Delivering Actives via Solid Lipid Nanoparticles and Nanostructured Lipid Carriers: Part I

Oct 1, 2010 | Contact Author | By: Johann W. Wiechers, PhD, JW Solutions, and Eliana B. Souto
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Title: Delivering Actives via Solid Lipid Nanoparticles and Nanostructured Lipid Carriers: Part I
SLNsx NLCsx deliveryx nanoparticlex lipid carrierx multilamellar vesiclesx stabilityx activex biocompatiblex
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Keywords: SLNs | NLCs | delivery | nanoparticle | lipid carrier | multilamellar vesicles | stability | active | biocompatible

Abstract: This first of a four-part series on SLNs and NLCs describes the differences between the two types and their delivery capabilities. The terms solid lipid nanoparticles and nanostructured lipid carriers are not very useful to distinguish these two delivery systems since both are solid, both are lipids, both are nanoparticles, and both are carrier systems. The only real difference between the two is the purity of the single lipid used in SLNs or multiple lipids used, i.e. one solid and one liquid, in NLCs. This factor has an enormous impact on the crystallinity of the lipid phase, which subsequently influences the loading capacity of the system for encapsulated active ingredients or API.

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JW Wiechers and EB Souto, Formulaitng focus—Delivering actives via solid lipid manoparticles and nanostructured lipid carriers: Part I, Cosm & Toil 125 (10) 22-30 (Oct 2010)

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This first of a four-part series on SLNs and NLCs (see Part IIPart III and Part IV) describes the differences between the two types and their delivery capabilities.

Solid lipid nanoparticles (SLNs) originally were introduced as an improvement over liposome delivery systems.1 This suggests that liposomes, reviewed previously in 2005,2 have some disadvantages. Advantages include the fact that they consist of biocompatible ingredients and are capable of including both water- and lipid-soluble actives; in addition, their membrane permeability and consequential release of actives can be regulated via the creation of single or multiple lamellar vesicles. However, disadvantages include their limited capability to enhance the stability of the incorporated active, as well as limited physical stability in real-life formulations.3

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This is an excerpt of an article from GCI Magazine. The full version can be found here.

 

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Figure 1. The differences between SLNs and NLCs

Schematic representation of SLNs (left) and NLCs (right); modified from Reference 4.

Schematic representation of SLNs (left) and NLCs (right); modified from Reference 4

Figure 2. A schematic overview of both the hot and cold homogenization

Figure 2. The production process of lipid nanoparticles using cold (left, light gray) and hot (right, dark gray) high pressure homogenization; reproduced with permission from Reference 4.

The production process of lipid nanoparticles using cold (left, light gray) and hot (right, dark gray) high pressure homogenization; reproduced with permission from Reference 4.

Figure 3. The lipid/active ratio will determine the SLN/NLC produced

Figure 3. Models of actives incorporated in lipid nanoparticles, homogeneous matrix; a) type I SLNs, b) type II SLNs, and c) type III SLNs; modified from Reference 4.

Models of actives incorporated in lipid nanoparticles, homogeneous matrix; a) type I SLNs, b) type II SLNs, and c) type III SLNs; modified from Reference 4.

Figure 4. The effect of adding chemically different lipids to a pure lipid

Figure 4. The effect of adding chemically different lipids to a pure lipid

The effect of adding chemically different lipids to a pure lipid; at left, the melting and crystallization temperatures of a pure lipid are shown—both quite high and with a relatively small difference (i.e., supercooling). By adding a chemically similar but nonidentical second lipid, the melting and crystallization temperatures drop but the second drops more than the first, leading to increased supercooling. Moving to the right, the greater the chemical difference, the greater the amount of supercooling; modified from Reference 8.

Figure 5. Selection criteria of lipid materials for SLNs and NLCs

Figure 5. Summary of selection criteria of lipid materials to be used in SLNs and NLCs

In Figure 5a, the influence of the crystallinity state of the lipids, which can be modulated via the choice of lipid, on the efficacy of SLNs and NLCs as skin delivery systems is shown. In Figure 5b, some practical experiments that assist in selecting the right lipids are indicated.

Footnotes

a Cutanova Cream Nano Repair Q10 and Intensive Serum NanoRepair Q10 are products of Dr. Rimpler GmbH, Germany.

b Witepsol W35 (INCI: Hydrogenated Coco-Glycerides) is a registered trademark of SASOL, Johannesburg.

c Dynasan 118 (INCI: Tristearin) is a registered trademark of SASOL, Johannesburg.

d Phospholipon 90G (INCI: Phosphatidyl Choline) is a registered trademark of Phospholipid GmbH, Cologne, Germany.

e Capra hircus homolipids were obtained from the laboratory of the Department of Pharmaceutics, University of Nigeria, Nsukka.

Biography: Johann W. Wiechers, PhD, JW Solutions

Johann W. Wiechers, PhD

A pharmacist by training, Johann W. Wiechers, PhD, earned his doctorate in 1989 in skin penetration enhancement at the University of Groningen, The Netherlands. Following six years at Unilever in the UK, he joined Uniqema in 1995 as skin R&D director. Wiechers founded JW Solutions, a consultancy focused on various aspects of cosmetic science, and released "Formulating for Efficacy, the Software", a computer program to help you deliver your active ingredients more effectively. Johann is no longer with us, but the work he started will continue just as he would have wished.

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