Antimycobacterial agents : a study of Liposomal-Encapsulation, comparitive permeability of bronchial tissue and in vitro activity against mycobacterium tuberculosis isolates

Van Rensburg, Lyne (2012-12)

Thesis (MScMedSc)--Stellenbosch University, 2012.

Includes bibliography

Thesis

ENGLISH ABSTRACT: In this thesis, research results are reported on the role of dipalmitoyl phosphatidyl choline (DPPC) and DPPC-liposomes on the in vitro permeability characteristics of various antimycobacterial drugs across porcine bronchial tissue. The permeability flux values of the different compounds (isoniazid, ofloxacin and moxifloxacin) and their relevant DPPC formulations were determined using a continuous flow through perfusion system. Mean steady state flux values were compared statistically by means of a t-test at a significance level of 5% as well as an F-test using whole curve comparisons. The results indicated that the different formulations of drug and their DPPC combinations retard the permeation of drug through bronchial tissue. However, moxifloxacin permeation was significantly enhanced when in a DPPC-liposomal formulation. These results demonstrate the important role that molecular weight, electrostatic charge, partitioning of the molecules in DPPC and DPPC-liposomes play in transmembrane diffusion. In addition, the effect of individual drugs and their DPPC combinations on the surface tension lowering property of DPPC was evaluated. The results obtained showed minimal decreases in the surface tension lowering capability of DPPC; however, the minimal increases in surface tension do not alter the integrity of DPPC to a large extent. Drug susceptibility testing of Mycobacterium tuberculosis cultures against the individual antitubercular drugs and their DPPC combinations was done by using the Radiometric BACTEC 460TB™ system. Drug-entrapped DPPC liposomes were tested at concentrations comparable to their relative minimum inhibitory concentrations (MIC). The results for the BACTEC assay indicated that the mycobacteria were susceptible to the developed drug entrapped liposomes; of which their encapsulation efficiencies for the relevant drugs were approximately ± 50%. It was concluded that drug-entrapped DPPC liposomes could fulfill the dual role of pulmonary drug delivery and alveolar stabilization due to antiatelectatic effect of DPPC which can improve the distribution of anti-tubercular drugs in the lung

AFRIKAANSE OPSOMMING: Hierdie tesis doen verslag oor navorsingsresultate met betrekking tot die rol van dipalmitoïel-fosfatidiel-cholien (DPPC) en DPPC-liposome in die in vitro-permeasiekenmerke van verskeie antimikobakteriese middels oor vark- brongiale weefsel. Die permeasievloedwaardes van die verskillende verbindings (isoniasied, ofloksasien en moksifloksasien) en hul betrokke DPPC-formules is met behulp van ’n deurlopende-deurvloei-perfusiestelsel bepaal. Gemiddelde vloedwaardes in ’n bestendige staat is statisties vergelyk met behulp van ’n t-toets op ’n beduidendheidsvlak van 5%, sowel as ’n F-toets met behulp van heelkurwevergelykings. Die resultate dui daarop dat die verskillende middelformules en hul DPPC-kombinasies middelpermeasie oor brongiale weefsel vertraag. Tog is die permeasie van moksifloksasien aansienlik versterk in ’n DPPC-liposomale formule. Hierdie resultate bevestig die belangrike rol van molekulêre gewig, elektrostatiese lading, die verdeling van molekules in DPPC sowel as DPPC-liposome in transmembraandiffusie. Daarbenewens is die uitwerking van individuele middels en hul DPPC-kombinasies op die oppervlakspanningsverligtingsvermoë van DPPC beoordeel. Die resultate toon minimale afnames in die oppervlakspanningsverligtingsvermoë van DPPC. Die minimale toenames in oppervlakspanning het egter meestal geen noemenswaardige effek op die integriteit van DPPC gehad nie. Voorts is die vatbaarheid van Mycobacterium tuberculosis-kwekings vir die individuele anti-tuberkulêre middels en hul DPPC-kombinasies met behulp van die radiometriese BACTEC 460TB™-stelsel getoets. Middel-ingeslote DPPC-liposome is getoets in konsentrasies wat met hul relatiewe minimum inhibisiekonsentrasies (MIK) vergelyk kan word. Die resultate van die BACTEC-toets toon dat die mikobakterieë vatbaar was vir die ontwikkelde middel-ingeslote liposome, met ’n enkapsuleringsdoeltreffendheid van ongeveer 50% vir die betrokke middels. Die studie kom tot die gevolgtrekking dat middel-ingeslote DPPC-liposome die dubbele rol van pulmonêre middel-lewering en alveolêre stabilisering kan vervul weens die anti-atelektatiese werking van DPPC, wat die verspreiding van anti-tuberkulêre middels in die long kan verbeter.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/71868
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