Reactive oxygen and nitrogen species are small reactive
molecules
derived from elements in the airoxygen and nitrogen. They
are produced in biological systems to mediate fundamental aspects
of cellular signaling but must be very tightly balanced to prevent
indiscriminate damage to biological molecules. Small molecule probes
can transmute the specific nature of each reactive oxygen and nitrogen
species into an observable luminescent signal (or even an acoustic
wave) to offer sensitive and selective imaging in living cells and
whole animals. This review focuses specifically on small molecule
probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide,
and peroxynitrite that provide a luminescent or photoacoustic signal.
Important background information on general photophysical phenomena,
common probe designs, mechanisms, and imaging modalities will be provided,
and then, probes for each analyte will be thoroughly evaluated. A
discussion of the successes of the field will be presented, followed
by recommendations for improvement and a future outlook of emerging
trends. Our objectives are to provide an informative, useful, and
thorough field guide to small molecule probes for reactive oxygen
and nitrogen species as well as important context to compare the ecosystem
of chemistries and molecular scaffolds that has manifested within
the field.