Super-resolution displacement spectroscopic sensing of exosomes

Subwavelength manipulation of light waves with high precision can enable new and exciting applications in spectroscopy, sensing, and medical imaging. For these applications, miniaturized spectrometers are desirable to enable the on-chip analysis of spectral information. In particular, for imaging-based spectroscopic sensing mechanisms, the key challenge is to determine the spatial-shift information accurately (i.e., the spatial displacement introduced by wavelength shift or biological or chemical surface binding), which is similar to the challenge presented by super-resolution imaging.

Researchers at SUNY Buffalo have developed a unique “rainbow” trapping metasurface for on-chip spectrometers and sensors. Combined with super-resolution image processing, the low-setting 4× optical microscope system resolves a displacement of the resonant position within 35 nm on the plasmonic rainbow trapping metasurface with a tiny area as small as 0.002 mm2. This unique feature of the spatial manipulation of efficiently coupled rainbow plasmonic resonances reveals a new platform for miniaturized on-chip spectroscopic analysis with a spectral resolution of 0.032 nm in wavelength shift. Using this low-setting 4× microscope imaging system, the researchers demonstrate a biosensing resolution of 1.92 × 109 exosomes per milliliter for A549-derived exosomes and distinguish between patient samples and healthy controls using exosomal epidermal growth factor receptor (EGFR) expression values, thereby demonstrating a new on-chip sensing system for personalized accurate bio/chemical sensing applications.

Sensor arrays for lung cancer diagnosis

(a) Schematic diagram of the rainbow trapping metasurface used in lung cancer diagnosis. (b) SEM image of a sensor array with four identical graded metasurface structures. (c) Schematic diagram of the surface grating with captured EGFR and exosomes (PEG: polyethylene glycol). (d, e) Real-time response of the centroid displacement upon (d) A549 and (e) healthy control 1 (blue curve) and patient 1 (red curve) sample exosome adsorption on the sensor surface. (f) Exosomal EGFR expression of healthy controls and NSCLC patient samples measured by four sensor units on the chip. (g) Average exosomal EGFR expression of healthy controls and NSCLC patient samples. Orange and green bars indicate the means of three samples in each group. Significantly higher expression of exosomal EGFR was observed in the NSCLC patient samples than in those of the healthy controls (n = 3; *p < 0.05).

Zhou L, Zhang N, Hsu CC et al. (2022) Super-Resolution Displacement Spectroscopic Sensing over a Surface “Rainbow”. Engineering [Epub ahead of print]. [article]

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