Photoacoustic flow cytometry

Abstract

Conventional flow cytometry using scattering and fluorescent detection methods has been a fundamental tool of biological discoveries for many years. Invasive extraction of cells from a living organism, however, may lead to changes in cell properties and prevents the long-term study of cells in their native environment. Here, we summarize recent advances of new generation flow cytometry for in vivo noninvasive label-free or targeted detection of cells in blood, lymph, bone, cerebral and plant vasculatures using photoacoustic (PA) detection techniques, multispectral high-pulse-repetition-rate lasers, tunable ultrasharp (up to 0.8 nm) rainbow plasmonic nanoprobes, positive and negative PA contrasts, in vivo magnetic enrichment, time-of-flight cell velocity measurement, PA spectral analysis, and integration of PA, photothermal (PT), fluorescent, and Raman methods. Unique applications of this tool are reviewed with a focus on ultrasensitive detection of normal blood cells at different functional states (e.g., apoptotic and necrotic) and rare abnormal cells including circulating tumor cells (CTCs), cancer stem cells, pathogens, clots, sickle cells as well as pharmokinetics of nanoparticles, dyes, microbubbles and drug nanocarriers. Using this tool we discovered that palpation, biopsy, or surgery can enhance CTC release from primary tumors, increasing the risk of metastasis. The novel fluctuation flow cytometry provided the opportunity for the dynamic study of blood rheology including red blood cell aggregation and clot formation in different medical conditions (e.g., blood disorders, cancer, or surgery). Theranostics, as a combination of PA diagnosis and PT nanobubble-amplified multiplex therapy, was used for eradication of CTCs, purging of infected blood, and thrombolysis of clots using PA guidance to control therapy efficiency. In vivo flow cytometry using a portable fiber-based devices can provide a breakthrough platform for early diagnosis of cancer, infection and cardiovascular disorders with a potential to inhibit, if not prevent, metastasis, sepsis, and strokes or heart attack by well-timed personalized therapy.

In vivo cell characteristic extraction and identification by photoacoustic flow cytography

“…3(a), 3(b) and 3(c) respectively. RBCs were 6-7 μm in diameter, and suspended melanoma cells were larger, 10-20 μm in diameter, which were consistent with previous work [11,12]. The adherent melanoma cells grown on glass were visible highlighted, that's because abundant melanin in cells lead to higher PA signals.…”

“…Sickle-cell anemia as one of hematologic diseases has an abnormal sickle-like shape of RBCs and an average volume of a red blood corpuscle below normal range [25,26]. The photoacoustic flow cytography system with the cells properties including shape, size and light absorption intensity, can be a valid means to distinguish RBCs and calculate mean cell volume for label-free and noninvasively auxiliary diagnosis of the disease [11,[27][28][29].…”

“…And acoustic waves with much longer wavelengths, are resistant to scattering and attenuation in biological media. PAFC can be applied to in vivo, label-free, and noninvasive monitor melanoma CTCs [9][10][11][12]. However, the PAFC is based on analyzing the overall PA signal excited by a linear configuration laser beam.…”

“…However, the PAFC is based on analyzing the overall PA signal excited by a linear configuration laser beam. On account of cells aggregation and various absorbers under the illumination, the difficulty in distinguishing active PA signals may easily lead to misidentification and false negatives of cells [11,12]. An improved technique capable of accurately identifying cell types is desiderated in the field of cell analysis.…”

Linear-array-based photoacoustic tomography for label-free high-throughput detection and quantification of circulating melanoma tumor cell clusters

“…Photoacoustic flow cytometry enables long-term monitoring of melanoma CTCs in vivo. However, these sensing techniques provide inadequate spatial resolution to further characterize melanoma CTCs 20 . The microscopic implementation of PAT, optical-resolution photoacoustic microscopy (OR-PAM), images single melanoma CTCs in the blood flows with high spatial-temporal resolution 21 .…”