Cell-microstructured surface interactions
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Amperometric biosensors were fabricated in a compact three-electrode flow-injection analysis system. Gold working electrodes were electrochemically deposited with arrays of gold nanoparticles and functionalized with glucose oxidase (GOx) via self-assembled monolayer (SAMs). The biosensing system exhibited fast response (response time as short as 5 s), good sensitivity (ca. 400 nA/mM/cm2), high stability (97.6% to 95.5% of initial activity between 7 and 30 days, respectively) and reproducibility (relative standard deviation of 4.2%), wide linear detection range (upper limit up to 20 mM) and an ultra-small sample size of approximately 10 µl per assay. The amperometric biosensors were applied to investigate the cause of decreasing enzymatic activity in the repeated standard spectrophotometric assay with o-Dianisidine as the indicator. Electrochemical detection results suggest the instability to be due to the deposition onto the enzyme electrode surface of the oxidized product of o-dianisidine, 3,3-dimethoxy-4,4-diiminodiphenoquinone. To explore the promise for anti-biofouling activity in implantable biosensors, cell-microstructured surface interactions were investigated. ArF excimer laser direct-writing ablation was used to fabricate microwell patterns with precise control of size and spacing on glass. In terms of cell adhesion and locomotion, cells tended to avoid microwells with a comparable size to their own, suggesting the potential of using microstructures to reduce biofouling. The impact of laser-ablated microstructures on cells in terms of cell viability, adhesion, morphology, proliferation and cytoskeleton organization over time was further investigated. Microstructures with variable architectures exhibited anti-cell adhesion and proliferation properties. F-actin and vinculin of fibroblasts on the microstructures appeared less-developed and less-defined than control (flat surface) in all time. Microstructure spacing ratio (well-to-well distance over microwell diameter), had a significant impact on the cellular response. The most efficient architecture was chosen for reducing cell adhesion and proliferation. These experiments support the application of surface micro-topography to modulate cell adhesion, morphology, locomotion and proliferation of cells without reducing cell viabilities.