TPAresponsive

TPAresponsive refers to materials engineered to change their physical or chemical state in response to two-photon irradiation. The term is used across photochemistry, materials science, and bioengineering to enable selective activation at depth within scattering media using near-infrared light.

The activation relies on two-photon absorption, typically by chromophores with large two-photon cross-sections. When two photons are absorbed in a confined focal volume, energy is released to drive a photochemical reaction, such as bond cleavage, photoisomerization, or cargo release.

Design considerations include choosing chromophores with high δ values, incorporating photolabile protecting groups or thermally latent linkages, and ensuring solubility and biocompatibility for biological uses. Performance is characterized by the two-photon absorption cross-section and the quantum yield of the triggered process.

Applications encompass fluorescence imaging and sensing with deep-tissue resolution, photopharmacology for spatially controlled drug activation, and smart materials or microfabrication systems that respond to two-photon stimuli.

History and challenges: Early demonstrations appeared in the 1990s and 2000s as two-photon biology matured. Current work aims to improve tissue compatibility, photostability, and reaction efficiency, while expanding library of activatable targets and reducing phototoxicity.

See also: two-photon absorption; photolabile protecting groups; photoswitchable compounds; photoresponsive materials.