PAMAM-Calix-Dendrimers: Second Generation Synthesis, Fluorescent Properties and Catecholamines Binding

Area of Science:

• Supramolecular Chemistry
• Polymer Science
• Organic Synthesis

Background:

• PAMAM dendrimers are versatile macromolecules with tunable properties.
• Calixarenes are macrocyclic compounds with well-defined cavities.
• Combining dendrimers and calixarenes offers unique structural and functional possibilities.

Purpose of the Study:

• To synthesize second-generation PAMAM dendrimers utilizing a p-tert-butylthiacalix[4]arene core.
• To investigate the fluorescence properties of the novel PAMAM-calix-dendrimers.
• To evaluate the binding capabilities of these dendrimers towards catecholamines and assess their potential in drug delivery.

Main Methods:

• Synthesis of PAMAM dendrimers with p-tert-butylthiacalix[4]arene cores in cone, partial cone, and 1,3-alternate conformations.
• Spectroscopic techniques including UV-Vis, fluorescence, 1D and 2D NMR for characterization and binding studies.
• Dynamic Light Scattering (DLS) for determining the size of supramolecular complexes.

Main Results:

• Successful synthesis of PAMAM-calix-dendrimers with observed unusual fluorescence.
• Demonstrated binding of catecholamines (dopamine, adrenaline, noradrenaline) with calculated binding constants (logK_a 3.85-4.74).
• Catecholamine binding occurs within the internal cavities, with the 1,3-alternate conformation showing highest efficiency.
• DLS confirmed the size of dendrimer/catecholamine supramolecular systems.
• Hemolytic activity decreased with increasing dendrimer generation for the 1,3-alternate conformation.

Conclusions:

• PAMAM-calix-dendrimers were successfully synthesized and characterized.
• These dendrimers exhibit significant binding affinity for catecholamines.
• The 1,3-alternate conformation is optimal for catecholamine binding and shows reduced hemolytic activity, indicating potential as drug delivery agents.