Injectable 3D Hydrogel Scaffold with Tailorable Porosity Post‐Implantation

Abstract

Since rates of tissue growth vary significantly between tissue types, and also between individuals due to differences in age, dietary intake, and lifestyle-related factors, engineering a scaffold system that is appropriate for personalized tissue engineering remains a significant challenge. In this study, a gelatin-hydroxyphenylpropionic acid/carboxylmethylcellulose-tyramine (Gtn-HPA/CMC-Tyr) porous hydrogel system that allows the pore structure of scaffolds to be altered in vivo after implantation is developed. Cross-linking of Gtn-HPA/CMC-Tyr hydrogels via horseradish peroxidase oxidative coupling is examined both in vitro and in vivo. Post-implantation, further alteration of the hydrogel structure is achieved by injecting cellulase enzyme to digest the CMC component of the scaffold; this treatment yields a structure with larger pores and higher porosity than hydrogels without cellulase injection. Using this approach, the pore sizes of scaffolds are altered in vivo from 32-87 μm to 74-181 μm in a user-controled manner. The hydrogel is biocompatible to COS-7 cells and has mechanical properties similar to those of soft tissues. The new hydrogel system developed in this work provides clinicians with the ability to tailor the structure of scaffolds post-implantation depending on the growth rate of a tissue or an individual's recovery rate, and could thus be ideal for personalized tissue engineering.

Nanofibrous Spongy Microspheres Enhance Odontogenic Differentiation of Human Dental Pulp Stem Cells

“…However, all of these adherent stem cells require beneficial scaffolding for the cells to attach, proliferate and differentiate. Therefore, scaffolds play a key role in dentin tissue engineering, which should be designed with a high porosity and interconnected pore network to facilitate cell seeding, adhesion, extracellular matrix (ECM) secretion and progressively the mineralized dentin regeneration [12, 13] . Naturally derived materials such as collagen, chitosan, and hyaluronic acid have previously been investigated for cell attachment and guidance [14, 15] .…”

In Situ Generation of Tunable Porosity Gradients in Hydrogel‐Based Scaffolds for Microfluidic Cell Culture

“…The GTN–HPA conjugate served as the backbone of the hydrogel and contained Arg‐Gly‐Asp (RGD) peptides that provide adhesive ligands for cell adhesion . The CMC–TYR conjugate, which contains CMC, a low‐cost cellulose derivative approved by the US Food and Drug Administration (FDA) for pharmaceutical use, was used as the sacrificial polymer in the GC hydrogel . The GTN–HPA and CMC–TYR conjugates were crosslinked via oxidative coupling of the phenol moieties catalyzed by horseradish peroxidase (HRP) enzyme to yield an in situ porous hydrogel; the enzyme‐mediated crosslinking process can be performed in mild conditions, that is, at room temperature and in an aqueous environment.…”

“…The GTN–HPA and CMC–TYR conjugates were crosslinked via oxidative coupling of the phenol moieties catalyzed by horseradish peroxidase (HRP) enzyme to yield an in situ porous hydrogel; the enzyme‐mediated crosslinking process can be performed in mild conditions, that is, at room temperature and in an aqueous environment. The cells were premixed with the GC hydrogel precursor solution and simply injected into the microfluidic cell culture chamber; the cells were thereby immobilized at uniform cell density within the scaffold as the hydrogel was crosslinked inside the microchamber . We note that the hydrogel may be injected to fill a microchamber of arbitrary shape.…”

“…To alter the pore size of the crosslinked GC hydrogel, a biocompatible enzyme, cellulase, was added to the hydrogel to digest the sacrificial CMC component of the hydrogel. The cellulase used was extracted from Trichoderma longibrachiatum , which is approved by the US FDA and common in the food industry . We have previously demonstrated that cellulase digests CMC selectively while remaining inert to mammalian cells and native ECM both in vitro and in vivo .…”

“…The cellulase used was extracted from Trichoderma longibrachiatum , which is approved by the US FDA and common in the food industry . We have previously demonstrated that cellulase digests CMC selectively while remaining inert to mammalian cells and native ECM both in vitro and in vivo . The GC hydrogel‐based microfluidic device developed in this work was used to study human fibrosarcoma cells (HT1080) as these cells can be readily propagated and are suitable as an invasive cancer cell model .…”