Dip-pen-based direct writing of conducting silver dots

Surface Modification by Combination of Dip-Pen Nanolithography and Soft Lithography for Reduction of Bacterial Adhesion

Dip-pen nanolithography (DPN) and soft lithography are techniques suitable to modify the surface of biomaterials. Modified surfaces might play a role in modulating cells and reducing bacterial adhesion and biofilm formation. The main objective of this study was threefold: first, to create patterns at microscale on model surfaces using DPN; second, to duplicate and transfer these patterns to a real biomaterial surface using a microstamping technique; and finally, to assess bacterial adhesion to these developed patterned surfaces using the cariogenic species Streptococcus mutans. DPN was used with a polymeric adhesive to create dot patterns on model surfaces. Elastomeric polydimethylsiloxane was used to duplicate the patterns and silica sol to transfer them to the medical grade stainless steel 316L surface by microstamping. Optical microscopy and atomic force microscopy (AFM) were used to characterize the patterns. S. mutans adhesion was assessed by colony-forming units (CFUs), MTT viability assay, and scanning electron microscopy (SEM). DPN allowed creating microarrays from 1 to 5 µm in diameter on model surfaces that were successfully transferred to the stainless steel 316L surface via microstamping. A significant reduction up to one order of magnitude in bacterial adhesion to micropatterned surfaces was observed. The presented experimental approach may be used to create patterns at microscale on a surface and transfer them to other surfaces of interest. A reduction in bacterial adhesion to patterned surfaces might have a major impact since adhesion is a key step in biofilm formation and development of biomaterial-related infections.

Crystal structure of bis-[tetra-kis-(tri-phenyl-phosphane-κP)silver(I)] (nitrilo-tri-acetato-κ(4) N,O,O',O'')(tri-phenyl-phosphane-κP)argentate(I) with an unknown amount of methanol as solvate

The structure of the title compound, [Ag(C18H15P)4]2[Ag(C6H6NO6)(C18H15P)], exhibits trigonal (P-3) symmetry, with a C 3 axis through all three complex ions, resulting in an asymmetric unit that contains one third of the atoms present in the formula unit. The formula unit thus contains two of the cations, one anion and disordered mol-ecules of methanol as the packing solvent. Attempts to refine the solvent model were unsuccessful, indicating uninter-pretable disorder. Thus, the SQUEEZE procedure in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18] was applied, accounting for 670 electrons per unit cell, representing approximately 18 mol-ecules of methanol in the formula unit. The stated crystal data for M r, μ etc do not take these into account.

Challenging material patterning: fine lithography on coarse substrates

Precise patterning of inorganic materials is important for many technological applications. Often lithography processes are required on challenging substrates with respect to topography, flexibility, and surface adhesion. Here we show the fabrication of artificial gunshot residues (GSR) on adhesive tape samples by means of dip-pen lithography as an example for fine lithography on coarse substrates. We deposited lead-, barium-, and antimony-containing inks on SEM adhesive tape by direct writing with a fine tip. Single as well as multiple element structures with dimensions in the range of 10-75 µm were fabricated.