Tuning the mechanics of 3D-printed scaffolds by crystal lattice-like structural design for breast tissue engineering.

Breast tissue engineering is a promising alternative to standard treatments for breast defects. Although there is a consensus that the mechanical property of the scaffold should best match the reconstructed tissue, the simulation of the soft and elastic tactility of native breast tissues using conventional materials and architecture design requires further study. Previous research has shown that the crystal microstructure-like design can drastically alter the mechanical properties of the constructed scaffolds. In this study, we designed and additive manufactured four kinds of breast scaffolds using polyurethane and termed their architectures as N5S4, N9S8, N7S6 and N4S6. The basic unit cell of each scaffold was similar to a lattice structure from the isometric crystal system. The scaffolds possessed identical porosity but different mechanical properties in which the compressive modulus of the softest scaffolds (N5S4) were similar to that of native breast tissue. When applied in the construction of tissue-engineered breast combining with delayed fat injection technique in nude rat models, the soft scaffolds(N5S4) performed better compared to its stiff counterpart (N4S6), as higher adipose survival, vascularization and milder fibrosis could be observed in N5S4 scaffolds . Lastly, using finite element analysis, we further investigated the influence of the unit cell architectures on the mechanical properties of the scaffolds and simulated the deformation as well as stress distribution patterns of the implanted scaffolds in detail. Thus, a crystal lattice-like architecture design was introduced to tune the mechanical properties of the scaffolds and match the requirements for tissue engineering applications.