John D. Jarrell

Controlled release of vanadium from titanium oxide coatings for improved integration of soft tissue implants.

This study evaluates the potential of titanium oxide coatings for short-term delivery of vanadium for improved wound healing around implants. Titanium and vanadium oxides are bioactive agents that elicit different bioresponses in cells, ranging from implant integration and reduction of inflammation to modulation of cell proliferation and morphology. These oxides were combined in biomaterial coatings using metal-organic precursors and rapidly screened in cell-culture microplates to establish how vanadium-loading influences cell proliferation and morphology. Twenty-eight-day elution studies indicated that there was a controlled release of vanadium from stable titanium oxide matrices. Elution profiles were mathematically modeled for vanadium loading of 20-1.25% up to a period of 28 days. Scanning electron microscopy and energy dispersive spectroscopy of the coatings indicated that the vanadium was present as a nanoscale dispersion and not segregated micron-scale islands. The study confirmed that the observed bioresponse of cells was modulated by the soluble release of vanadium into the surrounding medium. Controlled release of vanadium from titania coatings may be used to influence soft-tissue integration of implants by modulating cell proliferation, attachment, inflammation, and wound healing dynamics.

In vivo caprine model for osteomyelitis and evaluation of biofilm-resistant intramedullary nails.

Bone infection remains a formidable challenge to the medical field. The goal of the current study is to evaluate antibacterial coatings in vitro and to develop a large animal model to assess coated bone implants. A novel coating consisting of titanium oxide and siloxane polymer doped with silver was created by metal-organic methods. The coating was tested in vitro using rapid screening techniques to determine compositions which inhibited Staphylococcus aureus growth, while not affecting osteoblast viability. The coating was then applied to intramedullary nails and evaluated in vivo in a caprine model. In this pilot study, a fracture was created in the tibia of the goat, and Staphylococcus aureus was inoculated directly into the bone canal. The fractures were fixed by either coated (treated) or non-coated intramedullary nails (control) for 5 weeks. Clinical observations as well as microbiology, mechanical, radiology, and histology testing were used to compare the animals. The treated goat was able to walk using all four limbs after 5 weeks, while the control was unwilling to bear weight on the fixed leg. These results suggest the antimicrobial potential of the hybrid coating and the feasibility of the goat model for antimicrobial coated intramedullary implant evaluation.

Rapid screening, in vitro study of metal oxide and polymer hybrids as delivery coatings for improved soft-tissue integration of implants.

Metal-organic chemistry allows for molecular mixing and creation of a range of submicron phase-separated structures from normally brittle metal oxides and flexible polymers with improved bioactivity and delivery properties. In this study, we used a high throughput platform to investigate the influence of organic metal oxide doping of polydimethylsiloxane (PDMS) coatings on cellular bioactivity and controlled release of vanadium compared with titanium oxide coatings without additional PDMS. Metal-organic-derived titanium and or vanadium was doped into PDMS and used to form a coating on the bottom of cell culture microplates in the absence of added water, acids, or bases. These hybrid coatings were rapidly screened to establish how titanium and vanadium concentration influences cell proliferation, adhesion, and morphology. We demonstrate that titanium doping of PDMS can be used to improve cell proliferation and adhesion, and that vanadium doping caused a biphasic dose response in proliferation. A 28-day vanadium and titanium elution study indicated that titanium was not released, but the presence of PDMS in coatings increased delivery rates of vanadium compared with titania coatings without polymer. Hybrid coatings of titanium-doped polymers have potential for improving wound healing dynamics, soft-tissue integration of medical implants, and use as controlled delivery vehicles.

Silver doped titanium oxide-PDMS hybrid coating inhibits Staphylococcus aureus and Staphylococcus epidermidis growth on PEEK.

Bacterial infection remains one of the most serious issues affecting the successful installation and retention of orthopedic implants. Many bacteria develop resistance to current antibiotics, which complicates or prevents traditional antibiotic-dependent eradication therapy. In this study, a hybrid coating of titanium dioxide and polydimethylsiloxane (PDMS) was synthesized to regulate the release of silver. The coatings were benefited from the antimicrobial activity of silver ion, the biocompatibility of titanium dioxide, and the flexibility of the polymer. Three studied silver doped coatings with different titanium dioxide-PDMS ratios effectively inhibited the attachment and growth of Staphylococcus aureus and Staphylococcus epidermidis in a dose-dependent manner. The coatings were successfully applied on the discs of polyether ether ketone (PEEK), a common spinal implant material and antibacterial property of these coatings was assessed via Kirby Bauer assay. More importantly, these selected coatings completely inhibited biofilm formation. The release study demonstrated that the release rate of silver from the coating depended on doping levels and also the ratios of titanium dioxide and PDMS. This result is crucial for designing coatings with desired silver release rate on PEEK materials for antimicrobial applications.

Niobium oxide-polydimethylsiloxane hybrid composite coatings for tuning primary fibroblast functions.

This study evaluates the potential of niobium oxide-polydimethylsiloxane (PDMS) composites for tuning cellular response of fibroblasts, a key cell type of soft tissue/implant interfaces. In this study, various hybrid coatings of niobium oxide and PDMS with different niobium oxide concentrations were synthesized and characterized using scanning electron microscopy, X-ray photoelectron spectrometry (XPS), and contact angle goniometry. The coatings were then applied to 96-well plates, on which primary fibroblasts were seeded. Fibroblast viability, proliferation, and morphology were assessed after 1, 2, and 3 days of incubation using WST-1 and calcein AM assays along with fluorescent microscopy. The results showed that the prepared coatings had distinct surface features with submicron spherical composites covered in a polymeric layer. The water contact angle measurement demonstrated that the hybrid surfaces were much more hydrophobic than the original pure niobium oxide and PDMS. The combination of surface roughness and chemistry resulted in a biphasic cellular response with maximum fibroblast density on substrate with 40 wt % of niobium oxide. The results of the current study indicate that by adjusting the concentration of niobium oxide in the coating, a desirable cell response can be achieved to improve tissue/implant interfaces.

Characterizing a Debris Field Using Digital Mosaicking and CAD Model Superimposition from Underwater Video

Abstract Identifying submerged objects is critical for several disciplines such as marine archaeology and search and rescue. However, identifying objects in underwater searches presents many challenges, particularly if the only data available to analyze is poor-quality video where the videographer did not plan for photogrammetric techniques to be utilized. In this paper, we discuss the use of adaptive sampling of the underwater video to extract sharp still images for stitching and analysis, and creating mosaicked images by identifying and matching local scale-invariant feature transform features using computationally efficient algorithms. Computer aided design models of suspected aircraft components were superimposed, and a feature common in multiple mosaicked images was used to identify a common feature between purported objects to assess goodness of fit. The superimposition method was replicated using landing gear from a reference aircraft and a rope of known dimensions, and favorably compared against the remotely operated vehicle (ROV) analysis results.

Identification of a putative man-made object from an underwater crash site using CAD model superimposition

In order to identify an object in video, a comparison with an exemplar object is typically needed. In this paper, we discuss the methodology used to identify an object detected in underwater video that was recorded during an investigation into Amelia Earharts purported crash site. A computer aided design (CAD) model of the suspected aircraft component was created based on measurements made from orthogonally rectified images of a reference aircraft, and validated against historical photographs of the subject aircraft prior to the crash. The CAD model was then superimposed on the underwater video, and specific features on the object were geometrically compared between the CAD model and the video. This geometrical comparison was used to assess the goodness of fit between the purported object and the object identified in the underwater video.

In vitro and in vivo studies of electron beam evaporated titanium surfaces for orthopedic applications

Achieving stable device integration is challenging in orthopedic applications, particularly for prosthetic attachment, because of the many different hard tissue interfaces. Such osseointegrated devices undergo poor hard tissue integration caused by wear, lack of proper bone formation, and infection. The challenge with nanotextured titanium is to find a surface that prevents bacterial growth, while supporting bone cell proliferation to improve hard tissue integration. This study examined the influence of nanotextured titanium, with and without patterns, created through electron beam evaporation on bone formation and integration. In vitro and in vivo data provided data that these nanotextured surfaces improved bone growth compared to their conventional, non-nanotextured titanium surfaces.