Development of a microfluidic biochip for online monitoring of fungal biofilm dynamics

Abstract

Microfabricated biochips are developed to continuously monitor cell population dynamics in a non-invasive manner. In the presented work we describe the novel combination of contact-less dielectric microsensors and microfluidics to promote biofilm formation for quantitative cell analysis. The cell chip consists of a polymeric fluidic (PDMS) system bonded to a glass wafer containing the electrodes while temperature and fluid flow are controlled by external heating and pumping stations. The high-density interdigitated capacitors (microIDES) are isolated by a 550 nm multi-passivation layer of defined dielectric property and provide stable, robust and non-drifting measurement conditions. The performance of this detector is evaluated using various bacterial and yeast strains. The high sensitivity of the developed dielectric microsensors allows direct identification of microbial strains based on morphological differences and biological composition. The novel biofilm analysis platform is used to continuously monitor the dynamic responses of C. albicans and P. pastoris biofilms to increased shear stress and antimicrobial agent concentration. While the presence of shear stress triggers significant changes in yeast growth profiles, the addition of 0.5 microg mL(-1) amphotericin B revealed two distinct dynamic behaviors of the C. albicans biofilm. Initially, impedance spectra increased linearly at 30 Omega h(-1) for two hours followed by 10 Omega h(-1) (at 50 kHz) over 10 hours while cell viability remained above 95% during fungicide administration. These results demonstrate the ability to directly monitor dielectric changes of sub-cellular components within a living cell population.

Pronounced Effect of the Nature of the Inoculum on Biofilm Development in Flow Systems

“…Biofilm growth rates have been determined by various techniques, such as fluorescence in situ hybridization (FISH) (12,31), measuring the incorporation of radioactive substances like [ 3 H]thymidine and 32 P (8, 9), microscopy (3,13,17), measuring the total increase in biofilm mass (both cells and extracellular polymeric substances) (24,28), colorimetric 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenyl-amino)carbonyl]-2H-tetrazolium hydroxide (XTT) assays (26), or measurement of amide II bands, as determined by attenuated total reflectanceFourier transform infrared spectroscopy (6). Some of the above-mentioned techniques suffer the drawback that the bio-films have to be sacrificed with sampling or that the measured increases do not distinguish between live and dead matter in the biofilm (i.e., increases measured might not represent an accurate increase in viable cell numbers).…”

CO 2 Production as an Indicator of Biofilm Metabolism

“…In brief, a nonexhaustive list of techniques that deal only with online monitoring increase (whether of biotic or abiotic origin) and the decrease of biofilms includes quartz crystal microbalances (48), large area photometry (3,33), electrical capacitance (31), fiber optical devices (49), differential turbidity measurement devices (20), microfluidic biochips (39), optical coherence tomography (13), pressure drop or friction resistance (24), and heat transfer resistance (28). Techniques that provide information about the physical structure and chemical properties of biofilms are nuclear magnetic resonance (44), attenuated total reflectance-Fourier transform infrared spectroscopy (7), and photoacoustic spectroscopy (43).…”

Microfluidics:A Boon for Biological Research

“…A microfluidic device was used to control and monitor the environment of biofilms caused by Candida albicans, the organism responsible for candidiasis. A device with dielectric sensors was created to measure the real-time response of C. albicans biofilms to different shear stresses and antibiotic concentrations 25 . The findings suggested that an increased shear stress led to considerable changes in the biofilm formation patterns, whereas the addition of an antibioticamphotericin B resulted in two distinct forms of dynamic behaviour of the biofilm.…”