Exosome-based “intelligent” vectors developed to deliver hyperthermia nanoparticles and cause cell death in disseminated tumour models

 

Aragonese scientists have developed intelligent shuttles to move nanoparticles to the inside of tumour cells and destroy them using heat and without drugs, following the “Trojan horse” strategy, as published today in the prestigious Journal of Extracellular Vesicles, the journal with the highest impact index in this field.

 

 

The article reports the work led by Pilar Martín-Duque and Jesús Santamaría, teaching and research staff at the University of Zaragoza and both members of the Aragon Institute for Health Research (IIS Aragón) and the Biomedical Research Centre for Bioengineering, Biomaterials and Nanomedicine Network (CIBER-BBN). Santamaría also belongs to the Instituto de Nanociencia y Materiales de Aragón (INMA, CSIC-UNIZAR).

 

 

The study “Transfer of photothermal nanoparticles using stem cell derived small extracellular vesicles for in vivo treatment of primary and multinodular tumours” also involves researchers from the Instituto de Nanociencia y Materiales de Aragón, INMA (UNIZAR – CSIC) and CIBER-BBN, María Sancho, Víctor Sebastián and Miguel Encinas, together with Lluis Luján and Estela Pérez, linked to the Instituto Agroalimentario de Aragón, (IA2, UNIZAR-CITA).

 

 

The authors have used cell vesicles (exosomes) as Trojan horses to carry hollow gold nanoparticles into tumours in animal models. “We have managed to reduce or eliminate tumours in mice without drugs, only with the heat generated by laser irradiation. In other words, we injected the exosomes with the nanoparticles into the tail of the mouse and they “seek out” the tumour on their own, not only in conventional models but also in multinodular models, similar to metastasis processes,” say the authors of the study.

 

 

The results obtained with this work represent a second very important advance in the trajectory of the research they have been developing for some time. In 2019, these scientists used exosomes as Trojan horses to carry palladium (Pd) catalysts to the interior of cancer cells and manufacture the chemotherapy drug in situ, but the demonstration was only carried out with cells. This work goes a step further, in in vivo models.

 

 

 

One of the most interesting aspects of nanotechnology is nanoparticles for oncology treatments. There are all kinds: toxic in themselves, capable of harbouring chemotherapeutic compounds, capable of heating or emitting electromagnetic radiation… However, all these structures faced the same problem: it was very difficult to make them reach the tumour selectively and produce cell death only inside the tumour.

 

 

Until now, the main strategies to deliver particles to tumours were of two types, those based on the EPR effect (which exploits defects in the tumour vasculature to introduce nanoparticles) and those called active targeting, which decorate the particles with a wide variety of biomolecules, especially antibodies, as tumour recognition agents. Despite these efforts, recent studies have shown that only a small fraction of nanoparticles (usually less than 1%) reached tumours.

 

 

 

The work presented today marks an important difference in this respect: the authors have used cellular vesicles (exosomes) as Trojan horses to deliver gold nanoparticles into tumours in animal models. “We have used the natural biogenesis process of exosomes to obtain vesicles loaded with gold nanoparticles, and these vesicles have demonstrated their ability to strongly improve access to tumours with respect to the EPR effect, and not only in a “xenograft” model, but in a multinodular model, which simulates a metastatic growth invading spleen and pancreas,” says Pilar Martín-Duque, senior lecturer at the Faculty of Medicine.

 

 

“I am convinced that extracellular vesicles, and particularly exosomes, hold the key to overcoming some of the limitations of nanomedicine,” says Jesús Santamaría, Professor of Chemical Engineering at the University of Zaragoza, who holds two ERC Advanced Grants. He adds: “Although there is still a long way to go to achieve truly targeted delivery, the combination of active targeting provided by exosomes and remote activation of hyperthermia particles opens up extraordinary possibilities.

 

 

This work has used hollow gold nanoparticles, already developed by the group in previous research, which belong to what are known as “plasmonic nanoparticles” and which have the capacity to heat up when they receive near-infrared radiation, the radiation that penetrates the body most deeply. It is therefore a drug-free treatment that uses the heat generated by the particles to produce cell death around them. But “these particles are useless if they cannot be delivered to the tumour, and this is where the exosomes come in, the fundamental piece in this Trojan Horse strategy,” says Pilar Martín-Duque.

 

 

The system is in principle very safe because the hyperthermia particles are only activated when they are illuminated by the laser (i.e. even if there are particles in healthy tissue outside the tumour, only those in the laser beam would be activated). However, it is critical to obtain a sufficient mass of nanoparticles to have the desired effect. Therefore, it is necessary to increase the amount of particles reaching the tumour. According to Santamaria, “delivery by exosomes still needs to be perfected, but nevertheless in this work we have shown that twice (and in some cases three times) as many particles reach the tumour as when the same amount is delivered using the EPR effect”.

 

 

 

This work can be seen as a first step towards the ideal therapeutic vector: on the one hand, the selective tropism of exosomes, which are able to recognise other cell membranes (such as those of cells of the same lineage, or tumour cells, in the case of mesenchymal stem cell exosomes), is used. On the other hand, a highly biocompatible charge (hollow gold particles), which, however, become lethal when illuminated with light of the appropriate wavelength.  The authors’ lab is investigating the use of Trojan horse strategies to deliver therapeutic particles (metallic particles capable of heating the environment by hyperthermia, or catalysts that generate toxic molecules once they reach the tumour) to the tumour.

 

Transfer of photothermal nanoparticles using stem cell derived small extracellular vesicles for in vivo treatment of primary and multinodular tumors.

María Sancho-Albero, Miguel Encinas-Giménez, Víctor Sebastián, Estela Pérez, Lluis Luján, Jesús Santamaría, Pilar Martín-Duque

Journal of Extracellular Vesicles 2022