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1.
J Funct Biomater ; 5(4): 211-31, 2014 Oct 24.
Artículo en Inglés | MEDLINE | ID: mdl-25347356

RESUMEN

In this paper, we discuss the synthesis and self-assembling behavior of new copolymers derived from fatty acid/amino acid components, namely dimers of linoleic acid (DLA) and tyrosine derived diphenols containing alkyl ester pendent chains, designated as "R" (DTR). Specific pendent chains were ethyl (E) and hexyl (H). These poly(aliphatic/aromatic-ester-amide)s were further reacted with poly(ethylene glycol) (PEG) and poly(ethylene glycol methyl ether) of different molecular masses, thus resulting in ABA type (hydrophilic-hydrophobic-hydrophilic) triblock copolymers. We used Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies to evaluate the chemical structure of the final materials. The molecular masses were estimated by gel permeation chromatography (GPC) measurements. The self-organization of these new polymeric systems into micellar/nanospheric structures in aqueous environment was evaluated using ultraviolet/visible (UV-VIS) spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The polymers were found to spontaneously self-assemble into nanoparticles with sizes in the range 196-239 nm and critical micelle concentration (CMC) of 0.125-0.250 mg/mL. The results are quite promising and these materials are capable of self-organizing into well-defined micelles/nanospheres encapsulating bioactive molecules, e.g., vitamins or antibacterial peptides for antibacterial coatings on medical devices.

2.
J Biomed Mater Res B Appl Biomater ; 101(4): 532-40, 2013 May.
Artículo en Inglés | MEDLINE | ID: mdl-23296710

RESUMEN

Sterilization conditions need to be optimized to effectively neutralize the bioburden while using short exposure times for minimizing the changes in chemical composition, material properties and device architecture. Towards this goal, effects of ethylene oxide (EtO) exposure parameters such as time, temperature, humidity, and EtO concentration on the polymer properties were investigated by monitoring the changes in composition, and the morphology of different types of structures in a family of poly(ethylene glycol) (PEG)-containing tyrosine-derived polycarbonates. EtO was found to esterify the carboxyl groups present in the desaminotyrosyl-tyrosine groups. Sterilization under conditions more severe than those normally used reduced the glass transition temperature (Tg) and the molecular weight of the polymers, and the presence of PEG in the polymer enhanced this effect. Furthermore, electron micrographs showed that EtO sterilization cycle conditions, even those considered "mild," were found to damage the fragile structures such as those found in electrospun mats and porous scaffolds. Our study shows that the presence of EtO-susceptible groups, fusible architecture, and surface morphology should be taken into account in choosing the appropriate EtO sterilization conditions.


Asunto(s)
Materiales Biocompatibles/química , Óxido de Etileno/química , Polietilenglicoles/química , Tirosina/química , Cromatografía en Gel , Vidrio , Espectroscopía de Resonancia Magnética , Ensayo de Materiales , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Modelos Químicos , Peso Molecular , Porosidad , Esterilización , Estrés Mecánico , Temperatura , Factores de Tiempo
3.
Biomaterials ; 34(10): 2389-98, 2013 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-23312903

RESUMEN

Nanofiber scaffolds are effective for tissue engineering since they emulate the fibrous nanostructure of native extracellular matrix (ECM). Although electrospinning has been the most common approach for fabricating nanofiber scaffolds, airbrushing approaches have also been advanced for making nanofibers. For airbrushing, compressed gas is used to blow polymer solution through a small nozzle which shears the polymer solution into fibers. Our goals were 1) to assess the versatility of airbrushing, 2) to compare the properties of airbrushed and electrospun nanofiber scaffolds and 3) to test the ability of airbrushed nanofibers to support stem cell differentiation. The results demonstrated that airbrushing could produce nanofibers from a wide range of polymers and onto a wide range of targets. Airbrushing was safer, 10-fold faster, 100-fold less expensive to set-up and able to deposit nanofibers onto a broader range of targets than electrospinning. Airbrushing yielded nanofibers that formed loosely packed bundles of aligned nanofibers, while electrospinning produced un-aligned, single nanofibers that were tightly packed and highly entangled. Airbrushed nanofiber mats had larger pores, higher porosity and lower modulus than electrospun mats, results that were likely caused by the differences in morphology (nanofiber packing and entanglement). Airbrushed nanofiber scaffolds fabricated from 4 different polymers were each able to support osteogenic differentiation of primary human bone marrow stromal cells (hBMSCs). Finally, the differences in airbrushed versus electrospun nanofiber morphology caused differences in hBMSC shape where cells had a smaller spread area and a smaller volume on airbrushed nanofiber scaffolds. These results highlight the advantages and disadvantages of airbrushing versus electrospinning nanofiber scaffolds and demonstrate that airbrushed nanofiber scaffolds can support stem cell differentiation.


Asunto(s)
Células Madre Mesenquimatosas/citología , Nanofibras , Ingeniería de Tejidos/métodos , Diferenciación Celular/fisiología , Células Cultivadas , Humanos , Microscopía Electrónica de Rastreo , Células Madre/citología , Andamios del Tejido/química
4.
J Funct Biomater ; 3(1): 173-82, 2012 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-24956523

RESUMEN

Current methods for screening cell-material interactions typically utilize a two-dimensional (2D) culture format where cells are cultured on flat surfaces. However, there is a need for combinatorial and high-throughput screening methods to systematically screen cell-biomaterial interactions in three-dimensional (3D) tissue scaffolds for tissue engineering. Previously, we developed a two-syringe pump approach for making 3D scaffold gradients for use in combinatorial screening of salt-leached scaffolds. Herein, we demonstrate that the two-syringe pump approach can also be used to create scaffold gradients using a gas-foaming approach. Macroporous foams prepared by a gas-foaming technique are commonly used for fabrication of tissue engineering scaffolds due to their high interconnectivity and good mechanical properties. Gas-foamed scaffold gradient libraries were fabricated from two biodegradable tyrosine-derived polycarbonates: poly(desaminotyrosyl-tyrosine ethyl ester carbonate) (pDTEc) and poly(desaminotyrosyl-tyrosine octyl ester carbonate) (pDTOc). The composition of the libraries was assessed with Fourier transform infrared spectroscopy (FTIR) and showed that pDTEc/pDTOc gas-foamed scaffold gradients could be repeatably fabricated. Scanning electron microscopy showed that scaffold morphology was similar between the pDTEc-rich ends and the pDTOc-rich ends of the gradient. These results introduce a method for fabricating gas-foamed polymer scaffold gradients that can be used for combinatorial screening of cell-material interactions in 3D.

5.
Biomaterials ; 32(24): 5543-50, 2011 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-21609850

RESUMEN

We have recently reported on an ultrafast degrading tyrosine-derived terpolymer that degrades and resorbs within hours, and is suitable for use in cortical neural prosthetic applications. Here we further characterize this polymer, and describe a new tyrosine-derived fast degrading terpolymer in which the poly(ethylene glycol) (PEG) is replaced by poly(trimethylene carbonate) (PTMC). This PTMC containing terpolymer showed similar degradation characteristics but its resorption was negligible in the same period. Thus, changes in the polymer chemistry allowed for the development of two ultrafast degrading polymers with distinct difference in resorption properties. The in vivo tissue response to both polymers used as intraparenchymal cortical devices was compared to poly(lactic-co-glycolic acid) (PLGA). Slow resorbing, indwelling implant resulted in continuous glial activation and loss of neural tissue. In contrast, the fast degrading tyrosine-derived terpolymer that is also fast resorbing, significantly reduced both the glial response in the implantation site and the neuronal exclusion zone. Such polymers allow for brain tissue recovery, thus render them suitable for neural interfacing applications.


Asunto(s)
Materiales Biocompatibles/efectos adversos , Materiales Biocompatibles/metabolismo , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Polímeros/efectos adversos , Polímeros/metabolismo , Animales , Técnicas In Vitro , Ácido Láctico/efectos adversos , Ácido Láctico/metabolismo , Masculino , Poliésteres/efectos adversos , Poliésteres/metabolismo , Polietilenglicoles/efectos adversos , Polietilenglicoles/metabolismo , Ácido Poliglicólico/efectos adversos , Ácido Poliglicólico/metabolismo , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Ratas , Ratas Sprague-Dawley
6.
J Biomed Mater Res B Appl Biomater ; 86(1): 237-44, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-18161808

RESUMEN

BACKGROUND: The success of a biomaterial implant may be affected by the surface chemistry's impact on protein adsorption. We have developed a series of poly(ethylene glycol) (PEG) containing, tyrosine-derived polycarbonates, which have been rendered radio-opaque by the iodination of tyrosine units in the copolymer backbone for use in resorbable biomedical implants including vascular stents and grafts. We tested the hypothesis that protein adsorption along with seeding, growth, and migration of human aortic smooth muscle cells (SMC) and human aortic endothelial cells (EC) will be modified by the presence of iodine and PEG within the polymer composition. METHODS: Thin films of these polymers were prepared for the protein-material and cell-material interaction studies. Dot blot, SDS-PAGE, and XPS were used to evaluate relative protein adsorption. Cell adhesion and growth studies were performed using an MTS assay. Cell migration was evaluated using an injury model. RESULTS: The presence of PEG attenuated protein adsorption, cell adhesion, and growth. With the subsequent incorporation of iodine, protein adsorption markedly increased while the antiadhesive effect of PEG was counteracted by iodine for EC and SMC adhesion and SMC growth. CONCLUSION: Iodine incorporation into the polymer resulted in increased protein adsorption thus counteracting the effect of PEG.


Asunto(s)
Polietilenglicoles/química , Ingeniería de Tejidos/instrumentación , Ingeniería de Tejidos/métodos , Adsorción , Aorta/citología , Carbonatos/química , Adhesión Celular , Movimiento Celular , Proliferación Celular , Células Endoteliales/citología , Humanos , Yodo/química , Modelos Químicos , Miocitos del Músculo Liso/citología , Polímeros/química , Tirosina/química
7.
Langmuir ; 23(6): 3298-304, 2007 Mar 13.
Artículo en Inglés | MEDLINE | ID: mdl-17291015

RESUMEN

The hemocompatibility of polymeric vascular implants is in part dependent on the propensity of fibrinogen to adsorb to the implant surface. Fibrinogen surface adsorption was measured in real time using a quartz crystal microbalance with dissipation monitoring (QCM-D). Six new, biodegradable tyrosine-derived polycarbonates were used as test surfaces. Stainless steel, poly(L-lactic acid), poly(D,L-lactide-co-glycolide), and poly(ethylene terephthalate) surfaces served as controls and provided a comparison of the test surfaces with those of commonly used biomaterials. Our study addressed the question regarding to which extent systematic variations in polymer structure can be used to optimize X-ray visibility and provide tunable degradation rates while generating protein-repellant surface properties that minimize fibrinogen adsorption. QCM-D revealed surface-dependent changes in fibrinogen layer thickness (2 to 37 nm), adsorbed wet mass (0.2 to 4.3 microg/cm2), and viscosity (0.001 to 0.005 kg/ms). While we did not find an overall correlation between surface air-water contact angle measurements and fibrinogen adsorption (R2 = 0.08), our data demonstrate that gradually increasing the poly(ethylene glycol) content within a subgroup of polymers having the same polymer backbone will lead to decreased fibrinogen adsorption. Within this subgroup of polymers, there was a strong correlation between decreasing air-water contact angles and decreasing fibrinogen adsorption (R2 = 0.95). We conclude that it is possible to minimize fibrinogen adsorption to tyrosine-derived polycarbonates while optimizing X-ray visibility and degradation rates. Some of the tyrosine-derived polycarbonates were identified as useful materials for the design of blood-contacting implants on the basis of their substantially lower levels of fibrinogen adsorption relative to the commonly used controls.


Asunto(s)
Materiales Biocompatibles/química , Sangre/metabolismo , Desinfección/métodos , Fibrinógeno/química , Prótesis e Implantes , Esterilización/métodos , Adsorción , Desinfección/instrumentación , Elasticidad , Diseño de Equipo , Humanos , Cemento de Policarboxilato/química , Polímeros , Esterilización/instrumentación , Propiedades de Superficie , Tirosina/química , Viscosidad
8.
Langmuir ; 20(26): 11721-5, 2004 Dec 21.
Artículo en Inglés | MEDLINE | ID: mdl-15595803

RESUMEN

Biodegradable polymers capable of self-assembly into hollow nanospheres of less than 100 nm have significant potential for biotechnology applications such as drug delivery and gene therapy. Here we describe the synthesis of a novel ABA-type triblock copolymer made from a hydrophobic tyrosine-derived core and two hydrophilic poly(ethylene glycol) end groups (poly(ethylene glycol)-block-oligo(desaminotyrosyltyrosine octyl ester suberate)-block-poly(ethylene glycol)). We describe the self-assembly of this triblock copolymer and characterize its particles as 100 nm size vesicular nanospheres. The vesicular nature of these particles was determined by light scattering and electron microscopy. The nanospheres did not exhibit any short-term cytotoxicity toward UMR-106 cells at a concentration up to 2 mg/mL.


Asunto(s)
Nanoestructuras/química , Polietilenglicoles/química , Polietilenglicoles/farmacología , Línea Celular , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Microscopía Electrónica de Transmisión , Estructura Molecular , Nanoestructuras/toxicidad , Nanoestructuras/ultraestructura , Polietilenglicoles/síntesis química , Polietilenglicoles/toxicidad
9.
J Biomed Mater Res A ; 68(3): 496-503, 2004 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-14762929

RESUMEN

Numerous studies conclude that the selective adsorption of plasma proteins on materials contacting blood or tissue affects all subsequent interactions related to the biocompatibility of artificial surfaces. However, there are only a few studies available, which clearly demonstrate that there is a correlation between surface chemistry and selective protein adsorption. Detailed knowledge of such correlations would facilitate the design of biocompatible materials. In this study, a rapid, fluorescence-based, screening technique using a 384-well format for polymer-protein interactions was developed. The screening assay was used to measure the adsorption of human fibrinogen on 46 test polymers (44 polyarylates selected from a combinatorial library of tyrosine-derived polyarylates, and two lactide-based polymers). In this library of polyarylates, structural changes are generated by variations in either the polymer backbone or the polymer pendent chain. Although no overall trend between polymer hydrophobicity and fibrinogen adsorption could be identified using the entire set of test polymers (R(2) = 0.43), fibrinogen adsorption was clearly correlated with variations in the pendent chain structure. Thus, when the test polymers were grouped by backbone composition, increased hydrophobicity of the pendent chain was significantly correlated with reduced fibrinogen adsorption. The following R(2) coefficients within the polymer backbone groups were determined: 0.87 (diglycolates); 0.98 (glutarates); 0.73 (adipates); 0.87 (suberates); 0.67 (3-methyl-adipates). Our results demonstrate that it is possible to screen for protein-material interactions in a cost-effective fashion using a miniaturized immunofluorescence technique. Further, we demonstrate that small changes in chemical composition can significantly influence the adsorption of human fibrinogen on polymer surfaces. The lactide-based polymers were among those polymers exhibiting the highest tendency to adsorb fibrinogen. This information may be useful when polymers have to be selected for specific biomaterial applications.


Asunto(s)
Técnicas Químicas Combinatorias , Fibrinógeno/metabolismo , Técnica del Anticuerpo Fluorescente/métodos , Polímeros/química , Adsorción/efectos de los fármacos , Automatización , Evaluación Preclínica de Medicamentos/métodos , Técnica del Anticuerpo Fluorescente/normas , Humanos , Miniaturización , Polímeros/farmacología , Unión Proteica/efectos de los fármacos , Propiedades de Superficie
10.
J Pharm Sci ; 92(6): 1305-22, 2003 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-12761819

RESUMEN

Studies were previously conducted in our laboratory on the influence of n-alkanols, 1-alkyl-2-pyrrolidones, N,N-dimethlyalkanamides, and 1,2-alkanediols as skin permeation enhancers on the transport of a model permeant, corticosterone (CS). The experiments were conducted with hairless mouse skin (HMS) in a side-by-side, two-chamber diffusion cell, with enhancer present in an aqueous buffer in both chambers. The purpose of the present study was to extend these studies and investigate in greater detail the hypothesis that a suitable semipolar organic phase may mimic the microenvironment of the site of enhancer action, and that the enhancer partitioning tendency into this organic phase may be used to predict the enhancer potency. CS flux enhancement along the lipoidal pathway of HMS stratum corneum was determined with the 1-alkyl-2-azacycloheptanones, 1-alkyl-2-piperidinones, 1,2-dihydroxypropyl decanoate, 1,2-dihydroxypropyl octanoate, n-alkyl-beta-D-glucopyranosides, 2-(1-alkyl)-2-methyl-1,3-dioxolanes, 1,2,3-nonanetriol, and trans-hydroxyproline-N-decanamide-C-ethylamide as enhancers. Enhancement factors (E values) were calculated from the permeability coefficient and solubility data over a range of E values. Comparisons of the enhancer potencies for all studied homologous series and the carbon number of the n-alkyl group revealed a nearly semilogarithmic linear relationship with a slope of approximately 0.55, which is consistent with the hydrophobic effect. Moreover, comparisons of the enhancer potencies of all the enhancers with the n-hexanol-phosphate buffered saline (PBS), n-octanol-PBS, n-decanol-PBS, and n-hexane-PBS partition coefficients showed very good correlations for the n-alkanol solvents but not for n-hexane. This result supports the interpretation that the enhancer potency is directly related to the ability of the enhancer molecule to translocate to a site of action via its free energy of transfer from the bulk aqueous phase to a semipolar microenvironment in the stratum corneum lipid lamella that is well mimicked by water-saturated n-alkanols.


Asunto(s)
Adyuvantes Farmacéuticos/farmacología , Absorción Cutánea/efectos de los fármacos , Adyuvantes Farmacéuticos/química , Animales , Corticosterona/metabolismo , Epidermis/efectos de los fármacos , Epidermis/metabolismo , Hidrólisis , Técnicas In Vitro , Ratones , Ratones Pelados , Permeabilidad , Solubilidad , Relación Estructura-Actividad
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