Multifunctional nanocarriers for controlled drug delivery, imaging of disease development and follow-up of treatment efficacy are promising novel tools for disease diagnosis and treatment. In the current investigation, we present a multifunctional theranostic nanocarrier system for anticancer drug delivery and molecular imaging. Superparamagnetic iron oxide nanoparticles (SPIONs) as an MRI contrast agent and busulphan as a model for lipophilic antineoplastic drugs were encapsulated into poly (ethylene glycol)-co-poly (caprolactone) (PEG-PCL) micelles via the emulsion-evaporation method, and PEG-PCL was labelled with VivoTag 680XL fluorochrome for in vivo fluorescence imaging. Busulphan entrapment efficiency was 83% while the drug release showed a sustained pattern over 10 h. SPION loaded-PEG-PCL micelles showed contrast enhancement in T 2 *-weighted MRI with high r 2* relaxivity. In vitro cellular uptake of PEG-PCL micelles labeled with fluorescein in J774A cells was found to be time-dependent. The maximum uptake was observed after 24 h of incubation. The biodistribution of PEG-PCL micelles functionalized with VivoTag 680XL was investigated in Balb/c mice over 48 h using in vivo fluorescence imaging. The results of real-time live imaging were then confirmed by ex vivo organ imaging and histological examination. Generally, PEG-PCL micelles were highly distributed into the lungs during the first 4 h post intravenous administration, then redistributed and accumulated in liver and spleen until 48 h post administration. No pathological impairment was found in the major organs studied. Thus, with loaded contrast agent and conjugated fluorochrome, PEG-PCL micelles as biodegradable and biocompatible nanocarriers are efficient multimodal imaging agents, offering high drug loading capacity, and sustained drug release. These might offer high treatment efficacy and real-time tracking of the drug delivery system in vivo, which is crucial for designing of an efficient drug delivery system.

Hydrophobic agents, a fluorescent dye (Nile red, NR) or an anticancer drug (doxorubicin, DOX), are encapsulated into poly((N‐[3‐(dimethylamino) propyl] methacrylamide)‐b‐poly (methyl methacrylate) (PDMAPMA‐b‐PMMA) nanoparticles (NPs) via one‐pot reversible addition‐fragmentation chain‐transfer (RAFT)‐mediated emulsion polymerization in water. The macroRAFT, PDMAPMA, is chain‐extended with the methyl methacrylate (MMA), with the hydrophobic agents soluble in MMA, resulting in loaded NPs, with either NR or DOX via polymerization‐induced self‐assembly (PISA). The NR‐loaded NPs are visualized by structured illumination microscopy (SIM), thus indicating the successful loading of the fluorescent dye into the PMMA core. The DOX‐loaded NPs exhibit a sustained release profile over 5 d, showing a small burst effect during the first 2 h, as compared with the free DOX. The DOX‐loaded NPs show higher cell toxicity than the free DOX in RAW 264.7 cell line. The results demonstrate the potential of using emulsion polymerization for synthesis of tailored and reproducible NPs encapsulating hydrophobic agents.