Cell‐Surface Engineering by a Conjugation‐and‐Release Approach Based on the Formation and Cleavage of Oxime Linkages upon Mild Electrochemical Oxidation and Reduction

Abstract

We report a strategy to rewire cell surfaces for the dynamic control of ligand composition on cell membranes and the modulation of cell-cell interactions to generate three-dimensional (3D) tissue structures applied to stem-cell differentiation, cell-surface tailoring, and tissue engineering. We tailored cell surfaces with bioorthogonal chemical groups on the basis of a liposome-fusion and -delivery method to create dynamic, electroactive, and switchable cell-tissue assemblies through chemistry involving chemoselective conjugation and release. Each step to modify the cell surface: activation, conjugation, release, and regeneration, can be monitored and modulated by noninvasive, label-free analytical techniques. We demonstrate the utility of this methodology by the conjugation and release of small molecules to and from cell surfaces and by the generation of 3D coculture spheroids and multilayered cell tissues that can be programmed to undergo assembly and disassembly on demand.

Polyvalent Display of Biomolecules on Live Cells

“…Development of micro-scale tissue constructs holds great potential for biomedical applications such as tissue engineering and drug screening. [28–31] For instance, the co-culture of stem cells and chondrocytes has been studied to promote chondrogenesis. [32] Thus, we stained type II collagen and aggrecan, two major markers of chondrogenesis.…”

Programming Cell-Cell Interactions through Non-genetic Membrane Engineering

“…Similarly, when hMSCs and fibroblasts were modified with hydroquinone and oxyamine groups, respectively, the formation of cell clusters could be induced by chemical or electrochemical oxidation of the hydroquinone to a reactive quinone moiety, which then coupled to oxyamine-labeled cells. The cell clustering could then be reversed via reduction of the quinone back to a hydroxyquinone (Pulsipher et al, 2014). Unfortunately, neither of these reversal mechanisms – photocleavage or electrochemical reduction – are currently applicable to in vivo applications.…”

“…Genetically encoded modifications have met little success in the arena of stem cells, as the genetic manipulation typically causes a decrease in pluripotency (Rombouts and Ploemacher, 2003). However, non-genetic approaches – including hydrophobic insertion (Dennis et al, 2004; Ko et al, 2009), chemical modification (Cheng et al, 2012a), liposome fusion (Pulsipher et al, 2014), metabolic engineering (Du and Yarema, 2010), and enzymatic remodeling (Merzaban et al, 2015) – have been successfully applied to stem and progenitor cell populations without altering their multi-lineage differentiation capabilities. Consequently, these non-genetic approaches, which don’t typically rely upon the engagement of a physiologic receptor on the cell membrane, may be uniquely suited to directed stem cell therapies.…”

“…For example, the introduction of photoisomerizable (Shi et al, 2016) and photocleavable (Luo et al, 2014) groups into the modifications has allowing their removal upon UV irradiation. Electrochemical reversibility has also been demonstrated, with the formation and cleavage of oxime linkages reliant upon oxidation and reduction, respectively (Pulsipher et al, 2014). Additionally, several groups have utilized temperature as a stimulus via thermally-reversible polymers (Amaral and Pasparakis, 2015), oligonucleotides (Gartner and Bertozzi, 2009), and aptamers (Altman et al, 2013).…”

Controlled Detachment of Chemically Glued Cells

“…Yousaf group used oxime-hydroquinone chemistry that can reversibly degrade via electrochemical stimuli. 9 Although this technique is useful for two-dimensional cell patterning, electronic signal requires special plates, such as gold surface, and cannot be easily applied in vivo . Wagner group developed a genetic engineering-based method that forms cell-cell assembly by recombinant fusion protein of dihydrofolate reductase inhibitor methotrexate and disintegrates by treatment of trimethoprim, a bacterial dihydrofolate reductase inhibitor.…”