Microfluidic Assay to Quantify the Adhesion of Marine Bacteria

Abstract

For both, environmental and medical applications, the quantification of bacterial adhesion is of major importance to understand and support the development of new materials. For marine applications, the demand is driven by the quest for improved fouling-release coatings. To determine the attachment strength of bacteria to coatings, a microfluidic adhesion assay has been developed which allows probing at which critical wall shear stress bacteria are removed from the surface. Besides the experimental setup and the optimization of the assay, we measured adhesion of the marine bacterium Cobetia marina on a series of differently terminated self-assembled monolayers. The results showed that the adhesion strength of C. marina changes with surface chemistry. The difference in critical shear stress needed to remove bacteria can vary by more than one order of magnitude if a hydrophobic material is compared to an inert chemistry such as polyethylene glycol.

Surface anchored metal-organic frameworks as stimulus responsive antifouling coatings

“…The bacterium used in this work was Cobetia marina, a model marine bacterium used in adhesion studies due to its relevance in marine biofouling [11,21,22]. As bacteria cause an additional XPS signal, only XRD was applicable for detecting changes in the SURMOF.…”

“…Microfluidic detachment assays were performed on Cu-SURMOF 2 (15 layers and 10 layers, respectively) and on hexadecanethiol (HDT) and mercaptohexadecanoid acid (MHDA) self-assembled monolayers (SAMs) as copper-free controls. Additionally, two types of surfaces with known low adhesion strength were included, polyethylene glycol (PEG) [11] and hyaluronic acid (HA) [25]. Both surfaces are known for their protein and cell resistance; thus, they provide a suitable control as typical inert surfaces.…”

“…Marine Broth (MB) and ASW were prepared according to the manufacturer's instructions. Culture and bacterial assays followed recently published protocols [11]. For bacterial assays, a single colony from an agar plate was inoculated into 20 ml MB overnight while shaking on a vibrational table (65 rpm) at room temperature.…”

“…The adhesion strength of the bacterium Cobetia marina on SURMOF 2 was quantified using a custom built microfluidic setup [15] which has previously been utilized to study cell and bacterial [11] adhesion on surfaces. The channels (dimensions: 13 mm × 1 mm × 140 μm) were positioned between a glass lid and the coated surface to be investigated.…”

“…Four fully assembled channel systems containing four surfaces with different coatings were mounted on the stage of an inverted microscope (Nikon TE-2000) allowing a simultaneous incubation of the samples. Bacteria suspensions with an OD 600 = 0.1 were injected into all four channels and incubated for 2 h as established in previous protocols [11]. After the incubation phase, medium from a reservoir was aspirated through the channels by a computer controlled syringe pump generating a flow which was increased stepwise by 26% every 5 s. The detachment was followed via video microscopy with a 40 × Ph2 objective and the fraction of adherent bacteria was determined every 5 s. The removal from all four channels was done sequentially.…”