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Introduction Metastatic colorectal cancer (CRC) is complicated by chemotherapy-resistant cell populations. Oxaliplatin is used in heated intraperitoneal hyperthermic chemoperfusion (HIPEC) for treatment of disseminated CRC. Photothermal nanoparticles can provide focal heating to improve the response of CRC cells to oxaliplatin, by confining heating near individual cells. Reduction in cellular luciferase signal may allow single-cell-resolution recording of thermal dosimetry. Methods Oxaliplatin resistant (OxR) variants of luciferase-expressing CT26.WT-Fluc-Neo CRC cells were developed and their sensitivity to hyperthermia was evaluated. Polymer-based photothermal nanoparticles were developed, characterized and used to explore their potential for imparting a thermal dose to improve cell response to oxaliplatin. A correlation of thermal dose to intracellular luciferase activity was established using quantitative luminescence monitoring and microscopy. Results Luciferase-based monitoring of thermal dose within CT26 cell lines was validated within the ranges of 0.04–8.33 CEM43 for parental cells and 0.05–9.74 CEM43 for OxR CT26 cells. This was further confirmed using nanoparticle-induced hyperthermia, where the single-cell resolution of the thermal dose can be achieved. The nanoparticles enhance cell killing of resistant cells when combined with oxaliplatin and stimulated to generate heat. Conclusion Nanoparticle-based hyperthermia is effective for augmenting chemotherapy and can be coupled with reductions in CT26 luciferase expression to monitor thermal dose at single-cell resolution. The development of OxR CT26.WT-Fluc-Neo CRC cells sets the stage for pre-clinical evaluations to measure nanoparticle-induced hyperthermia to augment chemotherapy (Nano-HIPEC) in a chemotherapy-resistant model of disseminated CRC.

Abstract Colorectal cancer (CRC) treatment is currently hindered by micrometastatic relapse that cannot be removed completely during surgery and is often chemotherapy resistant. Targeted theranostic nanoparticles (NPs) that can produce heat for ablation and enable tumor visualization via their fluorescence offer advantages for detection and treatment of disseminated small nodules. A major hurdle in clinical translation of nanoparticles is their interaction with the 3D tumor microenvironment. To address this problem tumor organoid technology was used to evaluate the ablative potential of CD44-targeted polymer nanoparticles using hyaluronic acid (HA) as the targeting agent and coating it onto hybrid donor acceptor polymer particles (HDAPPs) to form HA-HDAPPs. Additionally, nanoparticles composed from only the photothermal polymer, 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), were also coated with HA, to form HA-BSe NPs, and evaluated in 3D. Monitoring of nanoparticle transport in 3D organoids revealed uniform diffusion of non-targeted HDAPPs in comparison to attenuated diffusion of HA-HDAPPs due to nanoparticle-matrix interactions. Computational diffusion profiles suggested that HA-HDAPPs transport may not be accounted for by diffusion alone, which is indicative of nanoparticle/cell matrix interactions. Photothermal activation revealed that only HA-BSe NPs were able to significantly reduce tumor cell viability in the organoids. Despite limited transport of the CD44-targeted theranostic nanoparticles, their targeted retention provides increased heat for enhanced photothermal ablation in 3D, which is beneficial for assessing nanoparticle therapies prior to in vivo testing.