Oxygen depleted hypoxic regions in the tumour are generally resistant to therapies1. Although nanocarriers have been used to deliver drugs, the targeting ratios have been very low. Here, we show that the magneto-aerotactic migration behaviour2 of magnetotactic bacteria3, Magnetococcus marinus strain MC-14, can be used to transport drug-loaded nanoliposomes into hypoxic regions of the tumour. In their natural environment, MC-1 cells, each containing a chain of magnetic iron-oxide nanocrystals5, tend to swim along local magnetic field lines and towards low oxygen concentrations6 based on a two-state aerotactic sensing system2. We show that when MC-1 cells bearing covalently bound drug-containing nanoliposomes were injected near the tumour in SCID Beige mice and magnetically guided, up to 55% of MC-1 cells penetrated into hypoxic regions of HCT116 colorectal xenografts. Approximately 70 drug-loaded nanoliposomes were attached to each MC-1 cell. Our results suggest that harnessing swarms of microorganisms exhibiting magneto-aerotactic behaviour can significantly improve the therapeutic index of various nanocarriers in tumour hypoxic regions.

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Poly(ethylene glycol)/polylactic acid (PEG/PLA) nanoparticles (NPs) containing the hydrophobic antifungal itraconazole (ITZ) were developed to provide a controlled release pattern of ITZ as well as to improve its aqueous dispersibility and hence enhance its antifungal action. Two PEG/PLA copolymers (PEGylated PLA polymers) were used in this study; branched PEGylated polymer in which PEG was grafted on PLA backbone at 7% (mol/mol of lactic acid monomer), PEG7%-g-PLA, and multiblock copolymer of PLA and PEG, (PLA-PEG-PLA)n with nearly similar PEG insertion ratio and similar PEG chain length. ITZ-loaded PLA NPs were also prepared and included in this study as a control. ITZ-NPs were prepared from a 1 : 1 w/w blend of PLA and each PEGylated polymer either PEG7%-g-PLA or (PLA-PEG-PLA)n using an oil-in-water emulsion evaporation method. The NPs morphology, size and size distribution, zeta potential, loading efficiency, release profile and antifungal activity were characterized. All ITZ-NPs were nearly spherical with smooth surface and showed less aggregating tendency with a size range of 185-285 nm. All ITZ-NPs measured nearly neutral zeta potential values close to 0 mV. The % LE of ITZ was ∼94% for PEG7%-g-PLA NPs and ∼83% for (PLA-PEG-PLA)n at 15.3% w/w theoretical loading. PEG/PLA NPs were stable over time regarding size and size distribution and % ITZ loading efficiency (% LE). ITZ release showed an initial burst followed by a gradual release profile for ITZ-NPs over 5 days. (PLA-PEG-PLA)n NPs exhibited faster release rates than PEG7%-g-PLA NPs particularly at the last 2 days. Differential scanning calorimetry and powder X-ray diffractometry data confirmed that ITZ exists in an amorphous state or a solid solution state into the NPs matrix. Fourier transform infrared revealed the possibility of chemical interaction between ITZ and the NPs matrix polymer indicating the successful entrapment of ITZ inside the particles. In haemolysis test, ITZ-NPs caused mild haemolysis over the concentration range (5-20 µg/mL) compared to free ITZ, indicating better safety profile of ITZ-NPs. ITZ-loaded PEG/PLA NPs inhibited fungal growth more efficiently than either free ITZ or ITZ-loaded PLA NPs. Our results suggest that PEG/PLA-ITZ could be used efficiently as a nanocarrier to improve the aqueous dispersibility of ITZ, control its release over time and, thereby, enhance its antifungal efficacy.