Multi-material bio-fabrication of hydrogel cantilevers and actuators with stereolithography

Abstract

Cell-based biohybrid actuators are integrated systems that use biological components including proteins and cells to power material components by converting chemical energy to mechanical energy. The latest progress in cell-based biohybrid actuators has been limited to rigid materials, such as silicon and PDMS, ranging in elastic moduli on the order of mega (10(6)) to giga (10(9)) Pascals. Recent reports in the literature have established a correlation between substrate rigidity and its influence on the contractile behavior of cardiomyocytes (A. J. Engler, C. Carag-Krieger, C. P. Johnson, M. Raab, H. Y. Tang and D. W. Speicher, et al., J. Cell Sci., 2008, 121(Pt 22), 3794-3802, P. Bajaj, X. Tang, T. A. Saif and R. Bashir, J. Biomed. Mater. Res., Part A, 2010, 95(4), 1261-1269). This study explores the fabrication of a more compliant cantilever, similar to that of the native myocardium, with elasticity on the order of kilo (10(3)) Pascals. 3D stereolithographic technology, a layer-by-layer UV polymerizable rapid prototyping system, was used to rapidly fabricate multi-material cantilevers composed of poly(ethylene glycol) diacrylate (PEGDA) and acrylic-PEG-collagen (PC) mixtures. The incorporation of acrylic-PEG-collagen into PEGDA-based materials enhanced cell adhesion, spreading, and organization without altering the ability to vary the elastic modulus through the molecular weight of PEGDA. Cardiomyocytes derived from neonatal rats were seeded on the cantilevers, and the resulting stresses and contractile forces were calculated using finite element simulations validated with classical beam equations. These cantilevers can be used as a mechanical sensor to measure the contractile forces of cardiomyocyte cell sheets, and as an early prototype for the design of optimal cell-based biohybrid actuators.

Structured Macroporous Hydrogels: Progress, Challenges, and Opportunities

“…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). Such level of control may be particularly useful in tissue engineering applications to create well-defined geometric niches to direct cell behavior [88] in a way not possible with other techniques for fabricating structured macroporous hydrogels.…”

Three-dimensionally printed biological machines powered by skeletal muscle

“…This advantageous property has helped to produce machines that include selfassembling microelectromechanical-system-based cantilevers (15), 2D biohybrid "muscular thin films" (16), and "crab-like" robots (17). These systems were powered by applied electric field stimulation or spontaneous contraction of engineered cardiac muscle, which have also been used as power sources for locomotive machines such as a swimming muscle-elastomer "jellyfish" (18), a self-propelled swimming robot (19), and a walking millimeter-scale "biological bimorph" cantilever (20,21), respectively.…”

Bioengineering Methods for Analysis of Cells In Vitro

“…For instance, photopatterning methods, in which the cell/prepolymer (e.g., PEG diacrylate) solution is exposed to UV light through a photomask, have been utilized to create constructs with a spectrum of shapes and sizes as well as multilayer hydrogels with different cell types and modular architectures , Hahn et al 2006, Liu Tsang et al 2007, Liu & Bhatia 2002, Revzin et al 2001, Underhill et al 2007). Laser-based stereolithography techniques also have been applied to the fabrication of multilayer PEG hydrogels, including composite systems incorporating tethered ECM molecules such as collagen (Chan et al 2010(Chan et al , 2012. Microscale patterning of 3D hydrogels has been shown to improve the viability of encapsulated cells by mitigating the nutrient-delivery limitations present in a bulk gel configuration (Liu Tsang et al 2007).…”