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  • Polyethylenimine-capped Ag nanoparticle film as a platform for detecting charged dye molecules by surface-enhanced Raman scattering and metal-enhanced fluorescence.

Polyethylenimine-capped Ag nanoparticle film as a platform for detecting charged dye molecules by surface-enhanced Raman scattering and metal-enhanced fluorescence.

ACS applied materials & interfaces (2012-10-10)
Kwan Kim, Ji Won Lee, Kuan Soo Shin
ABSTRACT

Many drugs are charged molecules and are weak bases or acids having counterions. Their binding to biological surfaces is generally difficult to assess by vibrational spectroscopy. In this work, we demonstrated the potential of surface-enhanced Raman scattering (SERS) conducted using a polyethylenimine (PEI)-capped Ag nanoparticle film for the quantification of an electrostatic adsorption process of charged drug molecules, by using charged dye molecules such as sulforhodamine B (SRB) and rhodamine-123 (R123) as model drugs. It was possible to detect small-sized anions such as SCN(-) at 1 × 10(-9) M by SERS because of the cationic property of PEI. We were subsequently able to detect a prototype anionic dye molecule, SRB, by SERS at a subnanomolar concentration. On the other hand, it was difficult to detect cationic dyes such as R123 because of the electrostatically repulsive interaction with PEI. Nonetheless, we found that even R123 could be detected at subnanomolar concentrations by SERS by depositing an anionic polyelectrolyte such as poly(sodium 4-styrenesulfonate) (PSS) and poly(acrylic acid) (PAA) onto the PEI-capped Ag nanoparticles. Another noteworthy point is that a subnanomolar detection limit can also be achieved by carefully monitoring the fluorescence background in the measured SERS spectra. This was possible because charged dyes were not in contact with Ag but formed ion pairs with either PEI or PSS (PAA), allowing metal-enhanced fluorescence (MEF). The PEI-capped Ag nanoparticle film can thus serve as a useful indicator to detect charged drug molecules by SERS and MEF.

MATERIALS
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Product Description

Sigma-Aldrich
Sulforhodamine B, Dye content 75 %
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$53.20
5 g
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10 g
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$431.00
Sigma-Aldrich
Poly(4-styrenesulfonic acid) solution, Mw ~75,000, 18 wt. % in H2O
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10 g
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$431.00
Sigma-Aldrich
Sulforhodamine B sodium salt, powder, BioReagent, suitable for cell culture
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$53.20
5 g
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$208.00
10 g
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$431.00
Sigma-Aldrich
Sulforhodamine B sodium salt, Technical grade
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$53.20
5 g
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10 g
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$431.00
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Rhodamine 123, BioReagent, for fluorescence, ≥85% (HPLC)
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$53.20
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$431.00
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Sulforhodamine B, acid form, laser grade, Dye content 95 %
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$53.20
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$431.00
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Rhodamine 123, mitochondrial specific fluorescent dye
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5 g
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$431.00
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Poly(sodium 4-styrenesulfonate) solution, average Mw ~200,000, 30 wt. % in H2O
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5 g
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$431.00
Sigma-Aldrich
Poly(sodium 4-styrenesulfonate), average Mw ~70,000
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$53.20
5 g
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10 g
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$431.00
Sigma-Aldrich
Poly(sodium 4-styrenesulfonate) solution, average Mw ~1,000,000, 25 wt. % in H2O
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1 g
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5 g
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$208.00
10 g
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$431.00
Sigma-Aldrich
Poly(sodium 4-styrenesulfonate) solution, average Mw ~70,000, 30 wt. % in H2O
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1 g
Estimated to ship on March 24, 2025
$53.20
5 g
Estimated to ship on March 24, 2025
$208.00
10 g
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$431.00
Sigma-Aldrich
Poly(sodium 4-styrenesulfonate), average Mw ~1,000,000, powder
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1 g
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$53.20
5 g
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$208.00
10 g
Estimated to ship on March 24, 2025
$431.00