Selective and rapid cell injection of fluorescence sensor encapsulated in liposome using optical control of zeta potential and local mechanical stimulus by optical tweezers

We developed selective and rapid injection of fluorescence sensor into the cell for intracellular measurement. The sensor encapsulated in the liposome contains photochromic chemical, 1, 3, 3-Trimethylindolino-6´- nitrobenzopyrylospiran, for optical control of zeta potential. The molecular structure of spiropyran changes between spiropyran type and merocyanine type by UV/VIS illumination. Zeta potential of merocyanine type is higher than that of spiropyran type. The charge of the liposomes are normally negative. Zeta potential of the liposome is switched from negative to positive by photoisomerization of spiropyran. Positive-charged liposome manipulated by optical tweezers adheres to the cell membrane by electrostatic force since the charge of the cell membrane is negative. The local vibration stimulus using optical tweezers is applied to the cell membrane for rapid injection of the sensor by membrane fusion and endocytosis. We demonstrated selective adhesion of the liposome to the cell membrane by optical control of zeta potential (adhesion rate: 71%). Moreover, we also demonstrated rapid injection of 1 μmφ fluorescence sensor (approximately 30 minutes, injection rate: 100%) into a cell using local vibration stimulus by optical tweezers.