A Microgel Construction Kit for Bioorthogonal Encapsulation and pH‐Controlled Release of Living Cells

Abstract

pH-Cleavable cell-laden microgels with excellent long-term viabilities were fabricated by combining bioorthogonal strain-promoted azide-alkyne cycloaddition (SPAAC) and droplet-based microfluidics. Poly(ethylene glycol)dicyclooctyne and dendritic poly(glycerol azide) served as bioinert hydrogel precursors. Azide conjugation was performed using different substituted acid-labile benzacetal linkers that allowed precise control of the microgel degradation kinetics in the interesting pH range between 4.5 and 7.4. By this means, a pH-controlled release of the encapsulated cells was achieved upon demand with no effect on cell viability and spreading. As a result, the microgel particles can be used for temporary cell encapsulation, allowing the cells to be studied and manipulated during the encapsulation and then be isolated and harvested by decomposition of the microgel scaffolds.

Charge-conversional and reduction-sensitive poly(vinyl alcohol) nanogels for enhanced cell uptake and efficient intracellular doxorubicin release

“…In the past decade, a tremendous effort has been directed to develop intelligent drug nanocarriers that release their payload in response to intrinsic intracellular signals, particularly to endosomal/lysosomal pH and cytoplasmic glutathione (GSH) [24][25][26]. Polymeric components with pH-sensitive groups (pH-induced protonation/deprotonation or degradation) are used to produce drugformulation nanosystems that are relatively stable in the circulation but also have the ability to rapidly release the entrapped drugs in the tumor tissue (pH 6.8) as well as in the intracellular compartments, such as endosomes (pH 5.5-6) and lysosomes (pH 4.5-5.0) of cells [27][28][29]. Following escape from the endosome and by taking advantage of the high redox potential in cytoplasms and nuclei of cancer cells, which have much higher concentration of reducing glutathione (GSH) tripeptide than body fluids and extracellular milieu (0.5-10 mM versus 2-20 μM GSH), reduction-sensitive nanosystems containing S-S bonds have been designed and exploited for active cytoplasmic release of various potent chemotherapeutics [30][31][32].…”

Cytocompatible in situ forming chitosan/hyaluronan hydrogels via a metal-free click chemistry for soft tissue engineering

“…For the metal-free click reaction, chitosan and hyaluronan were modified with oxanorbor- 30 nadiene (OB) and 11-azido-3,6,9-trioxaundecan-1-amine (AA), respectively. The gelation is attributed 31 to the triazole ring formation between OB and azido groups of polysaccharide derivatives. The molecular 32 structures were verified by FT-IR spectroscopy and elemental analysis, giving substitution degrees of 58% 33 and 47% for chitosan-OB and hyaluronan-AA, respectively.…”

“…Typically, 1,3-dipolar cyclo-addition cat-64 alyzed by Cu (I) can be accomplished with high efficiency, 65 reliability, and no by-products under the physiological condition 66 [21][22][23][24][25][26][27][28][29]. Some macromolecular derivatives, such as poly(vinyl 67 alcohol) (PVA) [18], polyethylene glycol (PEG) [21,23,26,28] and 68 hyaluronan [20,27] [31,32]. Presently, the SPPC has been employed to graft bioactive 86 peptides to PEG hydrogels for molecular patterning [33,34].…”

Soft PEG‐Hydrogels with Independently Tunable Stiffness and RGDS‐Content for Cell Adhesion Studies

“…The broad applicability of these materials was demonstrated by successful cell culturing of a range of cells, such as fibroblasts, human mesenchymal stem cells, and bone marrow derived stromal cells. [30][31][32][33] When culturing cells on hydrogels, it is important to understand how they interact with their surroundings. It has been stated that cells are able to feel the substrate they are attached to and that they will respond based on these external mechanical signals.…”

“…[34,35] For example, it has been shown that the differentiation of mesenchymal stem cells is dependent on substrate stiffness. Culturing on soft gels (0.1-1 kPa) led to neurons, but myoblasts were formed on stiffer substrates (8)(9)(10)(11)(12)(13)(14)(15)(16)(17) and cells differentiated into osteoblasts on rigid matrices (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). [36] Recent research indicates that these stem cells retain their phenotype on a non-fouling zwitterionic hydrogel, independent of stiffness.…”