Chromatographic characterization of amino acid profiles in urinary samples of patients suffering from prostate carcinoma
Abstract
Objective: The aim of our study was to prepare a protocol for pre-treatment of clinical urinary samples, subsequently employed for acquirement of amino acid profiles via ion exchange chromatography with detection in visible spectrum (IEC/ Vis). Further for clinically interesting biomolecules as sarcosine and taurine the optimization was carried out to shorten the analysis time.
Design: Methodological Material and methods: Urine specimens from patients diagnosed with prostate cancer (n = 500) were collected within 1 year and stored in -80oC. Samples were processed for analysis of amino acid profiles through acidic hydrolysis in a microwave reactor.
Using optimized conditions (80 W, 120oC, 25 bar, 105 min), 500 μL sample, mixed with 500 μL of 35% hydrochloric acid hydrolyzed. That resulted in product, which was subsequently diluted in buffer of sodium cycle (0.2 mol/L NaCl, 60 C6H807 mmol/L, 1.5 mmol/L and 0.4% N3Na S(CH2CH2OH)2).
After centrifugation (25000 g at 4oC, 20 min), the samples were neutralized (0.6 mol/l NaOH) and analyzed using ion-exchange liquid chromatography with post-column derivatization with ninhydrin, using the detection wavelength λ = 440 and 570 nm (IEC/Vis). For analysis of sarcosine and taurine, the samples were prepared by evaporation of 250 μL of sample employing a nitrogen evaporator (40 min, temperature 60oC.
Nitrogen pressure of 1 bar) and resuspended with buffer of sodium cycle (250 μL). Results and conclusion: The analyses of amino acid profiles offer interesting clinical information not only in non-invasively collected urinary samples, but also in other organic matrices.
Employment of nitrogen evaporator for sample pre-treatment leads to reduction of manipulation with sample and its combination with shortened analyses times of sarcosine and taurine may serve as a sensitive and low-cost method for analysis of clinical specimens.