Surface chemistry influences implant‐mediated host tissue responses

Abstract

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, -NH2, -CFx 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 –NH2 surface groups induced the thickest fibrous capsule accompanied with the greatest cellular infiltration into the implants. In contrast, surfaces with –CFx 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.

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

“…Consistent with our previous study, 55 the fibrous capsule around the implants varied significantly among the three different functional groups represented. In general, the particles containing the -OH groups exhibited the thickest capsule formation, followed by the polypropylene control particles, which consist predominately of the -CH 2 functionality.…”

“…In fact, our studies have found that surface functionality has significant influence on inflammatory cell accumulation (or inflammatory responses), but limited effect on fibrotic tissue reactions. 42,43,55 To test this hypothesis, it is essential to increase the interactions between functional groups and cells by increasing the surface area and/or density of functional groups. Spherical particles were chosen for this purpose to maximize the surface to volume ratio of the implants and also to mimic drug release particles and highly porous tissue scaffolds.…”

Progress technology in microencapsulation methods for cell therapy

“…81,183 Since then, a lot of effort has been directed towards improving the purification of polymers, the standardization of methods and better fundamental understanding of the biocompatibility of capsules and interactions with host soft tissues. 184,185 Nevertheless, the in vivo stability of electrostatic and hydrogen bonds maintaining the structure of microcapsules is limited, and the mechanical resistance of capsules is still a concern. Liquidcore/shell microcapsules generally seem to allow better cell growth and protein production, although their mechanical resistance is further diminished compared to matrix-core capsules.…”

rFN/Cad-11-Modified Collagen Type II Biomimetic Interface Promotes the Adhesion and Chondrogenic Differentiation of Mesenchymal Stem Cells

“…After anesthesia, rabbit bone marrow was collected into a 10-mL syringe that contained 5000 U of heparin. The marrow was resuspended in a 0.84% NH 4 Cl solution. After 5 min, approximately 2.0 · 10 6 marrow cells were plated in a 25-cm 2 plastic flask in Dulbecco's modified Eagle medium (DMEM), which was supplemented with 10% fetal bovine serum (FBS; Hyclone Laboratories), 2 mM l-glutamine, 100 U/mL penicillin, and 0.1 mg/mL streptomycin.…”

“…These factors include the roughness of the material interface, hydrophilicity, stress distribution, surface charge distribution, the density and strength of biological ligands, and the local microstructure. 4,5 The biology of chondrocytes is highly influenced by their interactions with specific extracellular matrix (ECM) molecules. 6 In recent years, the principle of surface modification has been utilized to mimic the interaction between ECM proteins and their surrounding cells.…”