AN INTEGRATED MICROSYSTEM FOR BACTERIAL BIOFILM DETECTION AND TREATMENT
Kim, Young Wook
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Bacterial biofilms cause severe infections in clinical fields and contamination problems in environmental facilities. Due to the unique complex structure of biofilms that comprise diverse polysaccharides and bacteria, traditional antibiotic therapies require a thousand times higher concentration compared to non-biofilm associated infections. The early detection of biofilms, before their structures are fully established in a given host/environment, is critical in order to eradicate them effectively. Also, the development of a new innovative biofilm treatment method that can be utilized with a low dose of antibiotic would be extremely important to the medical community. In this dissertation, a biofilm sensor and a new biofilm treatment method were independently developed to detect and treat biofilm communities, respectively. Furthermore, an integrated microsystem was demonstrated as a single platform of the sensor with the treatment method. The sensor was based on the surface acoustic wave (SAW) detection mechanism, which isn extremely sensitive for biofilm monitoring (hundreds of bacterial population detection limit) and consumes very low power (~100 µW). A piezoelectric ZnO layer fabricated by a pulsed laser deposition process was a key material to induce homogeneous acoustic waves. Reliable operation of the sensor was achieved using an Al2O3 film as a passivation layer over the sensor to protect ZnO degradation from the growth media. The sensor successfully demonstrated real-time monitoring of biofilm growth. The new biofilm treatment was developed based on the principles of the bioelectric effect that introduces an electric field along with antibiotics to biofilms, demonstrating significant biofilm inhibition compared to antibiotic treatment alone. Specifically, the new bioelectric effect was implemented with a superpositioned (SP) electric field of both alternating and direct current (AC and DC) and the antibiotic gentamicin (10 µg/mL). With the SP field treatment, significant biofilm reduction was demonstrated in total biomass (~ 71 %) as well as viable bacterial density (~ 400 times respected to the only antibiotic therapy) of the treated biofilms. This method was transferred to a microfluidic system using microfabricated planar electrodes. The microsystem-level implementation of the bioelectric effect also showed enhanced biofilm reduction (~ 140 % total biomass reduction improvement). The integrated system was based on the SAW sensor with the addition of coplanar thin electrodes to apply electric signals for the biofilm treatment. The chip was tested with two bacterial biofilms (Escherichia coli and Pseudomonas aeruginosa) that are clinically relevant strains. In both biofilm experiments, the integrated system demonstrated successful real-time biofilm monitoring and effective biofilm inhibition. This systematic integration of a continuous monitoring method with a novel effective treatment technique is expected to advance the state of the art in the field of managing clinical and environmental biofilms.