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Biomedical subjects

Kemin Wang

Publications and source records attributed to Kemin Wang.

At least 19 recordsLinked to original sources
PubMed2006

Atomic force microscopy study of different effects of natural and semisynthetic beta-lactam on the cell envelope of Escherichia coli.

The effects of native and semisynthetic beta-lactam on the surface of E. coli cells were investigated using tapping mode atomic force microscopy (AFM). These studies were done on both single cell and cell colonies. This allowed us to achieve a complete understanding of the effects, since previous related AFM analysis was only performed on single cells. Our results indicated that although amoxycillin and penicillin could both induce nanoporous damage to the envelope of E. coli, the distribution of the pores was different: those induced by penicillin were randomly distributed on the cell surface, while those induced by amoxycillin were far more numerous and mainly on the two ends of the cell. These findings could explain why the effect of amoxycillin is stronger than that of native penicillin. Ofloxacin was used as a control due to its inactive membrane, and no cell wall damages were observed. Our results demonstrate that AFM is a useful tool in discerning and verifying antibiotic mechanisms and can be helpful to explain the relationship between chemical structure and the function of antibiotics.

Anti-Bacterial Agents↗
PubMed2006

Magnetically assisted and accelerated self-assembly of strawberry-like nano/microparticles.

Precisely controlling multiple components of functional materials with well-defined shapes and dimensions on the micro/nanometer scale promises to provide new electronic, magnetic, mechanical, and optical properties for novel sensors, circuits, and other materials application. Here for the first time we introduce a novel method to reliably pattern strawberry-like microspheres by employing magnetically directed and accelerated self-assembly of nano/microparticles in aqueous solution, without the use of a template (such as molds or grooves). The results show that 100-1000 nm paramagnetic "decorating particles" rapidly self-assembled onto the surface of fluorescent 4-5 mum spherical magnetized "core particles", producing strawberry-like particles with stable and precisely arranged microstructures. Magnetic CrO2 nanorods, approximately 60 nm in diameter and 300 nm long, attached to the nonplanar surface of the 4-5 microm polystyrene core microspheres, serve as nanometer magnetic traps, so as to attract and confine paramagnetic decorating particles. The ease and speed, with which these particles can be fabricated with the aid of magnetic force, and the flexibility to tailor their chemical and physical properties through the choice of decorating particles, should facilitate their use for practical application in materials science, biology, and technology.

Algorithms↗
PubMed2006

Quantitative intracellular molecular profiling using a one-dimensional flow system.

We report on the development of one-dimensional microfluidic bead arrays for rapid and quantitative molecular profiling of human cancer cells. This new bioanalytical platform integrates the rapid binding kinetics of suspension bead carriers, the multiplexing and encoding capabilities of gene/protein chips, and the liquid handling advantages of microfluidic devices. Using antibody-conjugated beads in a two-site "sandwich" format, we demonstrate that the proteomic contents of as few as 56 human lung epithelial cancer cells can be determined with high sensitivity and specificity. The results indicate that each cell contains approximately 6 x 10(5) copies of the tumor suppressor protein P53. We have further examined the expression changes of P53, c-Myc, and beta-Actin as a function of anticancer drug treatment and have validated these changes by using Western blotting. This ability to quantitatively analyze normal and diseased cells raises new possibilities in studying cancer heterogeneity and circulating tumor cells.

Animals↗
PubMed2006

Electrical switching of DNA monolayers investigated by surface plasmon resonance.

The switching of DNA monolayers between a "lying" and a "standing" state initiated by applying electric field, and the subsequent DNA hybridization at different states were investigated in a contactless, label-free mode by surface plasmon resonance (SPR) technique. The results showed that the strength of the electric field and surface coverage could influence the switching of DNA monolayers. In addition, it was found that DNA hybridization efficiency could be enhanced or decreased when DNA probes stood straight up or lay flat on the gold surface, depending on the potential of the gold substrate. The enhancement of DNA hybridization efficiency reached the maximum when surface coverage reached 5.87 x 10(12) molecules/cm(2) and the potential of gold substrate was more negative than -0.7 V (versus ITO-coated glass). The research may be helpful for the construction of sensitive biosensors, biochips, and nanoscale electronic devices.

Base Sequence↗
PubMed2006

Enhanced surface plasmon resonance with the modified catalytic growth of Au nanoparticles.

The catalytic growth of Au nanoparticles (AuNPs) has been employed in several analytical methods for improving the detection sensitivity, or integrated with the enzyme reactions for the quantitative detection of the respective substrates. However, the catalytic growth of Au nanoparticles do not work in some situations, such as surface plasmon resonance (SPR), electrochemistry, where metal matrices were used, because metal matrices used in these techniques, e.g. Au, are susceptible to metal deposition, which increased the background seriously. In this work, a SiO(2) layer was vapor-deposited on the gold film. The inhibition of metal deposition by this SiO(2) layer was investigated by SPR sensor. The results showed that the SiO(2) layer could avoid the deposition of metal on Au film. With the low background achieved by SiO(2)-coated Au films, sensitive detection of DNA hybridization using the catalytic growth of Au nanoparticles enhanced SPR was demonstrated. The work described here maybe helpful for the development of sensitive bioanalytical methods.

Catalysis↗
PubMed2006

Immunofluorescent labeling of cancer cells with quantum dots synthesized in aqueous solution.

Thioglycolic-acid-stabilized CdTe quantum dots, synthesized directly in aqueous solution, are successfully conjugated with biotin and polyethylene glycol. Using these conjugates, we report the development of this kind of water-soluble quantum dot for immunofluorescent labeling of cancer cells. The results show that these conjugates have very low nonspecific binding and good stability against photobleaching, enabling them to be applied in many biological fields, such as cellular labeling, intracellular tracking, and other imaging applications.

Cell Line, Tumor↗
PubMed2005

Real-time investigation of nucleic acids phosphorylation process using molecular beacons.

Phosphorylation of nucleic acids is an indispensable process to repair strand interruption of nucleic acids. We have studied the process of phosphorylation using molecular beacon (MB) DNA probes in real-time and with high selectivity. The MB employed in this method is devised to sense the product of a 'phosphorylation-ligation' coupled enzyme reaction. Compared with the current assays, this novel method is convenient, fast, selective, highly sensitive and capable of real-time monitoring in a homogenous solution. The preference of T4 polynucleotide kinase (T4 PNK) has been investigated using this approach. The results revealed that a single-stranded oligonucleotide containing guanine at the 5' termini is most preferred, while those utilizing cytosine in this location are least preferred. The preference of (T)9 was reduced greatly when phosphoryl was modified at the 5' end, implying that T4 PNK could discern the phosphorylated/unphosphorylated oligonucleotides. The increase of oligonucleotide DNA length leads to an enhancement in preference. A fast and accurate method for assaying the kinase activity of T4 PNK has been developed with a wide linear detection range from 0.002 to 4.0 U/ml in 3 min. The effects of certain factors, such as NTP, ADP, (NH4)2SO4 and Na2HPO4, on phosphorylation have been investigated. This novel approach enables us to investigate the interactions between proteins and nucleic acids in a homogenous solution, such as those found in DNA repair or in drug development.

Bacteriophage T4↗
PubMed2005

Molecular beacons for bioanalytical applications.

Molecular beacons (MBs) are hairpin-shaped oligonucleotides that contain both fluorophore and quencher moieties. They act like switches and are normally in a closed state, when the fluorophore and the quencher are brought together to turn "off" the fluorescence. When prompted to undergo conformational changes that open the hairpin structure, the fluorophore and the quencher are separated, and fluorescence is turned "on." This Education will outline the principles of MBs and discuss recent bioanalytical applications of these probes for in vitro RNA and DNA monitoring, biosensors and biochips, real-time monitoring of genes and gene expression in living systems, as well as the next generation of MBs for studies on proteins, the MB aptamers. These important applications have shown that MBs hold great potential in genomics and proteomics where real-time molecular recognition with high sensitivity and excellent specificity is critical.

Biosensing Techniques↗
PubMed2005

Using molecular beacon to monitor activity of E. coli DNA ligase.

NAD(+)-dependent DNA ligase has been widely used in gene diagnostics for disease-associated mutation detection and has proved to be necessary for screening bactericidal drugs targeted to DNA ligases. However, further research has been restricted since conventional ligase assay technology is limited to gel electrophoresis, which is discontinuous, time-consuming and laborious. An innovative approach is developed for monitoring the activity of E. coli DNA ligase catalyzing nucleic acid ligation in the report. This approach utilizes a molecular beacon hybridized with two single-stranded DNA (ssDNA) segments to be ligated to form a hybrid with a nick, and could therefore be recognized by the enzyme. Ligation of the two ssDNA segments would cause conformation changes of the molecular beacon, leading to significant fluorescence enhancement. Compared to gel electrophoresis, this approach can provide real time information about ligase, is more time efficient, and is easier to use. The effect of quinacrine, a drug for malaria, on the activity of the ligase is detected, thereby certifying the capability of the method for developing novel antibacterial drugs targeted at NAD(+)-dependent ligase. The fidelity of strand joining by the ligase is examined based on this approach. The effects of external factors on activity of the ligase are analyzed, and then an assay of E. coli DNA ligase is performed with a broad linear range of 4.0 x 10(-4) Weiss Unit mL(-1) to 0.4 Weiss Unit mL(-1) and the detection limit of 4.0 x 10(-4) Weiss Unit mL(-1).

DNA Ligase ATP↗
PubMed2005

Influence of anions on the formation and properties of chitosan-DNA nanoparticles.

Chitosan-DNA nanoparticles were prepared by using different anions (such as chloride, sulfate, citrate, and tripolyphosphate) as mediation agents. The research suggested that the formation and morphological characteristics of chitosan-DNA nanoparticles largely depended on concentration, molecular size, charge number, and chemical structure of anions, as well as chitosan/DNA ratio. The observation by atom force microscopy showed that chitosan-DNA nanoparticles mediated by four anions (in their appropriate range of concentration) had a spherical shape, narrow size distribution, and good monodispersivity. Especially, nanoparticles mediated by sulfate and TPP had a size distribution of 40-50 nm. Additionally, the nanoparticles presented high encapsulation efficiency and good protection of DNA from DNasel digestion. The zeta-potential of nanoparticles could be adjusted moderately by adding different anions and controlling their concentrations, and DNA encapsulation efficiency was not influenced, which would reduce nonspecific interactions with the cell membrane and nanoparticle toxicity. Smaller size and lower zeta-potential will be beneficial for improving gene therapy. In addition, the anion mediation method has potential for the preparation of cationic polymer nanoparticles as drug or gene vectors.

Anions↗
PubMed2005

Uptake of silica-coated nanoparticles by HeLa cells.

Nanoparticles have seen wide applications in cellular research and development. One major issue that is unclear is the uptake of nanoparticles by cells. In this study, we have investigated the uptake of silica-coated nanoparticles by HeLa cells, employing rhoadime 6G isothiocyanate (RITC)-doped nanoparticles as a synchronous fluorescent signal indicator. These nanoparticles were synthesized with reverse microemulsion. A few factors, such as nanoparticle concentration, incubation time and temperature, and serum and inhibitors in culture medium were assessed on the nanoparticle's cellular uptake. The experimental results demonstrated that uptake was maximum after a 6 h incubation and was higher at 37 degrees C than that at 4 degrees C. Nanoparticle uptake depended on the nanoparticle concentration and was inhibited by hyperosmolarity, K+ depletion. In addition, serum in culture medium decreased the cellular uptake of nanoparticles. The results indicated that the uptake of silica-coated nanoparticles by HeLa cells was a concentration-, time-, and energy-dependent endocytic process. Silica-coated nanoparticles could be transported into HeLa cells in part through adsorptive endocytosis and in part through fluid-phase endocytosis.

Coated Materials, Biocompatible↗
PubMed2004

Monitoring molecular beacon/DNA interactions using atomic force microscopy.

The molecular beacon (MB) is a new fluorescence probe containing a single-stranded oligonucleotide with a probe sequence embedded in complementary sequences that form a hairpin stem. Due to the inherent fluorescent signal transduction mechanism, an MB functions as a sensitive probe with a high signal-to-background ratio for real-time monitoring and provides a variety of exciting opportunities in DNA, RNA, and protein studies. To better understand the properties of MBs, the specific interactions between MB and target DNA (complementary and one-base mismatch) have been directly investigated by atomic force microscopy. The interaction force between a linear DNA probe and the target DNA was also detected and compared to that between MB and target DNA. The results demonstrate the high specificity of the MB/target DNA compared to the linear DNA/target DNA interaction.

DNA↗
PubMed2004

Bionanotechnology based on silica nanoparticles.

We have developed uniform core/shell nanoparticles, consisting of a silica layer coating and pigments or magnetite core, using a water-in-oil microemulsion method. The nanoparticles are highly luminescent and photostable with the size ranging from 5 nm to 400 nm. Bioconjugation of these silica nanoparticles adds unique biofunctions with various molecules such as enzymes, antibodies, and DNA molecules. Significant advantages have been shown in using bioconjugated nanoparticles for biosensing and bioimaging, such as cell staining, DNA detection and separation, rapid single bacterium detection, and biotechnological application in DNA protection.

Animals↗
PubMed2004

A novel fluorescent label based on organic dye-doped silica nanoparticles for HepG liver cancer cell recognition.

In this paper, we report a method for the recognition of HepG liver cancer cells with the use of a novel fluorescent label based on organic dye-doped fluorescent silica nanoparticles. The novel organic dye-doped silica nanoparticles are prepared with a water-in-oil microemulsion technique. The silica network is produced by the controlled synchronous hydrolysis of tetraethoxysilane and 3-amino-propyltriethoxysilane (APTES). The organic dye fluorescein isothiocyanate is doped inside as a luminescent signaling element, through covalent bonding to the amino group of APTES. The organic dye-doped core-shell nanoparticles are highly luminescent and exhibit minimal dye leaching and excellent photostability. A novel fluorescent label method based on biological fluorescent nanoparticles has been developed. The dye-doped fluorescent silica nanoparticles are covalently immobilized with anti-human liver cancer monoclonal antibody HAb18. We have used antibody-labeled fluorescent nanoparticles to recognize HepG liver cancer cells. It has been observed that the bioassay based on the organic dye-doped nanoparticles can identify the target cells selectively and efficiently. The fluorescent nanoparticle label also exhibits high photostability.

Antibodies, Monoclonal↗
PubMed2004

Luminescent nanoparticle probes for bioimaging.

Bioimaging with luminescent nanoparticle probes have recently attracted widespread interest in biology and medicine. In comparison with commonly used organic dyes, luminescent nanoparticles are better in terms of photostability and sensitivity. These optical features of nanoparticle probes are critical for real time tracking and monitoring of biological events in the cellular level, which may not be accomplished using regular fluorescent dyes. Nanoparticle probes are also shown highly suitable for immunoassay and other diagnostic and therapeutic applications. In this article, we describe a variety of optical nanoparticle probes such as quantum dots, metal nanoparticles, dye-doped nanoparticles etc. for bioimaging applications.

Fluorescent Dyes↗
PubMed2003

Real-time monitoring of nucleic acid ligation in homogenous solutions using molecular beacons.

Nucleic acids ligation is a vital process in the repair, replication and recombination of nucleic acids. Traditionally, it is assayed by denatured gel electrophoresis and autoradiography, which are not sensitive, and are complex and discontinuous. Here we report a new approach for ligation monitoring using molecular beacon DNA probes. The molecular beacon, designed in such a way that its sequence is complementary with the product of the ligation process, is used to monitor the nucleic acid ligation in a homogeneous solution and in real-time. Our method is fast and simple. We are able to study nucleic acids ligation kinetics conveniently and to determine the activity of DNA ligase accurately. We have studied different factors that influence DNA ligation catalyzed by T4 DNA ligase. The major advantages of our method are its ultrasensitivity, excellent specificity, convenience and real-time monitoring in homogeneous solution. This method will be widely useful for studying nucleic acids ligation process and other nucleic acid interactions.

DNA Ligases↗