Gullo, Maurizio
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Towards a novel cost-effective and versatile bioink for 3D-bioprinting in tissue engineering
3D-bioprinting for tissue regeneration relies on, among other things, hydrogels with favorable rheological properties. These include shear thinning for cell-friendly extrusion, post-printing structural stability as well as physiologically relevant elastic moduli needed for optimal cell attachment, proliferation, differentiation and tissue maturation. This work introduces a cost-efficient gelatin-methylcellulose based hydrogel whose rheological properties can be independently optimized for optimal printability and tissue engineering. Hydrogel viscosities were designed to present three different temperature regimes: low viscosity for eased cell suspension and printing with minimal shear stress, form fidelity directly after printing and long term structural stability during incubation. Enzymatically crosslinked hydrogel scaffolds with stiffnesses ranging from 5 to 50 kPa were produced, enabling the hydrogel to biomimic cell environments for different types of tissues. The bioink showed high intrinsic cytocompatibility and tissues fabricated by embedding and bioprinting NIH 3T3 fibroblasts showed satisfactory viability. This novel hydrogel uses robust and inexpensive technology, which can be adjusted for implementation in tissue regeneration, e.g., in myocardial or neural tissue engineering.
An origami 3D patterned cellulose-based scaffold for bioengineering cardiovascular applications
Directional submicrofiber hydrogel composite scaffolds supporting neuron differentiation and enabling neurite alignment
Cell cultures aiming at tissue regeneration benefit from scaffolds with physiologically relevant elastic moduli to optimally trigger cell attachment, proliferation and promote differentiation, guidance and tissue maturation. Complex scaffolds designed with guiding cues can mimic the anisotropic nature of neural tissues, such as spinal cord or brain, and recall the ability of human neural progenitor cells to differentiate and align. This work introduces a cost-efficient gelatin-based submicron patterned hydrogel–fiber composite with tuned stiffness, able to support cell attachment, differentiation and alignment of neurons derived from human progenitor cells. The enzymatically crosslinked gelatin-based hydrogels were generated with stiffnesses from 8 to 80 kPa, onto which poly(ε-caprolactone) (PCL) alignment cues were electrospun such that the fibers had a preferential alignment. The fiber–hydrogel composites with a modulus of about 20 kPa showed the strongest cell attachment and highest cell proliferation, rendering them an ideal differentiation support. Differentiated neurons aligned and bundled their neurites along the aligned PCL filaments, which is unique to this cell type on a fiber–hydrogel composite. This novel scaffold relies on robust and inexpensive technology and is suitable for neural tissue engineering where directional neuron alignment is required, such as in the spinal cord.
Rapid prototyping method for 3D printed biomaterial constructs with vascular structures
This paper presents a fabrication method for rapid prototyping of 3D biomaterial constructs with vascular structures. The method relies on poloxamer fugitive ink, which is over casted with a custom-made alginate based model extracellular matrix (ECM). The presented method is simple to implement and compatible with standard cell culture workflows used in biomedical research and pharmaceutical development. We present the material preparation, gelation properties and printing methods in detail. First experiments demonstrate the suitability of the ECM constructs for 3D tissue culture.
An origami like 3D patterned cellulose-based scaffold for bioengineering cardiovascular applications
In this work we describe the manufacturing of cellulosic, cell compatible scaffolds with an inherent 3D origami crease pattern for applications in cardiac tissue engineering. Different cellulosic materials were studied, among them cotton linters, fibers obtained from eucalyptus, pine, spruce and lyocell. Formed sheets made of cotton linters were chosen for further study due to the highest biocompatibility and mechanical properties best suited for cardiomyocytes in wet and dry conditions: E - modulus of 0.8 GPa, tensile strength of 4.7 MPa and tensile strength in wet environment of 2.28 MPa. Cell alignment is desired to achieve directional contraction of the cardiac tissue, and several options were investigated to achieve fiber alignment, e.g. a dynamic sheet former and Rapid Köthen sheet former. Although the orientation was minimal, cells cultured on the cellulose fibers grew and aligned along the fibers. Origami inspired crease patterns were applied to the cellulose scaffolds in order to introduce directional flexibility beneficial for cardiac contraction. The transfer of a Miura-ori crease pattern was successfully applied in two ways: folding of the dried sheet between PET foils pre-formed in a 3D printed mold, and in situ wet fiber molding on a 3D-patterned mesh mounted in the sheet former’s sieve section. The latter approach enables upscaling for potential mass production.
Towards 3D bioprinted spinal cord organoids
Three-dimensional (3D) cultures, so-called organoids, have emerged as an attractive tool for disease modeling and therapeutic innovations. Here, we aim to determine if boundary cap neural crest stem cells (BC) can survive and differentiate in gelatin-based 3D bioprinted bioink scaffolds in order to establish an enabling technology for the fabrication of spinal cord organoids on a chip. BC previously demonstrated the ability to support survival and differentiation of co-implanted or co-cultured cells and supported motor neuron survival in excitotoxically challenged spinal cord slice cultures. We tested different combinations of bioink and cross-linked material, analyzed the survival of BC on the surface and inside the scaffolds, and then tested if human iPSC-derived neural cells (motor neuron precursors and astrocytes) can be printed with the same protocol, which was developed for BC. We showed that this protocol is applicable for human cells. Neural differentiation was more prominent in the peripheral compared to central parts of the printed construct, presumably because of easier access to differentiation-promoting factors in the medium. These findings show that the gelatin-based and enzymatically cross-linked hydrogel is a suitable bioink for building a multicellular, bioprinted spinal cord organoid, but that further measures are still required to achieve uniform neural differentiation.