Abstract Tumor organoids have great potential as a 3D in vitro system to model cancer. In this work, we studied how the structure of hydrogels based on gelatin with methacryloyl groups (GeIMA) can affect their usage in tumor organoids. To this end, gelatin hydrogels with different levels of methacrylation and with cellulose nanocrystals (NCC) or reduced graphene oxide (rGO) were prepared and used to encapsulate human colon carcinoma cells (RKO). Mechanical properties of the hydrogels were measured in dynamic conditions at 37°C and water. Results showed that NCC was able to provide higher mechanical stability to the hydrogels. RKO cells embedded in GelMA were able to proliferate within the hydrogels, leading to the formation of groups of cells after 48 h. GelMA with higher crosslink densities and NCC tended to show higher cell population as possibly due to the higher level of stability and rigidity displayed by these hydrogels.

Abstract The properties of glass fiber-reinforced polymer composites are closely related to the fiber-matrix interface. Interfacial treatments to improve mechanical properties are usually limited to enhance interfacial adhesion. In this work, Layer-by-Layer (LbL) technique was introduced to build a novel interface in polymer composites. Different numbers of bilayers of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate) with carbon nanotubes were deposited through LbL on the surface of woven glass fibers (GFs). Polypropylene composites containing the modified GFs were prepared by compression molding. Thermogravimetric analysis, scanning electron microscopy and Raman spectroscopy proved that multilayers of polymers with carbon nanotubes could be deposited on GFs surface. Mechanical tests on composites with modified GFs revealed an increase in Flexural Modulus and toughness. The overall results attested that the LbL technique can be used to design interfaces with different compositions to perform diverse tasks, such as to improve the stiffness of composites and to encapsulate active nanocomponents.

In the present study, PHB film was prepared by thermo-compression molding and PHB nanofibers mat was produced through electrospinning process. The nanofibers morphology was confirmed by SEM. The film and nanofibers crystallinity degree was estimated by different methods. FTIR and WAXD indicated that PHB film is more crystalline than PHB nanofibers. However, DSC analysis suggested that a PHB nanofibers phase change might occur while the temperature rises. SAXS indicated that PHB film and nanofibers have low electron density contrast between the alternating crystalline and amorphous layers. The influence of nanofiber morphology on the mechanical, surface and thermal properties was also shown in TG analysis, tensile tests and contact angle measurements.

O polipropileno (PP) tem uma degradação natural lenta e representa um importante constituinte na gestão dos resíduos sólidos, enquanto o poli(hidroxibutirato) (PHB) é um polímero biodegradável, mas tem as desvantagens de dificuldade de processamento e custo. O objetivo deste trabalho foi avaliar o efeito de nanopartículas de TiO2, do método de processamento e do envelhecimento acelerado na estrutura e propriedades da mistura PP/PHB/TiO2. As amostras foram produzidas por etapas de extrusão e injeção e foram caracterizadas por MEV/EDS, FTIR e análise térmica. Os resultados mostraram que a incorporação de 3% de nanopartículas de TiO2 levou a um aumento do tamanho médio da fase dispersa rica em PHB. A mudança na sequência da adição de nanopartículas de TiO2 permitiu guiar a incorporação desses nanocomponentes para a fase rica em PP. As misturas produzidas se mostraram mais estáveis termicamente do que PHB puro e a adição de TiO2 foi eficaz em aumentar a estabilidade térmica dos compósitos. As análises termogravimétricas e por FTIR mostraram que blendas contendo nanopartículas de TiO2 tiveram sua degradação mais afetada nos ensaios de envelhecimento acelerado. Os ensaios de extração com solvente mostraram que um maior conteúdo de produtos de fotodegradação puderam ser extraídos de amostras contendo mais elevadas concentrações de TiO2.

Polypropylene (PP) has a slow natural degradation rate. On the other hand, poly(hydroxybutyrate) (PHB) is biodegradable but has the disadvantages of cost and difficulty of processing. The aim of this work was to evaluate the effect of TiO2 nanoparticles, processing conditions and accelerated aging on the structure and properties of PP/PHB/TiO2 mixtures. Samples were prepared by extrusion and injection molding. The incorporation of 3% TiO2 nanoparticles led to an increase in the average size of the dispersed phase rich in PHB. Changes in the sequence of TiO2 nanoparticles incorporation were able to guide the inclusion of nanoparticles to the PP-rich phase. The produced composites were more thermally stable than pure PHB and the incorporation of TiO2 was effective to increase the thermal stability of the composites. Thermal and FTIR analyses showed that blends containing TiO2 nanoparticles had their degradation more affected by accelerated aging treatments. Solvent extraction results revealed that a larger amount of soluble products from the photodegradation could be extracted from samples containing TiO2 submitted to accelerated aging treatments.

Waterborne Polyurethanes (PUs) are a family of polymers that contains urethane linkages synthesized in an aqueous environment and are thus free of organic solvents. Recently, waterborne PUs have been extensively studied for biomedical applications because of their biocompatibility. The present work investigates the following: (1) the impact on electrical performance of electrode materials (platinum and silicon) modified chemically by a layer of waterborne PU, and (2) the behavior of rat cardiac fibroblasts and rat cardiomyocytes when in contact with an electrode surface. Diisocyanate and poly(caprolactone diol) were the main reagents for producing PUs. The electrochemical impedance of the electrode/electrolyte interface was accessed by electrochemical impedance spectroscopy. The cellular viability, proliferation, and morphology changes were investigated using an MTT assay. Cardiomyocyte adherence was observed by scanning electron microscopy. The obtained surface was uniform, flat, and transparent. The film showed good adhesion, and no peeling was detected. The electrochemical impedance decreased over time and was influenced by the ionic permeability of the PU layer. The five samples did not show cytotoxicity when in contact with neonatal rat cells.

Bamboo is an alternative sustainable material for use in product design and has been incorporated into the concepts of eco-design. Here, we investigated the mechanical properties and morphologies of low density polyethylene (LDPE)/bamboo flour (BF) composites that were modified with polyethylene-graft-maleic anhydride (PE-g-MA) and glycerol. Scanning electron microscopy (SEM) and tensile tests of the composites demonstrated poor adhesion between the filler and matrix. Contact angle measurement showed that the surface of LDPE was modified by the presence of the load. The thermal stability of the composites was studied by measuring the oxidation induction time (OIT). Preliminary bacterial penetration tests were performed using culture inoculums of E. coli and S. aureus to investigate the natural antibacterial and bacteriostatic properties attributed to bamboo. Furthermore, bamboo may have interesting antioxidant activity with potential for use in food packaging applications.

A porous biodegradable polyurethane nanocomposite based on poly(caprolactone) (PCL) and nanocomponents derived from montmorillonite (Cloisite®30B) was synthesized and tested to produce information regarding its potential use as a scaffold for tissue engineering. Structural and morphological characteristics of this nanocomposite were studied by infrared spectroscopy (FTIR), X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM). The reaction between polyurethane oligomers with isocyanate endcapped chains and water led to the evolution of CO2, which was responsible for building interconnected pores with sizes ranging from 184 to 387 μm. An in vitro cell-nanocomposite interaction study was carried out using neonatal rat calvarial osteoblasts. The ability of cells to proliferate and produce an extracellular matrix in contact with the synthesized material was assessed by an MTT assay, a collagen synthesis analysis, and the expression of alkaline phosphatase. In vivo experiments were performed by subcutaneously implanting samples in the dorsum of rats. The implants were removed after 14, 21, and 29 days, and were analyzed by SEM and optical microscopy after tissue processing. Histology crosssections and SEM analyses showed that the cells were able to penetrate into the material and to attach to many location throughout the pore structure. In vitro and in vivo tests demonstrated the feasibility for polyurethane nanocomposites to be used as artificial extracellular matrices onto which cells can attach, grow, and form new tissues.

OBJETIVO: Avaliar o uso de implantes de compósito de matriz polimérica e biocerâmica na reconstrução do complexo zigomático orbitário e seu comportamento através de variáveis clínicas e tomográficas em seis pacientes. MÉTODOS: Foram selecionados seis pacientes portadores de deformidades faciais secundárias a fraturas órbito-zigomáticas graves (n=3) e a seqüelas da radioterapia e enucleação decorrentes do tratamento de retinoblastoma na infância. Este estudo foi submetido a avaliação e aprovação pelo Comitê de Ética em Pesquisa envolvendo seres humanos da Universidade Federal de Minas Gerais, instituição aonde a pesquisa vêm sendo desenvolvida (ETIC203/04). RESULTADOS: Em um ano de acompanhamento após a implantação do material demonstraram ausência de reações inflamatórias locais. Os achados tomográficos demonstraram bom posicionamento do implante, não ocorrendo migrações ou deslocamentos, ausência de coleções ou reações de partes moles peri-implante e manutenção da projeção das partes moles suprajacentes ao implante na região da deformidade preexistente. CONCLUSÃO: Os compósitos têm demonstrado bons resultados para a reconstituição do esqueleto craniofacial. O biomaterial utilizado neste estudo alia biocompatibilidade à tecnologia nacional ampliando as possibilidades da sua utilização a menor custo.

PURPOSE: To evaluate through clinical and tomographic parameters implant behavior in orbital zygomatic reconstruction in six patients. METHODS: The subjects for this preliminary study consisted of six anophthalmic socket patients (3 patients presented residual orbital zygomatic deformities after complex facial fractures and 3 patients presented orbital zygomatic retraction after enucleation and radiotherapy to treat retinoblastoma in infancy). These deformities were surgically corrected with this composite implant. This study was approved and authorized by the Universidade Federal de Minas Gerais Ethical Committee for Research in Human Subjects (ETIC 203/04). Clinical data and tomographic images were utilized to assess the outcome of this study. RESULTS: There were no complications and tomographic findings revealed no implant reactions or migration and a good maintenance of soft tissue projection in the operated areas was achieved. Success of outcome in this preliminary study were encouraging. CONCLUSION: This study will be continued enrolling a larger sample and longer follow-up. Composite biomaterials have presented a good outcome in facial reconstructive surgery. The composite implants in this group have a good biocompatibility and combined with national technology can reduce costs providing more possibilities to many more patients.

Polyurethanes have been used in a series of applications due basically to their versatility in terms of controlling the behavior by altering basically the type of reagents used. However, for more specific and advanced applications, such as in membranes, biomaterials and sensors, well-organized and defined chemical functionalities are necessary. In this work, inorganic functionalities were incorporated into aliphatic polyurethanes (PU) having different macromolecular architectures. Polyurethanes were synthesized using a polyether diol and dicyclohexylmethane 4,4' diisocyanate (H12-MDI). Polyurethanes having carboxylic acid groups were also produced by introducing 2,2- bis (hydroxymethyl) propionic acid in the polymerization process. Inorganic functionalities were inserted into polyurethanes by reacting isocyanate end capped chains with aminopropyltriethoxysilane followed by tetraethoxysilane. PU having carboxylic acid groups yielded transparent samples after the incorporation of inorganic entities, as an evidence of smaller and better dispersed inorganic entities in the polymer network. FTIR and swelling measurements showed that polyurethanes having carboxylic acid groups had inorganic domains less packed, condensed and cross-linked when compared to polyurethanes with no carboxylic acid groups. Results also suggested that the progressive incorporation of inorganic moieties in both types of polyurethanes occurred in regions previously activated with inorganic functionalities, instead of by the creation of new domains. The temperatures of thermal decomposition and glass transition were also shifted to higher temperatures when inorganic functionalities were incorporated into polyurethanes.

Tissue engineering has evolved from the use of biomaterials for bone substitution that fulfill the clinical demands of biocompatibility, biodegradability, non-immunogeneity, structural strength and porosity. Porous scaffolds have been developed in many forms and materials, but few reached the need of adequate physical, biological and mechanical properties. In the present paper we report the preparation of hybrid porous polyvinyl alcohol (PVA)/bioactive glass through the sol-gel route, using partially and fully hydrolyzed polyvinyl alcohol, and perform structural characterization. Hybrids containing PVA and bioactive glass with composition 58SiO2-33CaO-9P2O5 were synthesized by foaming a mixture of polymer solution and bioactive glass sol-gel precursor solution. Sol-gel solution was prepared from mixing tetraethoxysilane (TEOS), triethylphosphate (TEP), and calcium chloride as chemical precursors. The hybrid composites obtained after aging and drying at low temperature were chemically and morphologically characterized through infrared spectroscopy and scanning electron microscopy. The degree of hydrolysis of PVA, concentration of PVA solution and different PVA-bioglass composition ratios affect the synthesis procedure. Synthesis parameters must be very well combined in order to allow foaming and gelation. The hybrid scaffolds obtained exhibited macroporous structure with pore size varying from 50 to 600 µm.

Híbridos de vidro bioativo/polímero são materiais de grande interesse em aplicações biomédicas devido às suas propriedades, que combinam a bioatividade dos materiais cerâmicos, com a flexibilidade dos polímeros. Para regeneração do tecido ósseo, propriedades mecânicas da matriz são críticas e o módulo e a resistência mecânica do material devem ser similares aos do osso natural. Em trabalhos anteriores desenvolvidos no grupo obtiveram-se espumas híbridas 80% vidro bioativo/20% álcool polivinílico (PVA), para aplicação em engenharia de tecidos. Neste trabalho foi aumentado o teor de PVA dos híbridos para otimizar suas propriedades mecânicas. Os híbridos foram preparados com fase inorgânica 70%SiO2-30%CaO e teores de PVA de 20 a 60%, através da hidrólise ácida de tetraetil ortosilicato, adição de CaCl2, PVA, surfactante e HF. A secagem das espumas mostrou-se crítica, ocorrendo grande contração do gel As amostras foram secas por duas rotas: (1): pré-secagem a 40°C em estufa e secagem a vácuo; (2): pré-secagem a 40°C em estufa com circulação de ar e secagem a alto vácuo. A rota de secagem 2 apresentou maior perda de água e menor contração das amostras. Corpos de prova cúbicos, 10x10x10mm, foram submetidos a ensaios de compressão com velocidade de aplicação de carga de 0,5mm/min. Observou-se que o aumento do teor de polímero na composição das espumas melhorou suas propriedades mecânicas.

Bioactive glass/ polymer hybrids are materials of high interest for biomedicals applications because their assets, they combine the bioactivity of ceramics, with the flexibility of the polymers. In bone regenerations, mechanicals properties of the scaffold are criticisms and they must be similar to the bone properties. In previous works, hybrid foams with 80% bioactive glass and 20% polyvinyl alcohol (PVA) were prepared by sol-gel process to application as scaffold for bone tissue engineering. In this work, the PVA fraction of the hybrids was increase for to improve their mechanicals properties. The hybrids were prepared with composition inorganic of 70%SiO2-30%CaO and PVA fractions of 20 to 60% by sol-gel method. The drying of the foams was a criticism stage, occurring ample contraction from the gel. The samples were drying for two routes: (1) pre-drying at 40ºC for 7 days and drying at vacuum for 48 hours; (2) pre-drying with air circulation at 40ºC for 7 days and drying at high vacuum for 48 hours. The drying route 2 had the most lost of water and the least contraction of samples. Five specimens of hybrids samples with dimensions 10x10x10mm were compressed at 0,5mm/min-1. The increase of PVA fraction in the hybrids improves their mechanicals properties.

OBJETIVO: Comparar dois novos biomateriais: compósito a 10% (Escola de Engenharia da Universidade Federal de Minas Gerais - UFMG - Brasil) e compósito a 20% (Escola de Engenharia da Universidade Federal de Minas Gerais - UFMG - Brasil), a dois materiais controles: Medpor® (Porex Surgical Inc. - EUA) e Polipore® (Homus Com. Ind. Ltda - Brasil). MÉTODOS: Estudo experimental randomizado duplo cego: em 28 coelhos, 56 implantes foram colocados por via transconjuntival após a remoção de fragmento de cartilagem da reborda orbitária superior de ambas as órbitas, formando-se 4 grupos: Grupo I: Compósito a 10%/Medpor®; Grupo II: Compósito a 10%/Polipore®; Grupo III: Compósito a 20%/Medpor®; Grupo IV: Compósito a 20%/Polipore®. Após permanência média de 19,7 semanas, o material explantado foi avaliado histomorfometricamente em microscopia óptica, e o estudo estatístico foi feito pelo teste t de Student. RESULTADOS: Nenhum implante sofreu extrusão, ocorrendo uma única exposição (Compósito a 20%). Comprovado similar biocompatibilidade dos materiais nos quatro grupos. A histomorfometria no entanto revelou nos compósitos a presença estatisticamente significativa de pseudocápsula mais espessa, com aumento do número de fibroblastos, maior quantidade de colágeno e neovasos, e menor número de células inflamatórias. Foi possível detectar na interface implante-tecido nos compósitos, a presença de camada de hidroxiapatita carbonatada, funcionando como cola biológica. A integração tecidual dos implantes através dos poros foi maior nos controles que nos compósitos. CONCLUSÃO: Os compósitos foram aprovados quanto a biocompatibilidade, e apresentaram adicionalmente algumas vantagens sobre o Medpor® e o Polipore®.

PURPOSE: To compare two new biomaterials: Composite 10% (Engineering School - Universidade Federal de Minas Gerais - UFMG - Brazil) and Composite 20% (Engineering School - Universidade Federal de Minas Gerais - UFMG - Brazil), with two similar materials as control: MedporTM (Porex Surgical Inc. - USA) e PoliporeTM (Homus Com. Ind. Ltda - BRASIL). METHODS: In vivo randomized experimental double blind study: a transconjunctival approach was performed in both cartilaginous superior orbital walls of 28 rabbits for 56 implants divided into 4 groups: GI: Composite 10%/MedporTM; GII: Composite 10%/PoliporeTM; GIII: Composite 20%/MedporTM; GIV: Composite 20%/PoliporeTM. The mean rate for implant time of permanence was 19.7 weeks. The Student's t test was used for statistical analysis. RESULTS: Revealed similar biocompatibility of all materials and none of the implants was extruded; one Composite 20% had partial exposure. Histomorphometry showed a greater bioactivity of the composites with significantly thicker fibrous encapsulation, with more collagen and fibroblasts, exuberant angiogenesis, and a lower inflammatory cell mean compared to controls. The presence of precipitation of a hydroxycarbonate apatite layer, which acts as an implant-tissue bond was confirmed. Composites presented a smaller tissular invasion index of the pores compared to controls. CONCLUSIONS: The composites showed a good biocompatibility and some additional advantageover the MedporTM and PoliporeTM controls.

Polymerization shrinkage is a critical factor affecting the longevity and acceptability of dental composite resins. The aim of this work was to evaluate the effect of light intensity and irradiation time on the polymerization process of a photo cured dental composite resin by measuring the Vickers hardness number (VHN) and the volumetric polymerization shrinkage. Samples were prepared using a dental manual light-curing unit. The samples were submitted to irradiation times of 5, 10, 20 and 40 s, using 200 and 400 mW.cm-2 light intensities. Vickers hardness number was obtained at four different moments after photoactivation (immediate, 1 h, 24 h and 168 h). After this, volumetric polymerization shrinkage values were obtained through a specific density method. The values were analyzed by ANOVA and Duncan's (p = 0.05). Results showed increase in hardness values from the immediate reading to 1 h and 24 h readings. After 24 h no changes were observed regardless the light intensities or activation times. The hardness values were always smaller for the 200 mW.cm-2 light intensity, except for the 40 s irradiation time. No significant differences were detected in volumetric polymerization shrinkage considering the light intensity (p = 0.539) and the activation time (p = 0.637) factors. In conclusion the polymerization of the material does not terminate immediately after photoactivation and the increase of irradiation time can compensate a lower light intensity. Different combinations between light intensity and irradiation time, i.e., different amounts of energy given to the system, have not affected the polymerization shrinkage.

Calcium phosphates and bioactive glasses have been used in many biomedical applications for more than 30 years due basically to their bioactive behavior. However, ceramics are too brittle for applications that require high levels of toughness and easy processability. In this work, a biphasic calcium phosphate (BCP) and a bioactive glass composition (BG) were combined with polymers to produce composites with tailorable properties and processability. The BCP particles were synthesized by a precipitation technique. The BG particles were produced by sol-gel processing. The BCP particles were treated with a silane agent to improve the compatibility between particles and the polymer matrix. Dense samples were produced by hot pressing (200 °C) a mixture of 30 wt.% of particles in poly (methyl methacrylate). The samples produced were characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Mechanical properties were evaluated by a three point bending test. Samples were also submitted to in vitro bioactivity test and in vivo toxicity test. Results showed that the production of the composites was successfully achieved, yielding materials with particles well dispersed within the matrices. Evaluation of the in vivo inflammatory response showed low activity levels for all composites although composites with silane treated BCP particles led to milder inflammatory responses than composites with non-treated particles.

Este estudo teve como objetivo avaliar a correlação entre grau de conversão e microdureza em resinas compostas, e o efeito do conteúdo de partículas e do tipo de unidade fotoativadora sobre esses parâmetros. Três resinas compostas (Artglass®, Solidex® e Zeta LC®) foram polimerizadas em três diferentes unidades laboratoriais (UniXS®, Solidilite® e unidade Experimental). Para cada material, quinze corpos-de-prova foram confeccionados em uma matriz metálica, e submetidos às análises do grau de conversão, através de espectroscopia de infravermelho, e da microdureza. O conteúdo de partículas inorgânicas foi determinado por análise termogravimétrica (TGA). O comportamento conjunto das variáveis - grau de conversão e microdureza - foi medido através do coeficiente de correlação de Pearson. Para a resina Artglass®, o grau de conversão variou de 37,5% a 79,2%, com valores de microdureza de 32,4 a 50,3 (r = 0,904). Para a resina Solidex®, o grau de conversão variou de 41,2% a 60,4%, com valores de microdureza de 33,3 a 44,1 (r = 0,707). Para a resina Zeta LC®, os valores de conversão e microdureza foram, respectivamente, de 62,0% a 78,0% e de 22,6 a 33,6 (r = 0,710). Concluiu-se que o uso das diferentes unidades resultou em variações dos valores de conversão em função das características específicas de cada unidade. Para cada material, uma forte correlação entre conversão e microdureza foi observada. Além disso, quando materiais diferentes foram comparados, observou-se que o conteúdo de partículas inorgânicas afetou diretamente os valores de microdureza, não interferindo no grau de conversão.

The purpose of this study was to evaluate the correlation between degree of conversion and microhardness in dental composites, as well as the effect of the inorganic content and type of photo-curing unit on these parameters. Three indirect composites (ArtglassTM, SolidexTM and Zeta LCTM) were polymerized by means of three different laboratorial units (UniXSTM, SolidiliteTM and an experimental device). For each material, fifteen samples were prepared using a metal matrix. The degree of conversion was analyzed by means of infrared spectroscopy, and microhardness was also assessed. The inorganic content was measured by means of thermogravimetric analysis (TGA). The Pearson’s test was carried out in order to determine correlations. The degree of conversion of ArtglassTM ranged from 37.5% to 79.2%, and its microhardness, from 32.4 to 50.3 (r = 0.904). The degree of conversion of SolidexTM ranged from 41.2% to 60.4%, and its microhardness, from 33.3 to 44.1 (r = 0.707). The degree of conversion and the microhardness of Zeta LCTM ranged from 62.0% to 78.0% and from 22.6 to 33.6, respectively (r = 0.710). It was concluded that the utilization of different photo-curing units caused variations on the degree of conversion, as a result of specific characteristics of each unit. For each material, there was strong correlation between the degree of conversion and microhardness. In addition, when different materials were compared, microhardness was more affected by filler content than by the degree of conversion.