Nanosensing at the single cell level

Abstract

This article presents an overview of the development, operation, and applications of optical nanobiosensors for use in in vivo detection of biotargets in individual living cells. The nanobiosensors are equipped with immobilized bioreceptor probes (e.g., antibodies, enzyme substrate) selective to specific molecular targets. Laser excitation is transmitted into the fiber producing an evanescent field at the tip of the fiber in order to excite target molecules bound to the bioreceptors immobilized at the fiber tips. A photometric system detects the optical signal (e.g., fluorescence) originated from the analyte molecules or from the analyte-bioreceptor reaction. Examples of detection of biospecies and molecular signaling pathways of apoptosis in a living cell are discussed to illustrate the potential of the nanobiosensor technology for single cell analysis.

Keywords: Apoptosis; Benzopyrene tetrol; Biosensor; Nanobiosensor; Single cell.

Fig. 1

Fabrication of nanofibers using the “heat and pull” technique.

Fig. 2

(A) Scanning electron micrograph (SEM) of an uncoated nanoprobe. The size of the fiber tip diameter is approximately 40 nm. (B) Scanning electron micrograph (SEM) of a fiber-optic nanosensor having the sidewall coated with silver.

Fig. 3

Metal coating system over rotating fiber tips.

Fig. 4

Instrumental system for fluorescence measurements of single cells.

Fig. 5

Photograph of a fiber-optic nanobiosensors inserted into a single cell.

Fig. 6

(A) Detection of caspase-9 activity in MCF-7 cells with ALA and laser treatment. (B) Monitoring of the control group of MCF-7 cells with ALA and no laser treatment [adapted from Ref. [21]].