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Polymeric test surfaces of P(L-D,L)LA and of a P(L-D,L)LA:PLGA blend decorated with 25 nanopillar covered fields, were used to investigate differences in growth of bone marrow stem cells (BMSC) and osteosarcoma cells (Saos-2). The fields were populated with pillars (ca. 900 nm tall, 200 nm×200 nm area) separated systematically from each other with 1-10 μm gaps. Saos-2 cells populated fields decorated with pillars 1 μm apart but they avoided pillar-free surfaces. In contrast, BMSCs avoided fields with interpillar distances <2 μm. Both BMSCs and Saos-2 cells aligned in the direction of the shorter distance when at least one of the interpillar distances was greater than 1.5 μm. Coating the P(L-D,L)LA surfaces with cell adhesive protein fibronectin enabled the BMSC to populate fields with high pillar density which they had avoided when uncoated. Decreasing the stiffness of the film surface by using a blend of (P(L-D,L)LA and PLGA) made them more acceptable for attachment by the BMSC cells., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Conjugates of avidin with ferrocene and with microperoxidase 8 have been used as electrochemically active molecular building blocks. Assemblies of the conjugates with biotinylated glucose oxidase or lactate oxidase on gold electrodes were tested as enzyme sensors for glucose and lactate. The electrochemical detection is based either on ferrocene-mediated oxidation of the substrate in oxygen-free solution, or on microperoxidase-catalysed reduction of H2O2 which is enzymatically produced from the substrate and molecular oxygen. Glucose and lactate were detectable with both detection principles in concentrations down to 1 or 0.1 mM, respectively. The molecular architecture concept allows quick adaptation of the sensors to other analytes, and it provides a platform for arrays of sensors with different selectivity.

Abstract: We developed a simple two-step replication method to transfer arrays of high aspect ratio nanopillars into films of poly(l-d,l-lactic acid) (PLLA). Such structures are promising model surfaces for tissue engineering applications. From arrays of 1μm high and 200nm wide pillars produced with e-beam lithography and reactive ion etching negative replicas were first formed by polydimethylsiloxane (PDMS) casting. The final replicates were produced by solvent casting from 1% to 4% solutions of PLLA in chlorinated solvents on the PDMS templates. The silicon masters provide excellent stability and reusability, whereas the flexibility and low surface energy of the PDMS are necessary for the separation of the casts made with PLLA, a brittle material which is difficult to handle. AFM and SEM characterizations confirmed a high fidelity reproduction of the structures with aspect ratios of 1:5. In vitro tests using mouse neural stem cells seeded on nanopillars showed that the cells sense the nano-sized topography and respond accordingly by orienting themselves. [Copyright &y& Elsevier]