Abstract
M.Sc. (Nanoscience)
Ochratoxin A and Aflatoxin B1 are important food contaminates as they are known to be
mutagenic, genotoxic, nephrotoxic, hepatotoxic, immunosuppressive and teratogenic to
both animals and humans. These mycotoxins are associated with the contamination of
food stuff such as grapes, maize, red pepper, meat, milk, beans and processed
products from contaminated raw material. Current physical, biological and chemical
methods employed to improve the safety of food often compromise the nutritional value
and result in huge losses. The alternative to these treatments are addition of
supplements with protective properties to reduce the toxicity of mycotoxins or prevent
their formation. The work presented in this dissertation reports an attempt to develop
such materials to prevent damage caused by ochratoxin A and aflatoxin B1. This was
done through the synthesis; characterisation and cytotoxicity study of chitosan
nanoparticles with methanolic plant extracts (L. leonurus, M. longifolia and A.
montanus). Inhibition of cellular damage due to mycotoxins for possible application in
prevention of cellular damage by mycotoxins also presented.
Chitosan nanoparticles were synthesised using an ionic gelation method with sodium
triphosphate as the cross linker. The methanolic medicinal plants extracts were
incorporated into the chitosan solution before synthesising nanoparticles, and
nanoparticle synthesis initiated by the addition of sodium triphosphate solution. The
synthesised products were characterised using zetasizer, transmission electron
microscopy, x-ray diffraction and Fourier-transform infrared spectroscopy. The extracts’
antioxidant ability was evaluated before incorporation into chitosan using 2, 2-diphenyl-
1-picrylhydrazy (DPPH) radical scavenging assay. This assay was performed using UVvis
spectroscopy. The cytotoxicity of the synthesised nanoparticles was assessed using
a Vero cell line and by evaluating the cell viability with an MTS assay. The nanoparticles were successfully synthesised and showed the presence of different
functional groups as expected. Plain chitosan nanoparticles were roughly spherical
shaped and had smooth surfaces, nanoparticles containing extracts similarly were
spherical in shape as well but had rougher surfaces when visualised under TEM. All
nanoparticles had positive zeta potentials between 26 – 28 mV. The average particle
sizes ranged between 31 – 65 nm as measured using TEM and average particle sizes
obtained using zetasiser was 78 – 190 nm. The cytotoxicity studies of plain
nanoparticles and nanoparticles with extract showed that the synthesised nanomaterials
were not toxic even at concentration of 500 μg/ml and less than 20% of the Vero cells
were affected under these conditions.