Ultrasensitive test for PSA in serum

Prostate-specific antigen (PSA) was tagged with titanium dioxide for determination in human serum by ICP MS at detection limits more than 2600 times lower than those of current ELISA and electrochemical methods. The diagnosis of prostate cancer using PSA is limited by the sensitivity of current methods but the new procedure, developed by Korean scientists at Dankook University, reduces the detection limit to 1.16 fg/mL. This is more than a million times lower than the PSA level regarded as a warning sign for prostate cancer.

In the first step, described in Journal of Analytical Atomic Spectrometry, magnetic nanoparticles that have been functionalised with the monoclonal immunoglobulin antibody for PSA were used to extract PSA from serum. These were mixed with titanium dioxide nanoparticles functionalised in the same way to form a sandwich-type complex. Finally, nitric acid was added to remove the magnetic nanoparticles leaving the titanium dioxide ones bound to PSA for measurement by ICP MS.

The ion corresponding to ⁴⁸Ti suffered multiple interferences from various ions like ⁴⁸Ca⁺ and ³²S¹⁶O⁺, so ⁴⁹Ti⁺ was selected for monitoring. Even so, background subtraction was required to remove the contribution of ³¹P¹⁸O⁺. The results are promising for a new PSA test but further work will be needed to negate the influence of the amounts of magnetic nanoparticles and immobilised antibody on the linear dynamic range.