Tissue engineering has made extensive advances in the creation of biomaterials and scaffolds to better study the effects of treatments and therapies in vitro, but the spatial control over mechanical heterogeneity is a characteristic that scientists have struggled to achieve. The emergent rise of 3D printing has led to greater interest in 3D bioprinting through the current use of gel layers. The potential applications of 3D bioprinting tissues and organs are indisputable including the support for personalized medicine. For example, cardiovascular disease often creates a hardening of blood vessels and the printed organs can potentially alleviate and replace the affected areas. Bio-stereolithography is a form of 3D bioprinting that prints biological material layer-by-layer through photopolymerization. The introduction of oxygen has traditionally been considered a negative feature because oxygen can inhibit free-radical polymerization, leading to incomplete curing. In contrast, controlled oxygen inhibition has great potential for high-throughput light-controlled photo-polymerizations.
Scientists from the University of Colorado Boulder took advantage of oxygen inhibition to create varying degrees of rigidity by controlling a printed layer’s stiffness to mimic actual tissue structures. An oxygen inhibition layer was introduced between a cured polymer structure and an oxygen-permeable window to physically limit the curing thickness, with the stiffness of the material increasing with UV exposure dosage.
To demonstrate the applicability of the engineered tissue, vascular smooth muscle cells were seeded on to the matrix resulting in a demonstration of a preferential cell migration response to its physiological environment. Several vascular-tube-like structures were printed with different alternating stiffness patterns, were used to observe the effects of cell behavior. Cells were observed to have migrated uniformly across the inner and outer walls of the structure forming an almost tissue-like vascular tube structure, although the cells were considerably exclusive to the stiffer regions of the printed matrix.
There are an extensive number of factors that scientists must imitate to generate engineered tissues for therapies and treatments. This study provides an innovative method to controlling the stiffness and geometries of biomaterials generated by 3D printing.
This article titled “Orthogonal programming of heterogeneous micro-mechano-environments and geometries in three-dimensional bio-stereolithography” was published in Nature Communications.