Three-dimensional (3D) printing is an emerging approach for rapid fabrication of complex tissue structures using cell-loaded bioinks. However, 3D bioprinting has hit a bottleneck in progress because of the lack of suitable bioinks that are printable, have high shape fidelity, and are mechanically resilient. In this study, we introduce a new family of nanoengineered bioinks consisting of kappa-carrageenan (κCA) and two-dimensional (2D) nanosilicates (nSi). κCA is a biocompatible, linear, sulfated polysaccharide derived from red algae and can undergo thermo-reversible and ionic gelation. The shear-thinning characteristics of κCA were tailored by nanosilicates to develop a printable bioink. By tuning κCA-nanosilicate ratios, the thermo-reversible gelation of the bioink can be controlled to obtain high printability and shape retention characteristics. The unique aspect of the nanoengineered κCA-nSi bioink is its ability to print physiologically-relevant-scale tissue constructs without requiring secondary supports. We envision that nanoengineered κCA-nanosilicate bioinks can be used to 3D print complex, large-scale, cell-laden tissue constructs with high structural fidelity and tunable mechanical stiffness for regenerative medicine.

Clay nanomaterials are an emerging class of two-dimensional (2D) biomaterials of interest due to their atomically thin layered structure, discotic charged characteristics and well-defined composition. Synthetic nanoclays are plate-like polyions composed of simple or complex salts of silicic acids with a heterogeneous charge distribution and patchy interactions. Due to their biocompatible characteristics, unique shape, high surface-to-volume ratio and charge distribution, nanoclays are investigated for various biomedical applications. This review article will provide a critical overview of the physical, chemical and physiological interactions of nanoclays with biological moieties including cells, proteins and polymers. The state-of-the-art biomedical applications of 2D nanoclay in regenerative medicine, therapeutic delivery and additive manufacturing are reviewed. In addition, recent developments that are shaping this emerging field are discussed and promising new research directions for 2D nanoclay-based biomaterials are identified.

We introduce an enhanced nanoengineered ionic-covalent entanglement (NICE) bioink for the fabrication of mechanically stiff and elastomeric 3D biostructures. NICE bioink formulations combine nanocomposite and ionic-covalent entanglement (ICE) strengthening mechanisms to print customizable cell-laden constructs for tissue engineering with high structural fidelity and mechanical stiffness. Nanocomposite and ICE strengthening mechanisms complement each other through synergistic interactions, improving mechanical strength, elasticity, toughness, and flow properties beyond the sum of the effects of either reinforcement technique alone. Herschel-Bulkley flow behavior shields encapsulated cells from excessive shear stresses during extrusion. The encapsulated cells readily proliferate and maintain high cell viability over 120 days within the 3D-printed structure, which is vital for long-term tissue regeneration. A unique aspect of the NICE bioink is its ability to print much taller structures, with higher aspect ratios, than can be achieved with conventional bioinks without requiring secondary supports. We envision that NICE bioinks can be used to bioprint complex, large-scale, cell-laden constructs for tissue engineering with high structural fidelity and mechanical stiffness for applications in custom bioprinted scaffolds and tissue engineered implants.

SignificanceWe demonstrate the use of next-generation sequencing technology (RNA-seq) to understand the effect of a two-dimensional nanomaterial on human stem cells at the whole-transcriptome level. Our results identify more than 4,000 genes that are significantly affected, and several biophysical and biochemical pathways are triggered by nanoparticle treatment. We expect that this systematic approach to understand widespread changes in gene expression due to nanomaterial exposure is key to develop new bioactive materials for biomedical applications.