Fabrication and in vitro degradation of porous fumarate‐based polymer/alumoxane nanocomposite scaffolds for bone tissue engineering

Abstract

In this work, the fabrication and in vitro degradation of porous fumarate-based/alumoxane nanocomposites were evaluated for their potential as bone tissue engineering scaffolds. The biodegradable polymer poly (propylene fumarate)/propylene fumarate-diacrylate (PPF/PF-DA), a macrocomposite composed of PPF/PF-DA and boehmite microparticles, and a nanocomposite composed of PPF/PF-DA and surface-modified alumoxane nanoparticles were used to fabricate porous scaffolds by photo-crosslinking and salt-leaching. Scaffolds then underwent 12 weeks of in vitro degradation in phosphate buffered saline at 37 degrees C. The presence of boehmite microparticles and alumoxane nanoparticles in the polymer inhibited scaffold shrinkage during crosslinking. Furthermore, the incorporation of alumoxane nanoparticles into the polymer limited salt-leaching, perhaps due to tighter crosslinking within the nanocomposite. Analysis of crosslinking revealed that the acrylate and overall double bond conversions in the nanocomposite were higher than in the PPF/PF-DA polymer alone, though these differences were not significant. During 12 weeks of in vitro degradation, the nanocomposite lost 5.3% +/- 2.4% of its mass but maintained its compressive mechanical properties and porous architecture. The addition of alumoxane nanoparticles into the fumarate-based polymer did not significantly affect the degradation of the nanocomposite compared with the other materials in terms of mass loss, compressive properties, and porous structure. These results demonstrate the feasibility of fabricating degradable nanocomposite scaffolds for bone tissue engineering by photo-crosslinking and salt-leaching mixtures of fumarate-based polymers, alumoxane nanoparticles, and salt microparticles.

Biomimetic coatings for bone tissue engineering of critical-sized defects

“…Therefore, a certain degradation rate of a bone substitute is important to fulfil its function: a too rapid degradation of bone substitutes will result in the disorder of osteogenic activities and the dominance of connective tissue healing; on the other hand, a too slow degradation will hinder the replacement by natural bone. Many efforts have been made to modulate the degradation rate of bone substitutes (Sokolsky-Papkov et al 2007; Mistry et al 2009Mistry et al , 2010. As a methodology to improve the osteoconductivity of and to confer the osteoinductivity to bone substitutes, BMP-2-incorporated CaP coating furnishes the substitutes with a layer of calcium phosphate of a certain thickness and induces a series of biological activities, which can also modulate the degradation rate of biodegradable bone substitutes.…”

Controlled Hydrolytic Degradation of Polyglycolide–Caprolactone-Based Bioabsorbable Copolymer

“…It was established that end-capped absorbable fibre was more stable at pH 10.0 compared to uncapped absorbable material. End-capping also retained more tensile strength (48%) compared to uncapped filaments (36%) after 28 days [19][20][21][22][23] . Percentage of weight retention of end-capped and uncapped filaments was compared after 7 and 14 days at pH 10.0 (Figure 14).…”

Novel biological/biohybrid prostheses for the ossicular chain: fabrication feasibility and preliminary functional characterization

“…This polymer/initiator mixture was then mixed with 80% wt salt [NaCl, particle size range: 100-300μm, sieved with USA Standard Testing Sieves (Fisher Scientific, Pittsburgh, PA)] as porogen. Photo-crosslinking of the polymer/initiator/salt mixture packed into the silicon molds was then performed using an Ultralum UV light box (Paramount, CA) (Mistry et al 2008;Danti et al 2009). Furthermore, a complete crosslinking of the samples was obtained by overnight thermal treatment at 60°C.…”

“…Briefly, silicon rubber molds were prepared using partial ossicular prostheses as implant forms, while PPF and its crosslinking agent PPF-DA were synthesized following established methods (Timmer et al 2003;Mistry et al 2008). In order to assure subsequent network crosslinking of the polymer mixture, the photoinitiator bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO) (Ciba Specialty Chemicals, Tarrytown, NY) (0.5% wt), dissolved in acetone at 0.1 g/ml, was mixed together with the polymer at 0.5% wt.…”

“…As an example of a scaffold with a PORP design, poly (propylene fumarate)/poly(propylene fumarate)-diacrylate (PPF/PPF-DA) was used as biocompatible and biodegradable polymer, and osteoinduced human Mesenchymal Stromal Cells (hMSCs) were employed as a tool to pregenerate bone ECM within the scaffold porosity (Datta et al 2005;Pham et al 2008). PPF/PPF-DA is a well-known biocompatible synthetic polymer that offers specific advantages for this application, such as photo/ thermo crosslinking, shape and dimension control during its processing into a highly porous millimetric structure, rigidity for effective sound transmission, and long-term degradation in physiological conditions (Timmer et al 2003;Fisher et al 2003, Mistry et al 2008Danti et al 2009). Such scaffolds will hereafter be referred to either as "TE constructs" or "TE PORPs" or "biohybrid PORPs".…”