Modern biomaterials: a review—bulk properties and implications of surface modiﬁcations
Paul Roach Æ David Eglin Æ Kirsty Rohde Æ Carole C. Perry
Received: 1 February 2006 / Accepted: 8 May 2006 / Published online: 19 April 2007 Ó Springer Science+Business Media, LLC 2007
Abstract This review concerns the importanceof length and time on physicochemical interactions between living tissue and biomaterials that occur on implantation. The review provides information on material host interactions, materials for medical applications and cell surface interactions, and then details the extent of knowledge concerning the role(s) that surface chemistry and topography play during the ﬁrst stage of implant integration,namely protein adsorption. The key points are illustrated by data from model in vitro studies. Host implant interactions begin nanoseconds after ﬁrst contact and from then on are in a state of ﬂux due to protein adsorption, cell adhesion and physical and chemical alteration of the implanted material. The many questions concerning the conformational form and control of bound proteins and how thismay impact on cell adhesion in the ﬁrst instance and later on cell signalling and implant integration can be answered by systematic investigations using model materials. Only then we will be in a more informed position to design new materials for use in the body. Keywords Biomaterials Á Cell–surface interactions Á Protein–surface interactions Á Topography Á Implantation Á PhysicochemicalIntroduction This review highlights the importance/development of physicochemical interactions between living tissue and a biomaterial upon implantation. Of utmost importance are the length scales of the species involved and the time for speciﬁc interactions to occur. The bioactive nature of a material describes its positive effect or interaction with living tissue. A more precise deﬁnition for aspeciﬁc material may include terms such as osteoconduction or osteopromotion, with the latter describing the directed growth of bone due to the presence of a speciﬁc material. Recent advances in the study of bioactive and biodegradable poly(a-hydroxyacids) composite materials are presented to illustrate the occurrence of macroscopic interactions between materials and living tissue. Then, the latestdevelopments in the understanding of surface chemistry and topography at both the micron and nanoscopic scale on cell and extracellular protein matrix interactions are reported. The bulk of a biomaterial presents physical and chemical properties of the material that remain during the lifetime of the implant. They can be altered to allow the biomaterial to mimic the physicochemical properties of tissueswhich they are meant to augment or replace. Advances in materials design have resulted in the development of products such as degradable sutures that naturally decompose after fulﬁlling their function. Importantly, the speciﬁc nature of a biomaterial surface both chemically and physically determines how the living host tissue and/or organism interacts with the implant. On a linear time scale, inthe early stages of implantation (nanoseconds to minutes) protein adsorption takes place, which is affected by the chemical nature of the adsorption environment and nanoscale topographical features. Surface-bound proteins
P. Roach Á D. Eglin Á K. Rohde Á C. C. Perry (&) Division of Chemistry, Interdisciplinary Biomedical Research Centre, School of Biomedical and Natural Sciences, NottinghamTrent University, Clifton, Nottingham, UK e-mail: Carole.Perry@ntu.ac.uk
J Mater Sci: Mater Med (2007) 18:1263–1277
may then mediate cell attachment during the next stage of implant assimilation (hours to days) if they have the correct orientation and conformation to interact with cell receptors. In this way, the effects of surface chemistry are conveyed through the adsorbed...