2021 年 59 巻 4-5 号 p. 95-103
Laser microdissection (LMD) is a method for isolating a specific region of a tissue sample or a specific cell using an ultraviolet (UV) laser beam under a microscope. Various biomolecules, such as nucleic acids and protein molecules, can be purified and extracted from isolated biological specimens, which can be used for molecular biological analysis. The laser beam scan on the sample plane to cut out arbitrary areas of the target sample has been conventionally performed using an XY motorized stage or a set of two deflection prisms. In addition to the usability of these conventional laser scanning components, there is a concern about thermal damage to the sample caused by UV laser irradiation. This paper reports on the development of microelectromechanical system (MEMS) mirror-type LMD instrumentation for reducing thermal damage by high-speed laser scanning. We compare the laser deflection components used in the two major laser scanning methods:raster and vector scans. Then, we detail the operating principle of the electrostatic-type MEMS mirror used in this study and the development of our instrumentation. The MEMS mirror deflection (non-resonant mode) is controlled by a vector scan operation and is not synchronized with laser pulse irradiation. The developed instrumentation demonstrates a high-speed laser scan, which is several tens of times faster than that of conventional LMD instrumentation. We then demonstrate the LMD of a pig heart muscle slice and confirm that a higher laser pulse rate lowered the number of scans required to complete the LMD. Further, we discuss the laser irradiation-induced thermal damage to the target tissue in association with the scan speed and describe the simulation performed to estimate the number of laser scans to complete microdissection by varying the laser scan speed and repetition rate. The simulation results indicate that our instrumentation affords LMD with reduction in sample thermal damage and minimizes the number of laser scans and the process time. The characteristics of the instrumentation, including the ability to reduce sample thermal damage, a compact and simple structure, unitization capability, high compatibility with optical microscopy, and cost effectiveness offer an attractive alternative to conventional, commercially available LMD instrumentation.