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Drug Delivery System (DDS)

A drug delivery system (DDS) is an enhanced method of administering pharmaceutics to patients to achieve a therapeutic effect that could not be accomplished by administering the drug alone. Goto Laboratory has produced a novel drug delivery system that uses unique emulsion systems.

photo

Schematic illustration of the preparation
(from a water-in-oil emulsion)
of a solid particle in a S/O nanodispersion

Solid-in-Oil (S/O) nanodispersion
An emulsion is prepared by mixing two or more immiscible liquids such as water and oil with surfactants. In an emulsion, either water or oil is dispersed as a small particle in the other liquid. Goto Laboratory has developed a novel drug delivery system by using solid-in-oil nanodispersion, an oil-based nanodispersion of hydrophilic drugs. S/O nanodispersion, in which hydrophilic drugs are coated with hydrophobic surfactant molecules, is prepared by removing the water phase from a water-in-oil (W/O) emulsion, and offers much greater stability and smaller particle size than a W/O emulsion. We have dispersed various kinds of hydrophilic drugs (such as small molecules, proteins and DNA) in an oil phase as nano-order particles by using the S/O nanodispersion technique. The mean particle size of the prepared S/O nanodispersion was around 200-300 nm, as measured by dynamic light scattering. There were no precipitates after storing the S/O nanodispersion at room temperature for one month. To prepare a S/O nanodispersion, we can use sucrose erucate, which has already been approved as a drug adjuvant.

photo

Fluorescence microscopy
treated with the samples
containing FITC-labeled insulin

Transcutaneous drug delivery
Transcutaneous drug delivery, which refers to drug delivery through the skin, has many advantages over injections and oral administration. One advantage is that it can avoid the first-pass hepatic metabolism and provide patients with an easier and more convenient route for drug administration. Despite its great potential, the delivery of hydrophilic macromolecules such as peptides and proteins through the skin remains a challenging issue in the development of drug delivery systems. This is mainly due to the intrinsic barrier function of the skin, provided by the highly organized structure of the stratum corneum. To get past this barrier, a number of chemical penetration enhancers have been employed to increase the permeability of the drugs into the skin. However, it has been difficult to get therapeutic levels of relatively large drugs (over 500 Da) through intact skin and into systemic circulation by using a chemical penetration enhancer alone.

To overcome these problems, Goto Laboratory proposed a novel transcutaneous drug delivery system using a S/O nanodispersion technique. The idea is that the dispersion of proteins modified with a surfactant in the oil phase enables the proteins to permeate the skin without any physical enhancers or pre-treatments, if a suitable oil with the properties of a chemical penetration enhancer is selected. This concept is novel because, to date, almost all studies on transcutaneous delivery of hydrophilic drugs have been based on aqueous vehicles.

Department of Applied Chemistry
Professor Masahiro Goto
Professor Noriho Kamiya
Assistant Professor Fukiko Kubota
Assistant Professor Rie Wakabayashi
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