Identification of BRCA1 gene mutation variants in clinical samples without labeling step – comparison of functionality and sensitivity of SPR and SERS sensors

SERS (surface-enhanced Raman scattering) and SPR (surface plasmon resonance) sensors for the identification of six the most popular in Poland variants of BRCA1 gene mutation without labelling have been constructed and tested with clinical samples. Both sensors were based on the selective hybridization of target DNA with the capture DNA immobilized on plasmonic substrates. Moreover, in both sensors the same thiolated capture DNA was used. The mutation identification process using SPR detector relied on the shape of the SPR sensorgrams, whereas for the SERS sensors, the intensity of the Raman band at about 715-735 cm-1 (this band is due to the superimposition of mainly the band due to the v(C-S) vibration of the alkanethiol chain in the trans conformation and the band due to the breathing vibration of adenine) was used as an analytical signal. The demonstrated biosensors are characterized by the low detection limit at the level of pg·uL–1, wide analytical range and high selectivity. It was found that for different DNA sequences, a SPR or SERS sensor achieves greater detection sensitivity, which means that the selection of the optimal sensor type depends on the sequence of the target DNA.