Urbaner Bildungskatalysator : eine neue Sinneslandschaft für Wien

Patrick Bayer, Christoph SchlapakUniversität Innsbruck, Masterarbeit, 2019(VLID)359340

Semipermeable poly(ethylene glycol) films: the relationship between permeability and molecular structure of polymer chains

We describe size-selective semipermeable poly(ethylene glycol) (PEG) films which avoid the nonspecific absorption of large proteins but permit the passage of small target molecules. The size threshold for permeation through the PEG films on indium-tin oxide surfaces was characterised using cyclovoltammetry and redox-active probes of 0.3 and 0.6 nm diameter. The permeation was dependent on the molecular weight of PEG and the different conformational preferences of the polymer chains. PEG 5000 D with a looped and dynamically changing structure provided a porous and easily permeable meshwork for the passage of small molecules. In contrast, parallel aligned and helical PEG 500 chains represented a denser molecular sieve which is only permeable for small molecules 0.3 nm in size. By describing the relationship between the molecular structure and an important physiochemical property of surface-tethered PEG films, our findings on controllable semipermeable interfaces may be exploited for electrical sensor surfaces.Austrian Science Foundation N00104-NA

Nanoscale DNA tetrahedra improve biomolecular recognition on patterned surfaces.

The bottom‐up approach of DNA nano‐biotechnology can create biomaterials with defined properties relevant for a wide range of applications. This report describes nanoscale DNA tetrahedra that are beneficial to the field of biosensing and the targeted immobilization of biochemical receptors on substrate surfaces. The DNA nanostructures act as immobilization agents that are able to present individual molecules at a defined nanoscale distance to the solvent thereby improving biomolecular recognition of analytes. The tetrahedral display devices are self‐assembled from four oligonucleotides. Three of the four tetrahedron vertices are equipped with disulfide groups to enable oriented binding to gold surfaces. The fourth vertex at the top of the bound tetrahedron presents the biomolecular receptor to the solvent. In assays testing the molecular accessibility via DNA hybridization and protein capturing, tetrahedron‐tethered receptors outperformed conventional immobilization approaches with regard to specificity and amount of captured polypeptide by a factor of up to seven. The bottom‐up strategy of creating DNA tetrahedrons is also compatible with the top‐down route of nanopatterning of inorganic substrates, as demonstrated by the specific coating of micro‐ to nanoscale gold squares amid surrounding blank or poly(ethylene glycol)‐passivated glass surfaces. DNA tetrahedra can create biofunctionalized surfaces of rationally designed properties that are of relevance in analytical chemistry, cell biology, and single‐molecule biophysics

Selective protein and DNA adsorption on PLL-PEG films modulated by ionic strength.

We describe a soft thin film which selectively adsorbs DNA but averts the non-specific binding of proteins. Indium tin oxide (ITO) substrates were surface-modified with a poly(L-lysine)-g-poly(ethylene glycol) (PLL-PEG) film which carries an outer protein-repelling PEG layer and an underlying positively charged PLL layer that attracts DNA. Binding of DNA could be tuned by a factor of over 90 by varying the salt concentration. The dependence of DNA binding on ionic strength was described with a physicochemical model which led to the conclusion of an unexpectedly high enrichment of salt inside the PEG layer. In addition, the model led to an expanded definition of the Debye-Huckel type effective screening length parameter z. Our new findings on a film with dual passivation/attraction properties can find applications in biopolymer-specific coatings useful in bioseparation and biosensing. In addition, the physicochemical characterisation provides new insight into the interactions between biopolymers and polymer-coated interfaces

Nanoscale DNA tetrahedra improve biomolecular recognition on patterned surfaces

The bottom‐up approach of DNA nano‐biotechnology can create biomaterials with defined properties relevant for a wide range of applications. This report describes nanoscale DNA tetrahedra that are beneficial to the field of biosensing and the targeted immobilization of biochemical receptors on substrate surfaces. The DNA nanostructures act as immobilization agents that are able to present individual molecules at a defined nanoscale distance to the solvent thereby improving biomolecular recognition of analytes. The tetrahedral display devices are self‐assembled from four oligonucleotides. Three of the four tetrahedron vertices are equipped with disulfide groups to enable oriented binding to gold surfaces. The fourth vertex at the top of the bound tetrahedron presents the biomolecular receptor to the solvent. In assays testing the molecular accessibility via DNA hybridization and protein capturing, tetrahedron‐tethered receptors outperformed conventional immobilization approaches with regard to specificity and amount of captured polypeptide by a factor of up to seven. The bottom‐up strategy of creating DNA tetrahedrons is also compatible with the top‐down route of nanopatterning of inorganic substrates, as demonstrated by the specific coating of micro‐ to nanoscale gold squares amid surrounding blank or poly(ethylene glycol)‐passivated glass surfaces. DNA tetrahedra can create biofunctionalized surfaces of rationally designed properties that are of relevance in analytical chemistry, cell biology, and single‐molecule biophysics