Mohseni, Mina (Centre in Regenerative Medicine, Queensland University of Technology (QUT), Brisbane, QLD 4059, Australia )


Simultaneous flexibility, strength and toughness are exceptional characteristics of soft biological tissues which do not exist in man-made materials. Soft tissue-engineered meshes (sTEMs) should exhibit tissue-like mechanics and geometries for better performance and fit. However, the majority of current clinical meshes for soft tissue regeneration are conventional fabrics made by knitting or weaving, which have limited fabrication capabilities to adapt the meshes with diverse mechanics and geometries. This limitation has led to noncompatible conformability and compliance, which result in undesired mesh performance and fit. Moreover, the lack of local reinforcement of regions that require stronger supports has increased the risk of mechanical failure of the meshes as they shrink. GalaformTM is only commercialized sTEMs with a reinforcing rim for plastic and reconstructive surgery; however, it does not offer customized meshes with patients’ specific reinforcements. In this study, we established a biomimetic design strategy and a manufacturing platform to develop flexible, strong, and tough meshes for soft tissue reconstruction.
A biomimetic design strategy was developed to control the non-linear mechanical response of meshes at a unit-cell scale and incorporate a stretchable polymer, Strataprene® (ST), and a strong polymer, Caproprene® (CAP) or Lactoprene® (LAC) in a composite fashion to simultaneously address the required flexibility, strength, and toughness within one integrated structure. The design is composed of two series of sinusoidal curves with tailored amplitudes to control the level of polymers’ contributions at three different stages of deformation. On the one hand, the smaller curves are attributed to the stretchable polymer since they straighten faster than large curves and should tolerate a high elongation to allow further stages of deformations to occur. On the other hand, the larger curves are attributed to the stronger polymers to support a rapid increase in the strength of the structure as they are lined up at high load regimes. Utilizing multi-material printing offered by FFF technique and toolpath planning programmed by MATLAB scripts, these polymers were placed in pre-designed patterns. Two series of meshes with uniaxial and biaxial strength were fabricated and characterized comprehensively.
Under tension, the meshes indicated a three-stage mechanical response, where at stage 1, ST curves turned into straightened position and induced the first dynamic transition in the architecture leading to a J-shape stress-strain response. At stage 2, CAP or LAC curves were aligned parallelly to the deformation direction and produced the second J shape response with a higher level of stress compared to stage 1. At stage 3, both polymers were fully elongated and exhibited a linear elastic response. Since CAP and LAC have a significantly higher elastic modulus when compared to ST, they mainly dominated the mechanical response of the last stage and increased the strength of the structure rapidly. Therefore, the structure highly indicated stretchability at low load regime while tolerating large stress and absorbing high energy at high load regime.
The proposed platform offers a high level of design flexibility to develop both mechanically and geometrically functional and customized scaffolds, not achievable by the currently commercialized meshes in the market.


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