Interactions of Doxorubicin with Self-Assembled Monolayer-Modified Electrodes: Electrochemical, Surface Plasmon Resonance (SPR), and Gravimetric Studies

Abstract

We present the results on the partitioning of doxorubicin (DOX), a potent anticancer drug, through the model membrane system, self-assembled monolayers (SAMs) on gold electrodes. The monolayers were formed from alkanethiols of comparable length with different ω-terminal groups facing the aqueous electrolyte: the hydrophobic -CH(3) groups for the case of dodecanethiol SAMs or hydrophilic -OH groups of mercaptoundecanol SAMs. The electrochemical experiments combined with the surface plasmon resonance (SPR) and gravimetric studies show that doxorubicin is likely adsorbed onto the surface of hydrophilic monolayer, while for the case of the hydrophobic one the drug mostly penetrates the monolayer moiety. The adsorption of the drug hinders further penetration of doxorubicin into the monolayer moiety.

Drug–GSH interaction on GSH–Au modified electrodes: A cyclic voltammetry and electrochemical impedance spectroscopy study

“…The linear plots log j c and log j a as 8)), considering that in protic media the reduction of the quinone moiety consist in a 2e À /2H + transfer, a surface concentration of C 0 = 4 Â 10 À10 mol cm À2 was obtained, for a 1.51 mM solution of Dox. The result seems reasonable, as compared to the literature value of 3.8 Â 10 À11 from a 1 Â 10 À5 M solution [23].…”

“…4A, curve 3), indicating the presence of a second cathodic wave at more negative potential values on the reversible wave. This new cathodic wave was assigned to the reduction of Dox adsorbed onto or within the moiety of GSH layer [23]. On cycling in the potential range 0/À800 mV, both waves decrease, and after the 8th cycle a stable reversible voltammogram is obtained (Fig.…”

“…The electrochemistry of doxorubicin on gold electrodes modified with hydrophobic (dodecanthiol) and hydrophilic (mercaptoundecanol) organic thiols was recently reported [23]. It was shown that Dox strongly adsorbs, even at concentrations of 10 -5 M on bare and hydrophilic thiol-modified gold electrodes, while for the hydrophobic one, the drug mostly penetrates the monolayer moiety.…”

“…The presence of the adsorption wave c 2 allows to evaluate the diameter of the channels (pinholes) in the GSH layer, to about or higher than ca. 0.6 nm, corresponding to the dimension of the [Fe(CN) 6 ] 3À ion, and therefore CV experiments using ferricyanide ion as redox probe are useful to select compact layers to investigate their blocking and «open-gating» properties, similar to [Ru(NH 3 ) 6 ] 3+ [23,24].…”

“…10 6 -10 9 /cm 2 [23,27,28]. However, due to the errors involved by the evaluation of the potential and currents on the S-shaped curves in our working conditions, these values must be considered as a rough estimate of the porosity of the modified electrodes, allowing a preliminary characterization of the modified electrode prior to the investigation of «ion-gating» effects.…”