Biomedical subjects

Li-Qun Wu

Publications and source records attributed to Li-Qun Wu.

17 recordsLinked to original sources

PubMed2007

Reversible vesicle restraint in response to spatiotemporally controlled electrical signals: a bridge between electrical and chemical signaling modes.

Microelectronic devices employ electrons for signaling whereas the nervous system signals using ions and chemicals. Bridging these signaling differences would benefit applications that range from biosensing to neuroprosthetics. Here, we report the use of localized electrical signals to perform an operation common to chemical signaling in the nervous system. Specifically, we employ electrical signals to restrain vesicles reversibly. We perform this operation using the stimuli-responsive aminopolysaccharide chitosan that is able to electrodeposit onto cathode surfaces in response to localized electrical stimuli. We show that surfactant-vesicles and liposomes can be co-deposited with chitosan and are entrapped (i.e., restrained) within the deposited film's matrix. Vesicle co-deposition could be controlled spatially and temporally using microfabricated wafers with independent electrode addresses. Finally, we show that vesicles restrained within the deposited chitosan matrix can be mobilized under mildly acidic conditions (pH <6.5) that resolubilize chitosan. Potentially, the ability to restrain and mobilize chemical signals that are segregated within vesicles may allow microfluidic systems to access the rich diversity offered by chemical signaling.

Animals↗

PubMed2006

Mechano-transduction of DNA hybridization and dopamine oxidation through electrodeposited chitosan network.

While microcantilevers offer exciting opportunities for mechano-detection, they often suffer from limitations in either sensitivity or selectivity. To address these limitations, we electrodeposited a chitosan film onto a cantilever surface and mechano-transduced detection events through the chitosan network. Our first demonstration was the detection of nucleic acid hybridization. In this instance, we electrodeposited the chitosan film onto the cantilever, biofunctionalized the film with oligonucleotide probe, and detected target DNA hybridization by cantilever bending in solution (static mode) or resonant frequency shifts in air (dynamic mode). In both detection modes, we observed a two-order of magnitude increase in sensitivity compared to values reported in literature for DNA immobilized on self-assembled monolayers. In our second demonstration, we coupled electrochemical and mechanical modes to selectively detect the neurotransmitter dopamine. A chitosan-coated cantilever was biased to electrochemically oxidize dopamine solution. Dopamine's oxidation products react with the chitosan film and create a tensile stress of approximately 1.7 MPa, causing substantial cantilever bending. A control experiment was performed with ascorbic acid solution. It was shown that the electrochemical oxidation of ascorbic acid does not lead to reactions with chitosan and does not change cantilever bending. These results suggest that chitosan can confer increased sensitivity and selectivity to microcantilever sensors.

Biosensing Techniques↗

PubMed2006

Expression of cancer-testis antigen (CTA) in tumor tissues and peripheral blood of Chinese patients with hepatocellular carcinoma.

To investigate the expression of cancer-testis antigen (CTA) in Chinese patients with hepatocellular carcinoma (HCC), and the relationship between CTA gene expression and clinical indexes, we used one-step reverse transcription polymerase chain reaction (RT-PCR). The expression of the CTA mRNA was investigated in the tissues of HCC and corresponding peripheral blood of 37 patients with HCC. Fifteen samples of cirrhotic tissues and 15 normal tissues were examined with the same method. Two kinds of CTA (SSX-2 and SSX-5) showed high-specific and high-frequent expression in HCC tissues, but neither of them could be detected in adjacent non-HCC tissues. In corresponding peripheral blood of HCC tissues, the positive expression rate of the SSX-2 and SSX-5 mRNA was not very high. No relationship was found between the expression of CTA and clinical indicators such as age, sex, tumor size, TNM staging, serum AFP level and infection with hepatitis virus. In 15 patients with cirrhosis and 15 other non-tumor patients, none of the SSX-2 and SSX-5 mRNA was detected in liver tissue or peripheral blood. High frequency and specificity of CTAs in HCC indicates that their products may be new potential promising targets for antigen-specific immunotherapy of HCC. High frequent co-expression of the two genes in HCC provides a possibility of polyvalent vaccinations for HCC. Specific expression of CTAs was observed in AFP-negative HCC, suggested applying their mRNA as tumor markers to detect circulating HCC cells as adjuvant diagnostic tool and as indicators of recurrence and prognosis.

Adolescent↗

PubMed2006

[Effect of disc displacement on mRNA expression of urokinase plasminogen activator and its inhibitor-1 in synovial tissues].

OBJECTIVE: To investigate the effect of anterior disc displacement on the expression of urokinase plasminogen activator and its inhibitor-1 (uPA/PAI-1) in synovial tissues. METHODS: Forty Japanese white rabbits were used in this study. The animals were killed at 4 days, 1, 2, 4, 8 and 12 weeks postoperatively, respectively. In situ hybridization technology was applied to detect the expression of uPA/PAI-1 mRNA in synovial membrane. RESULTS: In normal synovial tissues, synovial lining cells and a few fibrosblasts with mild positive staining were occasionally seen. More synovial lining cells and fibrosblasts with moderate postive signals were found 1 week after operation. Since then, the degree of staining for uPA/PAI-1 increased gradually. By the end of 12 weeks postoperatively, strong signals of uPA/PAI-1 mRNA were detected. CONCLUSION: There is a harmonized uPA/PAI-1 system existing in synovial tissues. The high expression of uPA and PAI-1 mRNA in synovial tissues indicates that the uPA/PAI-1 system may play an important role in the process of synovitis resulted from anterior disc displacement.

Animals↗

PubMed2005

Chitosan-mediated and spatially selective electrodeposition of nanoscale particles.

Nanoscale particles offer a variety of interesting properties, and there is growing interest in their assembly into higher ordered structures. We report that the pH-responsive aminopolysaccharide chitosan can mediate the electrodeposition of model nanoparticles. Chitosan is known to electrodeposit at the cathode surface in response to a high localized pH. To demonstrate that chitosan can mediate nanoparticle deposition, we suspended fluorescently labeled latex nanoparticles (100 nm diameter spheres) in a chitosan solution (1%) and performed electrodeposition (0.05 mA/cm2 for several minutes). Results demonstrate that chitosan is required for nanoparticle electrodeposition; chitosan confers spatial selectivity to electrodeposition; and nanoparticles distribute throughout the electrodeposited chitosan film. Additionally, we observed that the deposited films reversibly swell upon rehydration. This work indicates that chitosan provides a simple means to assemble nanoparticles at addressable locations and provides further evidence that stimuli-responsive biological materials may facilitate fabrication at the microscale.

Biocompatible Materials↗

PubMed2005

Signal-directed sequential assembly of biomolecules on patterned surfaces.

The signal-guided and sequential assembly of biomolecules onto patterned surfaces is demonstrated. Readily transmittable electric signals are used to guide spatially selective deposition of the pH-responsive polysaccharide, chitosan, and functionalized chitosan conjugates, by generating localized pH gradients. The nucleophilic primary amine groups of chitosan enable facile conjugation of proteins and nucleic acids by two approaches, one an enzymatic approach and the other a standard chemical modification, thus providing flexibility when sequentially assembling biomolecules in a spatially selective manner. Moreover, we developed an agarose gel "biomask" for the sequential assembly of single-stranded DNA and confirmed its functionality through nucleic acid hybridization assays.

Base Sequence↗

PubMed2004

Thermo-biolithography: a technique for patterning nucleic acids and proteins.

We describe a "biolithographic" technique in which the unique properties of biopolymeric materials and the selective catalytic activities of enzymes are exploited for patterning surfaces under simple and bio-friendly conditions. We begin by coating a reactive film of the polysaccharide chitosan onto an inorganic surface (glass or silicon wafer). Chitosan's pH-responsive solubility facilitates film deposition, while the nucleophilic properties of this polysaccharide allow simple chemistries or biochemistries to be used to covalently attach species to the film. The thermally responsive protein gelatin is then cast on top of the chitosan film, and the gelatin gel serves as a sacrificial "thermoresist". Pattern transfer is accomplished by applying a heated stamp to melt specific regions of the gelatin thermoresist and selectively expose the underlying chitosan. Finally, molecules are conjugated to the exposed chitosan sublayer and the sacrificial gelatin layer is removed (either by treating with warm water or protease). To demonstrate the concept, we patterned a reactive dye (NHS-fluorescein), a model 20-base oligonucleotide (using standard glutaraldehyde coupling chemistries), and a model green fluorescent protein (using tyrosinase-initiated conjugation). Because gelatin can be applied and removed under mild conditions, sequential thermo-biolithographic steps can be performed without destroying previously patterned biomacromolecules. These studies represent the first step toward exploiting nature's exquisite specificity for lithographic patterning.

Biosensing Techniques↗

PubMed2004

A robust technique for assembly of nucleic acid hybridization chips based on electrochemically templated chitosan.

A nucleic acid hybridization assay was assembled onto a robust and readily addressable silicon-based chip using polysaccharide chitosan as a scaffold for the covalent coupling of probe DNA to the chip's surface. Chitosan is a unique polymer, ideally suited for this application because its net charge and solubility are pH dependent. Specifically in this work, gold-patterned electrodes were created using standard photolithographic techniques, chitosan was electrodeposited in a spatially resolved manner onto the polarized electrodes, probe DNA was covalently assembled onto the chitosan, and both DNA:DNA and DNA:mRNA hybridization detection schemes were evaluated. Hybridization of target nucleic acid was quantifiable, reproducible, and robust; the surface was regenerated and rehybridized up to eight times without loss of signal. Finally, transcriptional upregulation of the Escherichia coli chaperone, DnaK, which is an indicator of cellular stress, was observed using the hybridization chip sandwich assay. Thus, this method enables rapid and facile monitoring of gene expression in a format that is reusable and requires minimal reagent quantities.

Chitin↗

PubMed2004

Biofabrication: using biological materials and biocatalysts to construct nanostructured assemblies.

Emerging opportunities are placing greater demands on device fabrication: next-generation microelectronics will need minimum features of less than 100 nm, high-throughput drug screening will require facile methods to incorporate sensitive biological components into microelectromechanical systems (MEMS), and implantable devices will need to be built from biocompatible materials. Increasingly, these emerging demands are being addressed by combining traditional microfabrication methods with 'biofabrication': namely, the use of biologically derived materials and biocatalysts. Recent fabrication techniques are using biological construction materials as process aids or structural components, and enzymes are being considered for their potential to fabricate devices with high selectivity under mild conditions. If incompatibilities between biology and microfabrication can be eliminated, then biofabrication will be poised to emerge as the standard for nanoscale construction.

Animals↗

PubMed2004

Expression of the bacterial gene in gallbladder carcinoma tissue and bile.

BACKGROUND: The major causive factors of gallbladder carcinoma are very complex. Cholecystitis with gallstone was reported one of the most important factors. Many research revealed that cholecystitis or gallstone can give rise to epithelial hyperplasia of gallbladder mucusa or canceration secondarily. In this study, 46 patients were detected in order to find the relationship between infection of different bacteria and formation of gallbladder carcinoma. METHODS: Using the common gene primer of bacteria 16S ribosomal RNA (rRNA), we detected bacterial gene fragments of gallbladder carcinoma tissues in 46 patients by polymerase chain reaction (PCR). Relative bile was also detected by PCR in 18 patients who underwent operations, including U-tube drainage (1), right or left biliary tube drainage (4), radical cholecystectomy (9), and cholecystorrhaphy (4). The tissue fragments of gallbladder carcinoma from the remaining 28 patients were paraffin slices. RESULTS: The positive rate of bacterial DNA in gallbladder carcinoma tissue was 78.3% (36/46). The sequence of 16S ribosomal RNA gene fragments amplified by PCR was approximately 371 base pairs (bp). Multiple kinds of standard bacterial gene fragments obtained from 36 patients included Colibacillus, B.fragilis, Klebsiella, C.perfringens and Clostridium, with a positive rate of 78.3% (36/46). Among the 36 patients, 14 patients with gallbladder carcinoma received operation and their relative bile at operation was detected bacterial gene fragments with a positive rate of 77.8% (14/18). This result was close to that in gallbladder carcinoma tissues. CONCLUSIONS: Our results suggested that there might be a relationship between occurrence of gallbladder carcinoma and infection of different kinds of bacteria, especially anaerobic bacteria C.perfringens. This reminds us that the gallbladder mucosa stimulated by anaerobic and aerobic bacteria might be the principal cause for the development of carcinoma.

Adolescent↗

PubMed2004

Efficacy of intra-tumor injection of Kang-Lai-Te in treating transplanted hepatoma in rats.

BACKGROUND: Non-operative therapy takes an important position in comprehensive therapy of liver cancer. Despite some effects by using ethanol, acetic acid and heat saline for intra-tumor injection in the treatment of liver cancer, it is difficult to attain a complete cure but bring about injury to the liver to some extent. Hence, searching for other drugs for the local treatment of liver tumor is an important option. This study was designed to set up rat models of transplanted liver cancer, intra-tumor injection of Kang-Lai-Te (KLT), and negative control (saline) and positive control (ethanol). The effect of intra-tumor injection of KLT in treating transplanted hepatoma in rats and its advantages and disadvantages were assessed and the possibility of its use in treating patients with liver cancer was evaluated. METHODS: Forty rats were divided into 4 groups (G1, G2, G3 and G4, 10 rats in each group). Different drugs were injected into their implanted hepatoma (G1 with 0.2 ml saline as control, G2 with 10 mg KLT, G3 with 20 mg KLT, G4 with 0.2 ml ethanol). After 3 and 8 days, the hepatoma volume (HV), the serum levels of albumin, alanine aminotransferase(ALT), aspartate aminotransferase alkaline phosphatase(ALP) and creatinine, as well as the expression of proliferation cell nuclear antigen(PCNA) in hepatoma were detected. RESULTS: After 3 days, the HVs were smaller in G3 and G4 than in G1 (P<0.05), the serum levels of albumin were higher in G2 and G3 than in G1 and G4 (P<0.05), the serum levels of ALT and AST were lower in G2 and G3 than in G4 (P<0.05), the serum levels of ALP was lower in G2 and G3 than in G1 and G4 (P<0.05),the PCNA labeling indexes (PCNA LI) were lower in G2 and G3 than in G1 and G4 (P<0.05). After 8 days, the HVs were smaller in G2, G3 and G4 than in G1 (P<0.05), and the differences of HVs among G2, G3 and G4 were not significant. The serum levels of ALP were lower in G1, G2 and G3 than in G4 (P<0.05), and the PCNA LI were lower in G3 than in G1 and G4 (P<0.05). CONCLUSION: Intra-tumor injection of KLT into implanted hepatoma is evidently effective, but it is less effective than ethanol. The effect of KLT on liver function is markedly lower than that of ethanol.

Animals↗

PubMed2003

Chitosan scaffolds for biomolecular assembly: coupling nucleic acid probes for detecting hybridization.

Chitosan, a naturally occurring biopolymer, was used as a scaffold for the covalent binding of single-stranded DNA oligonucleotide probes in a fluorescence-based nucleic acid hybridization assay. Chitosan's pH dependent chemical and electrostatic properties enable its deposition on electrodes and metal surfaces, as well as on the bottom of microtiter plates. A combinatorial 96-well microtiter plate format was used to optimize chemistries and reaction conditions leading to hybridization experiments. We found the coupling of oligonucleotides using relatively common glutaraldehyde chemistry was quite robust. Our hybridization results for complementary ssDNA oligonucleotides (E. coli dnaK sequences) demonstrated linear fluorescence intensity with concentration of E. coli dnaK-specific oligonucleotide from 0.73 microM to 6.6 microM. Moreover, hybridization assays were specific as there was minimal fluorescence associated with noncomplementary groEL oligonucleotide. Finally, these results demonstrate the portability of a DNA hybridization assay based on covalent coupling to chitosan, which, in turn, can be deposited onto various surfaces. More arduous surface preparation techniques involving silanizing agents and hazardous washing reagents are eliminated using this technique.

Chitin↗

PubMed2003

Efficacy of intra-tumor injection of Xiao-Zhi-Ling on transplanted hepatoma in rats.

AIM: To study the therapeutic effectiveness of intra-tumor injection of Xiao-Zhi-Ling(XZL) on transplanted hepatoma in rats. METHODS: Sixty rats were divided into 3 groups (groups S, X and E), 20 in each. Different drugs were injected into the implanted hepatoma (Group S with 0.2 ml saline as control, group X with 0.2 ml XZL, group E with 0.2 ml ethanol). After 3 days and 8 days respectively, we detected the hepatoma volume (HV), the level of albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) in serum, and the expression of proliferating cell nuclear antigen (PCNA) in hepatoma. RESULTS: The results were obtained after 3 days, the HVs in groups X and E were smaller than those in group S (group X vs S P=0.010(*), group E vs S P=0.002(*), P<0.05). The levels of ALT and AST in group S and X were lower than those in group E (ALT Group S vs E P=0.019(*), group X vs E P=0.003(*), P<0.05; AST group X vs E P=0.002(*), P<0.05). The levels of ALP and PCNA labeling index in group X were lower than those in group S and E (ALP group X vs S P=0.000(*), group X vs E P=0.000(*). P<0.05; PCNA group X vs S P=0.008(*), group X vs E P=0.048(*), P<0.05). The levels of creatinine in group S were lower than those in group E (group S vs E P=0.017, P<0.05). The degree of tumor necrosis in group S was lower than those in groups X and E (group S vs X P=0.006(*), group S vs E P=0.006(*), P<0.05). After 8 days, the HVs in groups X and E were smaller than those in group S (group X vs S P=0.007(*), group E vs S P=0.004(*), P<0.05). The difference of HVs between groups X and E was not significant. The levels of albumin, ALT, AST and creatinine in group X were not higher than those in other groups, the levels of ALP and PCNA in group X were lower than those in groups S and E (ALP group X vs E P=0.006(*) P<0.05; PCNA group X vs S P=0.044(*), group X vs E P=0.021(*), P<0.05). The degree of tumor necrosis in group S was lower than that in groups X and E (group S vs X P=0.001(*), group S vs E P=0.002(*), P<0.05). CONCLUSION: The therapeutic effectiveness of intra-tumor injection of XZL and ethanol on implanted hepatoma is obvious, but the toxicity of XZL on liver function is markedly lower than that of group E, at the same time XZL can inhibit the growth of tumor. XZL is relatively better and safer than ethanol in intra-tumor injection therapy.

Alum Compounds↗

PubMed2003

Treatment of early duodenal fistula after orthotopic liver transplantation: a case report.

Gastrointestinal fistula as a serious complication could lead to imbalance of nutrition or death. Duodenal fistula after orthotopic liver transplantation is rare and its treatment is complicated. On April 28, 200, we performed orthotopic liver transplantation for a patient at our hospital. Eight days after operation duodenal fistula developed, but cured after 13-day treatment.

Debridement↗

PubMed2002

Utilizing renewable resources to create functional polymers: chitosan-based associative thickener.

There is a growing interest in utilizing renewable resources and exploiting biological reactions for environmentally friendly products and processes. We report the use of the enzyme tyrosinase to graft the natural phenol, catechin, onto the biopolymer chitosan. Chemical evidence for grafting was obtained by UV/visible spectrophotometry and electrospray mass spectrometry. Rheological measurements demonstrate that the catechin-modified chitosan behaves as an associative thickener. Specifically, the viscosity increases dramatically with concentration of this modified chitosan. Furthermore, when the catechin-modified chitosan is dissolved at low concentrations (0.6% w/w), steady shear measurements show shear thinning behavior, while oscillatory measurements show weak gel behavior. These results demonstrate the potential for utilizing renewable resources and biochemical processing to functionalize biopolymersto offertechnically useful properties. To suggest the relative environmental impacts of chitosan derivatives with existing water-soluble polymers, we used the framework of a life cycle assessment.

Biocompatible Materials↗

PubMed2002

In vitro protein-polysaccharide conjugation: tyrosinase-catalyzed conjugation of gelatin and chitosan.

The enzyme tyrosinase was used for the in vitro conjugation of the protein gelatin to the polysaccharide chitosan. Tyrosinases are oxidative enzymes that convert accessible tyrosine residues of proteins into reactive o-quinone moieties. Spectrophotometric and dissolved oxygen studies indicate that tyrosinase can oxidize gelatin and we estimate that 1 in 5 gelatin chains undergo reaction. Oxidized tyrosyl residues (i.e., quinone residues) can undergo nonenzymatic reactions with available nucleophiles such as the nucleophilic amino groups of chitosan. Ultraviolet/visible, (1)H-NMR, and ir provided chemical evidence for the conjugation of oxidized gelatin with chitosan. Physical evidence for conjugation was provided by dynamic viscometry, which indicated that tyrosinase catalyzes the sol-to-gel conversion of gelatin/chitosan mixtures. The gels formed from tyrosinase-catalyzed reactions were observed to differ from gels formed by cooling gelatin. In contrast to gelatin gels, tyrosinase-generated gels had different thermal behavior and were broken by the chitosan-hydrolyzing enzyme chitosanase. These results demonstrate that tyrosinase can be exploited for the in vitro formation of protein-polysaccharide conjugates that offer interesting mechanical properties.

Agaricales↗

PubMedDate not supplied

Biofabrication with chitosan.

The traditional motivation for integrating biological components into microfabricated devices has been to create biosensors that meld the molecular recognition capabilities of biology with the signal processing capabilities of electronic devices. However, a different motivation is emerging; biological components are being explored to radically change how fabrication is achieved at the micro- and nanoscales. Here we review biofabrication, the use of biological materials for fabrication, and focus on three specific biofabrication approaches: directed assembly, where localized external stimuli are employed to guide assembly; enzymatic assembly, where selective biocatalysts are enlisted to build macromolecular structure; and self-assembly, where information internal to the biological material guides its own assembly. Also reviewed are recent results with the aminopolysaccharide chitosan, a material that offers a combination of properties uniquely suited for biofabrication. In particular, chitosan can be directed to assemble in response to locally applied electrical signals, and the chitosan backbone provides sites that can be employed for the assembly of proteins, nucleic acids, and virus particles.

Animals↗