Regulable Supporting Baths for Embedded Printing of Soft Biomaterials with Variable Stiffness

Abstract

Three-dimensional (3D) embedded printing is emerging as a potential solution for the fabrication of complex biological structures and with ultrasoft biomaterials. For the supporting medium, bulk gels can support a wide range of bioinks with higher printing resolution as well as better finishing surfaces than granular microgel baths. However, the difficulties of regulating the physical properties of existing bulk gel supporting baths limit the further development of this method. This work has developed a bulk gel supporting bath with easily regulable physical properties to facilitate soft-material fabrication. The proposed bath is composed based on the hydrophobic association between a hydrophobically modified hydroxypropylmethyl cellulose (H-HPMC) and Pluronic F-127 (PF-127). Its rheological properties can be easily regulated; in the preprinting stage by varying the relative concentration of components, during printing by changing the temperature, and postprinting by adding additives with strong hydrophobicity or hydrophilicity. This has made the supporting bath not only available for various bioinks with a range of printing windows but also easy to be removed. Also, the removal strategy is independent of printing conditions like temperature and ions, which empowers the bath to hold great potential for the embedded printing of commonly used biomaterials. The adjustable rheological properties of the bath were leveraged to characterize the embedded printing quantitatively, involving the disturbance during the printing, filament cross-sectional shape, printing resolution, continuity, and the coalescence between adjacent filaments. The match between the bioink and the bath was also explored. Furthermore, low-viscosity bioinks (with 0.008–2.4 Pa s viscosity) were patterned into various 3D complex delicate soft structures (with a 0.5–5 kPa compressive modulus). It is believed that such an easily regulable assembled bath could serve as an available tool to support the complex biological structure fabrication and open unique prospects for personalized medicine.

Instant Assembly of Collagen for Scaffolding, Tissue Engineering, and Bioprinting

“…Notably, the TRACEprinted structure demonstrated MMC-induced rapid gelation and was easily released from the bath without disrupting its integrity. In contrast, the same design printed in the regular support bath did not maintain its structure and disintegrated after the releasing due to insufficient gelation, as unmodified collagen typically requires much longer gelation time (≥ 30 minutes) 24,25,17,18 .…”

“…Recent advances in bioprinting collagen I include the usage of a granular hydrogel support bath to help maintain collagen positioning after extrusion [15][16][17] . The neutral-pH support bath promotes gelation of high concentration acid solubilized collagen upon extrusion, enabling highresolution printing of complex and mainly cell-free 3D constructs 15 .…”

Recent advances in 3D printing sacrificial templates for fabricating engineered vasculature

“…Pluronic F-127 shows superior printability and shear thinning feature at room temperature (25°C) and liquefies at 4°C. 84 Thus, Pluronic F-127 has been widely used as a sacrificial material to fabricate engineered vasculature. 3D printing sacrificial Pluronic F-127 on a crosslinked layer of hydrogel is the most common method for fabricating engineered vasculature.…”

“…Pluronic F‐127 shows superior printability and shear thinning feature at room temperature (25°C) and liquefies at 4°C 84 . Thus, Pluronic F‐127 has been widely used as a sacrificial material to fabricate engineered vasculature.…”

Biomaterial-Based Biomimetic Visual Sensors: Inkjet Patterning of Bacteriorhodopsin

“…Inkjet printing is attracting a great deal of attention as a method that can print patterns freely and manufacture under mild conditions. − Considering that biomaterials like bR are unstable in heat and vacuum, drawing patterns directly using inkjet printing is suitable for the production of biomaterial-based devices. While some biomaterials are currently used for inkjet printing, ,− the printability of biomaterials depends on physical or chemical properties such as particle size and viscosity. Research on inkjet printing using bR has also been conducted, and the possibility of patterning by inkjet printing has been shown …”