Patterns of surface immobilized block copolymer vesicle nanoreactors

Surfaces with Dual Functionality through Specific Coimmobilization of Self-Assembled Polymeric Nanostructures

Coimmobilization of functional, nanosized assemblies broadens the possibility to engineer dually functionalized active surfaces with a nanostructured texture. Surfaces decorated with different nanoassemblies, such as micelles, polymersomes, or nanoparticles are in high demand for various applications ranging from catalysis, biosensing up to antimicrobial surfaces. Here, we present a combination of bio-orthogonal and catalyst-free strain-promoted azide-alkyne click (SPAAC) and thiol-ene reactions to simultaneously coimmobilize various nanoassemblies; we selected polymersome-polymersome and polymersome-micelle assemblies. For the first time, the immobilization method using SPAAC reaction was studied in detail to attach soft, polymeric assemblies on a solid support. Together, the SPAAC and thiol-ene reactions successfully coimmobilized two unique self-assembled structures on the surfaces. Additionally, poly(dimethylsiloxane) (PDMS)-based polymersomes were used as "ink" for direct immobilization from a PDMS-based microstamp onto a surface creating locally defined patterns. Combining immobilization reactions has the advantage to attach any kind of nanoassembly pairs, resulting in surfaces with "desired" interfacial properties. Different nanoassemblies that encapsulate multiple active compounds coimmobilized on a surface will pave the way for the development of multifunctional surfaces with controlled properties and efficiency.

Interaction of cells with patterned reactors

The patterning of subcompartmentalized enzyme-loaded reactors is illustrated and the effect of triggered encapsulated catalysis on adhering cells is reported.

Surface-assisted laser desorption ionization mass spectrometry techniques for application in forensics

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) is an excellent analytical technique for the rapid and sensitive analysis of macromolecules (>700 Da), such as peptides, proteins, nucleic acids, and synthetic polymers. However, the detection of smaller organic molecules with masses below 700 Da using MALDI-MS is challenging due to the appearance of matrix adducts and matrix fragment peaks in the same spectral range. Recently, nanostructured substrates have been developed that facilitate matrix-free laser desorption ionization (LDI), contributing to an emerging analytical paradigm referred to as surface-assisted laser desorption ionization (SALDI) MS. Since SALDI enables the detection of small organic molecules, it is rapidly growing in popularity, including in the field of forensics. At the same time, SALDI also holds significant potential as a high throughput analytical tool in roadside, work place and athlete drug testing. In this review, we discuss recent advances in SALDI techniques such as desorption ionization on porous silicon (DIOS), nano-initiator mass spectrometry (NIMS) and nano assisted laser desorption ionization (NALDI™) and compare their strengths and weaknesses with particular focus on forensic applications. These include the detection of illicit drug molecules and their metabolites in biological matrices and small molecule detection from forensic samples including banknotes and fingerprints. Finally, the review highlights recent advances in mass spectrometry imaging (MSI) using SALDI techniques.

Adsorption of Spherical Polyelectrolyte Brushes: from Interactions to Surface Patterning

Adsorption of colloidal particles constitutes an attractive route to tailor the properties of surfaces. However, for efficient material design full control over the particle-substrate interactions is required. We investigate the interaction of spherical polyelectrolyte brushes (SPB) with charged substrates based on adsorption studies and atomic force spectroscopy. The brush layer grafted from the colloidal particles allows a precise adjustment of their adsorption behavior by varying the concentration of added salt. We find a pronounced selectivity between oppositely and like-charged surfaces for ionic strengths up to 10 mM. Near the transition from the osmotic to the salted brush regime at approximately 100 mM attractive secondary interactions become dominant. In this regime SPB adsorb even to like-charged surfaces. To determine the adhesion energy of SPB on charged surfaces directly, we synthesize micrometer-sized SPB. These particles are used in colloidal probe AFM studies. Measurements on oppositely charged surfaces show high forces of adhesion for low ionic strengths that can be attributed to an entropy gain by counterion release. Transferring our observations to charge patterned substrates, we are able to direct the deposition of SPB into two-dimensional arrays. Considering that numerous chemical modifications have been reported for SPB, our studies could open exiting avenues for the production of functional materials with a hierarchical internal organization.

pH dependent elasticity of polystyrene-block-poly(acrylic acid) vesicle shell membranes by atomic force microscopy

We assess the elastic properties of PS-b-PAA vesicle membranes under different pH values by AFM force measurements. We find that based on the shell deformation theory, the values of the estimated apparent Young's modulus of the vesicle membranes decrease as the pH of the solution increases. The onset of the decrease of E coincides with the surface pK(a) determined from ζ-potential measurements. This decrease of E at higher pH is attributed to electrostatic repulsion between the deprotonated PAA chains resulting in the thinning of the vesicle membrane.