Melanoma is the deadliest form of skin cancer, yet current diagnostic methods are unable to detect early onset of metastatic disease. Patients must wait until macroscopic secondary tumors form before malignancy can be diagnosed and treatment prescribed. Detection of cells that have broken off the original tumor and travel through the blood or lymph system can provide data for diagnosing and monitoring metastatic disease. By irradiating enriched blood samples spiked with cultured melanoma cells with nanosecond duration laser light, we induced photoacoustic responses in the pigmented cells. Thus, we can detect and enumerate melanoma cells in blood samples to demonstrate a paradigm for a photoacoustic flow cytometer. Furthermore, we capture the melanoma cells using microfluidic two phase flow, a technique that separates a continuous flow into alternating microslugs of air and blood cell suspension. Each slug of blood cells is tested for the presence of melanoma. Slugs that are positive for melanoma, indicated by photoacoustic waves, are separated from the cytometer for further purification and isolation of the melanoma cell. In this paper, we evaluate the two phase photoacoustic flow cytometer for its ability to detect and capture metastastic melanoma cells in blood.
Metastasis is a life threatening complex physiological phenomenon that involves the movement of cancer cells from one
organ to another by means of blood and lymph. An understanding about metastasis is extremely important to device
diagnostic systems to detect and monitor its spread within the body. For the first time we report rapid photoacoustic
detection of the induced metastatic melanoma in mice in vitro using photoacoustic flowmetry.
A new photoacoustic flow system is developed, that employs photoacoustic excitation coupled with an ultrasound
transducer capable of determining the presence of individual, induced mouse melanoma cells (B16/F10) within the
circulating system in vitro. Tumor was induced in mice by injecting mouse melanoma cells through tail vein into the
C57BL/6 mice. A luciferase based in vivo bioluminescence imaging is performed to confirm the tumor load and multiple
metastases in the tumor-induced mice. 1ml of blood obtained through cardiac puncture of the induced metastasized mice
was treated to lyse the red blood cells (RBC) and enriched, leaving the induced melanoma in the peripheral blood
mononuclear suspension (PBMC). A photoacoustic flowsystem coupled with an ultrasound transducer is used to detect
the individual circulating metastatic melanoma cells from the enriched cell suspension.
Melanoma is the deadliest form of skin cancer, yet current diagnostic methods are inadequately sensitive. Patients
must wait until secondary tumors form before malignancy can be diagnosed and treatment prescribed. Detection of
cells that have broken off the original tumor and flow through the blood or lymph system can provide data for
diagnosing and monitoring cancer. Our group utilizes the photoacoustic effect to detect metastatic melanoma cells,
which contain the pigmented granule melanin. As a rapid laser pulse irradiates melanoma, the melanin undergoes
thermo-elastic expansion and ultimately creates a photoacoustic wave. Thus, melanoma patient's blood samples can
be enriched, leaving the melanoma in a white blood cell (WBC) suspension. Irradiated melanoma cells produce
photoacoustic waves, which are detected with a piezoelectric transducer, while the optically transparent WBCs
create no signals. Here we report an isolation scheme utilizing two-phase flow to separate detected melanoma from
the suspension. By introducing two immiscible fluids through a t-junction into one flow path, the analytes are
compartmentalized. Therefore, the slug in which the melanoma cell is located can be identified and extracted from
the system. Two-phase immiscible flow is a label free technique, and could be used for other types of pathological
Our recent efforts are to develop a system for the detection of extremely low number of prostate
cancer cells tagged to gold nanorods. Such a system provides an attractive platform to detect the
early metastasis. By monitoring the metastatic prostate cancer cells, the physicians are provided
with more time to act and design the treatment and also provide better hope for the prostate
cancer patients. We developed an optical flowmetry system which employs photoacoustic
excitation coupled with an optical transducer capable of determining the presence of cells within
the circulating system in vitro.The particles were tagged to gold nanoparticles at Dr.Katti's lab.
This provided the required optical contrast to detect the individual prostate cancer cells.
Detection trials resulted in a detection threshold of the order of a couple of individual cells in the
detection volume, thus validating the effectiveness of the proposed mechanism.