Thymol encapsulated in β-cyclodextrin nanocavities for enhanced bio-efficacies and subsequent binding with DNA
摘要
Cyclodextrins are toroidal oligosaccharides with six to eight D-glucose monomers. β-cyclodextrins (β-CD) having seven such monomer units find various applications as drug delivery vehicles as it forms stable inclusion complexes with small biologically active molecules. Here, we have chosen thymol, as it has antimicrobial, antibacterial and antioxidant activities owing to its phenolic structure. We have studied the behaviour of β-CD encapsulated thymol and its interaction with DNA and different cell lines. Various sets of β-CD encapsulated systems were prepared by Box–Behnken design. Morphology of the encapsulated systems have been characterised using TEM and stability of the systems were monitored using DLS. UV–visible spectroscopy indicates a hyperchromic shift upon gradual addition of DNA. Isothermal titration calorimetric experiments help to confirm the binding interactions between β-CD-thymol and DNA. Positive ∆H (+ 336 kJ mol−1) and ∆S (+ 1.176 kJ mol−1 K−1) values indicate hydrophobic interactions. Fluorescence spectroscopic studies showed emission intensity of the complex decreases gradually upon increasing addition of DNA. Temperature variance and time resolved fluorescence measurement support static quenching. Competitive displacement assay, iodide quenching and DNA melting studies suggest groove binding with DNA. By encapsulation technique, thymol can be safely delivered to the living cells. MTT assay was performed to see whether the encapsulation has impact on anticancer activity or not. Finally, ROS-H2O2 assay indicated that β-CD-thymol offers cell protection under oxidative stress.