Salient Degradation Features of a 50:50 PLA/PGA Scaffold for Tissue Engineering

Abstract

An implant system that undergoes a gradual, time-dependent, nontoxic degradation process may offer an efficacious, safe, and desirable alternative to metallic materials used in the treatment of various musculoskeletal conditions. Such a scaffold may also be a suitable vehicle for growing cells and tissue in the laboratory for tissue engineering applications. We have used a scaffold of this type previously in animal studies for biological resurfacing of large articular cartilage defects.(1) This study examined important in vitro degradation characteristics of a 50:50 polylactic acid/polyglycolic acid (PLG) implant during an 8-week period. It was determined that this particular implant degraded in a biphasic fashion. The initial phase occurred during the first 2 weeks with a decrease in molecular weight and surface axial strain, coupled with an increase in percent porosity. The second phase demonstrated a decline in surface axial strain by 4 weeks and an ongoing decline in molecular weight. Loss of gross structural properties was not evident until the start of the second phase and was complete at 8 weeks. This study demonstrated the potential uses for this implant as a means of providing structural support for cells and tissue ingrowth for up to 8 weeks. Further studies need to be conducted in order to determine the biological effects of the degrading polymer byproducts on host tissues.

A sandwich model for engineering cartilage with acellular cartilage sheets and chondrocytes

“…The degradation of the scaffold should not be so fast that cells do not have enough time to proliferate and secrete the new matrix. In addition, it should not reside in the newly-formed tissue after its formation or interfere with the formation process, which can be very difficult to control with synthetic materials [25,26]. However, this is not a problem for acellular matrix, as the natural components in the scaffold contribute to the new tissue formation process.…”

Diffusion in Musculoskeletal Tissue Engineering Scaffolds: Design Issues Related to Porosity, Permeability, Architecture, and Nutrient Mixing

“…3 Porosity values may also be derived from scanning electron microscopy of cross-sections of scaffolds. 10,11,39,42,51,73,98,102,113,126 Two-dimensional images and image analysis can yield the pore to polymer area, which is then extrapolated to 3D to obtain estimates of porosity.…”

Controlled preparation and properties of porous poly(l-lactide) obtained from a co-continuous blend of two biodegradable polymers

“…Solution casting (dissolution/precipitation): 40-50%-porous, 5-15 mm-pore size [38,39] Use of solvents Generally limited to thin components, films or coating applications, practically no porosity at the surface Low mechanical strength PLLA films from polymer blends/extraction of one of the phases [40] Water extraction of PEO Use of solvents Possibility to vary pore size between 0.1 and 1000 mm PLLA/low-molecular weight additives mixture [41] 2-300 mm Use of solvents…”