Site-Selective Surface Modification Using Enzymatic Soft Lithography

Surface modification with functional polymers or molecules offers great promise for the development of smart materials and applications. Here, we describe a versatile and easy-to-use method of site-selective surface modification based on the ease of microcontact printing and the exquisite selectivity of enzymatic degradation. A micropatterned poly-l-lysine (PLL) layer on solid substrates was prepared by enzymatic degradation using trypsin enzyme immobilized on a prestructured poly(dimethlylsiloxane) (PDMS) stamp. After the enzymatic degradation of PLL and the removal of the degradation products, very well defined patterning was revealed over a large scale by fluorescence microscopy and atomic force microscopy (AFM). We investigate the advantage of our method by comparison with traditional microcontact printing and found that lateral diffusion was reduced, yielding a more accurate reproduction of the master. We also demonstrate that the stamp can be reused without reinking. The patterned surface was used for site-selective modification. The strategy was applied to two applications: the first is dedicated to the creation of amino-silane patterned surfaces, and the second illustrates the possibility of patterning polyelectrolyte multilayered thin films

Concentration Mediated Structural Transition of Triblock Copolymer Ultrathin Films

X-ray reflectivity, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurement techniques are used to study the structural changeover as a function of concentration of poly­(ethylene oxide)-poly­(propylene oxide)-poly­(ethylene oxide) (PEO-PPO-PEO) triblock copolymer diluted in toluene spin-coated as ultrathin films on hydrophilic Si substrate. A lamellar structure made of three alternating incomplete bilayers is observed until the concentration of copolymer solution attains a threshold value of about 3.6–4 g/L. Around this concentration and beyond, the entanglement of polymer chains takes place during drying and the growth of a homogeneous film made of complete bilayers on Si substrate is observed. The strong hydrophilic nature of the Si substrate dictates the growth of this amphiphilic copolymer. We evidence that the lower part of the films is made of hydrophilic PEO blocks attached to the substrate while the hydrophobic PPO blocks are directed toward air

Quantitative PEEM and Raman Study of Nanorough Au SERS-Active Substrates for Molecular Sensing Applications

Surface-enhanced Raman scattering (SERS) is a well-established surface-sensitive technique for detecting trace amounts of molecular analytes. While the impact of surface singularities on plasmonic materials has been widely studied, the fabrication of cost-effective, efficient SERS substrates remains a challenge. In this paper, we present the study of large-area nanorough Au SERS-active substrates, elaborated by thermal evaporation deposition by photoemission electron microscopy (PEEM), a high-resolution near-field mapping technique, to access the statistical properties of the hot-spot distribution. We experimentally demonstrate that the near-field PEEM and far-field Raman statistical signatures of nanorough Au surfaces are quantitatively correlated when used for molecular sensing. The maximum of the SERS signal of thiophenol (TP) molecules diluted to 10–6 M is observed near the film percolation threshold for which the hot-spot density is maximum. Finally, SERS measurements from solutions of TP, crystal violet, and rhodamine B molecules at 10–8 M demonstrated the sensitivity of our substrates for molecular sensing

Improved Colloidal Stability of Bacterial Cellulose Nanocrystal Suspensions for the Elaboration of Spin-Coated Cellulose-Based Model Surfaces

Well-dispersed suspensions are a prerequisite when preparing smooth model surfaces based on neutral bacterial cellulose nanocrystals (BCNs). However, neutral nanocrystal suspensions present pronounced particle aggregation. Carboxymethyl cellulose (CMC) or xyloglucan (XG) was therefore added to aggregated BCN suspensions. Turbidity measurements, polysaccharide content, and transmission electron microscopy (TEM) analysis revealed that aggregation of BCNs in CMC/BCN and XG/BCN suspensions is dependent on the concentration of CMC and XG in the suspensions. CMC enhances BCN dispersion above the concentration ratio of 0.05. In the case of XG, a better colloidal stability is observed above the concentration ratio of 0.5. Atomic force microscopy (AFM) investigations demonstrated that cellulose-based model surfaces, spin-coated from CMC/BCN or XG/BCN solutions, exhibited more uniform topography and less roughness than the reference BCN model surface

Reproductive parameters in the control group and in the 50 μg L^-1 fenoxycarb-exposed group.

<p>Pairing success in percent (A), success of fertilization in paired gammarid in percent (B), number of fertilized eggs per female (mean±standard deviation; numbers above the bars indicate the number of females that were observed) (C) and embryo viability in percent (50 embryos/condition) (D). Asterisks indicate significant differences compared to the control group.</p

Experimental design and measured endpoints in <i>G</i>. <i>fossarum</i> exposed to 50 μg L^-1 fenoxycarb.

<p>Experimental design and measured endpoints in <i>G</i>. <i>fossarum</i> exposed to 50 μg L^-1 fenoxycarb.</p

Fenoxycarb exposure disrupted the reproductive success of the amphipod <i>Gammarus fossarum</i> with limited effects on the lipid profile

<div><p>Insect growth regulator insecticides mimic the action of hormones on the growth and development of insect pests. However, they can affect the development of non-target arthropods. In the present study, we tested the effects of the growth regulator insecticide fenoxycarb on several endpoints in the freshwater crustacean <i>Gammarus fossarum</i> (Amphipoda). Females carrying embryos in their open brood pouch were exposed to 50 μg L^-1 fenoxycarb throughout the entire oogenesis (i.e. 21 days). After exposure, newborn individuals from exposed embryos were removed from the maternal open brood pouch for lipidomic analysis, while males were added to assess the reproductive success. After fertilization, the lipid profile, energy reserve content (lipids, proteins and glycogen), and activity of phenoloxidase − an enzyme involved in the immune response − were measured in females. No significant effect of fenoxycarb exposure was observed on the lipid profile of both newborn individuals and females, while reproductive success was severely impaired in exposed females. Particularly, precopulatory behavior was significantly reduced and fertilized eggs were unviable. This study highlighted the deleterious effects of the insect growth regulator fenoxycarb on gammarid reproduction, which could have severe repercussions on population dynamics.</p></div

Life-history traits in <i>G</i>. <i>fossarum</i> exposed to 50 μg L^-1 fenoxycarb.

<p>Mean±standard deviation. In parentheses, number of individuals or pooled sample analyzed.</p

Competition Between Steric Hindrance and Hydrogen Bonding in the Formation of Supramolecular Bottle Brush Polymers

The formation of supramolecular bottle-brush polymers consisting of a noncovalent backbone assembled through directional hydrogen bonds and of poly­(isobutylene) (PIB) side-chains was investigated in cyclohexane by light scattering. Two limiting cases were observed depending on the balance between the favorable formation of hydrogen bonds and the unfavorable stretching of the PIB chains within the supramolecular bottle-brushes, in agreement with a theoretical model developed by Wang et al. On one hand, a bisurea self-assembling unit able to form four cooperative hydrogen bonds per molecule led to relatively short supramolecular bottle-brushes, the length of which could be varied by modifying steric hindrance or by using solvent mixtures. On the other hand, supramolecular bottle-brush polymers exhibiting persistent lengths of more than 300 nm could be obtained by using trisureas that are able to form six hydrogen bonds per molecule. Their easy synthesis and the fact that it is possible to control their self-assembly into long supramolecular bottle-brush polymers make polymer-decorated bisureas and trisureas an attractive alternative to cyclopeptides and shape-persistent rings for the creation of supramolecular nanostructures

PCA scores of the lipid profiles plotted on the two first components of the PCA.

<p>Females in the control (green) and fenoxycarb-exposed group (pink) and newborns in the control (blue) and fenoxycarb-exposed group (orange).</p