Low-Power Two-Color Stimulated Emission Depletion Microscopy for Live Cell Imaging

Low-power compact continuous-wave stimulated emission depletion microscopy

Stimulated emission depletion (STED) microscopy can break the optical diffraction barrier and provide subdiffraction resolution. According to the STED superresolution imaging principle, the resolution of STED is positively related to the power of the depletion laser. However, high-laser power largely limits the study of living cells or living bodies. Moreover, the high complexity and high cost of conventional pulsed STED microscopy limit the application of this technique. Therefore, this paper describes a simple continuous-wave STED (CW-STED) system constructed on a 45 × 60 cm breadboard and combined with digitally enhanced (DE) technology; low-power superresolution imaging is realized, which has the advantages of reducing system complexity and cost. The low-system complexity, low cost, and low-power superresolution imaging features of CW-STED have great potential to advance the application of STED microscopy in biological research.

Ultralow Laser Power Three-Dimensional Superresolution Microscopy Based on Digitally Enhanced STED

The resolution of optical microscopes is limited by the optical diffraction limit; in particular, the axial resolution is much lower than the lateral resolution, which hinders the clear distinction of the three-dimensional (3D) structure of cells. Although stimulated emission depletion (STED) superresolution microscopy can break through the optical diffraction limit to achieve 3D superresolution imaging, traditional 3D STED requires high depletion laser power to acquire high-resolution images, which can cause irreversible light damage to biological samples and probes. Therefore, we developed an ultralow laser power 3D STED superresolution imaging method. On the basis of this method, we obtained lateral and axial resolutions of 71 nm and 144 nm, respectively, in fixed cells with 0.65 mW depletion laser power. This method will have broad application prospects in 3D superresolution imaging of living cells.

Multi-Color Two-Photon Microscopic Imaging Based on a Single-Wavelength Excitation

Two-photon probes with broad absorption spectra are beneficial for multi-color two-photon microscopy imaging, which is one of the most powerful tools to study the dynamic processes of living cells. To achieve multi-color two-photon imaging, multiple lasers and detectors are usually required for excitation and signal collection, respectively. However, one makes the imaging system more complicated and costly. Here, we demonstrate a multi-color two-photon imaging method with a single-wavelength excitation by using a signal separation strategy. The method can effectively solve the problem of spectral crosstalk by selecting a suitable filter combination and applying image subtraction. The experimental results show that the two-color and three-color two-photon imaging are achieved with a single femtosecond laser. Furthermore, this method can also be combined with multi-photon imaging technology to reveal more information and interaction in thick biological tissues.