Material-Tissue Interfaces: The Role of Surface Properties and Processes (original) (raw)

Surface properties and processes of the biomaterial-tissue interface

Materials Science and Engineering C

At an implant site, a manmade material meets human tissue, and the manmade material is highly perturbed by the preceeding surgical procedure. The focus of the action, and thus the focus of scientific interest, is the interface between the foreign material and the tissue. The primary interaction occurs on a molecular scale, and involves adsorption and reactions of biomolecules, water and inorganic ions respectively from the bioliquid as well as dissolution of atomic, ionic or molecular fragments from the biomaterial. Successively changing conditions in the tissue, owing to the ongoing healing process and concerted modifications of the surface properties of the biomaterial, make the material-tissue interface a dynamic, non-reversible system in space and time. Secondary processes, induced by the primary processes, may occur far from the interface in the surrounding tissue or as systemic effects.

Species and Density of Implant Surface Chemistry Affect the Extent of Foreign Body Reactions

Langmuir, 2008

Implant-associated fibrotic capsule formation presents a major challenge for the development of long term drug release microspheres and implantable sensors. Since material properties have been shown to affect in vitro cellular responses and also to influence short term in vivo tissue responses, we have thus assumed that the type and density of surface chemical groups would affect the degree of tissue responses to microsphere implants. To test this hypothesis, polypropylene particles with different surface densities of -OH and -COOH groups, along with the polypropylene control (-CH 2 groups) were utilized. The influence of functional groups and their surface densities on tissue reactions were analyzed using a mice subcutaneous implantation model. Our comparative studies included determination and correlation of the extents of fibrotic capsule formation, cell infiltration into the particles and recruitment of CD11b+ inflammatory cells for all of the substrates employed. We have observed major differences among microspheres coated with different surface functionalities. Surfaces with -OH surface groups trigger the strongest responses while -COOH rich surfaces prompt the least tissue reactions. However, variation of the surface density of either functional group has a relatively minor influence on the extent of fibrotic tissue reactions. The present results show that surface functionality can be used as a powerful tool to alter implant-associated fibrotic reactions and, potentially, to improve the efficacy and function of drug delivery microspheres, implantable sensors and tissue engineering scaffolds.

Surface chemistry influences implant‐mediated host tissue responses

Journal of Biomedical Materials Research Part A, 2008

Implant-mediated fibrotic reactions are detrimental to the performance of encapsulated cells, implanted drug release devices and sensors. To improve the implant function and longevity, research has emphasized altering cellular responses. Although material surface functional groups have been shown to be potent in affecting cellular activity in vitro and short term in vivo responses, these groups appear to have little influence on long-term in vivo fibrotic reactions, possibly as a result of insufficient interactions between recruited host cells and functional groups on the implants. To maximize the influence of functionality on cells, and to mimic drug release microspheres, functionalized micron-sized particles were created and tested for their ability in modulating tissue responses to biomaterial implants. In this work, the surfaces of polypropylene particles were controllably coated with four different functional groups, specifically -OH, -NH 2 , -CF x and -COOH, using a radio frequency glow discharge plasma polymerization technique. The effect of these surface functionalities on host tissue responses were then evaluated using a mice subcutaneous implantation model. Major differences were observed in contrasting tissue response to the different chemistries. Surfaces with -OH and -NH 2 surface groups induced the thickest fibrous capsule accompanied with the greatest cellular infiltration into the implants. In contrast, surfaces with -CF x and -COOH exhibited the least inflammatory/fibrotic responses and cellular infiltrations. The present results clearly demonstrate that, by increasing the available functionalized surface area and spatial distribution, the effect of surface chemistry on tissue reactivity can be substantially enhanced.

An approach to the soft tissue/synthetic material interface

Journal of Biomedical Materials Research, 1977

It is argued that chemical modification of soft tissue implants in the hope of obtaining an associated tissue response is unlikely to succeed as a method for studying the fundamentals of implant/tissue interactions. An alternative approach is proposed which places greater emphasis on the interfacial interactions (such as protein adsorption) which occur after implantation, in a manner paralleling current advances in knowledge of the blood/material interface. From simple arguments, it is proposed that the observed similarities in soft tissue response of hydrophobic materials may result from irreversible protein adsorption, and that if unusual tissue responses are possible they are likely to be found only with hydrophilic implants. The possibility of a critical hydrophilic/hydrophobic character which an implant must possess for essentially irreversible protein adsorption is also discussed.

Surface Chemistry Influence Implant Biocompatibility

2008

Implantable medical devices are increasingly important in the practice of modern medicine. Unfortunately, almost all medical devices suffer to a different extent from adverse reactions, including inflammation, fibrosis, thrombosis and infection. To improve the safety and function of many types of medical implants, a major need exists for development of materials that evoked desired tissue responses. Because implant-associated protein adsorption and conformational changes thereafter have been shown to promote immune reactions, rigorous research efforts have been emphasized on the engineering of surface property (physical and chemical characteristics) to reduce protein adsorption and cell interactions and subsequently improve implant biocompatibility. This brief review is aimed to summarize the past efforts and our recent knowledge about the influence of surface functionality on protein:cell:biomaterial interactions. It is our belief that detailed understandings of bioactivity of surface functionality provide an easy, economic, and specific approach for the future rational design of implantable medical devices with desired tissue reactivity and, hopefully, wound healing capability.

Surface Chemistry Influences Implant Biocompatibility

Current Topics in Medicinal Chemistry, 2008

Implantable medical devices are increasingly important in the practice of modern medicine. Unfortunately, almost all medical devices suffer to a different extent from adverse reactions, including inflammation, fibrosis, thrombosis and infection. To improve the safety and function of many types of medical implants, a major need exists for development of materials that evoked desired tissue responses. Because implant-associated protein adsorption and conformational changes thereafter have been shown to promote immune reactions, rigorous research efforts have been emphasized on the engineering of surface property (physical and chemical characteristics) to reduce protein adsorption and cell interactions and subsequently improve implant biocompatibility. This brief review is aimed to summarize the past efforts and our recent knowledge about the influence of surface functionality on protein:cell:biomaterial interactions. It is our belief that detailed understandings of bioactivity of surface functionality provide an easy, economic, and specific approach for the future rational design of implantable medical devices with desired tissue reactivity and, hopefully, wound healing capability.

Biomaterials: Role of surface modifications

Bulletin of Materials Science, 1994

The fundamental concepts related to biomaterials and blood/tissue-material interactions at the interface have been reviewed. The relevance of surface modification to enhance blood and/or tissue compatibility of materials has been discussed and its role in selected prosthetic applications described.

Modern biomaterials: a review—bulk properties and implications of surface modifications

Journal of Materials Science: Materials in Medicine, 2007

This review concerns the importance of 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 this may 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.