Biomechanics of breast tissues towards the design of a novel biomimetic scaffold for tissue regeneration

Introduction Breast cancer remains a pressing global health issue, despite the remarkable progress in medical technology and knowledge. Mastectomy, the surgical removal of breast tissue, often becomes an integral part of breast cancer treatment , usually followed by breast reconstruction using commercial breast implants . However, these procedures are not without their risks and complications, as capsular contracture , the most prevalent with an incidence rate ranging between 2.8% and 20.4% [ 1]. To address the limitations of current commercial breast prostheses, researchers are exploring innovative solutions such as scaffolds based on metamaterial structures, to tune their mechanical behavior and guide cellular interactions and tissue reformation [2]. Within this context, the mechanical behavior of breast tissues has a pivotal role in order to design suitable structures and choose the optimal biocompatible material, as well as to correctly stimulate the cell environment to proliferate . This being the case, this study presents an experimental investigation of the viscoelastic characteristics inherent in breast tissues. The aim is to discern a suitable scaffold capable of replicating the properties of these tissues and to provide insights for the development of structures for the optimal stimulation of surrounding cells. Methods Experimental characterization involved adipose and fibroglandular tissues that were harvested from a fresh- frozen human donor ( 85 y/o), with reference to anatomical landmarks. Then, samples were tested with a Model Mach-1 (Biomomentum©) following different protocols: unconfined compression with stress relaxation (5 ramps, 10% strain, 50%/s strain rate, 300s resting time) and loading-unloading cycles (1%/s, 10%/s and 100%/s) . Viscoelastic parameters and equilibrium stress-strain curves were extracted. In parallel, v arious scaffold geometries were investigated by means of finite element models , from beam-based to shell -based architectures (Figure 1 c), aimed to mimic the structure of the adipose and glandular tissues. Results In literature, the mechanical properties of the native breast are not extensively reported, or assumed to be linear elastic [3]. Experimental tests strongly highlighted the non -linear behavior as well as the viscoelastic response (Figure 1 a-b), two key points that should be included in scaffolds to replicate the correct tissues function and thus correctly interact and stimulate the cell environment. Discussion This knowledge holds the potential to significantly enhance our comprehension of breast mechanics, thereby facilitating exploration into plastic surgery techniques and alternative methods for breast reconstruction. Finite element models (Figure 1d -e) offer a promising tool for simulating the entire breast or scaffold under various conditions, thereby predicting real-life outcomes.