TABLE 1.

List of recently published research using various types of natural and synthetic hydrogels for innovative single-cell microgel techniques.

Type	Hydrogel	Cross linking	Application	Reference
Natural	Alginate	Calcium release from EDTA complex	Controlled gelation of microgels for cell encapsulation	Utech et al. (2015)
		On-chip picoinjection of CaCl2	Picoinjection of CaCl2 for controlled gelation of microgels for cell encapsulation	Ahmed and Stokke, (2021)
		On-chip mixing of alginate with Ca chelators	Testing of different chelators for cell encapsulation in microgels	Shao et al. (2020)
		Competitive ligand exchange crosslinking	Cell encapsulation with increased gelation control and improved cell viability	Håti et al. (2016)
		Alginate + CaCl2 in oil phase	Monodisperse microgels for cell aggregate encapsulation	Wang et al. (2021)
	Agarose	Cooling below 18°C	Pairing of secreting cell with reporter cell and flow cytometric sorting	Yanakieva et al. (2020)
			Pairing of secreting cell with detection beads for flow cytometric measurement	Chokkalingam et al. (2013)
			Encapsulation of cells to monitor cell egress	Neubauer et al. (2019)
	Gelatin based	Cooling on ice and genipin addition	Monitoring single tumor-cell response to adherence on gelatin microgels	Nan et al. (2019)
		Off-chip UV exposure (GelMA)	Rapid generation of injectable stem cell-laden microgels fore tissue engineering	Zhao et al. (2016)
		On-Chip UV exposure (GelMA)	On-chip gelation and retrieval from oil phase for cell encapsulation	Mohamed et al. (2019)
			On-chip gelation and sorting into aqueous medium	Hong et al. (2012)
	Collagen based	Emulsification in the 37°C oil phase	On-chip gelation for cell encapsulation	Bavli et al. (2021)
		Heating to 37°C (Matrigel®)	Production of large monodisperse organoids for drug testing	Zhang et al. (2021)
			Production of endothelial cell organoids	Dolega et al. (2015)
Synthetic	PEG based	Mixing acrylated PEG with dextran	Production of semi-permeable shell capsules for multistep processing of large biomolecules	Leonaviciene et al. (2020)
		Mixing thiolated PEG with PEG-dimaleimide	Production of hydrogel beads with force-responsive fluorescence	Allazetta et al. (2017)
		Mixing vinylsulfone-PEG with thiol-PEG	Production of hydrogel beads with tunable stiffness and tunable RGD functionalization	Rahimian et al. (2019)
		Mixing maleimide-PEG with dithiotrietol	Production of semi-permeable hydrogel shells for immunoassays	Zhu, (2010)
		Mixing of PEGDT with MALDEX	Single-cell encapsulation for culture of clones and subsequent mRNA sequencing	Zhao et al. (2021)
		Mixing of thiol-hyaluronic acid with PEGDA	Monodisperse microgels for cell encapsulation with semi-permeable silica coating	Mazutis et al. (2013)
	Polyisocyanide	Heating to above 15°C	Prolonged encapsulation of adherent cells for culture with cell retrieval afterward due to thermoreversibility	Tiemeijer et al. (2021)