Synthesis of a removable cytoprotective exoskeleton by tea polyphenol complexes for living cell encapsulation

Cell encapsulation is a chemical tool for endowing living cells with exogenous properties and enhancing their in vitro tolerance against lethal factors, which has shown promising prospects and potential applications in many fields such as cell transplantation, drug delivery, and tissue engineering. One-pot precipitation of a polyphenol–metal complex on cells protects cells from UV irradiation and lytic enzymes. However, the involvement of metal ions brings side effects on cell viability and growth. Moreover, an external removal agent is needed for cell division and growth. Herein, a polymer shell composed of hydrogen bonded constituents without affecting cell viability and growth by the precipitation of tea polyphenol and polyvinyl pyrrolidone is reported. The formation of the polymer shell was verified by the Au nanoparticle’s laser scanning confocal reflectance and quartz crystal microbalance measurement. The thickness of the shell was managed by the concentration of the complex. When exposed to UV irradiation for 15 or 30 min, polymer-coating-protected Saccharomyces cerevisiae (yeast) had much higher cell viability than the native one. Exposed to a high temperature environment (60 °C), most of the coated yeasts survived in contrast to uncoated ones. For the cell division and growth curve, the polymer coating with various thicknesses had no difference to the native one, which indicated no suppression of cell growth and no external side effects involved. As applied to mammalian HeLa cells under UV irradiation for 15 min, the coated cells had an obvious higher cell viability than that of untreated ones. Therefore, the tea polyphenol–poly(vinylpyrrolidone) shell is a versatile tool for chemically controlling the external properties of cells without side effects on cell viability and growth.