DEVELOPMENT OF NOVEL NANOMATERIALS FOR MICROBIOLOGICAL APPLICATIONS: LABELLING, DETECTION, AND DELIVERY

Microorganisms are believed to be the origin of life on earth responsible for the creation of living cells and the beginning of biological evolution. In fact, humans have more bacterial cells in their bodies than human cells, making the study of microbes pivotal to the progress of medicinal sciences. However, microbiology struggles with long processing times and must overcome several technological hurdles before fully accomplishing its potential. Incorporating nanotechnology into microbiological applications provides new methods to study and exploit microorganisms. While both fields are highly studied and have existed for years, interdisciplinary research practices combining nanotechnology and microbiology remain in their infancy. This thesis aims to engineer custom-designed nanomaterials for microbiological applications.

Before the biological manipulation of nanomaterials, it is essential to prepare them for the naturally complex biological environment. Nanomaterials, specifically quantum dots and gold nanoparticles, were synthesised and conjugated to targeting moieties known as aptamers. Their properties were tailored by modifying their size and surface environment to fit the requirements of each application. This allowed for labelling, detection, and delivery systems of bacteriaLabelling of cells can help detect microorganisms and track their behaviour and cellular mechanisms. Traditionally, this is done using organic fluorophores that present drawbacks, such as photobleaching and limited stability. In this thesis, biofunctionalisedIIInanoparticles are used to target and label bacterial cells. Opening a prospect for detecting colonies with high sensitivity to low concentrations of bacteria and high stability in diverse environments.

These Biofunctionalised nanoparticles synthesised to label the cells were used to address the rise of superbugs (multi-resistant bacteria). The nanoparticles were customised and employed in a Förster resonance energy transfer (FRET) based aptasensor. First gold nanoparticles and quantum dots, linked via an aptamer, were considered as a FRET pair. The possibility of a fluorescence turn-on sensor was studied. Then, following the same principle, quantum dot to quantum dot pair was considered for a ratiometric sensor. The FRET efficiency of both of these pairs was measured and improved via optimisation of FRET conditions.

In addition, living cells (such as bacteria) may hold the answer to superior drug delivery with higher efficiencies, stability, and biocompatibility. Therefore, outer membrane vesicles known as nature’s own nanoparticles derived from bacteria cells were isolated and successfully loaded with functionalised nanoparticles. As part of this work, the stability of the system was investigated. As a result, the outer membrane vesicles were unharmed, offering a potentially versatile method for customised delivery vehicles.

The methods used in this thesis, such as fluorescent labelling, specific delivery vehicles and faster bacterial detection, are evidence of the application of nanotechnology for the advancement of microbiological research. By bringing the technology to science, this thesis will aid in developing the field of microbiology and highlighting the promising potentials resulting from interdisciplinary research.