Laser stereolithography and supercritical fluid processing for custom-designed implant fabrication

Abstract

This paper describes the laser photopolymerization of a liquid mixture of polyfunctional acrylic monomers, photoinitiator and hydroxyapatite (HA). Pure polymeric and composite materials of specific shape and structure were fabricated by laser stereolithography based on images derived from three-dimensional (3D) computer modeling. The polymeric objects then were treated with supercritical carbon dioxide to remove potentially toxic residues (monomers, low molecular weight oligomers, etc.) and to provide interconnective microporosity. Finally, samples were implanted into white rats (diastolic epiphysis of femoral bone) to study living tissue response and processes of osteointegration and osteoinduction. It was shown that incorporation of HA into the composite implant structure encouraged periosteal as well as endosteal osteogenesis and improved their osteointegrative characteristics in particular. Supercritical carbon dioxide treatment significantly enhanced the biocompatibility of the materials, increasing the area of direct contact of the implant surface with regenerated bone tissue.

Osteogenesis and angiogenesis: The potential for engineering bone

“…Synthetic polymer matrices, polylactic acid (PLA) polyglycolic acid (PGA and poly(lactic-co-glycolic) (PLGA) acid polyorthoesters, polycaprolactones, polycarbonates, and polyfumerates which are free of potential contamination, can be readily engineered (Agrawal and Ray, 2001;Sachlos and Czernuszka, 2003). These have proven versatility and can be developed as 3D porous monolithic structures that can be custom-designed to fit the anatomical bone defect in an individual patient (Popov et al, 2004;Antonov et al, 2005). However, one of the major problems with these types of scaffolds is the lack of osteoconductivity compared to the current gold standard of allograft.…”

“…However, one of the major problems with these types of scaffolds is the lack of osteoconductivity compared to the current gold standard of allograft. Researchers have tried to overcome these problems by combining ceramics such as hydroxyapaptite (HA) and calcium phosphate with the synthetic polymers PLA or PLGA (Popov et al, 2004;Khan et al, 2004;Wei and Ma, 2004;Ruhe et al, 2005a). With the fabrication of the osteoconductive/osteoinductive scaffolds, novel approaches are being developed to enhance the engineered scaffolds by the addition of growth factors and osteoprogenitor cells to promote bone growth.…”

Stereolithographic Bone Scaffold Design Parameters: Osteogenic Differentiation and Signal Expression

“…25 Further, HA could be used in composite fabrication with photocurable acrylate resins. 120,121 In these studies, micrometer-sized HA particles were incorporated with olygocarbonate dimethacrylate resin material, and simple stirring created homogenous mixture of HA particles and resin polymers, which blocked the inhibition of photocrosslinking by solid particles. Although increasing the amount of HA particles might limit the versatility of SLA fabrication because of increased viscosity, the result of 4-and 8-week in vivo studies on distal epiphysis implants in rat femora exhibited extensive periosteal and endosteal osteogenesis, as observed by scanning electron microscopy of sectioned tissue samples.…”

Solid Free-form Fabrication Technology and Its Application to Bone Tissue Engineering

“…They fabricated HA structures that were the same shapes as parts of human ear ossicles. Popov et al also attempted the fabrication of scaffolds and prostheses using a commercial photocurable photopolymer with lower cytotoxicity (27).…”