Spatiotemporal
control of cell–material interactions contributes
to our understanding of cell biology and the development of cell engineering.
Here, we first report the reversible and spatio-selective immobilization
of nonadherent cells through the use of photoswitchable polymeric
materials. The substrate coated with spiropyran-conjugated poly(ethylene
glycol) (PEG) lipids, which bind to cell membranes via the lipid moiety
only in their merocyanine form, enabled rapid cell immobilization
and release in an on–off manner by irradiation with ultraviolet
and visible light, respectively. Our work has the potential to improve
the performance of cell manipulations on chips and to enable rapid
cell arrangement/sorting on various surfaces.
Optimized photocleavable PEG-lipids tightly trapped cells on the substrate under highspeed flow conditions and released cells in a light-guided manner.
Versatile
methods for patterning multiple types of cells with single-cell
resolution have become an increasingly important technology for cell
analysis, cell-based device construction, and tissue engineering.
Here, we present a photoactivatable material based on poly(ethylene
glycol) (PEG)-lipids for patterning a variety of cells, regardless
of their adhesion abilities. In this study, PEG-lipids bearing dual
fatty acid chains were first shown to perfectly suppress cell anchoring
on their coated substrate surfaces whereas those with single-chain
lipids stably anchored cells through lipid–cell membrane interactions.
From this finding, a PEG-lipid with one each of both normal and photocleavable
fatty acid chains was synthesized as a material that could convert
the chain number from two to one by exposure to light. On the photoconvertible
PEG-lipid surface, cell anchoring was activated by light exposure.
High-speed atomic force microscopy measurements revealed that this
photocaging of the lipid–cell membrane interaction occurs because
the hydrophobic dual chains self-assemble into nanoscale structures
and cooperatively inhibit the anchoring. Light-induced dissociation
of the lipid assembly achieved the light-guided fine patterning of
multiple cells through local photoactivation of the anchoring interactions.
Using this surface, human natural killer cells and leukemia cells
could be positioned to interact one-by-one. The cytotoxic capacity
of single immune cells was then monitored via microscopy, showing
the proof-of-principle for applications in the high-throughput analysis
of the heterogeneity in individual cell–cell communications.
Thus, the substrate coated with our photoactivatable material can
serve as a versatile platform for the accurate and rapid patterning
of multiple-element cells for intercellular communication-based diagnostics.
Methods to label intercellular contact have attracted attention because of their potential in cell biological and medical applications for the analysis of intercellular communications. In this study, a simple and versatile method for chemoenzymatic labeling of intercellularly contacting cells is demonstrated using a cell‐surface anchoring reagent of a poly(ethylene glycol)(PEG)‐lipid conjugate. The surface of each cell in the cell pairs of interest were decorated with sortase A (SrtA) and triglycine peptide that were lipidated with PEG‐lipid. In the mixture of the two‐cell populations, the triglycine‐modified cells were enzymatically labeled with a fluorescent labeling reagent when in contact with SrtA‐modified cells on a substrate. The selective labeling of the contacting cells was confirmed by confocal microscopy. The method is a promising tool for selective visualization of intercellularly contacting cells in cell mixtures for cell‐cell communication analysis.
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