Mechanical Properties, Cytocompatibility and Manufacturability of Chitosan:PEGDA Hybrid-Gel Scaffolds by Stereolithography

Abstract

Extracellular matrix mimetic hydrogels which hybridize synthetic and natural polymers offer molecularly-tailored, bioactive properties and tunable mechanical strength. In addition, 3D bioprinting by stereolithography allows fabrication of internal pores and defined macroscopic shapes. In this study, we formulated a hybrid biocompatible resin using natural and synthetic polymers (chitosan and polyethylene glycol diacrylate (PEGDA), respectively) by controlling molecular weight of chitosan, feed-ratios, and photo-initiator concentration. Ear-shaped, hybrid scaffolds were fabricated by a stereolithographic method using a 405 nm laser. Hybrid hydrogel scaffolds of chitosan (50-190 kDa) and PEGDA (575 Da) were mixed at varying feed-ratios. Some of the cationic, amino groups of chitosan were neutralized by dialysis in acidic solution containing chitosan in excess of sodium acetate solution to inhibit quenching of newly formed photoradicals. A feed-ratio of 1:7.5 was found to be the most appropriate of the formulations considered in this study in terms of mechanical properties, cell adhesion, and printability. The biofabricated hybrid scaffold showed interconnected, homogeneous pores with a nominal pore size of 50 µm and an elastic modulus of ~400 kPa. Moreover, long-term cell viability and cell spreading was observed via actin filament staining. Printability of the biocompatible resin was confirmed by printing thresholded MR images of an ear and the feed ratio of 1:7.5 provided the most faithful reproduction of the shape. To the best of our knowledge, this is the first report of stereolithographic printing hybridizing cell-adhesive properties of chitosan with mechanical robustness of PEG in scaffolds suitable for repair of complex tissue geometries, such as those of the human ear.

Recent Advances in Bioink Design for 3D Bioprinting of Tissues and Organs

“…Stereolithography (SLA) requires a viscous photocurable polymer solution or a prepolymer, which is exposed to a directed light (such as UV or laser) to spatially cross-link the solution (Skoog et al, 2014). SLA could potentially be considered for printing live cells as long as a cell-laden prepolymer formulation is used and the photocuring takes place in a mild, cell friendly condition, which are the two major issues for SLA in bioprinting (Elomaa et al, 2015; Wang et al, 2015; Morris et al, 2017). When 3D printing technologies are considered for bioprinting, the most commonly used technologies are DIW and inkjet printing (Ozbolat et al, 2016, 2017).…”

Structured Macroporous Hydrogels: Progress, Challenges, and Opportunities

“…Stereolithography has been particularly commonly exploited in this context given its capacity for processing different polymers. For example, Morris et al fabricated ear-shaped scaffolds consisting of chitosan and polyethylene glycol diacrylate (PEGDA) that contained a macroporous interconnective pore structure, [93] Elomaa et al created photocrosslinkable PEG-co-polydepsipeptide macromer to fabricate cell-laden hydrogels, [94] and Chan et al used a commercial stereolithographic printer to prepare 3D structured PEG-based hydrogels. [95,96] The clear advantage of 3D printing over all other described techniques is the precise detail on pore shape, alignment, size, and structure that can be designed into the product, as the resulting pore structure is neither the product of thermodynamics (emulsification), fluid mechanics (porogen distribution in the matrix), nor random events (nucleate evaporation in gas foaming, whipping in electrospinning).…”

A cross-linking strategy with moderated pre-polymerization of resin for stereolithography

“…inner holes, porous structures and micro-structures. [1][2][3][4][5][6][7][8][9][10] Due to the growing popularity of AM and the gradual expanding of its application scope, stereolithography (SLA) as the most versatile method with high accuracy and precision has attracted increasing attention. SLA is based on a liquid resin photocuring process wherein liquid resin (a blend for polymerization or crosslinking) is placed in a reservoir.…”

“…11 The laser intensity required to initiate such a photo-polymerization process is rather low, typically between 10 mW to 1 W, which is economically attractive. SLA is now oen used in industrial and medical sectors, 1,3,4,6,12,13 which is still underutilized as an industrial process. It can only manufacture limited functional parts, which limits its application from prototyping to the actual parts, and only a very small group utilize SLA for the production of nal parts.…”