGC-823 cells by regulating Bax/Bcl-2 expression and activating caspase-3 pathway

Ziyuglycoside II is an active compound of Sanguisorba officinalis L. that has anti-inflammation, antioxidation, antibiosis, and homeostasis properties. We report here on the anticancer effect of ziyuglycoside II on human gastric carcinoma BGC-823 cells. We investigated the effects of ziyuglycoside II on cell growth, cell cycle, and cell apoptosis of this cell line. Our results revealed that ziyuglycoside II could inhibit the proliferation of BGC-823 cells by inducing apoptosis but not cell cycle arrest, which was associated with regulation of Bax/Bcl-2 expression, and activation of the caspase-3 pathway. Our study is the first to report the antitumor potential of ziyuglycoside II in BGC-823 gastric cancer cells. Ziyuglycoside II may become a potential therapeutic agent against gastric cancer in the future.

Quantitative and Site-Directed Chemical Modification of Hypocrellins toward Direct Drug Delivery and Effective Photodynamic Activity

For photodynamic therapy (PDT) treatment of microvascular diseases, drugs are delivered via blood circulation and the targets are vasculature endothelial cells, for which the contradictory requirements of hydrophilicity and lipophilicity of the drugs have been achieved by liposome preparations. Herein, it is demonstrated that the drug delivery and target affinity are achieved by a single chemical compound, hypocrellin B (HB) derivative 6 selected from three novel aminoalkanesulfonic acid HB derivatives, 5-7. 6 exhibits a much higher PDT activity (IC(50) = 22 nM) on human gastric carcinoma BGC823 cells than HB, while it has no cellular toxicity in the dark. On the basis of estimation of the clinically required concentration according to relative PDT activity and clinical criteria, it can be predicted that 6 is directly deliverable to and PDT effective on target cells. The enhanced red absorption and superhigh photoactivity suggest that 6 is more powerful for PDT of tumors than HB.

Amplified electrochemical microRNA biosensor using a hemin-G-quadruplex complex as the sensing element

A novel signal amplified electrochemical microRNA (miRNA) biosensor was developed here using hemin-G-quadruplex as signal unit. A hairpin structure DNA probe (43 bases) was immobilized on the gold nanoparticles (AuNPs) modified gold electrode surface with the segment at its 3′-end complementary to miRNA-21 (22 bases) and the segment at its 5′-end complementary to capture DNA (21 bases). Upon hybridization with the target miRNA-21, the hairpin structure was unfolded, which was further hybridized with capture DNA loaded on AuNPs. The AuNP contained two kinds of DNA; one was complementary to the hairpin structure DNA probe, while the other was aptamer for hemin. The electrochemical signal of hemin self-assembled in the center of G-quadruplex structure of the aptamer was measured using chronoamperometry. The miRNA-21 target was analyzed with a detection limit of 3.96 pM. Using isolated total RNA from human gastric carcinoma BGC-823 cells, human breast adenocarcinoma MCF-7 cells, human hepatocarcinoma HepG2 cells and human colon cancer HT-29 cells, the assay detected specifically miRNA-21 and over-expression of oncogene miRNA-21 was demonstrated.

URD12: A urea derivative with marked antitumor activities

Urea derivatives have been widely used in biology and medicine. The substituted urea derivative URD12 introduced in this study exhibits cytotoxic activity against the K562 human leukemia and KB human mouth epidermal carcinoma cell lines. To further study the bioactivity of URD12 and examine its feasibility as a new antitumor drug, we applied in vivo and in vitro assays to investigate the antitumor activity of URD12. URD12 was prepared and its cytotoxicity was evaluated using the BGC-823 human gastric carcinoma, MGC-803 human gastric carcinoma, SMMC-7721 human hepatoma and HepG2 human hepatocellular carcinoma cell lines using MTT assays. Antitumor activity in vivo was confirmed in mice bearing H22 hepatocellular carcinoma cells. Organ coefficient was used to further elucidate the cytotoxic mechanisms of URD12. URD12 inhibited the growth of tested tumor cell lines in vitro and the growth of H22 mouse hepatocellular carcinoma in vivo with no effects on the weight, spleen and thymus coefficient of tumor-bearing mice. In conclusion, our findings indicate that URD12 is an effective antitumor agent without evident immunosuppression effects.

Highly Sensitive Fluorescent Analysis of Dynamic Glycan Expression on Living Cells Using Glyconanoparticles and Functionalized Quantum Dots

A double signal amplification strategy was designed for highly sensitive and selective in situ monitoring of carbohydrate on living cells. The double signal amplification included the multiplex sandwich binding of functionalized quantum dots (QDs) to both glycan groups on the cell surface and glyconanoparticles and a cadmium cation sensitized fluorescence emission of Rhod-5N. Using the sialic acid-phenylboronic acid recognition system as a model, the 3-aminophenylboronic acid functionalized QDs (APBA-QDs) were synthesized by covalently binding APBA to mercaptopropionic acid capped CdS QDs, and the glyconanoparticles, polysialic acid stabilized gold nanoparticles (PSA-AuNPs), were prepared by a one-pot procedure. The APBA-QDs first recognized the sialic acid (SA) groups on BGC-823 human gastric carcinoma (BGC) cells and then the PSA on AuNPs, which were further used to bind more APBA-QDs on the cell surface for signal amplification. After the bound QDs were dissolved to release the Cd(2+), a Cd(2+)-sensitized fluorescence method was developed for the detection of BGC cells in a linear range from 5.0 × 10(2) to 1.0 × 10(7) cells mL(-1) with a limit of detection down to 210 cells mL(-1) (8 cells in 40 μL of solution) and the dynamic monitoring of SA expression variation on the cell surface. The monitoring result was identical with that from flow cytometric analysis. This approach showed high specificity and acceptable reproducibility. This strategy provided a promising platform for highly sensitive cytosensing and cytobiologic study.

In Situ Electrochemical Imaging of Membrane Glycan Expression on Micropatterned Adherent Single Cells

A scanning electrochemical microscopic (SECM) method for in situ imaging of four types of membrane glycan motifs on single adherent cells was proposed using BGC-823 human gastric carcinoma (BGC) cells as the model. These adherent cells were first micropatterned in the microwell of poly(dimethylsiloxane) membrane for precisely controlling the localized surface interaction, and the membrane glycans were then specifically recognized with corresponding lectins labeled with horseradish peroxidase (HRP). On the basis of the enzymatic oxidization of ferrocenylmethanol (FMA) by H(2)O(2) to yield FMA(+), the glycan expression level was detected by the reduction current of FMA(+) at the SECM tip. The cell-surface glycans could, thus, be in situ imaged by SECM at a single-cell level without peeling the cells from culture dish. Under the optimized conditions, four types of membrane glycan motifs showed statistically distinguishable expression levels. The SECM results for different glycan motifs on adherent single cells were consistent with those estimated by flow cytometric assay. This work provides a reliable approach for in situ evaluation of the characteristic glycopattern of single living cells and can be applied in cell biologic study based on cell surface carbohydrate expression.

Proteomic identification and comparison of differentiation-related proteins in gastric carcinoma cell lines

To investigate the differentiation-related proteins in human gastric carcinoma cell lines by comparative proteomics. The holoproteins of human gastric carcinoma cell lines MKN28, SGC7901 and BGC823 were measured by two-dimensional gel electrophoresis and matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Some proteins identified by proteomics were tested by Western blot in the cell strains and tissues of gastric carcinoma. 14 differential protein spots were found in the 3 gastric carcinoma cell lines, among them 8 spots were identified by MALDI-TOF-MS. These proteins were probably thioredoxin peroxidase, glyceraldehyde-3-phosphate dehydrogenase (GAPD), beta-tubulin polypeptide, hypothetical protein, zinc finger protein (ZNF) 139, protein-tyrosine kinase, calreticulin precursor, and tropomyosin, proteins related with biological behavior of gastric carcinoma cells such as signal transduction, cellular homeostasis, glycolysis, antioxidation action, multidrug resistance(MDR), etc. The expressions of those proteins in gastric cancer cells and tissues identified by Western blot were consistent with the results obtained by proteomics. Differential proteins are found in 3 human gastric carcinoma cell lines, mainly, proteins related with cell signaling, maintenance of homeostasis, glycolysis, metabolism of anti-cancer drug and anti-oxidative injury, etc.

Oroxylin A induces G2/M phase cell-cycle arrest via inhibiting Cdk7-mediated expression of Cdc2/p34 in human gastric carcinoma BGC-823 cells

Abstract We reported previously that oroxylin A, a natural product isolated from Scutellariae Radix, was a potent apoptosis inducer of human hepatoma HepG2 cells. In this study, cell-cycle arrest of BGC-823 human gastric carcinoma cells caused by oroxylin A has been investigated. Based on our 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay and flow cytometric analysis, treatment of BGC-823 cells with growth suppressive concentrations of oroxylin A caused an irreversible arrest in the G2/M phase of the cell cycle. Western blot analysis demonstrated that oroxylin A-induced cell-cycle arrest in BGC-823 cells was associated with a significant decrease in cdc2/p34, cyclin B1 and cyclin A expression. In addition, oroxylin A-treated cells decreased the expression of Cdk7, which was responsible for the low expression of M phase promoting factor (cyclin B1/Cdc2). The results suggested that oroxylin A induced G2/M phase cell-cycle arrest via inhibiting Cdk7-mediated expression of Cdc2/p34 in human gastric carcinoma BGC-823 cells.

Over-activated Notch-1 protects gastric carcinoma BGC-823 cells from TNFα-induced apoptosis

The role of Notch-1 in human gastric carcinoma, one of the most common carcinomas of the human digestive tract, remains poorly characterised. Here, we investigated the effect and mechanism of Notch-1 activation on TNFalpha-induced apoptosis of human gastric carcinoma BGC-823 cells. Cell viabililty was measured by MTT assay. Apoptosis was detected by flow cytometry assay. Notch-1, Hes-1, caspase-3 p20 and NF-kappaB p65 expressions were assayed by Western blotting. NF-kappaB activation was tested by electrophoretic mobility shift assay (EMSA), and caspase-3 activation was tested by colorimetric assay. BGC-823 cells underwent apoptosis following stimulation with TNFalpha. We found that Notch-1 was over-activated by overexpressing exogenous intracellular domain of Notch (ICN) via retrovirus-mediated gene transfer, and over-activated Notch-1 reduced the TNFalpha-induced growth suppression and apoptosis in BGC-823 cells. Down-regulation of Notch-1 by siRNA targeting Notch-1 enhanced TNFalpha-induced apoptosis in BGC-823 cells. As the molecular mechanism involved, we showed over-activated Notch-1 partially suppressed TNFalpha-induced activation of caspase-3. However, TNFalpha-induced activation of NF-kappaB was not affected by over-activated Notch-1. Our data indicate that over-activated Notch-1 significantly protects BGC-823 cells from TNFalpha-induced apoptosis, and this effect is mediated, at least in part, by decreasing activation of caspase-3 independent of NF-kappaB.

Cytosensing and Evaluation of Cell Surface Glycoprotein Based on a Biocompatible Poly(diallydimethylammonium) Doped Poly(dimethylsiloxane) Film

In this paper, we constructed an interface that not only retains viability of immobilized BGC823 human gastric carcinoma cells (BGC823 cells) but also efficiently resists nonspecific adsorption of the P-glycoprotein antibody and its secondary antibody, which enabled us to sensitively detect the number of cells and P-glycoproteins on the BGC823 cell surface by the immunoassay method. Preparation of the film was quite simple and inexpensive just by spin-coating poly(dimethylsiloxane) (PDMS) doped with poly(diallydimethylammonium) (PDDA) on the surface of gold electrodes. The composite film's biocompatibility, antinonspecific adsorption ability, and the conductivity for electrochemical probe ([Fe(CN)6]3-/4-) were proved by cell culture experiments, blocking experiments, and electrochemical experiments. Compared with PDMS and PDMS doped with poly(sodium 4-styrenesulfonate) (PSS), the PDMS-PDDA composite film showed a predominant ability to capture cells due to electrostatic reaction between the presence of positively charged PDDA and the negatively charged glycocalyx on the surface of cells. On the advantage of electrochemical immunoassay with a signal amplification path by using biocatalytic precipitation of an insoluble product, differential pulse voltammetry (DPV) measurement based on the changes of electron-transfer resistance was introduced to detect the cell amount and monitor growing states of cells like adhesion, spread, proliferation, and apoptosis on the electrodes. Optimally, signal response was proportional to the logarithm of cell concentration ranging from 1.0 x 10(3) to 5.0 x 10(7) cells mL(-1) with a detection limit of 7.2 x 10(2) cells mL(-1). On the basis of the special property for resisting nonspecific adsorption of this composite film, an ultraviolet and visible (UV-vis) absorption spectrum with one-step immunoreaction was employed to evaluate the P-glycoprotein on the BGC823 cell surface. The P-glycoprotein on a single living intact BGC823 cell was detected correspondingly to 4.7 x 10(7) molecules. The work implied that the composite film possessed potential applications for biosensing and convenient evaluation of surface glycoprotein on living cells.

Synergistic effect of 5-fluorouracil with gambogic acid on BGC-823 human gastric carcinoma

The design of novel targeted or combination therapies may improve treatment options for gastric cancer. In this study, we determined the inhibitory effects of 5-fluorouracil (5-FU) combined with gambogic acid (GA) on BGC-823 human gastric carcinoma cells in vitro and in vivo and investigated the underlying mechanisms. 5-FU combined with GA inhibited the viability of BGC-823 human gastric cells in a concentration-dependent manner. The pro-apoptotic activity of the two-drug combination was much stronger than single. Furthermore, the results showed GA could regulate the metabolic enzymes of 5-FU. GA decreased the mRNA levels of thymidine synthetase (TS) and dihydropyrimidine dehydrogenase (DPD), while increased the mRNA level of orotate phosphoribosyltransferase (OPRT). Moreover, combined treatment caused significantly growth inhibition of human tumor xenografts in vivo. Taken together, our data showed that GA attenuated 5-FU-induced apoptosis by modulating metabolic enzymes of 5-FU and the antigastric cancer effect of two drugs combination was much stronger than that of GA or 5-FU alone.

Oroxylin A induces G<SUB>2</SUB>/M phase cell-cycle arrest via inhibiting Cdk7-mediated expression of Cdc2/p34 in human gastric carcinoma BGC-823 cells

We reported previously that oroxylin A, a natural product isolated from Scutellariae Radix, was a potent apoptosis inducer of human hepatoma HepG2 cells. In this study, cell-cycle arrest of BGC-823 human gastric carcinoma cells caused by oroxylin A has been investigated. Based on our 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay and flow cytometric analysis, treatment of BGC-823 cells with growth suppressive concentrations of oroxylin A caused an irreversible arrest in the G2/M phase of the cell cycle. Western blot analysis demonstrated that oroxylin A-induced cell-cycle arrest in BGC-823 cells was associated with a significant decrease in cdc2/p34, cyclin B1 and cyclin A expression. In addition, oroxylin A-treated cells decreased the expression of Cdk7, which was responsible for the low expression of M phase promoting factor (cyclin B1/Cdc2). The results suggested that oroxylin A induced G2/M phase cell-cycle arrest via inhibiting Cdk7-mediated expression of Cdc2/p34 in human gastric carcinoma BGC-823 cells.

Effects of Newcastle disease virus on the mitochondria of human gastric carcinoma BGC-823 cells

To explore changes in structure and function of the mitochondria of human gastric carcinoma BGC-823 cells after Newcastle disease virus (NDV) infection. Electron microscopy was applied to observe the structure of mitochondria; Rhodamine 123 staining was used to determine the mitochondrial membrane potential; the activity of Na(+)-K(+)-ATPase and Ca(2+)-ATPase were also determined and the release of cytochrome C was detected by Western blotting. The structure of mitochondria in the tumor cells infected with NDV changed distinctly. In the infected group the activity of mitochondrial Na(+)-K(+)-ATPase and Ca(2+)-ATPase significantly declined (P < 0.01), and compared with control cells, mitochondrial trans-membrane potential was decreased. NDV infection induced the decrease of cytochrome C levels. The effects of NDV infection on the structure and functions of mitochondria of human gastric carcinoma BGC-823 cells might play a role in the oncolysis of NDV.

Effective Cell Capture with Tetrapeptide-Functionalized Carbon Nanotubes and Dual Signal Amplification for Cytosensing and Evaluation of Cell Surface Carbohydrate

A novel electrochemical cytosensing strategy was designed based on the specific recognition of integrin receptors on a cell surface to arginine-glycine-aspartic acid-serine (RGDS)-functionalized single-walled carbon nanotubes (SWNTs). The covalent conjugation of the RGDS tetrapeptide to SWNTs was proved with Raman and FT-IR spectra. The conjugated RGDS showed a predominant ability to capture cells on the electrode surface by the specific combination of RGD domains with integrin receptors. With the use of BGC-823 human gastric carcinoma cells (BGC cells) as a model, the cell surface mannosyl groups could specifically bind with horseradish peroxidase labeled concanavalin A, producing an electrochemical cytosensor. On the basis of the dual signal amplification of SWNTs and enzymatic catalysis, the cytosensor could respond down to 620 cells mL (-1) of BGC cells with a linear calibration range from 1.0 x 10 (3) to 1.0 x 10 (7) cells mL (-1), showing very high sensitivity. The dual signal amplification could be further used to evaluate the mannosyl groups on the cell surface, and the mannosyl groups on a single living intact BGC cell were detected to correspond to 5.3 x 10 (7) molecules of mannose. This strategy presents a promising platform for highly sensitive cytosensing and convenient evaluation of surface carbohydrates on living cells.