PubMed · 14704776
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Jesper Glückstad. 2004. Microfluidics: Sorting particles with light.. https://doi.org/10.1038/nmat1041
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BACKGROUND: Flow cytometry is the standard method for the multi-parametric analysis of cells. However, for about a decade, an instrument has been available which analyses fluorescing cells immobilised on slides called a laser scanning cytometer (LSC). Its design, according to the principles of slide-based cytometry, promises many advantages, especially in the analysis of minimal sample volumes. METHODS AND PATIENTS: To date, applications for cultured cells and animal models have been established. Its use for clinical purposes, however, remains to be critically evaluated. We analysed a variety of specimens obtained in our clinical routine. RESULTS: First, the instrument's resolution was evaluated using standardised particles. This showed a very good sensitivity across a wide range of fluorescence intensities at various wavelengths. Next, diverse applications for tissue engineering, immunophenotyping, and ENT-oncology were tested. Considering its microanalytical capacities, LSC proved to be a convincing tool for clinical use. Additionally, complex structures such as bi-layers of cultured cells were analysed. CONCLUSION: A broad spectrum of applications in clinical practice and research for the LSC is evident.
Although the addition of just the excitation light field at the focus, or of just the fluorescence field at the detector is sufficient for a three- to fivefold resolution increase in 4Pi-fluorescence microscopy, substantial improvements of its optical properties are achieved by exploiting both effects simultaneously. They encompass not only an additional expansion of the optical bandwidth, but also an amplified transfer of the newly gained spatial frequencies to the image. Here we report on the realization and the imaging properties of this 4Pi microscopy mode of type C that also is the far-field microscope with the hitherto largest aperture. We show that in conjunction with two-photon excitation, the resulting optical transfer function displays a sevenfold improvement of axial three-dimensional resolution over confocal microscopy in aqueous samples, and more importantly, a marked transfer of all frequencies within its inner region of support. The latter is present also without the confocal pinhole. Thus, linear image deconvolution is possible both for confocalized and nonconfocalized live-cell 4Pi imaging. Realized in a state-of-the-art scanning microscope, this approach enables robust three-dimensional imaging of fixed and live cells at approximately 80 nm axial resolution.
A mass analyzer based on a rectilinear geometry ion trap (RIT) has been built, and its performance has been characterized. Design concepts for this type of ion trap are delineated with emphasis on the effects of electrode geometry on the calculated electric field. The Mathieu stability region was mapped experimentally. The instrument can be operated using mass-selective instability scans in both the boundary and resonance ejection versions. Comparisons of performance between different versions of the device having different dimensions allowed selection of an optimized geometry with an appropriate distribution of higher-order electric fields. Comparisons made under the same conditions between the performance of a conventional cylindrical ion trap and a RIT of 4 times greater volume show an improvement of 40 times in the signal-to-noise ratio resulting from the higher ion trapping capacity of the RIT. The demonstrated capabilities of the RIT include tandem mass spectrometry, a mass resolution in excess of 1000, and a mass/charge range of 650 Th, all in a simple structure that is only 3.5 cm(3) in internal volume.