표적지향 약물전달을 위한 마그네타이트가 함유된

poly(ethyl-2-cyanoacrylate) nanoparticles의 제조

이홍재, 박성배, 함승주*, 김우식

연세대학교 화학공학과

haam@yonsei.ac.kr

Preparation of magnetite loaded poly(ethyl-2-cyanoacrylate) nanoparticles

for targeted drug delivery

Hongjae Yih, Seong-Bea Park, Seungjoo Haam, and Woo-Sik Kim

Department of Chemical Engineering, Yonsei University, Seoul 20-749, Korea

haam@yonsei.ac.kr

Introduction

Magnetic polymer particles are used in several biomedical applications, such as magnetic cell seperation, enzyme immunoassay, targeted drug delivery and diagnostics, etc.[1]

The purpose of the present work is the preparation of magnetite-contained biodegradable polymer nanoparticles for tageted drug delivery system which is one of the possible applications.

The magnetic material within particles could make it possible to direct the particles to the specified location by means of external magnetic fields. This, in turn, would reduce the side-effects of the drug because its levels in the general circulation are lowered. The polymer of particles would have the role of transporting the drug and releaseing it during its biodegradation.[2]

In this study, magnetite-contained poly(ethyl-2-cyanoacrylate) (MPECA) nanoparticles were prepared by emulsion polymerization method. At this point, magnetic material was used magnetite(Fe3O4) with quite low toxicity and well tolerance in the human body.[3] Also, biodegradable polymer was used poly(ethyl-2-cyanoacrylate) (PECA) with fast degradation rate, biodegradability, high biocompatibility, drug compatibility, and permeability. This is a member of the polyalkylcyanoacrylates(PACA) family, which is considered of high interest because of the strong reactivity of the corresponding monomers, able to polymerize easily in various media including water.[4]

Theory

Particles can be classified with two kinds by the form of small solids in paticles; spheres in which the small solids are dispersed throughout the particles,  capsules in which the small solids are confined to a central cavity surrounded by a membrane.     MPECA  nanoparticles of the sphere form can be prepared by emulsion polymerization. Although with slight variations, most authors have used the emulsion polymerization method for the synthesis of PECA nanoparticle, in which the mechanism of polymerization is an anionic process initiated by covalent bases present in the medium(e.g. OH- ions deriving from water dissociation): even weak base like OH- are capable of ionizing the monomer giving rise to carbanions which in turn react with other monomer units to form living chains. the polymerization terminates by addition of cations that neutralize such chains.[4] The technique involves the polymerization of the monomer in an aqueous solution(of a pharmaceutical drug in most instances).

The other form(capsules) can be obtained by interfacial polymerization with similar formulation. The interfacial polymerzation of water-in-oil nanoemulsion offers advantage over the use of size-reduced kinetically stabilised emulsions by virtue of the use of nanoemulsion. nanoemulsions are thermodynamically stable and form spontaneously so require minimal input of energy for their formation. They have a small and uniform droplet size, and they form reproducibly. All these properties render them amenable to industrial scale-up. Further, if biocompatible oils and surfactants are used for the formation of the nanoemulsion, the necessity of isolating the nanocapsules form the reaction matrix following polymerization is removed. nanocapsules can therefore be prepared in situ in a nanoemulsion matrix.[5]

Experiments

The MPECA  nanoparticles were prepared by emulsion polymerization method. In detail, the monomer(1%, w/v) was added dropwise, under mechanical stirring(1000rpm), to 50ml of an aqueous polymerization medium containing magnetite and surfactant(1%, w/v) at pH 2.5. After the polymerization was complete (usually 3h), the suspension of particles obtained was passed through filter. Free magnetite and surfactant were eliminated by repeated cycles of centrifugation at 12000rpm for 20min. The MPECA  nanoparticles were dried at 35℃ in a vacuum oven and stored in desicator.

The morphology, size and structural properties of particles were carried out by scanning electron microscopy(SEM), dynamic light scattering(DLS), and IR spectroscopy. Also, the total magnetite concentration of particle was determined UV analysis.

Results & Discussions

Fig. 1. shows that the morphology of MPECA particles at different magnetite/initial monomer ratio(w/v) which is from 1:3 to 3:1.  According to figure, most of particles are well formed except for magnetite/initial monomer ratio=3:1 condition(Fig. 1.(e)). The formed particles were spherical shape, smooth surface, and moderately homogenous size distribution.

Dynamic light scattering(DLS) was used to determine the size of prepared MPECA particles.(Fig. 2.) The size of formed particles is in the range of 300nm to 900nm.  In case of magnetite/initial monomer=1:3 , particle size is the smallest size which is 289.6nm. As magnetite proportion is incresed, particle size obtained increase.

Fig. 3. shows magnetite loading efficiency at different magnetite/initial monomer ratio. According as magnetite content is increase, magnetite loading effciency is increased. But generally magnetite loading effciency is lower than 10%.

Fig 4. shows the infrared spectra of the three types of particles which is magnetite, PECA, MPECA particles. IR spectra of iron oxides exhibit strong bands in the low-frequency region(1000-300cm-1) due to the iron oxide skeleton. Especially magnetite(Fe3O4) spectrum exhibits in 570cm-1. The main feature of this figure is the presence of the band of magnetite(570cm-1) in the spectrum of the MPECA particles.

MPECA particles prepared by emulsion polymerization method are monodisperse and size less than 1□. In the event of magnetite/initial monomer ratio=2:1, particle size is 880nm and magnetite loading efficiency of particle is the maximum. However, this process have a limit that magnetite loading efficiency is 8.6%.

Fig1.  Morphology of MPECA particles at different magnetite/initial monomer ratio by scanning electron microscopy(SEM). (a)1:3 (b)1:2 (c)1:1 (d)2:1 (e) 3:1

Fig2.  Size of MPECA particles at different magnetite/initial monomer ratio

by dynamic light scattering(DLS)

Fig 3. magnetite loading efficiency of magnetite-contained  poly(ethyl-2-cyanoacrylate)

at different magnetite/initial monomer ratio

Fig 4. structural properties of magnetite, PECA, MPECA particles by IR spectroscopy.

Reference

[1] Jhunu Chatterjee, Yousef Haik, J. Magn. Magn. Mater. 246, 382-391(2002).

[2] J.L. Arias, V. Gallardo, S.A. Gomez-Lopera, J. Cont. R, es. 77, 309-321(2001).

[3] R.H. Muller, S. Maaben, H. Weyhers, F. Specht, Int. J. Pharm. 138,   85-94(1996).

[4] A.J. Domb, J.Kost, D.M. Wiseman(Eds.), Handbook of biodegradable polymers,

Harwood, Amsterdam, 183-202(1997).

[5] Watnasirichaikul, S., Davies, N.M., Rades, T., Pharm. Res. 17, 684-689(2000).