Functionalized polymer nanofibrous substrates as capturing platforms for mycobacteria

[摘要] ENGLISH ABSTRACT : Tuberculosis (TB) remains one of the world's deadliest communicable diseases. In 2013, an estimated 9.0 million people developed TB and 1.5 million died from the disease. The treatment of children with TB is often not considered a priority by tuberculosis control programmes. Paediatric TB is frequently more difficult to diagnose due to non-specific clinical and radiological features as opposed to adult TB cases that are often easily recognizable and accompanied by a positive sputum smear test. Most cases of childhood TB are paucibacillary, and therefore mycobacterial culture of specimens is required to optimise diagnostic yield, which can take weeks. If the TB bacilli can be concentrated in specimens, this problem could be circumvented and rapid diagnosis could be possible using existing microscopy methods.In this thesis, styrene maleimide copolymer (SMI) derivatives were synthesized and electrospun to develop nanofibrous substrates with an affinity for the mycobacterial cell wall of Mycobacterium tuberculosis (Mtb) to potentially act as capturing platforms for these bacilli. SMA was modified with a variety of low molecular weight modification agents that were chosen based on their known or possible affinity for the mycobacterial cell wall before being electrospun into nanofibrous membranes. Prefabricated SMA nanofibers were also surface-functionalized with a lectin-binding protein, namely Concanavalin A (Con A).Affinity studies were carried out between the modified polymer nanofibers and an attenuated strain of Mtb, namely Mycobacterium bovis bacillus Calmette-Guérin (BCG) to evaluate the ability of each polymer nanofibrous substrate to capture BCG at decreasing concentrations. The successful capture of BCG onto the substrates was confirmed using fluorescence microscopy (FM). Analysis of the FM images revealed that SMA functionalized with Con A captured BCG the most effectively due to the saccharide binding properties of the protein. This interaction is specific between BCG and the Con A protein due to the mannose binding ability of Con A and the mannose molecules present on the outer cell surface of BCG. SMA modified with aliphatic quaternary ammonium moieties of chain lengths C8-C12 also showed exceptional capturing abilities through a combination of ionic and hydrophobic interactions. This interaction is non-specific as it is only dependent on the electrostatic and hydrophobic-hydrophobic interaction between BCG and the polymer nanofibrous surfaces. These interactions were visible even at the lowest tested BCG concentration.

[发布机构] Stellenbosch University