Microfluidic Fabrication of Click Chemistry-Mediated Hyaluronic Acid Microgels: A Bottom-Up Material Guide to Tailor a Microgel's Physicochemical and Mechanical Properties.

Thomas Heida,Julian Thiele,Doreen Biedenweg,Nicolas Hauck,Oliver Otto

doi:10.3390/polym12081760

Thomas Heida, Julian Thiele + Show 3 more

Open Access

https://doi.org/10.3390/polym12081760

Copy DOI

Abstract

The demand for tailored, micrometer-scaled biomaterials in cell biology and (cell-free) biotechnology has led to the development of tunable microgel systems based on natural polymers, such as hyaluronic acid (HA). To precisely tailor their physicochemical and mechanical properties and thus to address the need for well-defined microgel systems, in this study, a bottom-up material guide is presented that highlights the synergy between highly selective bio-orthogonal click chemistry strategies and the versatility of a droplet microfluidics (MF)-assisted microgel design. By employing MF, microgels based on modified HA-derivates and homobifunctional poly(ethylene glycol) (PEG)-crosslinkers are prepared via three different types of click reaction: Diels–Alder [4 + 2] cycloaddition, strain-promoted azide-alkyne cycloaddition (SPAAC), and UV-initiated thiol–ene reaction. First, chemical modification strategies of HA are screened in-depth. Beyond the microfluidic processing of HA-derivates yielding monodisperse microgels, in an analytical study, we show that their physicochemical and mechanical properties—e.g., permeability, (thermo)stability, and elasticity—can be systematically adapted with respect to the type of click reaction and PEG-crosslinker concentration. In addition, we highlight the versatility of our HA-microgel design by preparing non-spherical microgels and introduce, for the first time, a selective, hetero-trifunctional HA-based microgel system with multiple binding sites. As a result, a holistic material guide is provided to tailor fundamental properties of HA-microgels for their potential application in cell biology and (cell-free) biotechnology.

Highlights

Microgels are solvent-swollen macromolecular networks forming finite structures ranging in size from tens of micrometers to the nanometer scale [1]
Cycloaddition [34,35], and strain-promoted azide-alkyne cycloaddition (SPAAC) [36,37], which have been widely reported for biomaterial design in bulk (Figure 1)
Both DMTMM- and EDC-activated hyaluronic acid (HA)-derivatives are incubated with PDPH, which is applied as a coupling reagent in the later-described synthesis of thiol-modified HA (HASH) (Figure S1C and Figure S2) [28]

Summary

Introduction

Microgels are solvent-swollen macromolecular networks forming finite structures ranging in size from tens of micrometers to the nanometer scale [1] Due to their unique versatility regarding the adjustment of mechanical and physicochemical properties, microgels have attracted attention as promising substrates, e.g., for engineered extracellular matrices (ECMs) [2,3] drug delivery systems [4,5,6], or cell-free biosynthesis environments [7,8,9]. Droplet microfluidics (MF), as the method of choice, overcomes these limitations in design flexibility, allowing for precisely tailoring microgel particles regarding—among other parameters—size, shape, permeability, elasticity, and functionality This distinct control originates from the ability to precisely manipulate flow rates, flow pattern formation, and mixing of microgel precursors inside microfluidic devices, which are commonly fabricated by combined photo and soft lithography [15,16]. Due to short dwell times and fast mixing dynamics facilitated by customized microchannels, even fast-gelling polymer materials can be processed without forming spatially heterogeneous polymer networks [17]

Methods

Results

Conclusion