Featured paper: Antimicrobial dental implants.

SEM image of the new antibiofilm coating.
SEM image of the new antibiofilm coating.

Bacterial biofilms are formed by communities embedded in a self-produced polymeric matrix forming a three-dimensional structure. Biofilms grow attached to the most diverse surfaces, natural or artificial, and can include a variety of bacteria and fungi. When found on our teeth, these microbial communities can cause well-known health damage, such as dental caries. Even inside the mouth, where biofilms tend to form, dental implants can also be harmed by the action of biofilms. In fact, the main cause of failure in dental implants is related to infections in the tissues surrounding the implant, due to bacterial accumulation on the titanium screws implanted by a surgeon dentist in the jaw bone or maxilla to support the dental prosthesis.

In light of this problem, a team of researchers from areas related to dentistry and materials developed a coating capable of reducing the adhesion of bacteria and fungi to the titanium surface, thus attacking the formation of biofilms in its initial stage. In the new coating, the bacterial adhesion was eight times less than in uncoated titanium. In addition, the coating changed the composition of the microbial population in the biofilms that appeared on the surface. Thus, the presence of bacteria directly responsible for generating infections around the implants was seven times less in the coating than in the uncoated titanium. “Our coating not only reduced the adhesion of microorganisms, but also modified its composition to a less aggressive host profile,” summarizes professor Valentim Adelino Ricardo Barão (UNICAMP), corresponding author of the paper related to the study, recently published in ACS Applied Materials and Interfaces. Finally, in addition to generating antibiofilm properties on titanium, the coating maintained this material’s biocompatibility, allowing the growth of human cells on its surface, and increased its resistance to corrosion.

According to the authors of the work, this new coating may be a promising strategy to control the formation of biofilms in titanium implants and thus reduce the development of microbial infections. “Countless coatings have been developed in this area,” contextualizes Professor Barão. “However, the ones available on the market aim, mainly, to improve biomechanical properties and biocompatibility, but not effective in reducing the accumulation of microorganisms.” According to the authors of the article, in order to apply coated titanium to patients and make it available on the market, it would be necessary to test its insertion as a dental implant in animal models and, finally, to conduct a controlled clinical trial that contemplates the insertion of the material in humans.

From developing the material to in vitro and in situ studies

The authors of the paper. From the left: Joao Gabriel Silva Souza, Martinna M. Bertolini, Raphael Cavalcante Costa, Jairo Matozinho Cordeiro, Bruna Egumi Nagay, Amanda B Almeida, Belén Retamal-Valdes, Francisco Nociti, Magda Feres, Elidiane Cipriano Rangel, and Valentim Adelino Ricardo Barao.
The authors of the paper. From the left: Joao Gabriel Silva Souza, Martinna M. Bertolini, Raphael Cavalcante Costa, Jairo Matozinho Cordeiro, Bruna Egumi Nagay, Amanda B Almeida, Belén Retamal-Valdes, Francisco
Nociti, Magda Feres, Elidiane Cipriano Rangel, and Valentim Adelino Ricardo Barao.

The research was carried out within the doctorate of João Gabriel Silva Souza, with guidance from Professor Barão and funding from Brazilian agencies Fapesp and Capes. The thesis was defended in 2019 in the Graduate Program on Dental Clinic of the School of Dentistry at UNICAMP Piracicaba.

The main objective of the thesis, says Souza, was to develop a coating for titanium, a widely used material in dentistry, that has the ability to reduce microbial accumulation by using low-pressure plasma technology. Bibliographic searches have shown that a superhydrophobic surface would be a promising alternative to reduce the adhesion of bacteria to titanium and its alloys. A surface is considered to be superhydrophobic (that is, very difficult to wet) when the angle formed between it and a drop of water is greater than 150º. Superhydrophobicity, in turn, is based on high surface roughness and chemical composition.

“Based on this idea and previous studies already developed by Professor Barão’s research group, we aimed to develop a superhydrophobic coating with plasma technology, changing various parameters, such as pressure, gases, etc.” says Souza.

The coating was developed and characterized at the Laboratory of Technological Plasmas – UNESP – Sorocaba, which includes the Multi-User Laboratory for Characterization of Materials, under the guidance of Professor Elidiane Rangel. “Professor Elidiane has broad experience in the area and has been contributing extensively to our research group in the development of coatings for dental applicability,” explains Professor Barão.

While the scientific literature recorded superhydrophobic coatings manufactured mainly in two stages (one to obtain roughness and the second to achieve hydrophobicity), Professor Rangel manufactured the coating in just one step, using the technique of PECVD (plasma-enhanced chemical vapor deposition). In this technique, an atmosphere of carefully selected gases is formed inside a reactor (in this case, oxygen, argon and hexamethyldisiloxane, of the formula C6H18OSi2). This atmosphere is highly energized (in a plasma state) after applying an electrical voltage, when the gases decompose and generate species (atoms, molecules, ions) with great propensity to react chemically. These species form new compounds that are deposited in a solid state on the surface of the material to be coated (in this case, titanium).

To manufacture the superhydrophobic coating using this technique, Professor Elidiane carried out a unique 60-minute process. The result was a surface based on silicon and oxygen, similar in appearance to cauliflower, with a different roughness. Making an analogy with the relief of our planet, the coating presented, on the micrometric scale, mountains of different heights and shapes, separated by valleys and canyons.

After obtaining the coating, in order to test its effectiveness as an antibiofilm, the study involved research groups from the University of Guarulhos and the University of Connecticut Health Center (USA), where the then doctoral student Souza carried out a doctoral internship.” In addition, the Brazilian National Nanotechnology Laboratory (LNNano) and the Brazilian Biosciences National Laboratory (LNBio) were used to characterize the coating and analyze the composition of adhered proteins, respectively.

The team of scientists then carried out a series of microbiological tests and analyses, both in the laboratory (in vitro) and in the mouth of volunteers (in situ), always comparing uncoated titanium and the titanium with the superhydrophobic coating. In one of the in vitro experiments, they used natural saliva as a culture medium for several microorganisms usually found in biofilms that grow on the implants. In contact with this medium, the coated titanium samples showed a very good antibiofilm performance with respect to the uncoated titanium: the adhesion of the set of microbes was eight times lower, and, in particular, the adhesion of a bacteria directly responsible for the formation of the biofilm matrix was 17 times smaller. Consequently, in a later stage of the experiment, biofilm formation in the coating was scarce and sparse.

In another interesting test, carried out in situ, four volunteers used a device on the palate during 3 days. This device was made with some untreated titanium discs and others with a superhydrophobic coating. When analyzing the composition of biofilms formed on the two surfaces, with the collaboration of professor Magda Feres of the University of Guarulhos, the researchers were once again surprised by the positive performance of the developed coating, which reduced by seven times the presence of pathogens directly associated with infections that lead to dental implant failures.

Above and to the left, 3D reconstruction based on confocal laser microscopy shows the dense formation of peaks in the new coating. High roughness with respect to uncoated titanium (control) can also be seen below. In the center, the obtained superhydrophobicity: the drop of water does not spread on the surface. On the right, images show the coating with proliferation of human cells, showing biocompatibility (above) and with reduced bacterial accumulation (green spots), below.
Above and to the left, 3D reconstruction based on confocal laser microscopy shows the dense formation of peaks in the new coating. High roughness with respect to uncoated titanium (control) can also be seen below. In the center, the obtained superhydrophobicity: the drop of water does not spread on the surface. On the right, images show the coating with proliferation of human cells, showing biocompatibility (above) and with reduced bacterial accumulation (green spots), below.

Featured paper: Clay Labyrinth in Hydrogel Matrix for Controlled Drug Release.

[Paper: Highly Controlled Diffusion Drug Release from Ureasil–Poly(ethylene oxide)–Na+–Montmorillonite Hybrid Hydrogel Nanocomposites. ACS Appl. Mater. Interfaces, 2018, 10 (22), pp 19059–19068. DOI: 10.1021/acsami.8b04559]

Clay Labyrinth in Hydrogel Matrix for Controlled Drug Release

By combining a clay and a polymer gel at the nanoscale, a brazilian scientific team with members of the São Paulo State University (UNESP) and the University of Franca (UNIFRAN) developed a new material that can carry drugs and release them in a gradual and controlled manner.

The team tested in vitro – that is, in the laboratory, in containers that simulate the biological conditions – the performance of the material in the release of sodium diclofenac. This drug is an anti-inflammatory, given orally or by injection, widely used to relieve swelling and pain from, for example, arthritis, rheumatism, muscle injuries, surgeries or gout.

The material developed is a nanocomposite that includes polymeric hydrogel, clay and the drug. The hydrogel (gel that absorbs water amounts higher than normal without dissolving) is composed of an organic-inorganic hybrid material known as siloxane-polyether or ureasil. The clay is known as montmorillonite, and is present in the nanocomposite in the form of nanometric lamellae homogeneously dispersed in the hydrogel. The diclofenac sodium, which appears encapsulated within the nanocomposite, is incorporated into the material during its preparation, as if it were another “ingredient”.

The nanocomposite was obtained by the São Paulo team through the sol-gel process. This preparation method is based on a series of chemical reactions with the transformation of a “sol” (liquid with nanometric particles in suspension) into a gel (rigid three-dimensional network with interstices in which the liquid remains immobilized).

In this nanocomposite the main function of the hydrogel, which is hydrophilic, is absorbing water from the external environment and storing it in its interstices. In this aqueous environment, the drug molecules disperse due to the physical diffusion process until they cross the pores of the hydrogel and exit into the external environment, in this case the human body if the material were being used to release drugs into real patients.

clay hydrogelThe main novelty of the material is the use of clay, which is impermeable, to control how the drug is released. In fact, in the material developed by the São Paulo team, the nanometric clay lamellae acted as a physical barrier to the passage of the molecules of water and drug.

As shown in the image below, the lamella set formed a real labyrinth that slowed the movement of these molecules, determining a specific rhythm to water absorption and the release of diclofenac sodium.

“The main contribution of this work was to develop a barrier system based on an organic-inorganic hybrid material containing polymer-clay for the fine control of the diclofenac sodium release,” says Eduardo Ferreira Molina, corresponding author of an article on the subject, recently published in the journal ACS Applied Materials & Interfaces. Molina is currently a professor at the University of Franca (SP).

In the work reported in this journal, the authors prepared a series of samples of the nanocomposite using different proportions of montmorillonite clay, as well as samples of the clayless hydrogel. The scientists used different characterization techniques to analyze the structure of the nanocomposites and their phases (hydrogel and clay) and also to study water absorption and release of the drug in the material. The team was able thus to verify that the presence of the clay was essential to control the way the drug was released. By adjusting the clay percentage used in nanocomposite preparation, the researchers were able to prevent the early release of a large dose of sodium diclofenac (a common problem in drug delivery systems). They also succeeded in releasing it slowly and at a steady and predictable rate.

The results of this work may constitute a first step towards the use of this nanocomposite as a drug release system for prolonged treatments of arthritis, migraine, postoperative pain and etc. With a system like this, medication could be released gradually at the most appropriate doses and rates, keeping the ideal concentration of the drug in the bloodstream.

Celso R. N. Jesus (left), first author of the paper and Eduardo F. Molina, corresponding author.
Celso R. N. Jesus (left), first author of the paper and Eduardo F. Molina, corresponding author.

The work, which received funding from the Brazilian federal agencies CAPES and CNPq and the São Paulo State agency FAPESP, was carried out at the Chemistry Institute of UNESP, in the city of Araraquara, with the exception of small-angle X-ray scattering (SAXS) measurements, performed at the Brazilian Synchrotron Light Laboratory (LNLS), in the city of Campinas.

The research was developed between 2010 and 2014 in the doctorate in Chemistry of Celso Ricardo Nogueira Jesus, under the supervision of Professor Celso Valentim Santilli (UNESP) and Professor Sandra Helena Pulcinelli (UNESP). The idea, previously unpublished, of developing these nanocomposites to function as barriers to controlled drug release arose at the beginning of the doctoral research of Nogueira Jesus. The theme brought together themes developed in two other postgraduate works. On the one hand, Eduardo Molina’s doctoral research, guided by Professor Santilli, on siloxane-polyether for controlled release of drugs. In 2010, this work was in the final phase. And on the other hand, Márcia Hikosaka’s master’s work, guided by Professor Pulcinelli and completed a few years ago, on the preparation of nanocomposites with polymers and montmorillonite clay.

Featured scientist: interview with Carlos Graeff.

Prof. Carlos Graeff
Prof. Carlos Graeff

Fascinated by science since he was a child, with a representative at his home (his father, a renowned neuroscientist), Carlos Frederico Oliveira Graeff, born at Ribeirao Preto (state of São Paulo), chose the area of Physics as his university studies. He obtained his bachelor’s (1989), master (1991) and doctor (1994) degrees in Physics from the University of Campinas (Unicamp). During his master’s and doctorate program, supervised by professor Ivan Chambouleyron, he took his first steps as a researcher in the Materials area with studies on materials based on germanium and silicon. During his doctorate he participated in a research internship at the Max Plank Institut für Festkörperforschung in Germany.

He returned to Germany in 1994 until 1996 for a postdoctoral period to work on electronic magnetic resonance, semiconductors and electronic devices at the Walter Schottky Institute of the Technische Universität München (TUM), with a grant from the German foundation Alexander Von Humboldt.

Upon returning to Brazil, he became a professor at the Department of Physics and Mathematics of the University of São Paulo (USP), where he remained for 10 years. In 2006, he joined the Faculty of Sciences of Bauru at the State University of São Paulo (UNESP) as a full professor, where he is still teaching and researching. Throughout his academic career, Graeff has been visiting professor or researcher at several institutions in France, China and Switzerland.

From 2007 to 2009, Graeff was coordinator of the Post-Graduate Program in Materials Science and Technology (POSMAT) at UNESP – Bauru campus. Between 2009 and 2014, he was the coordinator of the newly created Materials Area of CAPES, responsible for the evaluation of Brazilian post-graduate programs in Materials, among other functions. From 2011 to 2013, Graeff was president of the Humboldt Club of Brazil and in 2012 and 2013 he was scientific director of B-MRS. The scientist also fulfilled or performs management or advisory functions at Brazilian agencies FAPESP and CAPES, and at IUPAC (International Union of Pure and Applied Chemistry).

In 2017, after having participated in the editorial board of several international journals, he was appointed associate editor in the photovoltaic area of the journal Solar Energy (impact factor 4,018), of Elsevier publishing house. Also in 2017, he became Dean of Research at UNESP, a post he holds until now.

With an h index of 28, Graeff is the author of about 200 indexed papers that have more than 2,500 citations, according to Google Scholar. In three decades of scientific work, together with his team at the Laboratory of New Materials and Devices at UNESP and his numerous national and international collaborators, Graeff has contributed to the field of materials research with multiple subjects. Among his most cited articles there are studies on synthetic diamond, silicon and germanium heterostructures, conjugated polymers, latex and melanin (biological material with semiconductor properties that are promising for the development of bioelectronic devices).

The researcher has also worked in the area of photovoltaic energy (direct conversion of solar radiation into electricity), with numerous contributions to the development of solar cells based on different materials (dyes, perovskites and organic semiconductors). On this subject of photovoltaic energy, Carlos Graeff will offer a plenary lecture at the XVII B-MRS Meeting, to be held in Natal (RN) from September 16 to 20.

The following is an interview with this outstanding researcher of our community.

B-MRS Newsletter: How or why did you become a scientist? Did you always want to be a scientist? Also, briefly tell us what led you to work in the field of materials.

Carlos Graeff: My father, Frederico Graeff, is a well-known researcher and perhaps one of the most important influences in my decision. My aunts were also teachers and researchers, so from an early age I had access to the world of science from my home, which has always fascinated me. The decision to study physics was largely due to the various books I read and from the television Cosmos series presented by Carl Sagan. The decision to work in the Materials area came later on during my baccalaureate in physics after the first courses in condensed matter physics and semiconductors. From the beginning of the graduate studies I worked in materials, and soon I was attracted by the interfaces of physics with chemistry and biology in very different subjects of materials science and engineering.

B-MRS Newsletter: What do you believe are your main contributions to the Materials area? Please consider all aspects of scientific activity.

Carlos Graeff: It is always difficult to choose key contributions. In my case in particular it is easy to see, reading my CV, a very eclectic trajectory in terms of studied materials and applications. Using originality as a preference, I will dwell on three themes; the first is the production of CoS (cobalt sulfide) the basis of ecological paints for the production of electrodes for solar cells. We have achieved a simple, industrial and ecological method to replace platinum in dye-based solar cells. In the second theme, we have proposed several alternative methods for the synthesis of melanin, the material involved in tanning, and with this we have been able to produce biocompatible materials with very special characteristics with regard to, for example, solubility. We are identifying a very important defect for this material using, as a main tool, computational simulations combined with spectroscopic techniques. We are sure this material will be important in the emerging area of bioelectronics. In the third theme, we describe in detail the whole degradation process of organic semiconductors, identifying routes for the production of high sensitivity dosimeters for applications in hospitals and clinics that use, for example, gamma rays for cancer treatments and diagnosis. We also have had very unique contributions in the physics of electrically detected magnetic resonance, increasing the sensitivity and the general understanding of the physical phenomena involved. In addition to these fundamental contributions, I was responsible, proudly and with satisfaction, for the implementation of the materials area at CAPES. Another source of satisfaction regards the good students I was fortunate enough to mentor, many of them brilliant scientists. I helped and coordinated the assemblage of several laboratories both here in Brazil and abroad, most recently I helped set up a magnetic resonance laboratory in China.

B-MRS Newsletter: Now we invite you to leave a message for our readers who are starting their scientific careers.

Carlos Graeff: I started my master’s degree in 1989, a time that was perhaps as troubled as the current one, do not get discouraged! With focus and a bit of luck it is always possible to create new ideas, build a solid career and contribute to our beautiful country. We are going through a great revolution, with the emergence of new technologies that will profoundly transform society. Intelligence will increasingly play a decisive role in the direction of our society, be prepared to work in this new world of great opportunities. Always seek out dialogue with specialists from the most different areas of knowledge and from various countries. Quite possibly, in the coming years we will unravel the mysteries of how the brain works, we will master limitless forms of energy and ecological production, generate artificial intelligence. Open up to what is new, be bold, Brazil needs your citizen and entrepreneurial spirit.

B-MRS Newsletter:  You will deliver a plenary lecture at the XVII B-MRS Meeting. Leave an invitation to our community.

Carlos Graeff: Photovoltaic energy is reaching its commercial maturity, we are living an unprecedented energy revolution. In the lecture I will show some updated data on the perspectives of using photovoltaic cells in Brazil and in the world; its principles of operation; the challenges for scientists and material engineers in this relentless race for increasingly efficient, durable and environmentally friendly materials, processes and devices. I will present our group’s latest results on this topic.

B-MRS members named editors of international scientific journals.

Prof. Novais de Oliveira Jr (left), associate editor of ACS Appl. Mater. Interfaces with editor-in -chief Prof. Schanze at XVI B-MRS Meeting.
Prof. Novais de Oliveira Jr (left), associate editor of ACS Appl. Mater. Interfaces with editor-in -chief Prof. Schanze at XVI B-MRS Meeting.

B-MRS President Osvaldo Novais de Oliveira Junior is the newest associate editor of ACS Applied Materials and Interfaces, an ACS Publications journal with an impact factor of 7,504. The full professor of IFSC – USP (Institute of Physics of São Carlos of the University of São Paulo) assumed this post in early September. At B-MRS, Oliveira Junior has been administrative director and counselor, and has been chairing the society since early 2016.

The Solar Energy journal (impact factor 4,018) also recently incorporated a member of B-MRS among its editors, Carlos Frederico de Oliveira Graeff, full professor and pro-rector of research at Unesp (Universidade Estadual Paulista Júlio de Mesquita Filho). Graeff was named associate editor in the area of Photovoltaics in this periodical of the publisher Elsevier. A member of B-MRS since its beginning, Graeff was scientific director of the society and served on the scientific committee of the B-MRS Newsletter.

Finally, Carlos José Leopoldo Constantino, also a professor at Unesp and a member of the B-MRS community, took over as Associate Editor in the Nanomaterials area of the Journal of Nanoscience and Nanotechnology (Impact Factor 1,483) from American Scientific Publishers.

Prof. Graeff (left) and Constantino, associate editors of international journals.
Prof. Graeff (left) and Constantino, associate editors of international journals.

Postdoctoral Fellowship in Condensed Matter Physics.

The Laboratory of Nanostructured Films and Spectroscopy at São Paulo State University (UNESP), http://www.unesp.br/international/, campus in Presidente Prudente, SP, Brazil, invites applications for a postdoctoral research fellowship in the field of micro-Raman and SERS (surface-enhanced Raman scattering) spectroscopy, and Cell Membrane Models funded by Foundation for Research Support of the State of São Paulo (FAPESP) contract.  The successful candidate will conduct research on the molecular interaction between analytes of interest and cell membrane models, which includes the following activities:

  1. Synthesis of metallic nanoparticles applied as “SERS substrate”.
  2. Incorporation of such nanoparticles in Langmuir and Langmuir-Blodgett (LB) films and vesicles of phospholipids, applied as cell membrane models.
  3. Investigate the interactions between the analytes of interest and the cell membrane models using micro-Raman and SERS spectroscopy.
  4. From the results, propose molecular mechanisms involved in the interaction cell membrane models/analytes.
  5. Develop a methodology that allows investigating the cell membrane models in a complementary way using both micro-Raman techniques (SERS) and confocal fluorescence microscopy.

The fellowship for postdoctoral researchers allows you to carry out a long-term research project (18 months), starting at September/01/2017.

Applicants must have a Ph.D. in physics, chemistry, or related fields.  Experience in phospholipid self-assembly and basic optical microscopy and vibrational spectroscopy is required.   The successful candidate must have excellent communication skills and excel in a highly collaborative research environment. In addition to the timely publication of research results in peer-reviewed journals, the responsibilities of the postdoc include drafting progress reports.  Interested individuals should send (i) CV with the list of publications and (II) two letters of recommendation to case@fct.unesp.br. The deadline for application is July /31/2017.

Available facilities: http://www.fct.unesp.br/#!/departamentos/fisica-quimica-e-biologia/laboratorios/lab-filmes-finos-e-esp-raman/