Investigation of Encapsulated Liposomal Antituberculotics and Effects on in Vitro Model Systems

Abstract

Introduction. Liposomes are widely investigated nanocarriers, which are capable for incorporation of both lipid-soluble and water-soluble drugs. WHO aimed to eradicate TB disease, which is caused by Mycobacterium tuberculosis bacteria. TB kills more than 1 million people every year. The main reasons for death are increasing frequency of MDR (multidrug-resitant) and XDR (extensively drug-resistant) bacteria stems and inappropriate patient compliance.Aim. Preparation and encapsulation of newly synthesized antitubercultic compound into liposomes. To enhance the encapsulation efficiency and to target intracellular bacteria in the macrophages.Methods.We have prepared two types of liposomes.Type I. consists of dipalmitoyl phosphatidylcholine (DPPC).Type II. consists of: dioleoylphosphatidylethanolamine (DOPE), cholesteryl hemisuccinate (CHEMS) and pegylated distearoyl phosphatidylethanolamine (DSPE-PEG).We used thin lipid film technology to prepare multilamellar vesicles (MLV) and henceforward both types were treated with ultrasound or extrusion technique to get small unilamellar vesicles (SUV). The size distribution of liposomes was determined/measured with dynamic light scattering (DLS). The change of diameter of vesicles show the rate of aggregation. We investigated the efficacy of the preparation technology and the stability of liposomes. The used antituberculotic compounds were: isoniazid (INH), TB 504, TB 505 (chemical structure not published yet). Encapsulation efficiency was determined by measuring absorbance after size exclusion chromatography (SEC).Results. DPPC vesicles showed reduced stability than complex liposomes (type II.) both at 4 and 20 °C. By extrusion method we got uniform and more stable vesicles. Encapsulation efficiency was influenced by the diameter of liposome and the physico-chemical properties of antituberculotic compounds. The in vitro activity of liposomal antituberculotic compounds was determined on M. tuberculosis H37Rv culture. Considering that M. tuberculosis is an intracellular pathogen the effect of the compounds was studied on M. tuberculosis H37Rv infected MonoMac6 human monocytes.