Engineered tubular constructs made from soft biomaterials are employed in a myriad of applications in biomedical science. Potential uses of these constructs range from vascular grafts to conduits for enabling perfusion of engineered tissues and organs. The fabrication of standalone tubes or complex perfusable constructs from biofunctional materials, including hydrogels, via rapid and readily accessible routes is desirable. Here we report a methodology in which customized coaxial nozzles are 3D printed using commercially available stereolithography (SLA) 3D printers. These nozzles can be used for the fabrication of hydrogel tubes via coextrusion of two shear-thinning hydrogels: an unmodified Pluronic® F-127 (F127) hydrogel and an F127bisurethane methacrylate (F127-BUM) hydrogel. We demonstrate that different nozzle geometries can be modeled via computer-aided design and 3D printed in order to generate tubes or coaxial filaments with different cross-sectional geometries. We were able to fabricate tubes with luminal diameters or wall thicknesses as small as ~150 μm. Finally, we show that these tubes can be functionalized with collagen I to enable cell adhesion, and human umbilical vein endothelial cells can be cultured on the luminal surfaces of these tubes to yield tubular endothelial monolayers. Our approach could enable the rapid fabrication of biofunctional hydrogel conduits which can ultimately be utilized for engineering in vitro models of tubular biological structures.
We describe the synthesis, characterization and direct-write 3D printing of triblock copolymer hydrogels that have a tunable response to temperature and shear stress. In aqueous solutions, these polymers utilize the temperature-dependent self-association of poly(alkyl glycidyl ether) 'A' blocks and a central poly(ethylene oxide) segment to create a physically crosslinked three-dimensional network. The temperature response of these hydrogels was dependent upon composition, chain length and concentration of the 'A' block in the copolymer. Rheological experiments confirmed the existence of sol-gel transitions and the shear-thinning behavior of the hydrogels. The temperature-and shear-responsive properties enabled direct-write 3D printing of complex objects with high fidelity. Hydrogel cytocompatibility was also confirmed by incorporating HeLa cells into select hydrogels resulting in high viabilities over 24 h. The tunable temperature response and innate shear-thinning properties of these hydrogels, coupled with encouraging cell viability results, present an attractive opportunity for additive manufacturing and tissue engineering applications.
Mechanically robust bulk antimicrobial
polymers are one way to
address disease transmission via contaminated surfaces. Here, we demonstrate
the visible light photo-oxidative cross-linking of amine-containing
PDMS using a single-component, solvent-free system where amines have
a dual role as antimicrobial functionalities and cross-linking sites.
Rose Bengal, a xanthene dye used as a fluorescent stain, is thermally
reacted with the polymer to give a solvent-free liquid siloxane that
can generate reactive singlet oxygen upon aerobic green light irradiation,
coupling the amine functionalities into imine cross-links. Photorheological
experiments demonstrate that light intensity is the largest kinetic
factor in the photo-oxidative curing of these polymers. Room temperature
irradiation under an ambient atmosphere results in free-standing elastic
materials with mechanical properties that depend on the amount of
Rose Bengal present. An ultimate elongation strain of 117% and Young’s
modulus of 2.15 MPa were observed for the highest dye loading, with
both mechanical properties found to be higher than those for the same
solution-based dye amounts. We demonstrate that the solvent-free nature
of the material can be exploited to generate 3D structures using low-temperature
deposition as well as direct-write patterning and photolithography
on glass substrates. The antimicrobial activity was investigated,
with the cross-linked material demonstrating greater efficacy against E. coli (Gram negative) compared with MRSA (Gram
positive) bacterial strains and inducing complete cell lysis of incubated
CHO-K1 mammalian cells, demonstrating applicability as a mechanically
robust single-component antimicrobial elastomer.
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