TCO-PEG8-acid | CAS 2353410-03-2

TCO-PEG8-acid is a trans-cyclooctene (TCO) functionalized polyethylene glycol (PEG) carboxylic acid click chemistry reagent designed for strain-promoted inverse electron-demand Diels–Alder (SPIEDAC) conjugation. The PEG spacer and terminal acid functionality support aqueous solubility and convenient coupling to amine-, hydrazide-, or activated ester-bearing platforms, while the TCO handle enables rapid bioorthogonal ligation to tetrazine partners used across chemical biology and molecular imaging workflows. This reagent is commonly selected when researchers need a flexible, water-compatible TCO-bearing linker for building conjugates, probes, and materials that can be assembled under mild conditions.

1. Tetrazine Probe Conjugation

TCO-PEG8-acid is widely used to generate tetrazine-reactive probes for fluorescence, luminescence, and affinity-based detection formats. The PEG8 spacer helps maintain probe accessibility and reduces steric constraints around the cyclooctene moiety, which is particularly valuable when labeling antibodies, nanobodies, or engineered binding scaffolds with a defined TCO density. The terminal carboxylic acid enables straightforward incorporation into linker strategies for probe assembly, including coupling to scaffold surfaces or attachment to polymeric carriers before downstream tetrazine-triggered ligation. In practice, this reagent is favored in research settings where rapid, catalyst-free conjugation to tetrazine reagents is required to preserve biomolecule integrity and to streamline probe production.

2. Antibody And Protein Labeling

TCO-PEG8-acid supports site-aware or bulk labeling workflows for proteins and protein-based reagents that will later be joined to tetrazine-functional partners. The PEG spacer improves conjugate handling in aqueous buffers and can reduce nonspecific aggregation that sometimes accompanies small, hydrophobic click handles. Researchers commonly use the carboxylic acid functionality to integrate TCO into amide-forming or activated ester coupling schemes, enabling attachment to protein surfaces while keeping the TCO group available for subsequent SPIEDAC reactions. This application is especially relevant for building modular immunoconjugates and research-grade protein probes where orthogonal assembly steps are preferred for reproducibility and batch-to-batch consistency.

3. Surface And Material Functionalization

TCO-PEG8-acid is used to functionalize surfaces and biomaterials that require bioorthogonal reactivity for later attachment of tetrazine-tagged ligands. The PEG8 chain provides a hydrated, flexible interface that can improve the presentation of TCO groups on coatings, beads, and polymeric matrices, which is important for maintaining reactivity in complex media. The carboxylic acid handle allows incorporation into surface chemistries such as carbodiimide-mediated coupling to amine-bearing materials or attachment to pre-activated linkers used in material fabrication. Downstream, these TCO-functional materials can be rapidly decorated with tetrazine-conjugated dyes, affinity ligands, or imaging reporters to create customizable sensing and labeling platforms.

4. Molecular Imaging Reagent Building

TCO-PEG8-acid is commonly employed as a TCO-bearing building block for constructing molecular imaging reagents and imaging-compatible conjugates that are assembled using tetrazine chemistry. The PEG8 linker helps optimize the spatial arrangement between the imaging payload and the reactive TCO moiety, supporting efficient engagement with tetrazine partners during probe assembly. Its carboxylic acid functionality facilitates integration into linker systems used to attach imaging labels to targeting vectors, including modular conjugation strategies where the imaging component is introduced at a later stage. This makes TCO-PEG8-acid a practical choice for research laboratories developing imaging reagents that benefit from rapid, bioorthogonal coupling and from flexible linker architecture to tune probe behavior in aqueous conditions.