Marcos Augusto de Sá

Carbon nanotubes functionalized with sodium hyaluronate restore bone repair in diabetic rat sockets.

OBJECTIVE We evaluated the effects of sodium hyaluronate (HY) and carbon nanotubes functionalized with HY (HY-CNT) on bone repair in the tooth sockets of diabetic rats. MATERIALS AND METHODS Diabetes was induced by streptozotocin (50 mg kg(-1) i.v.), and the sockets were divided into normal control, diabetic control, diabetic treated with HY (1%), and diabetic treated with HY-CNT (100 μg ml(-1)) groups. The sockets were analyzed according to the percentage of bone formation and the number of cell nuclei. RESULTS The percentage of bone trabeculae was lower in diabetic control animals (11.16 ± 5.10% vs 41.92 ± 6.34% in normal animals) after 14 days. Treating diabetic animals with HY or HY-CNT significantly increased the percentage of neoformed trabeculae (HY: 29.43 ± 3.29%; HY-CNT: 36.90 ± 3.07%). Moreover, the sockets of diabetic animals had an increased number of cell nuclei and HY or HY-CNT reduced this parameter. CONCLUSION Our results indicate that HY and HY-CNT restore bone repair in the tooth sockets of diabetic rats, suggesting that these biomaterials are potential adjuvant therapies for the management of diabetes.

Single-walled carbon nanotubes functionalized with sodium hyaluronate enhance bone mineralization

The aim of this study was to evaluate the effects of sodium hyaluronate (HY), single-walled carbon nanotubes (SWCNTs) and HY-functionalized SWCNTs (HY-SWCNTs) on the behavior of primary osteoblasts, as well as to investigate the deposition of inorganic crystals on titanium surfaces coated with these biocomposites. Primary osteoblasts were obtained from the calvarial bones of male newborn Wistar rats (5 rats for each cell extraction). We assessed cell viability using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay and by double-staining with propidium iodide and Hoechst. We also assessed the formation of mineralized bone nodules by von Kossa staining, the mRNA expression of bone repair proteins, and the deposition of inorganic crystals on titanium surfaces coated with HY, SWCNTs, or HY-SWCNTs. The results showed that treatment with these biocomposites did not alter the viability of primary osteoblasts. Furthermore, deposition of mineralized bone nodules was significantly increased by cells treated with HY and HY-SWCNTs. This can be partly explained by an increase in the mRNA expression of type I and III collagen, osteocalcin, and bone morphogenetic proteins 2 and 4. Additionally, the titanium surface treated with HY-SWCNTs showed a significant increase in the deposition of inorganic crystals. Thus, our data indicate that HY, SWCNTs, and HY-SWCNTs are potentially useful for the development of new strategies for bone tissue engineering.

Thermomagnetic behaviour of quenched ribbons of Nd16Fe76B8

Abstract Magnetization and thermal demagnetization were studied on rapidly quenched ribbons. The thermomagnetic curves are explained on the basis of single-domain behaviour of non-interacting uniaxial particles described by the model of Stoner and Wohlfarth. There is a good qualitative agreement between theory and the experimental results confirming previous analysis of a Hopkinson effect in these samples.

O ensino-aprendizagem da anatomia humana: avaliação do desempenho dos alunos após a utilização de mapas conceituais como uma estratégia pedagógica

EnglishAbstract The aim of this study was to implement and evaluate the impact of the development of Concept Maps (MC), as a pedagogical strategy in teaching of Human Anatomy, one of the course subjects of Physical Therapy, from Federal University of Minas Gerais (UFMG). A total of 298 students, enrolled regularly, participated of the study over six semesters. The mean analysis of the final scores of the students, prior to the expansion of the MC Project, showed decrease of average score over the semester, which was reversed when the MC were implemented systematically. The implementation of MC were also capable of promoting a significant reduction in the failure rate. Thus, we conclude that the use of MC seems to have contributed to improving student performance and also the approval rating in the discipline of Anatomy, especially after the systematization of its use by the Teaching Project supported by the institution. portuguesResumo O objetivo deste estudo foi implementar e avaliar o impacto da elaboracao de Mapas Conceituais (MC) como estrategia pedagogica no ensino-aprendizagem da Anatomia Humana, uma das disciplinas do curso de Fisioterapia da Universidade Federal de Minas Gerais. Participaram do estudo 298 alunos regularmente matriculados, ao longo de seis semestres. A analise das medias das notas finais dos alunos, anteriores a ampliacao do projeto dos MC, demonstrou decrescimo dessas medias ao longo dos semestres, o que foi revertido quando o projeto de ensino de MC foi implementado sistematicamente. A implementacao dos MC tambem foi capaz de promover uma reducao significativa no indice de reprovacao. Assim, concluimos que o uso de MC parece ter contribuido para melhorar o desempenho dos alunos e tambem o indice de aprovacao na disciplina de Anatomia Humana, principalmente apos a sistematizacao do seu uso atraves do Projeto de Ensino apoiado pela Pro-Reitoria de Graduacao da Instituicao.

Enhancement of Bone Healing by Local Administration of Carbon Nanotubes Functionalized with Sodium Hyaluronate in Rat Tibiae.

It has been reported that carbon nanotubes (CNTs) serve as nucleation sites for the deposition of bone matrix and cell proliferation. Here, we evaluated the effects of multi-walled CNTs (MWCNTs) on bone repair of rat tibiae. Furthermore, because sodium hyaluronate (HY) accelerates bone restoration, we associated CNTs with HY (HY-MWCNTs) in an attempt to boost bone repair. The bone defect was created by a 1.6-mm-diameter drill. After 7 and 14 days, tibiae were processed for histological and morphometric analyses. Immunohistochemistry was used to evaluate the expression of vascular endothelial growth factor (VEGF) in bone defects. Expression of osteocalcin (OCN), bone morphogenetic protein-2 (BMP-2), and collagen I (Col I) was assessed by real-time PCR. Histomorphometric analysis showed a similar increase in the percentage of bone trabeculae in tibia bone defects treated with HY and HY-MWCNTs, and both groups presented more organized and thicker bone trabeculae than nontreated defects. Tibiae treated with MWCNTs or HY- MWCNTs showed a higher expression of VEGF. Treatment with MWCNTs or HY-MWCNTs increased the expression of molecules involved in the bone repair process, such as OCN and BMP-2. Also, HY- and MWCNT-treated tibiae had an increased expression of Col I. Thus, it is tempting to conclude that CNTs associated or not with other materials such as HY emerged as a promising biomaterial for bone tissue engineering.

Bone Repair Utilizing Carbon Nanotubes

One of the major challenges for researchers working on bone tissue engineering is developing biocomposites able to accelerate the repair of bone defects, thereby reducing the time and costs of patients rehabilitation. Since their discovery, carbon nanotubes (CNTs) have captivated investigators worldwide due to their remarkable mechanical, thermal and electrical properties, as well as their functionalization capability and biocompatibility. Recent studies have demonstrated that CNTs are among the unique biomaterials that hold potential clinical applications in bone tissue engineering and orthopedic procedures due to their impressive capacity of accelerating bone repair/regeneration. Significant progress has been achieved regarding the effects of CNTs associated or not with polymers in different experimental models (in vitro and in vivo). The purpose of this chapter is to summarize the recent developments in bone repair/regeneration using CNTs or CNT-based composites and to provide insights concerning future possible applications of CNTs on bone tissue engineering.