Tetra-arylborate lipophilic anions as targeting groups.

Tetraphenylborate (TPB) anions traverse membranes but are excluded from mitochondria by the membrane potential (Δψ). TPB-conjugates also distributed across membranes in response to Δψ, but surprisingly, they rapidly entered cells. They accumulated within lysosomes following endocystosis. This pH-independent targeting of lysosomes makes possible new classes of probe and bioactive molecules.