Evaluation of the potential of starch-based biodegradable polymers in the activation of human inflammatory cells

Scaffolds for tissue engineering and 3D cell culture

In tissue engineering applications or even in 3D cell cultures, the biological cross talk between cells and the scaffold is controlled by the material properties and scaffold characteristics. In order to induce cell adhesion, proliferation, and activation, materials used for the fabrication of scaffolds must possess requirements such as intrinsic biocompatibility and proper chemistry to induce molecular biorecognition from cells. Materials, scaffold mechanical properties and degradation kinetics should be adapted to the specific tissue engineering application to guarantee the required mechanical functions and to accomplish the rate of the new-tissue formation. For scaffolds, pore distribution, exposed surface area, and porosity play a major role, whose amount and distribution influence the penetration and the rate of penetration of cells within the scaffold volume, the architecture of the produced extracellular matrix, and for tissue engineering applications, the final effectiveness of the regenerative process. Depending on the fabrication process, scaffolds with different architecture can be obtained, with random or tailored pore distribution. In the recent years, rapid prototyping computer-controlled techniques have been applied to the fabrication of scaffolds with ordered geometry. This chapter reviews the principal polymeric materials that are used for the fabrication of scaffolds and the scaffold fabrication processes, with examples of properties and selected applications.

Influence of porosity and fibre diameter on the degradation of chitosan fibre-mesh scaffolds and cell adhesion

The state of the art approaches for tailoring the degradation of chitosan scaffolds are based on altering the chemical structure of the polymer. Nevertheless, such alterations may lead to changes in other properties of scaffolds, such as the ability to promote cell adhesion. The aim of this study was to investigate the influence of physical parameters such as porosity and fibre diameter on the degradation of chitosan fibre-mesh scaffolds, as a possible way of tailoring the degradation of such scaffolds. Four sets of scaffolds with distinct fibre diameter and porosity were produced and their response to degradation and cell adhesion was studied. The degradation study was carried out at 37degrees C in a lysozyme solution for five weeks. The extent of degradation was expressed as percentage of weight loss of the dried scaffolds after lysozyme treatment. Cell adhesion was assessed by Confocal Microscopy. The results have shown that the scaffolds with higher porosity degrade faster and that, within the same range of porosity, the fibres with smaller diameter degrade slightly faster. Furthermore, the morphological differences between the scaffolds did not affect the degree of cell adhesion, and the cells were observed throughout the thickness of all four types of scaffolds.

The effect of starch-based biomaterials on leukocyte adhesion and activation in vitro

Leukocyte adhesion to biomaterials has long been recognised as a key element to determine their inflammatory potential. Results regarding leukocyte adhesion and activation are contradictory in some aspects of the material's effect in determining these events. It is clear that together with the wettability or hydrophilicity/hydrophobicity, the roughness of a substrate has a major effect on leukocyte adhesion. Both the chemical and physical properties of a material influence the adsorbed proteins layer which in turn determines the adhesion of cells. In this work polymorphonuclear (PMN) cells and a mixed population of monocytes/macrophages and lymphocytes (mononuclear cells) were cultured separately with a range of starch-based materials and composites with hydroxyapatite (HA). A combination of both reflected light microscopy and scanning electron microscopy (SEM) was used in order to study the leukocyte morphology. The quantification of the enzyme lactate dehydrogenase (LDH) was used to determine the number of viable cells adhered to the polymers. Cell adhesion and activation was characterised by immunocytochemistry based on the expression of several adhesion molecules, crucial in the progress of an inflammatory response. This work supports previous in vitro studies with PMN and monocytes/macrophages, which demonstrated that there are several properties of the materials that can influence and determine their biological response. From our study, monocytes/macrophages and lymphocytes adhere in similar amounts to more hydrophobic (SPCL) and to moderately hydrophilic (SEVA-C) surfaces and do not preferentially adhere to rougher substrates (SCA). Contrarily, more hydrophilic surfaces (SCA) induced higher PMN adhesion and lower activation. In addition, the hydroxyapatite reinforcement induces changes in cell behaviour for some materials but not for others. The observed response to starch-based biodegradable polymers was not significantly different from the control materials. Thus, the results reported herein indicate the low potential of the starch-based biodegradable polymers to induce inflammation especially the HA reinforced composite materials.