Ultrasensitive Refractometry via Supercritical Angle Fluorescence.
ACS Nano
; 12(12): 11892-11898, 2018 12 26.
Article
de En
| MEDLINE
| ID: mdl-30475589
ABSTRACT
Refractometry, namely, the measurement of refractive index (RI), provides information about various sample properties such as concentrations and molecular structure. One physical phenomenon which enables precise determination of a sample's RI in a microscope is the supercritical-angle fluorescence. This effect is observed when the fluorescence from an emitter near a glass-medium interface is captured by an objective lens with a high numerical aperture. The materials' index mismatch creates a distinguishable transition in the intensity pattern at the back focal plane of the objective that changes proportionally to the RI of the media. Here, we present a refractometry approach in which the fluorophores are preattached to the bottom surface of a microfluidic channel, enabling highly sensitive determination of the RI using tiny amounts of liquid (picoliters). With this method, we attained a standard deviation of 3.1 × 10-5 and a repeatability of 2.7 × 10-5 RI units. We first determine the capabilities of the device for glycerol-water solutions and then demonstrate the relevance of our system for monitoring changes in biological systems. As a model system, we show that we can detect single bacteria ( Escherichia coli) and measure population growth.
Mots clés
Texte intégral:
1
Collection:
01-internacional
Base de données:
MEDLINE
Sujet principal:
Réfractométrie
/
Microscopie de fluorescence
Langue:
En
Journal:
ACS Nano
Année:
2018
Type de document:
Article