Ionic Liquid-Coated NIR-II Polymer Conjugates as Targeted Brain Theranostics

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PROJECT SUMMARY/ABSTRACT There are currently limited treatments available to treat non-operable brain cancers, and none that meaningfully extend the lifespan of patients. Imaging these diffuse tumors is also a challenge, and current fluorescent probes emit in wavelengths with high biological background fluorescence. This proposal describes the development of novel dye molecules that emit in the near-infrared II (NIR-II)/shortwave infrared (SWIR) region (1000 – 2000 nm). Within the NIR-II/SWIR region, higher resolution images are found at longer wavelengths. No small molecule emitters have peak emission beyond 1400 nm and only one known molecule has peak emission >1250 nm. We have preliminarily synthesized two fluorescent materials with emission maxima conservatively projected at ~1700 nm and >1900 nm. These dyes offer the ability to see further into the SWIR region than any other reported organic small molecules where image resolution is the highest. Additionally, we proposed to synthesize materials with shorter wavelength emission than these materials >2000 nm where imaging depth and contrast both are suggested to continually improve based on the current literature. In order to effectively deliver the dye molecules into the brain, we have to encapsulate them into nanocarriers. Linear-dendritic block-copolymers (LDBCs) represent a highly functionalizable material for drug delivery vehicles. Its dual linear/dendritic nature makes it excellent at encapsulating a variety of molecules. We use biocompatible ionic liquids (ILs), molten salts comprised of asymmetric cations and anions, to `tune' the affinity of nanoparticles to different cell types. Using this strategy, we have developed an IL that promotes nanoparticle `hitchhiking' on erythrocytes to deliver them to the brain, and achieves cell-selective targeting of microglia once delivered to the central compartment. Preliminary data in rats demonstrate ~48% of injected nanoparticles accumulating in the brain within 6 hours, a vast improvement over current nanoparticle delivery strategies. To this end, we will (Aim 1) generate a library of novel NIR-II candidates, in addition to our current leads, that show peak emission at 1700 – 2000 nm, package them into LDBCs, and coat the nanoparticles with ILs. We will measure their photophysical properties and confirm the preference that ILs confer to murine and human blood components as potential cargo carriers. (Aim 2) We will assess the safety (subacute, acute, subchronic, reproductive, mutagenic) and biodistribution of up to 5 leading formulations in rats, and capture high-resolution live brain imaging. (Aim 3) Lead candidates (based on CNS distribution and photophysical properties) will be assessed in vitro and in vivo in a xenografted glioblastoma rat model.