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Biomedical subjects

P B Messersmith

Publications and source records attributed to P B Messersmith.

5 recordsLinked to original sources
PubMed2005

Enzymatically cross-linked hydrogels and their adhesive strength to biosurfaces.

OBJECTIVES: To design an in-situ gelling hydrogel capable of solidifying rapidly under physiologic conditions into a hydrogel capable of adhering tissue surfaces together. DESIGN: Multifunctional polymers containing covalently bound peptide substrates of transglutaminase were designed. EXPERIMENTAL VARIABLE: Enzyme cross-linked hydrogels were compared with commercial fibrin tissue adhesive. OUTCOME MEASURE: The shear strength between tissue surfaces or type 1 collagen membranes bonded with hydrogel was measured. RESULTS: The shear adhesive strength of transglutaminase cross-linked hydrogels was found to be equal to or better than fibrin sealant for tissue and collagen surfaces, respectively. CONCLUSION: Transglutaminase cross-linked hydrogels are injectable, in-situ formed, biodegradable, and expected to be useful in a variety of applications including sustained drug delivery, medical and dental adhesives, tissue repair and engineering as polymeric scaffolds, and gene therapy.

Adhesiveness↗
PubMed2001

Triggered release of calcium from lipid vesicles: a bioinspired strategy for rapid gelation of polysaccharide and protein hydrogels.

The bioinspired strategy of triggered release of Ca2+ from liposomal compartments was used to induce rapid gelation of polysaccharide and protein-based hydrogels. Thermally triggerable liposomes were designed by entrapping CaCl2 within liposomes constructed of 90% dipalmitoylphosphatidylcholine and 10% dimyristoylphosphatidylcholine. These liposomes released greater than 90% of entrapped Ca2+ when heated to 37 degrees C. A precursor fluid containing liposomes suspended in aqueous sodium alginate remained fluid for several days at room temperature but gelled rapidly when heated to 37 degrees C, as a result of Ca2+ release and formation of crosslinked Ca-alginate. Alternatively, thermally triggered Ca2+ release from liposomes was used to activate enzyme-catalyzed crosslinking of proteins to form hydrogels. A mixture of Ca-loaded liposomes, fibrinogen, and a Ca2+-dependent transglutaminase enzyme (either human recombinant FXIII or guinea pig liver transglutaminase) remained fluid indefinitely when stored at room temperature, but gelled rapidly when heated to 37 degrees C. SDS-PAGE of the reaction mixture revealed that gelation was due to enzymatic crosslinking of the alpha and gamma chains of fibrinogen, and oscillating rheometry revealed gel formation within 10 min of heating to 37 degrees C. This new approach may be useful for developing rapidly gelling injectable biomaterials that can be stored at room temperature and injected in a minimally invasive manner into a body tissue or cavity, upon which rapid solidification would occur. This versatile bioinspired strategy could be utilized for the delivery of biomaterials for tissue repair and reconstruction, and local site-directed drug delivery.

Calcium↗
PubMed1998

New acrylic resin composite with improved thermal diffusivity.

STATEMENT OF PROBLEM: Studies have shown that physical characteristics of denture base materials may affect patient acceptance of denture prostheses by altering sensory experience of food during mastication. Thermal diffusivity is one material property that has been cited as being important in determining gustatory response, with denture base acrylic resins having low thermal diffusivity compared with denture base metal alloys. PURPOSE: This study prepared and characterized experimental acrylic resin composite material with increased thermal diffusivity. MATERIAL AND METHODS: Sapphire (Al2O3) whiskers were added to conventional denture base acrylic resin during processing to achieve loadings of 9.35% and 15% by volume. Cylindrical test specimens containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 degree to 70 degrees C). RESULTS: Thermal diffusivities of the sapphire containing composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the volume percentage of sapphire filler, which suggested that the high aspect ratio ceramic particles formed a pathway for heat conduction through the insulating polymer matrix. CONCLUSION: The thermal diffusivity of denture base acrylic resin was increased by the addition of thermally conducting sapphire whiskers.

Acrylic Resins↗
PubMed1990

Stress enhancement and fatigue susceptibility of porous coated Ti-6Al-4V implants: an elastic analysis.

An elastic stress analysis of porous-coated implant surfaces was performed using the finite element method. Three-hundred-microns-diameter metal beads sinter bonded onto an implant surface were modeled with sinter neck radii of 5, 10, 20, and 50 microns. Smooth-surface, single-bead, single-layer, and double-layer systems were analyzed. The finite element models were loaded to simulate bone-bead contact forces and lateral hip implant tensile forces. Results showed that, for a single bead sinter-bonded onto an implant surface, concentration of stress occurs either at the base of the sinter neck or within the neck itself, depending on the type of load applied. Under lateral hip implant tensile loads, a maximum stress concentration factor of 1.97 was obtained for a single bead sinter-bonded onto a implant surface. Addition of a single layer of beads onto the implant surface resulted in a significant increase in stress at the most proximal and distal ends of the porous layer, with a maximum stress concentration factor of 4.3. Addition of a second layer of beads did not significantly increase the magnitude of the stress concentration occurring at the ends of the porous layer. The results of this study provide stress concentration factors for porous coatings with sinter necks of known dimensions under loading conditions similar to those present along the lateral surface of a hip prosthesis.

Alloys↗