3D Control of Properties in Single-Material Digital Stereolithography for the Treatment of Growth Plate Injury*

A predominant challenge in tissue engineering is the need of a technique for producing structures with precise three-dimensional control of mechanical properties. We use pediatric physeal tissue engineering as a model application because damaged cartilage within the physis (growth plate) can lead to bone formation and asymmetric growth arrest. The growth plate has three distinct zones where cells evolve differently depending on the chemical and mechanical environment. Here, we present the first demonstration of micron scale 3D control of mechanical properties using a single cytocompatible material. Our findings indicate that the mechanical and chemical properties of materials patterned using stereolithography can be programmed by a model that accounts for the non-reciprocal relationship between intensity, time and conversion. In this work we use a poly(ethylene glycol) diacrylate based hydrogel to implement a step function and a gradual change in mechanical properties in 3D scaffolds. The model is validated by a novel application of atomic force microscopy. As a proof of concept, pillar structures were implanted into a rabbit model of physeal injury and there was an apparent reduction in bony bar reformation after 8 weeks of implantation.