Scientists in Paris, France have engineered liposomes containing iron-oxide nanoparticles and photosensitizers, and have used them to ablate cancerous tumors in mice. While current experimental cancer treatments employ either magnetic hyperthermia techniques or photodynamic therapy, this work is a new attempt to combine the two techniques into one self-contained injectable vessel. Liposomes are spherical, self-assembling, lipid bilayer structures. In the lowest energy state the hydrophobic tails touch inside the bilayer, which forms a sphere with a hydrophilic outer shell and a hydrophilic inner cage useful for carrying drugs, or in this case iron-oxide nanoparticles.
Liposomes are a good choice for drug delivery because they are injectable, biocompatible, and less immune-responsive than drugs or particles alone. Cell membranes are made of lipid bilayers, and the liposomes can easily enter into the cytoplasm. The hydophobic portion of the liposomes is important in this application because the photosensitizer was incorporated into the lipid bilayer. In this way, each liposome contained both iron-oxide nanoparticles in the hydrophilic core, and photosenstizer within the lipid bilayer.
Magnetic hyperthermia is a method of tumor destruction in which ferromagnetic particles are injected into the tumor and an external field is applied in such a way to cause the particles to vibrate. This rapid vibration creates heat, which is damaging to the cancerous tissue. Photodynamic therapy is a cancer treatment method whereby a photosensitizer is targeted to a tumor. A photosensitizer is a compound that produces radical oxygen species (ROS) upon light absorption.
In this work the team created liposomes containing either iron-oxide particles or photosensitizers or a combination of both. They then applied them to cancerous cells in a culture dish, and also injected them into a live mouse with a mass of cancerous cells. The same magnetic field and light were applied in all situations. Both in vitro and in vivo, the liposomes containing both the magnetic nanoparticles and the photosensitizers were more effective at tumor destruction than either treatment alone. The most striking result was that in the live mouse, the dual treatment liposomes completely eradicated the tumor.
This exciting work provides extremely promising results suggesting that combining magnetic hyperthermia and photodynamic therapy is a more effective cancer treatment than either method alone, and that using liposomes to deliver the therapy is viable.
More detailed experimental information is available in the full article. Combining Magnetic Hyperthermia and Photodynamic Therapy for Tumor Ablation with Photoresponsive Magnetic Liposomes. Riccardo Di Corato, Gaëlle Béalle, Jelena Kolosnjaj-Tabi, Ana Espinosa, Olivier Clément, Amanda K. A. Silva, Christine Ménager, and Claire Wilhelm. ACS Nano. 2015. DOI: 10.1021/nn506949t
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