Combined System for the Simultaneous Delivery of Levofloxacin and Rifampicin: Structural and Functional Properties and Antibacterial Activity

Abstract

The therapy of resistant forms of tuberculosis requires the simultaneous use of several drugs, in particular, a combination of rifampicin and levofloxacin. In this paper, we aimed to design a combined system for the simultaneous delivery of these drugs for potential inhalation administration. A feature of this system is the incorporation of rifampicin into optimized liposomal vesicles capable of forming a multipoint non-covalent complex with chitosan-β-cyclodextrin conjugates. Levofloxacin is incorporated into cyclodextrin tori by forming a host-guest complex. Here, a comprehensive study of the physicochemical properties of the obtained systems was carried out and special attention was paid to the kinetics of cargo release for individual drugs and in the combined system. The release of levofloxacin in combined system is slow and is described by the Higuchi model in all cases. The release of rifampicin from liposomes during the formation of complexes with polymeric conjugates is characterized by the change of the Higuchi model to the Korsmeyer-Peppas model with the main type of diffusion against Fick's law. Microbiological studies in solid and liquid growth media a consistently high antibacterial activity of the obtained systems was shown against B. subtilis and E. coli.

Keywords: antibiotics; chitosan; cyclodextrin; levofloxacin; liposomes; rifampicin.

Figure 1

Structures of substances under consideration and the schematic cartoon representing the structure of combined system.

Figure 2

Rifampicin release from liposomal forms with and without a polymer shell. (a) LRif DPPC (blue line) and its complex with HP-CD-Chit (red) and NH₂-CD-Chit (green). (b) LRif DPPC:CL 80:20 (blue line) and its complex with HP-CD-Chit (red) and NH₂-CD-Chit (green). For all complexes, the liposome : polymer base–molar ratio was 1:7. Total lipid concentration 3 mg/mL in 0.01 M Na phosphate-buffered solution, pH 7.4. 37 °C. SD (n = 3).

Figure 3

Mathematical processing of Rif release curves from DPPC:CL (80:20) liposomes without polymers (orange line) and in a complex with NH₂-CD-Chit (red line) through the Higuchi (a) and Korsmeyer–Peppas (b) models. For all complexes, the liposome : polymer base–molar ratio was 1:7. Total lipid concentration 3 mg/mL in 0.01 M Na phosphate-buffered solution, pH 7.4. 37 °C.

Figure 4

Mathematical processing of Lev release curves from the guest–host complex with NH₂-CD (grey line) and NH₂-CD-Chit (green line) by the Higuchi models. A total of 0.01 M Na phosphate-buffered solution, pH 7.4. 37 °C.

Figure 5

(a) Lev release profile from the NH₂-CD-Chit and Lev (purple) complex and the Rif (orange) from the LRif NH₂-CD-Chit complex. Independent experiments. (b) The simultaneous release of Lev (purple) and Rif (orange) from the combined system LRif DPPC:CL + NH₂-CD-Chit, loaded with Lev. A total of 0.01 M Na phosphate-buffered solution, pH 7.4. 37 °C. SD (n = 3).

Figure 6

In vitro experiments in solid media (A) on E. coli ATCC 25922 and in liquid media (B) on B. subtilis 6633, 37 °C.