Biomaterial Development

Some examples of our recent projects:

Highly porous microparticles Hollow fibre membranes Membranes for wound coverings Bioactive implants

Highly porous microparticles

Microparticles

Our new types of highly porous particles, made of poly(ether imides) could be suitable for multiple fields of application – for instance for modern adsorption processes or controlled release of active ingredients.

For example apheresis is an emerging technique to separate blood components from whole blood or plasma to remove pathologically elevated levels of proteins or toxins. Advantageously, the realization of apheresis by chromatographic techniques allows a selective or specific removal of blood components causing the disease. However, the particulate support material carrying the ligands is frequently not adapted to the necessities of large-volume, high molecular weight components, which have to be removed. Thus commercial support materials have the disadvantages of a too low accessibility of the internal pore system, a too poor flow-through behavior and/or a too high unspecific protein adsorption. Therefore novel support materials with optimally adapted properties profile have been developed.

Detailed description: Polyimides have been identified as novel blood compatible, steam-sterilizable materials that can be easily functionalized by wet-chemistry means. So far no suitable preparation process for the fabrication of highly porous beads is known. The Centre for Biomaterial Development develops particles from poly(ether imide) by a spraying/coagulation process. Data of the particle characteristics verify that this technique is suitable to prepare highly porous support particles, which have a high accessibility of their internal pore system.

Innovative aspect: Development of highly porous microparticles from poly(ether imide) prepared by a spraying coagulation process and achieving a particle diameter of about 100 µm and a relatively large (>10 nm) pore diameter ensuring good accessibility of large volume molecules.

Main advantages: The microparticles developed at the Centre for Biomaterial Development possess good accessibility of large volume molecules, high compression stability and can be sterilised using steam. They feature very high surface porosity as well as good chemical and mechanical stability.

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Hollow fibre membranes

CO2-foamed hollow fibre

Our new types of multi-layer hollow-fibre membranes are mainly used in medicine and biotechnology applications. Especially the preparation of hollow fibre membranes with highly asymmetric morphologies is of long term interest as they have potentials to be suitable for use as blood vessel replacements.

Detailed description: Results of our research findings show that highly asymmetric hollow fibre morphologies without any external skin can be reproducibly prepared. Their separation properties are similar to those of conventionally prepared membranes but the permeability could be improved considerably due to a distinctly reduced support layer resistance.

Innovative aspect: Preparation of highly asymmetric hollow fibre membranes from poly(ether imide) by a modified dry-wet phase inversion technique using a triple spinneret.

Main advantages: The Centre for Biomaterial Development can tailor hollow fibre membranes to your requirements by using the phase inversion process in which the polymer solution is propelled through a nozzle into a coagulation bath. Using a triple spinneret we can produce hollow fibre membranes whose inner and outer surfaces are made from different polymers.

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Membranes for wound coverings

Growth of different cells (left: human fibroblasts, center: human ceratinocytes, right: a co-culture) on varried polymeric surfaces (top: poly-acrylonitrile [PAN], center: a PAN-copolymer, bottom: tissue culture plate) each cultivated for 7 days.

Our new types of microporous, biostable membranes have promissing specifications for the cultivation of epidermal transplants. Many patients suffering from acute or chronic skin wounds require aid to enable the regeneration and restoration of normal skin structure and function. Treatment with autologous skin grafts is often not feasible if the wound size is too large or the constitution of the patient does not allow further skin injury at the donor site. Ideally, synthetic skin substitutes have to adhere to the wound site, be porous enough to allow oxygenation and removal of wound exudates, and prevent dehydration and infection.

Detailed description: For this purpose we investigated our biomaterials on cyto-toxicity and cell-specificity. Meanwhile comprehensive investigations on the interaction of these materials with primary cells and cell lines are performed.

Innovative aspect: Our cell specific materials with biofunctionality and adjustable permeability have high application potential for the development of new types of "plaster".

Main advantages: Such wound coverings permit sufficient oxygen diffusion to reach the wound while preventing the intrusion of bacteria. They are also easily removed from the surface of the wound after healing.

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Bioactive implants

Loaded Scaffold

Bioactive implants are among the most important medical innovations of our time. They can help tissues to make a full recovery from large-scale injuries. Polymers have proven to be an ideal material for making bioactive implants. The surface and volume of the polymer - the crucial factors in the implant’s design - must be defined to accord as closely as possible with the requirements of the human body. Such materials could be applicable for example in the treatment of critical sized bone defects.

Detailed description: We process biodegradable plastics into porous scaffolds as matrix materials for colonisation by cells in tissue engineering. After implantation in the body the tissue construct is intended to regenerate missing body tissue. These scaffolds can be charged with bioactive molecules such as growth factors in order to activate the body’s own regeneration processes.

Innovative aspect: We create biocompatible shaped bodies and then modify their surfaces using either wet chemical processes or modified plasma. The innovative shaped bodies that result open up a huge range of new opportunities for specific clinical application.

Main advantages: We develop CO2-foamed, i.e. solvent-free, membranes as substrates for tissue engineering applications.

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