The invention relates to microbubble contrast agent compositions comprising a gas core encapsulated by a monolayer shell, said shell comprising a first surfactant, a second surfactant having a higher water solubility than said first surfactant, an anchor molecule attached to said shell at the gas-shell interface and an optically-active probe, said probe being detectable by fluorescence, near-infrared, bioluminescence, or other optical imaging methods. Uses of the described compositions for imaging and therapeutic applications are contemplated.
