3D Bioprintable Hydrogel with Tunable Stiffness for Exploring Cells Encapsulated in Matrices of Differing Stiffnesses.

In vitro cell models have undergone a shift from 2D models on glass slides to 3D models that better reflect the native 3D microenvironment. 3D bioprinting promises to progress the field by allowing the high-throughput production of reproducible cell-laden structures with high fidelity. The current stiffness range of printable matrices surrounding the cells that mimic the extracellular matrix environment remains limited. The work presented herein aims to expand the range of stiffnesses by utilizing a four-armed polyethylene glycol with maleimide-functionalized arms. The complementary cross-linkers comprised a matrix metalloprotease-degradable peptide and a four-armed thiolated polymer which were adjusted in ratio to tune the stiffness. The modularity of this system allows for a simple method of controlling stiffness and the addition of biological motifs. The application of this system in drop-on-demand printing is validated using MCF-7 cells, which were monitored for viability and proliferation. This study shows the potential of this system for the high-throughput investigation of the effects of stiffness and biological motif compositions in relation to cell behaviors.

Lanthanide-based ß-Tricalcium Phosphate Upconversion Nanoparticles as an Effective Theranostic Nonviral Vectors for Image-Guided Gene Therapy.

Lanthanide-based beta-tricalcium phosphate (ß-TCP) upconversion nanoparticles are exploited as a non-viral vector for imaging guided-gene therapy by virtue of their unique optical properties and multi-modality imaging ability, high transfection efficiency, high biocompatibility, dispersibility, simplicity of synthesis and surface modification. Ytterbium and thulium-doped ß-TCP nanoparticles (ßTCPYbTm) are synthesized via co-precipitation method, coated with polyethylenimine (PEI) and functionalized with a nuclear-targeting peptide (TAT). Further, in vitro studies revealed that the nanotheranostic carriers are able to transfect cells with the plasmid eGFP at a high efficiency, with approximately 60% of total cells producing the fluorescent green protein. The optimized protocol developed comprises the most efficient ßTCPYbTm/PEI configuration, the amount and the order of assembly of ßTCPYbTm:PEI, TAT, plasmid DNA and the culturing conditions. With having excellent dispersibility and high chemical affinity toward nucleic acid, calcium ions released from ßTCPYbTm:PEI nanoparticles can participate in delivering nucleic acids and other therapeutic molecules, overcoming the nuclear barriers and improving the transfection efficacy. Equally important, the feasibility of the upconversion multifunctional nanovector to serve as an effective contrast agent for imaging modality, capable of converting low-energy light to higher-energy photons via a multi-photons mechanism, endowing greater unique luminescent properties, was successfully demonstrated.