Optical methods for ultrafast screening of microorganisms

Identifier:  TDX:2589

Handle: https://hdl.handle.net/20.500.11797/TDX2589

Authors:  Català García, Carme

Abstract:
This doctoral thesis intended to develop and optimize a method for multiplex detection and quantification of the most common microorganisms causing bacterial infections. This detection approach envisions to directly use different real human fluids avoiding thus, tedious pre-treatments of the samples with an unprecedented speed, low cost, and sensitivity. The design of the system is based on variations in the SERS intensity. This is accomplished using encoded plasmonic nanoparticles functionalized with bio-recognition elements. Consequently, when a sample containing the biological target to be identified interacts with the recognition elements attached to the nanoparticle, will induce an accumulation of them at the surface of the targeted microorganism. This particle aggregation on the bacteria membranes renders a dense array of inter-particle gaps in which the Raman signal is amplified by several orders of magnitude relative to the dispersed particles, enabling a multiplexed deterministic identification of the microorganisms. Quantification is achieved by passing the sample through a microfluidic device with a collection window where a laser interrogates and classifies the bacteria–nanoparticle aggregates in real time. Additionally, a comparison between two of the most common bio-recognition elements (antibodies and aptamers) was performed. This new pathogen detection system opens exciting prospects for fast inexpensive diagnosis of bacterial infections.