Creating Physicochemical Gradients in Modular Microporous Annealed Particle Hydrogels via a Microfluidic Method. (4th December 2019)

• Record Type: Journal Article
• Authors: Xin, Shangjing; Dai, Jing; Gregory, Carl A.; Han, Arum; Alge, Daniel L.
• Is Part Of: Advanced functional materials. Volume 30:Number 6(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-12-04
• Subjects: cell–material interactions -- gradient -- hydrogels -- microfluidics -- microgels; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201907102
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: Microporous annealed particle (MAP) hydrogels are an attractive platform for engineering biomaterials with controlled heterogeneity. Here, a microfluidic method is introduced to create physicochemical gradients within poly(ethylene glycol) based MAP hydrogels. By combining microfluidic mixing and droplet generator modules, microgels with varying properties are produced by adjusting the relative flow rates between two precursor solutions and collected layer‐by‐layer in a syringe. Subsequently, the microgels are injected out of the syringe and then annealed with thiol‐ene click chemistry. Fluorescence intensity measurements of constructs annealed in vitro and after mock implantation into a tissue defect show that a continuous gradient profile is achieved and maintained after injection, indicating utility for in situ hydrogel formation. The effects of physicochemical property gradients on human mesenchymal stem cells (hMSCs) are also studied. Microgel stiffness is studied first, and the hMSCs exhibit increased spreading and proliferation as stiffness increased along the gradient. Microgel degradability is also studied, revealing a critical degradability threshold above which the hMSCs spread robustly and below which they are isolated and exhibit reduced spreading. This method of generating spatial gradients in MAP hydrogels can be further used to gain new insights into cell–material interactions, which can be leveraged for tissue engineering applications. Abstract : A new droplet microfluidic approach to obtain microporous annealed particle hydrogels with physicochemical gradients is presented. Gradient formation is achieved by precisely controlling the mixing of two precursor solutions, and the gradient can be maintained after injection. This approach can be leveraged to produce new materials for tissue repair and to gain unique insights on cell–material interactions.