DNA Functionalized Spider Silk Nanohydrogels for Specific Cell Attachment and Patterning

Abstract

Nucleated protein self-assembly of an azido modified spider silk protein was employed in the preparation of nanofibrillar networks with hydrogel-like properties immobilized on coatings of the same protein. Formation of the networks in a mild aqueous environment resulted in thicknesses between 2 and 60 nm, which were controlled only by the protein concentration. Incorporated azido groups in the protein were used to “click” short nucleic acid sequences onto the nanofibrils, which were accessible to specific hybridization-based modifications, as proved by fluorescently labeled DNA complements. A lipid modifier was used for efficient incorporation of DNA into the membrane of nonadherent Jurkat cells. Based on the complementarity of the nucleic acids, highly specific DNA-assisted immobilization of the cells on the nanohydrogels with tunable cell densities was possible. Addressability of the DNA cell-to-surface anchor was demonstrated with a competitive oligonucleotide probe, resulting in a rapid release of 75–95% of cells. In addition, we developed a photolithography-based patterning of arbitrarily shaped microwells, which served to spatially define the formation of the nanohydrogels. After detaching the photoresist and PEG-blocking of the surface, DNA-assisted immobilization of the Jurkat cells on the nanohydrogel microstructures was achieved with high fidelity.

Dual Patterning of Self‐Assembling Spider Silk Protein Nanofibrillar Networks

“…Considering the broad variability of available spider silk protein genetical variants [38,[47][48][49] and chemical [32,35] modifications, such a system will offer many alternatives for screening and comparing different surface modifications under the same conditions at a microscale resolution and with variable spacing in-between the different material and shapes based on the protein microstructures. Such variable setup could be used in the future, for instance, in studies of material-cell interactions [44,45] at the concomitant influence of microstructure shapes and/ or co-culturing of different cell lines specifically attracted by employed adhesion tags on the eADF4(C16) scaffolds to study the influence of biological signals on cell behavior. In further developments of the presented system, spatially selective implementation of enzymatic functionalities into the pattern would be possible in post-lithography processing using addressable hybridization between the DNA-modified micropattern and complementary DNA-modified protein chimeras, protein binding DNA-aptamers, [32,50] or protein binding tags.…”

“…[39,40] If combined with the ability to microstructure the scaffolds into arbitrary shapes at microscale sizes, the applications thereof would be expandable into microtechnological fields with potential uses for instance in protein microarrays, [41] microstructured enzymatic arrays, [42] microfluidic chips used for substance analysis, [43] and microscale cell-cell or cell-material interaction assaying platforms. [44,45] Herein, the self-assembling spider silk nanofibrils were explored in a combination with positive tone photolitho graphy to produce functionalized microscale pattern of arbitrary shapes. The assembled nanofibrillar networks withstood even repetitive processing of the photoresist, thus enabling spatiotemporal patterning of the specifically codified protein microareas on one substrate with high position fidelity (Figure 1).…”

“…[ 39,40 ] If combined with the ability to microstructure the scaffolds into arbitrary shapes at microscale sizes, the applications thereof would be expandable into microtechnological fields with potential uses for instance in protein microarrays, [ 41 ] microstructured enzymatic arrays, [ 42 ] microfluidic chips used for substance analysis, [ 43 ] and microscale cell–cell or cell–material interaction assaying platforms. [ 44,45 ]…”

Aptamer‐Modified Nanohydrogel Microarrays for Bioselective Cancer Cell Immobilization

“…[22] The nanohydrogels showed inherently non-adhesive surface properties for cell and protein binding, whilst at the same time enabling incorporation of diverse DNA functionalities and related addressable immobilization of enzymes or DNA-modified cells. [22,23] Moreover, the chemical resilience of the fibrous networks enabled photolithography procedures and the production of nanohydrogel micropattern. [23] Herein we used the photolithographic approach to create arbitrarily shaped microwells to spatially define the self-assembly of azido-modified recombinant spider silk protein N 3 -eADF4(C16) into microstructured networks on surfaces.…”

“…[22,23] Moreover, the chemical resilience of the fibrous networks enabled photolithography procedures and the production of nanohydrogel micropattern. [23] Herein we used the photolithographic approach to create arbitrarily shaped microwells to spatially define the self-assembly of azido-modified recombinant spider silk protein N 3 -eADF4(C16) into microstructured networks on surfaces. Modification of the protein pattern via copper-free strain-promoted cycloaddition enabled incorporation of DNA-aptamers to bind typical cancer markers PTK7 or nucleolin expressed on human nonadherend leukemia T cells (Jurkat), as well as adherent cervix carcinoma (HeLa) and neuroblastoma (Kelly) cell lines.…”