Weathering Resistance of Waterborne Polyurethane Coatings Reinforced with Silica from Rice Husk Ash.

Waterborne polyurethanes (WPUs) are interesting materials for coatings when compared to solvent-based polyurethanes, once that reducing the concentration of volatile organic compounds that are harmful for human health and the environment. However, the WPU has low weathering resistance. In order to improve this behavior among others properties, inorganic fillers has been added in these systems. SiO2 particles from various sources, mainly, from agro-industrial waste, as rice husk has attracted the scientific and technological interest. In this study, the accelerated weathering essay was performed in waterborne polyurethane (WPU)/ silica (from rice husk ash) composites in order to evaluate the thermal and physical changes in these materials. These composites were prepared by two distinct methods: in situ polymerization and blending method. The highest resistance to thermal degradation and to accelerated weathering was reached with WPU/silica composites obtained by blending method due the interactions between SiO2 particles and the polymer matrices. Blending method for preparation WPU/silica composites proved to be a simpler and faster method, with no drawback for large scale application.

Preclinical evaluation of the functionality of a polymer-coated sirolimuseluting stent in pigs.

PURPOSE: To compare the endothelial coverage of different stents in porcine carotid arteries. Research problem: How effective are polyurethane stents (PU) and PU + rapamycin (PU + RAPA) compared to bare-metal stents on endothelial coverage by neointima in pigs after 28 days? METHODS: The methodology had two phases for an interventional, experimental, prospective study, with three Moura pigs, 12 weeks old and weighing between 19 and 22.5 kg. In phase I, eight stents were implanted in carotid arteries; three stents coated with PU, three coated with PU + RAPA, and two without coating. After 28 days, phase II was carried out, consisting of euthanasia, removal of the stents, to evaluate the exposed area of the stent struts, and the percentage of endothelialization through optical microscopy and scanning electron microscopy. RESULTS: The eight stents implanted with ultrasound sizing and post-dilation with a larger diameter balloon were analyzed by Doppler ultrasound, intravascular ultrasound, and angiography after 28 days. CONCLUSIONS: This study showed complete endothelial coverage by the endoluminal neointima of the stent struts, good integration and coverage with the arterial wall, with no exposed struts showing the presence of intimal hyperplasia (whitish tissue).

Zinc-Modified Titanate Nanotubes as Radiosensitizers for Glioblastoma: Enhancing Radiotherapy Efficacy and Monte Carlo Simulations.

Radiotherapy (RT) is the established noninvasive treatment for glioblastoma (GBM), a highly aggressive malignancy. However, its effectiveness in improving patient survival remains limited due to the radioresistant nature of GBM. Metal-based nanostructures have emerged as promising strategies to enhance RT efficacy. Among them, titanate nanotubes (TNTs) have gained significant attention due to their biocompatibility and cost-effectiveness. This study aimed to synthesize zinc-modified TNTs (ZnTNT) from sodium TNTs (NaTNT), in addition to characterizing the formed nanostructures and evaluating their radiosensitization effects in GBM cells (U87 and U251). Hydrothermal synthesis was employed to fabricate the TNTs, which were characterized using various techniques, including transmission electron microscopy (TEM), energy-dispersive spectroscopy, scanning-transmission mode, Fourier-transform infrared spectroscopy, ICP-MS (inductively coupled plasma mass spectrometry), X-ray photoelectron spectroscopy, and zeta potential analysis. Cytotoxicity was evaluated in healthy (Vero) and GBM (U87 and U251) cells by the MTT assay, while the internalization of TNTs was observed through TEM imaging and ICP-MS. The radiosensitivity of ZnTNT and NaTNT combined with 5 Gy was evaluated using clonogenic assays. Monte Carlo simulations using the MCNP6.2 code were performed to determine the deposited dose in the culture medium for RT scenarios involving TNT clusters and cells. The results demonstrated differences in the dose deposition values between the scenarios with and without TNTs. The study revealed that ZnTNT interfered with clonogenic integrity, suggesting its potential as a powerful tool for GBM treatment.

Micro- and nanoplastic toxicity: A review on size, type, source, and test-organism implications.

Polymeric wastes are among the current major environmental problems due to potential pollution and contamination. Within the spectrum of polymeric waste, microplastics (MPs) and nanoplastics (NPs) have gained ground in recent research since these particles can affect the local biota, inducing toxic effects on several organisms. Different outcomes have been reported depending on particle sizes, shape, types, and exposed organisms and conditions, among other variables. This review aimed to compile and discuss the current knowledge and possible literature gaps regarding the MPs and NPs generation and their toxicological effects as stressors, considering polymer type (as polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polyvinyl chloride, or others), size (micro- or nano-scale), source (commercial, lab-synthesized, or environmental) and test organism group. In that sense, 615 publications were analyzed, among which 72 % discussed micro-sized plastics, while <28 % assayed the toxicity of NPs (<1 µm). For most polymers, MPs and NPs were commercially purchased and used without additional size reduction processes; except for polyethylene terephthalate studies that mostly used grinding and cutting methods to obtain MPs. Polystyrene (PS) was the main polymer studied, as both MPs and NPs. PS accounts for >90 % of NPs reports evaluated, reflecting a major literature gap if compared to its 35.3 % share on MPs studies. Among the main organisms, arthropods and fish combined accounted for nearly 40 % of toxicity testing. Overall, the different types of plastics showed a tendency to report toxic effects, except for the 'Survival/lethality' category, which might indicate that polymeric particles induce mostly sublethal toxic effects. Furthermore, despite differences in publication numbers, we observed greater toxicity reported for NPs than MPs with oxidative stress among the majorly investigated endpoints. This study allowed a hazard profile overview of micro/nanoplastics (MNPs) and the visualization of literature gaps, under a broad diversity of toxicological evidence.

Hydrocarbon-based plastics: Progress and perspectives on consumption and biodegradation by insect larvae.

The obvious contrast between the remarkable durability and the high consumption of plastic products leads to the deposition of at least 100 million tons of plastics per year in nature. Since 2010, several studies have shown the potential of insect larvae to biodegrade different types of plastics, at higher rates than those reported for microorganisms. This review discusses a compilation of studies about the consumption and biodegradation of hydrocarbon-based plastics, particularly PE, PS, PP and PVC, by lepidopteran and coleopteran larvae. Insects of the Coleoptera order seem to have a better adaptation for PS biodegradation, while those of the Lepidoptera order can better biodegrade PE. Tenebrio molitor biomineralize PE and PS into CO2, and PVC into HCl; while Tenebrio obscurus and Zophobas atratus converts PE and PS into CO2, respectively. Plastic biodegradation by T. molitor has been shown to be dependent on microbiota, exception for PE. Similar PS and PE biodegradation profile has been shown for T. obscurus. PS, PP and PE biodegradation by Z. atratus is also reported to be microbial-dependent. For Galleria mellonella, microbial role on PE biodegradation is still controversial, but the PS metabolism was proved to be microbiota-independent. Advances in this field has stimulated new studies with other insect species, which need to be better explored. Uncovering and understanding the chemical processes behind the innate plastic biodegradation by insect larvae will open the perspective to new eco-friendly innovative biotechnological solutions for the challenge of plastic waste.

Chitosan and chitosan/PEG nanoparticles loaded with indole-3-carbinol: Characterization, computational study and potential effect on human bladder cancer cells.

Indole-3-carbinol (I3C) is a plant molecule known to be active against several types of cancer, but some chemical characteristics limit its clinical applications. In order to overcome these limitations, polymeric nanoparticles can be used as carrier systems for targeted delivery of I3C. In this study, chitosan and chitosan/polyethylene glycol nanoparticles (CS NP and CS/PEG NP, respectively) were prepared to encapsulate I3C by ionic gelation method. The polymeric nanoparticles were characterized by Dynamic Scattering Light (DLS), Zeta Potential (ZP), Fourier Transform Infrared (FTIR) spetroscopy, X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). I3C release testing was performed at an acidic media and the interactions between I3C and chitosan or PEG were evaluated by Density Functional Theory (DFT). Cytotoxicity of nanoparticles in bladder cancer T24 cell line was evaluated by the Methyl-thiazolyl-tetrazolium (MTT) colorimetric assay. The average size of the nanoparticles was observed to be in the range from 133.3 ± 3.7 nm to 180.4 ± 2.7 nm with a relatively homogeneous distribution. Samples had relatively high positive zeta potential values (between +20.3 ± 0.5 mV and + 24.3 ± 0.5 mV). Similar encapsulation efficiencies (about 80%) for both nanoparticles were obtained. Physicochemical and thermal characterizations pointed to the encapsulation of I3c. electron microscopy showed spherical particles with smooth or ragged surface characteristics, depending on the presence of PEG. The mathematical fitting of the release profile demonstrated that I3C-CS NP followed the Higuchi model whereas I3C-CS/PEG NP the Korsmeyer-Peppas model. Chemical differences between the nanoparticles as based on the I3C/CS or I3C/PEG interactions were demonstrate by computational characterization. The assessment of cell viability by the MTT test showed that the presence of both free I3C and I3C-loaded nanoparticles lead to statistically significant reduction in T24 cells viability in the concentrations from 500 to 2000 µM, when comparison to the control group after 24 h of exposure. Thus, CS and CS/PEG nanoparticles present as feasible I3C carrier systems for cancer therapy.

Hyaluronic acid-coated chitosan nanoparticles as carrier for the enzyme/prodrug complex based on horseradish peroxidase/indole-3-acetic acid: Characterization and potential therapeutic for bladder cancer cells.

Hybrid nanoparticles composed of different biopolymers for delivery of enzyme/prodrug systems are of interest for cancer therapy. Hyaluronic acid-coated chitosan nanoparticles (CS/HA NP) were prepared to encapsulate individually an enzyme/pro-drug complex based on horseradish peroxidase (HRP) and indole-3-acetic acid (IAA). CS/HA NP showed size around 158 nm and increase to 170 and 200 nm after IAA and HRP encapsulation, respectively. Nanoparticles showed positive zeta potential values (between +20.36 mV and +24.40 mV) and higher encapsulation efficiencies for both nanoparticles (up to 90 %) were obtained. Electron microscopy indicated the formation of spherical particles with smooth surface characteristic. Physicochemical and thermal characterizations suggest the encapsulation of HRP and IAA. Kinetic parameters for encapsulated HRP were similar to those of the free enzyme. IAA-CS/HA NP showed a bimodal release profile of IAA with a high initial release (72 %) followed by a slow-release pattern. The combination of HRP-CS/HA NP and IAA- CS/HA NP reduced by 88 % the cell viability of human bladder carcinoma cell line (T24) in the concentrations 0.5 mM of pro-drug and 1.2 µg/mL of the enzyme after 24 h.

Comparison of 2D and 3D cell culture models for cell growth, gene expression and drug resistance.

In vitro drug screening is widely used in the development of new drugs, because they constitute a cost-effective approach to select compounds with more potential for therapy. They are also an attractive alternative to in vivo testing. However, most of these assays are done in two-dimensional culture models, where cells are grown on a polystyrene or glass flat surface. In order to develop in vitro models that would more closely resemble physiological conditions, three-dimensional models have been developed. Here, we introduce two novel fully synthetic scaffolds produced using the polymer polyhydroxybutyrate (PHB): a Solvent-Casting Particle-Leaching (SCPL) membrane; and an electrospun membrane, to be used for 3D cultures of B16 F10 murine melanoma cells and 4T1 murine breast cancer cells. A 2D cell culture system in regular tissue culture plates and a classical 3D model where cells are grown on a commercially available gel derived from Engelbreth-Holm Swarm (EHS) tumor were used for comparison with the synthetic scaffolds. Cells were also collected from in vivo tumors grown as grafts in syngeneic mice. Morphology, cell viability, response to chemotherapy and gene expression analysis were used to compare all systems. In the electrospun membrane model, cells were grown on nanometer-scale fibers and in the SCPL membrane, which provides a foam-like structure for cell growth, pore sizes varied. Cells grown on all 3D models were able to form aggregates and spheroids, allowing for increased cell-cell contact when compared with the 2D system. Cell morphology was also more similar between 3D systems and cells collected from the in vivo tumors. Cells grown in 3D models showed an increase in resistance to dacarbazine, and cisplatin. Gene expression analysis also revealed similarities among all 3D platforms. The similarities between the two synthetic systems to the classic EHS gel model highlight their potential application as cost effective substitutes in drug screening, in which fully synthetic models could represent a step towards higher reproducibility. We conclude PHB synthetic membranes offer a valuable alternative for 3D cultures.

New quercetin-coated titanate nanotubes and their radiosensitization effect on human bladder cancer.

Interest in nanostructures such as titanate nanotubes (TNT) has grown notably in recent years due to their biocompatibility and economic viability, making them promising for application in the biomedical field. Quercetin (Qc) has shown great potential as a chemopreventive agent and has been widely studied for the treatment of diseases such as bladder cancer. Motivated by the possibilities of developing a new hybrid nanostructure with potential in biomedical applications, this study aimed to investigate the incorporation of quercetin in sodium (NaTNT) and zinc (ZnTNT) titanate nanotubes, and characterize the nanostructures formed. Qc release testing was also performed and cytotoxicity in Vero and T24 cell lines evaluated by the MTT assay. The effect of TNTs on T24 bladder cancer cell radiosensitivity was also assessed, using cell proliferation and a clonogenic assay. The TNT nanostructures were synthesized and characterized by FESEM, EDS, TEM, FTIR, XRD and TGA. The results showed that the nanostructures have a tubular structure and that the exchange of Na+ ions for Zn2+ and incorporation of quercetin did not alter this morphology. In addition, interaction between Zn and Qc increased the thermal stability of the nanostructures. The release test showed that maximum Qc delivery occurred after 24 h and the presence of Zn controlled its release. Biological assays indicated that the NaTNTQc and ZnTNTQc nanostructures decreased the viability of T24 cells after 48 h at high concentrations. Furthermore, the clonogenic assay showed that NaTNT, NaTNTQc, ZnTNT and ZnTNTQc combined with 5 Gy reduced the formation of polyclonal colonies of T24 cells after 48 h. The results suggest that the nanostructures synthesized in this study interfere in cell proliferation and can therefore be a powerful tool in the treatment of bladder cancer.

Preclinical evaluation of the functionality of a polymer-coated sirolimuseluting stent in pigs

Purpose: To compare the endothelial coverage of different stents in porcine carotid arteries. Research problem: How effective are polyurethane stents (PU) and PU + rapamycin (PU + RAPA) compared to bare-metal stents on endothelial coverage by neointima in pigs after 28 days? Methods: The methodology had two phases for an interventional, experimental, prospective study, with three Moura pigs, 12 weeks old and weighing between 19 and 22.5 kg. In phase I, eight stents were implanted in carotid arteries; three stents coated with PU, three coated with PU + RAPA, and two without coating. After 28 days, phase II was carried out, consisting of euthanasia, removal of the stents, to evaluate the exposed area of the stent struts, and the percentage of endothelialization through optical microscopy and scanning electron microscopy. Results: The eight stents implanted with ultrasound sizing and post-dilation with a larger diameter balloon were analyzed by Doppler ultrasound, intravascular ultrasound, and angiography after 28 days. Conclusions: This study showed complete endothelial coverage by the endoluminal neointima of the stent struts, good integration and coverage with the arterial wall, with no exposed struts showing the presence of intimal hyperplasia (whitish tissue).

Development and validation of analytical methodology by GC-FID using hexadecyl propanoate as an internal standard to determine the bovine tallow methyl esters content.

EN 14103:2003 and EN 14103:2011 were developed in order to determine fatty acid methyl ester (FAME) content of biodiesel. The internal standards (IS) of biodiesel include methyl heptadecanoate (MHD) and methyl nonadecanoate (MND), respectively. However, since these ISs are also present in bovine tallow methyl esters (BTME) or overlapping peaks, they have not been efficient. This work proposes an improved BTME determination method by using hexadecyl propanoate (HDP) as an IS. For this purpose, an analytical methodology by Gas Chromatography-Flame Ionization Detector (GC-FID) was developed and validated, where HDP demonstrated selectivity in retention time between peaks C16:1 and C18:0 for coconut and soybeans methyl esters and BTME, as well as resolution >1.5 for the BTME in split mode 30:1. Trueness in the determination of BTME content using the HDP as an IS was statistically equivalent to confidence interval of 95% for the null hypothesis statistic test, even when only 20% of the HDP was utilized in comparison with the IS concentrations defined by EN 14103:2003 and EN 14103:2011. This allowed the biodiesel analysis to be performed five times more with 1 g of HDP. Furthermore, the method developed enabled us to reduce the analysis time by 21.6%, without prejudice to the integration of peaks (C6:0 to C24:1). Regarding the repeatability and intermediate precision tests, results of RSD (%) ≤ 2% were reached. Additionally, the method developed has proved to be robust. HDP is a long-chain fatty alcohol ester absent from feedstocks used in biodiesel synthesis. It presents all of the characteristics for a good IS, ideal for application via internal standardization method, as recommended by EN 14103.

Chemical synthesis and in vitro biocompatibility tests of poly (L-lactic acid).

Polylactic acid is a polymer of great technological interest, whose excellent mechanical properties, thermal plasticity, and bioresorbability render it potentially useful for environmental applications, as a biodegradable plastic and as a biocompatible material in biomedicine. This article discusses the synthesis and characterization of poly-L-lactic acid, obtained through two synthetic routes: direct polycondensation reactions without organic solvents, and in a supercritical medium. Tin complexes were used as catalysts in both polymerization reactions. The polymers were characterized by (1)HNMR, IR, GPC, DSC, and TGA techniques. In vitro biocompatibility tests were performed with human alveolar bone osteoblasts and there were assessed cell adhesion, proliferation and viability. The poly condensation reaction proved to be an excellent synthetic route to produce PLA polymers with different molar mass. The formation of polymers from lactic acid monomer was confirmed through techniques utilized. It was observed that cell adhesion and viability was not disturbed by the presence of the polymer, although the proliferation rate was decreased when compared to control.

Incorporação do hormônio do crescimento humano recombinante (rhGH) em matriz de polímero biodegradável / Recombinant human growth hormone (rhGH) incorporated into biodegradable polymer scaffolds

Objetivo: Incorporar o hormônio de crescimento recombinante humano em um polímero biodegradável (PLGA). Material e método: As matrizes foram confeccionadas através da técnica de evaporação de solventes. Foi feita uma mistura do polímero (poli ácido glicólico lático) e do hormônio do crescimento humano recombinante (Saizen® Merck Serono S.A. Aubonne, Suíça). Essa mistura foi vertida em moldes de silicone circulares de 1 cm de diâmetro e aproximadamente 2 mm de espessura, e levada para secagem em uma câmara de evaporação de solvente por 48 horas. Após esse período, as matrizes foram imersas em PBS e passaram por um banho termostatizado (ensaio de degradação hidrolítica), in vitro, à temperatura de 37°C. As amostras foram retiradas do banho no intervalo de 1, 2, 3, 4, 7, 10 e 14 dias. Foram aferidas a perda de massa, a variação do pH e a concentração do hormônio liberado em função do tempo. Resultado: A concentração do hormônio liberado em função do tempo foi aumentando até o terceiro dia. No quarto dia, houve uma queda e, no sétimo, ocorreu um aumento do hormônio liberado, estendendo-se até o décimo dia; no 14° dia, houve queda novamente. O pH teve uma queda brusca de 7,4 para 3,2 no primeiro dia, mantendo uma pequena queda até o 14° dia. A perda de massa foi gradual em relação ao tempo, como já era esperado. Conclusão: O PLGA é um bom biomaterial para confecção de matrizes com hormônio do crescimento. Revelou-se possível incorporar o rhGH nessa matriz, de modo a, então, desenvolver-se um substituto ósseo.

Objective: Incorporate recombinant human growth hormone in a biodegradable polymer (PLGA). Material and method: The arrays were fabricated by solvent evaporation technique. A mixture of polymer (poly lactic glycolic acid) and recombinant human growth (Saizen® Merck Serono SA Aubonne, Switzerland) was performed hormone. This mixture was poured into circular molds silicone 01cm in diameter and about 02mm thick, and carried into a drying chamber for evaporation of solvent for 48 hours. After this period, the matrices were immersed in PBS and passed through a constant temperature bath (test for hydrolytic degradation) in vitro, at a temperature of 37°C. The samples were removed from the bath in the range of 01, 02, 03, 04, 07, 10, 14 days. Mass loss, pH and concentration of hormone released as a function of time was measured. Result: The concentration of hormone released versus time was increased until the third day. On the fourth day had a fall and on the seventh day there have been increased hormone released by the tenth day, the fourteenth day was falling again. The pH had a sharp drop from 7.4 to 3.2 on the first day and keeping a small drop until the fourteenth day. The mass loss was a gradual loss in relation to time as was to be expected. Conclusion: PLGA is a good biomaterial for making breeders of growth hormone. It has proved possible to incorporate the rhGH in the array so as to then develop a bone substitute.

Human alveolar bone-derived cell-culture behaviour on biodegradable poly(L-lactic Acid).

Poly(L-lactic acid) (PLA) is a polymer of great technological interest, whose excellent mechanical properties, thermal plasticity and bioresorbability render it potentially useful for environmental applications, as a biodegradable plastic and as a biocompatible material in biomedicine. The interactions between an implant material surface and host cells play central roles in the integration, biological performance and clinical success of implanted biomedical devices. Osteoblasts from human alveolar bone were chosen to investigate the cell behaviour when in contact with PLA discs. Cell morphology and adhesion through osteopontin (OPN) and fibronectin (FN) expression were evaluated in the initial osteogenesis, as well as cell proliferation, alkaline phosphatase activity and bone nodule formation. It was shown that the polymer favoured cell attachment. Cell proliferation increased until 21 days but in a smaller rate when compared to the control group. On the other hand, ALP activity and bone mineralization were not enhanced by the polymer. It is suggested that this polymer favours cell adhesion in the early osteogenesis in vitro, but it does not enhance differentiation and mineralization.

Apical extrusion of debris after hand, engine-driven reciprocating and continuous preparation / Extrusão apical de debris após o preparo manual e mecanizado oscilatório e contínuo

Purpose: This in vitro study assessed the amount of debris extruded apically after preparation with different techniques. Methods: Sixty healthy, extracted, human mandibular incisors were randomly divided into 3 groups: Group A - hand crown-down technique; Group B - crown-down technique with engine-driven rotary reciprocating instruments; Group C - Protaper: engine-driven continuous rotary instrumentation. The roots were immersed in 2.3 mL of distilled water. After preparation, the water in each tube was filtered to collect solid material extruded, and the filters were weighed using a precision scale. Data were analyzed by Kolmogorov-Smirnov and Kruskal-Wallis tests at the 0.05 level of significance. Results: The statistical analysis showed that group C had significantly higher values of debris than groups A and B. Conclusion: The instrumentation using a continuous rotary technique, Protaper, produced greater apical extrusion than the hand and engine-driven crown-down techniques. The direction of instrumentation, whether cervical-apical or apical-cervical, seems to be a more important factor influencing apical extrusion than whether the instrumentation was performed by hand or was engine-driven.

Objetivo: Este estudo, in vitro, avaliou a quantidade de extrusão apical de "debris", após o preparo químico-mecânico do canal radicular, utilizando diferentes técnicas. Metodologia: Sessenta incisivos inferiores humanos hígidos foram aleatoriamente divididos em três grupos: Grupo A: técnica coroa-ápice manual; Grupo B: técnica coroa-ápice mecanizada com sistema de rotação oscilatória; Grupo C: Protaper, técnica mecanizada com sistema derotação contínua. As raízes foram imersas em 2,3 mL de água destilada. Após os preparos, a água destilada de cada amostra foi filtrada, e o filtro de papel, contendo o material sólido extruído, foi pesado em uma balança analítica de precisão. Os dados foram analisados estatisticamente pelos testes Kolmogorov-Smirnov e Kruskal-Wallis ao nível de significância de 0,05. Resultados: A análise estatística demonstrou que o grupo C apresentou valores superiores de "debris" do que os grupos A e B. Conclusão: A técnica rotatória contínua com Pro-taper produziu maior quantidade de extrusão apical do que as técnicas coroa-ápice manual e mecanizada com sistema de rotação oscilatória. A direção da instrumentação, se cérvico-apical ou ápico-cervical, parece ser o fator mais determinante na extrusão de "debris" independente desta ser realizada manual ou mecanizada.