Miguel BoyayanTwo raw materials found in great quantities in Rio Grande do Sul, chitosan, a biopolymer prepared from the shells of shrimps and polyol, obtained from soybean oil, are the main components of a new substance for incorporating particles or the active principles used in preparing hair gel or for ultrasonography, in addition to being used to make insect repellants. Registered under the commercial name of Quiol-gel, it has a viscosity similar to the substances used currently in various pharmaceutical and cosmetic products and made from petrochemical polymers; the advantage of the new substance is that it is biocompatible and biodegradable.
“The product has a specific composition that allows the material to be applied directly to the skin after the incorporating the cosmetic or active ingredients”, says Professor Nádya Pesce da Silveira, from the Chemistry Institute of the Federal University of Rio Grande do Sul (UFRGS), and coordinator of the research. One of the main characteristics of Quiol-gel is the possibility of varying the viscosity of the formula. It is possible to obtain a gel, a lotion, a fluid or even a spray. To do so the it is only necessary to modify the conditions under which the macromolecules of chitosan, associated with the smaller molecules of polyol, are prepared and adjust them to the required pH.
The studies that gave rise to formulation of the gel began with the development of a biological nanoparticle that was given the name chitossome, the result of incorporating chitosan and liposome, a nanostructure that is similar to small spheres of fat and considered an excellent system for the controlled release of medication or biologically active substances. “The difference between this system and other similar ones is the preparation method, which means that the particle’s stability improves a lot”, says Nádya. Lipids extracted from soybean lecithin, a by-product of the production of soybean oil, were associated with chitosan, a natural molecule with antifungal properties, so that the system was more stable. “Chitossome remains stable for a month at room temperature without mold”, says Nádya. This property, allied to the fact that it is biodegradable and biocompatible, makes this nanoparticle a vehicle with great potential for encapsulating biological actives. “I can put a vaccine, an antioxidant, sun block or even medication inside chitossome”, she explains.
“Some application possibilities have already been tested. Chitossome prepared at UFRGS has been used as an adjuvant (vehicle for transporting substances) in vaccines against diphtheria, a bacterial illness that affects the throat and can lead to serious complications. The experiment was carried out by researchers from the Butantan Institute, coordinated by researcher, Maria Helena Bueno da Costa, from the Laboratory of Microspheres and Liposome of the Biotechnology Center, in partnership with researchers from the University of Havana, in Cuba. Three different formulae of diphtheria toxoid, the weakened toxin, were tested and compared. One of them consisted of the toxoid associated with the chitossome, another of the toxoid with normal liposome and the third, just the toxoid without any additional adjuvant. “The response of the chitossome as adjuvant was superior”, says Maria Helena. She says that she still does not know the adjuvant action mechanism of the chitossome, but that in the experiments with mice it was possible to see that more antibodies were produced.
The researcher pointed out that the method of incorporating chitosans with liposomes that was developed by Professor Nádya’s group is innovative. “The chitosan is placed both inside and outside the lipids”, she says. It is like a sandwich that improves the resistance of the particles. In other already known methods chitosan is only placed outside. “As the nanoparticles adhere to the tissue and slowly release the encapsulated substance there’s an increase in the effectiveness of the vaccine or of the encapsulated medication because contact with the body is prolonged”, explains Nádya. This means a saving in active substances and fewer collateral effects. A new study, currently being done by Maria Helena, uses chitossome as a model for an oral vaccine against diphtheria and bee stings. “It also induces a response in the mucosa, which is a great problem with real vaccines”, says the researcher.
Chitossome was also tested in association with melatonin, a substance produced in the brain by the pineal gland and found in small quantities in fruit, vegetables, cereals and aromatic plants, to evaluate how the formulation responds to the aging of the skin caused by solar radiation. The experiment was done by Master’s degree student, Manuela França Gonçalves, whose tutor is Professor Silvia Guterres, from the Department for the Production and Control of Medication at the School of Pharmacy at UFRGS, who is the coordinator of the Nanocosmetics Network, created and funded by the Ministry of Science and Technology. Professor Nádya was co-tutor for the part of the research that characterized the chitossome.
Melatonin associated with chitossome was compared with melatonin incorporated with a hydrogel. The two formulae were rubbed into the backs of mice that were then submitted to ultraviolet radiation. “Melatonin has an antioxidant effect, it protects against the aging of skin and the sun’s UVA radiation, which causes long term damage”, says Manuela. Chitossome helps transport the melatonin and may be a promising system for inclusion in skin applications, like sun block creams, because it is going to help protect the skin against the effects of UVA radiation. This means that chitossome could be associated with the physical and chemical filters in sun blocks that are already used to increase product effectiveness.
At the Institute of Food Sciences and Technology at UFRGS chitossome has been evaluated in association with enzymes by Professor Adriano Bradelli’s group. “For example, they may help cheese remain stable for longer”, says Nádya. There are several lines of study with various applications that go beyond the frontiers of cosmetics, an area in which research has already started.
MARÓN, L. B., et al. LUVs recovered with chitosan: a new preparation for vaccine delivery. Journal of Liposome Research. v. 17, ed. 3&4, p. 155-163, July. 2007.