David Maraldo, Chemical and Biological Engineering, Drexel University, 32nd and Chestnut St., Philadelphia, PA 19104, Fernando Garcia, Dept of Pathology and Laboratory Medicine, Drexel University, 32nd and Chestnut St., Philadelphia, PA 19104, and Raj Mutharasan, Department of Chemical and Biological Engineering, Drexel University, 32nd and Chestnut St., Philadelphia, PA 19104.
We describe a macrocantilever-based method for detecting a prostate cancer biomarker (alpha-methylacyl-CoA racemase; AMACR) directly in patient urine without a sample preparation step and without the use of labeled reagents. Clean catch voided urine specimens were prospectively collected from five confirmed prostate cancer patients 3 weeks post biopsy. The presence of AMACR was measured in a blinded manner by exposing 3-mL of urine to the anti-AMACR immobilized piezoelectric-excited millimeter-sized (PEMC) sensor. The resonance frequency of PEMC decreases as AMACR from sample binds to the antibody on the sensor. The resonance frequency changes for the five patients tested were 4,314+/-35 (n=2), 269 +/-17 (n=2), 977 +/-64 (n=3), 600 +/-31 (n=2), and 801+/-81 (n=2) Hz, respectively. Positive detection was observed within ~ 15 minutes. The responses to positive, negative, and buffer controls were -9 +/-13, -34+/-18 Hz and -6+/-18 Hz, respectively. Positive verification of AMACR attachment was confirmed by low-pH buffer release. The sensor response was quantitatively related to AMACR concentration in control urine, and the relationship was used in developing an in situ calibration method for quantifying AMACR in patient urine. Estimated concentrations of 42, 2, and 3 fg/mL AMACR were calculated for the three patient urine, while absence of AMACR was confirmed in control urine (n=13). Because of simplicity of measurement is combined with high sensitivity and specificity, the method may be an useful adjunct in a point-of-care setting to identify men at increased risk for prostate cancer.