Limits...
Design and Fabrication of Fiber-Optic Nanoprobes for Optical Sensing

View Article: PubMed Central - HTML - PubMed

ABSTRACT

This paper describes the design and fabrication of fiber-optic nanoprobes developed for optical detection in single living cells. It is critical to fabricate probes with well-controlled nanoapertures for optimized spatial resolution and optical transmission. The detection sensitivity of fiber-optic nanoprobe depends mainly on the extremely small excitation volume that is determined by the aperture sizes and penetration depths. We investigate the angle dependence of the aperture in shadow evaporation of the metal coating onto the tip wall. It was found that nanoaperture diameters of approximately 50 nm can be achieved using a 25° tilt angle. On the other hand, the aperture size is sensitive to the subtle change of the metal evaporation angle and could be blocked by irregular metal grains. Through focused ion beam (FIB) milling, optical nanoprobes with well-defined aperture size as small as 200 nm can be obtained. Finally, we illustrate the use of the nanoprobes by detecting a fluorescent species, benzo[a]pyrene tetrol (BPT), in single living cells. A quantitative estimation of the numbers of BPT molecules detected using fiber-optic nanoprobes for BPT solutions shows that the limit of detection was approximately 100 molecules.

No MeSH data available.


Related in: MedlinePlus

Intracellular measurement of benzo[a]pyrene tetrol (BPT) with nanoprobes. PC3 human prostate cancer cells were incubated with 1 μM BPT in PBS for 2 h. Control cells are treated with PBS only. All dishes were rinsed with PBS prior to measurement.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211233&req=5

Figure 9: Intracellular measurement of benzo[a]pyrene tetrol (BPT) with nanoprobes. PC3 human prostate cancer cells were incubated with 1 μM BPT in PBS for 2 h. Control cells are treated with PBS only. All dishes were rinsed with PBS prior to measurement.

Mentions: Chemical analysis of polynuclear aromatic hydrocarbons (PAHs) is of great environmental and toxicological interest because many of them have been shown to be mutagens and/or potent carcinogens in laboratory animal assays. Benzo[a]pyrene (BaP), which has been extensively investigated, is one of the more potent carcinogens among PAHs and is a fundamental indicator of exposure and carcinogenic activity of all PAHs. In order to facilitate the study of intracellular dynamics of benzo[a]pyrene tetrol (BPT), the related biomarker under BaP exposure, a quantitative estimation of the numbers BPT molecules detected using fiber-optic nanoprobes for solutions containing different BPT concentrations was performed and shown in Figure 8. The limit of detection that corresponds to the amount of analyte emitting a signal 3 times the standard deviation of the noise was determined to be 1 μM for BPT. Under 1 μM, the dark count noise from PMT was stronger than the signal. The detection volume can be estimated as 17 aL for 200 nm aperture probe based on Bethe–Bouwkamp theory. Therefore, the limit of detection was approximately 100 BPT molecules. Figure 9 shows the intracellular measurement of BPT in PC3 human prostate cancer cells. The cells were incubated with 1 μM BPT in PBS for 2 h at 37°C. Control cells are PC3 cells treated with PBS only. All dishes were rinsed with PBS prior to measurement. It is apparent that the treated cells exhibited higher fluorescence reading than the control group. Although in our preliminary experiments the living cells were directly incubated with BPT, the results illustrate that the nanoprobes can be employed to detect very low concentrations of fluorescent species such as BPT molecules that are important biomarkers of exposure and carcinogenic activity of related PAHs, inside living cells.


Design and Fabrication of Fiber-Optic Nanoprobes for Optical Sensing
Intracellular measurement of benzo[a]pyrene tetrol (BPT) with nanoprobes. PC3 human prostate cancer cells were incubated with 1 μM BPT in PBS for 2 h. Control cells are treated with PBS only. All dishes were rinsed with PBS prior to measurement.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211233&req=5

Figure 9: Intracellular measurement of benzo[a]pyrene tetrol (BPT) with nanoprobes. PC3 human prostate cancer cells were incubated with 1 μM BPT in PBS for 2 h. Control cells are treated with PBS only. All dishes were rinsed with PBS prior to measurement.
Mentions: Chemical analysis of polynuclear aromatic hydrocarbons (PAHs) is of great environmental and toxicological interest because many of them have been shown to be mutagens and/or potent carcinogens in laboratory animal assays. Benzo[a]pyrene (BaP), which has been extensively investigated, is one of the more potent carcinogens among PAHs and is a fundamental indicator of exposure and carcinogenic activity of all PAHs. In order to facilitate the study of intracellular dynamics of benzo[a]pyrene tetrol (BPT), the related biomarker under BaP exposure, a quantitative estimation of the numbers BPT molecules detected using fiber-optic nanoprobes for solutions containing different BPT concentrations was performed and shown in Figure 8. The limit of detection that corresponds to the amount of analyte emitting a signal 3 times the standard deviation of the noise was determined to be 1 μM for BPT. Under 1 μM, the dark count noise from PMT was stronger than the signal. The detection volume can be estimated as 17 aL for 200 nm aperture probe based on Bethe–Bouwkamp theory. Therefore, the limit of detection was approximately 100 BPT molecules. Figure 9 shows the intracellular measurement of BPT in PC3 human prostate cancer cells. The cells were incubated with 1 μM BPT in PBS for 2 h at 37°C. Control cells are PC3 cells treated with PBS only. All dishes were rinsed with PBS prior to measurement. It is apparent that the treated cells exhibited higher fluorescence reading than the control group. Although in our preliminary experiments the living cells were directly incubated with BPT, the results illustrate that the nanoprobes can be employed to detect very low concentrations of fluorescent species such as BPT molecules that are important biomarkers of exposure and carcinogenic activity of related PAHs, inside living cells.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

This paper describes the design and fabrication of fiber-optic nanoprobes developed for optical detection in single living cells. It is critical to fabricate probes with well-controlled nanoapertures for optimized spatial resolution and optical transmission. The detection sensitivity of fiber-optic nanoprobe depends mainly on the extremely small excitation volume that is determined by the aperture sizes and penetration depths. We investigate the angle dependence of the aperture in shadow evaporation of the metal coating onto the tip wall. It was found that nanoaperture diameters of approximately 50 nm can be achieved using a 25° tilt angle. On the other hand, the aperture size is sensitive to the subtle change of the metal evaporation angle and could be blocked by irregular metal grains. Through focused ion beam (FIB) milling, optical nanoprobes with well-defined aperture size as small as 200 nm can be obtained. Finally, we illustrate the use of the nanoprobes by detecting a fluorescent species, benzo[a]pyrene tetrol (BPT), in single living cells. A quantitative estimation of the numbers of BPT molecules detected using fiber-optic nanoprobes for BPT solutions shows that the limit of detection was approximately 100 molecules.

No MeSH data available.


Related in: MedlinePlus