Tanja K. Claus

Spatially controlled photochemical peptide and polymer conjugation on biosurfaces

An efficient phototriggered Diels-Alder conjugation is utilized to graft in an effective and straightforward approach poly(trifluoro ethyl methacrylate) (Mn = 3700 Da, Đ = 1.27) and a model peptide (GIGKFLHS) onto thin hyaluronan films and cellulose surfaces. The surfaces were functionalized with an o-quinodimethane moiety - capable of releasing a caged diene - via carbodiimide mediated coupling. The o-quinodimethane group is employed as a photoactive linker to tether predefined peptide/polymer strands in a spatially controlled manner onto the biosurface by photoenol ligation. An in-depth characterization employing XPS, ToF-SIMS, SPR, ellipsometry, and AFM was conducted to evidence the effectiveness of the presented approach.

Guiding Cell Attachment in 3D Microscaffolds Selectively Functionalized with Two Distinct Adhesion Proteins.

The combination of three different photoresists into a single direct laser written 3D microscaffold permits functionalization with two bioactive full-length proteins. The cell-instructive microscaffolds consist of a passivating framework equipped with light activatable constituents featuring distinct protein-binding properties. This allows directed cell attachment of epithelial or fibroblast cells in 3D.

Ambient temperature ligation of diene functional polymer and peptide strands onto cellulose via photochemical and thermal protocols.

In the present contribution, two novel ambient temperature avenues are introduced to functionalize solid cellulose substrates in a modular fashion with synthetic polymer strands (poly(trifluoro ethyl methacrylate), PTFEMA, Mn = 4400 g mol(-1) , Đ = 1.18) and an Arg-Gly-Asp (RGD) containing peptide sequence. Both protocols rely on a hetero Diels-Alder reaction between an activated thiocarbonyl functionality and a diene species. In the first-thermally activated-protocol, the cellulose features surface-expressed thiocarbonylthio compounds, which readily react with diene terminal macromolecules at ambient temperature. In the second protocol, the reactive ene species are photochemically generated based on a phenacyl sulfide-decorated cellulose surface, which upon irradiation expresses highly reactive thioaldehyde species. The generated functional hybrid surfaces are characterized in-depth via ToF-SIMS and XPS analysis, revealing the successful covalent attachment of the grafted materials, including the spatially resolved patterning of both synthetic polymers and peptide strands using the photochemical protocol. The study thus provides a versatile platform technology for solid cellulose substrate modification via efficient thermal and photochemical ligation strategies.

Stepwise Light‐Induced Dual Compaction of Single‐Chain Nanoparticles

A photochemical strategy for the sequential dual compaction of single polymer chains is introduced. Two photoreactive methacrylates, with side chains bearing either a phenacyl sulfide (PS) or an α-methylbenzaldehyde (photoenol, PE) moiety, are selectively incorporated by one-pot iterative reversible-addition fragmentation chain transfer copolymerization into the outer blocks of a well-defined poly(methyl methacrylate) based ABC triblock copolymer possessing a nonfunctional spacer block (Mn = 23 400 g mol-1 , Đ = 1.2; ≈15 units of each photoreactive moieties of each type) as well as in model statistical copolymers bearing only one type of photoreactive unit. Upon UVA irradiation, PS and PE lead to highly reactive thioaldehydes and o-quinodimethanes, which rapidly react with dithiol and diacrylate linkers, respectively. The monomerfunctional copolymers are employed to establish the conditions for controlled intramolecular photo-crosslinking, which are subsequently applied to the bifunctional triblock copolymer. All compaction/folding experiments are monitored by size-exclusion chromatography and dynamic light scattering. The dual compaction consists of two events of dissimilar amplitude: the first folding step reveals a large reduction in hydrodynamic diameters, while the second compaction lead to a far less pronounced reduction of the single-chain nanoparticles size, consistent with the reduced degrees of freedom available after the first covalent compaction step.