Advanced Engineering Materials

Cell adhesion plays an important role for the biocompatibility and biological performance of medical implants. Depending on where the biomaterial is implanted, cell adhesion may or may not have a positive impact on its biological performance. Polytetrafluoroethylene (PTFE) is a widely used biomaterial for vascular prostheses because of its outstanding biological performance, especially when in contact with blood. However, PTFE and certain other polymer biomaterials fail in contact with connective tissue. Therefore, the aim of this work was to improve the performance of PTFE surfaces for the adhesion of living cells without changing the distinct chemical properties of the material. The objectives were achieved by laser ablation of the PTFE surface and the creation of a well-defined micro topography without modification of the chemical composition of the surface.

Despite a number of shortcomings biomaterials for implants have not changed much during the last decades. Yet, there is a revolution ongoing in fundamental biomaterials science research, which introduces new concepts and may help to answer a number of open questions. Bioactive and biomimetic nanomaterials in zero, one or two dimensions may be at the brink of transfer to clinical testing and application. These materials will in the future intervene actively in biological processes, such as protein adsorption, cell binding and growth.

Tissue engineering needs a biomaterial as a framework for single cells to build a vital and well functioning tissue. A future challenge is to modify biomaterials used this purpose in a way that they imitate in their composition and/or structure the native and physiological conditions for the tissue specific cells. This review gives a survey about types of the used biomaterials, processing techniques and biomimetic aspects.

Recent findings have generated new interest in the biomaterial properties of silica-containing structures useful for bone replacement. The sol-gel-route seems to be most appropriate to mimic biological processing because it works under ambient conditions and furthermore allows the formation of a mineral phase from solution and the integration of a second component. The present work provides a strategy to mimic the natural processes of biosilicification under ambient conditions. By going beyond the nano- and micro-level, the authors established an advanced procedure for the preparation of monolithic silica-collagen hybrid xerogels.

Fatigue failure of cortical bone may be observed in vivo after severe cyclic loading. In vitro hysteresis measurements are strongly influenced by time-dependent deformation and microcrack formation. Load increase tests with recovery cycles and/or adapted loading velocity together with microstructural investigations offer a good possibility to discriminate between the influence of loading velocity and microstructural damage on the hysteresis parameters.

Nanoparticles of calcium phosphate were electrophoretically deposited on silicon and then structured by laser direct writing. Osteoblast-like cells showed a good proliferation and also an orientation along the parallel laser-written lines.

A novel hydrogel composite is reported in this study, which was derived from oxidized alginate, gelatin and tricalcium phosphate (TCP). The physical and biological properties of these hydrogel composites prepared with oxidized sodium alginate with different oxidation degrees were investigated. The drug delivery potential of this hydrogel composite as a carrier was evaluated by using Vitamin B2 as a model drug as well. An in vitro investigation with encapsulation of osteoblast revealed that these composites were biocompatible. This hydrogel composite presented here may be utilized for the fabrication of potential injectable systems for tissue engineering, drug delivery and other medical applications.

Ultra high molecular polyethylene (UHMWPE) is used in artificial knee joints and therefore subjected to cyclic loading. The hysteretic thermo-mechanical response of medical grade ultra high molecular weight polyethylene under compressive cyclic loading at high stress levels was investigated. It was shown that the repeated loading leads to heat dissipation that heavily alters the properties of the polyethylene and is crucial to its fatigue behaviour.

The interface between materials with very different properties is quite often the weakest point in a construction. Interfaces of metal implants into bone are particularily prone to failure, a major cause for reparative surgery. The present study explores the natural interface between cartilage and bone in order to provide for potentially alternative surface textures and to allow deduction of the rules of construction governing those interfaces.

Cell adhesion plays an important role for the biocompatibility and biological performance of medical implants. Depending on where the biomaterial is implanted, cell adhesion may or may not have a positive impact on its biological performance. Polytetrafluoroethylene (PTFE) is a widely used biomaterial for vascular prostheses because of its outstanding biological performance, especially when in contact with blood. However, PTFE and certain other polymer biomaterials fail in contact with connective tissue. Therefore, the aim of this work was to improve the performance of PTFE surfaces for the adhesion of living cells without changing the distinct chemical properties of the material. The objectives were achieved by laser ablation of the PTFE surface and the creation of a well-defined micro topography without modification of the chemical composition of the surface.

Since many years, amorphous carbon films (a-C, a-C:H, DLC) have attracted much attention for applications with regard of their promising biomedical and biofunctional properties. The blood coagulation mechanism on a-C surfaces is not yet exactly understood. In this work, the behaviour of platelets adhered onto amorphous carbon films (a-C) is described from a macroscopic point of view.

Recently, the microstructuring of biological species, such as proteins, using microcontact printing (μCP), has become very popular. Microstructuring of proteins is useful for a variety of applications, such as biosensors, controlled cell growth and adhesion and microarrays for bioanalytical detection. Here the authors investigated the microcontact printing of proteins using a hydrophilic thermoplastic elastomeric stamp material. The emphasis is placed on the quality of the printed patterns with respect to inking time and protein concentration in the ink.

The hierarchical self-assembly of collagen type II, the major fibril-forming collagen of cartilage, has been studied by atomic force microscopy (AFM). The fibrillation of human collagen type II in simulated body fluid (SBF) was investigated by varying the incubation time, pH, and temperature as well as the collagen concentration. The results reveal that the collagen type II fibrillogenesis process from procollagen into D-banded fibrils is entropy driven, and that incubation at low temperature leads to the formation of distinct hierarchical supramolecular assemblies.

In the current study a new composite material comprising calcium sulphate, calcium carbonate, and tripalmitin was developed as a bioresorbable drug carrier for the local antibiotic therapy. Device fabrication can be simply performed by compression moulding of the components. The evaluated bone substitute material based on a calcium sulphate/calcium carbonate composite exhibits an excellent biocompatibility and a therapeutically useful release profile. It, therefore, represents a promising new antibiotic delivery system for the efficient prevention and treatment of bone infections.

Hydrogels are attractive materials for biomedical applications due to their versatility and excellent biocompatibility. In this study, the authors report the preparation of poly(ethylene glycol) (PEG) based hydrogels for intraocular applications. Transparent hydrogels were formed in situ upon chemical reaction of these macromers. The cross-linked hydrogels showed no cytotoxic effects and may be used as vitreous substitutes or intraocular drug release systems.