In vitro electromagnetic stimulation to enhance cell proliferation in extracellular matrix constructs with and without metallic nanoparticles.

Extremely low frequency electromagnetic fields (ELF-EMFs) can induce beneficial effects including enhanced protein synthesis and cell proliferation on healing bone and skin wounds. This study investigated the effects of ELF-EMFs on acellular tissue constructs with and without gold nanoparticles (AuNPs) to determine if cell proliferation could be increase and thus provide an enhanced mechanism for in vitro cell seeding on tissue engineered constructs. Different sized AuNPs, 20 and 100 nm, were conjugated to acellular porcine tissue, seeded with L929 murine fibroblasts and exposed to a continuous 12 gauss, 60 Hz electromagnetic field for 2 hours each day up to 10 days. Scanning electron microscopy and cell culture assays were performed to ascertain cell proliferation and viability before and after exposure. Results indicate the ELF-EMF stimulation significantly increased cell proliferation. The presence of AuNPs did not boost the stimulatory effects, but they did demonstrated higher rates of proliferation from day 3 to day 10. In addition, unstimulated 100 nm AuNPs constructs resulted in significant increases in proliferation as compared to unstimulated crosslinked constructs. In conclusion, ELF-EMF stimulation enhanced cellular proliferation and while the presence of AuNPs did not significantly enhance this effect, AuNPs resulted in increased proliferation rates from day 3 to day 10.

Assessment of the biocompatibility and stability of a gold nanoparticle collagen bioscaffold.

Collagen has been utilized as a scaffold for tissue engineering applications due to its many advantageous properties. However, collagen in its purified state is mechanically weak and prone to rapid degradation. To mitigate these effects, collagen can be crosslinked. Although enhanced mechanical properties and stability can be achieved by crosslinking, collagen can be rendered less biocompatible either due to changes in the overall microstructure or due to the cytotoxicity of the crosslinkers. We have investigated crosslinking collagen using gold nanoparticles (AuNPs) to enhance mechanical properties and resistance to degradation while also maintaining its natural microstructure and biocompatibility. Rat tail type I collagen was crosslinked with AuNPs using a zero-length crosslinker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Several characterization studies were performed including electron microscopy, collagenase assays, ROS assays, and biocompatibility assays. The results demonstrated that AuNP-collagen scaffolds had increased resistance to degradation as compared to non-AuNP-collagen while still maintaining an open microstructure. Although the biocompatibility assays showed that the collagen and AuNP-collagen scaffolds are biocompatible, the AuNP-collagen demonstrated enhanced cellularity and glycoaminoglycans (GAG) production over the collagen scaffolds. Additionally, the Reactive Oxygen Species (ROS) assays indicated the ability of the AuNP-collagen to reduce oxidation. Overall, the AuNP-collagen scaffolds demonstrated enhanced biocompatibility and stability over non-AuNP scaffolds.

Materials characterization of explanted polypropylene, polyethylene terephthalate, and expanded polytetrafluoroethylene composites: spectral and thermal analysis.

This study utilized spectral and thermal analysis of explanted hernia mesh materials to determine material inertness and elucidate reasons for hernia mesh explantation. Composite mesh materials, comprised of polypropylene (PP) and expanded polytetrafluoroethylene (ePTFE) mesh surrounded by a polyethylene terephthalate (PET) ring, were explanted from humans. Scanning electron microscopy (SEM) was conducted to visually observe material defects while attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to find chemical signs of surface degradation. Modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA) gave thermal stability profiles that showed changes in heat of fusion and rate of percent weight loss, respectively. ATR-FTIR scans showed higher carbonyl peak areas as compared to pristine for 91% and 55% of ePTFE and PP explants, respectively. Ninety-one percent of ePTFE explants also exhibited higher C--H stretch peak areas. Seventy-three percent of ePTFE explants had higher heats of fusion while 64% of PP explants had lower heats of fusion with respect to their corresponding pristines. Only 9% of PET explants exhibited a lower heat of fusion than pristine. Seventy-three percent of ePTFE explants, 73% of PP explants, and only 18% of PET explants showed a decreased rate of percent weight loss as compared to pristine. The majority of the PP and ePTFE mesh explants demonstrated oxidation and crosslinking, respectively, while the PET ring exhibited breakdown at the sites of high stress. The results showed that all three materials exhibited varied degrees of chemical degradation suggesting that a lack of inertness in vivo contributes to hernia mesh failure.