Special Issue "Colloidal Drug Carrier Systems"

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A special issue of Pharmaceutics (ISSN 1999-4923).

Deadline for manuscript submissions: closed (30 April 2011)

Special Issue Editor

Guest Editor
Prof. Dr. Dr. h.c. Reinhard Neubert (Website)

Biopharmacy Group, Pharmaceutics and Biopharmaceutics Division, Institute of Pharmacy, Martin-Luther-University Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, D-06120 Halle/Saale, Germany
Phone: +49-345-5525000
Fax: +49 345 55 27 292
Interests: drug transport; dermal drug delivery; colloidal drug carrier systems; biosensors based on quartz microbalance; drug analysis based on capillary electrophoresis and HPLC-mass spectrometry; food-drug interactions; molecular structure of the stratum corneum lipids

Special Issue Information

Dear Colleagues,

Modern colloidal drug carriers (CDCs) are called in the literature mostly microemulsions (MEs). These systems form spontaneously combining appropriate amounts of a lipophilic and a hydrophilic ingredient, as well as a surfactant and a co-surfactant.

The formation of a ME is accompanied by a significant increase in the interfacial area A. The required very low interfacial tension cannot be realized by only one surfactant. The additionally used cosurfactant penetrates the amphiphilic interfacial layer and increases its curvature and fluidity.1,2

Basically two types of MEs are differentiated: bicontinuous ones and MEs with droplet like structure. The droplet structures are forming depending on the major compounds water-in-oil (w/o) and oil-in-water (o/w) MEs having colloidal phases in the range of 10 – 100 nm.

The term “ME” itself is sometimes used in a misleading way. On the one hand, various homogeneous surfactant-containing solutions were named like this and on the other hand, the expression itself implies emulsion-like properties with droplet sizes in the submicron-range. In the future, therefore, the term colloidal drug carrier (CDC) should be used. This concept  covers also other colloidal structures such as solubilized micellar systems are also covered by the term CDC. Some authors use the term “swollen micelles” to describe droplet like MEs.

Due to their special features, CDCs such as MEs offer a lot of advantages for pharmaceutical use, such as ease of preparation, long term stability, high solubilization capacity for hydrophilic and lipophilic drugs, and improved drug delivery. The latter provides a wide range of possible applications.

Most interesting is the application of CDCs:

i) to improve the bioavailability of extremely lipophilic low molecular drugs and modern biopharmaceuticals such as peptides, proteins as well as RNA and DNA derivatives and
ii) to develop new ways of drug delivery such as transdermal, parenteral and ocular drug delivery.

Prof. Dr. Reinhard Neubert
Guest Editor

References:

1    De Gennes, P.G.; Taupin, C. Microemulsions and the flexibility of oil/water interfaces. J. Phys. Chem. 1982, 86, 2294-2304.
2    Attwood, D. Microemulsions. In Colloidal drug delivery systems, Drugs and the Pharmaceutical Sciences; Kreuter, J., ed.; Marcel Dekker: New York, NY, USA, 1994; Volume 66.

Keywords

  • colloidal carrier systems
  • microemulsions
  • drug delivery
  • characterization
  • microstructure
  • compatibility
  • surfactants
  • cosurfactants
  • cosolvents
  • solubilisation
  • absorption
  • penetration
  • permeation
  • bioavailability
  • low molecular drugs
  • biopharmaceuticals (peptides, proteins, DNA and RNA derivatives)

Published Papers (5 papers)

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Research

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Open AccessArticle Rapid Detection and Identification of Overdose Drugs in Saliva by Surface-Enhanced Raman Scattering Using Fused Gold Colloids
Pharmaceutics 2011, 3(3), 425-439; doi:10.3390/pharmaceutics3030425
Received: 5 May 2011 / Revised: 1 July 2011 / Accepted: 11 July 2011 / Published: 13 July 2011
Cited by 14 | PDF Full-text (629 KB) | HTML Full-text | XML Full-text
Abstract
The number of drug-related emergency room visits in the United States doubled from 2004 to 2009 to 4.6 million. Consequently there is a critical need to rapidly identify the offending drug(s), so that the appropriate medical care can be administered. In an [...] Read more.
The number of drug-related emergency room visits in the United States doubled from 2004 to 2009 to 4.6 million. Consequently there is a critical need to rapidly identify the offending drug(s), so that the appropriate medical care can be administered. In an effort to meet this need we have been investigating the ability of surface-enhanced Raman spectroscopy (SERS) to detect and identify numerous drugs in saliva at ng/mL concentrations within 10 minutes. Identification is provided by matching measured spectra to a SERS library comprised of over 150 different drugs, each of which possess a unique spectrum. Trace detection is provided by fused gold colloids trapped within a porous glass matrix that generate SERS. Speed is provided by a syringe-driven sample system that uses a solid-phase extraction capillary combined with a SERS-active capillary in series. Spectral collection is provided by a portable Raman analyzer. Here we describe successful measurement of representative illicit, prescribed, and over-the-counter drugs by SERS, and 50 ng/mL cocaine in saliva as part of a focused study. Full article
(This article belongs to the Special Issue Colloidal Drug Carrier Systems)
Open AccessArticle Fliposomes: pH-Sensitive Liposomes Containing a trans-2-morpholinocyclohexanol-Based Lipid That Performs a Conformational Flip and Triggers an Instant Cargo Release in Acidic Medium
Pharmaceutics 2011, 3(3), 379-405; doi:10.3390/pharmaceutics3030379
Received: 4 May 2011 / Revised: 7 June 2011 / Accepted: 30 June 2011 / Published: 11 July 2011
Cited by 15 | PDF Full-text (1489 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Incorporation of a pH-sensitive conformational switch into a lipid structure enables a drastic conformational flip upon protonation that disrupts the liposome membrane and causes rapid release of cargo specifically in areas of increased acidity. pH-sensitive liposomes containing the amphiphile (1) [...] Read more.
Incorporation of a pH-sensitive conformational switch into a lipid structure enables a drastic conformational flip upon protonation that disrupts the liposome membrane and causes rapid release of cargo specifically in areas of increased acidity. pH-sensitive liposomes containing the amphiphile (1) with trans-2-morpholinocyclohexanol conformational switch, a phospholipid, and a PEG-lipid conjugate were constructed and characterized. The optimized composition—1/POPC/PEG-ceramide (50/45/5)could be stored at 4 °C and pH 7.4 for up to 1.5 years, and was stable in blood serum in vitro after 48 h at 37 °C. Liposomes loaded with ANTS/DPX or methotrexate demonstrated an unusually quick content release (in a few seconds) at pH below 5.5, which was independent of inter-liposome contact. The pH-titration curve for the liposome leakage paralleled the curve for the acid-induced conformational flip of 1 studied by 1H-NMR. Freeze-fracture electron microscopy images showed budding and division of the bilayer at pH 5.5. A plausible mechanism of pH-sensitivity involves an acid-triggered conformational flip of 1, shortening of lipid tails, and membrane perturbations, which cause the content leakage. The methotrexate-loaded liposomes demonstrated much higher cytotoxicity in HeLa cells than the free drug indicating that they can serve as viable drug delivery systems. Full article
(This article belongs to the Special Issue Colloidal Drug Carrier Systems)
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Open AccessArticle Influence of the Vehicle on the Penetration of Particles into Hair Follicles
Pharmaceutics 2011, 3(2), 307-314; doi:10.3390/pharmaceutics3020307
Received: 14 April 2011 / Revised: 30 May 2011 / Accepted: 8 June 2011 / Published: 14 June 2011
Cited by 7 | PDF Full-text (418 KB) | HTML Full-text | XML Full-text
Abstract
Recently, it has been demonstrated that particulate substances penetrate preferentially into the hair follicles and that the penetration depth depends on the particle size. In the present study, the influence of the vehicle of the particulate substances on the penetration depth was [...] Read more.
Recently, it has been demonstrated that particulate substances penetrate preferentially into the hair follicles and that the penetration depth depends on the particle size. In the present study, the influence of the vehicle of the particulate substances on the penetration depth was investigated. Four different formulations (ethanolic suspension, aqueous suspension, ethanolic gel and aqueous gel) containing peptide-loaded particles of 1 µm in diameter were prepared and applied on porcine ear skin. After penetration, punch biopsies were taken and the penetration depths of the particles were investigated by laser scanning microscopy. The deepest penetration was achieved with the gel formulations demonstrating an influence of the vehicle on the penetration depth of particulate substances. Full article
(This article belongs to the Special Issue Colloidal Drug Carrier Systems)
Open AccessArticle Semi-solid Sucrose Stearate-Based Emulsions as Dermal Drug Delivery Systems
Pharmaceutics 2011, 3(2), 275-306; doi:10.3390/pharmaceutics3020275
Received: 7 April 2011 / Revised: 20 May 2011 / Accepted: 30 May 2011 / Published: 30 May 2011
Cited by 17 | PDF Full-text (2207 KB) | HTML Full-text | XML Full-text
Abstract
Mild non-ionic sucrose ester surfactants can be employed to produce lipid-based drug delivery systems for dermal application. Moreover, sucrose esters of intermediate lipophilicity such as sucrose stearate S-970 possess a peculiar rheological behavior which can be employed to create highly viscous semi-solid [...] Read more.
Mild non-ionic sucrose ester surfactants can be employed to produce lipid-based drug delivery systems for dermal application. Moreover, sucrose esters of intermediate lipophilicity such as sucrose stearate S-970 possess a peculiar rheological behavior which can be employed to create highly viscous semi-solid formulations without any further additives. Interestingly, it was possible to develop both viscous macroemulsions and fluid nanoemulsions with the same chemical composition merely by slight alteration of the production process. Optical light microscopy and cryo transmission electron microscopy (TEM) revealed that the sucrose ester led to the formation of an astonishing hydrophilic network at a concentration of only 5% w/w in the macroemulsion system. A small number of more finely structured aggregates composed of surplus surfactant were likewise detected in the nanoemulsions. These discoveries offer interesting possibilities to adapt the low viscosity of fluid O/W nanoemulsions for a more convenient application. Moreover, a simple and rapid production method for skin-friendly creamy O/W emulsions with excellent visual long-term stability is presented. It could be shown by franz-cell diffusion studies and in vitro tape stripping that the microviscosity within the semi-solid formulations was apparently not influenced by their increased macroviscosity: the release of three model drugs was not impaired by the complex network-like internal structure of the macroemulsions. These results indicate that the developed semi-solid emulsions with advantageous application properties are highly suitable for the unhindered delivery of lipophilic drugs despite their comparatively large particle size and high viscosity. Full article
(This article belongs to the Special Issue Colloidal Drug Carrier Systems)
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Review

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Open AccessReview Structural Versatility of Bicellar Systems and Their Possibilities as Colloidal Carriers
Pharmaceutics 2011, 3(3), 636-664; doi:10.3390/pharmaceutics3030636
Received: 3 June 2011 / Revised: 21 July 2011 / Accepted: 5 September 2011 / Published: 14 September 2011
Cited by 6 | PDF Full-text (5127 KB) | HTML Full-text | XML Full-text
Abstract
Bicellar systems are lipid nanostructures formed by long- and short-chained phospholipids dispersed in aqueous solution. The morphological transitions of bicellar aggregates due to temperature, composition and time variations have been revised in this work. To this end, two bicellar systems have been [...] Read more.
Bicellar systems are lipid nanostructures formed by long- and short-chained phospholipids dispersed in aqueous solution. The morphological transitions of bicellar aggregates due to temperature, composition and time variations have been revised in this work. To this end, two bicellar systems have been considered; one formed by dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl- phosphatidylcholine (DHPC) and another formed by dipalmitoyl-phosphatidylcholine (DPPC) and DHPC. The relationship between the magnetic alignment, the morphology of the aggregates and the phase transition temperature (Tm) of lipids is discussed. In general terms, the non-alignable samples present rounded objects at temperature below the Tm. Above this temperature, an increase of viscosity is followed by the formation of large elongated aggregates. Alignable samples presented discoidal objects below the Tm. The best alignment was achieved above this temperature with large areas of lamellar stacked bilayers and some multilamellar vesicles. The effect of the inclusion of ceramides with different chain lengths in the structure of bicelles is also revised in the present article. A number of physical techniques show that the bicellar structures are affected by both the concentration and the type of ceramide. Systems are able to incorporate 10% mol of ceramides that probably are organized forming domains. The addition of 20% mol of ceramides promotes destabilization of bicelles, promoting the formation of mixed systems that include large structures. Bicellar systems have demonstrated to be morphologically stable with time, able to encapsulate different actives and to induce specific effects on the skin. These facts make bicellar systems good candidates as colloidal carriers for dermal delivery. However, water dilution induces structural changes and formation of vesicular structures in the systems; stabilization strategies have been been explored in recent works and are also updated here. Full article
(This article belongs to the Special Issue Colloidal Drug Carrier Systems)
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