1064-nm-resonant gold nanorods for photoacoustic theranostics within permissible exposure limits.

Therapeutic and diagnostic methods based on photomechanical effects are attracting much current attention in contexts as oncology, cardiology and vascular surgery, for such applications as photoacoustic imaging or microsurgery. Their underlying mechanism is the generation of ultrasound or cavitation from the interaction of short optical pulses with endogenous dyes or targeted contrast agents. Among the latter, gold nanorods are outstanding candidates, but their use has mainly been reported for photoacoustic imaging and photothermal treatments. Conversely, much less is still known about their value as a precision tool for photomechanical manipulations, such as to impart local damage with high spatial resolution through the expansion and collapse of microbubbles. Here, we address the feasibility of gold nanorods exhibiting a distribution of surface plasmon resonances between about 900 to above 1100 nm as a contrast agent for photoacoustic theranostics. After testing their cytotoxicity and cellular uptake, we discuss their photostability and use to mediate cavitation and the photomechanical destruction of targeted cells. We find that the choice of a plasmonic band peaking around 1064 nm is key to enhance the translational potential of this approach. With respect to the standard alternative of 800 nm, at 1064 nm, relevant regulations on optical exposure are less restrictive and the photonic technology is more mature.

Targeted 307 nm UVB-phototherapy in psoriasis. A pilot study comparing a 307 nm excimer light with topical dithranol.

BACKGROUND: Phototherapy is a cornerstone in treatment of moderate-to-severe psoriasis. Narrow-band UVB has been shown to be a potent therapeutic tool. To reduce the potential carcinogenic risk, targeted phototherapy has been developed using excimer lasers or excimer light devices (ELD). OBJECTIVE: The role of excimer light therapy in practice and modes of action are not completely understood. We wanted to investigate a 307 nm ELD for plaque psoriasis in comparison with topical dithranol therapy twice daily. METHODS: We conducted a pilot trial in 21 adult patients with moderate plaque-type psoriasis. Two target lesions of comparable size and plaque-modified Psoriasis Activity and Severity Index (PSI) scores were selected. Lesion A was treated three times using a newly developed 307 nm ELD. Lesion B was treated twice daily with dithranol ointment. The mean period of treatment was 9 days. Clinical evaluation included PSI scores, safety, time needed to treat, and patient's satisfaction. In addition, fluorescence-remission imaging technique was used for objective evaluation. RESULTS: Both treatments improved the PSI score (mean 3.0 points). The treatments were safe but ELD was more convenient for patients. The time needed to treat the target lesion was significantly shorter with ELD. Targeted UVB therapy normalized NADH fluorescence in lesional skin. CONCLUSIONS: The 307 nm excimer light therapy for plaque type psoriasis was equipotent to twice daily topical dithranol. Efficacy, safety, and convenience suggest that targeted UVB therapy with quasi monochromatic light is a new useful treatment option for patients with limited psoriatic plaques.