Materials characterization of explanted polypropylene hernia mesh: Patient factor correlation.

This study quantitatively assessed polypropylene (PP) hernia mesh degradation and its correlation with patient factors including body mass index, tobacco use, and diabetes status with the goal of improving hernia repair outcomes through patient-matched mesh. Thirty PP hernia mesh explants were subjected to a tissue removal process followed by assessment of their in vivo degradation using Fourier transform infrared, differential scanning calorimetry, and thermogravimetric analysis analyses. Results were then analyzed with respect to patient factors (body mass index, tobacco use, and diabetes status) to determine their influence on in vivo hernia mesh oxidation and degradation. Twenty of the explants show significant surface oxidation. Tobacco use exhibits a positive correlation with modulated differential scanning calorimetry melt temperature and exhibits significantly lower TGA decomposition temperatures than non-/past users. Chemical and thermal characterization of the explanted meshes indicate measurable degradation while in vivo regardless of the patient population; however, tobacco use is correlated with less oxidation and degradation of the polymeric mesh possibly due to a reduced inflammatory response.

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 decellularized porcine diaphragm conjugated with gold nanomaterials as a tissue scaffold for wound healing.

One million Americans suffer from chronic wounds every year with diabetics and older populations representing the majority. Mechanisms that may be responsible for the reduced healing response in these patients include reduction in growth factors or vascularization and an increase in free radical levels. The focus of this study was to develop a biocompatible gold/porcine diaphragm scaffold capable of sustaining fibroblast attachment and proliferation which was measured using viability and dsDNA assays. The free radical scavenging properties, as measured by ROS assays, were also investigated as a mechanism for improving the wound environment. Results indicated 69-89% viability for gold nanoparticle (AuNP) scaffolds and 51-74% for gold nanorod (AuNR) scaffolds as compared to 100% for decellularized scaffolds and 77% for crosslinked scaffolds. All scaffolds exhibited good cell attachment while AuNP-1X scaffolds showed the greatest cell proliferation with a 74% increase in dsDNA content from Day 3 to 7. AuNP-2X and AuNP-4X scaffolds generated higher levels of free radicals with AuNP-4X generating over twice as much as decellularized scaffolds. This study suggests the capability for gold/porcine diaphragm scaffolds to enhance cell proliferation while the modification of free radical generation appears to be dependent on nanomaterial shape and concentration.

Development and in vitro studies of a polyethylene terephthalate-gold nanoparticle scaffold for improved biocompatibility.

Polyethylene terephthalate (PET) mesh is one of the most commonly used synthetic biomaterials for tension-free hernia repair. In an effort to improve the biocompatibility of PET mesh, gold nanoparticles (AuNP) in various concentrations were conjugated to the PET surface to develop PET-AuNP scaffolds. These novel scaffolds were characterized with Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) to assess the addition of functional groups, presence of AuNPs, and thermal stability of the modified PET mesh, respectively. The biocompatibility of the PET-AuNP scaffolds was evaluated through in vitro cell culture assays. The cellularity of cells exposed to the PET-AuNP scaffolds, as well as the scaffolds' ability to reduce reactive oxygen species, was assessed using L929 murine fibroblasts. Antimicrobial properties of AuNPs conjugated to PET mesh were tested against the bacteria Pseudomonas aeruginosa. Results from the FT-IR showed presence of COOH groups while SEM displayed bonding of AuNPs to the PET surface. DSC results indicated that the PET more than likely did not undergo any detrimental degradation due to the surface modification. Results from the in vitro studies showed that AuNPs, in optimal concentrations (1× concentrations), enhanced cellularity, reduced ROS, and reduced bacteria adhesion to PET. These studies demonstrated enhanced biocompatibility of the AuNP conjugated PET mesh over pristine PET mesh.

Characterization of bionanocomposite scaffolds comprised of amine-functionalized single-walled carbon nanotubes crosslinked to an acellular porcine tendon.

Carbon nanotubes (CNT) possess many unique electrical and mechanical properties that make them useful for a variety of industrial and biomedical applications. They are especially attractive materials for biomedical applications since their dimensions are similar to components of the extracellular matrix. In this study, amine-functionalized single-walled carbon nanotubes were crosslinked to an acellular porcine diaphragm tendon. The resulting bionanocomposite scaffolds were subjected to a number of materials characterization techniques including a collagenase assay, uniaxial tensile testing, modulated differential scanning calorimetry, and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to determine whether the properties of the original extracellular matrix were altered by the treatment processes. A variety of SWCNT concentrations were investigated. While none of the conditions investigated resulted in bionanocomposites with significantly improved physicochemical properties, no detrimental effects were observed due to any of the processing steps. Future studies should be performed to determine if carbon nanotubes can influence cellular adhesion and function in order to promote rapid integration and remodeling.

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.