Engineering a titanium and polycaprolactone construct for a biocompatible interface between the body and artificial limb.

Intraosseous transcutaneous amputation prostheses may be able to overcome the problems that stem from the nonuniform distribution of pressure seen in the conventional stump-socket prosthetic replacement devices. Transcutaneous devices have had limited success in amputees. By optimizing the attachment of the skin to the prosthetic, intraosseous transcutaneous amputation prostheses may become clinically viable options. This report details studies evaluating the development of a modified titanium construct with a specially machined surface to increase the adherence of tissue as well as scaffold. A computer-aided biology tool was used to fabricate polycaprolactone (PCL) scaffolds with a specific three-dimensional architecture. To extrude the PCL, it was dissolved in acetic acid to produce a 70% PCL liquid. A scaffold with a porosity of >50% was fabricated to have a tensile strength similar to skin. The presence of a specially machined surface greatly increased the adhesion of the PCL scaffold to the titanium constructs. When the 70% PCL was properly neutralized by heating at 55 degrees C and washing in 90% ethanol (EtOH), there was only a decrease (10%) in the viability of cells seeded onto the PCL constructs when compared with the cells in culture. The antibacterial properties of titanium dioxide anatase, silver nanoparticles, and chlorhexidine diacetate mixed in either type I collagen or hyaluronic acid (HA) were assessed. The addition of 1% (w/w) chlorhexidine diacetate in HA resulted in a 71% decrease in bacteria seen in nontreated HA. These results show promise in developing a novel engineered titanium and PCL construct that promotes effective adhesion between the titanium-skin interface.

Engineered cellular response to scaffold architecture in a rabbit trephine defect.

Tight control of pore architecture in porous scaffolds for bone repair is critical for a fully elucidated tissue response. Solid freeform fabrication (SFF) enables construction of scaffolds with tightly controlled pore architecture. Four types of porous scaffolds were constructed using SFF and evaluated in an 8-mm rabbit trephine defect at 8 and 16 weeks (n = 6): a lactide/glycolide (50:50) copolymer scaffold with 20% w/w tri-calcium phosphate and random porous architecture (Group 1); another identical design made from poly(desaminotyrosyl-tyrosine ethyl ester carbonate) [poly(DTE carbonate)], a tyrosine-derived pseudo-polyamino acid (Group 2); and two poly(DTE carbonate) scaffolds containing 500 microm pores separated by 500-microm thick walls, one type with solid walls (Group 3), and one type with microporous walls (Group 4). A commercially available coralline scaffold (Interpore) with a 486-microm average pore size and empty defects were used as controls. There was no significant difference in the overall amount of bone ingrowth in any of the devices, as found by radiographic analysis, but patterns of bone formation matched the morphology of the scaffold. These results suggest that controlled scaffold architecture can be superimposed on biomaterial composition to design and construct scaffolds with improved fill time.

Performance of degradable composite bone repair products made via three-dimensional fabrication techniques.

This study analyzed the in vivo performance of composite degradable bone repair products fabricated using the TheriForm process, a solid freeform fabrication (SFF) technique, in a rabbit calvarial defect model at 8 weeks. Scaffolds were composed of polylactic-co-glycolic acid (PLGA) polymer with 20% w/w beta-tricalcium phosphate (beta-TCP) ceramic with engineered macroscopic channels, a controlled porosity gradient, and a controlled pore size for promotion of new bone ingrowth. Scaffolds with engineered macroscopic channels and a porosity gradient had higher percentages of new bone area compared to scaffolds without engineered channels. These scaffolds also had higher percentages of new bone area compared to unfilled control defects, suggesting that scaffold material and design combinations could be tailored to facilitate filling of bony defects. This proof-of-concept study demonstrated that channel size, porosity, and pore size can be controlled and used to influence new bone formation and calvarial defect healing.