Piezoelectric materials are excellent generators of clean energy, as they can harvest the ubiquitous vibrational and mechanical forces. We developed large-scale unidirectionally polarized, aligned diphenylalanine (FF) nanotubes and fabricated peptide-based piezoelectric energy harvesters. We first used the meniscus-driven self-assembly process to fabricate horizontally aligned FF nanotubes. The FF nanotubes exhibit piezoelectric properties as well as unidirectional polarization. In addition, the asymmetric shapes of the self-assembled FF nanotubes enable them to effectively translate external axial forces into shear deformation to generate electrical energy. The fabricated peptide-based piezoelectric energy harvesters can generate voltage, current, and power of up to 2.8 V, 37.4 nA, and 8.2 nW, respectively, with 42 N of force, and can power multiple liquid-crystal display panels. These peptide-based energy-harvesting materials will provide a compatible energy source for biomedical applications in the future.

Aside its historical use in contact with bone and teeth, an increasing number of studies use bioactive glasses (BG) in contact with soft tissue. BG could provide solutions for various medical problems. This study presents a first evaluation, whether BG containing silicone elastomers are a suitable material for left ventricular assist device drivelines and could enhance skin biointegration thereof. Three different nano-or microparticles of BG45S5® were incorporated into medical grade silicone elastomer and thin films of the composites were manufactured. Physicochemical, mechanical and in vitro experiments using primary human dermal fibroblasts were used to evaluate the nano-and microcomposites. The incorporation of BG particles reduced the tensile strength at break and percent elongation at break of the composites and increased the stiffness of the material. Especially the incorporation of nanosized BG decreased the percent elongation at break after immersion in SBF due to agglomerate formation and increased hydroxyapatite formation compared to commercially available microparticles. The cytocompatibility of BG containing composites increased significantly with increasing particle concentration. A clear trend regarding particle size was not observed. In general, the simple incorporation of particles into medical grade silicone elastomer allowed an easy modification of the mechanical properties and improvement in bioactivity (assessed by hydroxyapatite formation) of the material. The choice of either nano-or microparticles depends on the specific application and requirements for the material, as different particle types show different advantages and disadvantages.

Surgery of the chest wall is potentially required to cover large defects after  removal of malignant tumours. Usually, inert and non-degradable Gore-Tex serves to replace the missing tissue. However, novel biodegradable materials combined with stem cells are available that stimulate the healing. Based on poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/aCaP) and pure PLGA, a dual layer biodegradable hybrid nanocomposite was generated. Mouse adipose-derived stem cells were cultered on electrospun disks (ASCs of C57BL/6), and biomechanical tests were performed. The cell-seeded scaffolds were engrafted in C57BL/LY5.1 mice to serve as a chest wall substitute. Cell invasion into the bi-layered material, extent of CD45 + cells, inflammatory response, neo-vascularization and ECM composition were determined at 1 and 2 months post-surgery, respectively. The bi-layered hybrid nanocomposite was stable after a 2-week in vitro culture, in contrast to PLGA/aCaP without a PLGA layer. There was a complete biointegration and good vascularization in vivo . The presence of ASCs attracted more CD45 + cells (hematopoietic origin) compared to cell-free scaffolds. Inflammatory reaction was similar for both groups (±ASCs) at 8 weeks. A bi-layered hybrid nanocomposite fabricated of electrospun PLGA/aCaP and a reinforcing layer of pristine PLGA is an ideal scaffold for chest wall reconstruction. It is stable and allows a proper host tissue integration. If ASCs are seeded, they attract more CD45 + cells, supporting the regeneration process.