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1.
Materials (Basel) ; 15(8)2022 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-35454466

RESUMO

Road pavement thickness and their depth of construction take a chunk of the overall cost of road construction. This has called for a need for reduced road pavement thickness by improving the engineering properties of subgrade such as the California bearing ratio (CBR). The CBR of road subgrade has been a major determining factor for road pavement thickness, and expansive subgrades generally have a low CBR, resulting in major road defects. In this study, road pavement thickness and construction depth optimization were conducted using the CBR values achieved in this study. Additives proportions of 8% lime and 20% cement were used in expansive subgrade to improve their engineering properties, making them suitable for use in road construction. The study investigated the characteristics, mineral structure, Atterberg limit, compaction, CBR, swell and microstructural properties of expansive subgrade. The results show a reduction in road pavement thickness and a construction depth with an increase in CBR value. All CBR values for treated samples were above 2%, making them usable in road construction. A reduction in swell potential up to 0.04% was observed for treated expansive subgrade. The study concluded that pavement thickness and construction depth can be reduced by enhancing subgrade materials and using cement and lime as binders.

2.
Hand (N Y) ; 12(4): 382-388, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28644935

RESUMO

BACKGROUND: The aim of this review was to further define the clinical condition triquetrohamate (TH) impaction syndrome (THIS), an entity underreported and missed often. Its presentation, physical findings, and treatment are presented. METHODS: Between 2009 and 2014, 18 patients were diagnosed with THIS. The age, sex, hand involved, activity responsible for symptoms, and defining characteristics were recorded. The physical findings, along with ancillary studies, were reviewed. Delay in diagnosis and misdiagnoses were assessed. Treatment, either conservative or surgical, is presented. Follow-up outcomes are presented. RESULTS: There were 15 male and 3 females, average age of 42 years. Two-handed sports such as golf and baseball accounted for more than 60% of the cases, and these cases were the only ones that involved the lead nondominant hand, pain predominantly at impact. Delay in diagnosis averaged greater than 7 months, with triangular fibrocartilage (TFCC) and extensor carpi ulnaris (ECU) accounting for more than 50% of misdiagnoses. Physical findings of note included pain over the TH joint, worse with passive dorsiflexion and ulnar deviation. Radiographic findings are described. Instillation of lidocaine with the wrist in radial deviation under fluoroscopic imaging with relief of pain helped to confirm the diagnosis. Conservative treatment was successful in 9 of 18 patients (50%), whereas in the remaining, surgical intervention allowed approximately 80% return to full activities without limitation. CONCLUSION: Triquetrohamate impaction syndrome remains an underreported and often unrecognized cause of ulnar-sided wrist pain. In this report, the largest series to date, its presentation, defining characteristics, and treatment options are further elucidated.


Assuntos
Dor Crônica/fisiopatologia , Hamato/fisiopatologia , Artropatias/fisiopatologia , Piramidal/fisiopatologia , Adolescente , Adulto , Traumatismos em Atletas/fisiopatologia , Tratamento Conservador/estatística & dados numéricos , Diagnóstico Tardio , Feminino , Hamato/diagnóstico por imagem , Hamato/cirurgia , Humanos , Artropatias/diagnóstico , Artropatias/terapia , Masculino , Pessoa de Meia-Idade , Procedimentos Ortopédicos/estatística & dados numéricos , Recuperação de Função Fisiológica , Piramidal/diagnóstico por imagem , Piramidal/cirurgia , Adulto Jovem
3.
J Craniofac Surg ; 22(1): 285-8, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21239920

RESUMO

INTRODUCTION: Intracranial hypertension due to craniosynostosis is a dreaded potential complication that affects the developing brain. We hypothesized that craniosynostotic patients have significantly reduced jugular foramen (JF) when compared with age-matched controls. This may partially account for the observed increase in intracranial pressure (ICP) seen in some of these patients. We also estimated the potential effects on ICP using the Hagen-Poiseuille equation. MATERIALS AND METHODS: Two institutional review board-approved groups were included in this study. Group 1 consists of 14 randomly selected craniosynostotic patients (7 boys and 7 girls; mean age, 9.33 mo; range, 0.6-21 mo). Group 2, the control group, consists of 27 children without craniosynostosis (13 boys and 14 girls; mean age, 8.71 mo; range, 0.23-45 mo). The same neuroradiologist used axial computed tomographic scans to measure the greatest anterior-posterior (AP) and lateral diameters of the jugular bulb. RESULTS: The right JF AP diameter is 23.02% smaller in group 1 than in group 2 (P = 0.0066, 2-tailed t-test). The left JF AP diameter was also smaller for group 1 but was not statistically significant (P = 0.257, 2-tailed t-test). Group 1 also had a nonsignificant increase in both lateral diameters (P > 0.05). DISCUSSION: The study showed a significant decrease (23.02%) in the right JF AP dimension in children with craniosynostosis. On the basis of the Hagen-Poiseuille equation, a 23.02% AP diameter reduction in 1 JF may theoretically increase the ICP 63.5% or 6.35 mm Hg, keeping all other variables, such as blood flow, constant. Although not supported by aspect ratio analysis, the slight increase in the lateral diameters of the patients' JFs may lessen this effect.


Assuntos
Craniossinostoses/complicações , Hipertensão Intracraniana/etiologia , Veias Jugulares/diagnóstico por imagem , Estudos de Casos e Controles , Pré-Escolar , Craniossinostoses/diagnóstico por imagem , Craniossinostoses/fisiopatologia , Feminino , Humanos , Lactente , Hipertensão Intracraniana/diagnóstico por imagem , Hipertensão Intracraniana/fisiopatologia , Veias Jugulares/fisiopatologia , Masculino , Tomografia Computadorizada por Raios X
4.
J Colloid Interface Sci ; 351(1): 190-6, 2010 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-20708740

RESUMO

In dilute aqueous solution unimers of copolymer F127 (E(98)P(67)E(98)) associate to form micelles, and in more concentrated solution micelles pack to form high-modulus gels. Cosolvents are known to affect these processes, and ethanol/water mixtures have been of particular interest. Dynamic light scattering from dilute solutions was used to confirm micellization, but major attention was directed towards the gels. Visual observation of mobility (tube inversion) was used to detect gel formation, oscillatory rheometry to confirm gel formation and provide values of the elastic moduli over a wide temperature range, and small-angle X-ray scattering to determine gel structure. The solvents were limited to 10, 20 and 30 wt.% ethanol/water. Critical concentrations for gel formation were similar for 10 and 20 wt.% ethanol/water but were significantly increased for 30 wt.% ethanol/water, e.g. at T=45 degrees C from c approximately 15 wt.% to c approximately 28 wt.%. The elastic moduli reached maximum values at T approximately 50 degrees C: e.g. G' approximately 25 kPa for 25 wt.% F127 in 10 and 20 wt.% ethanol/water and a similar value for 30 wt.% F127 in 30 wt.% ethanol/water. Hard gels of 30 and 35 wt.% F127 in ethanol/water at 25 and 40 degrees C had the body-centered cubic (bcc) structure.


Assuntos
Etanol/química , Poloxâmero/química , Géis/química , Micelas , Soluções , Propriedades de Superfície , Temperatura , Água/química
5.
Langmuir ; 25(24): 13776-83, 2009 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-19572512

RESUMO

Gel diagrams based on tube inversion and oscillatory rheometry are reported for Pluronic copolymers F127 (E(98)P(67)E(98)) and P123 (E(21)P(67)E(21)) in mixtures with anionic surfactant sodium dodecyl sulfate (SDS). Total concentrations (c, SDS+copolymer) were as high as 50 wt % with mole ratios SDS/copolymer (mr) in the ranges 1-5 (F127) and 1-7 (P123). Temperatures were as high as 90 degrees C. Determination of the temperature dependences of the dynamic moduli served to confirm the gel boundaries from tube inversion and to reveal the high elastic moduli of the gels, e.g., compared at comparable positions in the gel phase, a 50 wt % SDS/P123 with mr = 7 had G' three times that of a corresponding gel of P123 alone. Small-angle X-ray scattering (SAXS) was used to show that the structures of all the SDS/F127 gels were bcc and that the structures of the SDS/P123 gels with mr = 1 were either fcc (c = 30 wt %) or hex (c = 40 wt %). Assignment of structures to SDS/P123 gels with values of mr in the range 3-7 was more difficult, as high-order scattering peaks could be very weak, and at the higher values of c and mr, the SAXS peaks included multiple reflections.

6.
Int J Pharm ; 378(1-2): 211-4, 2009 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-19501147

RESUMO

The solubilisation of two poorly soluble flavonoids, quercetin and rutin, in micellar solutions of mixtures of a block copolymer of ethylene oxide and styrene oxide (E(137)S(18)E(137)) with one of ethylene oxide and propylene oxide (E(62)P(39)E(62)) has been studied at 25 and 37 degrees C. Solubilisation capacities were higher than those for the model poorly water-soluble drug griseofulvin and comparable with published values for the solubilisation of rutin by beta-cyclodextrin.


Assuntos
Griseofulvina/química , Polímeros/química , Quercetina/química , Rutina/química , Antioxidantes/administração & dosagem , Antioxidantes/química , Compostos de Epóxi/química , Óxido de Etileno/química , Griseofulvina/administração & dosagem , Micelas , Quercetina/administração & dosagem , Rutina/administração & dosagem , Solubilidade , Temperatura , beta-Ciclodextrinas/química
7.
Waste Manag ; 29(2): 804-11, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18835151

RESUMO

Quantification and characterization of medical waste generated in healthcare facilities (HCFs) in a developing African nation has been conducted to provide insights into existing waste collection and disposal approaches, so as to provide sustainable avenues for institutional policy improvement. The study, in Ibadan city, Nigeria, entailed a representative classification of nearly 400 healthcare facilities, from 11 local government areas (LGA) of Ibadan, into tertiary, secondary, primary, and diagnostic HCFs, of which, 52 HCFs were strategically selected. Primary data sources included field measurements, waste sampling and analysis and a questionnaire, while secondary information sources included public and private records from hospitals and government ministries. Results indicate secondary HCFs generate the greatest amounts of medical waste (mean of 10,238 kg/day per facility) followed by tertiary, primary and diagnostic HCFs, respectively. Characterised waste revealed that only approximately 3% was deemed infectious and highlights opportunities for composting, reuse and recycling. Furthermore, the management practices in most facilities expose patients, staff, waste handlers and the populace to unnecessary health risks. This study proffers recommendations to include (i) a need for sustained cooperation among all key actors (government, hospitals and waste managers) in implementing a safe and reliable medical waste management strategy, not only in legislation and policy formation but also particularly in its monitoring and enforcement and (ii) an obligation for each HCF to ensure a safe and hygienic system of medical waste handling, segregation, collection, storage, transportation, treatment and disposal, with minimal risk to handlers, public health and the environment.


Assuntos
Eliminação de Resíduos de Serviços de Saúde/métodos , Eliminação de Resíduos de Serviços de Saúde/estatística & dados numéricos , Coleta de Dados , Instalações de Saúde , Eliminação de Resíduos de Serviços de Saúde/normas , Nigéria , Inquéritos e Questionários , Transportes
8.
Environ Geochem Health ; 31(2): 315-25, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19023666

RESUMO

Preliminary mineral magnetic results from a pilot project investigating the suitability of roadside tree leaves as depositories of vehicular pollution are presented. Tree leaf surfaces (Lime: Tilia europaea; Sycamore: Acer pseudoplatanus) at four roadside and one woodland location in Wolverhampton, UK, have been monitored (July 2003 to November 2003). Mineral magnetic technologies have revealed spatial variations of particulate pollution concentration throughout the conurbation and data analysis indicates that magnetic concentration parameters are suitable proxies for fine particulate pollution, which are particularly hazardous to health. Site-specific traffic management and associated vehicle behaviour appear to be chiefly responsible for the magnetic concentration differences between sites. Magneto-biomonitoring in this way allows the high-resolution spatial mapping of particulate matter (PM) pollution, which may also benefit epidemiology in better assessing exposure to vehicular-derived particulates. Given the speed, measurement sensitivity and non-destructive nature of the technique, it is proposed that this low-cost approach offers some advantages over centralised monitoring stations to monitor urban roadside particulate pollution.


Assuntos
Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Folhas de Planta/química , Emissões de Veículos/análise , Acer/química , Cidades , Inglaterra , Magnetismo , Tamanho da Partícula , Tilia/química
9.
Int J Pharm ; 369(1-2): 196-8, 2009 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-19041381

RESUMO

The influence of hydrophobic-block length on solubilisation capacity was examined for micelles of E(m)B(n) copolymers (E=oxyethylene, B=oxybutylene, subscripts denote number-average block lengths in repeat units) with B-block lengths in the range of 30-76 and with E-blocks of sufficient length to ensure the formation of spherical micelles. Griseofulvin was used as a model poorly-water-soluble drug known to be almost exclusively solubilised in the micellar core. Combination of solubilisation data with those of a previous study has shown that the amount of drug solubilised per gram of hydrophobe is essentially independent of B-block length when this exceeds about 15 B units, suggesting that core size is not a major influence on solubilisation.


Assuntos
Compostos de Epóxi/química , Óxido de Etileno/química , Griseofulvina/química , Micelas , Interações Hidrofóbicas e Hidrofílicas , Polímeros/química , Solubilidade
10.
Langmuir ; 24(21): 12260-6, 2008 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-18844386

RESUMO

In certain applications copolymer P123 (E21P67E21) is dissolved in water-ethanol mixtures, initially to form micellar solutions and eventually to gel. For P123 in 10, 20, and 30 wt % aqueous ethanol we used dynamic light scattering from dilute solutions to confirm micellization, oscillatory rheometry, and visual observation of mobility (tube inversion) to determine gel formation in concentrated solutions and small-angle X-ray scattering (SAXS) to determine gel structure. Except for solutions in 30 wt % aqueous ethanol, a clear-turbid transition was encountered on heating dilute and concentrated micellar solutions alike, and as for solutions in water alone (Chaibundit et al. Langmuir 2007, 23, 9229) this could be ascribed to formation of wormlike micelles. Dense clouding, typical of phase separation, was observed at higher temperatures. Regions of isotropic and birefringent gel were defined for concentrated solutions and shown (by SAXS) to have cubic (fcc and hcp) and hexagonal structures, consistent with packed spherical and elongated micelles, respectively. The cubic gels (0, 10, and 20 wt % ethanol) were clear, while the hex gels were either turbid (0 and 10 wt % ethanol), turbid enclosing a clear region (20 wt % ethanol), or entirely clear (30 wt % ethanol). The SAXS profile was unchanged between turbid and clear regions of the 20 wt % ethanol gel. Temperature scans of dynamic moduli showed (as expected) a clear distinction between high-modulus cubic gels (G'max approximately 20-30 kPa) and lower modulus hex gels (G'max<10 kPa).

11.
Int J Pharm ; 362(1-2): 193-6, 2008 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-18585447

RESUMO

The dependence of log(cmc) on hydrophobic block length n was examined for E(m)B(n) copolymers (E=oxyethylene, B=oxybutylene, subscripts denote number-average block lengths in repeat units) with n in the range 30-76. Combination with published data for E(m)B(n) diblock copolymers with shorter E-blocks shows two changes of slope in the log(cmc)-n plot corresponding to the onset of unimolecular micelle formation at n approximately 12 and completion of this process at n approximately 30. The results are discussed with reference to published data for E(m)L(n) and E(m)CL(n) (L from d,L-lactide; CL from epsilon-caprolactone) copolymers, which show similar behaviour.


Assuntos
Portadores de Fármacos/química , Compostos de Epóxi/química , Micelas , Polietilenoglicóis/química , Fenômenos Químicos , Química Farmacêutica , Físico-Química , Solubilidade , Soluções , Água
12.
Int J Pharm ; 358(1-2): 303-6, 2008 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-18417305

RESUMO

The solubilisation of two poorly soluble drugs, furosemide and nabumetone, in micellar solutions of diblock copolymers of ethylene oxide and styrene oxide has been studied at 25 and 37 degrees C and solubilisation capacities compared with published values for griseofulvin and docetaxel. Solubilisation in the micelle core, corrected for the different proportions of poly(styrene oxide) in the copolymers, was similar for all four drugs. The highest solubilisation capacities were found for a copolymer with worm-like micelles.


Assuntos
Polietilenoglicóis/química , Poliestirenos/química , Butanonas/química , Furosemida/química , Espectroscopia de Ressonância Magnética , Micelas , Nabumetona , Preparações Farmacêuticas/química , Soluções Farmacêuticas , Polímeros , Solubilidade , Espectrofotometria Ultravioleta
13.
Int J Pharm ; 354(1-2): 82-7, 2008 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-18063326

RESUMO

Ethylene oxide and 1,2-butylene oxide were sequentially polymerised to form the diblock copolymer E13B10 (E=oxyethylene, B=oxybutylene, subscripts denote number-average block lengths in repeat units). Dynamic and static light scattering over the temperature range 10-30 degrees C demonstrated a transition from compact (spheroidal) micelles to larger, more elongated (worm-like) micelles with temperature increase above a critical onset temperature of about 20 degrees C. Determination of the solubilisation capacity for griseofulvin, carbamazepine and spironolactone of dilute micellar solutions of this copolymer, together with those of E11B8 and E17B12 block copolymers (which also show the sphere-to-worm transition), allowed investigation of the influence on solubilisation characteristics of hydrophobic block length and temperature. The extent of solubilisation at 25 degrees C of the poorly water-soluble drug spironolactone increased linearly with increase of hydrophobic block length, attributable to a concomitant increase in the proportion of worm-like micelles in solution.


Assuntos
Carbamazepina/química , Griseofulvina/química , Micelas , Polímeros/química , Espironolactona/química , Compostos de Epóxi/química , Óxido de Etileno/química , Luz , Soluções Farmacêuticas , Espalhamento de Radiação , Solubilidade , Temperatura , Água
14.
Expert Opin Drug Deliv ; 4(5): 533-46, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17880275

RESUMO

It is thought that almost half of potentially useful drug candidates fail to progress to formulation development because of their low aqueous solubility and associated poor or erratic absorption characteristics. A response to this challenge has been the development of a variety of colloidal delivery systems in which the therapeutic agent is encapsulated in nanosized particles. In this review, attention is focussed on colloidal vectors based on amphiphilic block copolymers, the micelles of which can accommodate a wide range of water-insoluble guest molecules, and particularly on copolymers with poly(oxyethylene) as the hydrophilic block and with poly(oxyalkylene) or polyester hydrophobic blocks, taking advantage of the 'stealth' properties of the poly(oxyethylene) corona of their micelles. Although copolymers of this type have been commercially available for several decades in the form of the Pluronic (BASF) polyols, which have a poly(oxypropylene) hydrophobic block, they have not found wide application for drug solubilisation, primarily because of their low solubilisation capacity. In attempts to achieve greater drug loading, recent work has concentrated on copolymers in which the core-forming blocks are designed to be more hydrophobic and more compatible with the drug to be encapsulated. Progress in this area has been reviewed and recent developments in the design of block copolymers of this type that combine high drug loading capacity with thermally reversible gelation characteristics in the temperature range suitable for potential application as in situ gelling vehicles following subcutaneous injection have also been discussed.


Assuntos
Portadores de Fármacos/química , Polietilenoglicóis/química , Polímeros/química , Química Farmacêutica , Coloides/química , Desenho de Fármacos , Géis/química , Humanos , Micelas , Solubilidade , Temperatura
15.
Int J Pharm ; 345(1-2): 35-41, 2007 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-17869036

RESUMO

Published values of the critical micelle concentration are tabulated for diblock copolymers E(m)P(n), E(m)B(n), E(m)S(n), E(m)L(n), E(m)VL(n) and E(m)CL(n), where E denotes a chain unit derived from ethylene oxide, P from propylene oxide, B from 1,2-butylene oxide, S from styrene oxide, L from dl-lactide, VL from gamma-valerolactone and CL from epsilon-caprolactone, and the subscripts denote average chain lengths. Noting that log(cmc/moldm(-3) is proportional to the standard Gibbs energy of micellisation, the dependence of this quantity on hydrophobic block length (n) is explored for a given E-block length. Superposition of data allows ranking of the hydrophobicities of the chain units. The ratios relative to the least hydrophobic unit are: P : L : B : VL : S : CL = 1 : 4 : 6 : 10 : 12 : 12 Transitions in the slope of log(cmc) versus n are assigned to changes in the unimer-micelle equilibrium and related to the formation of unimolecular micelles and, at high values of n, to the completion of that process. The formation transition is seen in the plots for all the copolymers except the least hydrophobic, E(m)P(n). The completion transition is seen in the plots for E(m)CL(n) and E(m)L(n) copolymers, as these alone include results for copolymers with very lengthy hydrophobic blocks.


Assuntos
Éteres/química , Poliésteres/química , Polímeros/química , Fenômenos Químicos , Química Farmacêutica , Físico-Química , Micelas , Solubilidade
16.
Langmuir ; 23(18): 9229-36, 2007 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-17676776

RESUMO

The micellization in dilute aqueous solution of Pluronic copolymers P123 (E21P67E21) and F127 (E98P67E98) and mixtures of the two was investigated using static and dynamic light scattering. Gelation of concentrated solutions of the two copolymers and their mixtures was studied using tube inversion and oscillatory rheometry. The two copolymers comicellized to give micelles with narrow size distributions. Clouding temperatures and critical micelle temperatures decreased as the proportion of P123 in the mixture was increased. Micelle association numbers of the mixed micelles lay between the values found for micelles of P123 and F127 alone, whereas micelle radii passed through maximum values in the range 0-50 wt % P123. As judged by the ratio of the thermodynamic to the hydrodynamic radius, the micelle interaction potential changes gradually from soft to hard as the proportion of P123 in the mixture is increased. Regions of cubic and hexagonal (birefringent) gel were defined for concentrated solutions. The high-temperature boundary of the 30 wt % cubic gel decreased monotonically from 90 to 43 degrees C as the proportion of P123 in the mixture was increased from 0 to 100 wt %, whereas the low-temperature boundary was essentially constant at 15 +/- 3 degrees C. Increasing the proportion of P123 in the mixture at 25 degrees C increased the concentration at which the cubic gel was first formed and decreased the concentration at which the hexagonal gel was first formed.

17.
Int J Pharm ; 328(1): 95-8, 2007 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-16942846

RESUMO

The gelation behaviour of concentrated micellar solutions of mixtures of a block copolymer of ethylene oxide and styrene oxide (E(137)S(18)E(137)) with one of ethylene oxide and propylene oxide (E(62)P(39)E(62)) has been investigated. Over a wide range of compositions, up to 90 wt.% E(137)S(18)E(137) in the mixture, gelation resembled that of solutions of E(62)P(39)E(62) alone, i.e. they gelled on heating from ambient to body temperature. In related experiments, using the aromatic drug griseofulvin as a comparative standard, it was demonstrated that solubilisation efficiency of dilute micellar solutions of the mixtures with 80 wt.% or more E(137)S(18)E(137) approached that of solutions of E(137)S(18)E(137) alone. Thus it was shown that the mixed system could have both the satisfactory solubilisation capacity of micellar solutions of E(137)S(18)E(137) and the desirable gelation characteristics of E(62)P(39)E(62), and so have potential for use in drug release applications involving in situ gelation.


Assuntos
Sistemas de Liberação de Medicamentos , Compostos de Epóxi/química , Óxido de Etileno/química , Antifúngicos/administração & dosagem , Química Farmacêutica , Géis , Griseofulvina/administração & dosagem , Micelas
18.
Langmuir ; 22(18): 7465-70, 2006 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-16922522

RESUMO

The aim of this study was to define a block copolymer micellar system with a high solubilization capacity for poorly soluble aromatic drugs. Ethylene oxide and phenyl glycidyl ether were sequentially polymerized to form the diblock copolymer G5E67 (G = phenyl glycidyl ether, OCH2CH(CH2OC6H5); E = oxyethylene, OCH2CH2; subscripts denote number-average block lengths in repeat units). The association properties in aqueous solution over the range 20-50 degrees C were investigated by surface tensiometry and light scattering, yielding values of the cmc, hydrodynamic radius, and association number; gel boundaries in concentrated micellar solution were investigated by tube inversion. The solubilization capacity of G5E67 for the poorly water-soluble drug griseofulvin was higher than that of a triblock EGE copolymer of longer G block length and considerably higher than that achieved with poloxamers (EmPnEm, P = oxypropylene).


Assuntos
Óxido de Etileno/química , Micelas , Preparações Farmacêuticas/química , Éteres Fenílicos/química , Polímeros/química , Géis/química , Interações Hidrofóbicas e Hidrofílicas , Estrutura Molecular , Solubilidade , Soluções , Viscosidade , Água/química
19.
Phys Chem Chem Phys ; 8(31): 3612-22, 2006 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-16883389

RESUMO

The article deals with the association behaviour in dilute aqueous solution of block copoly(oxyalkylene)s in which hydrophilic poly(ethylene oxide) is combined with hydrophobic poly(propylene oxide), poly(1,2-butylene oxide) or poly(styrene oxide). Polymers with three simple architectures are considered, i.e. copolymers of type EmAn, EmAnEm and AnEmAn, where E denotes an oxyethylene unit, A denotes a hydrophobic oxyalkylene unit, and the subscripts m and n denote number-average block lengths in repeat units. The aim is to examine how composition, block length and block architecture govern two fundamental properties, critical micelle concentration (cmc) and micelle association number (N), for systems which are in dynamic equilibrium. Copolymers with properties known to be greatly affected by heterogeneity in composition are excluded from consideration. A uniform pattern of behaviour emerges when log(cmc) is plotted against reduced hydrophobic block length (x), consistent with the micellisation equilibrium changing from one between unimers and multimolecular micelles at low values of x, to one between unimolecular micelles and multimolecular micelles at high values of x. Support for this model is provided by the enthalpy of micellisation, values of which fall effectively to zero as x is increased. Values of the micelle association number are used to define a critical hydrophobic block length for micellisation (n(cr)) for each class of diblock copolymers, values of which apply equally well to the half-length of the central block of corresponding EmAnEm triblock copolymers. Given these values, and irrespective of block architecture, the overall scaling law for the weight-average association number of the micelles is shown to be Nw = n'(1.07)m(-0.63) where m is the length (or half-length) of the hydrophilic block, and n' is the effective length of the hydrophobic block, equal to its length (or half-length) minus the critical length, i.e. n' = n-n(cr).


Assuntos
Algoritmos , Materiais Biocompatíveis/química , Polímeros/química , Água/química , Interações Hidrofóbicas e Hidrofílicas , Micelas , Polienos/química , Polietilenoglicóis/química , Polipropilenos/química , Poliestirenos/química , Solubilidade
20.
Langmuir ; 22(16): 6814-7, 2006 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-16863225

RESUMO

The viscoelasticity of aqueous micellar solutions of two oxyethylene/oxybutylene block copolymers (E(92)B(18) and B(20)E(510)) has been investigated using a torsional resonator operated at 26 kHz. For both systems considered, values of the dynamic viscosity (eta'(infinity)) point to partial draining of the micellar corona induced by the high-frequency oscillatory field. At low effective volume fractions, values of the elastic modulus (G'(infinity)) indicate that the repulsive interactions between micelles can be modeled by a power law function u(r) proportional to 1/r(nu) with exponents close to 13 and 6 for copolymers E(92)B(18) and B(20)E(510) respectively. At a critical copolymer concentration (c*) plots of log(G'(infinity)) against log(c) deviate from the straight lines established at low concentrations, implying that the systems undergo ergodic/nonergodic transitions.

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