Aspiration-assisted bioprinting for precise positioning of biologics

Abstract

Three-dimensional (3D) bioprinting is an appealing approach for building tissues; however, bioprinting of mini-tissue blocks (i.e., spheroids) with precise control on their positioning in 3D space has been a major obstacle. Here, we unveil “aspiration-assisted bioprinting (AAB),” which enables picking and bioprinting biologics in 3D through harnessing the power of aspiration forces, and when coupled with microvalve bioprinting, it facilitated different biofabrication schemes including scaffold-based or scaffold-free bioprinting at an unprecedented placement precision, ~11% with respect to the spheroid size. We studied the underlying physical mechanism of AAB to understand interactions between aspirated viscoelastic spheroids and physical governing forces during aspiration and bioprinting. We bioprinted a wide range of biologics with dimensions in an order-of-magnitude range including tissue spheroids (80 to 600 μm), tissue strands (~800 μm), or single cells (electrocytes, ~400 μm), and as applications, we illustrated the patterning of angiogenic sprouting spheroids and self-assembly of osteogenic spheroids.

3D bioprinting of high cell-density heterogeneous tissue models through spheroid fusion within self-healing hydrogels

“…1a, Supplementary Movie 1). This approach avoids surface tension effects that can significantly reduce cell viability when transferring cells and spheroids between liquid and air interfaces 31 . The support hydrogel used is based on the assembly of hyaluronic acid (HA) modified with either adamantane (Ad) or β-cyclodextrin (CD) ( Supplementary Fig.…”

“…For example, spheroids can be aspirated and then skewered onto supporting metallic needles (i.e., Kenzan method) for fusion 30 . Hydrogels have also been used to support aspiration based methods, through the sequential layering of an uncrosslinked hydrogel precursor and spheroids, followed by layer crosslinking 31 . Despite advances with these bioassembly technologies, significant challenges remain, particularly to support the patterning of complex 3D structures without the need to disrupt spheroids mechanically or to use external stimuli to initiate hydrogel crosslinking.…”

Aspiration-assisted Freeform Bioprinting of Tissue Spheroids in a Yield-stress Gel

“…In this study, we further advanced our recently published Aspiration-assisted Bioprinting (AAB) technique 21 to demonstrate the freeform bioprinting of spheroids within a granular gel. Specifically, aspiration forces were used to pick up spheroids from the spheroid reservoir (placed inside the cell media compartment) and transfer them into the granular gel (occupying inside the support gel compartment) one by one ( Figs.…”

“…1E, the theoretical approach was confirmed by the experimental approach and the results were close to each other, particularly for spheroids with smaller radii. Yet, increasing aspiration pressure may lead to deformation of the spheroids 21 . Spheroids needed to be transferred in a safe manner without leading to significant deformations.…”

“…challenges of current techniques, we recently demonstrated an aspiration-assisted bioprinting (AAB) technique 21 enabling precise bioprinting of spheroids into or onto sacrificial or functional gel substrates. However, freeform bioprinting of spheroids in 3D has been a long-standing problem due to the layer-by-layer-building nature of the existing techniques.…”