Dynamic measurements of flowing cells labeled by gold nanoparticles using full-field photothermal interferometric imaging

Abstract

We present highly dynamic photothermal interferometric phase microscopy for quantitative, selective contrast imaging of live cells during flow. Gold nanoparticles can be biofunctionalized to bind to specific cells, and stimulated for local temperature increase due to plasmon resonance, causing a rapid change of the optical phase. These phase changes can be recorded by interferometric phase microscopy and analyzed to form an image of the binding sites of the nanoparticles in the cells, gaining molecular specificity. Since the nanoparticle excitation frequency might overlap with the sample dynamics frequencies, photothermal phase imaging was performed on stationary or slowly dynamic samples. Furthermore, the computational analysis of the photothermal signals is time consuming. This makes photothermal imaging unsuitable for applications requiring dynamic imaging or real-time analysis, such as analyzing and sorting cells during fast flow. To overcome these drawbacks, we utilized an external interferometric module and developed new algorithms, based on discrete Fourier transform variants, enabling fast analysis of photothermal signals in highly dynamic live cells. Due to the self-interference module, the cells are imaged with and without excitation in video-rate, effectively increasing signal-to-noise ratio. Our approach holds potential for using photothermal cell imaging and depletion in flow cytometry.

Super-resolution three-dimensional fluorescence and optical diffraction tomography of live cells using structured illumination generated by a digital micromirror device

“…The RI distribution of live cells has provided structural and biochemical information about biological samples in studies in the fields of cell biology [22,23], microbiology [24], hematology [25], infectious diseases [26], and biophysics [27]. Nonetheless, the RI generally provides limited molecular specificity [28], except for certain materials with distinct RI values such as lipids [29,30] and metallic particles [31,32].…”

Compensation of aberration in quantitative phase imaging using lateral shifting and spiral phase integration

“…Employing the principle of interferometric imaging, QPI measures the phase retardation induced by a sample, from which 2D phase delay maps or 3D refractive index (RI) tomograms of the sample can be retrieved. Due to its non-destructive, label-free, and quantitative imaging capability [3], QPI has been widely used for study in various biological and medical fields, including hematology [4,5], immunology [6], neuroscience [7][8][9], cell biology [10,11], microbiology [12], histopathology [13,14], and nanotechnology [15][16][17].…”