HER2 biosensing through SPR-envelope tracking in plasmonic optical fiber gratings

Abstract

In the biomedical detection context, plasmonic tilted fiber Bragg gratings (TFBGs) have been demonstrated to be a very accurate and sensitive sensing tool, especially well-adapted for biochemical detection. In this work, we have developed an aptasensor following a triple strategy to improve the overall sensing performances and robustness. Single polarization fiber (SPF) is used as biosensor substrate while the demodulation is based on tracking a peculiar feature of the lower envelope of the cladding mode resonances spectrum. This method is highly sensitive and yields wavelength shifts several tens of times higher than the ones reported so far based on the tracking of individual modes of the spectrum. An amplification of the response is further performed through a sandwich assay by the use of specific antibodies. These improvements have been achieved on a biosensor developed for the detection of the HER2 (Human Epidermal Growth Factor Receptor-2) protein, a relevant breast cancer biomarker. These advanced developments can be very interesting for point-of-care biomedical measurements in a convenient practical way.

Fig. 1.

Sketch of specific HER2 biodetection based on an SPR-TFBG biofunctionalized using anti-HER2 aptamers.

Fig. 2.

Scheme of the experimental setup used for biofunctionalization and biodetection experiments (300 µL samples are used).

Fig. 3.

Response signal of the SPR-TFBG at the end of the aptamer immobilization and in PBS (before and after aptamer grafting) (a) with an enlargement on the spectral region of interest (b). The fit of the SPR signature using the envelope is also shown. Enlargement on the wavelength shift of the SPR envelope maximum around during the aptamer immobilization (c). Sensorgram showing the tracking of the wavelength shift in nm over time of the SPR envelope during the aptamer immobilization with immersion in PBS before and after grafting (d).

Fig. 4.

Tracking of the SPR-TFBG response signal shift in wavelength during the 6-mercapto-1-hexanol blocking in PBS with an enlargement on the spectral region of interest (a). The sensorgram obtained by using the tracking of the maximum of the SPR envelope overtime is also plotted (b).

Fig. 5.

Sketch of principle of HER2 biodetection at SPR TFBG aptasensor interface through anti-HER2 aptamers and signal amplification using anti-HER2 antibodies.

Fig. 6.

Tracking of the SPR envelope in the spectral region of interest during the HER2 biodetection through anti-HER2 aptamers (a) and the anti-HER2 amplification (b). Tracking of the wavelength shift in nm over time of the maximum of the SPR envelope during the biodetection with measurements in PBS between each step (c).