The development of nanoparticles in the biomedical field concerns both the nature of systems and the cellular models used for testing which, in turn, enrich methods of treatment.
Researchers fighting disease will examine all possibilities to improve treatments and reduce side effects. While some will develop new molecular therapies, others will focus on conveying them more efficiently to the target. The basic problem often resides in the site of the action and the physicochemical properties of the molecules, which are vulnerable to any obstacle they come across.
One solution is the use of nanoparticles; these nanometric objects combine medicine and carriers. These vectors encapsulate the active substances and protect them from premature deterioration. Simple, furtive, operational, sensitive to endogenous or exogenous stimuli, these nanoparticle systems increase in complexity and selectivity.
A chemical bond that hits the mark
When an active substance is linked to its carrier it is called a prodrug. “This avoids a large quantity of medicine from being released immediately, and systems become less toxic. More active substances reach the target and less nanoparticles are administered”, explains Julien Nicolas, researcher in the Nanomedecine for Serious Diseases team, at the Galien Institute Paris-Sud (CNRS/Université Paris-Sud).
The team has discovered in particular the surprising properties of squalene, a lipid that is part of the same product family as terpenes, naturally present in the body. Like cholesterol, of which squalene is a precursor, it interacts with the lipoproteins in blood circulation, which then carries it to the cancerous cells. The system delivers the drug, like a Trojan horse, carried by squalene, to the heart of the tumours.
Small RNA but great impacts
Liliane Massade used this system in her research on junction oncogene cancers, in the Vectorology and Anticancer Therapies Laboratory (CNRS/Université Paris-Sud) at the Gustave Roussy Institute. Illegitimate chromosomal rearrangement is the source of 20% of cancers, and these are prime targets for a therapy based on the use of small interfering RNAs (or siRNAs), capable of inhibiting the target gene. “siRNAs are hydrophilic molecules that are rapidly dissolved. Squalene stabilises them and enables them to pass through membranes to reach the target tissue”, Liliane Massade explains. siRNAs that are characteristic of papillary thyroid carcinomas and linked to squalene can slow tumour growth down by 70 to 80% in model mice!
Within the framework of the collaborative project Nanoprotection of the NanoSaclay LabEx, the researcher is now studying the 1A form of the Charcot-Marie-Tooth disease, a hereditary, neurological disease where duplication of a chromosome causes an approximate 30% overexpression of the PMP22 protein (peripheral myelin protein 22). “The difficulty of this project resides in normalising the gene by partially inhibiting it”. One of the different siRNAs, built and tested in vitro, reached this goal. When injected in transgenic mice carrying the disease, a spectacular improvement in their motor function was observed and the disappearance of all other symptoms was noticeable. “We are now going to study the involved cellular and molecular mechanisms and standardise the treatment in order to rapidly proceed to clinical trials”.
Synthetic polymers in numbers
Central to Julien Nicolas’ research is finding the best carrier, which is easy to synthesise and functionalise while remaining non-toxic and efficient. “Vinyl polymers are ideal for chemical synthesis as they are well defined and easily functionalised. Labile chemical motifs are introduced to render them biodegradable. They are then tested for toxicity in vitro.” The most promising systems, after incorporation of drug and assessment on diseased cells, will be used for in vivo tests on small animals.
Mimicking the structure of tumours
It is not easy to move on to the in vivo stage: “We have noticed that some systems that are very efficient in vitro, do not work as efficiently when they are tested in vivo”, Simona Mura explains, researcher in the same team at the Galien Institute Paris-Sud. In vitro study conditions do not reproduce the structural complexity of tumours. This is why the researcher has perfected a 3D culture model. She studied, in particular, pancreatic cancer, which has a very low survival rate. “Failure in treatments is mainly due to their inefficient distribution in terms of cancerous cells, because of the matrix surrounding these cells, and collapse of blood vessels, which inhibits their conveyance”. She has developed a spheroid model by optimising her cell culture technique. It reproduces pancreatic cancer and its environment. “Its relevance has been confirmed by histological analysis and cytotoxicity tests”. She is now considering adding microfluidic conditions, to mimic the blood flow and to make this model even more biomimetic.
Gold, a metal that means us well
Bruno Palpant and his team work in the Quantic and Molecular Photonics Laboratory (CNRS/CentraleSupélec/ENS Paris-Saclay) where they are studying the therapeutic applications of plasmon resonance of gold nanoparticles. “We can put the nanoparticle electrons in collective oscillation and heat them in a localised way”, explains the researcher. The variation in temperature induces different effects on cancerous cells. “By lighting up these nano-objects with a laser, it is also possible to extract electrons to create free radicals, capable of destroying cancerous cells”.
∙ Massaad-Massade L. et al., New Formulation for the Delivery of Oligonucleotides Using "Clickable" siRNA-Polyisoprenoid-Conjugated Nanoparticles : Application to Cancers Harboring Fusion Oncogenes. Bioconjug Chem. 2018 Jun 20; 29(6) :1961-1972.
∙ Labouret T. et al., Plasmon-Assisted Production of Reactive Oxygen Species by Single Gold Nanorods. Small 2015.
∙ Lazzari G. et al., Multicellular spheroid based on a triple co-culture: A novel 3D model to mimic pancreatic tumor complexity. Acta Biomaterialia 2018, 78, 296-307
∙ Guégain E. et al., Degradable polymer prodrugs with adjustable activity from drug-initiated radical ring-opening copolymerization. Chem. Sci. 2018 Sep 13; DOI: 10.1039/C8SC02256A.
Profile : Liliane Massade
"From the moment you have a vector that exists naturally in the body such as squalene, preliminary toxicology studies at the clinical stage are reduced."
Liliane Massade is a Doctor of Sciences and Human Genetics (Université Paris Diderot). She is currently running the Targeted Therapies for Neuropathies team, at the Disease and Hormones of the Nervous System Laboratory (Inserm/Université Paris-Sud), at the Kremlin-Bicêtre hospital. She coordinates the collaborative project Nanoprotection of the NanoSaclay LabEx.
By Véronique Meder.