The present invention relates to nanoparticles. In particular, the present invention provides nanoparticles for clinical (e.g., targeted therapeutic), diagnostic (e.g., imaging), and research applications in the field of cardiology. For example, in some embodiments, the present invention provides a method of treating (e.g., ablating) cardiac tissue, comprising: a) contacting an animal with a nanoparticle comprising a matrix, a toxic (e.g., ablative) agent (e.g., sonosensitizer, chemotherapeutic agent (e.g., doxorubicin or cisplatin), or photosensitizer), and a cardiac targeting moiety; and b) administering an activator of the toxic agent (e.g., light, chemical (e.g., pharmaceutical agent) or ultrasound) to at least a portion of the cardiac tissue (e.g., heart) of the animal to activate the toxic agent.