Particulate ECM biomaterial ink is 3D printed and naturally crosslinked to form structurally-layered and lubricated cartilage tissue mimics.

Articular cartilage is a layered tissue with a complex, heterogeneous structure and lubricated surface which is challenging to reproduce using traditional tissue engineering methods. Three-dimensional printing techniques have enabled engineering of complex scaffolds for cartilage regeneration, but constructs fail to replicate the unique zonal layers, and limited cytocompatible crosslinkers exist. To address the need for mechanically robust, layered scaffolds, we developed an extracellular matrix particle-based biomaterial ink (pECM biomaterial ink) which can be extruded, polymerizes via disulfide bonding, and restores layered tissue structure and surface lubrication. Our cartilage pECM biomaterial ink utilizes functionalized hyaluronan (HA), a naturally occurring glycosaminoglycan, crosslinked directly to decellularized tissue particles (ø40-100µm). We experimentally determined that HA functionalized with thiol groups (t-HA) forms disulfide bonds with the ECM particles to form a 3D network. We show that two inks can be co-printed to create a layered cartilage scaffold with bulk compressive and surface (friction coefficient, adhesion, and roughness) mechanics approaching values measured on native cartilage. We demonstrate that our printing process enables the addition of macropores throughout the construct, increasing the viability of introduced cells by 10%. The delivery of these 3D printed scaffolds to a defect is straightforward, customizable to any shape, and adheres to surrounding tissue.

Snakeskin-Inspired Elastomers with Extremely Low Coefficient of Friction under Dry Conditions.

Soft elastomers are critical to a broad range of existing and emerging technologies. One major limitation of soft elastomers is the large friction of coefficient (COF) due to inherently large adhesion and internal loss. In applications where lubrication is not applicable, such as soft robotics, wearable electronics, and biomedical devices, elastomers with inherently low dry COF are required. Inspired by the low COF of snakeskins atop soft bodies, this study reports the development of elastomers with low dry COF by growing a hybrid skin layer with a strong interface with a large stiffness gradient. Using a solid-liquid interfacial polymerization (SLIP) process, hybrid skin layers are imparted onto elastomers, which reduces the COF of the elastomers from 1.6 to 0.1, without sacrificing the bulk compliance and ductility of elastomer. Compared with existing surface modification methods, the SLIP process offers spatial control and ability to modify flat, prepatterned, curved, and inner surfaces, which is essential to engineer multifunctional skin layers for emerging applications.