Intracellular Sensing Based On Whispering Gallery Mode Microcavity

Whispering gallery mode(WGM)microcavity has a high quality factor and small mode volume,which can strongly enhance light-matter interactions.It is extremely sensitive to changes in the external environment,making them an excellent platform for various sensing applications.The WGM microcavity can realize the low limit detection of biochemical molecules without labeling,which has a widely application prospect.This paper studies the high sensitivity sensing detection of WGM microcavity by using dye droped microspheres.The main work includes follows:(1)An optical system has been created which can realize stimulation of WGM microsphere doped with DG,signal transmission and collection,and microscopic imaging simultaneously.It proved that the feasibility of optical system when we successfully detected the calcium ion concentration with a DG microsphere.Finally,we stimulated the intracellular DG microspheres and realized the recognition of cell types according to the WGMs in different cells.(2)A method of Fluorescence Resonant Energy Transfer(FRET)was proposed to enhance WGM microcavity sensing.DG and Rhodamine 6G(R6G)in the system transfer energy through FRET,and the laser of both DG and R6 G can be realized simultaneously under 473 nm laser.It is observed that the center peaks of the DG and R6 G laser depended on the concentration of R6 G.By plotting the frequency shiftstandard concentration curve,the lowest detection concentration was calculated to be 4.04 n M.This detection limit is four orders of magnitude lower than without FRET.It was found that the laser wavelength of DG and R6 G was also dependent on the concentration of R6 G when lase the intracellular FRET-WGM system.By measuring the peaks distance between the two groups in the cell,the concentration of R6 G molecule in the cell was calculated according to the fitting formula of the distance between the two peaks outside the cell.(3)A kind of Green microsphere array(Firefly Green,FG)was prepared,which can be excited WGM laser in the optical system.The WGM resonator may be a polygon structure according to the free spectrum range of FG laser.On this basis,the WGM of the hybrid array of FG microspheres and Nile Red(NR)microspheres was investigated.Due to special spectral properties of the FG and NR,they can make a good pair of FRET.The laser of FG and NR was realized simultaneously under 473 nm laser in the prepared regular microsphere array.The WGM microcavity and FRET-WGM system studied in this paper are of great significance for the real-time detection of the environment within single cells and the development of cell lasers.