L-cysteine capped silver nanoparticles as chiral recognition sensor for ketoprofen enantiomers.

A simple, inexpensive but effective approach for visual chiral recognition of ketoprofen enantiomers was developed using L-cysteine capped silver nanoparticles (L-Cys-AgNPs) as a colorimetric sensor. Upon the addition of R-ketoprofen to L-Cys-AgNPs, rapid aggregation occurred, and the solution changed color from yellow to green. However, the presence of S-ketoprofen did not induce any color change. The results were characterized using UV-Vis, FESEM, FT-IR, SERS, and zeta potential measurements. The chiral assay described in this work is easily distinguished with the naked eyes or using a UV-Vis spectrometer. The sensor revealed a good linear response to ketoprofen enantiomers in the concentration range of 8.33-33.3 µM with a detection limit of 4.52 µM and relative standard deviation of 3.73%. The proposed method was utilized for the determination of ketoprofen racemic mixtures in water samples and commercial tablets. The method excels by its simplicity, low cost, and good availability of materials.

Spectroscopic studies for the inclusion complexation of ketoprofen enantiomers with ß-cyclodextrin.

Inclusion complexes of R-ketoprofen and S-ketoprofen enantiomers with ß-cyclodextrin (ß-CD) in aqueous solution were studied using various spectroscopic techniques such as Raman, FTIR, UV and fluorescence. The different relative intensities and characteristic band shifts of the two enantiomers from Raman spectra suggests different interaction when complexed with ß-CD. Raman experiments revealed a noticeable diminishing of the CC vibration and ring deformation, which indicate the embedding of ketoprofen inside the ß-CD cavity. It's revealed that distinct differences between R- and S-ketoprofen in the presence of ß-CD at neutral pH. The stoichiometry ratio and binding constant of the inclusion complexes were calculated using Benesi-Hildebrand plot. Both enantiomers showed stoichiometry ratio of 1:1 inclusion complex with ß-CD. The binding constant of R-ketoprofen (4088 M-1) is higher than S-ketoprofen (2547 M-1). These values indicated that ß-CD formed inclusion complexes more preferentially with R-ketoprofen than S-ketoprofen. Results demonstrated that ß-CD can be used as a promising chiral selector for ketoprofen enantiomers.