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Published on: February 3, 2015
Robust Inclusion Complex of Topotecan Comprised within a Rhodamine-Labeled β-Cyclodextrin: Competing Proton and
Maria Rosaria Di Nunzio1, Abderrazzak Douhal1
1Departamento de Química Física, Facultad de Ciencias Ambientales y Bioquímica and INAMOL, Universidad de Castilla-La Mancha, Av. Carlos III, s/n, 45071 Toledo, Spain.
Abstract:
Monitoring the biological fate of medicaments within the environments of cancer cells is an important challenge which is nowadays the object of intensive studies. In this regard, rhodamine-based supramolecular systems are one of the most suitable probes used in drug delivery thanks to their high emission quantum yield and sensitivity to the environment which helps to track the medicament in real time. In this work, we used steady-state and time-resolved spectroscopy techniques to investigate the dynamics of the anticancer drug, topotecan (TPT), in water (pH ~6.2) in the presence of a rhodamine-labeled methylated β-cyclodextrin (RB-RM-βCD). A stable complex of 1:1 stoichiometry is formed with a Keq value of ~4 × 104 M-1 at room temperature. The fluorescence signal of the caged TPT is reduced due to: (1) the CD confinement effect; and (2) a Förster resonance energy transfer (FRET) process from the trapped drug to the RB-RM-βCD occurring in ~43 ps with 40% efficiency. These findings provide additional knowledge about the spectroscopic and photodynamic interactions between drugs and fluorescent functionalized CDs, and may lead to the design of new fluorescent CD-based host-guest nanosystems with efficient FRET to be used in bioimaging for drug delivery monitoring.
Insights
Researchers studied how the anticancer drug topotecan (TPT) interacts with a fluorescently labeled cyclodextrin. They found a stable complex forms, and energy transfer occurs, enabling real-time tracking for drug delivery monitoring.
Area of Science:
- Supramolecular Chemistry
- Biophysical Chemistry
- Materials Science
Background:
- Monitoring drug delivery in cancer cells is crucial.
- Rhodamine-based probes offer real-time tracking due to high fluorescence.
- Functionalized cyclodextrins are promising for drug delivery systems.
Purpose of the Study:
- To investigate the spectroscopic and photodynamic interactions between topotecan (TPT) and a rhodamine-labeled methylated β-cyclodextrin (RB-RM-βCD).
- To understand the dynamics of TPT within the cyclodextrin host-guest system.
- To explore the potential for FRET-based drug delivery monitoring.
Main Methods:
- Steady-state and time-resolved spectroscopy.
- Fluorescence spectroscopy to analyze drug-cyclodextrin interactions.
- Complexation studies to determine stoichiometry and binding constants.
Main Results:
- A stable 1:1 complex between TPT and RB-RM-βCD was formed with a binding constant (Keq) of ~4 × 10^4 M^-1.
- Fluorescence quenching of TPT was observed due to cyclodextrin confinement and Förster Resonance Energy Transfer (FRET).
- FRET occurred with ~40% efficiency over ~43 ps, indicating efficient energy transfer from TPT to the rhodamine probe.
Conclusions:
- The study elucidates the photophysical interactions between TPT and RB-RM-βCD.
- The observed FRET process provides a mechanism for real-time monitoring of drug encapsulation and release.
- Findings support the development of novel fluorescent cyclodextrin-based nanosystems for bioimaging and drug delivery applications.
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