PhD: Beatriz Serrano do Couto

Director:

Dr Maria Soler, Senior Researcher, NanoBiosensors and Bioanalytical Applications group ICN2

Short Abstract:

This PhD Thesis develops and analytically validates nanophotonic biosensors for rapid, precise molecular diagnosis of infectious diseases. It addresses two major challenges: surveillance of zoonotic coronaviruses at the animal–human interface, and diagnosis of bacterial sexually transmitted infections and antimicrobial resistance markers. Surface plasmon resonance and bimodal waveguide interferometry were investigated for direct, label-free detection of pathogen-specific RNA and DNA sequences. Robust nucleic acid biofunctionalization strategies were established for gold and silicon nitride surfaces by optimizing surface chemistry, probe immobilization, hybridization conditions, and regeneration. Coronavirus assays were developed and validated using synthetic targets, in vitro transcribed RNA, and animal-derived samples, demonstrating applicability to wildlife and veterinary surveillance. The work was extended to Neisseria gonorrhoeae and Chlamydia trachomatis and to discrimination of a clinically relevant single-nucleotide mutation linked to ciprofloxacin resistance. Overall, this Thesis establishes a framework for label-free nucleic acid detection with potential integration into multiplexed, automated, portable diagnostic platforms.

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