Tuberculosis (TB) is an infectious, deadly disease, caused by Mycobacterium tuberculosis
(M.tb). In 2010, there were 8,8 million incident cases of TB globally. South Africa currently
has the third highest TB incident cases worldwide. In an attempt to address the challenges
facing TB chemotherapy, among which frequent dosing and long duration of therapy resulting
in poor patient compliance, a novel poly(DL-lactic-co-glycolic) acid (PLGA) nanoparticulate
drug delivery system (DDS) encapsulating anti-TB drugs was developed. It is hypothesised
that this nanoparticulate DDS will address the challenges mentioned by enabling decreased
dosing frequency, shortening duration of therapy and minimising adverse side effects.
Therefore, favourable modification of pharmacodynamic (PD) and pharmacokinetic (PK)
properties of the conventional anti-TB drugs was demonstrated. Furthermore, the
nanoparticles will provide a platform for drug delivery to macrophages that serve as hosts for
M.tb.
The study design was based on determining specific physicochemical properties of the
nanoparticulate DDS to elucidate the hypothesis. Spray-dried PLGA nanoparticles were
prepared using the double emulsion solvent evaporation technique. In vivo analysis of
macrophage uptake and possible immunological response in mice were evaluated. In vitro
protein-binding assays of PLGA nanoparticles encapsulating anti-TB drugs isoniazid (INH)
and rifampicin (RIF) were performed with subsequent in vivo tissue distribution assays to
support protein-binding data generated. Finally, PK/PD analyses were conducted to evaluate
the effect of nanoencapsulation on the anti-TB drugs. These involved in vitro assays to
determine if sufficient drug was released from the nanoparticles to exhibit minimum inhibitory
concentration (MIC) and minimum bactericidal concentrations (MBC). Furthermore, in vivo
drug distribution and drug release kinetics assays of encapsulated RIF, INH, pyrazinamide
(PZA) and ethambutol (ETB) in a mouse model were performed.
The results confirmed that the PLGA nanoparticles (<250 nm, low positive zeta potential)
were taken up by macrophages in vivo with no significant immunological effect. Furthermore
the nanoparticles were present in the brain, heart, kidneys, lungs, liver and spleen for up to 7
days following once-off oral dosing at 13.23± 0.11%, 16.81± 0.11%, 54.89± 0.95%, 15.61±
1.15%, 48.48± 2.28% and 5.73± 0.21%, respectively. This was further confirmed by drug
analysis demonstrating the presence of INH, RIF and ETB at different time points up to 7 days in the lungs, kidneys, liver and spleen. However, PZA was not detected. Nanoencapsulated
RIF and INH exhibited MICs and MBCs in vitro over 14 days and these drugs were also
observed in plasma for up to 7 days post once-off oral dosing. ETB and PZA were observed
up to 3 days.
From the results generated, it can be concluded that the nanoparticles were taken up by
macrophages without eliciting an immune response. This provides a platform for drug delivery
to specific sites. Furthermore, the nanoparticulate DDS exhibited sustained drug release
in vitro and in vivo over a number of days above the MIC for the drugs analysed. Sustained
drug distribution was also observed. It can therefore be concluded that the hypothesised
reduction in dose frequency and duration of therapy for this DDS is a possibility / Thesis (PhD (Pharmaceutics))--North-West University, Potchefstroom Campus, 2013
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/9106 |
| Date | January 2012 |
| Creators | Booysen, Laetitia Lucretia Ismarelda Josephine |
| Publisher | North-West University |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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