Mirela Enache

Spectral Studies on the Molecular Interaction of Anticancer Drug Mitoxantrone with CTAB Micelles

The interaction of anticancer drug mitoxantrone with cationic surfactant cetyltrimethylammonium bromide (CTAB) has been investigated by absorption spectroscopy as a function of surfactant concentration ranging from the premicellar to postmicellar region at pH 7.4 and 10. Interaction of mitoxantrone with CTAB micelles induces a bathochromic shift of both absorption maxima and spectral data showed that the micellization reduces the dimerization process and mitoxantrone is bound into micelles in the monomeric form. Binding constant and partition coefficient were estimated using the red shifts of the absorption maxima in the presence of surfactant. From the resulting binding constants for mitoxantrone-surfactant interactions, it was concluded that the hydrophobic interactions have a great effect on the binding of mitoxantrone to CTAB micelles. Also, by comparing the partition coefficients obtained using pseudo-phase model, the hydrophobic interactions have a major role in the distribution of mitoxantrone between micelle-water phases. Gibbs free energy of binding and distribution of mitoxantrone between the bulk aqueous medium and surfactant micelles were calculated.

Spectroscopic investigations of the molecular interaction of anticancer drug mitoxantrone with non-ionic surfactant micelles.

Objectives  The aim of this study was to investigate the interaction of the anticancer drug mitoxantrone with non‐ionic micelles, as simple model systems of biological membranes.

Mitoxantrone-Surfactant Interactions: A Physicochemical Overview

Mitoxantrone is a synthetic anticancer drug used clinically in the treatment of different types of cancer. It was developed as a doxorubicin analogue in a program to find drugs with improved antitumor activity and decreased cardiotoxicity compared with the anthracyclines. As the cell membrane is the first barrier encountered by anticancer drugs before reaching the DNA sites inside the cells and as surfactant micelles are known as simple model systems for biological membranes, the drugs-surfactant interaction has been the subject of great research interest. Further, quantitative understanding of the interactions of drugs with biomimicking structures like surfactant micelles may provide helpful information for the control of physicochemical properties and bioactivities of encapsulated drugs in order to design better delivery systems with possible biomedical applications. The present review describes the physicochemical aspects of the interactions between the anticancer drug mitoxantrone and different surfactants. Mitoxantrone-micelle binding constants, partitions coefficient of the drug between aqueous and micellar phases and the corresponding Gibbs free energy for the above processes, and the probable location of drug molecules in the micelles are discussed.

Spectroscopic Investigation of the Interaction of the Anticancer Drug Mitoxantrone with Sodium Taurodeoxycholate (NaTDC) and Sodium Taurocholate (NaTC) Bile Salts

The focus of the present work was to investigate the interaction of the anticancer drug mitoxantrone with two bile salts, sodium taurodeoxycholate (NaTDC) and sodium taurocholate (NaTC). Ultraviolet-visible (UV-Vis) absorption and electron paramagnetic resonance (EPR) spectroscopy were used to quantify the interaction and to obtain information on the location of mitoxantrone in bile salt micelles. The presence of submicellar concentrations of both bile salts induces mitoxantrone aggregation and the extent of drug aggregation in NaTDC is higher than in NaTC. For micellar bile salts concentrations, mitoxantrone monomers are entrapped in the micellar core. Binding constants, micelle/water partition coefficients and the corresponding thermodynamic parameters for binding and partitioning processes were estimated using the changes in monomer absorbance in the presence of bile salts. Binding interaction of mitoxantrone is stronger for NaTDC than NaTC micelles, whereas partitioning efficiency is higher for NaTC micelles for all investigated temperatures. Thermodynamic parameters indicate that both binding and partitioning processes are spontaneous and entropy controlled. The spectral behavior and thermodynamic parameters indicate distinct types of mitoxantrone interaction with NaTDC and NaTC micelles supported by the differences in nature and structure of bile salts micelles.

Tubular and Spherical SiO2 Obtained by Sol Gel Method for Lipase Immobilization and Enzymatic Activity

A wide range of hybrid biomaterials has been designed in order to sustain bioremediation processes by associating sol-gel SiO2 matrices with various biologically active compounds (enzymes, antibodies). SiO2 is a widespread, chemically stable and non-toxic material; thus, the immobilization of enzymes on silica may lead to improving the efficiency of biocatalysts in terms of endurance and economic costs. Our present work explores the potential of different hybrid morphologies, based on hollow tubes and solid spheres of amorphous SiO2, for enzyme immobilization and the development of competitive biocatalysts. The synthesis protocol and structural characterization of spherical and tubular SiO2 obtained by the sol gel method were fully investigated in connection with the subsequent immobilization of lipase from Rhizopus orizae. The immobilization is conducted at pH 6, lower than the isoelectric point of lipase and higher than the isoelectric point of silica, which is meant to sustain the physical interactions of the enzyme with the SiO2 matrix. The morphological, textural and surface properties of spherical and tubular SiO2 were investigated by SEM, nitrogen sorption, and electrokinetic potential measurements, while the formation and characterization of hybrid organic-inorganic complexes were studied by UV-VIS, FTIR-ATR and fluorescence spectroscopy. The highest degree of enzyme immobilization (as depicted from total organic carbon) was achieved for tubular morphology and the hydrolysis of p-nitrophenyl acetate was used as an enzymatic model reaction conducted in the presence of hybrid lipase–SiO2 complex.