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Surface composition and contact angle relationships for differently prepared solid dispersions
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
2008 (English)In: European journal of pharmaceutics and biopharmaceutics, ISSN 0939-6411, E-ISSN 1873-3441, Vol. 70, 478-485 p.Article in journal (Refereed) Published
Abstract [en]

Solid dispersions are promising drug delivery forms which offer the possibility to disperse a hydrophobic drug in a hydrophilic matrix and thereby improve the dissolution behavior and the bioavailability of the drug. One important aspect and a prerequisite in understanding the drug dissolution mechanism from solid dispersions is a better analytical monitoring of the solid dispersion surface properties, such as powder surface composition and water adsorption properties. In this paper, we have considered chemical and structural surface analysis data for solid dispersions processed by spray drying or roto-evaporation and compared these data with information obtained by contact angle measurements. Firstly, we establish the usefulness and suitability of X-ray photoelectron spectroscopy (XPS) for determination of surface chemical composition and scanning electron microscopy (SEM) for determining the structure of solid dispersions composed of different types of carriers, drugs and drug concentrations. Secondly, we measure contact angles of solid dispersions to describe wettability, to finally establish a link between the surface chemical composition, the powder structure and the wetting behavior. These experimental methods offer a rapid screening tool for the selection of carrier, drug concentration and/or process in early development. In addition, they provide a useful tool for investigating structural aspects of solid dispersions which have intrinsic relevance for drug dissolution and stability.

Place, publisher, year, edition, pages
2008. Vol. 70, 478-485 p.
Keyword [en]
Solid dispersions, Roto-evaporation, Wettability, Spray drying, Contact angle, Surface composition, XPS, Powder morphology
Identifiers
URN: urn:nbn:se:kth:diva-11786DOI: 10.1016/j.ejpb.2008.05.026ISI: 000260697400008Scopus ID: 2-s2.0-52949135898OAI: oai:DiVA.org:kth-11786DiVA: diva2:281965
Note
QC 20100915Available from: 2009-12-18 Created: 2009-12-18 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Drugs and polymers in dissolving solid dispersions: NMR imaging and spectroscopy
Open this publication in new window or tab >>Drugs and polymers in dissolving solid dispersions: NMR imaging and spectroscopy
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The number of poorly water-soluble drug substances in the pharmaceutical pipeline is increasing, and thereby also the need to design effective drug delivery systems providing high bioavailability. One favourable formulation approach is preparation of solid dispersions, where dispersing a poorly water-soluble drug in a water-soluble polymer matrix improves the dissolution behaviour and the bioavailability of the drug. However, in order to take full advantage of such formulations the impact of material properties on their performance needs to be investigated.

 

An experimental toolbox has been designed, and applied, for analysing the processes which govern the behaviour of solid pharmaceutical formulations in general, and that of solid dispersions in particular. For the purpose of monitoring multifaceted phenomena in situ during tablet dissolution, nuclear magnetic resonance (NMR) spectroscopy and NMR imaging are superior to many other techniques, both on macroscopic and molecular levels. The versatility of NMR with its isotope and chemical selectivity allows one to follow the influence of the original tablet properties on polymer mobilisation, drug migration and water penetration selectively. Mapping these processes on relevant time scales in dissolving tablets highlighted the gel layer inhomogeneity below the originally dry tablet surface as a key factor for drug release kinetics.

 

Furthermore, NMR relaxometry has been shown to provide novel information about the particle size of the drug and its recrystallisation behaviour within swelling solid dispersions. The NMR experiments have been complemented and supported by investigation of the crystalline state, the powder morphology and the surface composition of the dry solid dispersions. These experiments have been performed by X-ray photoelectron spectroscopy (XPS),  scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dynamic contact angle (DAT) measurements.

 

The methods presented in this thesis provide a new avenue towards better understanding of the behaviour of solid dispersions, which in turn may result in more effective distribution of promising drug candidates despite their low water-solubility.

Abstract [sv]

En allt större andel av de läkemedelssubstanser som idag är av intresse för den farmaceutiska industrin är svårlösliga i vatten. För att trots detta erhålla hög biotillgänglighet måste man utveckla beredningsformer som medger effektiv frisättning av den aktiva substansen. En lovande sådan beredningsform utgörs av fasta dispersioner, där den svårlösliga substansen finfördelas i en vattenlöslig polymer. För att utnyttja dessa dispersioners potential fullt ut måste dock materialegenskapernas inverkan på deras beteende kartläggas i större utsträckning än vad som tidigare gjorts.

 

En uppsättning experimentella metoder har i detta arbete utvecklats och använts för att analysera de processer som styr beteendet hos fasta läkemedelsberedningar i allmänhet, och fasta dispersioner i synnerhet. För observation av sådana processer in situ, under pågående tablettupplösning, är NMR-spektroskopi (kärnmagnetisk resonans-spektroskopi) och NMR-avbildning överlägsna många andra tekniker, både på makroskopisk och på molekylär nivå. NMR är en mångsidig metod med både isotop- och kemisk selektivitet. Genom att utnyttja dessa möjligheter kan de enskilda sambanden mellan den ursprungliga tablettens materialegenskaper och polymermobilisering, vatteninträngning och den aktiva substansens migrering följas separat. Kartläggning av dessa processer, på relevanta tidsskalor i tabletter under upplösning, påvisar att gellagrets inhomogenitet inuti den ursprungliga tabletten har stor betydelse för frisättningskinetiken.

 

Vidare visar sig NMR-relaxometri ge värdefull information om den aktiva substansens partikelstorlek och dess omkristallisationsbeteende i fasta dispersioner under svällning och upplösning. NMR-experimenten kompletteras med oberoende karakterisering av det kristallina tillståndet, pulvermorfologin och ytsammansättningen hos de torra fasta dispersionerna. Dessa experiment utförs med hjälp av XPS (röntgen-fotoelektronspektroskopi), SEM (elektronmikroskopi), pXRD (pulver-röntgendiffraktion), DCS (differentiell kalorimetri), FTIR (infraröd Fourier transform spektroskopi) och DAT (dynamisk kontaktvinkel) mätningar.

 

De metoder som presenteras i den här avhandlingen pekar mot nya vägar att nå djupare förståelse för beteendet hos fasta dispersioner, vilket i sin tur kan leda till att fler lovande läkemedelssubstanser kan distribueras effektivt trots begränsad vattenlöslighet.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 76 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:1
National Category
Physical Chemistry Physical Chemistry Pharmaceutical Sciences
Identifiers
urn:nbn:se:kth:diva-11783 (URN)978-91-7415-510-5 (ISBN)
Public defence
2010-01-21, hörsal F3, Lindstedtsvägen 26, KTH, Stockholm, 09:30 (English)
Opponent
Supervisors
Note
QC 20100915Available from: 2009-12-18 Created: 2009-12-17 Last updated: 2010-09-15Bibliographically approved

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