Tissue reaction after subcutaneous implants of a new material composed of ethylene-vinyl acetate and starch for future use as a biomaterial.

This study aimed to evaluate the tissue reaction of ethylene-vinyl acetate (EVA) in 4 different compositions and processing: EVA foamed at high pressure with ultrasound (EVACU); EVA with 15% starch foamed at high pressure with ultrasound (EVAMCU); EVA with 15% starch foamed at high pressure without ultrasound and EVA foamed at high pressure without ultrasound as future use as a porous scaffold. Scanning electron microscopy images showed the influence of starch, reducing the diameter of pores. The number of open pores was also reduced with the addition of starch. The ultrasound applied during the manufacturing of composites does not affect these characteristics. Eighteen rats were used to test the tissue reaction of materials and PTFE (polytetrafluoroethylene), proven biocompatible material. After 7, 15, and 60 days of surgery, the materials were removed and processed for microscopic evaluation and counting of the inflammatory infiltrate. The data shows inflammatory reaction similar to PTFE. However, in the quantitative analysis at 60 days, the EVACU and EVAMCU showed less quantity of mononuclear cells (p < 0.05). Thus, the results suggest that the use of ultrasound in the production method (EVA) seems to have improved cell behavior regarding the reduction of infiltration over the period, with tissue response equivalent to the PTFE. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 400-407, 2019.

Novo biomaterial composto de EVA (polietileno-co acetato de vinila) para enxerto "onlay" em tecido ósseo / New biomaterial composed of EVA (polyethylene-co-vinyl acetate) for onlay grafting in bone tissue

Introdução: o EVA (polietileno-co acetato de vinila) é um tipo de espuma, com baixo custo e ampla gama de aplicações. Misturas de EVA e amido proporcionam diferentes tipos de estrutura porosa favorecendo seu uso como scaffold para regeneração tecidual óssea. Objetivo: resultados prévios mostraram reação tecidual favorável ao seu uso como biomaterial, sendo assim, os mesmos foram investigados para fins de regeneração óssea. Método: nesse trabalho, 22 ratos linhagem Wistar foram divididos em dois grupos (4 destinados ao experimento piloto e 18 destinados ao projeto). Primeiramente, 4 animais foram submetidos à cirurgia na calota craniana para en xerto onlay em tecido ósseo dos biomateriais: 1) EVA com amido a 15% espumado em alta pressão com ultrassom (EVAMCU), 2) EVA espumado em alta pressão com ultrassom (EVACU), 3) EVA espumado em alta pressão sem ultrassom (EVASU), 4) EVA com amido a 15% espumado em alta pressão sem ultrassom (EVAMSU). Após 30 dias do pós-operatório, os biomateriais EVACU e EVAMCU apresentaram resultados microscópicos com fibrovascularização favorável e bom desempenho. Em sequência, 18 ratos foram submetidos à cirurgia de enxerto e após 7, 14 e 90 dias, 6 animais foram submetidos à eutanásia para coleta dos biomateriais e tecidos adjacentes da calota craniana. Foi realizada análise qualitativa da região de fibrovascularização, bem como do possível potencial osteogênico da região ao redor dos biomateriais ao longo dos períodos. Resultados e Conclusão: os biomateriais testados demonstraram biocompatibilidade e capacidade para regeneração óssea, no entanto, mais estudos precisam ser realizados, como por exemplo, em defeitos ósseos bicorticais.

Introduction: the EVA (polyethylene-co-vinyl acetate) is a kind of foam with low cost and wide range of applications. EVA and starch mixtures provide different types of porous structure favoring its use as scaffold for bone tissue regeneration. Objective: Previous results showed tissue reaction favorable to its use as biomaterial, and thus, they were investigated for purposes of bone regeneration. Method: in this study, 22 male Wistar rats were divided into two groups, 4 of them for the pilot experiment and 18 for the project. First, 4 animals underwent surgery on the skull cap for onlay graft in bone tissue of the biomaterials: 1) EVA with starch to 15% foamed at high pressure with ultrasound, 2) EVA foam at high pressure with ultrasound, 3) EVA foam for high pressure without ultrasound, 4) EVA with 15% starch foamed at high pressure without ultrasound). The results were evaluated microscopically 30 days after surgery and the biomaterials EVACU and EVAMCU presented good performance with favorable fibrovascularization. Eighteen rats were submitted to graft surgery and after 7, 14 and 90 days, 6 animals were submitted to euthanasia for the collection of biomaterials and adjacent tissues of the skullcap. A qualitative analysis of the region of fibro vascularization was performed, as well as the potential osteogenic based on the microscopic findings of the region surrounding the biomaterials throughout the periods. Results and Conclusion: the biomaterials tested demonstrated biocompatibility and capacity for bone regeneration, however, more studies need to be performed, for example, on bicortical bone defects.

New LLLT protocol to speed up the bone healing process-histometric and immunohistochemical analysis in rat calvarial bone defect.

A new low-level laser therapy (LLLT) protocol is proposed and compared to another previously studied, in animal models, aiming to establish a more practical LLLT protocol. Protocol 1, the same used in other works and based on the clinical LLLT protocol for bone regeneration, consists of punctual transcutaneous applications in the defect region with fluence of 16 J/cm(2) every 48 h for 15 days. Protocol 2, proposed in this work, consists of three sessions: the first application directly on the defect site with fluency of 3.7 J/cm(2), during the surgical procedure, followed by two transcutaneous applications, 48 and 120 h postoperatively. The Thera Lase® (λ = 830 nm) was used, and the dosimetry of the first application of protocol 2 was calculated based on in vitro studies. Forty-five male rats were used, in which critical-size bone defects with 8 mm of diameter were surgically created in calvaria. The animals were randomly divided into three groups of 15 animals, named group 1 (protocol 1), group 2 (protocol 2), and control, which was not submitted to laser treatment. After 7, 15, and 45 days, five animals of each group were euthanized, and the pieces of calvarial bone were collected for microscopic and immunohistochemistry for vascular endothelial growth factor (VEGF), osteocalcin (OC), and osteopontin (OP) analysis. Histomorphometry showed that newly formed bone of 15-day samples from group 2 is higher than the control group (p < 0.05, ANOVA, Tukey). At 7 days, in the central part of the defect, VEGF expression was the same for all groups, OC was higher for protocol 2, and OP for protocol 1. The results suggest LLLT using the protocol 2 hastened the bone healing process in the early periods after surgery.

Subcutaneous tissue reaction and cytotoxicity of polyvinylidene fluoride and polyvinylidene fluoride-trifluoroethylene blends associated with natural polymers.

Cytotoxicity and subcutaneous tissue reaction of innovative blends composed by polyvinylidene fluoride and polyvinylidene fluoride-trifluoroethylene associated with natural polymers (natural rubber and native starch) forming membranes were evaluated, aiming its applications associated with bone regeneration. Cytotoxicity was evaluated in mouse fibroblasts culture cells (NIH3T3) using trypan blue staining. Tissue response was in vivo evaluated by subcutaneous implantation of materials in rats, taking into account the presence of necrosis and connective tissue capsule around implanted materials after 7, 14, 21, 28, 35, 60, and 100 days of surgery. The pattern of inflammation was evaluated by histomorphometry of the inflammatory cells. Chemical and morphological changes of implanted materials after 60 and 100 days were evaluated by Fourier transform infrared (FTIR) absorption spectroscopy and scanning electron microscopy (SEM) images. Cytotoxicity tests indicated a good tolerance of the cells to the biomaterial. The in vivo tissue response of all studied materials showed normal inflammatory pattern, characterized by a reduction of polymorphonuclear leukocytes and an increase in mononuclear leukocytes over the time (p < 0.05 Kruskal-Wallis). On day 60, microscopic analysis showed regression of the chronic inflammatory process around all materials. FTIR showed no changes in chemical composition of materials due to implantation, whereas SEM demonstrated the delivery of starch in the medium. Therefore, the results of the tests performed in vitro and in vivo show that the innovative blends can further be used as biomaterials.