Browsing by Author "Smit, Marica"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Polymer-coated magnetic nanoparticles and modified polymer nanofibers for the efficient capture of Mycobacterium tuberculosis (Mtb)
    (Stellenbosch : Stellenbosch University, 2018-03) Smit, Marica; Lutz, Marietjie; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: The World Health Organization (WHO) determined that 10.4 million people died of tuberculosis (TB) in 2015 which makes TB the number one cause of death from a preventable infectious disease worldwide. Mycobacterium tuberculosis (Mtb) is the causative pathogen of TB and a frequent lack of clinical symptoms hampers the pathogen’s detection. Current diagnostic tests are limited when applied to low populations of bacteria in biological fluids, such as blood. A large volume of biological fluid is needed for a positive diagnosis. Obtaining multiple samples are, however, difficult, especially from children under six years. A smaller amount of biological fluid will be needed if the Mtb can be captured and concentrated within the sample. Polymer coated superparamagnetic magnetite nanoparticles (SPMNs) with affinity for the pathogen can be used as capturing substrates for Mtb followed by diagnosis via existing microscopy methods such as fluorescence microscopy (FM). In this thesis, modified chitosan and modified poly(styrene-alt-maleic anhydride) (SMA) were synthesized and utilized to coat SPMNs as well as electrospun into nanofibers to form potential Mtb capturing substrates. Chitosan and SMA were modified to from quaternary derivatives which can possibly interact with the Mtb cell wall. The nano-substrates were also surface functionalized with a carbohydrate binding protein, namely Concanavalin A (Con A), which can bind to the Mtb cell wall. Chitosan coated SPMNs were synthesized by in situ co-precipitating Fe2+ and Fe3+ with chitosan followed by further modification. SMA coated SPMNs were synthesized by activating the iron oxide core with 3-aminopropyl(triethoxysilane) (3-APTES) followed by further modification. Polymer nanofibers were electrospun via single needle electrospinning. The chitosan derivatives were electrospun into nanofibers by blending with non-ionogenic polymers, viz. polyvinyl alcohol (PVA), polylactide (PLA), polycaprolactam (Nylon 6), polyethylene oxide (PEO) and polyvinyl pyrrolidone (PVP) to facilitate electrospinning. The nano-substrates were evaluated for their affinity and thus capturing capabilities utilizing the mCherry fluorophore tagged bacillus Calmette-Guérin (BCG) strain of Mycobacterium bovis, a live attenuated Mtb-mimic. A preliminary nanofiber affinity study was conducted to determine which polymer-and-functional-moiety combination had the highest affinity for the bacteria utilizing FM (fluorescence microscopy). Quaternary SMA (SMI-qC12) had the highest affinity for BCG-mCherry (through electrostatic and hydrophobic interactions) followed by Con A immobilized chitosan (CS-EDC-Con A). The SPMNs were coated with three different polymer loadings and a dilution study performed to determine the limit of detection. The 0.9 g loaded SMI-qC12 SPMNs had the highest affinity for BCG-mCherry determined via FM and TEM (transmission electron microscopy).
  • Thumbnail Image
    Item
    Polymer-coated magnetic nanoparticles and polymer nanoparticles for the treatment of Mycobacterium tuberculosis (Mtb)
    (Stellenbosch : Stellenbosch University, 2022-04) Smit, Marica; Lutz, Marietjie; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: Tuberculosis (TB) can be classified as a neglected disease where an estimated one fourth of the world’s population could be infected with Mycobacterium tuberculosis (Mtb) in the form of latent TB. Combinations of three or more anti-tuberculosis (anti-TB) drugs are required during a long treatment period (between 6 months and 2 years) to effectively eliminate Mtb. The long treatment duration with concentrated anti-TB drugs has lead to side-effects, low patient adherence and resulting possible drug resistance. Orally administered anti-TB drugs have difficulty effectively reaching the lung and alveolar macrophages. Concentrated anti-TB drugs are thus orally administered daily in tablet form but anti-TB drug loaded polymer nanoparticles could possibly prevent rapid drug degradation via sustained release. There is thus a need to decrease the necessary concentration of the administered anti-TB drugs, which could be achieved via pulmonary inhalation which directly treats TB in the lungs. Polymer coated superparamagnetic iron oxide nanoparticles (SPMNs) could possibly enable targeted drug delivery via injection. The nanoparticles can be controlled with an external magnetic field to Mtb infected areas, followed by drug release from the anti-TB drug loaded polymer coating. In this thesis, biocompatible polymers namely chitosan, carrageenan, alginate, dextran sulfate and poly(lactide-co-glycolide) (PLGA) were utilized for anti-TB drug loading. Quaternary ammonium chitosan (CS-qC12) and quaternary ammonium poly(styrene-alt- maleic anhydride) (SMI-qC12) were also synthesized due to the known improvement in antimicrobial activity and mucoadhesion, due to the quaternary ammonium functional groups, compared to pristine chitosan and poly(styrene-alt-maleic anhydride). Several commonly administered anti-TB drugs such as isoniazid (INH), rifampicin (RIF), ethambutol (EMB), streptomycin (STM), ethionamide (ETA) and ofloxacin (OFX) were utilized for anti-TB drug loading. Chitosan (CS) based anti-TB drug loaded nanoparticles were synthesized via ionic gelation where polymer and anti-TB drug is dissolved, followed by the addition of crosslinking agent or polymer to prepare the nanoparticles (distributing anti-TB drug throughout the polymer matrix). PLGA nanoparticles were prepared via an “oil-in-water” emulsion followed by solvent evaporation. Sustained drug release (aqueous acetic acid solution, pH 5, UV-Vis spectrophotometry) over 7 days was seen for all the drug loaded nanoparticles, except with ofloxacin loading. The SPMNs were produced via co-precipitating with Fe2+ and Fe3+ in one step (CS SPMNs and CS-qC12 SPMNs) or two steps (chitosan-alginate-carrageenan (CS-Al-Car) SPMNs and chitosan-dextran sulfate (CS-DS) SPMNs). PLGA SPMNs and SMI-qC12 SPMNs were synthesized by activating the pristine iron oxide nanoparticles with oleic acid and (3-aminopropyl)triethoxysilane (3-APTES), respectively, before polymer coating. The polymer coated SPMNs were ex situ drug loaded by dispersing the SPMNs in anti-TB drug solution. Sustained drug release over 8 days was observed for the INH, ETA and RIF loaded polymer coated SPMNs. The resazurin microtiter assay (REMA) against TB mimic Mycobacterium Smegmatis (M. Smeg) was utilized to quantify the antimicrobial activity, via minimum inhibition concentration (MIC) determinations. The CS-DS nanoparticles were determined to be the optimal drug carrier with lower MIC values (CS-DS-OFX = 0.2441 μg/mL) compared to the free drugs (OFX = 0.5859 μg/mL).