Surface modification of styrene maleic anhydride nanofibers for efficient capture of Mycobacterium tuberculosis

[摘要] ENGLISH ABSTRACT: Tuberculosis (TB) is a major cause of morbidity and mortality across the world, affecting adults and children. Children infected with TB differ from adults, as their immunological and patho-physiological response to the disease is different. Although there are a variety of tests available for TB diagnosis, they have limitations when used to diagnose paediatric TB. Children are also unable to generate sputum spontaneously when required for the use in culture or microscopy as diagnostic method. Children however do produce sputum, containing the TB bacilli, which they swallow. If the TB bacilli can therefore be retrieved from the stomach and tested, TB can be diagnosed using gastric samples.In this thesis, a variety of styrene maleimide copolymer (SMI) derivatives were prepared as potential M. tuberculosis-capturing platforms. This was done by modifying poly(styrene-co-maleic anhydride) (SMA) with a variety of primary amine compounds, selected based on possible chemical interactions with the M. tuberculosis cell wall. All the prepared copolymer derivatives were electrospun into nanofibrous mats using the single needle electrospinning technique to yield SMI nanofibers, functionalized with different compounds. Some of the functionalized SMI nanofibers were prepared by surface-functionalization of the polymer nanofibers after electrospinning and some by modification of the polymer before electrospinning.Affinity studies were conducted at neutral and low pH between the different functionalized SMI nanofibers and two mycobacterium strains, namely the bacillus Calmette-Guérin strain of Mycobacterium bovis (BCG) and M. tuberculosis, to evaluate the surfaces of the modified SMI nanofibers as mycobacterium-capturing platforms. The successful capture of BCG onto the surfaces of the various functionalized nanofibers was confirmed by SEM and fluorescence microscopy (FM). Analysis of the SEM and FM images indicated that the SMI nanofibers, functionalized with a C12 aliphatic quaternary ammonium moiety (SMI-qC12), captured BCG the most effectively through a combination of ionic and hydrophobic interaction. Concentration and time studies revealed that the extent of this interaction was dependent on incubation time and concentration of BCG. The affinity studies with BCG also concluded that the polymer used for the nanofibrous-capturing platform should not be too hydrophobic in character as this caused poor wetting of the functionalized nanofibers, thus preventing close contact with the mycobacteria and a reduction in the capture effectivity of the polymer nanofibers.The successful capture of M. tuberculosis onto the SMI-qC12 nanofibrous surface was confirmed by FM, light microscopy (LM) and polymerase chain reaction (PCR). The extent of this interaction was dependent on the concentration of M. tuberculosis. The detection of M. tuberculosis using FM and LM as detection methods was simplified by the tendency of M. tuberculosis to clump together in clusters on the hydrophobic surface of the SMI-qC12 nanofibers. As a result of this clustering, FM and LM were therefore regarded as feasible detection methods to image M. tuberculosis on the surface of the SMI-qC12 nanofibers, even at relatively low concentration of M. tuberculosis.

[发布机构] Stellenbosch University