On Low-Concentration Inks Formulated by Nanocellulose Assisted with Gelatin Methacrylate (GelMA) for 3D Printing toward Wound Healing Application.

Wenyang Xu,Stefan Willför,Fang Cheng,Dandan Su,Paul J Molino,Zhilian Yue,Gordon G Wallace,Xiaoju Wang,Binbin Zhang Molino,Chunlin Xu

doi:10.1021/acsami.8b21268

Abstract

Cellulose nanofibrils (CNFs) in the form of hydrogels stand out as a platform biomaterial in bioink formulation for 3D printing because of their low cytotoxicity and structural similarity to extracellular matrices. In the present study, 3D scaffolds were successfully printed with low-concentration inks formulated by 1 w/v % 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized CNF with less than 1 w/v % gelatin methacrylate (GelMA). Quartz crystal microbalance with dissipation monitoring (QCM-D) measurements showed strong interaction between the two biopolymers. The UV cross-linking ability of GelMA (≤1 w/v %) was enhanced in the presence of TEMPO-oxidized CNFs. Multiple factors including strong physical interaction between CNF and GelMA, in situ cross-linking of CNF by Ca2+, and UV cross-linking of GelMA enabled successful 3D printing of low-concentration inks of CNF/GelMA into scaffolds possessing good structural stability. The mechanical strength of the scaffolds was tuned in the range of 2.5 to 5 kPa. The cell culture with 3T3 fibroblasts revealed noncytotoxic and biocompatible features for the formulated inks and printed scaffolds. More importantly, the incorporated GelMA in the CNF hydrogel promoted the proliferation of fibroblasts. The developed low-concentration CNF/GelMA formulations with a facile yet effective approach to fabricate scaffolds showed great potential in 3D printing for wound healing application.

Highlights

Three-dimensional (3D) printing allows the patterning of soft biocompatible hydrogels into 3D tissue that mimic constructs, generating intricately structured scaffolds that permit researchers to study cell−cell and cell−matrix interactions.[1,2] Cellulose nanomaterials, including cellulose nanocrystals (CNCs)[3−7] and cellulose nanofibrils (CNFs), have attracted increasing attention as bioink constituents for 3D bioprinting.[8,9] This is attributable to their low cytotoxicity, structural similarity to extracellular matrices (ECM), and favorable rheological properties
This study presents a novel low-concentration ink formulation based on 1.0 w/v % TEMPO-oxidized CNF and up to 1.0 w/v % Gelatin methacrylate (GelMA) for extrusion-based 3D printing of nanocellulose hydrogel scaffolds
The molecular interaction between these two biopolymers of TEMPO-oxidized CNF and GelMA modified the rheological properties of the CNF

Summary

Introduction

Three-dimensional (3D) printing allows the patterning of soft biocompatible hydrogels into 3D tissue that mimic constructs, generating intricately structured scaffolds that permit researchers to study cell−cell and cell−matrix interactions.[1,2] Cellulose nanomaterials, including cellulose nanocrystals (CNCs)[3−7] and cellulose nanofibrils (CNFs), have attracted increasing attention as bioink constituents for 3D bioprinting.[8,9] This is attributable to their low cytotoxicity, structural similarity to extracellular matrices (ECM), and favorable rheological properties. As the pioneer in this field, Gatenholm’s group has largely contributed to the development of nanocellulosebased bioinks from 2015 for different applications including cartilage regeneration, human chondrocytes redifferentiation, and adipose tissue engineering.[10−16]. An auxiliary material is preferable to be incorporated in CNFbased bioink formulation, which imposes functionalities to aid printability and good fidelity, as well as to increase ink bioactivity.[8,9] Common strategies include direct or indirect solidification of printed objects by cross-linking either

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