The role of lasers in biomedicine goes under the spotlight this week as we explore the workings of photodynamic cancer therapy, find out how laser tweezers can be used to force-feed bugs to white blood cells and hear how a new technique uses laser-powered DNA nanoswitches to spot specific genes. Also, why the proton just got smaller, prompting a reevaluation of some trusted laws of physics, how antidepressants in seawater can make shrimps swim towards danger and a novel mechanism for natural selection - beneficial bacteria! Plus, in Kitchen Science, what the patterns produced by laser light... Like this podcast? Please help us by supporting the Naked Scientists