Antibodies modified by gold nanoparticles or quantum dots for specific detection of sarcosine on the membrane: Use in rapid diagnostics
Abstract
Paper tests are very cheap and fast diagnostic tools for self-testing in a wide range of health problems. Thus, the diagnostics of tumor development is of a great medical and socio-economic significance.
Malignant prostate cancers are the most common malignancy in men. Procedures have been developed to diagnose this disease based on the monitoring of tumor marker molecules.
Most commonly, PSA and fPSA are used. Although these tumor markers are significantly increased, the cancer at the biopsy is not always confirmed.
Thus, the finding of other marker molecules is urgently needed. Recent studies have shown that changes in content of the amino acid sarcosine are associated with prostate tumours.
Polyclonal chicken antibodies against sarcosine (AntiSar) were prepared. AntiSar antibodies were labelled with gold nanoparticles Au20 (size 20-30 nm, zeta potential - 38 mV) and CdTe QDs (emission 530 green QDs and 650 nm yellow QDs).
Dot blot and flow lateral chromatography were used to develop a newly designed sarcosin detection procedure. The aggregation or fluorescence intensities were evaluated by newly designed software.
Sarcosine was analysed in a concentration range (0-150 mu M) in PBS, artificial urine and urine sample buffer. The calibration curves obtained in the concentration range (0-12 mu M) were strictly linear (R-2 = 0.99) with a relative error of 10%.
Using the proposed methods sarcosine concentrations as low as 250-500 nM were analysed. Moreover, the results obtained show a higher sensitivity (by 20-40%) of sarcosine detection using QDs in comparison with using gold nanoparticles.