Abstract
Bioprinting emerges as a powerful flexible approach for tissue engineering with prospective capability to produce tissue on demand, including biomimetic hollow-core fiber structures. In spite of significance for tissue engineering, hollow-core structures proved difficult to fabricate, with the existing methods limited to multistage, time-consuming, and cumbersome procedures. Here, we report a versatile cell-friendly photopolymerization approach that enables single-step prototyping of hollow-core as well as solid-core hydrogel fibers initially loaded with living cells. This approach was implemented by extruding cell-laden hyaluronic acid glycidyl methacrylate hydrogel directly into aqueous solution containing free radicals generated by continuous blue light photoexcitation of the flavin mononucleotide/triethanolamine photoinitiator. Diffusion of free radicals from the solution to the extruded structure initiated cross-linking of the hydrogel, progressing from the structure surface inwards. Thus, the cross-linked wall is formed and its thickness is limited by penetration of free radicals in the hydrogel volume. After developing in water, the hollow-core fiber is formed with centimeter range of lengths. Amazingly, HaCaT cells embedded in the hydrogel successfully go through the fabrication procedure. The broad size ranges have been demonstrated: from solid core to 6% wall thickness of the outer diameter, which was variable from sub-millimeter to 6 mm, and Young’s modulus ∼1.6 ± 0.4 MPa. This new proof-of-concept fibers photofabrication approach opens lucrative opportunities for facile three-dimensional fabrication of hollow-core biostructures with controllable geometry.
Highlights
Three-dimensional (3D) printing is widespread additive manufacturing technology for fabricating spatially precise structures highly demanded in regenerative medicine
Hyaluronic acid was converted to photocurable form by chemical modification in aqueous medium with glycidyl methacrylate to introduce moieties with the vinyl group (Figure 1)
We synthesized a number of Hyaluronic acid glycidyl methacrylate (HAGM) modifications with various degrees of substitution (DS) from 11.0 to 69.3%
Summary
Three-dimensional (3D) printing is widespread additive manufacturing technology for fabricating spatially precise structures highly demanded in regenerative medicine. Hydrogel hollow-core fibers represent a broad class of ubiquitous biomimetic structures, such as biomimetic blood vessels and bile ducts, and are highly demanded for many applications in tissue engineering. Since photocuring represents the most precise approach to form microand macrostructures, a careful selection of polymer and photoinitiator as the key components of the inks is required. To this aim, modified naturally derived polymers based on conjugates of gelatin (Suvarnapathaki et al, 2018), collagen (Gentile et al, 2017), chitosan (Sultankulov et al, 2019), and hyaluronic acid (HA) (Kufelt et al, 2014) are the best candidates to co-realize tunable mechanical and biocompatible properties. To meet stringent biomedical requirements, a photoinitiator must be water miscible, feature lack of dark cytotoxicity and moderate light toxicity, and have non-toxic photoproducts and preferable properties of photoactivation in visible or near-infrared spectral ranges
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