Overview of the optical properties of fluorescent nanoparticles for optical imaging

Nanoparticles (NPs) include a wide group of small structures composed by very different materials and characterized by peculiar properties that make them suitable for many applications, especially imaging and drug delivery. In this overview, we focus on the optical properties of fluorescent NPs available for in vivo, in vitro and ex vivo preclinical studies and detectable with the optical imaging technique alone or in combination with microscopic confocal imaging. We summarize here the basic principles of the optical detection of fluorescent NPs, elucidating which are the current issues to be resolved and possible solutions to achieve the highest sensitivity and specificity for an unbiased analysis. So far NPs application in clinic is in evaluation due to safety questions still unaddressed but in the future they could dramatically improve both preclinical research and patient clinical care.