Polymer concepts in tissue engineering

Abstract

Traumatic injuries, cancer treatment, and congenital abnormalities are often associated with abnormal bone shape or segmental bone loss. Restoration of normal structure and function in these cases requires replacement of the missing bone that may be accomplished by surgical transfer of natural tissue from an uninjured location elsewhere in the body. However, this procedure is limited by availability, adequate blood supply, and secondary deformities at the donor site. One strategy to overcome these problems is to develop living tissue substitutes based on synthetic biodegradable polymers. Three methods of bone regeneration using biodegradable polymers are being studied in our laboratory: tissue induction, cell transplantation, and fabrication of vascularized bone flaps. Injectable polymers are used for filling skeletal defects and guiding bone tissue growth. Their main advantage is minimizing the surgical intervention or the severity of the surgery. Polymer-cell constructs also hold great promise in the field of tissue engineering. They provide a scaffold on which cells grow and organize themselves. As the cells begin to secrete their own extracellular matrix, the polymer degrades and is eventually eliminated from the body, resulting in completely natural tissue replacement. Bone flaps can be fabricated ectopically into precise shapes and sizes. With an attached vascular supply, these flaps can be transferred into areas deficient in vascularity. This article discusses polymer concepts regarding bone tissue engineering and reviews recent advances of our laboratory on guided bone regeneration using biodegradable polymer scaffolds.

Scaffolds and cells for tissue regeneration: different scaffold pore sizes—different cell effects

“…Microporous polycaprolactone (PCL) matrice with various pore sizes might be used to stimulate osteogenesis by delivery of various protein such as lysozyme (100-200 lm), collagenases (80-200 lm), catalase (100-250 lm), lactose (45-90, 90-125 lm) and gelatin (125-250 lm) into damaged tissue (Wang et al , 2009). Correspondingly, osteoblasts proliferation and bone formation on the PLGA scaffold was the best with the poresize ranging from 150 to 300 lm (Peter et al 1998). Parallelly, it was shown that PLGA scaffolds with pore size ranging from 150 to 710 lm had no impact on the osteoblasts attachment and proliferation, whereas tissue mineralization was the best on the scaffolds with 300-500 lm pores (Ishaug et al 1997).…”

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

“…However, there are studies that argue that smaller pore sizes may be adequate for bone growth 45 and that pore sizes in the 150-710 µm range do not have any significant effect on osteoblast behavior. 43,44,75 Although results vary, an important underlying trend is the need for scaffolds to have a high porosity.…”

Fabrication and characterization of six electrospun poly(α-hydroxy ester)-based fibrous scaffolds for tissue engineering applications

“…Since non-biodegradable polymers would interfere with tissue turnover and remodeling, the current trend is to use biodegradable polymers in tissue engineering, although the non-biodegradable polymers have the advantage that their properties, both chemical and mechanical, are less aVected by the cellular and tissue milieu. On the other hand, polymer biodegradation via the combined eVect of enzymatic and hydrolytic activities generates space within the scaVold to allow for cell proliferation and the deposition of newly synthesized ECM [3]. Ideally, optimal tissue regeneration occurs upon complete biodegradation of the polymeric matrix followed by restoration of biological functions.…”