Silicon posts with similar topography containing only physisorbed lectins showed significantly less activity. These supports promoted microbe more » adhesion and colony formation in a lectin-specific manner. Arrays of circular polymer supports ten micron in diameter were generated on silicon substrates to provide discrete, covalent coupling sites for Triticum vulgare and Lens culinaris lectins. In this report, we evaluate the use of the block co-polymer, poly(glycidyl methacrylate)-block-4,4-dimethyl-2-vinylazlactone (PGMA-b-PVDMA), as a surface support for lectin-specific microbial capture. The capture of targeted microbes using surface immobilized lectins that recognize specific extracellular oligosaccharide moieties offers a non-destructive method for functional characterization based on EPS content. Microbial exopolysaccharides (EPS) play a critical and dynamic role in shaping the interactions between microbial community members and their local environment. These insights will aid in design of biofunctional interfaces with physicochemical surface properties favorable for capture and isolation of bacteria cells from solutions.
These findings emphasize the critical importance of the synthetic interface and the development of surfaces that combine high lectin densities with tailored physical features to drive high levels of capture. Statistical analysis of surface capture levels revealed that lectin surface density was the primary factor driving capture, as opposed to exopolysaccharide adhesin expression. Finally, to investigate the impact of cell surface parameters on capture, we used Agrobacterium tumefaciens cells genetically modified to allow manipulation of exopolysaccharide adhesin production levels. NPA surfaces containing 300 nm tall pillars further improved the detection limit to 2.1 × 10 2 cfu/mL, but also reduced the viability of captured cells. This detection limit was 1 order of magnitude lower than more » control lectin surfaces functionalized with standard, carbodiimide coupling chemistry. For flat polymer interfaces, bacteria were detected on the surface after incubation at a solution concentration of 10 3 cfu/mL, and a corresponding detection limit of 1.7 × 10 3 cfu/mL was quantified. Capture of Escherichia coli on lectin–polymer surfaces coated over both flat and NPA surfaces was then investigated. To introduce physical nanostructures into the attachment layer, nanopillar arrays (NPAs) of varied heights (3 nm) were then used to provide an underlying surface template for the functional polymer layer. Here, experimental parameters including polymer areal chain density, lectin molecular weight, and lectin coupling buffer were systematically varied to identify parameters driving highest azlactone conversions and corresponding lectin surface densities. The designer block copolymer poly(glycidyl methacrylate)-block-poly(vinyldimethyl azlactone) was used as a lectin attachment layer, and lectin coupling into the polymer film through azlactone–lectin coupling reactions was first characterized. This study provides a systematic investigation of physical and chemical surface parameters that influence bacteria capture over lectin-functionalized polymer interfaces and then applies these findings to construct surfaces with significantly enhanced bacteria capture. Lectin-functional interfaces are useful for isolation of bacteria from solution because they are low-cost and allow nondestructive, reversible capture.
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