Fine-tuning of substrate architecture and surface chemistry promotes muscle tissue development

Tissue engineering has been increasingly brought to the scientific spotlight in response to the tremendous demand for regeneration, restoration or substitution of skeletal or cardiac muscle after traumatic injury, tumour ablation or myocardial infarction. In vitro generation of a highly organized and contractile muscle tissue, however, crucially depends on an appropriate design of the cell culture substrate. The present work evaluated the impact of substrate properties, in particular morphology, chemical surface composition and mechanical properties, on muscle cell fate. To this end, aligned and randomly oriented micron (3.3±0.8 μm) or nano (237±98 nm) scaled fibrous poly(ε-caprolactone) non-wovens were processed by electrospinning. A nanometer-thick oxygen functional hydrocarbon coating was deposited by a radio frequency plasma process. C2C12 muscle cells were grown on pure and as-functionalized substrates and analysed for viability, proliferation, spatial orientation, differentiation and contractility. Cell orientation has been shown to depend strongly on substrate architecture, being most pronounced on micron-scaled parallel-oriented fibres. Oxygen functional hydrocarbons, representing stable, non-immunogenic surface groups, were identified as strong triggers for myotube differentiation. Accordingly, the highest myotube density (28±15% of total substrate area), sarcomeric striation and contractility were found on plasma-coated substrates. The current study highlights the manifold material characteristics to be addressed during the substrate design process and provides insight into processes to improve bio-interfaces.

The short-term effect of hippotherapy on spasticity in patients with spinal cord injury

STUDY DESIGN

Assessment of spasticity before and after hippotherapy treatment.

OBJECTIVE

To evaluate the short-term effect of hippotherapy on spasticity of spinal cord injured patients (SCIs).

SETTING

Swiss Paraplegic Centre, Nottwil.

METHODS

32 patients with spinal cord injury with various degrees of spasticity had repeated sessions (mean 11) of Hippotherapy-K. Spasticity of the lower extremities was scored according to the Ashworth Scale.

RESULTS

In primary rehabilitation patients Ashworth values after hippotherapy were significantly lower than before (Wilcoxon's signed-rank test: P<0.001). Highest improvements were observed in SCIs with very high spasticity. No significant difference between short-term effect in paraplegic and short-term effect in tetraplegic subjects was found.

CONCLUSIONS

Hippotherapy significantly reduces spasticity of lower extremities in SCIs.

XPS, AES, and AFM as tools for study of optimized plasma functionalization

The plasma-based surface modification of polymer materials with desirable bulk properties is a useful way to obtain polymers with tailor-made surface properties. This is necessary because the surface properties of most engineering polymers in use today are less then optimum for many applications. New functionalities such as biocompatibility, adhesion, special functional groups as well as lubricative, friction and wear-and-tear properties are demanded. By optimization of the process parameters during a low pressure plasma treatment, most of these requirements can be fulfilled. A specific functionalization with, e.g., carboxyl, amino, epoxy or hydroxyl groups as well as the generation of ultra thin layers with those functionalities is possible. The most challenging problem is not only to find parameters which do not lead to a fragmentation of the monomeric structure, but moreover the adhesion of the thin films to the substrates must overcome a stability test without delamination. To optimize plasma processes, with their great variety of parameters influencing the obtained surface properties, several surface analytical techniques are indispensable. XPS, AES as well as AFM are helpful tools to characterize the modified sample surfaces and consequently optimize the set of parameters for the glow discharge treatment. With XPS the retention of the monomer structure can be controlled. AES depth profiling clarifies the elemental composition of gradient layers, necessary for a good adhesion of scratch-resistant coatings. AFM visualizes the surface morphology which is important for, e.g., the friction properties of plasma-coated substrates.

Improving the Stability of Amino-Containing Plasma Polymer Films in Aqueous Environments

Plasma polymer films that contain amine groups (NH₂-PPFs) are known to degrade over time, particularly in aqueous environments. To reduce such aging effects, a vertical chemical gradient regarding the amine group density was explored ranging over a few nanometers at the coating surface. The gradient-containing nanofilms were formed in low-pressure plasma by tuning plasma conditions while keeping the plasma "switched on". The coating process started with a more cross-linked NH₂-PPF (70 W, 4:7 NH₃/C₂H₄), followed by the deposition of a few nanometers of a less cross-linked yet more functional NH₂-PPF (50 W, 7:7 NH₃/C₂H₄). Characterization of the prepared gradient coatings showed that the chemical composition depends on the NH₃/C₂H₄ gas flow ratio, as observed by different analytical methods: plasma diagnostics during deposition and depth profiling analyses of the deposited coating. Finally, surface chemistry was analyzed during air and water aging, showing a similar aging process of the NH₂-PPF single layer and NH₂-PPF with a vertical chemical gradient in air, while the stability of the gradient coating was found to be enhanced under aqueous conditions maintaining an [NH₂]/[C] amount of ∼1%.