Kooperativer Bibliotheksverbund

Language: English

In: Journal of Controlled Release, 2002, Vol.81(1), pp.219-220

Keywords: Pharmacy, Therapeutics, & Pharmacology

ISSN: 0168-3659

E-ISSN: 1873-4995

DOI: 10.1016/S0168-3659(02)00039-1

Source: ScienceDirect Journals (Elsevier)

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Advanced Drug Delivery Reviews, Dec, 2012, Vol.64, p.290(12)

Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.addr.2012.09.029 Byline: S. Stolnik, L. Illum, S.S. Davis Keywords: Particulate (colloid) drug delivery system; Poloxamer; Poloxamine; Poly(ethylene oxide); PEG copolymer; Drug targeting; Biodegradable material; Protein adsorption; Biodistribution Abstract: To exert its activity a drug must reach its pharmacological site(s) of action(s) within the body. One of the current approaches to achieve site specific delivery utilises the use of a carrier. This review focuses on the physicochemical and biological properties of polymeric particulate carriers in the nanometre size range surface modified by poly(ethylene oxide) (PEO). Such systems are able to bypass the normal physiological defence processes occurring after the intravenous injection of particulates and, depending on the particle size and PEO layer properties, remain for a prolonged period of time in the systemic circulation, or have a degree of selectivity for sites of deposition within the body. Article History: Accepted 13 April 1995 Article Note: (footnote) [star] PII of original article: 0169-409X(95)00025-9. The article was originally published in Advanced Drug Delivery Reviews 16 (1995) 195-214.

Keywords: Copolymers ; Drug Delivery Systems ; Adsorption ; Ethylene Oxide ; Air Pollution

ISSN: 0169-409X

Source: Cengage Learning, Inc.

Language: English

In: Gastroenterology, 2011, Vol.140(5), pp.S-1002-S-1002

Keywords: Medicine

ISSN: 0016-5085

E-ISSN: 1528-0012

DOI: 10.1016/S0016-5085(11)64162-0

Source: ScienceDirect Journals (Elsevier)

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Planetary and Space Science, 2011, Vol.59(14), pp.1804-1814

Description: It is suspected that the lunar exosphere has a dusty component dispersed above the surface by various physical mechanisms. Most of the evidence for this phenomenon comes from observations of “lunar horizon glow” (LHG), which is thought to be produced by the scattering of sunlight by this exospheric dust. The characterization of exospheric dust populations at the Moon is key to furthering our understanding of fundamental surface processes, as well as a necessary requirement for the planning of future robotic and human exploration. We present a model to simulate the scattering of sunlight by complex lunar dust grains (i.e. grains that are non-spherical and can be inhomogeneous in composition) to be used in the interpretation of remote sensing data from current and future lunar missions. We numerically model lunar dust grains with several different morphologies and compositions and compute their individual scattering signatures using the Discrete Dipole Approximation (DDA). These scattering properties are then used in a radiative transfer code to simulate the light scattering due to a dust size distribution, as would likely be observed in the lunar exosphere at high altitudes 10's of km. We demonstrate the usefulness and relevance of our model by examining mode: irregular grains, aggregate of spherical monomers and spherical grains with nano-phase iron inclusions. We subsequently simulate the scattering by two grain size distributions ( and radius), and show the results normalized per-grain. A similar methodology can also be applied to the analysis of the LHG observations, which are believed to be produced by scattering from larger dust grains within about a meter of the surface. As expected, significant differences in scattering properties are shown between the analyses employing the widely used Mie theory and our more realistic grain geometries. These differences include large variations in intensity as well as a positive polarization of scattered sunlight caused by non-spherical grains. Positive polarization occurs even when the grain size is small compared to the wavelength of incident sunlight, thus confirming that the interpretation of LHG based on Mie theory could lead to large errors in estimating the distribution and abundances of exospheric dust. ► Complex lunar dust grain modeled and their scattering properties computed. ► The scattering by a lunar exosphere composed of such is simulated. ► Comparison is made with the standard model for spherical grains. ► Significant variations in scattering are observed between the two models. ► Interpretation of observations based on spherical grains would lead to large errors.

Keywords: Moon ; Dust ; Radiative Transfer ; Scattering ; Polarization ; Engineering ; Astronomy & Astrophysics ; Physics

ISSN: 0032-0633

E-ISSN: 1873-5088

DOI: 10.1016/j.pss.2011.01.003

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Advanced Drug Delivery Reviews, December 2012, Vol.64, pp.290-301

Description: To exert its activity a drug must reach its pharmacological site(s) of action(s) within the body. One of the current approaches to achieve site specific delivery utilises the use of a carrier. This review focuses on the physicochemical and biological properties of polymeric particulate carriers in the nanometre size range surface modified by poly(ethylene oxide) (PEO). Such systems are able to bypass the normal physiological defence processes occurring after the intravenous injection of particulates and, depending on the particle size and PEO layer properties, remain for a prolonged period of time in the systemic circulation, or have a degree of selectivity for sites of deposition within the body.

Keywords: Particulate (Colloid) Drug Delivery System ; Poloxamer ; Poloxamine ; Poly(Ethylene Oxide) ; Peg Copolymer ; Drug Targeting ; Biodegradable Material ; Protein Adsorption ; Biodistribution ; Biology ; Pharmacy, Therapeutics, & Pharmacology

ISSN: 0169-409X

E-ISSN: 1872-8294

DOI: 10.1016/j.addr.2012.09.029

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: International Journal of Pharmaceutics, 2007, Vol.338(1), pp.94-103

Description: The effect of bioadhesive formulations on the direct transport of an angiotensin antagonist drug ( C-GR138950) from the nasal cavity to the central nervous system was evaluated in a rat model. Three different bioadhesive polymer formulations (3% pectin LM-5, 1.0% pectin LM-12 and 0.5% chitosan G210) containing the drug were administered nasally to rats by inserting a dosing cannula 7 mm into the nasal cavity after which the plasma and brain tissue levels were measured. It was found that the polymer formulations provided significantly higher plasma levels and significantly lower brain tissue levels of drug than a control, in the form of a simple drug solution. Changing the depth of insertion of the cannula from 7 to 15 mm, in order to reach the olfactory region in the nasal cavity significantly decreased plasma levels and significantly increased brain tissue levels of drug for the two formulations studied (1.0% pectin LM-12 and a simple drug solution). There was no significant difference between the drug availability for the bioadhesive formulation and the control in the brain when the longer cannula was used for administration. It is suggested that the conventional rat model is not suitable for evaluation of the effects of bioadhesive formulations in nose-to-brain delivery.

Keywords: Bioadhesive Formulations ; Olfactory Region ; Pectin ; Chitosan ; Nasal Administration ; Pharmacy, Therapeutics, & Pharmacology

ISSN: 0378-5173

E-ISSN: 1873-3476

DOI: 10.1016/j.ijpharm.2007.01.047

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Journal of Controlled Release, 2007, Vol.118(2), pp.225-234

Description: There is an increasing need for nasal drug delivery systems that could improve the efficiency of the direct nose to brain pathway especially for drugs for treatment of central nervous system disorders. Novel approaches that are able to combine active targeting of a formulation to the olfactory region with controlled release bioadhesive characteristics, for maintaining the drug on the absorption site are suggested. If necessary an absorption enhancer could be incorporated. Low methylated pectins have been shown to gel and be retained in the nasal cavity after deposition. Chitosan is known to be bioadhesive and also to work as an absorption enhancer. Consequently, two types of pectins, LM-5 and LM-12, together with chitosan G210, were selected for characterisation in terms of molecular weight, gelling ability and viscosity. Furthermore, studies on the release of model drugs from candidate formulations and the transport of drugs across MDCK1 cell monolayers in the presence of pectin and chitosan were also performed. Bioadhesive formulations providing controlled release with increased or decreased epithelial transport were developed. Due to their promising characteristics 3% LM-5, 1% LM-12 pectin and 1% chitosan G210 formulations were selected for further biological evaluation in animal models.

Keywords: Chitosan ; Pectin ; Nose to Brain Delivery ; Drug Release ; Drug Transport ; Pharmacy, Therapeutics, & Pharmacology

ISSN: 0168-3659

E-ISSN: 1873-4995

DOI: 10.1016/j.jconrel.2006.12.014

URL: View record in ScienceDirect (Access to full text may be restricted)

Language: English

In: Journal of Controlled Release, 1985, Vol.2, pp.27-38

Description: The design and evaluation of delivery systems for the gastrointestinal tract requires knowledge about three inter-related topics, the drug, the delivery system and the destination intended. Preformulation data describing the physicochemical characteristics of a drug molecule need to be considered in relation to known physiological variables such as gastrointestinal pH gradients and transit times. The drug progabide, which is unstable under acid conditions, is used to illustrate the delicate balance between physical and physiological variables and the use of physical models describing the biopharmaceutics and pharmacokinetic events for the design of an appropriate delivery system. Similarly, the use of in vitro dissolution tests and diffusion experiments can provide essential information on the mechanisms of drug release but are not necessarily good predictors of the in vivo situation. The non-invasive technique of gamma scintigraphy has been used to follow in vivo release rates and to relate these to pharmacokinetic parameters. The same scintigraphic method has been used to follow the gastrointestinal transit of a variety of controlled release systems to include pellets, matrix systems and osmotic pumps. The effect of dosage characteristics and physiological variables, particularly diet, can be evaluated. Large (〉5 mm) units will be retained in a fed stomach while smaller units can empty in a similar way to liquids. Small intestine transit time is short (3 h ± 1 h ) for all systems studied. This result has implications for the design of controlled release delivery systems for drugs with poor absorption in the large intestine, as well as for the development of positioned release systems (colon targeting).

Keywords: Pharmacy, Therapeutics, & Pharmacology

ISSN: 0168-3659

E-ISSN: 1873-4995

DOI: 10.1016/0168-3659(85)90030-6

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Language: English

In: Gastrointestinal Endoscopy, April 2011, Vol.73(4), pp.AB130-AB130

Keywords: Medicine

ISSN: 0016-5107

E-ISSN: 1097-6779

DOI: 10.1016/j.gie.2011.03.061

Source: ScienceDirect Journals (Elsevier)

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Language: English

In: Journal of Controlled Release, 2001, Vol.70(3), pp.353-363

Description: Poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles of 150-nm mean size were produced by an interfacial deposition method. The polar model drug Rose Bengal was successfully loaded into the nanoparticles during production and the surface of these particles was subsequently modified with poloxamer 407 and poloxamine 908 in order to create a steric stabilising layer of PEG on the surface. Drug loading was low (〈1%) which can be attributed to the polar nature of the drug and the small size of the nanoparticles. Drug release was biphasic with 50% release measured within 30 min in serum. After intravenous injection in rats, the drug loaded nanoparticles substantially avoided capture by the Kupffer cells of the liver as compared to free drug. The half-life of Rose Bengal in the blood stream when administered in the nanoparticles was greatly extended with approximately 30% remaining after 1 h as compared to only 8% of Rose Bengal left 5 min after administration in solution. These surface modified nanoparticles would have potential as carriers for drugs to specific sites within the body or for slow release of drug within the circulation.

Keywords: Poly( D, L-Lactide-Co-Glycolide) (Plga) Nanoparticles ; Poloxamer 407 ; Poloxamine 908 ; Drug Targeting ; Rose Bengal ; Pharmacy, Therapeutics, & Pharmacology

ISSN: 0168-3659

E-ISSN: 1873-4995

DOI: 10.1016/S0168-3659(00)00367-9

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