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1.
Materials (Basel) ; 14(9)2021 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-33922889

RESUMO

The current study explores the effects of geometrical shapes of the infills on the 3D printed polylactic acid (PLA) plastic on the tensile properties. For this purpose, by utilizing an accessible supply desktop printer, specimens of diamond, rectangular, and hexagonal infill patterns were produced using the fused filament fabrication (FFF) 3D printing technique. Additionally, solid samples were printed for comparison. The printed tensile test specimens were conducted at environmental temperature, Ta of 23 °C and crosshead speed, VC.H of 5 mm/min. Mainly, this study focuses on investigating the percentage infill with respect to the cross-sectional area of the investigated samples. The mechanical properties, i.e., modulus of toughness, ultimate tensile stress, yield stress, and percent elongation, were explored for each sample having a different geometrical infill design. The test outcomes for each pattern were systematically compared. To further validate the experimental results, a computer simulation using finite element analysis was also performed and contrasted with the experimental tensile tests. The experimental results mainly suggested a brittle behavior for solidly infilled specimen, while rectangular, diamond, and hexagonal infill patterns showed ductile-like behavior (fine size and texture of infills). This brittleness may be due to the relatively higher infill density results that led to the high bonding adhesion of the printed layers, and the size and thickness effects of the solid substrate. It made the solidly infilled specimen structure denser and brittle. Among all structures, hexagon geometrical infill showed relative improvement in the mechanical properties (highest ultimate tensile stress and modulus values 1759.4 MPa and 57.74 MPa, respectively) compared with other geometrical infills. Therefore, the geometrical infill effects play an important role in selecting the suitable mechanical property's values in industrial applications.

2.
Molecules ; 25(16)2020 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-32781588

RESUMO

Bone regeneration for replacing and repairing damaged and defective bones in the human body has attracted much attention over the last decade. In this research, highly porous polyetheretherketone (PEEK)/hydroxyapatite (HA) bionanocomposite scaffolds reinforced with carbon fiber (CF) and carbon nanotubes (CNTs) were fabricated, and their structural, mechanical, and biological properties were studied in detail. Salt porogen (200-500 µm size) leaching methods were adapted to produce porous PEEK structures with controlled pore size and distribution, facilitating greater cellular infiltration and biological integration of PEEK composites within patient tissue. In biological tests, nanocomposites proved to be non-toxic and have very good cell viability. In addition, bone marrow cell growth was observed, and PEEK/HA biocomposites with carbon particles showed increased cell attachment over the neat PEEK/HA composites. In cell viability tests, bionanocomposites with 0.5 wt% CNTs established good attachment of cells on disks compared to neat PEEK/HA biocomposites. A similar performance was seen in culture tests of bone marrow cells (osteoblasts and osteoclasts). The 0.5 wt% CF for osteoblasts and 1 wt% CNTs for osteoclasts showed higher cell attachment. The addition of carbon-based nanomaterials into PEEK/HA has been identified as an effective approach to improve cell attachment as well as mechanical and biological properties. With confirmed cell attachment and sustained viability and proliferation of the fabricated PEEK/HA/CNTs, CF bionanocomposites were confirmed to possess excellent biocompatibility and will have potential uses in bone scaffolding and other biomedical applications.


Assuntos
Durapatita/química , Cetonas/química , Cetonas/farmacologia , Nanocompostos/química , Nanopartículas/química , Nanotubos de Carbono/química , Polietilenoglicóis/química , Polietilenoglicóis/farmacologia , Benzofenonas , Adesão Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Fenômenos Mecânicos , Osteoclastos/citologia , Osteoclastos/efeitos dos fármacos , Polímeros , Porosidade
3.
Prog Biomater ; 8(3): 211-221, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31630375

RESUMO

Bone regeneration is of great importance worldwide, because of various bone diseases, such as infections, tumors, and resultant fracture, birth defects, and bone loss due to trauma, explosion, or accident. Bone regeneration can be achieved by several materials and templates manufactured through various fabrication techniques. Uses of different materials and scaffold fabrication techniques have been explored over the past 20 years. In this research, polyetheretherketone (PEEK) was used to fabricate highly porous bionanocomposite foams for bone scaffolding. Melt casting and salt porogen (200-500 µm size) leaching methods were adapted to create an adequate pore size and the necessary percent of porosity, because pore size plays a vital role in cell implantation and growth. Porosity (75% and 85%) of the prepared scaffolds was adjusted by changing salt concentrations in the PEEK powder. Hydroxyapatite (HA) and carbon particles were used to improve cell attachments and interactions with the porous PEEK and to increase the mechanical properties of the scaffold materials. Carbon fiber (CF) and carbon nanotubes (CNTs) were uniformly dispersed into the PEEK powder before melt casting to enhance the mechanical properties and to observe the influence of the carbon particles on the properties of PEEK bionanocomposite foam. Compression test results of the fabricated bionanocomposites showed that HA and carbon particles are the potential filler materials for the enhancement of bionanocomposite mechanical properties. About 186% enhancement of compression modulus and 43% enhancement of yield strength were observed while incorporating only 0.5 wt% of CNTs into PEEK/HA bionanocomposites having 75% porosity, compared to PEEK/HA 20 wt% bionanocomposites. Micro-computed tomography (micro-CT) test results reveal that pore size and interconnectivity of the nanocomposite foams are in order and within the designed sizes. Mechanical tests proved that PEEK bionanocomposite foam has the potential for use in bone scaffolding and other biomedical applications.

4.
ACS Omega ; 4(3): 5044-5051, 2019 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-30949614

RESUMO

The interconnected porous structures that mimic the extracellular matrix support cell growth in tissue engineering. Nanofibers generated by electrospinning can act as a vehicle for therapeutic cell delivery to a neural lesion. The incorporation of carbon nanomaterials with excellent electrical conductivity in nanofibers is an attractive aspect for design of a nanodevice for neural tissue regeneration. In this study, nanoscaffolds were created by electrospinning poly(ε-caprolactone) (PCL) and three different types of carbon nanomaterials, which are carbon nanotubes, graphene, and fullerene. The component of carbon nanomaterials in nanofibers was confirmed by Fourier transform infrared spectroscopy. The fiber diameter was determined by scanning electron microscopy, and it was found that the diameter varied depending on the type of nanomaterial in the fibers. The incorporation of carbon nanotubes and graphene in the PCL fibers increased the contact angle significantly, while the incorporation of fullerene reduced the contact angle significantly. Incorporation of CNT, fullerene, and graphene in the PCL fibers increased dielectric constant. Astrocytes isolated from neonatal rats were cultured on PCL-nanomaterial nanofibers. The cell viability assay showed that the PCL-nanomaterial nanofibers were not toxic to the cultured astrocytes. The immunolabeling showed the growth and morphology of astrocytes on nanofiber scaffolds. SEM was performed to determine the cell attachment and interaction with the nanoscaffolds. This study indicates that PCL nanofibers containing nanomaterials are biocompatible and could be used for cell and drug delivery into the nervous system.

5.
ACS Omega ; 4(2): 4040-4048, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-30842986

RESUMO

Injectable thermosensitive hydrogels have been widely investigated for drug delivery systems. Chitosan (CH) is one of the most abundant natural polymers, and its biocompatibility and biodegradability make it a favorable polymer for thermosensitive hydrogel formation. The addition of nanoparticles can improve its drug release behavior, remote actuation capability, and biological interactions. Carbon nanotubes (CNTs) have been studied for the use in drug delivery systems, and they can act as drug delivery vehicles to improve the delivery of different types of therapeutic agents. In this work, carbon nanotubes were incorporated into a thermosensitive and injectable hydrogel formed by chitosan and ß-glycerophosphate (ß-GP) (CH-ß-GP-CNTs). The hybrid hydrogels loaded with methotrexate (MTX) were liquid at room temperature and became a solidified gel at body temperature. A number of tests including scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction were utilized to characterize the MTX-loaded CH-ß-GP-CNT hybrid hydrogels. The cell viability (alamarBlue) assay showed that hydrogels containing CNT (0.1%) were not toxic to the 3T3 cells. In vitro MTX release study revealed that CNT-containing hydrogels (with 0.1% CNT) demonstrated a decreased MTX releasing rate compared with control hydrogels without CNT. The cultured MCF-7 breast cancer cells were used to evaluate the efficacy of CH-ß-GP-CNT hybrid hydrogels delivering MTX on the control of tumor cell growth. Results demonstrated that CNT (0.1%) in the hydrogel enhanced the MTX antitumor function. Our study indicates that a thermosensitive CH-ß-GP-CNT hybrid hydrogel can be used as a potential breast cancer therapy system for controlled delivery of MTX.

6.
PLoS One ; 13(8): e0201345, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30091992

RESUMO

This study deals with the fabrication of polyacrylonitrile (PAN) nanofibers via an electrospinning process followed by stabilizing and carbonization in order to remove all non-carboneous matter and ensure a pure carboneous material. The as-spun PAN fibers were stabilized in air at 270°C for one hour and then carbonized at 750, 850, and 950°C in an inert atmosphere (argon) for another one hour. Differential scanning calorimetry and Raman spectroscopy were employed to determine the thermal and chemical properties of PAN. Surface features and morphologies of PAN-derived carbon nanofibers were investigated by means of scanning electron microscopy (SEM). SEM micrograms showed that fiber diameters were reduced after carbonization due to evolution of toxic gases and dehydrogenation. The Raman spectra of carbonized fibers manifested D/G peaks. The Raman spectroscopy peaks of 1100 and 500 cm-1 manifested the formation of γ phase and another peak at 900 cm-1 manifested the formation of α-phase. The water contact angle measurement of carbonized PAN fibers indicated that the nanofibers were superhydrophobic (θ > 150o) due to the formation of bumpy and pitted surface after carbonization. In DSC experiment, the stabilized fibers showed a broad exothermic peak at 308°C due to cyclization process. The mechanical andThermal analysis was used to ascertain mechanical properties of carbonized PAN fibers. PAN-derived carbon nanofibers possess excellent physica and mechanical properties and therefore, they may be suitable for many industrial applications such as energy, biomedical, and aerospace.


Assuntos
Resinas Acrílicas/química , Fibra de Carbono/química , Nanofibras/química , Varredura Diferencial de Calorimetria , Fibra de Carbono/ultraestrutura , Ciclização , Microscopia Eletrônica de Varredura , Nanofibras/ultraestrutura , Análise Espectral Raman , Propriedades de Superfície , Resistência à Tração
7.
J Biomed Mater Res A ; 105(9): 2381-2390, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28445606

RESUMO

Chitosan has the ability to make injectable thermosensitive hydrogels which has been highly investigated for drug delivery applications. The addition of nanoparticles is one way to increase the mechanical strength of thermosensitive chitosan hydrogel and subsequently and control the burst release of drug. Graphene nanoparticles have shown unique mechanical, optical and electrical properties which can be exploited for biomedical applications, especially in drug delivery. This study, have focused on the mechanical properties of a thermosensitive and injectable hybrid chitosan hydrogel incorporated with graphene nanoparticles. Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD) have been used for morphological and chemical characterization of graphene infused chitosan hydrogels. The cell viability and cytotoxicity of graphene-contained hydrogels were analyzed using the alamarBlue® technique. In-vitro methotrexate (MTX) release was investigated from MTX-loaded hybrid hydrogels as well. As a last step, to evaluate their efficiency as a cancer treatment delivery system, an in vitro anti-tumor test was also carried out using MCF-7 breast cancer cell lines. Results confirmed that a thermosensitive chitosan-graphene hybrid hydrogel can be used as a potential breast cancer therapy system for controlled delivery of methotrexate. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2381-2390, 2017.


Assuntos
Quitosana/química , Sistemas de Liberação de Medicamentos , Grafite/química , Hidrogéis/química , Temperatura , Células 3T3 , Animais , Antineoplásicos/farmacologia , Morte Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Liberação Controlada de Fármacos , Cinética , Metotrexato/farmacologia , Camundongos , Espectroscopia de Infravermelho com Transformada de Fourier
8.
J Biomater Appl ; 30(1): 38-49, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25638169

RESUMO

Albumin-based drug-carrying micro-composite spheres were fabricated and studied to evaluate their potentials for breast cancer treatment. Magnetic nanoparticles and albumin were incorporated within poly(D l-lactide-co-glycolide) microspheres to increase accumulation of the microspheres at the target site. Two chemotherapeutics, cyclophosphamide and 5-fluorouracil, were encapsulated into the microspheres. The drug-release study revealed an initial burst of drug and then sustained release by diffusion. A Fourier transform infrared spectroscopy study confirmed the presence of all components of the drug delivery system. An in vitro study using fibroblast cells (3T3) and breast cancer cells (MDA-486) exhibited an effective cytotoxicity behavior when exposed to the drug delivery system in a dose- and time-dependent manner. The therapeutic influence of the drug delivery system was evaluated in vivo using a nude mouse breast cancer model. A continuous decrease in tumor size was observed in groups treated with microspheres containing the chemotherapeutics, whereas mice treated with direct chemotherapy without drug delivery system showed less efficacy and suggested tumor relapse after cessation of treatment. The enhanced therapeutic influence of the drug delivery system may be attributed to the increased uptake of the microspheres by malignant cells due to the presence of albumin and magnetic force. The bioavailability of chemotherapeutics at the target site was further increased due to the sustained release of the drugs by diffusion following the burst release. Continuous investigations will optimize the size of the drug delivery system and portions of the target driving-force components (magnetic nanoparticles and albumin) in the drug delivery system to maximize its therapeutic efficacy and minimize potential long-term side effects.


Assuntos
Antineoplásicos/administração & dosagem , Neoplasias da Mama/tratamento farmacológico , Mama/efeitos dos fármacos , Ciclofosfamida/administração & dosagem , Portadores de Fármacos/química , Fluoruracila/administração & dosagem , Albumina Sérica/química , Células 3T3 , Animais , Antineoplásicos/uso terapêutico , Mama/patologia , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Ciclofosfamida/uso terapêutico , Sistemas de Liberação de Medicamentos , Feminino , Fluoruracila/uso terapêutico , Humanos , Nanopartículas de Magnetita/química , Camundongos , Camundongos Nus
9.
Materials (Basel) ; 8(10): 7017-7031, 2015 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-28793615

RESUMO

This paper presents an idea of using carbonized electrospun Polyacrylonitrile (PAN) fibers as a sensor material in a structural health monitoring (SHM) system. The electrospun PAN fibers are lightweight, less costly and do not interfere with the functioning of infrastructure. This study deals with the fabrication of PAN-based nanofibers via electrospinning followed by stabilization and carbonization in order to remove all non-carbonaceous material and ensure pure carbon fibers as the resulting material. Electrochemical impedance spectroscopy was used to determine the ionic conductivity of PAN fibers. The X-ray diffraction study showed that the repeated peaks near 42° on the activated nanofiber film were α and ß phases, respectively, with crystalline forms. Contact angle, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were also employed to examine the surface, thermal and chemical properties of the carbonized electrospun PAN fibers. The test results indicated that the carbonized PAN nanofibers have superior physical properties, which may be useful for structural health monitoring (SHM) applications in different industries.

10.
Biotechnol J ; 9(1): 163-70, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24106002

RESUMO

A novel drug delivery system incorporating human serum albumin, poly(lactic-co-glycolic acid, magnetite nanoparticles, and therapeutic agent(s) was developed for potential application in the treatment of diseases such as rheumatoid arthritis and skin cancer. An oil-in-oil emulsion/solvent evaporation (O/OSE) method was modified to produce a drug delivery system with a diameter of 0.5­2 µm. The diameter was mainly controlled by adjusting the viscosity of albumin in the discontinuous phase of the O/OSE method. The drug-release study showed that the release of drug and albumin was mostly dependent on the albumin content of the drug delivery system, which is very similar to the drug occlusion-mesopore model. Cytotoxicity tests indicated that increasing the albumin content in the drug delivery system increased cell viability, possibly due to the improved biocompatibility of the system. Overall, these studies show that the proposed system could be a viable option as a drug delivery system in the treatment of many illnesses, such as rheumatoid arthritis, and skin and breast cancers.


Assuntos
Sistemas de Liberação de Medicamentos/efeitos adversos , Sistemas de Liberação de Medicamentos/métodos , Nanocompostos/química , Albumina Sérica/farmacocinética , Animais , Linhagem Celular , Emulsões , Humanos , Ácido Láctico/administração & dosagem , Nanopartículas de Magnetita/administração & dosagem , Nanopartículas de Magnetita/química , Metotrexato/administração & dosagem , Camundongos , Modelos Moleculares , Nanocompostos/uso terapêutico , Ácido Poliglicólico/administração & dosagem , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Albumina Sérica/administração & dosagem
11.
Biomacromolecules ; 15(1): 319-26, 2014 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-24304204

RESUMO

Nanofiber-based scaffolds may simultaneously provide immediate contact guidance for neural regeneration and act as a vehicle for therapeutic cell delivery to enhance axonal myelination. Additionally, nanofibers can serve as a neuron-free model to study myelination of oligodendrocytes. In this study, we fabricated nanofibers using a polycaprolactone and gelatin copolymer. The ratio of the gelatin component in the fibers was confirmed by energy dispersive X-ray spectroscopy. The addition of gelatin to the polycaprolactone (PCL) for nanofiber fabrication decreased the contact angle of the electrospun fibers. We showed that both polycaprolactone nanofibers as well as polycaprolactone and gelatin copolymer nanofibers can support oligodendrocyte precursor cell (OPC) growth and differentiation. OPCs maintained their phenotype and viability on nanofibers and were induced to differentiate into oligodendrocytes. The differentiated oligodendrocytes extend their processes along the nanofibers and ensheathed the nanofibers. Oligodendrocytes formed significantly more myelinated segments on the PCL and gelatin copolymer nanofibers than those on PCL nanofibers alone.


Assuntos
Proliferação de Células , Nanofibras/química , Fibras Nervosas Mielinizadas/fisiologia , Oligodendroglia/fisiologia , Células-Tronco/fisiologia , Engenharia Tecidual/métodos , Animais , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Nanofibras/administração & dosagem , Neurônios , Oligodendroglia/efeitos dos fármacos , Ratos , Células-Tronco/efeitos dos fármacos
12.
Membranes (Basel) ; 3(4): 375-88, 2013 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-24957063

RESUMO

Polymeric nanofiber membranes of polyvinyl chloride (PVC) blended with polyvinylpyrrolidone (PVP) were fabricated using an electrospinning process at different conditions and used for the filtration of three different liquid suspensions to determine the efficiency of the filter membranes. The three liquid suspensions included lake water, abrasive particles from a water jet cutter, and suspended magnetite nanoparticles. The major goal of this research work was to create highly hydrophilic nanofiber membranes and utilize them to filter the suspended liquids at an optimal level of purification (i.e., drinkable level). In order to overcome the fouling/biofouling/blocking problems of the membrane, a coagulation process, which enhances the membrane's efficiency for removing colloidal particles, was used as a pre-treatment process. Two chemical agents, Tanfloc (organic) and Alum (inorganic), were chosen for the flocculation/coagulation process. The removal efficiency of the suspended particles in the liquids was measured in terms of turbidity, pH, and total dissolved solids (TDS). It was observed that the coagulation/filtration experiments were more efficient at removing turbidity, compared to the direct filtration process performed without any coagulation and filter media.

13.
Langmuir ; 27(2): 504-7, 2011 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-21171580

RESUMO

Polystyrene (PS) and polyvinyl chloride (PVC) fibers incorporated into TiO(2) nanoparticles and graphene nanoflakes were fabricated by an electrospinning technique, and then the surface morphology and superhydrophobicity of these electrospun nanocomposite fibers were investigated. Results indicated that the water contact angle of the nanocomposite fiber surfaces increases to 178° on the basis of the fiber diameter, material type, nanoscale inclusion, heat treatment, and surface porosity/roughness. This is a result of the formation of the Cassie-Baxter state in the fibers via the nanoparticle decoration, bead formation, and surface energy of the nanofiber surface. Consequently, these superhydrophobic nanocomposite fibers can be utilized in designing photoelectrodes of dye-sensitized solar cells (DSSCs) as self-cleaning and anti-icing materials for the long-term efficiency of the cells.


Assuntos
Interações Hidrofóbicas e Hidrofílicas , Nanopartículas/química , Poliestirenos/química , Cloreto de Polivinila/química , Titânio/química , Grafite/química , Temperatura Alta , Tamanho da Partícula , Porosidade , Propriedades de Superfície
14.
J Colloid Interface Sci ; 354(2): 448-54, 2011 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-21144531

RESUMO

Dielectrophoresis (DEP) force-assisted assembly of a colloidal single photonic-crystal monolayer in a microfluidic chamber was demonstrated. Negative DEP force with a high-frequency AC electric field induced the compression of colloidal microspheres to form a colloidal crystal domain at the center of a hexapolar-shaped electrode. While typical assembly by monotonic DEP force forms multicrystalline domains containing crystal defects, repetitions of the DEP/relaxation cycle significantly facilitated crystal growth of 10µm monodispersed polystyrene microspheres, allowing a grain-boundary-free single-crystal monolayer domain of ca. 200µm in size. Microsphere size as well as size distribution affected the formation of the single-crystal domain. A simple method was used to immobilize the single-crystal domain on the glass substrate without losing its crystallinity.

15.
Langmuir ; 27(2): 782-91, 2011 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-21162522

RESUMO

Mechanically durable, long-lasting antifog coatings based on polysaccharides were developed using a layer-by-layer (LBL) assembly process. The unique properties of these coatings are a result of a molecular-level blending of the polysaccharides, with multilayers containing chitosan and carboxymethyl cellulose providing the best overall properties. The antifog properties resulted from a strong interaction between the polar and H-bonding elements of the assembled polymers and water molecules and the concomitant formation of thin films of water. Environmental scanning electron microscopy (ESEM) studies confirmed that fogging coatings are decorated with light scattering, micrometer-sized droplets of water whereas antifogging coatings remain droplet free. To improve the mechanical durability of the multilayer films on substrates, the surface was modified via self-assembly of epoxy-functionalized silane molecules. Cross-linking chemistry was then applied to improve the mechanical robustness of the LBL films on various surfaces. These films were characterized using several techniques: optical profilometery (PL), spectroscopic ellipsometry (EL), contact angle goniometry (CA), and atomic force microscopy (AFM). The antifog properties of the films were evaluated by several tests under different environmental conditions. This work demonstrates that the unique water-adsorbing properties of polysaccharides can be exploited to create permanent antifog properties, which may be useful for various applications.


Assuntos
Materiais Revestidos Biocompatíveis/química , Membranas Artificiais , Polissacarídeos/química , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Cinética , Tamanho da Partícula , Propriedades de Superfície , Água/química
16.
Biotechnol J ; 3(2): 252-63, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18034436

RESUMO

Measurement of the real dielectric constant of bulk buffer solutions containing short sequences of DNA as a function of temperature through the DNA melting or denaturiztion transition can be used to determine melting temperatures, T(m), and to estimate the binding energy of the complimentary strands. We describe a preliminary dielectric measurement and analysis protocol to determine these parameters and its application to two known short sequences. The relative real dielectric constant for the bulk solutions was determined over the frequency range of 50 Hz-20 kHz and temperature range of <40-65 degrees C. The measurements were performed on dilute solutions and utilized low electric field strengths. Based on fits to the data by modified sigmoid functions, the melting temperatures, width of transition, and binding energy for the two sequences in solution were estimated. It was observed that the order of the transition appeared to be second order. The results were then compared against predictions of a number of models from the literature that provide theoretical estimates for the melting temperatures of known short sequences of DNA.


Assuntos
DNA/química , Eletroquímica/métodos , Desnaturação de Ácido Nucleico , Temperatura de Transição , Algoritmos , Eletroquímica/instrumentação , Soluções/química , Termodinâmica
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