pH- and Functionalization-Dependent Host-Guest Interactions Between Fluorescein and Various Poly(amidoamine)...

Area of Science:

• Supramolecular Chemistry
• Polymer Science
• Analytical Chemistry

Background:

• Dendrimers are versatile macromolecules with tunable properties for various applications.
• Understanding dendrimer-guest interactions is crucial for optimizing applications like drug delivery and environmental remediation.
• Environmental factors, particularly pH, significantly influence molecular interactions.

Purpose of the Study:

• To investigate the pH-dependent interactions between fluorescein and poly(amidoamine) dendrimers with different terminal groups.
• To elucidate the mechanisms governing these host-guest interactions.
• To establish a quantitative framework for analyzing such complex systems.

Main Methods:

• Utilized UV-vis and fluorescence spectroscopies to monitor fluorescein-dendrimer binding.
• Employed an open-source mathematical protocol for quantitative analysis of spectral data.
• Investigated dendrimers with amine, hydroxyl, and carboxyl terminal groups.

Main Results:

• Fluorescein binding was observed across four pH units with amine-terminated dendrimers and two pH units with hydroxyl-terminated dendrimers.
• No attractive interaction was detected between fluorescein and carboxyl-terminated dendrimers.
• Spectroscopic analysis revealed a redshift upon binding, indicating interaction.
• Interactions were found to be predominantly electrostatic, with contributions from hydrogen and CH-π bonding.

Conclusions:

• Dendrimer terminal functionalization dictates the pH range and strength of fluorescein binding.
• Electrostatic interactions are the primary drivers of fluorescein-dendrimer association.
• The study provides a reproducible method for analyzing complex host-guest interactions influenced by environmental conditions.