Bacteria that adhere to the surfaces of implanted medical devices can cause catastrophic infection. Since chemical modifications of materials' surfaces have poor long-term performance in preventing bacterial buildup, approaches using bactericidal physical surface topography have been investigated. The authors used Nanoimprint Lithography was used to fabricate a library of biomimetic nanopillars on the surfaces of poly(methyl methacrylate) (PMMA) films. After incubation of Escherichia coli (E. coli) on the structured PMMA surfaces, pillared surfaces were found to have lower densities of adherent cells compared to flat films (67%-91% of densities on flat films). Moreover, of the E. coli that did adhere a greater fraction of them were dead on pillared surfaces (16%-141% higher dead fraction than on flat films). Smaller more closely spaced nanopillars had better performance. The smallest most closely spaced nanopillars were found to reduce the bacterial load in contaminated aqueous suspensions by 50% over a 24-h period compared to flat controls. Through quantitative analysis of cell orientation data, it was determined that the minimum threshold for optimal nanopillar spacing is between 130 and 380 nm. Measurements of bacterial cell length indicate that nanopillars adversely affect E. coli morphology, eliciting a filamentous response. Taken together, this work shows that imprinted polymer nanostructures with precisely defined geometries can kill bacteria without any chemical modifications. These results effectively translate bactericidal nanopillar topographies to PMMA, an important polymer used for medical devices.

Ability to perform cytogenetic interrogations on circulating tumor cells (CTCs) from the blood of cancer patients is vital for progressing toward targeted, individualized treatments. CTCs are rare compared to normal (bystander) blood cells, found in ratios as low as 1:10 9 . The most successful isolation techniques have been immunocytochemical technologies that label CTCs for separation based on unique surface antigens that distinguish them from normal bystander cells. The method discussed here utilizes biotin-tagged antibodies that bind selectively to CTCs. The antibodies are introduced into a suspension of blood cells intending that only CTCs will display surface biotin molecules. Next, the cell suspension is passed through a microfluidic channel that contains about 9000 transverse, streptavidin coated posts. A CTC making contact with a post has the opportunity to engage in a biotin-streptavidin reaction that immobilizes the cell. Bystander blood cells remain in suspension and pass through the channel. The goal of the present study is to establish the technical performance of these channels as a function of antigen density and operating conditions, especially flow rate. At 18 lL/min, over 70% of cells are captured at antigen densities greater than 30 000 sites/cell while 50% of cells are captured at antigen densities greater than 10 000. It is found that lower flow rates lead to decreasing cell capture probabilities, indicating that some streamlines develop which are never close enough to a post to allow cell-post contact. Future modeling and streamline studies using computational fluid dynamics software could aid in optimization of channel performance for capture of rare cells.

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Advanced molecular electronic components remain vital for the next generation of miniaturized integrated circuits. Thus, much research effort has been devoted to the discovery of lossless molecular wires, for which the charge transport rate or conductivity is not attenuated with length in the tunneling regime. Herein, we report the synthesis and electrochemical interrogation of DNA-like molecular wires. We determine that the rate of electron transfer through these constructs is independent of their length and propose a plausible mechanism to explain our findings. The reported approach holds relevance for the development of high-performance molecular electronic components and the fundamental study of charge transport phenomena in organic semiconductors.