In vivo photoacoustic flow cytometry for early malaria diagnosis.

In vivo photoacoustic (PA) flow cytometry (PAFC) has already demonstrated a great potential for the diagnosis of deadly diseases through ultrasensitive detection of rare disease-associated circulating markers in whole blood volume. Here, we demonstrate the first application of this powerful technique for early diagnosis of malaria through label-free detection of malaria parasite-produced hemozoin in infected red blood cells (iRBCs) as high-contrast PA agent. The existing malaria tests using blood smears can detect the disease at 0.001-0.1% of parasitemia. On the contrary, linear PAFC showed a potential for noninvasive malaria diagnosis at an extremely low level of parasitemia of 0.0000001%, which is ∼10(3) times better than the existing tests. Multicolor time-of-flight PAFC with high-pulse repetition rate lasers at wavelengths of 532, 671, and 820 nm demonstrated rapid spectral and spatial identification and quantitative enumeration of individual iRBCs. Integration of PAFC with fluorescence flow cytometry (FFC) provided real-time simultaneous detection of single iRBCs and parasites expressing green fluorescence proteins, respectively. A combination of linear and nonlinear nanobubble-based multicolor PAFC showed capability to real-time control therapy efficiency by counting of iRBCs before, during, and after treatment. Our results suggest that high-sensitivity, high-resolution ultrafast PAFC-FFC platform represents a powerful research tool to provide the insight on malaria progression through dynamic study of parasite-cell interactions directly in bloodstream, whereas portable hand-worn PAFC device could be broadly used in humans for early malaria diagnosis. © 2016 International Society for Advancement of Cytometry.

Preclinical photoacoustic models: application for ultrasensitive single cell malaria diagnosis in large vein and artery.

In vivo photoacoustic flow cytometry (PAFC) has demonstrated potential for early diagnosis of deadly diseases through detection of rare circulating tumor cells, pathogens, and clots in nearly the entire blood volume. Before clinical application, this promising diagnostic platform requires verification and optimization using adequate preclinical models. We show here that this can be addressed by examination of large mouse blood vessels which are similar in size, depth and flow velocity to human vessels used in PAFC. Using this model, we verified the capability of PAFC for ultrasensitive, noninvasive, label-free, rapid malaria diagnosis. The time-resolved detection of delayed PA signals from deep vessels provided complete elimination of background from strongly pigmented skin. We discovered that PAFC's sensitivity is higher during examination of infected cells in arteries compared to veins at similar flow rate. Our advanced PAFC platform integrating a 1060 nm laser with tunable pulse rate and width, a wearable probe with a focused transducer, and linear and nonlinear nanobubble-amplified signal processing demonstrated detection of parasitemia at the unprecedented level of 0.00000001% within 20 seconds and the potential to further improve the sensitivity 100-fold in humans, that is approximately 106 times better than in existing malaria tests.