Synthetic Polyisoprene Rubber as a Mimic of Natural Rubber: Recent Advances on Synthesis, Nanocomposites, and Applications.

Up to now, rubber materials have been used in a wide range of applications, from automotive parts to special-design engineering pieces, as well as in the pharmaceutical, food, electronics, and military industries, among others. Since the discovery of the vulcanization of natural rubber (NR) in 1838, the continuous demand for this material has intensified the quest for a synthetic substitute with similar properties. In this regard, synthetic polyisoprene rubber (IR) emerged as an attractive alternative. However, despite the efforts made, some properties of natural rubber have been difficult to match (i.e., superior mechanical properties) due not only to its high content of cis-1,4-polyisoprene but also because its structure is considered a naturally occurring nanocomposite. In this sense, cutting-edge research has proposed the synthesis of nanocomposites with synthetic rubber, obtaining the same properties as natural rubber. This review focuses on the synthesis, structure, and properties of natural and synthetic rubber, with a special interest in the synthesis of IR nanocomposites, giving the reader a comprehensive reference on how to achieve a mimic of NR.

Gordonia sp. BSTG01 isolated from Hevea brasiliensis plantation efficiently degrades polyisoprene (rubber).

Polyisoprene is the principal constituent of rubber latex which has been estimated globally as one of the major solid wastes. Bacterial bioremediation of this solid waste remains a major point of interest for scientists. This study reports a Gram-positive, non-motile, non-spore-forming actinomycete Gordonia sp. BSTG01, isolated from the bark of Hevea brasiliensis of a rubber plantation garden can considerably degrade natural rubber (NR) and synthetic polyisoprene rubber (SR). Scanning electron microscopy showed adhesive colonization of strain BSTG01 on both natural and synthetic rubber surface, conflating into the rubber and forming a biofilm. Rubber-dependent growth of the strain was examined by the decrease of rubber mass and increase of its total protein content in a time-dependent manner. Degradation was also verified by Schiff's reagent which confirms the appearance of aldehydes in the culture media. Fourier transform infrared spectroscopy including the attenuated total reflectance with the NR and SR pieces overgrown by the isolate revealed variations of the overall chemicals arising on the polyisoprene backbone due to the degradation of rubber by the strain BSTG01. Isolate BSTG01 (MTCC 13159) is a strain of Gordonia and this is the first strain isolated from unexplored rubber plantation area with considerable rubber degradation properties. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-03063-5.

Natural Membrane Differentiates Human Adipose-Derived Mesenchymal Stem Cells to Neurospheres by Mechanotransduction Related to YAP and AMOT Proteins.

Adipose tissue-derived mesenchymal stem cells (ADMSCs) are promising candidates for regenerative medicine, as they have good cell yield and can differentiate into several cell lines. When induced to the neuronal differentiation, they form neurospheres composed of neural precursors (NPs) that can be an alternative in treating neurodegenerative diseases. This study aimed to characterize NPs from neurospheres obtained after seeding ADMSCs on a natural polyisoprene-based membrane. The ADMSCs were isolated from adipose tissue by enzymatic dissociation, were subjected to trilineage differentiation, and were characterized by flow cytometry for specific ADMSC surface markers. For neuronal differentiation, the cells were seeded on polystyrene flasks coated with the membrane and were characterized by immunocytochemistry and RT-PCR. The results demonstrated that the isolated cells showed characteristics of ADMSCs. At 15 to 25 days, ADMSCs seeded on the natural membrane developed neurospheres. Then, after dissociation, the cells demonstrated characteristic neuronal markers expressed on NPs: nestin, ß-III tubulin, GFAP, NeuN, and the YAP1/AMOT in the cytoplasm. In conclusion, it was demonstrated that this membrane differentiates the ADMSCs to NPs without any induction factors, and suggests that their differentiation mechanisms are related to mechanotransduction regulated by the YAP and AMOT proteins.

Guayule (Parthenium argentatum A. Gray), a Renewable Resource for Natural Polyisoprene and Resin: Composition, Processes and Applications.

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.

First report of cis-1,4-polyisoprene degradation by Gordonia paraffinivorans.

The use of rubber has increased over the years, leading to a series of environmental problems due to its indefinite decomposition time. Bioremediation employing microorganisms have drawn an increasing interest and originated several studies of microbial rubber degradation. Genome sequencing and in silico analysis demonstrated that G. paraffinivorans MTZ041 isolate encodes the lcp gene (Latex Clearing Protein), responsible for expressing an enzyme that performs the first step in the assimilation of synthetic and natural rubber. Growth curves and scanning electron microscopy (SEM) were conducted for MTZ041 in natural (NR) and synthetic rubber (IR) as sole carbon source during 11 weeks. After 80 days, robust growth was observed and SEM analysis revealed the presence of bacilli and the formation of biofilm-like structures on natural and synthetic rubber. This is the first report of a G. paraffinivorans rubber degrader. Given the complexity of this substrate and the relative small number of microorganisms with this ability, the description and characterization of MTZ041 is of great importance on bioremediation processes of rubber products.

Improving bone cement toughness and contrast agent confinement by using acrylic branched polymers.

A new biomedical material to be used as part of acrylic bone cement formulations is described. This new material is tough, its Young's Modulus is similar to the one of poly (methylmethacrylate) and the contrast agent, usually employed in acrylic bone cements, is homogeneously distributed among the polymeric matrix. Additionally, its wear coefficient is 66% lower than the one measured in poly(methyl methacrylate). The developed material is a branched polymer with polyisoprene backbone and poly(methyl methacrylate) side chains, which are capable of retaining barium sulphate nanoparticles thus avoiding their aggregation. The grafting reaction was carried out in presence of the nanoparticles, using methyl methacrylate as solvent. From the (1)H-NMR spectra it was possible to determine the average number of MMA units per unit of isoprene (3.75:1). The ability to retain nanoparticles (about 8wt.%), attributed to their interaction with the polymer branches, was determined by thermogravimetric analysis and confirmed by FTIR and microscopy techniques. By SEM microscopy it was also possible to determine the homogeneous spatial distribution of the barium sulphate nanoparticles along the polymer matrix.

Micro-organisms in latex and natural rubber coagula of Hevea brasiliensis and their impact on rubber composition, structure and properties.

Natural rubber, produced by coagulation of the latex from the tree Hevea brasiliensis, is an important biopolymer used in many applications for its outstanding properties. Besides polyisoprene, latex is rich in many nonisoprene components such as carbohydrates, proteins and lipids and thereby constitutes a favourable medium for the development of micro-organisms. The fresh rubber coagula obtained by latex coagulation are not immediately processed, allowing the development of various microbial communities. The time period between tree tapping and coagula processing is called maturation, during which an evolution of the properties of the corresponding dry natural rubber occurs. This evolution is partly related to the activity of micro-organisms and to the modification of the biochemical composition. This review synthesizes the current knowledge on microbial populations in latex and natural rubber coagula of H. brasiliensis and the changes they induce on the biochemistry and technical properties of natural rubber during maturation.

Clinical relevance of trans 1.4-polyisoprene aging degradation on the longevity of root canal treatment

This in vivo study investigated the time of degradation of root filling material (trans 1,4-polyisoprene) retrieved from endodontically treated teeth and correlated the occurrence of degradation with the longevity of endodontics. Thirty-six root-filled teeth with different filling times (2 to 30 years) and with and without periapical lesions were selected. All teeth presented clinical indication for root canal retreatment. The association among filling time, presence of periapical lesion and root filling material degradation was investigated. Root filling samples were retrieved from the root canals using a Hedströ m file without solvent. The trans 1,4-polyisoprene was isolated by root filling solubilization in chloroform followed by filtration and centrifugation. GPC and FT-IR were the analytical techniques utilized. Degradation of trans 1,4-polyisoprene occurred with time, as a slow process. It is an oxidative process, and production of carboxyl and hydroxyl groups in the residual polymer were observed. Statistically significant decrease of molar mass was observed after 5 (p=0.0001) and 15 (p=0.01) years in teeth with and without periapical lesion, respectively. Bacteria participated in polymer degradation. Gutta-percha aging was proven an important factor for the long-term success of endodontic treatment. The findings of the present study showed that, after 15 years, polymer weight loss may decrease the capacity of the filling mass to seal the root canal space and prevent re-infection, thus compromising significantly the longevity of root canal therapy.

Este estudo in vivo avaliou a degradação do material obturador e a influência deste fator na longevidade do tratamento endodôntico. Foram selecionados 36 pacientes (3-30 anos) com canais tratados endodonticamente, com e sem lesões periapicais, e indicação de retratamento endodôntico. Foi investigada a associação entre o tempo de tratamento, presença de lesão periapical e a degradação do material obturador. O material obturador foi removido com uma lima Hedströ em sem uso de solvente. O polímero trans 1,4- poliisopreno foi isolado do material obturador através de solubilização em clorofórmio, seguido de filtragem e centrifugação. GPC e FT-IR foram os métodos analíticos utilizados. A degradação do trans 1,4- poliisopreno foi observada com o tempo, sendo um processo lento e oxidativo, com formação de grupos carboxílicos e hidroxilas no polímero residual. Após 5 (p=0,0001) e 15 (p=0,01) anos, em dentes com e sem lesões periapicais, respectivamente, houve decréscimos significantes na massa molar do material obturador. A infecção bacteriana participa no processo de degradação do polímero. O envelhecimento da guta-percha é um fator que influencia o sucesso a longo prazo do tratamento endodôntico. Após 15 anos, a longevidade do tratamento pode ser significantemente afetada pela redução da capacidade de selamento causada pela perda de massa molar do polímero, permitindo a reinfecção do sistema de canais radiculares.

Contribution to the study of Himatanthus sucuuba: latex macromolecule, microelements and carbohydrates

The polymeric material in the latex of Himatanthus sucuuba (Spruce) Woodson was identified by spectroscopic methods as cis-polyisoprene (Mn = 192; Mw = 571; Mw/ Mn = 2.97). ICP-MS analysis of microelements in the aqueous phase showed the most abundant to be Ca (354 g/g) and Mg (250 g/g). Carbohydrate analysis of the aqueous phase by HPLC-PAD showed arabinose, glucose, xylose, rhamnose and galactose to be the predominant saccharides.

O polímero do látex de Himatanthus sucuuba (Spruce) Woodson foi identificado por métodos espectroscópicos como o cis-poliisopreno (Mn = 192; Mw = 571; Mw /Mn= 2.97). A análise de microelementos na fase aquosa por ICP-MS forneceu Ca (354 mg/g) e Mg (259 mg/g) como elementos majoritários. A detecção de carboidratos na fase aquosa por CLAE-DPA apresentou arabinose, glucose, xilose, ramnose e galactose como açúcares principais.

Contribution to the study of Himatanthus sucuuba: latex macromolecule, microelements and carbohydrates

The polymeric material in the latex of Himatanthus sucuuba (Spruce) Woodson was identified by spectroscopic methods as cis-polyisoprene (Mn = 192; Mw = 571; Mw/ Mn = 2.97). ICP-MS analysis of microelements in the aqueous phase showed the most abundant to be Ca (354 g/g) and Mg (250 g/g). Carbohydrate analysis of the aqueous phase by HPLC-PAD showed arabinose, glucose, xylose, rhamnose and galactose to be the predominant saccharides.

O polímero do látex de Himatanthus sucuuba (Spruce) Woodson foi identificado por métodos espectroscópicos como o cis-poliisopreno (Mn = 192; Mw = 571; Mw /Mn= 2.97). A análise de microelementos na fase aquosa por ICP-MS forneceu Ca (354 mg/g) e Mg (259 mg/g) como elementos majoritários. A detecção de carboidratos na fase aquosa por CLAE-DPA apresentou arabinose, glucose, xilose, ramnose e galactose como açúcares principais.