Recent Advances in Microgels: From Biomolecules to Functionality

Abstract

The emerging applications of hydrogel materials at different length scales, in areas ranging from sustainability to health, have driven the progress in the design and manufacturing of microgels. Microgels can provide miniaturized, monodisperse, and regulatable compartments, which can be spatially separated or interconnected. These microscopic materials provide novel opportunities for generating biomimetic cell culture environments and are thus key to the advances of modern biomedical research. The evolution of the physical and chemical properties has, furthermore, highlighted the potentials of microgels in the context of materials science and bioengineering. This review describes the recent research progress in the fabrication, characterization, and applications of microgels generated from biomolecular building blocks. A key enabling technology allowing the tailoring of the properties of microgels is their synthesis through microfluidic technologies, and this paper highlights recent advances in these areas and their impact on expanding the physicochemical parameter space accessible using microgels. This review finally discusses the emerging roles that microgels play in liquid–liquid phase separation, micromechanics, biosensors, and regenerative medicine.

Colloidal Polyelectrolyte Complexes from Hyaluronic Acid: Preparation and Biomedical Applications

“…[1] Under appropriate preparing conditions and depending on polyelectrolyte natures, such complexes can be elaborated as colloidal particles having submicronic size. [2,3] Although colloidal PECs are technically comparable to nanogels (NGs) owing to the 3D networks of physically bonded polyelectrolytes in their structures, [2,4,5] they have also been described with several other terms depending on personal perceptions of researchers, most commonly as nanoparticles (NPs), [6,7] Consequently, HA has been widely used for elaboration of colloidal PECs with various cationic polymers of different natures: chitosan (CTS) and diethylaminoethyl dextran (DEAE-D) as polysaccharides; poly-L-lysine (PLL) and polyarginine (PAR) as homopolypeptides; zein, protamine (PROT), lactoferrin (LF), whey protein isolate (WPI), feather keratin and bovine serum albumin as proteins; polyethylenimine (PEI) and poly(β-amino esters) (PBAE) as synthetic cationic polymers as well as their derivatives. Although the concept of colloidal PECs from HA has been described in the literature for more than a decade, it was not until 5 years ago did these systems start to be extensively investigated for drug delivery (see Tables 1 and 2), while there has been so far no comprehensive review on such specific materials.…”

“…[ 1 ] Under appropriate preparing conditions and depending on polyelectrolyte natures, such complexes can be elaborated as colloidal particles having submicronic size. [ 2,3 ] Although colloidal PECs are technically comparable to nanogels (NGs) owing to the 3D networks of physically bonded polyelectrolytes in their structures, [ 2,4,5 ] they have also been described with several other terms depending on personal perceptions of researchers, most commonly as nanoparticles (NPs), [ 6,7 ] nanocomplexes, [ 8,9 ] nanocomposites, [ 10,11 ] nanoassemblies [ 12 ] and coacervates. [ 13,14 ] Such colloidal systems, especially when prepared from biopolymers, have been extensively investigated due to their promising properties for numerous applications in biomedical fields.…”

“…[ 21 ] Besides such biorelevant aspects, the elaboration of biopolymer‐based PECs is also in accordance with green chemistry principles since their preparation process usually requires only gentle mixing of polyelectrolyte solutions at room temperature, which is a simple and rapid procedure without the need for chemical agents, surfactants, organic solvents or high mechanical or thermal energy. [ 1 5 ]…”

Bioprinting microporous functional living materials from protein-based core-shell microgels

“…Microgels have recently emerged as a new type of ink to fabricate 3D structures through extrusion printing 29,31,[34][35][36][37] . In a jammed state, they can form rest structures behaving as elastic solids through physical interactions such as frictions; when sheared, the interparticle frictions are dissipated to allow the ink to flow.…”

Aqueous microgels with engineered hydrophobic nano-domains

“…9 A broad variety of synthesis methods can be employed to synthesize functional microgels discussed in several publications. [9][10][11] Moreover a review on the general advances in the context of microgels and their fabrication was recently published by Xu et al 12 Temperature-responsive microgels are the most studied class of microgels in the literature owing to their simple applicability especially for many biological and medical applications. Even though there are more examples of temperature-responsive polymers the two main monomers This journal is © The Royal Society of Chemistry and IChemE 2022 applied in the synthesis of temperature-sensitive microgels are N-isopropylacrylamide (NiPAM), and N-vinylcaprolactam (VCL), which form polymer chains exhibiting a lower critical solution temperature (LCST).…”