| When developed as tools for applications within biological systems, RNA aptamers immediately face numerous obstacles, in particular nuclease degradation and post-selection 2' modification. This study aimed to develop a novel class of highly stable, 2'-fully modified RNA aptamers directly selectable from a fGmH RNA library with improved nuclease stability. The facile transcription of a fGmH (2'-F-dG, 2'-OMe-dA/dC/dU) RNA library was performed, from which aptamers were directly selected that bind Staphylococcus aureus Protein A (SpA). The superior nuclease and serum stability of these fGmH aptamers was demonstrated in comparison to 2'-partially modified RNA variants. Characterizations of fGmH RNA aptamers binding to purified SpA and to endogenous SpA present on the surface of S. aureus cells demonstrated fGmH RNA aptamer selectivity and stability. Significantly, fGmH RNA aptamers were able to functionalize, stabilize, and specifically deliver aggregation-prone silver nanoparticles (AgNPs) to S. aureus with SpA-dependent antimicrobial effects. Attempted selection of fGmH RNA aptamers against other targets, namely the PD-1 immune checkpoint, led to the selection of a single non-binding sequence during the selection against PD-1, as well as several non-binding sequence motif groups during the selection against PD-L1. Overall, this dissertation demonstrates the selection and deployment of Protein A binding fGmH RNA aptamers against S. aureus, discusses hypotheses and results aimed at explaining the selection of PD-1 and PD-L1 non-binding sequences, and describes a novel aptamer class with considerable potential to improve the in vivo applicability of nucleic acid-based affinity molecules. |
