Potassium Acyltrifluoroborate (KAT) Ligations are Orthogonal to Thiol-Michael and SPAAC Reactions: Covalent Dual Immobilization of Proteins onto Synthetic PEG Hydrogels

TLDR: The potassium acyltrifluoroborate amide-forming ligation is orthogonal to both thiol-Michael and strain promoted azide alkyne cycloadditions and enables stepwise covalent protein immobilization of multiple BSA-derivatives onto the hydrogel scaffold regardless of the order of addition.

Abstract: The covalent immobilization of peptides, proteins, and other biomolecules to hydrogels provides a biologically mimicking environment for cell and tissue growth. Bioorthogonal chemical reactions can serve as a tool for this, but the paucity of such reactions and mutual incompatibilities limits the number of distinct molecules that can be introduced. We now report that the potassium acyltrifluoroborate (KAT) amide-forming ligation is orthogonal to both thiol-Michael and strain promoted azide alkyne cycloadditions (SPAAC) and the requisite functional groups – KATs and hydroxylamines – are stable and compatible to hydrogel formation, protein modification, and post-assembly immobilization of biomolecules onto hydrogels. In combination these ligations enables stepwise covalent protein immobilization of multiple BSA-derivatives onto the hydrogel scaffold regardless of the order of addition.