Nanopillar Templating Augments the Stiffness and Strength in Biopolymer Films

Abstract

Natural load-bearing mammalian tissues, such as cartilage and ligaments, contain ∼70% water yet can be mechanically stiff and strong due to the highly templated structures within. Here, we present a bioinspired approach to significantly stiffen and strengthen biopolymer hydrogels and films through the combination of nanoscale architecture and templated microstructure. Imprinted submicrometer pillar arrays absorb energy and deflect cracks. The produced chitosan hydrogels show nanofiber chains aligned by nanopillar topography, subsequently templating the microstructure throughout the film. These templated nanopillar chitosan hydrogels mechanically outperform unstructured flat hydrogels, with increases in the moduli of ∼160%, up to ∼20 MPa, and work at break of ∼450%, up to 8.5 MJ m −3 . Furthermore, the strength at break increases by ∼350%, up to ∼37 MPa, and it is one of the strongest hydrogels yet reported. The nanopillar templating strategy is generalizable to other biopolymers capable of forming oriented domains and strong interactions. Overall, this process yields hydrogel films that demonstrate mechanical performance comparable to that of other stiff, strong hydrogels and natural tissues.

Insight and Recent Advances into the Role of Topography on the Cell Differentiation and Proliferation on Biopolymeric Surfaces

“…As a result, there is a plethora of miniaturized periodic biopolymeric patterns, of which the most popular are lines/stripes of various proteins, chitosan, cellulose, silk and other biomolecules [ 24 , 25 , 27 , 58 , 60 , 61 ]. Other patterns include pads of biomolecules [ 27 ], nanodots of proteins [ 62 ] as well as pillars, grooves and holes sculptured in cellulose, and in gelatins crosslinked with genipin ( Figure 1 a–c) or in chitosan [ 22 , 24 , 28 , 29 ]. More complex patterns such as spider web arrays [ 61 ] and arrays of nanodots of neutravidin, liposomes and other proteins [ 62 , 63 ] were also recently reported.…”

“…The latter can be created by utilizing a variety of simple or more complex lithography methods, ref. [ 18 , 19 , 20 , 21 ] and may include grooves [ 22 ], lines [ 23 , 24 , 25 ], squares [ 23 , 26 ] and other shapes [ 13 , 27 , 28 , 29 ] of various dimensions and functions widely used in applications related inclusively to cell culturing [ 30 , 31 , 32 , 33 , 34 , 35 ]. For instance, holes and pillars on gelatin-genipin substrates can be used for culturing human osteoblastic Saos-2 cells for developing better properties of surface dental implants [ 22 ], and the microgrooves on the chitosan membrane can be employed for enhancing nerve regeneration using Schwan cell cultures [ 36 ].…”

Customizable Low-Friction Tough Hydrogels for Potential Cartilage Tissue Engineering by a Rapid Orthogonal Photoreactive 3D-Printing Design

“…Material matrices are indispensable parts in this field and play critical roles in realizing these properties. ,− Typically, porous, water-rich hydrogels are able to mimic extracellular matrices and provide similar microenvironments for cell proliferation, nutrition delivery, and tissue generation. − The introduction of functional components in hydrogels will improve their mechanical property, biocompatibility, diagnosis, and therapy performances. For example, nanoparticles such as hydroxyapatite, silicon dioxide, and calcium phosphate have been widely employed for the preparation of hydrogels with high mechanical strength and toughness. , Natural macromolecules, including gelatin, chitosan, and sodium alginate, are generally used for fabricating biocompatible hydrogels that facilitate cell growth and differentiation in biomimetic tissue engineering. − Moreover, anti-osteoporotic drugs of activated vitamin D and calcium salt have been introduced into a hydrogel for promoting bone tissue regeneration. , These pioneered works demonstrate that high-performance hydrogels are promising candidates for designing artificial scaffolds for advanced clinical applications.…”

“…For example, nanoparticles such as hydroxyapatite, silicon dioxide, and calcium phosphate have been widely employed for the preparation of hydrogels with high mechanical strength and toughness. 19,20 Natural macromolecules, including gelatin, chitosan, and sodium alginate, are generally used for fabricating biocompatible hydrogels that facilitate cell growth and differentiation in biomimetic tissue engineering. 21−23 Moreover, anti-osteoporotic drugs of activated vitamin D and calcium salt have been introduced into a hydrogel for promoting bone tissue regeneration.…”