(100h) Nanostructured Polymer Interfaces for Improved Lectin-Based Capture and Detection of Bacteria

There is critical need for developing materials and interfaces that can be used to capture and isolate bacteria for rapid, culture-free sensing at high sensitivity. Lectin interfaces are considered to be promising for affinity-based microorganism capture and isolation from complex samples, including blood, urine, and wastewater. However, there are limitations associated with the practical use of many lectin-based interfaces due to the fact that the equilibrium dissociation constants (K_D) of lectin-carbohydrate interactions are higher than antibody-antigen binding constants by 2-3 orders of magnitude, resulting in poor cell capture efficiency.

In this work, we have designed surfaces that combine reactive polymer coatings that offer control of biomolecule surface density with nanoscale surface structures that allow for precise control of physical surface topology in order to improve cell capture. First we characterize the critical interface parameters that impact lectin coupling onto flat, reactive azlactone-based block copolymer films that consist of poly(glycidyl methacrylate)-block-poly(vinyldimethyl azlactone) (PGMA₅₆-b-PVDMA₁₇₅). Second, we incorporate well-controlled physical nanostructures into the films using nanospike arrays (black silicon) fabricated from reactive ion etching, which provide underlying physical structures for the polymer coating. The microbe detection sensitivity and bactericidal impact of the both flat and nanopillar polymer surfaces are then characterized.

Our data indicate that the physicochemically-optimized surfaces enhance capture and detection of bacteria from solutions by two orders of magnitude compared to control surfaces, which were lectins immobilized to flat surfaces using standard carbodiimide coupling chemistry (EDC/NHS). We found that flat PVDMA surfaces alone improve the limit of detection (LOD) by one order of due to the fact that the PVDMA polymer offered higher levels of lectin surface density. Addition of the nanopillar arrays to the PVDMA-coated surfaces improved the sensitivity by an additional order of magnitude, down to 10² CFU/mL. This is likely due the three-dimensional surface structures that provided enhanced contact with the targeted bacteria. This level of sensitivity gives our interfaces relevance to a variety of bacterial detection applications which include detection in water/wastewater systems (required LOD =10³-10⁵ CFU/mL), urinary tract infections (required LOD = 10³ CFU/mL), and blood infections (required LOD = 1-100 CFU/mL).