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1.
An Acad Bras Cienc ; 93(3): e20200924, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34076183

RESUMO

The objectives of this research were to study (1) the dispersion of MWCNTs in an aqueous system by three commercial admixtures (CAds) for concrete, and (2) the effect of CAds and MWCNTs on indirect tensile strength and electrical conductivity of MWCNTs-high early strength (HE) cement-mortar composites. To achieve the objectives, we dispersed MWCNTs in an aqueous system with (1) hydroxylated polymers-based water reducing plasticizer (HPs), a nonionic compound, (2) Naphthalene based superplasticizer (SNF), an anionic compound, and (3) calcium chloride-based accelerating agent (CC) a neutral amphoteric salt. We prepared a total of 242 samples grouped in three sets: (1) Plain mortar [PM] (water + HE cement + Sand), (2) [PM+CAd], and (3) [PM+CAd+MWCNTs]. The three CAds dispersed MWCNTs in an aqueous solution. The CC and HPs admixtures have a two-time bigger dispersing power than the SNF. They demand half of SNF's ultrasound energy for optimal dispersion. Although the SNF (anionic) based superplasticizer resulted incompatible with the HE cement, it improved the indirect tensile strength of [PM+SNF+MWCNTs] composite. In contrast, the CC (amphoteric) based accelerating agent was compatible with the HE cement; the CC adsorption on the MWCNTs surface favors an improvement in the electrical conductivity of [PM+CAd+MWCNTs] composite.


Assuntos
Materiais de Construção , Cimentos de Ionômeros de Vidro , Condutividade Elétrica , Resistência à Tração
2.
J Adhes Dent ; 23(3): 243-252, 2021 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-34060304

RESUMO

PURPOSE: To investigate the influence of the etching strategy of universal adhesives on bond degradation to sound and artificially-induced caries-affected dentin. MATERIALS AND METHODS: The universal adhesives (Scotchbond Universal Adhesive; All-Bond Universal; Prime&Bond Elect) and adhesives used as controls (Adper Single Bond 2 and Clearfil SE Bond) were applied to sound and artificially-induced caries-affected bovine dentin. Microtensile bond strength was evaluated immediately (24 h) and after one year of water storage (1 year). Representative specimens were also prepared to assess nanoleakage. Bond strength data (MPa) were analyzed using three-way ANOVA and post-hoc Tukey's test (α = 0.05), considering each substrate separately. RESULTS: Bonding degradation was observed for all universal adhesives on caries-affected dentin, irrespective of the etching strategy. On sound dentin, bonding degradation was observed when adhesives were used on the etch-and-rinse strategy. CONCLUSION: The universal adhesives were not capable of maintaining bond stability over time on caries-affected dentin. The self-etch strategy seems better able to maintain the durability of adhesive interfaces created on sound dentin.


Assuntos
Colagem Dentária , Cárie Dentária , Animais , Bovinos , Cárie Dentária/terapia , Suscetibilidade à Cárie Dentária , Dentina , Resistência à Tração
3.
J Adhes Dent ; 23(3): 255-265, 2021 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-34060305

RESUMO

PURPOSE: To evaluate the effect of different surface modification methods on the microtensile bond strength (µTBS) of four resin-matrix CAD/CAM ceramics after artificial aging. MATERIALS AND METHODS: Specimens of four CAD/CAM materials (Shofu Block HC, Lava Ultimate, Brilliant Crios, and Vita Enamic) were prepared and divided into four groups. Each group received one of the following treatments: group 1 (INT): no surface modification; group 2: sandblasting with 29-µm Al2O3 particles (SB); group 3: hydrofluoric acid etching (9%) + silane (HF+Si); group 4: sandblasting with 30-µm particles of the CoJet system (CJ). The specimens of each group were luted together in pairs using resin cement (RelyX Ultimate). After one week of water storage (37°C), the sandwich specimens were sectioned into rectangular microspecimens and half of them were immediately subjected to µTBS testing, while the other half was tested after six months. Data were statistically analyzed using FFANOVA including the factors of material, treatment, and storage time, with α = 0.05. RESULTS: After one week, the lowest µTBS was observed for INT, while the highest was found for either mechanical (SB and CJ) or chemical (HF+Si) treatments (p < 0.05). After six months, a significant decrease in µTBS was observed depending on treatment (p < 0.05), while artificial aging significantly influenced the µTBS of all experimental groups (p < 0.05). During the two storage periods, the failure type was mainly interfacial and was associated with the type of surface modification. CONCLUSION: After artificial aging, the µTBS appeared to depend on srface modification, while the parameter "material" did not influence the results. Consequently, adhesive strategies should be oriented towards surface modification techniques.


Assuntos
Colagem Dentária , Cimentos de Resina , Cerâmica , Teste de Materiais , Propriedades de Superfície , Resistência à Tração
4.
Arch Oral Biol ; 127: 105148, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34022546

RESUMO

OBJECTIVE: The aim of this study was to synthesize and characterize an experimental primer containing cationic lipid nanoparticles (NPL-chitosan) and to evaluate its properties. DESIGN: The NPL-chitosan were synthesized by emulsion and sonication method. The experimental primers were applied in dentin surface of fifty human molars. The experimental groups were: 1) application of commercial primer; 2) Primer containing 2% of Chlorhexidine (CHX) 3); Primer with 2% NPL-chitosan 4); Primer with 0.6 % of NPL-chitosan 5); Primer with 0.4 % of NPL-chitosan. A composite resin plateau was used for the analysis, where sections were made for making the dentin beams. The effect of experimental primer with cationic nanoparticles in the inhibition of matrix metalloproteinase (MMP) activity was carrying out by in situ zymography. For the Resin-Dentin Adhesive Strength and in situ Zymography analysis, was used the One-way analysis of variance (ANOVA) with significance level of 95 %. RESULTS: Spherical NPL-chitosan presented size below 220 nm, polydispersity index of 0.179 and zeta potential positive and was stable over 75 days. These nanoparticles showed antibacterial activity agsainst S. mutans with MIC of the 0.4 % and MBC of 0.67 %. In the Microtensile Strength, no statistical difference was observed between the experimental groups (p = 0.9054). The in situ zymography assay showed that the group with 2% of NPL-chitosan presented higher inactivation activity of MMPs compared to the other groups (p < 0.05). CONCLUSION: The experimental primer containing NPL-chitosan has antimicrobial activity, does not alter the adhesive resistance and inactivates MMPs present in dentin.


Assuntos
Quitosana , Colagem Dentária , Nanopartículas , Resinas Compostas , Cimentos Dentários/farmacologia , Dentina , Adesivos Dentinários , Humanos , Teste de Materiais , Metaloproteases , Cimentos de Resina , Resistência à Tração
5.
AAPS PharmSciTech ; 22(4): 151, 2021 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-33977355

RESUMO

As commonly known, the product development stage is quite complex, requires intensive knowledge, and is time-consuming. The selection of the excipients with the proper functionality and their corresponding levels is critical to drug product performance. The objective of this study was to apply quality by design (QbD) principles for formulation development and to define the desired product quality profile (QTPP) and critical quality attributes (CQA) of a product. QbD is a risk- and science-based holistic approach for upgraded pharmaceutical development. In this study, Ibuprofen DC 85W was used as a model drug, Cellactose® 80 along with MicroceLac® 100 as a filler, and magnesium stearate, stearic acid, and sodium stearyl fumarate as lubricants. By applying different formulation parameters to the filler and lubricants, the QbD approach furthers the understanding of the effect of critical formulation and process parameters on CQAs and the contribution to the overall quality of the drug product. An experimental design study was conducted to determine the changes of the obtained outputs of the formulations, which were evaluated using the Modde Pro 12.1 statistical computer program that enables optimization by modeling complex relationships. The results of the optimum formulation revealed that MicroceLac® 100 was the superior filler, while magnesium stearate at 1% was the optimum lubricant. A design space that indicates the safety operation limits for the process and formulation variables was also created. This study enriches the understanding of the effect of excipients in formulation and assists in enhancing formulation design using experimental design and mathematical modeling methods in the frame of the QbD approach.


Assuntos
Química Farmacêutica/métodos , Força Compressiva , Desenvolvimento de Medicamentos/métodos , Lubrificantes/síntese química , Química Farmacêutica/normas , Composição de Medicamentos/métodos , Desenvolvimento de Medicamentos/normas , Ibuprofeno/síntese química , Ibuprofeno/normas , Lubrificantes/normas , Ácidos Esteáricos/síntese química , Ácidos Esteáricos/normas , Tensoativos/síntese química , Tensoativos/normas , Comprimidos , Resistência à Tração
6.
AAPS PharmSciTech ; 22(4): 154, 2021 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-33983536

RESUMO

In twin screw melt granulation, granules are produced by passing mixtures of drug substances and polymeric binders through twin screw extruder such that temperatures are maintained below melting point of drugs but above glass transition of polymers used, whereby the polymers coat surfaces of drug particles and cause their agglomeration into granules. Since various formulation factors, such as binder type and concentration, and processing variables like extrusion temperature, screw configuration, and screw speed, can influence the granulation process, the present investigation was undertaken to study their effects on tabletability of granules produced. Three different types of polymeric binders, Klucel® EXF (hydroxypropyl cellulose), Eudragit® EPO (polyacrylate binder), and Soluplus® (polyvinyl caprolactam-co-vinyl acetate-ethylene glycol graft polymer), were used at 2, 5, and 10% concentrations. Metformin hydrochloride (HCl) (mp: 222°C) and acetaminophen (mp: 169°C) were used as model drugs, and drug-polymer mixtures with metformin HCl were extruded at 180, 160, and 130°C, while those with acetaminophen were extruded at 130 and 110°C. Other process variables included screw configurations: low, medium, and high shear for metformin HCl, and low and medium shear for acetaminophen; feed rates: 20 and 60 g/min; and screw speed of 100 and 300 RPM. Formulation and process variables had significant impact on tabletability. The target tensile strength of ≥2 MPa could be obtained with all polymers and at all processing temperatures when metformin HCl was granulated at 180°C and acetaminophen at 130°C. At other temperatures, the target tensile strength could be achieved at certain specific sets of processing conditions.


Assuntos
Acetaminofen/síntese química , Química Farmacêutica/métodos , Composição de Medicamentos/métodos , Metformina/síntese química , Polímeros/síntese química , Analgésicos não Narcóticos/síntese química , Congelamento , Hipoglicemiantes/síntese química , Tamanho da Partícula , Comprimidos , Resistência à Tração
7.
Clinics (Sao Paulo) ; 76: e2358, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33978072

RESUMO

OBJECTIVES: In the present study, a novel single knot tenorrhaphy was developed by combining the modified Kessler flexor tendon suture (MK) with the loop lock technique. METHODS: A total of 48 porcine flexor digitorum profundus tendons were collected and randomly divided into six groups. The tendons were transversely cut and then repaired using six different techniques, the MK method, double knot Kessler-loop lock flexor tendon suture (DK), and single knot Kessler-loop lock flexor tendon suture (SK), each in combination with the epitendinous suture (P), and the same three techniques without P. Furthermore, by performing the load-to-failure tests, the biomechanical properties and the time taken to complete a repair, for each tenorrhaphy, were assessed. RESULTS: Compared to the MK+P method, DK+P was more improved, thereby enhancing the ultimate tensile strength. The SK+P method, which required fewer knots than DK+P, was easier to perform. Moreover, the SK+P repair increased the force at a 2-mm gap formation, while requiring lesser knots than DK+P. CONCLUSION: As opposed to the traditional MK+P method, the SK+P method was improved and exhibited better biomechanical properties, which may facilitate early mobilization after the repair.


Assuntos
Técnicas de Sutura , Suturas , Animais , Fenômenos Biomecânicos , Suínos , Tendões/cirurgia , Resistência à Tração
8.
J Mech Behav Biomed Mater ; 119: 104516, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33932753

RESUMO

Cryopreservation is required to preserve the native properties of tissue for prolonged periods of time. In this study, we evaluate the impact that 4 different cryopreservation protocols have on porcine urethral tissue, to identify a protocol that best preserves the native properties of the tissue. The cryopreservation protocols include storage in cryoprotective agents at -20 °C and -80 °C with a slow, gradual, and fast reduction in temperature. To evaluate the effects of cryopreservation, the tissue is mechanically characterised in uniaxial tension and the mechanical properties, failure mechanics, and tissue dimensions are compared fresh and following cryopreservation. The mechanical response of the tissue is altered following cryopreservation, yet the elastic modulus from the high stress, linear region of the Cauchy stress - stretch curves is unaffected by the freezing process. To further investigate the change in mechanical response following cryopreservation, the stretch at different tensile stress values was evaluated, which revealed that storage at -20 °C is the only protocol that does not significantly alter the mechanical properties of the tissue compared to the fresh samples. Conversely, the ultimate tensile strength and the stretch at failure were relatively unaffected by the freezing process, regardless of the cryopreservation protocol. However, there were alterations to the tissue dimensions following cryopreservation that were significantly different from the fresh samples for the tissue stored at -80 °C. Therefore, any study intent on preserving the mechanical, failure, and geometric properties of urethral tissue during cryopreservation should do so by freezing samples at -20 °C, as storage at -80 °C is shown here to significantly alter the tissue properties.


Assuntos
Criopreservação , Animais , Módulo de Elasticidade , Congelamento , Suínos , Temperatura , Resistência à Tração
9.
J Mech Behav Biomed Mater ; 119: 104552, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33934037

RESUMO

As the global trauma fixation devices market expands rapidly, it is imperative to improve the production of fixation devices through enhanced design accuracy and fit for best performance and maximum patient comfort. Selective laser melting (SLM) is one of the mature additive manufacturing methods, which provides a viable route for the rapid production of such devices. In this work, the ability of SLM to produce near-net-shape parts, as desired for medical implants, was utilized for the fabrication of bone plates from Ti-6Al-4V alloy powder. Martensitic microstructure obtained after the printing of alloy resulted in poor ductility, limiting its application in the field of orthopedics. A specially designed repeated cyclic heating and cooling close to but below the ß-transus was used to transform from acicular to a bimodal microstructure without the need for plastic deformation prior to heat treatment for improving the ductility. Bone plates subjected to this heat treatment were mechanically tested by means of tensile and 3-point bend tests and demonstrated large improvement in ductility, and the values were comparable to those similar plates prepared from wrought alloy. Other important properties required for implants were assessed, such as corrosion resistance in simulated body fluid and cytocompatibility in vitro using MC3T3-E1 cells. These results for the bone plate after heat treatment were excellent and similar to those of the additively manufactured and wrought plates. Taken together, the performance of the additively manufactured bone plates after subjecting to heat treatment was similar to those of bone plate manufactured using wrought alloy. These results have important implications for the fabrication of patient-specific metallic orthopedic devices using SLM without compromising their biomechanical performance by subjecting them to a tailored heat treatment.


Assuntos
Placas Ósseas , Titânio , Ligas , Humanos , Próteses e Implantes , Resistência à Tração
10.
Am J Vet Res ; 82(6): 510-515, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34032486

RESUMO

OBJECTIVE: To determine the effect of epitendinous suture (ES) caliber on the tensile strength of flexor tendon repairs in cadaveric specimens from dogs. SAMPLE: 60 cadaveric superficial digital flexor tendons (SDFTs) from 30 skeletally mature dogs. PROCEDURES: Specimens were randomly assigned to 5 suture caliber groups (n = 12 SDFTs/group). After sharp transection, SDFTs were repaired by placement of a simple continuous circumferential ES created with size-0, 2-0, 3-0, 4-0, or 5-0 polypropylene suture. Constructs were preloaded to 2 N and load tested to failure. Loads at yield, peak, and failure and mode of failure were compared among groups by statistical methods. RESULTS: Yield, peak, and failure loads for SDFT repair constructs were positively correlated with ES caliber and did not differ between the size-0 and 2-0 groups on pairwise comparisons. Yield load was significantly greater for size-0, 2-0, and 3-0 groups than for the 4-0 and 5-0 groups. Peak and failure loads were significantly greater for the size-0 and 2-0 groups than for the remaining groups. Most size-0 (12/12), 2-0 (12/12), and 3-0 (10/12) group constructs failed because of ES pull-through; several constructs in the 4-0 group (5/12) and most in the 5-0 group (11/12) failed because of ES breakage. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested size-0 and 2-0 sutures should be considered when placing an ES for flexor tendon repairs in dogs. However, in vivo studies are needed determine the effects of increasing ES caliber on clinical outcomes for dogs undergoing these procedures.


Assuntos
Doenças do Cão , Traumatismos dos Tendões , Animais , Fenômenos Biomecânicos , Cadáver , Cães , Técnicas de Sutura/veterinária , Suturas/veterinária , Traumatismos dos Tendões/cirurgia , Traumatismos dos Tendões/veterinária , Tendões/cirurgia , Resistência à Tração
11.
Oper Dent ; 46(1): E1-E10, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33882142

RESUMO

CLINICAL RELEVANCE: Carious and eroded dentin represent clinical challenges. The use of a universal bonding system, in a self-etching mode, associated with chlorhexidine (CHX) seems to not improve its longevity. This may be attributed to the competition for calcium between the bonding agent functional monomer and CHX.


Assuntos
Clorexidina , Colagem Dentária , Cimentos Dentários , Dentina , Adesivos Dentinários , Teste de Materiais , Cimentos de Resina , Resistência à Tração
12.
J Adhes Dent ; 23(2): 159-165, 2021 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-33825429

RESUMO

PURPOSE: To evaluate the effect of inclusion of two dimethyl sulfoxide (DMSO) concentrations in simplified etch-and-rinse adhesives on dentin bonding durability after three years of water storage. MATERIALS AND METHODS: Forty-two caries-free third molars were divided into six experimental groups (n = 7) according to the following factors: 1) adhesive (Adper Single Bond 2 [SB], 3M Oral Care; Prime&Bond 2.1 [PB], Dentsply Sirona); 2) concentration of DMSO (control group: 0.0% DMSO; addition of 0.2% DMSO [0.2] and 2% DMSO [2.0]). After completing restoration, specimens were stored in water (37°C) for 24 h, sectioned into adhesive-dentin sticks (0.8 mm2), tested for microtensile bond strength (µTBS) at 0.5 mm/min, and examined for nanoleakage (NL) using SEM immediately thereafter or after three years of water storage. Data were subjected to a three-way repeated-measures ANOVA and Tukey's test (α = 0.05) for each property evaluated. RESULTS: After three years of water storage, for both adhesives, the incorporation of 2% DMSO maintained the µTBS when compared to immediate µTBS (p > 0.05). In general, SB resulted in a statistically significantly higher mean of µTBS compared to PB, independent of the DMSO concentration after water storage (p < 0.05). Furthermore, the amount of NL was lower and practically limited to the hybrid layer given the concentrations of 0.2% and 2% DMSO for both tested adhesives after three years. CONCLUSION: The incorporation of DMSO in simplified etch-and-rinse adhesives maintains the long-term stability of the dentin bond.


Assuntos
Colagem Dentária , Adesivos Dentinários , Dentina , Dimetil Sulfóxido , Teste de Materiais , Cimentos de Resina , Resistência à Tração , Água
13.
Int J Mol Sci ; 22(7)2021 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-33805875

RESUMO

This article compares the properties of bacterial cellulose/fish collagen composites (BC/Col) after enzymatic and chemical cross-linking. In our methodology, two transglutaminases are used for enzymatic cross-linking-one recommended for the meat and the other proposed for the fish industry-and pre-oxidated BC (oxBC) is used for chemical cross-linking. The structure of the obtained composites is characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy, and their functional properties by mechanical and water barrier tests. While polymer chains in uncross-linked BC/Col are intertwined by H-bonds, new covalent bonds in enzymatically cross-linked ones are formed-resulting in increased thermal stability and crystallinity of the material. The C2-C3 bonds cleavage in D-glucose units, due to BC oxidation, cause secondary alcohol groups to vanish in favor of the carbonyl groups' formation, thus reducing the number of H-bonded OHs. Thermal stability and crystallinity of oxBC/Col remain lower than those of BC/Col. The BC/Col formation did not affect tensile strength and water vapor permeability of BC, but enzymatic cross-linking with TGGS improved them significantly.


Assuntos
Celulose/química , Colágeno/química , Reagentes para Ligações Cruzadas/química , Gluconacetobacter/química , Animais , Enzimas/química , Peixes , Ligação de Hidrogênio , Microscopia Eletrônica de Varredura , Permeabilidade , Polímeros , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Temperatura , Resistência à Tração , Termogravimetria , Difração de Raios X
14.
Int J Mol Sci ; 22(7)2021 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-33805101

RESUMO

Hydrogels based on chitosan are very versatile materials which can be used for tissue engineering as well as in controlled drug delivery systems. One of the methods for obtaining a chitosan-based hydrogel is crosslinking by applying different components. The objective of the present study was to obtain a series of new crosslinked chitosan-based films by means of solvent casting method. Squaric acid-3,4-dihydroxy-3-cyclobutene-1,2-dione-was used as a safe crosslinking agent. The effect of the squaric acid on the structural, mechanical, thermal, and swelling properties of the formed films was determined. It was established that the addition of the squaric acid significantly improved Young's modulus, tensile strength, and thermal stability of the obtained materials. Moreover, it should be stressed that the samples consisting of chitosan and squaric acid were characterized by a higher swelling than pure chitosan. The detailed characterization proved that squaric acid could be used as a new effective crosslinking agent.


Assuntos
Quitosana/química , Reagentes para Ligações Cruzadas/química , Ciclobutanos/química , Materiais Biocompatíveis/química , Módulo de Elasticidade , Hidrogéis/química , Teste de Materiais , Microscopia de Força Atômica , Solventes , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Resistência à Tração , Termodinâmica , Termogravimetria , Engenharia Tecidual/métodos
15.
J Hand Surg Asian Pac Vol ; 26(2): 188-193, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33928850

RESUMO

Background: The purpose of the present study was to assess the biomechanical strength and properties of a modified Krackow technique for side-to-side tendon repair with a short overlap length. Methods: The flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus muscles were harvested from 10 fresh frozen cadavers. Overall, 60 tendon repairs were divided into four groups based on the suture technique: modified Krackow technique repair (KT); weave suture repair (WS); mattress suture repair (MS); and composite technique repair (CT), a combination of the modified Krackow and weave suture techniques. Single loading mechanical tests were performed, and the results for each suture technique were compared. Results: Ultimate loads for KT, WS, MS, and CT were 155 ± 45 N, 122 ± 18 N, 92 ± 31 N, and 163 ± 22 N, respectively. KT and CT had significantly higher ultimate loads than the other groups. However, the difference between the KT and CT groups in terms of ultimate load was not significant. Conclusions: Based on the results from the single loading tests, the use of the modified Krackow and composite techniques appeared to provide stronger fixation than that with the use of the weave and mattress sutures with a short overlap length.


Assuntos
Técnicas de Sutura , Traumatismos dos Tendões/cirurgia , Idoso , Idoso de 80 Anos ou mais , Cadáver , Feminino , Humanos , Masculino , Estresse Mecânico , Resistência à Tração
16.
Waste Manag ; 126: 538-548, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33848726

RESUMO

Grape stalks are a lignocellulosic biomass, which is a very complex material, whose easy and profitable fractionation to obtain its basic components is still not available. Therefore, alternative ways to try and make use of grape stalks are currently being explored. In the present study, the possible use of dried and milled grape stalks as filler in bio-composites was assessed using polybutylene succinate as a basic polymer. The tensile specimens produced using 10% grape stalk powder as it is and functionalized through pre-extrusion acetylation and silylation, and silylation in situ were characterized for their structural, mechanical, thermal, morphological, and color properties. The bio-composites showed to be stiffer than the control polymer, with an increase of Young's modulus from 616 MPa to 732 MPa in the specimens obtained with acetylated grape stalk powder. This led to a potentially new method to valorize by-products of the wine industry such as grape stalks in order to recover raw materials which could prove useful in the biomaterials and bio-composites sector.


Assuntos
Vitis , Butileno Glicóis , Polímeros , Resistência à Tração
17.
Molecules ; 26(9)2021 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-33922098

RESUMO

More than 23 million tonnes of lignin are produced annually in the US from wood pulping and 98% of this lignin is burnt. Therefore, creating products from lignin, such as plastics, offers an approach for obtaining sustainable materials in a circular economy. Lignin-based copolymers were synthesized using a single pot, solvent free, melt condensation reaction. The synthesis occurred in two stages. In the first stage, a biobased prepolymer consisting of butanediol (BD, 0.8-1 molar content) and a diacid (succinic (SA), adipic (AA) and suberic acids (SuA), with varying amounts of diaminobutane (DAB, 0-0.2 molar content) was heated under vacuum and monitored by Fourier transform infra-red (FTIR) spectroscopy and electrospray ionization-mass spectrometry (ESI-MS). In the second stage, prepolymer was mixed with a softwood kraft lignin (0-50 wt.%) and further reacted under vacuum at elevated temperature. Progression of the polymerization reaction was monitored using FTIR spectroscopy. The lignin-copolyester/amide properties were characterized using tensile testing, X-ray diffraction (XRD), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. Lignin co-polymer tensile (strength 0.1-2.1 MPa and modulus 2 to 338 MPa) properties were found to be influenced by the diacid chain length, lignin, and DAB contents. The lignin-copolymers were shown to be semi-crystalline polymer and have thermoplastic behavior. The SA based copolyesters/amides were relatively stiff and brittle materials while the AA based copolyesters/amides were flexible and the SuA based copolyesters/amides fell in-between. Additionally, > 30 wt.% lignin the lignin- copolyesters/amides did not exhibit melt behavior. Lignin-co-polyester/amides can be generated using green synthesis methods from biobased building blocks. The lignin- copolyesters/amides properties could be tuned based on the lignin content, DAB content and diacid chain length. This approach shows that undervalued lignin can be used in as a macromonomer in producing thermoplastic materials.


Assuntos
Amidas/química , Lignina/química , Plásticos/química , Poliésteres/química , Fenômenos Químicos , Estrutura Molecular , Polimerização , Espectrometria de Massas por Ionização por Electrospray , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Resistência à Tração , Termogravimetria , Difração de Raios X
18.
Molecules ; 26(8)2021 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-33924692

RESUMO

Hydrophilic behaviour of carrageenan macroalgae biopolymer, due to hydroxyl groups, has limited its applications, especially for packaging. In this study, macroalgae were reinforced with cellulose nanofibrils (CNFs) isolated from kenaf bast fibres. The macroalgae CNF film was after that treated with silane for hydrophobicity enhancement. The wettability and functional properties of unmodified macroalgae CNF films were compared with silane-modified macroalgae CNF films. Characterisation of the unmodified and modified biopolymers films was investigated. The atomic force microscope (AFM), SEM morphology, tensile properties, water contact angle, and thermal behaviour of the biofilms showed that the incorporation of Kenaf bast CNF remarkably increased the strength, moisture resistance, and thermal stability of the macroalgae biopolymer films. Moreover, the films' modification using a silane coupling agent further enhanced the strength and thermal stability of the films apart from improved water-resistance of the biopolymer films compared to unmodified films. The morphology and AFM showed good interfacial interaction of the components of the biopolymer films. The modified biopolymer films exhibited significantly improved hydrophobic properties compared to the unmodified films due to the enhanced dispersion resulting from the silane treatment. The improved biopolymer films can potentially be utilised as packaging materials.


Assuntos
Biopolímeros/química , Celulose/química , Silanos/química , Hibiscus/química , Nanocompostos/química , Alga Marinha/metabolismo , Resistência à Tração
19.
Mar Drugs ; 19(3)2021 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-33809867

RESUMO

While electrospun chitosan membranes modified to retain nanofibrous morphology have shown promise for use in guided bone regeneration applications in in vitro and in vivo studies, their mechanical tear strengths are lower than commercial collagen membranes. Elastin, a natural component of the extracellular matrix, is a protein with extensive elastic property. This work examined the incorporation of elastin into electrospun chitosan membranes to improve their mechanical tear strengths and to further mimic the native extracellular composition for guided bone regeneration (GBR) applications. In this work, hydrolyzed elastin (ES12, Elastin Products Company, USA) was added to a chitosan spinning solution from 0 to 4 wt% of chitosan. The chitosan-elastin (CE) membranes were examined for fiber morphology using SEM, hydrophobicity using water contact angle measurements, the mechanical tear strength under simulated surgical tacking, and compositions using Fourier-transform infrared spectroscopy (FTIR) and post-spinning protein extraction. In vitro experiments were conducted to evaluate the degradation in a lysozyme solution based on the mass loss and growth of fibroblastic cells. Chitosan membranes with elastin showed significantly thicker fiber diameters, lower water contact angles, up to 33% faster degradation rates, and up to seven times higher mechanical strengths than the chitosan membrane. The FTIR spectra showed stronger amide peaks at 1535 cm-1 and 1655 cm-1 in membranes with higher concentrated elastin, indicating the incorporation of elastin into electrospun fibers. The bicinchoninic acid (BCA) assay demonstrated an increase in protein concentration in proportion to the amount of elastin added to the CE membranes. In addition, all the CE membranes showed in vitro biocompatibility with the fibroblasts.


Assuntos
Materiais Biocompatíveis , Quitosana/química , Elastina/química , Membranas Artificiais , Animais , Proliferação de Células , Elasticidade , Fibroblastos/fisiologia , Camundongos , Estrutura Molecular , Células NIH 3T3 , Relação Estrutura-Atividade , Propriedades de Superfície , Resistência à Tração
20.
J Mech Behav Biomed Mater ; 119: 104474, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33887626

RESUMO

Three-point bending is often used during the mechanical determination of tissue material properties. When taken to failure, the test samples often experience high deformations. The objective of this study was to present beam and plate theories as analytical tools for determining tensile and compressive elastic moduli during the transition from flexure to membrane stress states. Samples of cartilage, a highly flexible connective tissue having differing tensile and compressive moduli, were tested. Three-point bending tests were conducted on auricular (ear) and costal (rib) cartilage harvested from pigs. The influence of span length variation and Poisson's ratio assumptions were statistically assessed. Tensile elastic moduli of the ear (3.886 MPa) and rib (6.131 MPa) were derived from high-deformation bending tests. The functional assessment described here can be applied as a design input approach for tissue reconstruction and tissue engineering, considering both hard and soft tissue applications.


Assuntos
Produtos Biológicos , Cartilagem , Animais , Costelas , Estresse Mecânico , Suínos , Resistência à Tração , Engenharia Tecidual
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