TCO-PNB ester is widely utilized in bioorthogonal chemistry for labeling and imaging applications. It serves as a key component in click chemistry reactions, particularly with tetrazines, enabling rapid and selective conjugation in biological systems. This property makes it valuable for studying live cells, tracking biomolecules, and developing targeted drug delivery systems. Additionally, it is employed in the synthesis of bioconjugates for diagnostic and therapeutic purposes, enhancing precision in molecular imaging and cancer research. Its stability and reactivity under physiological conditions further support its use in advanced biomedical studies.