Patterned Silicone Surfaces for Limiting Infection in Breast Prostheses
Sujee Jeyapalina, PhD, Brian T. BEnnett, MSc, Jayant Agarwal, MD.
University of Utah, SALT LAKE CITY, UT, USA.
PURPOSE: Breast prosthesis placement remains one of the most commonly performed procedures in reconstructive surgery. It is estimated that approximately 15% of breast prostheses complications are due to infection, while an additional ~35% are attributed to aggressive capsular contracture (CC) formation. Interestingly, recent publications attribute acute infection as a potential etiology for CC. Since micro-patterned surfaces have been shown to limit bacterial adhesion and biofilm formation while promoting directional adhesion of healthy cells, one option to reduce infection rates is to modify the breast prosthetic surfaces with micro-patterns. This concept is based on the "race-for-the-surface" principle—where anti-biofilm adhesive surfaces provide a protective environment for host eukaryotic cells to adhere and proliferate first. To date, no studies have been attempted to test these surfaces on breast prostheses. Thus, we hypothesized that a range of surface patterns with micro-scaled repeating units on silicone surfaces would reduce or eliminate bacterial adhesion, thereby deterring biofilm formation while allowing directional adhesion of the fibroblasts.
METHODS: To test this hypothesis, we performed in vitro and in vivo experiments. Initially, a range of micro-patterned surfaces were fabricated at the U of U Nanofabrication Core facility and the surface properties were quantified using scanning electron microscopy, protein adhesion, and wettability assays. Biofilm reactor and cell adhesion studies were then used to quantify the bacterial and fibroblast adhesion properties, respectively. Based on the data, three surfaces (3X3, 5X5 and 10X10) were tested in two in vivo studies, and a clinically-utilized smooth breast prosthesis surface was used as the control. In each in vivo study, 16 (n=4/group) female hairless IVF rats were used. During the surgery, a subcutaneous pocket was made under the right dorsal skin using blunt dissection. In each animal, a single PDMS implant was placed into this pocket. After inoculating the pocket with a known concentration of bioluminescent S. aureus (Xen 36 strain): 0.2 ml of 104 CFU (Study 1) and 0.2 ml of 1010 CFU (Study 2). The incision line was sutured and dressed, and the animals were survived to the preselected time points: Study 1 - three weeks post-surgery and Study 2 - sixteen weeks post-surgery. The implant and adjacent tissues were collected at necropsy, processed, and analyzed.
RESULTS: In Study 1, histology data (Figure 1) indicated that, while the periprosthetic tissues of the control had an increased number of foreign body giant cells, periprosthetic tissues surrounding the 3X3 patterns had increased lymphocyte activities. Periprosthetic tissues of the 5X5 and 10X10 designs showed reduced inflammation when compared to the control. The second study is ongoing. Early clinical observations revealed differences between the groups. Within the first two weeks post-surgery, 5X5 and 10X10 implant sites appeared inflamed but receded after the third week. These animals will be euthanized in early December.
CONCLUSION: Based on these early data, there could be relationship between implant surface texture and periprosthetic morphology.
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