Self-Reporting Materials: Protein- Mediated Visual Indication of Damage in a Bulk Polymer

Abstract

Damage self-reporting materials are able to indicate the presence of microscopic damaged regions by easy to detect signals, such as fluorescence. Therefore, these smart materials can reduce the risk of catastrophic failure of load-bearing components, e.g. in aerospace and construction applications. We highlight here our proof-of-concept paper and we present some additional data, which shows that proteins can be used as mechanophores in solid polymeric materials. Macroscopic mechanical forces were transferred from the polymer to the embedded proteins. The biomolecules act as molecular strain sensor, giving the material the desired selfreporting property. Poly(ethylene glycol) and poly(acrylamide) (PAAm) networks were doped with small amounts of thermsosome (THS), a protein cage from the family of chaperonins, that encapsulated a pair of fluorescent proteins. THS acts as a scaffold which brings the two fluorescent proteins into distance suitable for fluorescence resonance energy transfer (FRET). Moreover, THS can be distorted by mechanic forces so that the distance between the fluorescent proteins changes, leading to a change in FRET efficiency. Using the brittle PAAm as a model system, we were able to visualize microcracks in the polymers by FRET microscopy and by fluorescence lifetime imaging. THS also stabilizes the encapsulated guest proteins against thermal denaturation, increasing their half-live at 70°C by a factor of 2.3.

Mechanically Modulating the Photophysical Properties of Fluorescent Protein Biocomposites for Ratio‐ and Intensiometric Sensors

“…Furthermore, surprisingly few efforts have been directed toward developing stress‐sensing materials that employ fluorescent proteins. For example, Clark and co‐workers utilized Förster resonance energy transfer (FRET) between YFP and cyan fluorescent protein (CFP) to develop stress‐reporting poly(acrylamide) composites 33. 34 Stretching these materials under uniaxial strain resulted in increased FRET interactions between YFP and CFP near microscopic cracks that formed within the material, as determined by fluorescence confocal microscopy and fluorescence lifetime imaging (FLIM) 34.…”

“…For example, Clark and co-workers utilized Fçrster resonance energy transfer (FRET) between YFP and cyan fluorescent protein (CFP) to develop stress-reporting poly(acrylamide) composites. [33,34] Stretching these materials under uniaxial strain resulted in increased FRET interactions between YFP and CFP near microscopic cracks that formed within the material, as determined by fluorescence confocal microscopy and fluorescence lifetime imaging (FLIM). [34] Bruns and coworkers more recently reported that eYFP could serve as a mechanically sensitive link between glass substrates and epoxy resins, where delamination of the resin resulted in denaturation of the protein and subsequent fluorescence quenching.…”

From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

“…Further expanding the use of fluorescent proteins in polymer materials, Bruns and co‐workers combined two fluorescent proteins that display a FRET process to elicit a mechanochromic response. [ 161 ] Thus, a protein‐based mechanoresponsive motif was designed by covalently attaching an enhanced cyan fluorescent protein (eCFP) and an eYFP protein to the two cavities of a thermosome (THS), a chaperonin protein that assists folding amino acid sequences and serves to stabilize defined secondary structures. The THS protein holds the fluorescent eCFP and eYFP in close proximity to each other so that FRET can occur.…”

Self‐Reporting Fiber‐Reinforced Composites That Mimic the Ability of Biological Materials to Sense and Report Damage

“…Other dyes, which include bis(benzoxazolyl) stilbene and perylene derivatives, can be dispersed into polymeric materials during melt compounding or in solution. Further mechanochromic substances that have been used in polymeric materials are shear‐responsive photoluminescent ZnO tetrapods, CdSe–CdS tetrapod quantum dots, or force‐responsive proteins . The reader is referred to various reviews for a detailed overview of this field …”