Spectroscopic studies on the chiral recognition of ketoprofen enantiomers using different selectors / Asma Omar Obaid
Ketoprofen is a chiral drug marketed as a racemic mixture for medicinal use. The physiological reactions of R-ketoprofen and S-ketoprofen within the human body differ considerably; therefore, enantiorecognition is a necessary process that can be done using chiral selectors that interact different...
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| Format: | Thesis |
| Published: |
2022
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| Online Access: | http://studentsrepo.um.edu.my/14754/2/Asma_Omar.pdf http://studentsrepo.um.edu.my/14754/1/Asma.pdf http://studentsrepo.um.edu.my/14754/ |
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| Summary: | Ketoprofen is a chiral drug marketed as a racemic mixture for medicinal use. The
physiological reactions of R-ketoprofen and S-ketoprofen within the human body differ
considerably; therefore, enantiorecognition is a necessary process that can be done using
chiral selectors that interact differently with only one enantiomer. In this study, the
potential of different chiral selectors for recognizing ketoprofen enantiomers was
investigated. Gold and silver nanoparticles (AuNPs and AgNPs) were synthesized and
characterized then used for recognition of ketoprofen. AgNPs with ketoprofen
enantiomers showed significant differences in the appearance and spectra obtained, while
no differences were obtained between R- and S-ketoprofen when using AuNPs. Then
beta-cyclodextrin (β-CD) and hydroxypropyl-beta-cyclodextrin (HPβ-CD) inclusion
complexes with R- and S-ketoprofen were investigated as selectors for ketoprofen
enantiomers. The different relative intensities and characteristic band shifts of the two
enantiomers from Raman spectra suggest different interactions when complexed with β-
CD/HPβ-CD. Raman experiments revealed a noticeable diminishing of the C=C vibration
and ring deformation, which indicate the embedding of ketoprofen inside the β-CD cavity.
Both enantiomers showed a stoichiometry ratio of a 1:1 inclusion complex with β-CD and
HPβ-CD. The binding constant of R-ketoprofen (2750 M-1) and (1038 M-1) is higher than
S-ketoprofen (1299 M-1) and (799 M-1) with β-CD and HPβ-CD, respectively. These
values indicate that β-CD forms inclusion complexes more preferentially with Rketoprofen
than S-ketoprofen. This investigation was followed by qualitative surface
enhanced Raman spectroscopy (SERS) studies of β-CD/HPβ-CD inclusion complexes
with ketoprofen enantiomers using AgNPs and AuNPs as SERS substrate. In the second
part, the potential of L-cysteine capped with AgNPs (L-Cys-AgNPs) or AuNPs (L-Cys AuNPs) as chiral selectors for recognition of ketoprofen enantiomers have been studied.
Colorimetric sensors represent easy, inexpensive, simple and very effective visual chiral
recognition methods for the recognition of ketoprofen enantiomers. Rapid aggregation of
NPs occurred in the addition of R-ketoprofen, resulting in visible colour changes. The
chiral assay described in this work is easily distinguished with the naked eyes or using a
UV-Vis spectrometer. Both L-Cys-AgNPs and L-Cys-AuNPs sensors revealed a good
linear response to ketoprofen enantiomers in the concentration range of 8.33–33.33 μM.
The methods excel by their simplicity, low cost and good availability of materials. Both
qualitative and quantitative analysis were performed to test the capability of these
colorimetric sensors.
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