Designing photolabile ruthenium polypyridyl crosslinkers for hydrogel formation and multiplexed, visible-light degradation

Abstract

Multiplexed visible-light photolysis: two ruthenium crosslinkers were used to generate a PEG based hydrogel that can be degraded selectively with orange and blue light.

Visible Light‐Responsive Dynamic Biomaterials: Going Deeper and Triggering More

“…In the first completely visible dual‐wavelength responsive system, Rapp et al used two ruthenium complexes as crosslinkers for a PEG‐based hydrogel, inducing hydrogel degradation selectively using orange (592 nm) and blue (450 nm) light. [ 57 ] Coordinating nitrile‐based ligands modified with an alkyne, they were able to form a hydrogel with azide‐modified four‐arm PEG and selectively degrade hydrogel sections. The kinetics of bond cleavage only permitted unidirectional degradation, with the red‐shifted Ru(biq) 2 L 2 having an efficiency of photocleavage at 520 M −1 cm −1 compared to blue‐shifted Ru(bpy) 2 L 2 's efficiency of 980 M −1 cm −1 .…”

“…In these complexes, biq is an electron‐withdrawing ligand that decreases the energy of the singlet metal‐to‐ligand charge transfer state responsible for the strong visible absorbance band. [ 57 ]…”

“…Adapted with permission under the terms of the CC BY‐NC 3.0 license. [ 57 ] Copyright 2019, the Authors. Published by The Royal Society of Chemistry.…”

Selective Modification for Red‐Shifted Excitability: A Small Change in Structure, a Huge Change in Photochemistry

“…Due to their advantage of spatiotemporal control without the use of additional chemical reagents, photolabile protecting groups (PPGs) or “caging groups” already created an extensive pool of applications in the fields of biochemistry, [1–3] organic synthesis [3, 4] and even inorganic materials for coated surfaces [5] or hydrogel formation [6] . Nonetheless, the development and synthesis of PPGs, which can be used by irradiation with visible light—optimally within the “phototherapeutic window” (650–950 nm) [7] and thus in living cells without tissue damage—remains one of the main tasks of modern photochemistry.…”

“…Due to their advantage of spatiotemporal control withoutt he use of additional chemical reagents, photolabile protecting groups (PPGs) or "caging groups" already created an extensive pool of applicationsi nt he fields of biochemistry, [1][2][3] organic synthesis [3,4] and even inorganic materials for coated surfaces [5] or hydrogel formation. [6] Nonetheless, the development and synthesis of PPGs, which can be used by irradiation with visible light-optimally within the "phototherapeutic window" (650-950 nm) [7] and thus in living cells without tissue damage-remains one of the main tasks of modern photochemistry.A lternatively, alsoP PGs which can be activated with visiblel ight within the "green gap" (low absorption of the light-harvesting complexes of plants) from 500-600nma re highly desired for new applications in plants. [8] There are several strategies for achieving the necessary bathochromic absorption shift: psystem extension of the chromophore( maintaining planarity) [9] as well as an attachment of donor (D) and acceptor (A) structures to create ap ush-pull character [10] that enhances electron delocalization and therefore decreases the energy requiredf or excitation,a re few of them.…”