Covalently Grafted 2-Methacryloyloxyethyl Phosphorylcholine Networks Inhibit Fibrous Capsule Formation around Silicone Breast Implants in a Porcine Model.

The surface of human silicone breast implants is covalently grafted at a high density with a 2-methacryloyloxyethyl phosphorylcholine (MPC)-based polymer. Addition of cross-linkers is essential for enhancing the density and mechanical durability of the MPC graft. The MPC graft strongly inhibits not only adsorption but also the conformational deformation of fibrinogen, resulting in the exposure of a buried amino acid sequence, γ377-395, which is recognized by inflammatory cells. Furthermore, the numbers of adhered macrophages and the amounts of released cytokines (MIP-1α, MIP-1ß, IL-8, TNFα, IL-1α, IL-1ß, and IL-10) are dramatically decreased when the MPC network is introduced at a high density on the silicone surface (cross-linked PMPC-silicone). We insert the MPC-grafted human silicone breast implants into Yorkshire pigs to analyze the in vivo effect of the MPC graft on the capsular formation around the implants. After 6 month implantation, marked reductions of inflammatory cell recruitment, inflammatory-related proteins (TGF-ß and myeloperoxidase), a myoblast marker (α-smooth muscle actin), vascularity-related factors (blood vessels and VEGF), and, most importantly, capsular thickness are observed on the cross-linked PMPC-silicone. We propose a mechanism of the MPC grafting effect on fibrous capsular formation around silicone implants on the basis of the in vitro and in vivo results.

Alleviation of capsular formations on silicone implants in rats using biomembrane-mimicking coatings.

Despite their popular use in breast augmentation and reconstruction surgeries, the limited biocompatibility of silicone implants can induce severe side effects, including capsular contracture - an excessive foreign body reaction that forms a tight and hard fibrous capsule around the implant. This study examines the effects of using biomembrane-mimicking surface coatings to prevent capsular formations on silicone implants. The covalently attached biomembrane-mimicking polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), prevented nonspecific protein adsorption and fibroblast adhesion on the silicone surface. More importantly, in vivo capsule formations around PMPC-grafted silicone implants in rats were significantly thinner and exhibited lower collagen densities and more regular collagen alignments than bare silicone implants. The observed decrease in α-smooth muscle actin also supported the alleviation of capsular formations by the biomembrane-mimicking coating. Decreases in inflammation-related cells, myeloperoxidase and transforming growth factor-ß resulted in reduced inflammation in the capsular tissue. The biomembrane-mimicking coatings used on these silicone implants demonstrate great potential for preventing capsular contracture and developing biocompatible materials for various biomedical applications.