The evaluation of biological host response to implanted materials permits the determination of the safety and biocompatibility of biomedical devices, prostheses and biomaterials. Once a biomaterial is introduced into the body to a corresponding implant site, a sequence of events occurs promoting the activation of inflammatory mediators such as leukocytes and the release of signaling molecules such as cytokines and growth factors, evoking an inflammatory and wound healing process. This review examines the cellular and molecular mechanisms involved in the foreign body reaction, especially how cytokines impact the overall inflammatory response to devices. It also reviews how these events can be modulated by the physical and chemical properties of the biomaterials such as wettability, chemistry and geometry of surface. Particular attention is dedicated to the cardiovascular field, where the use of synthetic polymers has several limitations such as thrombogenicity and risk of infection. New materials and strategies to improve biomaterial characteristics are discussed. Copyright © 2012 John Wiley & Sons, Ltd.

The molecular complexity of the processes which lead to cell adhesion includes membrane and cytoskeletal proteins, involved in the focal adhesion formation, as well as signaling molecules tightly associated with the main intracellular regulatory cascades (Akt/PKB and MAPK/Erk). Dynamic environments, which create substrate deformations at determined frequencies and timing, have significant influences on adhesion mechanisms and in general in cellular behavior. In this work, we investigated the role of mechanical stretching (10% substrate deformation, 1 Hz frequency applied up to 60  min) on adhesion proteins (vinculin and focal adhesion kinase-FAK), related RhoGTPases (Rac1 and RhoA), and intracellular pathways (Akt/PKB and MAPK/Erk) in terms of activation and membrane recruitment in relation with cytoskeletal changes observed (membrane ruffling and filopodia formation). These changes are due to intracellular molecular rearrangements, acting with sequential concerted dynamics, able to modify the cytoskeletal conformation. The observed cellular response adds some important issues for better understanding the cellular behavior in environment which mimic as close as possible the physiological conditions.

The interactions between the surface of synthetic scaffolds and cells play an important role in tissue engineering applications. To improve these interactions, two strategies are generally followed: surface coating with large proteins and surface grafting with small peptides. The proteins and peptides more often used and derived from the extracellular matrix, are fibronectin, laminin, and their active peptides, RGD and SIKVAV, respectively. The aim of this work was to compare the effects of coating and grafting of poly(L-lactide) (PLLA) films on MRC5 fibroblast cells. Grafting reactions were verified by X-ray photoelectron spectroscopy. Cell adhesion and proliferation on coated and grafted PLLA surfaces were measured by cell counting. Vinculin localization and distribution were performed on cell cultured on PLLA samples using a fluorescence microscopy technique. Finally, western blot was performed to compare signals of cell adhesion proteins, such as vinculin, Rac1, and RhoA, as well as cell proliferation, such as PCNA. These tests showed similar results for fibronectin and laminin coated PLLA, while RGD grafting is more effective compared with SIKVAV grafting. Considering the overall view of these results, although coating and grafting can both be regarded as effective methods for surface modification to enhance cell adhesion and proliferation on a biomaterial, RGD grafted PLLA show better cell adhesion and proliferation than coated PLLA, while SIKVAV grafted PLLA show similar adhesion but worse proliferation. These data verified different biological effects depending on the surface modification method used.

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Because of their suitable bio-mechanical properties, polymeric materials, such as Poly(L-lactic acid) (PLLA), and poly (lactic-co-glycolic acid) (PLGA), are often used in the biomedical field, in particular for cardiovascular applications. Implanted materials induce several events related to the inflammatory reaction, such as macrophage adhesion and activation with following cytokine release. This work considered the effect of macrophage adhesion and related cytokine release on endothelial cells (PAOEC) proliferation and migration. Slight differences have been shown by the macrophages reaction when in contact with PLLA, PLGA, or PLLA/PLGA blend. However, these differences showed to differently enhance endothelial cells behavior in terms of wound healing. These data suggest the inflammatory reaction as a useful way to consider concerning materials biocompatibility, in order to optimize the endothelial regeneration following vascular prosthetic implants.