Supercritical CO2 fluid-foaming of polymers to increase porosity: A method to improve the mechanical and biocompatibility characteristics for use as a potential alternative to allografts in impaction bone grafting?

A comparison of polymer and polymer–hydroxyapatite composite tissue engineered scaffolds for use in bone regeneration. An in vitro and in vivo study

“…The WST‐1 assay acts as a standard quantitative measure of total cell activity, and is closely related to total viable cell number . We have previously shown the excellent biocompatibility of these particular polymers, and thus the absence of any significant difference observed between the samples after the incubation period was expected …”

“…Preceding work identified high‐molecular weight polylactic acid (PLA) and high‐molecular weight poly(lactic‐ co ‐glycolic) acid (PLGA) as possible materials for use as tissue engineered living composite alternatives to allograft for use in impaction bone grafting (IBG), given their enhanced resistance to shear forces (the most common cause of allograft failure in IBG), and ability to support the survival and proliferation of skeletal stem cells (SSC) . Subsequent in vitro studies have shown that a porous version of the same polymers, produced via supercritical CO 2 foaming, enhanced both cellular compatibility and osteoblastic differentiation, while maintaining superior composite shear characteristics in comparison with allograft …”

“…14 Subsequent in vitro studies have shown that a porous version of the same polymers, produced via supercritical CO 2 foaming, enhanced both cellular compatibility and osteoblastic differentiation, while maintaining superior composite shear characteristics in comparison with allograft. 15 This study set out to examine these previously identified porous polymers with the incorporation of HA, to assess whether this further enhanced their biological and mechanical characteristics for use in IBG. A second stage of the study selected the best two in vitro performing polymers and examined the polymers in an in vivo (murine) environment, such that a single optimal polymer could be selected for future scale up and potential clinical translation.…”

The influence of supercritical foaming conditions on properties of polymer scaffolds for tissue engineering

“…The polymer foaming process with the use of supercritical fluids is an alternative to traditional methods of production of functional porous structures, carried out with the application of environmentally cpe.czasopisma.pan.pl; degruyter.com/view/j/cpe harmful, volatile organic solvents, which may also lead to a reduction in the activity of processed biodegradable polymers (Gualandi et al, 2010;Tayton et al, 2012). The exercitation of a safe medium such as supercritical carbon dioxide in the process allows to eliminate the above mentioned disadvantages.…”

The scale-up of a tissue engineered porous hydroxyapatite polymer composite scaffold for use in bone repair: An ovine femoral condyle defect study

“…Previous in vitro and small animal in vivo studies highlighted a composite polymer hydroxyapatite scaffold in combination with SSCs for potential use as a tissue engineered bone graft substitute. Scaffold characterization via microCT and scanning electron microscopy (mean porosity 63.4 ± 5.4%, pore size 192 ± 51 μm), cellular viability studies and shear testing found high molecular weight porous poly ( dl ‐lactic acid) hydroxyapatite (P DL LA + 10% HA) composite to display both the mechanical, osteogenic capabilities and tissue compatibility required for clinical use . The use of large animal models is essential when investigating bone regenerative strategies, circumventing issues of translation, scale, nutrient requirements, and lack of relevance of skeletal form and forces present in small animal models .…”