Optimization and quantification of Urease in a magnetoresistive biochip platform with integrated Microfluidics

Débora Cristina Batista de Albuquerque

Key information

Authors:

Débora Cristina Batista de Albuquerque (Débora Cristina Batista de Albuquerque)

Supervisors:

Susana Isabel Pinheiro Cardoso de Freitas (Susana Isabel Pinheiro Cardoso de Freitas)

Published in

11/29/2017

Abstract

In recent years there has been an exploration of sustainable and environmental-friendly technologies for ground improvement to be used in civil engineering infrastructure developments. One of the most studied and promising biological ground improvement method is biocementation through microbially induced calcite precipitation (MICP). The biological induced precipitation of CaCO3 involves the use of bacteria capable of producing a high amount of precipitates within a short period of time in the presence of urea due to their high urease activity. The analysis of this enzyme allows then a possible method for quantifying the amount of biocement produced. The present thesis is dedicated to the quantification of urease present in a given soil sample in a way that can be used in situ. This is accomplished by employing a lab-on-a-chip (LOC) device utilizing magnetoresistive biochips as biosensors in tandem with a read-out electronic set-up, magnetic labels and an integrated microfluidics system. In this thesis it was also studied a method of urease sample preparation involving the use of a microfluidic mixer and magnetic separator. A calibration curve between 0.5 and 70 mg/ml was obtained using the biochip platform for a pure urease extract from Canavalia ensiformis. Urease from Bacillus pasteurii was grown and its urease activity was measured. The urease from B. pasteurii was not quantified using the platform since no magnetic signal could be detected, further optimization in the sample preparation being needed. The preparation of a urease sample was successfully carried out using only microfluids, though with lower sensitivity.