Chem 8157

Here are some questions about Yu-Shen's presentation.

1. Could somebody clarify the suggested use of PSA as a possible marker of breast cancer?

2. The paper mentions that they use water to release DNA from the nanoprobe? Why does DNA do not come off the nanoprobe prior to its release in Step 3? The other solutions are also aqueous.

3. What is the negative control used in these experiments?

2. They only use the pure D.I. water to dehybridize the dsDNA on the particle surface. For the other steps, they suspend the DNA and antibody anchored partcles in PBS solution. So I think the ionic stregth of solution might influence the dehybridization of the dsDNA. I was wondering that they might use hot D.I. water to dehybridize the dsDNA, but they didn't mention the details in the experimental procedure.
They suppose to use the hot water to dehybridize the double strand DNA more easily.

3. The negative control is adding these two particles probes to the PSA free PBS solution. So the magnetic particles will not bind with dye-labelled DNA polystyrene particles.
Then they did the same steps such as magnetic separation and fluorescence measurement.
So they find the fluorscence intensity is close to zero.

1. Called prostate specific antigen, PSA is now also found secreted by breast cancer tissues. There are two forms of PSA in serum, one is free PSA and the other is PSA complexed to the serine protease inhibitor a1-antichymotrypsin. The relative concentrations of these two forms are important variables to diagnose breast cancer. The percentage of free PSA in serum of female having breast cancer is five times higher than healthy women or women with benign breast diseases. Traditional method is to employ ELISA assays to detect total PSA and free PSA with 2 different pairs of monoclonal antibodies. The cross-reactivity is smaller than 5% while the specificity is very bigger than 96%. With the use of Fluorophore-based bio-barcode amplification assay it is possible to increase the detection limit considering the very low level of PSA in breast cancer subjects.

Reference: “Serum Total and Free Prostate-specific Antigen for Breast Cancer Diagnosis in Women1”, Clinical Cancer Research, Vol. 6, 467–473, February 2000

1) I found an additional paper by Sauter et. al. investigating possible breast cancer markers which could be tested before biopsy of tissue. It was discovered that PSA is a suitable biomarker. The papers discusses various accuracies/sensitivities and different levels of PSA for pre-menopausal women and post-menopausal women.

Reference: Sauter, E; Wagner-Mann, C; Ehya, H; Klein-Szato, A. Biologic markers of breast cancer in nipple aspirate fluid and nipple discharge are associated with clinical findings, Cancer Detect. Prev., 31(1), 2007, 50-58.

1) I found an additional paper by Sauter et. al. investigating possible breast cancer markers which could be tested before biopsy of tissue. It was discovered that PSA is a suitable biomarker. The papers discusses various accuracies/sensitivities and different levels of PSA for pre-menopausal women and post-menopausal women.

Reference: Sauter, E; Wagner-Mann, C; Ehya, H; Klein-Szato, A. Biologic markers of breast cancer in nipple aspirate fluid and nipple discharge are associated with clinical findings, Cancer Detect. Prev., 31(1), 2007, 50-58.