ABSTRACT
Granular hydrogels composed of hydrogel microparticles are promising candidates for 3D bioprinting due to their ability to protect encapsulated cells. However, to achieve high print fidelity, hydrogel microparticles need to jam to exhibit shear-thinning characteristics, which is crucial for 3D printing. Unfortunately, this overpacking can significantly impact cell viability, thereby negating the primary advantage of using hydrogel microparticles to shield cells from shear forces. To overcome this challenge, a novel solution: a biphasic, granular colloidal bioink designed to optimize cell viability and printing fidelity is introduced. The biphasic ink consists of cell-laden polyethylene glycol (PEG) hydrogel microparticles embedded in a continuous gelatin methacryloyl (GelMA)-nanosilicate colloidal network. Here, it is demonstrated that this biphasic bioink offers outstanding rheological properties, print fidelity, and structural stability. Furthermore, its utility for engineering complex tissues with multiple cell types and heterogeneous microenvironments is demonstrated, by incorporating ß-islet cells into the PEG microparticles and endothelial cells in the GelMA-nanosilicate colloidal network. Using this approach, it is possible to induce cell patterning, enhance vascularization, and direct cellular function. The proposed biphasic bioink holds significant potential for numerous emerging biomedical applications, including tissue engineering and disease modeling.
ABSTRACT
We report a simple droplet fluidic point-of-care test (POCT) that uses gravity to manipulate the sequence, timing, and motion of droplets on a surface. To fabricate this POCT, we first developed a surface coating toolbox of nine different coatings with three levels of wettability and three levels of slipperiness that can be independently tailored. We then fabricated a device that has interconnected fluidic elements-pumps, flow resistors and flow guides-on a highly slippery solid surface to precisely control the timing and sequence of motion of multiple droplets and their interactions on the surface. We then used this device to carry out a multi-step enzymatic assay of a clinically relevant analyte-lactate dehydrogenase (LDH)-to demonstrate the application of this technology for point-of-care diagnosis.
ABSTRACT
Light-responsive biomaterials are an emerging class of materials used for developing noninvasive, noncontact, precise, and controllable biomedical devices. Long-wavelength near-infrared (NIR) radiation is an attractive light source for in situ gelation due to its higher penetration depth and minimum side effects. The conventional approach to obtain crosslinked biomaterials relies heavily on the use of a photoinitiator by generating reactive species when exposed to short-wavelength radiation, which is detrimental to surrounding cells and tissue. Here, a new class of NIR-triggered in situ gelation system based on defect-rich 2D molybdenum disulfide (MoS2 ) nanoassemblies and thiol-functionalized thermoresponsive polymer in the absence of a photoinitiator is introduced. Exposure to NIR radiation activates the dynamic polymer-nanomaterials interactions by leveraging the photothermal characteristics of MoS2 and intrinsic phase transition ability of the thermoresponsive polymer. Specifically, upon NIR exposure, MoS2 acts as a crosslink epicenter by connecting with multiple polymeric chains via defect-driven click chemistry. As a proof-of-concept, the utility of NIR-triggered in situ gelation is demonstrated in vitro and in vivo. Additionally, the crosslinked gel exhibits the potential for NIR light-responsive release of encapsulated therapeutics. These light-responsive biomaterials have strong potential for a range of biomedical applications, including artificial muscle, smart actuators, 3D/4D printing, regenerative medicine, and therapeutic delivery.
Subject(s)
Disulfides , Molybdenum , Hydrogels , PhototherapyABSTRACT
The objective of this study was to evaluate the utility of gelatin-norbornene (GelNB), which is cross-linkable via thiol-ene click chemistry, and the photoinitiator lithium phenyl-2,4,6 trimethylbenzoylphosphinate (LAP) for 3D bioprinting. These materials were compared to two widely used materials, gelatin-methacryloyl (GelMA) and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (I2959). Characterization of photocuring kinetics revealed that LAP markedly improved the kinetics compared to I2959, which improved stability and print fidelity. Additionally, GelNB exhibited improved photocuring kinetics, improved stability, and decreased filament spreading compared to GelMA. However, inks containing GelMA yielded at lower stress, were more easily extruded, and produced smoother filaments. NIH 3T3 fibroblasts exhibited high viability in printed constructs, regardless of the gelatin derivative or photoinitiator used. Overall, these results support the selection of LAP over I2959 and suggest that GelNB could be a useful alternative to GelMA, although further work is needed to optimize GelNB extrusion.
