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Biomedical subjects

Richard R Koepsel

Publications and source records attributed to Richard R Koepsel.

7 recordsLinked to original sources
PubMed2006

Surface-active antifungal polyquaternary amine.

There is a distinct need for antimicrobial compounds that can act at surfaces without leaching into the environment. Such materials should be easy to synthesize, be easy to apply to surfaces, and display reasonable levels of antimicrobial and antifungal activity. Here we describe such a surface-active compound and demonstrate its ability to inhibit the growth of the filamentous fungus Aspergillus niger. We have synthesized a series of polyquaternary ammonium compounds by atom transfer radical polymerization. Two members of this series were tested for their ability to inhibit the growth of A. niger. The compounds were dried onto surfaces, and the treated surfaces were then used as growth chambers for A. niger. A water soluble polyquaternary amine compound was shown to effectively kill A. niger in solution in a dose-dependent manner. Conversely, a water insoluble polyquaternary amine compound was shown to kill only the fungi in direct contact with the material on the surface. These results have important implications for the development of effective, environmentally benign, surface-active anti-fungal compounds.

Amines↗
PubMed2005

Surface dispersion and hardening of self-assembled diacetylene nanotubes.

We describe here the first method for dispersion of individual self-assembled diacetylene nanotubes on surfaces. Complete polymerization by UV exposure was achieved as demonstrated by nanotubes that were resistant to aggressive organic solvents and temperatures well above the melting point of the monomer. The polymerized tubes displayed reversible thermochromic and mechanochromic properties.

Journal Article↗
PubMed2003

Biomaterials for mediation of chemical and biological warfare agents.

Recent events have emphasized the threat from chemical and biological warfare agents. Within the efforts to counter this threat, the biocatalytic destruction and sensing of chemical and biological weapons has become an important area of focus. The specificity and high catalytic rates of biological catalysts make them appropriate for decommissioning nerve agent stockpiles, counteracting nerve agent attacks, and remediation of organophosphate spills. A number of materials have been prepared containing enzymes for the destruction of and protection against organophosphate nerve agents and biological warfare agents. This review discusses the major chemical and biological warfare agents, decontamination methods, and biomaterials that have potential for the preparation of decontamination wipes, gas filters, column packings, protective wear, and self-decontaminating paints and coatings.

Biocompatible Materials↗
PubMedDate not supplied

Directed capture of enzymes and bacteria on bioplastic films.

The development of smart coatings for a variety of uses depends on the ability of the coating material to perform specific functions. We have used water dispersible polyurethane preparations for the immobilization of binding proteins under mild conditions. In these experiments, antibodies against the enzyme beta-galactosidase or the bacterium Escherichia coli were immobilized in polyurethane coatings and then used to effectively capture their cognate antigen. Further, a second, more general, capture protocol was developed which involves the incorporation of the protein avidin in the plastics. This system efficiently captures biotinylated beta-galactosidase. Biotinylated anti-E. coli antibody captured by avidin bioplastics resulted in a nearly 5-fold increase in the number of bound bacteria when compared to blank polyurethane. The use of avidin in a bioplastic allows any biotinylated antibody to be applied to all or part of the surface resulting in a patterning of capture agents on a preformed surface.

Antibodies, Bacterial↗
PubMedDate not supplied

Permanent, nonleaching antibacterial surfaces. 1. Synthesis by atom transfer radical polymerization.

We have grown an antimicrobial polymer directly on the surfaces of glass and paper using atom transfer radical polymerization (ATRP). The method described here results in potentially permanent nonleaching antibacterial surfaces without the need to chemically graft the antimicrobial material to the substratum. The tertiary amine 2-(dimethylamino)ethyl methacrylate was polymerized directly onto Whatman #1 filter paper or glass slides via atom transfer radical polymerization. Following the polymerization, the tertiary amino groups were quaternized using an alkyl halide to produce a large concentration of quaternary ammonium groups on the polymer-modified surfaces. Incubating the modified materials with either Escherichia coli or Bacillus subtilis demonstrated that the modified surfaces had substantial antimicrobial capacity. The permanence of the antimicrobial activity was demonstrated through repeated use of a modified glass without significant loss of activity. Quaternary amines are believed to cause cell death by disrupting cell membranes allowing release of the intracellular contents. Atomic force microscopic imaging of cells on modified glass surfaces supports this hypothesis.

Anti-Bacterial Agents↗
PubMedDate not supplied

Regulating expression of pyruvate kinase in Bacillus subtilis for control of growth rate and formation of acidic byproducts.

Our prior work has shown that a pyk mutant of Bacillus subtilis exhibited diminished acidic byproduct accumulation, dramatically elevated phosphoenolpyruvate (PEP) pool, and reduced growth rate. To determine if a low acetate-producing but fast-growing strain of B. subtilis could be developed, we placed the expression of the pyk gene under the control of an inducible promoter. Enzyme measurements proved that PYK activity of the inducible PYK mutant (iPYK) increases with the isopropyl-beta-d-thiogalactopyranoside concentration. Batch growth experiments showed that growth rate and acid formation are closely related to the induction level of pyk. Measurements of cell growth rate and acetate formation of the iPYK mutant at different induction levels revealed that a PYK activity of about 12% of wild-type allows for good growth rate (0.4 h(-)(1) versus 0.63 h(-)(1) of wild-type) and low acetate production (0.26 g/L versus 1.05 g/L of wild-type). This is the first report to our knowledge of a metabolically engineered B. subtilis strain that allows good growth rate and low acid production in batch cultures. Finally, it was found that, by varying the pyk induction level, intracellular PEP concentration can be controlled over a wide range. The intracellular PEP concentration is intimately connected to the regulation of the transport of phosphotransferase system (PTS) sugars in the presence of glucose. Because there is no other method for modulating intracellular PEP levels, this finding represents a major advance in one's ability to dissect the function of the PTS and sugar metabolism in bacteria.

Bacillus subtilis↗