Highly Uniform Superparamagnetic Mesoporous Spheres with Submicrometer Scale and Their Uptake into Cells

Abstract

A new template approach was developed to synthesize highly uniform superparamagnetic mesoporous spheres with submicrometer scale, composed of silica and CoFe 2 O 4 , in which mesoporous shell/solid core silica spheres with an average diameter of 505 nm are used as templates. Superparamagnetic phases are grown exclusively within mesoporous shells of the host silica spheres using a mixed solvent composed of ethanol and dioctyl ether, which results in maintaining the mesoporous nature of the host silica and retaining the superparamagnetic property. The samples annealed at temperatures above 773 K are converted into high-crystalline forms with enhanced coercivity and magnetization, which show a type IV isotherm typical for the mesoporous silica. The resulting superparamagnetic spheres are well-dispersible in water, have high magnetization values, and possess high surface areas. Cellular viability studies showed that the particles were readily endocytosed in human breast cancer (MCF-7) and mouse embryonic fibroblast (NIH-3T3) cells. Such highly uniform superparamagnetic spheres with submicrometer scale are suitable for renewable supports for catalytic applications and magnetic carriers for drug delivery.

Low-Temperature Preparation of Superparamagnetic CoFe2O4 Microspheres with High Saturation Magnetization

“…5a, 5b) display the two relatively high Ms values of 41.2 (taken from 220 nm) and 55.2 emu/g (330 nm), respectively. Both values are, however, somewhat lower than the bulk value (71.2 emu/g) [18,19]. The hysteresis loop shows essentially no coercivity ( H C ) for the smaller size samples (220 nm) and negligible value of 27 Oe (larger size specimens, a diameter of 330 nm), suggesting that improved coalescence of the crystallites in the nanostructures results in increased magnetic coupling and higher magnetization.…”

Magnetic Nanocomposites with Mesoporous Structures: Synthesis and Applications

“…An interesting way to finely control the particle size and shape of magnetic NPs is to impregnate the magnetic NPs inside an ordered mesoporous material. By using such an impregnation and reduction method, ordered mesoporous magnetic silica nanocomposites with various magnetic NPs including Co 3 O 4 , Fe 3 O 4 , CoFe 2 O 4 , and γ‐Fe 2 O 3 have been reported with high surface areas and different mesoporous structures and pore sizes ( Figure A) 81–90. Specifically, magnetic nanocomposites with mesoporous structures and large pore sizes such as magnetic NP@SBA‐15 (pore size 6.8 nm) can be achieved using this method.…”

Effects of Mesoporous Silica Coating and Postsynthetic Treatment on the Transverse Relaxivity of Iron Oxide Nanoparticles

“…23,24 Others have synthesized magnetic NPs inside the pores of MS NPs. 25 Alternative syntheses are based on a core-shell architecture, which is the focus of the present investigation. Many groups have developed syntheses of core-shell magnetic MS NPs (mMS NPs), 7,8,26,27 which display a range of conflicting r 2 values.…”