Fluorescent Protein PEGylation for Stable Photon Manipulation in Deep-Red Light-Emitting Devices

PEGylation is a classic strategy to reduce denaturation and immunogenicity in therapeutic proteins, bioimaging, and drug delivery. However, this concept has not been applied to incorporate biogenic materials as functional components in optoelectronics. Herein, PEGylation is rationalized as an effective tool to stabilize fluorescent proteins in solid-state photon manipulation down-converters integrated into bio-hybrid light-emitting diodes. In short, the archetypal red-emitting protein mCherry is nonspecifically PEGylated with methoxypolyethylene glycols (mPEG) chains of different lengths (mPEG-350/-750/-2000). These derivatives hold the same photoluminescence figures-of-merit of mCherry, but an improved resistance against organic solvents, pH, temperature, and polymers (in solution/dry-coatings) upon increasing the mPEG length. Indeed, the best-performing mCherry-mPEG-2000 adduct leads to deep-red devices with threefold enhanced color stability (>300 h) under harsh operation conditions (150 mW cm⁻²) over the prior art. Different device architectures along with spectroscopic, thermocycling, and electrochemical impedance spectroscopy studies of the prepared coatings aid in rationalizing that PEGylation successfully reduces i) nonreversible thermal denaturation, ii) aggregation in solid-state, and iii) photo-induced oxidation and H⁺-transfer deactivation of the chromophore, since oxygen diffusivity and H⁺-reorganization across the protein skeleton are slowed down by strong H⁺-bonding/hydrophobic mCherry-mPEG interactions. Hence, this simple supramolecular modification is of utmost relevance for future advances in protein-based optoelectronics.