Modification of silicone elastomers with Bioglass 45S5® increases in ovo tissue biointegration

Silicone is an important material family used for various medical implants. It is biocompatible, but its bioinertness prevents cell attachment, and thus tissue biointegration of silicone implants. This often results in constrictive fibrosis and implant failure. Bioglass 45S5® (BG) could be a suitable material to alter the properties of silicone, render it bioactive and improve tissue integration. Therefore, BG micro- or nanoparticles were blended into medical-grade silicone and 2D as well as 3D structures of the resulting composites were analyzed in ovo by a chick chorioallantoic membrane (CAM) assay. The biomechanical properties of the composites were measured and the bioactivity of the composites was verified in simulated body fluid. The bioactivity of BG-containing composites was confirmed visually by the formation of hydroxyapatite through scanning electron microscopy as well as by infrared spectroscopy. BG stiffens as prepared non-porous composites by 13% and 36% for micro- and nanocomposites respectively. In particular, after implantation for 7 days, the Young's modulus had increased significantly from 1.20 ± 0.01 to 1.57 ± 0.03 MPa for microcomposites and 1.44 ± 0.03 to 1.69 ± 0.29 MPa to for nanocpmosites. Still, the materials remain highly elastic and are comparably soft. The incorporation of BG into silicone overcame the bioinertness of the pure polymer. Although the overall tissue integration was weak, it was significantly improved for BG-containing porous silicones (+72% for microcomposites) and even further enhanced for composites containing nanoparticles (+94%). These findings make BG a suitable material to improve silicone implant properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B: Appl Biomater, 2018

Bioactive glass containing silicone composites for left ventricular assist device drivelines: role of Bioglass 45S5® particle size on mechanical properties and cytocompatibility

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.ISSN:0022-2461ISSN:1573-480

Hybrid nanocomposite as a chest wall graft with improved integration by adipose-derived stem cells

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