Photothermal nanoparticles for ablation of bacteria associated with kidney stones

Abstract

Objective: To determine whether photothermal polymer nanoparticles (NPs) can interface with bacteria associated with kidney stones, generate heat when stimulated with near infrared (NIR) light, and aid in reducing bacterial burden. Methods: Two types of kidney stones, artificial, and those removed during percutaneous nephrolithotomy (PCNL), were inoculated with Escherichia coli (E. coli) and then incubated with NPs composed of FITC-labeled Poly[4,4-bis(2-ethylhexyl)-cyclopenta[2,1-b;3,4-b′]-dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe). Association of the PCPDTBSe NPs was evaluated using fluorescence microscopy. Infected stones were incubated with NPs and exposed to 800 nm light to generate temperature increases from 25.4 to 68.6 °C on the stones. Following photothermal treatment, the stones were homogenized and the bacteria was enumerated via colony counting assays to evaluate the bactericidal effect. The photothermal effect was also evaluated using scanning electron microscopy of the treated biofilms. Results: Both kidney stone types sequestered E. coli. Control stones and stones treated with laser only had growth of numerous bacterial colonies, while stones exposed to NPs and laser grew significantly less, or none (p = 0.02). Conclusions: The polymer NPs interface with E. coli on artificial and patient-derived kidney stones, and they can impart a bactericidal effect, when stimulated with NIR to generate heat. This technique may possibly be extended to treating infected kidney stones in patients.