Oral and transdermal drug delivery systems: role of lipid-based lyotropic liquid crystals

Abstract

Liquid crystal (LC) dosage forms, particularly those using lipid-based lyotropic LCs (LLCs), have generated considerable interest as potential drug delivery systems. LCs have the physical properties of liquids but retain some of the structural characteristics of crystalline solids. They are compatible with hydrophobic and hydrophilic compounds of many different classes and can protect even biologicals and nucleic acids from degradation. This review, focused on research conducted over the past 5 years, discusses the structural evaluation of LCs and their effects in drug formulations. The structural classification of LLCs into lamellar, hexagonal and micellar cubic phases is described. The structures of these phases are influenced by the addition of surfactants, which include a variety of nontoxic, biodegradable lipids; these also enhance drug solubility. LLC structure influences drug localization, particle size and viscosity, which, in turn, determine drug delivery properties. Through several specific examples, we describe the applications of LLCs in oral and topical drug formulations, the latter including transdermal and ocular delivery. In oral LLC formulations, micelle compositions and the resulting LLC structures can determine drug solubilization and stability as well as intestinal transport and absorption. Similarly, in topical LLC formulations, composition can influence whether the drug is retained in the skin or delivered transdermally. Owing to their enhancement of drug stability and promotion of controlled drug delivery, LLCs are becoming increasingly popular in pharmaceutical formulations.

Morphological Control Over Three‐ and Four‐Phase Superstructures in Blends of Asymmetric ABC and BAC Triblock Terpolymers

“…The microphase separation of pure SIM 171 shows at the top part of the TEM image (Figure a) laying cylinders in light gray (PS) surrounded by dark gray helical structures (PI) in a white matrix (PMMA). At the bottom of this image standing cylinders show a hexagonal arrangement, which is verified by scattering reflections at relative q values of 1, , , , and in the SAXS measurement ( Figure ). The TEM image of neat ISM 318 (Figure b) does not show a well‐ordered structure so that it is quite difficult to distinguish the exact morphology from this image.…”

Rapid Stabilization of Immiscible Fluids using Nanostructured Interfaces via Surfactant Association

“…Amphiphilic systems using oil, water, and surfactants have been utilized in a variety of applications ranging from oil recovery and drug delivery, to food and personal care products [1][2][3][4]. The main objective of amphiphilic surfactant systems is to increase emulsion stability and control colloidal structures at the nanoscale [5,6].…”

Improved skin penetration using active and passive enhancement methods

“…In the case of LLC, the drug is mostly localized in the dermal layers of the skin, presenting high intensity values. These results confirm the good penetration enhancer skills of LLC, due to their skin-similar structure and relatively high surfactant content, which is able to interrupt the skin barrier [40,106]. LLC contains a relatively high amount of Kolliphor RH40, which is a penetration enhancer surfactant that has a disordering effect on SC lamellar structure and disturbs the ordered lipid structure [27,[107][108][109][110].…”