Biomedical Membranes Research Articles

Collagen‐apatite nanocomposite membranes for guided bone regeneration

Collagen-apatite nanocomposite is regarded as a potential biomaterial because of its composition and structure, which are similar to those of human hard tissues. However, there have been few investigations of its mechanical and biological benefits in direct comparison with a collagen equivalent. Herein, we successfully produced a biomedical membrane made of a nanocomposite, and systemically evaluated the mechanical, chemical, and biological properties of the nanocomposite in comparison with those of pure collagen. The results showed that significant improvements were achieved by the nanocomposite approach, particularly in terms of the mechanical strength and chemical stability. The present findings point to the potential usefulness of the collagen-apatite nanocomposite membrane in the field of guided bone regeneration (GBR).

Nanofiber Generation of Gelatin–Hydroxyapatite Biomimetics for Guided Tissue Regeneration

AbstractThe development of biomimetic bone matrices is one of the major goals in the bone‐regeneration and tissue‐engineering fields. Nanocomposites consisting of a natural polymer and hydroxyapatite (HA) nanocrystals, which mimic the human bone matrix, are thus regarded as promising bone regenerative materials. Herein, we developed a biomimetic nanocomposite with a novel nanofibrous structure by employing an electrospinning (ES) method. The HA precipitate/gelatin matrix nanocomposites are lyophilized and dissolved in an organic solvent, and then electrospun under controlled conditions. With this process, we can successfully generate a continuous fiber with a diameter of the order of hundreds of nanometers. The internal structure of the nanofiber features a typical nanocomposite, i.e., HA nanocrystals well distributed within a gelatin matrix. These nanocomposite fibers improve the bone‐derived cellular activity significantly when compared to the pure gelatin equivalent. This method of generating a nanofiber of the biomimetic nanocomposite was effective in producing a biomedical membrane with a composition gradient, which is potentially applicable in the field of guided tissue regeneration (GTR).

In vitro degradation and cytocompatibility evaluation of novel soy and sodium caseinate-based membrane biomaterials.

Soy- and casein-based membranes are newly proposed materials disclosing a combination of properties that might allow for their use in a range of biomedical applications. Two of the most promising applications are drug delivery carrier systems and wound dressing membranes. As for all newly proposed biomaterials, a cytotoxic scanning must be performed as a preliminary step in the process of the determination of the compatibility with biological systems (biocompatibility). In this study, the cytotoxicity of both soy- and casein-based protein biomaterials has been evaluated and correlated with the materials degradation behavior. It was possible to show, through morphological and biochemical tests that these natural origin materials do not exert any cytotoxic effect over cells, and in some cases can in fact enhance cell proliferation. The different treatments to which the membranes were subjected during their processing (that include crosslinking with glyoxal and tannic acid, and physical modification by thermal treatment) seemed to have a clear effect both on the materials mechanical properties and on their in vitro biological behavior.

Surface characterization of biocompatible polysulfone membranes modified with poly(ethylene glycol) derivatives

Self-transformable and blood compatible devices of sulfonated poly(ethylene glycol) acrylate diblock copolymer (PEG-SO3A/OA) with hydrophilic and hydrophobic block entrapped to polysulfone membrane surface were investigated in terms of the degree of hydrophilicity. The asymmetric membrane was formed by phase inversion process, and the induced hydrophilicity by reorientation of diblock copolymer at interface was verified with contact angle measurement, electron spectroscopy for chemical analysis (ESCA) depth profiling with ion sputtering and platelet adhesion test. Molecular dynamics (MD) simulations for the interface of hydration layer were also performed with various hydrophilic copolymer densities to gain optimum interfacial structure in information. The dependency of water clustering behavior around diblock copolymers as a hydrophilicity parameter was described in terms of atom-atom radial distribution function (RDF). The results showed that the diblock copolymer entrapped surfaces demonstrated less platelet adhesion than control or copolymers having no hydrophobic blocks. In addition, oxygen composition significantly began to decrease deeper into the membrane, indicating the reorientation of diblock chains. Copolymer entrapped surfaces significantly induced the degree of water clustering, and the resulting equilibrium rearrangement of interfacial structures was distinctly dependent upon the density of copolymer. Taken together, the results show that the novel concept ofin situ self-transformable surface modification strategy was successfully developed for biocompatible ultrathin biomedical membrane device.

Reutilizing and retesting of parallel plate sensors in dielectric thermal analysis

One of the advantages of dielectric thermal analysis (DETA) is that the parallel plate sensors are disposable, thereby eliminating potentially time-consuming clean-up procedures. Nonetheless, sometimes the reusing of parallel plate sensors is desirable, for example, when the test material is limited, further processing is intended, or cyclic testing is required. In this experiment, multiple-run and single-run methodologies were performed, the former without unloading the ram, and the latter after unloading the ram, removing the specimen, and cleaning the sensor. A dummy biomedical membrane was cast from a tetrahydrofuran solution of highly plasticized poly(vinyl chloride). After running each DETA experiment at a heating rate of 3°C min −1 from −20 to + 80°C at 1, 10, and 100 Hz, no significant differences were observed for permittivities, loss factors, tan deltas, ion conductivities, or the membrane thicknesses at room temperature. When calibrated, sensor areas varied by ±1%, and thermistor values varied by ±0.5%. From comparative graphs, box-plots, and statistical analyses, the data confirm that parallel plate sensors can be reutilized for retesting with these biomedical membranes.

Mechanical Test Methods for Biomedical Membranes

It is important to estimate the mechanical characteristics and strength of biomedical membrane. For this purpose, previously we have proposed several mechanical test methods for biomedical membranes. To establish the safety design for biomedical membrane, such as cellophane membrane for hemodialysis, it is important to estimate the viscoelastic characteristics of these materials. On the other hand, artificial biomedical membrane such as tympanic membrane, are subjected to noncontact internal air pressure under the membranous state. To estimate mechanical characteristics of such membrane, it is necessary to develop a well-simulated test under the gaseous pressure and the other mechanical test under the membranous state. In this paper, several test methods for these purposes were shown. Furthermore, results obtained by these methods were shown and related to clinical problems. These proposed test methods are quite different from the axial tensile test. But they are also important to estimate the mechanical property of biomedical membrane. Each result obtained by these test methods has its own significance. By selection of the most suitable test method for each purpose and revealing these mutual relations, safety design of artificial organs can be performed from the viewpoint of the strength.

タンパク質の吸着を抑制するポリマーの合成と医用膜への応用

タンパク質の吸着を抑制するポリマーの合成と医用膜への応用

Biaxial Testing of Membrane Biomaterials: Testing Equipment and Procedures

A testing facility for measuring the biaxial mechanical properties of highly deformable membranes is described. Forces are applied, via strain-gauge force transducers, to four points on each side of an initially square 12 to 25 mm membrane sample to produce biaxial extensions of up to 80 percent of undeformed length. Strain is estimated from the displacement of markers bounding a 1 to 2 mm central square. The accuracy of stress and strain field measurements has been assessed by finite element analysis of a biaxially-loaded isotropic elastic membrane. Major advantages of the present system over those previously described in the literature are that 1) sample mounting procedures are simplified, 2) there is provision for independent adjustment of stress field uniformity and measurement of the applied point forces and 3) faster strain rates can be imposed on the relatively small samples tested.

Mechanical Test Methods of Biomedical Membranes such as Used for Otolaryngology

Biomedical membranes, such as artificial tympanic membranes, are subject to noncontact internal air pressure. To estimate mechanical characteristics of such membranes, it is necessary to carry out the noncontact pressure test and membranous contact test, in addition to the usual monotonic tensile test, by using a rectangular specimen cut from the membranes. In this paper, these mechanical test methods and results on such biomedical membranes were studied. Some of the authors have already presented the mechanical test methods of cellophane membrane for hemodialysis under applied water pressure. Herein, we are concerned with the mechanical test methods of biomedical membranes such as tympanic membrane, in which gaseous pressure was applied.

A new colorimetric method for the determination of the “dissolved” oxygen permeability coefficients of polymeric membranes

The polarographic technique which is used in the measurement of the “dissolved” oxygen permeability coefficient ( P d) of biomedical membranes frequently results in confused data due to stagnant boundary layer formation at the polymer—liquid interface in the unstirred small cell and due to the electrode polarization, electrochemical side reactions during measurement. A novel colorimetric method that can overcome these problems and is capable of measuring P d in a short time was developed. The method is based on the colorimetric determination of the dissolved oxygen in a reduced indigo—carmine solution at 700 nm wavelength. P d values of polymer membranes such as low density polyethylene, poly-4-methylpent-l-ene, polystyrene, ethylene—vinyl acetate copolymer and siloxane—acrylate copolymer were measured and were found to be in good agreement with those determined by the polarographic method. The colorimetric method resulted in higher P d values for less permeable polymer membranes than the polarographic method due to the absence of boundary layer formation caused by stirring the solution in the cell