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Chemical engineering

Compatible with the body

Laboratory at UFMG synthesizes new generation of biomaterials

Amongst the innovations with biological functions developed at the Ceramic Materials Laboratory (LMC) of the Engineering School of the Federal University of Minas Gerais (UFMG) are materials able to activate the regeneration potential of human tissues and organs and devices for controlled release of medicines. The researchers synthesized several items using a chemical process called sol-gel. Depending on the intended use, objects with different shapes, consistencies, textures and sizes were obtained creating a new generation of biomaterials, more compatible and with greater power to interact with the functions of the organism.

The UFMG is about to get a Brazilian patent for a matrix for the controlled release of drugs, developed at the LMC. Presented in the form of a little disc to be implanted under the skin, the piece can be used in various kinds of treatment. At the LMC, the in vitro tests were carried out with a growth hormone, but the same device could release other kinds of hormones.

“The novelty lies in the application of the sol-gel process in the production of new materials with biological functions”, says Professor Wander Luiz Vasconcelos, the head of the LMC. The sol-gel method consists of the reaction of precursors, or chemical agents, usually alcoxides (compounds that are formed under the action of certain metals on an alcohol) that are transformed into gel, following reactions of hydrolysis and condensation. An inorganic structure is then formed, which allows the incorporation of organic groups, such as proteins, in the “empty spaces” between the structures or on the surface of the materials.

The method permits a structural control of the material, even at the nanometric level (one nanometer is equivalent to one billionth of a meter), making it possible for the “empty spaces” or pores that are formed between the structures to be occupied. “We work with a wide range of size of pores, which vary between a few nanometers to several micrometers (one micrometer is equivalent to one millionth part of a meter). According to the case, we can act on structures at the molecular level, and at other times we have a very large protein, with several molecules that do not fit into a nanometric structure”, explains Vasconcelos.

Release of drugs
Nanoengineering works on molecular structures on a nanometric scale, but the final device may have any size or shape. The incorporation of a substance of interest may occur on the surface of particles or in their volume, as the insides are called, with the occupation of the pores, which act like sponges. In the experiments with the matrix for releasing drugs, in this case a protein that simulates the effects of the growth hormone, octreotide was incorporated into the surface of the material. To recompose the tissues and organs, the process of incorporating the proteins of interest takes place in the “empty spaces” of the particles.

The new method for incorporating proteins in sol-gel matrixes, the fruit of research by Rúbia Lenza, who is studying for her doctorate under Vasconcelos’s supervision, yielded two scientific articles published in international magazines last year, and three this year. The chemical agents used were titanium and silicon alcoxides, in the process that resulted in the production of biomaterials to be applied as substrates for engineering in tissues and carriers of biologically active molecules, using the method of forming foam in polymers (compounds made up of long chains of molecules able to connect up with other molecules of the same species), with controlled porosity, in sol-gel solutions. A common protein called laminin was used to fill the “empty spaces” of the foam, in the basic tests for recomposing tissues.

Materials with superficial organic properties and planned pore sizes are particularly important in applications where the recognition of molecules is necessary, such as in the process of adsorption (fixing molecules of one substance on the surface of another substance) and in the controlled release of drugs. The results shown in research at the LMC suggest that the materials obtained have great potential for being used a support for tissue engineering and as carriers of biospecific molecules. Everything leads to believe that bioactive foam modified with proteins represents a new generation of materials that can be used in the regeneration of bone and muscle tissues.

A thousand uses
The sol-gel chemical process has been known for over a hundred years, but its application is relatively recent. It began to be used in the 1980’s, in some industries. Its application in new materials is so versatile that, amongst other things, it results in the production of a glass capable of blocking out light and heat in adherent films, to protect the most varied surfaces, and on a membrane with such filtering power that it can transform brackish water into drinkable water. In health, research with the application of sol-gel was intensified less than ten years ago, and quickly awoke the interest of researchers in several countries. In spite of all the advances, though, there is still much to be developed.

The production of ceramic materials via sol-gel offers advantages when compared with the conventional ways used in the production of glass and polymers, which require powerful furnaces, with high temperatures and lots of energy use. The first stages of the sol-gel process occur at room temperature. According to its use, it needs to be heated, although always more blandly than in the conventional processes. To give an idea, to get pure silicon through the quartz fusion by traditional means calls for a furnace heated to a temperature of over 2,000ºC. With sol-gel, the temperature does not go beyond 1,000ºC.

Long way
Its versatility, structural control, energy saving and residues that cause no environmental damage may attract the interest of the pharmaceutical industry. With regard to the final costs of biomaterials using sol-gel, at least for the time being, there are no definitive figures, because the process is still at the laboratory scale. Sol-gel is a typical case of the joint development of science and technology. “There are still many unknown quantities, but the great challenge lies in the development of technologies using this process”, explains Vasconcelos. He thinks that the applications of sol-gel are so vast that it becomes difficult to make any forecast. “People don’t know where it may get to. It is a hot subject worldwide “, says the researcher.

The researcher from the UFMG was one of the first in Brazil to work with sol-gel in the development of new materials. In 1992, Wander created the LMC, in the Metallurgical and Materials Engineering Department of the UFMG’s Engineering School. At the moment, he is supervising 16 students at the LMC, the majority about the synthesis of nanostructured materials using sol-gel, always with the prospect of making advances n the scientific and technological knowledge of these new materials that may shortly be common in hospitals and industries.