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