Utility of Gold Nanoparticles for Spectrofluorimetric and Spectrophotometric Determination of Sildenafil Citrate, Dapoxetine, Vardenafil and Tadalafil in their Dosage Forms and Biological Fluids
Abstract
Abstract Two simple, rapid and novel sensitive fluorimetric and spectrophotometric methods were investigated for the assay of sildenafil citrate (SIL), dapoxetine (DAP), vardenafil (VAD) and tadalafil (TAD) using gold nanoparticles (Au NPs). On the spectrofluorimetric method, gold nanoparticles were used as a fluorescence probe. The addition of drugs to Au-NPs solution caused considerable quenching of the emission band of Au-NPs, which was likely due to the complexation of the drug to gold NPs. Under the optimum conditions, the quenched fluorescence (FL) intensity was linear with the studied concentrations. The quenching mechanism of the studied drugs on the emission band of Au-NPs was explained by Stern-Volmer law. The second spectrophotometric method was based on aggregation of synthesized gold nanoparticles. Gold nanoparticles showed absorption at 522 nm. Upon interaction with the cited drugs, the band at 522 nm disappeared with the formation of a new red-shifted band at 673, 660, 665, and 663 nm for SIL, TAD, VAD, and DAP, respectively. Different experimental factors were optimized for higher sensitivity. The calibration curves were linear with a concentration range of 0.1-12 μg/mL for the studied drugs. The methods were applied successfully to determine the studied drugs in minor concentrations in pure form, pharmaceutical dosage forms, and biological fluids (human serum and urine).
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