# Advances in Biomaterials for Breast Reconstruction
### Modification of Implant Surface Topography  
A silicone gel implant with a smooth surface was the earliest form and is still being used today. However, the frequency of its use is decreasing because of the relatively high capsular contracture rate. According to previous studies, the rate of capsular contracture is higher for smooth implants than for textured surface implants [32; 33; 34; 35]. Manufacturers presented breast implants with a textured surface to overcome the high capsular contracture rate of implants with a smooth surface [36; 37]. Initial textured implants were made with a polyurethane coating, developed in the 1970s [38]. Studies indicated that a polyurethane foam-coated silicone gel implant might reduce capsular contracture [39; 40]. After capsular formation around the implant, the 1.5 to 2.0 mm-thick polyurethane coating disintegrated, and it was hypothesized that the tightening that occurred would prevent the alignment of myofibists and eventually interrupt the capsular contracture process [41]. The use of polyurethane implants has spread worldwide since they were introduced. However, as polyurethane foam degraded, it was found to release carcinogenic 2_A_-toluene diamine (TDA). This subsequently led to complete prohibition by the FDA in 1991, and this implant was removed from the market. Later, it was revealed that the small amount of 2,4-TDA released would not significantly increase risk [42]. The surgical use of the polyurethane-coated implant continued in countries other than the US. The safety and effectiveness of reducing the capsular contracture rate have been reported on by multiple authors [43; 44; 45]. As polyurethane foam-covered silicone gel implants are not as biocompatible as silicone, textured implants have been introduced to inhibit capsule formation. Through the \"adhesive effect\" of the pores on the surface of the textured implant, the stabilization and fixing of the implant in the breast pocket could be achieved. In addition, a textured silicone implant causes less fibrosis, and, as a result, the frequency of capsular contracture is lower than that of a smooth implant [35; 46; 47]. Still, many textured implants are associated with a significant rate of capsular contracture, and texturization during manufacture has been associated with a collection of serous fluid that develops under the surface in the body (seroma) and double capsule formation. For the next generation of implants, micro- or nanotextured implants were developed by controlling the roughness of the existing surface. The rough surface may induce bacterial colonization by providing space for bacteria and more points of direct contact between the pathogenic cell and the implant surface (Figure 2) [48]. By avoiding aggressive texturing with the projection of sugar crystals and salt onto the implant, reduced roughness has promoted a more natural interaction between the implant and soft tissue, potentially reducing inflammation. For example, Sientra's Silimed has a web-like organization at the implant's surface, and Allergan Biocell has a salt-loss pattern on the surface. However, the microtextured implant, such as Mentor Siltex, is manufactured using a pressure imprint-stamping technique (Figure 3A-C) [49]. One of the nanotextured implants, Motiva Silksurface, is manufactured using negative imprinting with three-dimensional (3D) technology. It optimizes biocompatibility by structuring a uniform topography using 3D imprinting on polydimethylsiloxane (PDMS) material to build the outer shell (Figure 3D) [50]. These changes to the surface have minimized inflammation and, in turn, reduced breast implant-related complications such as capsular contracture and late seromas. Moreover, a higher number of contact points could prevent the aggregation of fibroblasts, which might lead to capsular contracture. In addition to surface structural modification, modifications using biomaterials are also in progress to minimize capsular contracture.