Dynamic Dosing Assay Relating Real-Time Respiration Responses of Staphylococcus aureus Biofilms to Changing Microchemical Conditions

Abstract

Bacterial biofilms are a metabolically heterogeneous community of bacteria distributed in an extracellular matrix comprised primarily of hydrated polysaccharides. Effective inhibitory concentrations measured under planktonic conditions are not applicable to biofilms, and inhibition concentrations measured for biofilms vary widely. Here, we introduce a novel microfluidic approach for screening respiration inhibition of bacteria in a biofilm array morphology. The device geometry and operating conditions allow antimicrobial concentration and flux to vary systematically and predictably with space and time. One experiment can screen biofilm respiratory responses to many different antimicrobial concentrations and dosing rates in parallel. To validate the assay, onset of respiration inhibition following NaN₃ exposure is determined optically using an O₂-sensing thin film. Onset of respiration inhibition obeys a clear and reproducible pattern based on time for diffusive transport of the respiration inhibitor to each biofilm in the array. This approach can be used for high-throughput screening of antimicrobial effectiveness as a function of microbial characteristics, antimicrobial properties, or antimicrobial dosing rates. The approach may also be useful in better understanding acquired antimicrobial resistance or for screening antimicrobial combinations.

Pore‐scale water dynamics during drying and the impacts of structure and surface wettability

“…Pseudo‐two‐dimensional emulated soil micromodels were fabricated from two‐dimensional (2‐D) micromodel patterns using standard methods of photolithography and soft lithography as previously described [ Deng et al ., ; Markov et al ., , ]. Micromodel patterns were designed with three identical channels each containing a 1 mm × 1 cm soil microstructure region.…”

“…[ Deng et al, 2013;Markov et al, 2010aMarkov et al, , 2010b. Micromodel patterns were designed with three identical channels each containing a 1 mm 3 1 cm soil microstructure region.…”

Bacterial Extracellular Polymeric Substances Amplify Water Content Variability at the Pore Scale

“…Microfluidic devices were fabricated using standard photolithography and soft lithography methods as described previously (Deng et al, 2013). Briefly, polydimethylsiloxane (PDMS, Sylgard 184, Dow Corning, Midland, MI), a two-part silicone elastomer, was cast over a photolithography master, then cured at 60 • C for 6 h, then cut out using a scalpel and punched on both side using a 4-mm biopsy punch (Integra R Miltex).…”

Selective deposition of chemically-bonded gold electrodes onto PDMS microchannel side walls

“…The channel contained two rows of posts measuring 200 lm in diameter. Microfluidic masters were created from SU-8 2100 (Microchem, Newton, MA) using photolithography as previously described [23]. Detailed fabrication parameters can be found in Table S Replicate devices were cast from masters in PDMS using standard soft lithography methods [24].…”