Biomedical subjects

K Kesenci

Publications and source records attributed to K Kesenci.

5 recordsLinked to original sources

PubMed2001

Poly(epsilon-caprolactone-co-D,L-lactide) /silk fibroin composite materials: preparation and characterization.

Poly(epsilon-caprolactone-co-D,L-lactide) copolymers with 10, 30, and 50% by weight of silk particles (size range: 5-250 microm) derived from Bombyx mori were blended in acetone solution. After evaporation of the solvent, the morphology, thermal behavior, and mechanical properties of the composites were examined. The composites were transparent and the silk fibroin particles were homogeneously distributed within the composite structure. The particles appeared as bright reflected images under the optical microscope, suggesting that they were in a crystalline state. DSC thermograms of the composites revealed that the glass transition of the matrix was at ca. -18 degrees C. Degradation of the silk fibroin occurred beyond 270 degrees C. The decomposition temperatures and degradation rate decreased with increasing silk fibroin content as revealed by TGA analysis. FTIR spectra of the composites showed absorption bands at 1730 and 1088 cm(-1) for the copolymer and at 3273 and 1617 cm(-1) for the silk fibroin. Although the characteristic lines of poly(epsilon-caprolactone-co-D,L-lactide) were independent of filler concentration. the absorption bands of the beta-sheet form of the silk fibroin increased slightly due to the interaction of silk fibroin with the copolymer.

Calorimetry↗

PubMed2000

Poly(D,L-lactide/epsilon-caprolactone)/hydroxyapatite composites.

In this study, elastomeric D,L-lactide and epsilon-caprolactone copolymers with two different molecular weights (Mn: 108.000 and 40.000) were synthesized by ring-opening polymerization of the respective dimers by using stannous octoate as the catalyst, as a potential bone-filling material. The final ratio of D,L-lactide to epsilon-caprolactone obtained by 1NMR was 60/40 (comparing to the initial ratio of 50/50). Both copolymers were amorphous having Tg at around -21 degrees C. Different amounts of hydroxyapatite (HA) powder were loaded within the copolymers. These composites were easily shaped by hand. Mechanical properties of the composites changed with the HA loading and the molecular weight of the copolymer. The percent elongation decreased, while both the Young's modulus and yield point (stress) increased with the HA content. The copolymers were degraded within the Ringer solutions in about 6 weeks. The molecular weight distribution became broader during degradation. Incorporation of HA reduced the degradation rate.

Biodegradation, Environmental↗

PubMed2000

Protein A immobilization and HIgG adsorption onto porous/nonporous and swellable HEMA-incorporated polyEGDMA microspheres.

Both non swellable and swellable poly(EGDMA/HEMA) microbeads were produced by suspension copolymerization. These microbeads were modified by immobilization of a spacer-arm (hexamethylene diamine (HMDA)) and protein A. The optimal values for modifications were as follows: sodium periodate concentration, 1.0 mgml(-1); HMDA concentration, 4 mgml(-1); and glutaraldehyde concentration, 0.070 microgml(-1). Adsorption of protein A onto the plain and periodate oxidized poly(EGDMA/HEMA) microbeads were very close to each other, and were 0.01-0.02 mg protein A on the 1-g Microbeads I and II, respectively. Protein A immobilization on poly(EGDMA/HEMA) microbeads were studied at different temperatures, times, and pHs using single protein solution containing different amounts of proteins. The optimal values for immobilization were as follows: the initial protein A concentration, 0.1 mgml(-1); temperature, 25 degrees C; pH, 9.5; and immobilization time, 120 min. Incorporation of protein A resulted in 1.420 and 1.825 mg protein A on the 1-g Microbeads I and II, respectively. HIgG adsorption capacity on the protein A-incorporated poly(EGDMA/HEMA) microbeads is 27 and 35 mg HIgGg(-1) polymer for Microbeads I and II, respectively.

Adsorption↗

PubMed2000

Preparation and properties of poly(L-lactide)/hydroxyapatite composites.

In this study, two different viscosity-average molecular weight (eta = 4.0 and 7.8) poly(L-lactide) (PLLA) were synthesized by ring-opening polymerization and the poly(L-lactide)/hydroxyapatite composites (PLLA/HA) were prepared by blending HA particles (size range: 25-45 microm and Ca/P = 1.69) with a content of 10, 30, and 50 wt% in PLLA solution with further evaporation of the solvent. The plain PLLA polymers and PLLA/HA composites were compression-molded and machined to yield 25 x 3 x 2 mm3 specimens. The molar mass of resulting specimens was decreased drastically due to the hydrolytic and thermal degradation of ester bonds. Scanning electron microscopy and thermal gravimetric results indicated that the compositions of HA in PLLA were well dispersed. With increasing HA content, the crystallinity of PLLA/HA composites are slightly increased due to the effect of HA as a nucleating agent. The dynamic mechanical analysis is useful in studying the viscoelastic behaviour of the PLLA/HA composites and no secondary relaxation was observed below the glass-to-rubber transition (60 degrees C). The mechanical properties of the PLLA/HA composites were found to vary with HA content. Increased levels of HA resulted in increased bending modulus and strength.

Absorbable Implants↗

PubMed1999

Characterization of processed tooth hydroxyapatite for potential biomedical implant applications.

In this study hydroxyapatite (HA) (100-150 microns) derived from freshly-extracted human teeth in laboratory conditions was investigated. Scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDXS), wet chemical, ion chromatographic peak method (ICP), atomic absorption, x-ray diffraction and infra-red (IR) were performed separately for HA obtained from dentine and enamel. This naturally derived HA did not differ from synthetic ones. Its production was simple when compared with other methods. Processed tooth HA could safely be used in animal subjects prior to human studies as a graft material after biocompatibility studies fully conducted.

Animals↗