Systemically injected drug delivery systems distribute into various organs and tissues, including liver, spleen and kidneys. Recent reports pointed out a significant accumulation of systemically injected nanoparticles in the skin. Skin constitutes the largest organ in the body with important immune functions, and accumulation of drug delivery systems could have significant implications for skin toxicity in living subjects. Fiber optic-based near- infrared spectroscopy (FONIRS) setup was developed and tested for measuring of NIR spectra in the skin (670 nm and 760 nm). Ex vivo spectral measurements of NIR fluorescence through the skin showed linear response down to 34 femtomole of NIR dyes<i>. </i>Following systemic injection of NIR labeled drug carriers, FONIRS detected an immediate and stable accumulation of fluorescence in the skin. FONIRS measurements enabled comparison of skin accumulation between different drug delivery systems and correlated with intravital measurements and ex vivo quantification. Interestingly, skin monitoring of DiR labeled, long-circulating PEGylated liposomes showed much higher accumulation than DiR-labeled short-circulating non-PEGylated liposomes. The skin deposition can be monitored for days after the liposomes cleared from blood. Measurements with FONIRS also enabled to estimate skin concentration of liposomes (percent of injected dose per gram). This simple and practical approach can be used to monitor accumulation of drug delivery systems in preclinical and clinical studies. <br/>

Fiber optical near infrared spectrometry (FONIRS) for non-invasive monitoring of skin accumulation of systemically injected drug carriers

256th National Meeting (2018)

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