Nonfouling coatings, based on surface-tethered, hydrophilic polymer chains, have widespread application in areas such as biosensing, medical devices, and biotechnology. Self-organization of polymers is a particularly attractive approach given its simplicity and cost-effectiveness in the application. Here we present a new class of polymers based on the polycationic poly(L-lysine)-graft-poly(ethylene glycol) copolymer (PLL-g-PEG) with a fraction of the amine-terminated lysine side chains covalently conjugated to 3,4-dihydroxyphenylacetic acid (DHPAA). This copolymer is shown to adsorb and self-organize as a confluent monolayer on negatively charged titanium oxide surfaces, driven by long-range electrostatic attraction, while the catechol groups of DHPAA spontaneously engage in strong, coordinative binding to the substrate surface, similar to the biomimetic dihydroxyphenylalanine (DOPA) found in mussel adhesive proteins. The adsorption kinetics and resulting polymer coverage are demonstrated to critically depend on (a) a rational design of the copolymer architecture with a compromise between sufficient positive charges in the PLL backbone and a minimal grafting density of DHPAA groups and (b) optimum choice of ionic strength and temperature of the assembly solution. PLL-graft-(DHPAA; PEG) adlayers exhibit excellent resistance to nonspecific protein (fibrinogen) adsorption. To test the chemical stability of the polymeric layer, coated substrates were exposed to high ionic salt solutions and proved to remain nonfouling thanks to stable catechol-substrate anchorage, in stark contrast to the control PLL-g-PEG copolymer that desorbed under these conditions as a consequence of screening of the (purely) electrostatic surface forces. Furthermore, polymer-coated substrates resisted attachment of the cyanobacterium Lyngbya sp. over a time frame of at least 100 days.

A new chemical vapour deposition setup for the generation of anti-adhesive coatings on Si stamps used in nanoimprint lithography has been developed. This is suitable for controlled co-evaporation of more than one type of silane by directly injecting a premixed silane into an evacuated deposition reactor through a septum. This process was found to be very flexible and resulted in reproducible coatings. A surface coated with a mixture of mono-and trichlorosilanes shows a higher water contact angle than those of individual coatings, which is attributed to the interaction between the two types of silane molecules. In addition, the influence of process parameters, e.g. water content, temperature and number of imprints, on the coating quality will be discussed.

Laccases (Lac) are oxidizing enzymes with a broad range of applications, for example, in soil remediation, as bleaching agent in the textile industry, and for cosmetics. Protecting the enzyme against degradation and inhibition is of great importance for many of these applications. Polymer vesicles (polymersomes) from poly(N-vinylpyrrolidone)-block-poly(dimethylsiloxane)-block-poly(N-vinylpyrrolidone) (PNVP-b-PDMS-b-PNVP) triblock copolymers were prepared and investigated as intrinsically semipermeable nanoreactors for Lac. The block copolymers allow oxygen to enter and reactive oxygen species (ROS) to leave the polymersomes. EPR spectroscopy proved that Lac can generate ROS. They could diffuse out of the polymersome and oxidize an aromatic substrate outside the vesicles. Michaelis-Menten constants Km between 60 and 143 μM and turn over numbers kcat of 0.11 to 0.18 s(-1) were determined for Lac in the nanoreactors. The molecular weight and the PDMS-to-PNVP ratio of the block copolymers influenced these apparent Michaelis-Menten parameters. Encapsulation of Lac in the polymersomes significantly protected the enzyme against enzymatic degradation and against small inhibitors: proteinase K caused 90% less degradation and the inhibitor sodium azide did not affect the enzyme's activity. Therefore, these polymer nanoreactors are an effective means to stabilize laccase.

Simultaneous detection of multiple biomarkers, such as extracellular signaling molecules, is a critical aspect in disease profiling and diagnostics. Precise positioning of antibodies on surfaces, especially at the micro- and nano- scale, is important for the improvement of assays, biosensors, and diagnostics on the molecular level, and therefore, the pursuit of device miniaturization for parallel, fast, low-volume assays is a continuing challenge. Here, we describe a multiplexed cytokine immunoassay utilizing electron beam lithography and a trehalose glycopolymer as a resist for the direct writing of antibodies on silicon substrates allowing for micro- and nano-scale precision of protein immobilization. Specifically, anti-interleukin 6 (IL-6) and anti-tumor necrosis factor alpha (TNFα) antibodies were directly patterned. Retention of the specific binding properties of the patterned antibodies was shown by the capture of secreted cytokines from stimulated RAW 264.7 macrophages. A sandwich immunoassay was employed using gold nanoparticles and enhancement with silver for the detection and visualization of bound cytokines to the patterns by localized surface plasmon resonance detected with dark field microscopy. Multiplexing with both IL-6 and TNFα on a single chip was also successfully demonstrated with high specificity and in relevant cell culture conditions and at different times after cell stimulation. The direct fabrication of capture antibody patterns for cytokine detection described here could be useful for biosensing applications.