Quantum Defects as a Toolbox for the Covalent Functionalization of Carbon Nanotubes with Peptides and Proteins

Abstract

Single‐walled carbon nanotubes (SWCNTs) are a 1D nanomaterial that shows fluorescence in the near‐infrared (NIR, >800 nm). In the past, covalent chemistry was less explored to functionalize SWCNTs as it impairs NIR emission. However, certain sp3 defects (quantum defects) in the carbon lattice have emerged that preserve NIR fluorescence and even introduce a new, red‐shifted emission peak. Here, we report on quantum defects, introduced using light‐driven diazonium chemistry, that serve as anchor points for peptides and proteins. We show that maleimide anchors allow conjugation of cysteine‐containing proteins such as a GFP‐binding nanobody. In addition, an Fmoc‐protected phenylalanine defect serves as a starting point for conjugation of visible fluorophores to create multicolor SWCNTs and in situ peptide synthesis directly on the nanotube. Therefore, these quantum defects are a versatile platform to tailor both the nanotube's photophysical properties as well as their surface chemistry.

Remote near infrared identification of pathogens with multiplexed nanosensors

“…The modular chemical design of the SWCNT functionalization is useful to create more sensors and increase the multiplexing level and thus sensor performance. In this context, the advent of covalent functionalization of SWCNTs with biomolecules without impairment of NIR fluorescence will open up additional possibilities 77 . For point-of-care diagnostics the current time resolution should be further increased.…”

Advances in engineering near-infrared luminescent materials

“…reported enhanced QY up to 4% ( Berger et al., 2019 ). Recent research has also used quantum defects for modular anchors for both the attachment of nanobodies (such as peptides and proteins) and the synthesis of peptides directly on the SWNT surface, enabling further tuning of their photophysical properties ( Mann et al., 2020 ).…”

A post-functionalization toolbox for diazonium (electro)-grafted surfaces: review of the coupling methods

“…exploited quantum defects of the surface to successfully anchor peptides and proteins. 104 Two other fundamental studies, focused on the post functionalization efficiency using various approaches, were reported by Downard and coworkers. In the first one, NH 2 -tethered carbon surfaces were obtained by electrografting and deprotection of Boc-and Fmoc protected aminobenzyldiazonium salts.…”