Degradable Segmented Polyurethane Elastomers for Bone Tissue Engineering: Effect of Polycaprolactone Content

Abstract

Segmented polyurethanes (PURs) – consisting of degradable poly(α-hydroxy ester) soft segments and amino acid-derived chain extenders – are biocompatible elastomers with tunable mechanical and degradative properties suitable for a variety of tissue engineering applications. In this study, a family of linear PURs synthesized from poly(ε-caprolactone) (PCL) diol, 1,4-diisocyanobutane and tyramine with theoretical PCL contents of 65 to 80 wt% were processed into porous foam scaffolds and evaluated for their ability to support osteoblastic differentiation in vitro. Differential scanning calorimetry and mechanical testing of the foams indicated increasing polymer crystallinity and compressive modulus with increasing PCL content. Next, bone marrow stromal cells (BMSCs) were seeded into PUR scaffolds – as well as poly(lactic-co-glycolic acid) (PLGA) scaffolds – and maintained under osteogenic conditions for 14 and 21 days. Analysis of cell number indicated a systematic decrease in cell density with increasing PUR stiffness at both 14 and 21 days in culture. However, at these same time points the relative mRNA expression for the bone-specific proteins osteocalcin and the growth factors bone morphogenetic protein-2 and vascular endothelial growth factor gene expression were similar among the PURs. Finally, prostaglandin E2 production, alkaline phosphatase activity, and osteopontin mRNA expression were highly elevated on the most-crystalline PUR scaffold as compared to the PLGA and PUR scaffolds. These results suggest that both the modulus and crystallinity of the PUR scaffolds influence cell proliferation and the expression of osteoblastic proteins.

Porosity and swelling properties of novel polyurethane–ascorbic acid scaffolds prepared by different procedures for potential use in bone tissue engineering

“…Bioresorbable PU scaffolds have recently gained attention for their potential use in bone and cartilage engineering. 7,8 A growing body of literature investigating the engineering of bone tissues has proposed the use of porous scaffolds made of bioresorbable PU synthesized from different components. 9 In Table 1, the examples of different PU systems used for scaffolds fabrication are shown.…”

A review on microwell and microfluidic geometric array fabrication techniques and its potential applications in cellular studies

“…• Good compatibility with cells and soft tissues • Excellent mechanical properties and can be cross linked as soft elastomers or rigid materials • Biodegradable • Better control over the structure • Promote cell adhesion Good for 3D shape of the cells by using microcontact printing, poly urethane square microwells preserve the 3D morphology of cells Ochsner et al [82] Broderick et al [103] Kavlock et al [104] Polystyrene Nguyen et al [105] Nam et al [106] Sugimura et al [107] (Continues) ratios facilitate long-term cell culture. [86] Additionally, traditional microwell geometries consisting of flat bases with vertical and cylindrical walls have been utilized in the formation of multiple cell aggregates, [87] but they tend to be better suited for simple biological analysis.…”

Epithelial machines of morphogenesis and their potential application in organ assembly and tissue engineering

“…One of the most common strategies has utilized cell-populated scaffold constructs for the repair of damaged tissues. Designing the optimal scaffold has been major focus of this strategy resulting in advanced applications of synthetic foams based on PLLA (Poly(L-lactic acid)) and PLGA (Poly(l-lactide-co-glycolide)) (Wright et al 2010; Kavlock et al 2012), PMMA (Polymethylmethacrylate) (Xing et al 2012), PEG (Poly(ethylene glycol)) (Chiu et al 2011) and PTFE (polytetrafluoroethylene) (Bax et al 2011) and optimization of these polymers for cell viability and proliferation. Fabrication techniques such as freeze drying (Ohya et al 2004), solvent evaporation (Devin et al 1996) and electrospinning (Zeng et al 2005) among others are routinely used to produce scaffolds with the necessary porosity and mechanical strength to allow degradation, cell attachment, and the binding of survival and growth factors.…”