Sub-10\nμm Soft\nInterlayers Integrating Patterned\nMultivalent Biomolecular Binding Environments

Designing surfaces\nthat enable controlled presentation\nof multivalent\nligand clusters (e.g., for rapid screening of biomolecular binding\nconstants or design of artificial extracellular matrices) is a cross-cutting\nchallenge in materials and interfacial chemistry. Existing approaches\nfrequently rely on complex building blocks or scaffolds and are often\nspecific to individual substrate chemistries. Thus, an interlayer\nchemistry that enabled efficient nanometer-scale patterning on a transferrable\nlayer and subsequent integration with other classes of materials could\nsubstantially broaden the scope of surfaces available for sensors\nand wearable electronics. Recently, we have shown that it is possible\nto assemble nanometer-resolution chemical patterns on substrates including\ngraphite, use diacetylene polymerization to lock the molecular pattern\ntogether, and then covalently transfer the pattern to amorphous materials\n(e.g., polydimethylsiloxane, PDMS), which would not natively enable\nhigh degrees of control over ligand presentation. Here, we develop\na low-viscosity PDMS formulation that generates very thin films (<10\nμm) with dense cross-linking, enabling high-efficiency surface\nfunctionalization with polydiacetylene arrays displaying carbohydrates\nand other functional groups (up to 10-fold greater than other soft\nmaterials we have used previously) on very thin films that can be\nintegrated with other materials (e.g., glass and soft materials) to\nenable a highly controlled multivalent ligand display. We use swelling\nand other characterization methods to relate surface functionalization\nefficiency to the average distance between cross-links in the PDMS,\ndeveloping design principles that can be used to create even thinner\ntransfer layers. In the context of this work, we apply this approach\nusing precision glycopolymers presenting structured arrays of <i>N</i>-acetyl glucosamine ligands for lectin binding assays.\nMore broadly, this interlayer approach lays groundwork for designing\nsurface layers for the presentation of ligand clusters on soft materials\nfor applications including wearable electronics and artificial extracellular\nmatrix.