Designing surfaces
that enable controlled presentation
of multivalent
ligand clusters (e.g., for rapid screening of biomolecular binding
constants or design of artificial extracellular matrices) is a cross-cutting
challenge in materials and interfacial chemistry. Existing approaches
frequently rely on complex building blocks or scaffolds and are often
specific to individual substrate chemistries. Thus, an interlayer
chemistry that enabled efficient nanometer-scale patterning on a transferrable
layer and subsequent integration with other classes of materials could
substantially broaden the scope of surfaces available for sensors
and wearable electronics. Recently, we have shown that it is possible
to assemble nanometer-resolution chemical patterns on substrates including
graphite, use diacetylene polymerization to lock the molecular pattern
together, and then covalently transfer the pattern to amorphous materials
(e.g., polydimethylsiloxane, PDMS), which would not natively enable
high degrees of control over ligand presentation. Here, we develop
a low-viscosity PDMS formulation that generates very thin films (<10
μm) with dense cross-linking, enabling high-efficiency surface
functionalization with polydiacetylene arrays displaying carbohydrates
and other functional groups (up to 10-fold greater than other soft
materials we have used previously) on very thin films that can be
integrated with other materials (e.g., glass and soft materials) to
enable a highly controlled multivalent ligand display. We use swelling
and other characterization methods to relate surface functionalization
efficiency to the average distance between cross-links in the PDMS,
developing design principles that can be used to create even thinner
transfer layers. In the context of this work, we apply this approach
using precision glycopolymers presenting structured arrays of N-acetyl glucosamine ligands for lectin binding assays.
More broadly, this interlayer approach lays groundwork for designing
surface layers for the presentation of ligand clusters on soft materials
for applications including wearable electronics and artificial extracellular
matrix.
