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Biomedical subjects

D Klee

Publications and source records attributed to D Klee.

26 records · Page 2Linked to original sources
PubMed1998

[Characterization of the properties of differently modified titanium surfaces for dental implantology. 1: Methods for surface analysis].

Contact between the biological environment and biomaterials takes place at their surfaces. The biocompatibility of a material is determined by interactions at the interface between implant and biological system. The physicochemical surface properties of the materials used, for example, chemical composition, wettability, surface energy and electrical surface charge, therefore play an important role. Within the framework of the investigations described here, specific modifications of the surfaces properties of titanium are effected using various methods with the aim of achieving a positive influence on cell growth and cell attachment. To characterize the physicochemical surface properties, X-ray photoelectron spectroscopy (XPS) have been used. In addition to the clearly altered chemical composition of the modified material surface, it proved possible to determine significant changes in the thermodynamic properties with the aid of contact angle measurements and the determination of surface energy. On the basis of these results, important information about possible interactions at the interface between implant and tissue can be obtained.

Biocompatible Materials↗
PubMed1998

[Characterization of the properties of differentially modified titanium surfaces for dental implantology. 2: In vitro biocompatibility studies].

The aim of the present study was to determine whether specific surface modifications are capable of improving the biocompatibility of a titanium surface, and whether there is a correlation between the physico-chemical properties of the implant material and its biocompatibility. To this end, the properties of titanium surfaces were modified using various methods or the latter were coated with various materials. Plasma treatments under different atmospheric conditions (N2-plasma, SO2-plasma, acetylene plasma) as well as plasma polymerization were used to affect the biological response. Characterization of the physico-chemical surface properties by means of X-ray photoelectron spectroscopy (XPS), contact angle measurements and the calculation of surface tensions or surface energy provided important information on the interactions at the interface between the implant material and the aqueous environment. The influence of the respective surface modification on cell proliferation, cell viability and the activity of mitochondrial dehydrogenases was evaluated in specific in vitro tests with human gingiva fibroblasts. It was show that different modifications of the titanium samples induce different biological responses of the gingiva fibroblasts. The results confirm the existence of correlations between thermodynamic surface properties and cellular reactions under in vitro conditions.

Cell Division↗
PubMed1997

Development of a biodegradable ureteric stent: surface modification and in vitro assessment.

The aim of the present study was to develop a short bioresorbable ureteric stent and to characterize the chosen polymers with respect to surface modification, biocompatibility, and loading of a biologically active compound. As materials for the stent, poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) were chosen. Degradation experiments were carried out and analytical data were obtained by contact angle measurement, X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy in the attenuated reflection mode (FTIR-ATR). Gas loading technology was used to incorporate biologically active compounds, and biocompatibility of the polymers was assessed by in vitro cellular assays, applying measures such as cell morphology, proliferative activity, and membrane integrity. Our results indicate that surface modification of bioresorbable polymers is a suitable and efficient approach to improve the surface properties. Incorporation of biologically active compounds was possible without loss of activity, and in vitro assessment of cellular responses demonstrated the biocompatibility of the chosen polymers and modifications.

Absorption↗
PubMed1995

Development and characterization of a wettable surface modified aromatic polyethersulphone using glow discharge induced HEMA-graft polymerisation.

The aromatic polyethersulphone (PES) is a well known polymer for the preparation of membranes with excellent thermal stability and chemical resistance. The disadvantage of PES-membranes is their hydrophobic character, which in contact with protein containing solutions leads to high protein adsorption and as a consequence to deterioration of membrane properties. In this report the surface modification of PES by means of glow discharge induced grafting of 2-hydroxyethyl methacrylate (HEMA) is described. Graft polymerisation creates a largely wettable layer of poly(2-hydroxyethyl methacrylate) (PHEMA) on the surface of PES. This has been shown by contact angle measurements using the Wilhelmy plate method. Chemical characterization is carried out by means of X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy/attentuated total reflection (FTIR-ATR). The influence of storage conditions on the surface properties of modified PES samples has been investigated after storage in vacuum, water, and air.

Journal Article↗
PubMed1993

Infective endocarditis due to Fusobacterium nucleatum: case report and review of the literature.

Endocarditis caused by Fusobacterium nucleatum is exceedingly rare. We report a case of F. nucleatum right-sided endocarditis in a patient with no known intravenous drug abuse. A detailed computer and manual search of the literature using Med-Line and Index Medicus, respectively, revealed a total of five cases of endocarditis due to this species. The clinical characteristics and the patient's hospital course are summarized and reviewed.

Dental Caries↗
PubMed1991

Plasma-induced surface modifications on silicone intraocular lenses: chemical analysis and in vitro characterization.

In contrast to the high standard of intraocular lens implantation today, lens fixation and the occurrence of secondary opacifications are still not satisfactory. We are working on an implant that builds a stable connection to the surrounding lens-capsule. Disc-shaped lenses made of poly(dimethylsiloxane) were treated with different kinds of plasma to bring functional groups to the surface. This allows further macromolecular coating. The results of the surface modifications were characterized by electron spectroscopy for chemical analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and cell culture experiments. O2 plasma induces a rapid increase of functional groups on the lens surface. CO2 plasma has to be used for longer treatment periods to achieve the same increase, but as SEM shows, did not lead to surface damage up to periods of 300 s. Using O2 plasma for longer than 60 s, a crack formation occurred. Therefore, CO2 plasma may be a more effective and sensitive tool in grafting functional groups to the surface.

Biocompatible Materials↗
PubMedDate not supplied

Comparison of coatings from reactive star shaped PEG-stat-PPG prepolymers and grafted linear PEG for biological and medical applications.

Grafting of poly(ethylene glycol) (PEG) is a common strategy for reducing nonspecific interactions of surfaces with proteins. We have used grafting at "cloud point" solution conditions that ensures maximum grafting density of linear methoxy terminated PEG-aldehyde (mPEG-ald, M(w) = 5000 and 30000). In an alternative approach, surfaces were modified with layers prepared from isocyanate terminated, star shaped poly(ethylene glycol-stat-propylene glycol) prepolymers (80% ethylene glycol, six arms, M(w) = 3000, 12,000, and 18,000; this compound will be referred to as "Star PEG" in the text). Due to the highly reactive endgroups, these molecules form a dense network on the substrate with a high polymer surface coverage. The two systems were compared regarding their ability to prevent unspecific adsorption of insulin and lysozyme. The layers were analyzed by ellipsometry, contact angle measurements, and XPS. Protein adsorption was monitored by surface MALDI-TOF MS and fluorescence microscopy. No protein adsorption could be detected on Star PEG coatings and on mPEG-ald 5000, whereas mPEG-ald 30,000 could only prevent adsorption of lysozyme but not of the smaller insulin.

Adsorption↗