Electrochemical and spectroscopic characterization of the interaction between β -lapachone and PAMAM derivatives immobilized on surface electrodes

The β-lapachone (βLP) is a very promising antitumor drug, but its low solubility in water limits its clinical application. This work reports the study of encapsulation of βLP, a quinone with polyamidoamine dendrimers (PAMAM) immobilized on the surface of the carbon nanotubes and gold electrodes. This polymer can form complexes with bioactive substances, having low toxicity and an excellent drug delivery system. The electrochemical techniques proved to be an important tool for the study of the inclusion complex, and electrochemical measurements were obtained by the cyclic voltammetry technique in a protic medium (sodium sulfate, 0.2 mol L−1 with 5% of the ethanol). To calculate the constant (K) interaction and the number of activation sites (n) between dendrimer and βLP, the working gold electrode was modified with 11-mercaptoundecanoic acid (MUA) and PAMAM (MUA/PAMAM) and the values obtained from them, using the equation adapted from Scatchard-Klotz, were K = 2.9 × 104 M−1 and n = 22.77, respectively. Observing the generated voltammograms and impedance experiments, we can note a much larger and significant interaction between the quinone with PAMAM and the MUA/PAMAM electrode than with MUA alone or without modification. FTIR and UV–Vis studies were also performed to demonstrate the formation of an inclusion complex among βLP and PAMAM.