The study develops dual-stage photocages (SNAPcages) that can be activated by tissue penetrating near-infrared (NIR) light to release the payload only in the presence of specific biomolecules, offering unprecedented control and precision over the uncaging process.

An additional layer of control over photouncaging is incorporated by integrating photocages with site-specific targeting via SNAP-tag proteins in living cells. In strong contrast to conventional photocages that rely solely on light as a stimulus - limiting spatial resolution to the diffraction limit - SNAPcages are activated by NIR light only in the presence of specific biomolecular targets. This novel approach enhances spatial precision beyond the current state-of-the-art, enabling targeted uncaging at the subcellular to single-molecule level. The concept is based on a recently introduced fluorogenic system, the utility of which has been shown on a series of polymethine dyes.^[1]

The SNAPcages are designed around a Cy7 photocage scaffold containing a drug-like payload attached in the C4′ position of the central chain. Contrary to all the previous photocages pursued in our group,^[2–4] the design herein relies on desymmetrized cyanines that contain two different terminal heterocycles.

In their native state, the SNAPcages are photochemically inactive because of the intramolecular cyclization of the sidechain (red) which disrupts the conjugation of the cyanine chromophore. Upon specific binding of SNAP-ligand (green) to its target (brown), the polarity of the immediate environment surrounding the SNAPcage will change, triggering the ring-opening on the heterocycle site and restoring the absorption of Cy7. This will arm the SNAPcage for a subsequent activation with light and uncaging of the payload (purple). This arming process induced by specific intracellular targets will provide an additional layer of spatiotemporal control of the uncaging, overcoming the resolution limits imposed by the diffraction limits of light.

[1] A. Martin, P. Rivera-Fuentes, Nat Chem, 2024, 16, 28–35.

[2] K. Hanc, H. Janeková, P. Štacko, JACS Au, 2024, 4, 2687–2694.

[3] M. Russo, D. Zielinska, K. Hanc, A. Ramundo, D. Meier, A. Szabo, P. Stacko, JACS Au, 2025, ASAP article.

[4] M. Russo, H. Janeková, D. Meier, M. Generali, P. Štacko, JACS, 2024, 146 (12), 8417-8424.