RESUMO
The blend of butadiene and acrylonitrile copolymer (NBR) with natural poly-cis-isoprene (NR) shows increased resistance to swelling in solvents in comparison to the individual components. In aerospace, NBR rubber is used as thermal protection for rockets and shall not contain other polymers, even in low contents, otherwise, it can affect the protection performance and rocket safety by causing detachment of the elastomer/propellant interface; therefore, this investigation presents methodologies to determine the NR/NBR contents. This study explores different analytical techniques, such as Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy, in the mid-infrared (MIR) by reflection and in the near-infrared by reflectance (NIRA) modes, Furthermore, quantification strategies by univariate, bivariate and multivariate (chemometric) models are evaluated and compared. A proposed methodology, based on multivariate Raman microscopy with partial least squares regression (PLS), showed high linearity (R2 > 0.99) and low error (< 0.82 %). The validation of FT-MIR data for the CH3, which presented lower error (1.3%) than vinylidene band (6%), showed that both methodologies (reflection and NIRA reflectance) can be used for the quantification of NR in NR/NBR. These results constitute a contribution to the state of the art in researching industrial and aerospace elastomeric applications.
Assuntos
Borracha , Análise Espectral Raman , Análise Espectral Raman/métodos , Borracha/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Butadienos/química , Butadienos/análiseRESUMO
PURPOSE: To evaluate the effect of different finishing and polishing systems on the surface roughness of a resin composite subjected to simulated saliva-, acid-, and enzyme-induced degradation. METHODS: 160 specimens (n= 40) were fabricated with Filtek Z350 XT nanofilled composite and analyzed for average surface roughness (Ra). The specimens were finished and polished using: AD - Al2O3-impreginated rubberized discs (medium, fine, and superfine grit, Sof-Lex); SD - silicon carbide and Al2O3-impregnated rubberized discs (coarse, medium and fine grit, Jiffy,); MB - 12- and 30-multiblade burs. The control group (CT) (n= 40) comprised specimens with a Mylar-strip-created surface. Specimens from each group were immersed in 1 mL of one of the degradation methods (n= 10): artificial saliva (ArS: pH 6.75), cariogenic challenge (CaC: pH 4.3), erosive challenge (ErC: 0.05M citric acid, pH 2.3) or enzymatic challenge (EzC: artificial saliva with 700 µg/mL of albumin, pH 6.75). The immersion period simulated a time frame of 180 days. Ra measurements were also performed at the post-polishing and post-degradation time points. The data were evaluated by three-way ANOVA for repeated measures and the Tukey tests. RESULTS: There was significant interaction between the finishing/polishing system and the degradation method (P= 0.001). AD presented the greatest smoothness, followed by SD. After degradation, CT, AD and SD groups became significantly rougher, but not the MB group, which presented no difference in roughness before or after degradation. CT and AD groups showed greater roughness in CaC, ErC and EzC than in ArS. The SD group showed no difference in roughness when the specimens were polished with CaC, EzC or ArS, but those treated with ErC had greater roughness. In the MB group, the lower roughness values were found after using CaC and EzC, while the higher values were found using ErC or ArS. CLINICAL SIGNIFICANCE: As far as degradation resistance of nanofilled composite to hydrolysis, bacterial and dietary acids and enzymatic reactions is concerned, restorations that had been finished and polished with Al2O3-impregnated discs had the smoothest surfaces.
Assuntos
Óxido de Alumínio , Resinas Compostas , Polimento Dentário , Saliva Artificial , Compostos de Silício , Propriedades de Superfície , Resinas Compostas/química , Polimento Dentário/métodos , Humanos , Saliva Artificial/química , Concentração de Íons de Hidrogênio , Óxido de Alumínio/química , Compostos de Silício/química , Compostos Inorgânicos de Carbono/química , Teste de Materiais , Nanocompostos/química , Ácido Cítrico/química , Saliva/enzimologia , Saliva/metabolismo , Saliva/química , Erosão Dentária , Borracha/química , Materiais Dentários/químicaRESUMO
Natural Rubber Latex (NRL) has shown to be a promising biomaterial for use as a drug delivery system to release various bioactive compounds. It is cost-effective, easy to handle, biocompatible, and exhibits pro-angiogenic and pro-healing properties for both soft and hard tissues. NRL releases compounds following burst and sustained release kinetics, exhibiting first-order release kinetics. Moreover, its pore density can be adjusted for tailored kinetics profiles. In addition, biotechnological applications of NRL in amblyopia, smart mattresses, and neovaginoplasty have demonstrated success. This comprehensive review explores NRL's diverse applications in biotechnology and biomedicine, addressing challenges in translating research into clinical practice. Organized into eight sections, the review emphasizes NRL's potential in wound healing, drug delivery, and metallic nanoparticle synthesis. It also addresses the challenges in enhancing NRL's physical properties and discusses its interactions with the human immune system. Furthermore, examines NRL's potential in creating wearable medical devices and biosensors for neurological disorders. To fully explore NRL's potential in addressing important medical conditions, we emphasize throughout this review the importance of interdisciplinary research and collaboration. In conclusion, this review advances our understanding of NRL's role in biomedical and biotechnological applications, offering insights into its diverse applications and promising opportunities for future development.
Assuntos
Materiais Biocompatíveis , Sistemas de Liberação de Medicamentos , Látex , Medicina Regenerativa , Borracha , Humanos , Materiais Biocompatíveis/química , Látex/química , Medicina Regenerativa/métodos , Borracha/química , Cicatrização/efeitos dos fármacosRESUMO
Natural rubber (NR), derived from Hevea brasiliensis, has properties for biomedical applications. Several studies indicate that these properties can be amplified when we associate another bioproduct. However, there are no studies of aging aspects of this biomaterial regarding changes in functionality, structure and composition. The objective was to evaluate the aging process of natural rubber membranes - copaiba (NRC) subjected to controlled conditions of time, light and presence of oxygen. The NRC was prepared and stored in the presence or absence of light and vacuum, for periods of 30, 60 and 90 days. Subsequently, the membranes were characterized through the techniques of wettability, infrared spectroscopy, thermal analysis, scanning microscopy and antioxidant activity. The wettability analysis, showed that NRC membranes both in the zero time and in the aging time were hydrophilic. Through thermogravimetric analysis and differential exploratory analysis the membranes remained thermally stable. The scanning electronic microscopy, indicated no morphological alterations during the observed period. After 90 days, the packaged membranes showed satisfactory antioxidant activity. Our results suggest that the membranes were resistant to the storage period, since they maintained their chemical, thermal, morphological and antioxidant characteristics. Hence, it corroborates to use of membranes as a possible curative for biomedical applications.
Assuntos
Hevea , Borracha , Borracha/química , Látex/química , Antioxidantes/farmacologia , Extratos Vegetais , Proteínas de Plantas/químicaRESUMO
Gold nanoparticles (AuNPs) have shown interesting properties and specific biofunctions, providing benefits and new opportunities for controlled release systems. In this research, we demonstrated the use of natural rubber latex (NRL) from Hevea brasiliensis as a carrier of AuNPs and the antibiotic metronidazole (MET). We prepared AuNP-MET-NRL and characterized by physicochemical, biological and in vitro release assays. The effect of AuNPs on MET release was evaluated using UV-Vis and Laser-Induced Breakdown Spectroscopy (LIBS) techniques. AuNPs synthesized by Turkevich and Frens method resulted in a spherical shape with diameters of 34.8 ± 5.5 nm. We verified that there was no emergence or disappearance of new vibrational bands. Qualitatively and quantitatively, we showed that the MET crystals dispersed throughout the NRL. The Young's modulus and elongation values at dressing rupture were in the range appropriate for human skin application. 64.70% of the AuNP-MET complex was released within 100 h, exhibiting a second-order exponential release profile. The LIBS technique allowed monitoring of the AuNP release, indicating the Au emission peak reduction at 267.57 nm over time. Moreover, the dressing displayed an excellent hemocompatibility and fibroblast cell viability. These results demonstrated that the AuNP-MET-NRL wound dressing is a promising approach for dermal applications.
Assuntos
Ouro , Látex , Nanopartículas Metálicas , Metronidazol , Bandagens , Ouro/química , Humanos , Látex/química , Nanopartículas Metálicas/química , Metronidazol/farmacologia , Borracha/químicaRESUMO
Natural rubber is an essential material, especially for plane and truck tyres but also for medical gloves. Asia ranks first in the production of natural rubber, of which the Hevea tree is currently the sole source. However, it is anticipated that this source alone will not be able to fulfill the growing demand. Guayule, a shrub native to northern Mexico and southern United States, may also contribute. This plant not only contains polyisoprene, but also resin, a mixture of lipids and terpenoids. This review summarizes various aspects of this plant, from the usage history, botanical description, geographical distribution and cultivation practices, down to polyisoprene and resin biosynthesis including their distribution within the plant and molecular composition. Finally, the main processes yielding dry rubber or latex are depicted, as well as the properties of the various extracts along with economic considerations. The aim is to provide a wide picture of current knowledge available about this promising crop, a good feedstock candidate for a multiple-product biorefinery.
Assuntos
Asteraceae/química , Resinas Vegetais/química , Animais , Ásia , Humanos , Látex/química , México , Borracha/química , Estados UnidosRESUMO
Rubber residues present harmful impacts on health and environment, besides wasting valuable and huge amounts of rubber. Biological recycling technique is focused here to minimize this problem. A comparison of the biodegradation effect caused by Bacillus subtilis, Pseudomonas aeruginosa, and Streptomyces sp., separately, on vulcanized SBR-rubber during 4 weeks is reported. The surface and molecular analyses were studied by FTIR-ATR, TGA, DSC, TC and SEM/EDS, in addition to the contact angle and crosslinking tests. B. subtilis, P. aeruginosa, and Streptomyces sp. evoked after 4 weeks a loss in v-SBR crosslinks by 17.15, 10.68 and 43.39% and also in the contact angle with water by 14.10, 12.86 and 15.71%, respectively., if compared to Control samples. FTIR findings indicate that the polymeric chain has been partially consumed causing C-C bonds scission indicating the biodegradation and bio-devulcanization phenomena. The bacterial strains caused a carbon loss by 9.15, 5.97 and 4.55% after one week and 16.09, 16.79 and 18.13% after four weeks for B. subtilis, P. aeruginosa, and Streptomyces sp. mediums, respectively. DSC and EDS results are also promising and highlighting Streptomyces sp. strain as the most effective biodegradative one as an alternative and natural mean of degrading vulcanized rubber residues.
Assuntos
Bacillus subtilis/metabolismo , Biodegradação Ambiental , Pseudomonas aeruginosa/metabolismo , Borracha/metabolismo , Humanos , Látex/química , Látex/metabolismo , Reciclagem , Borracha/química , Streptomyces/metabolismoRESUMO
The shear wave dispersion magneto-motive ultrasound (SDMMUS) method was recently developed to analyze the mechanical properties of a viscoelastic medium. This technique is based on the interaction of magnetic nanoparticles (MNPs) with an external magnetic field to generate a shear wave within the medium labeled with MNPs. The propagation of this wave provides information about the viscoelastic properties of the medium. In a previous work by Arsalani et al (2018), magnetite NPs were synthesized by a co-precipitation method and coated with natural rubber latex (NRL). In order to investigate the effect of NRL on the size and magnetization of MNPs, varying amounts of NRL (zero, 100 µl, and 800 µl of a stock solution of NRL) were used during the synthesis process. The results showed that MNPs prepared with 800 µl of NRL, named as MNPs-800NRL, had the smallest size and highest magnetization. In the present paper, the main objective is to investigate whether MNPs-800NRL, having the highest magnetization, is also the best option for SDMMUS experiments among others. All experiments were performed using gelatin tissue-mimicking phantoms labeled with the aforementioned MNPs. The two factors of core size and magnetization were considered, and based on the observed results, the effect of magnetization was more prominent than that of the core size on the induced displacements. MNPs coated with a thicker NRL shell, having the highest magnetization value, enhanced the sensitivity and the signal to noise ratio in SDMMUS. Various concentrations of these optimized MNPs were also examined, to investigate the lowest possible concentration for observing shear waves in the SDMMUS technique.
Assuntos
Látex/química , Fenômenos Magnéticos , Nanopartículas de Magnetita/química , Borracha/química , Ondas Ultrassônicas , GelatinaRESUMO
Natural rubber latex (NRL) is a natural polymer which has arisen large interest in the biomedical field, mostly, due to its ability to facilitate angiogenesis and therefore, tissue repair. Moxifloxacin (MXF) is a broad-spectrum antibiotic orally administrated. Considering the biological properties of the NRL and its ability to deliver a wide range of compounds, the present study aimed to develop a novel device for infected chronic wound treatment. MXF-loaded NRL was obtained by a casting method. The results demonstrated that the incorporation of MXF in NRL did not promote any molecular interaction, preserving the integrity of the compounds. The mechanical properties of the biomaterial did not show any significant change, indicating enough elasticity for dermal application. The microbiological assays confirmed the ability of the polymer to deliver the drug without influencing its pharmacological properties. Moreover, it has expressed activity against major bacterial strains presented in wound infections. Finally, the biomaterial shown biocompatibility from the in vitro study. Thus, the present work has shown that MXF-loaded NRL membrane is a promising biomaterial to infected wound treatment.
Assuntos
Bandagens , Sistemas de Liberação de Medicamentos/instrumentação , Moxifloxacina/farmacologia , Polímeros/química , Infecção dos Ferimentos/terapia , Animais , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Linhagem Celular , Escherichia coli/efeitos dos fármacos , Fibroblastos/microbiologia , Humanos , Queratinócitos/microbiologia , Látex/química , Camundongos , Testes de Sensibilidade Microbiana , Pseudomonas aeruginosa/efeitos dos fármacos , Borracha/química , CicatrizaçãoRESUMO
Our aim was to evaluate effects of natural rubber membrane (NR) associated with aqueous propolis extract (P) on the wound healing in rats burn model. The membranes were characterized for wettability and pore presence after the membrane preparation by casting the liquid solution in Petri dishes, at different temperatures (27 and 60⯰C). Male Wistar rats were divided into treatment groups (nâ¯=â¯5 per group: control without treatment, silver sulfadiazine, NR, NRP) initiated immediately after second-degree burn and maintained during 10â¯days. The NRP membranes presented hydrophilic and porous characteristics. Macroscopic analysis from lesions showed that all groups presented crust formation. At the end of the experiment, the lesions treated with NRP membranes prepared at 60⯰C had a higher regression percentage indicating a faster wound healing. The biopsies showed that the treatment with the NRP membranes induced a wound healing with collagen production, angiogenesis, reepithelization, and a small number of inflammatory cells, characterized by the crust detachment and the epithelium formation. In conclusion, NRP membranes are promising as a dressing for the burns treatment since were able to accelerate the healing process and tissue repair without the curative switch.