We demonstrate a strategy for the synthesis of multifunctional mesoporous silica nanoparticles. These uniform tumblerlike nanocomposites, which simultaneously possess magnetic, luminescent, and porous properties, have great potential in biomedical applications.

Cells have many advantages as therapeutic agents. They are able to carry out complex functions, as in stem cell [1] or immune cell therapy. [2] For effective therapy, the delivered cells must carry long-lived tracking agents for monitoring the position and fate of the injected cells. At present, monitoring is often carried out by slow histological analysis, which requires tissue biopsy. Recently, the development of noninvasive real-time tracking of injected cells has attracted a lot of attention for its clinical potential. Fluorescent nanomaterials have been successfully utilized as labels in biological and medical applications for imaging [3,4] and diagnostic purposes. [5][6][7] The limited capability of the fluorescence technique in detecting deep tissues restricts the collection of information in vivo. Magnetic resonance imaging (MRI), one of the most important noninvasive imaging techniques, has been widely used for clinical diagnosis [8] and biomedical research. However, its sensitivity is relatively low for cellularlevel applications. [9] Hence, the synthesis of a new MRI con-trast agent [10][11][12][13] with high sensitivity would be of great interest.Recently, the development of a nanomaterial-based probe with multifunctionalities has become a very active field. Preferably, the functionalities should combine the advantages of MRI in noninvasiveness, fluorescence in high sensitivity and resolution, a surface functional group for targeting, and the ability to deliver drugs locally. Among these, the carrying of good and long-lived MRI contrast agents would be the most useful. Our interest is in developing a nanoparticle form of mesoporous silica, which has some unique properties, such as rigid structure, large pore volume, uniform pore size, great surface-modification capability, [14] and good biocompatibility. It has also been demonstrated as a biomarker [15,16] and a drug carrier. [17][18][19] Previously, we reported multimodal tumblerlike mesoporous silica, which carries a magnetic iron oxide nanoparticle as a T 2 contrast agent (T 1 and T 2 = magnetic relaxation times) and a fluorescent dye. [20] However, the T 2 agent often gives poor contrast in dark areas, such as the liver. Herein, we report a new multifunctional mesoporous silica nanorod that possesses green fluorescence and paramagnetism, and could serve as a good contrast agent in T 1 and T 2 imaging.The multimodality of nanoparticle-based monitoring agents has been developed before. However, very few have been demonstrated as a platform in cell monitoring. [21] There are several different combinations of luminescent materials, MRI contrast agents, and support. The iron oxide nanoparticle, a typical T 2 contrast agent, has been demonstrated to be a multimodal probe by surface functionalization with Cy5.5 dye and chlorotoxin to detect gliomas. [22] Santra and co-workers also developed novel multifunctional probes by encapsulating Gd-TSPETE (n-trimethoxysilylpropyl)ethyldiamine triacetic acid trisodium salt) and CdSe:Mn/ZnS core-shell quantum dots o...

The unique properties of mesoporous silica nanoparticles (MSNs), such as high surface areas, uniform pore size, easy modification, and biocompatibility, make them highly suitable for biological applications. [1][2] In previous reports, MSNs have been demonstrated to function as cell markers [3][4][5][6] and as gene transfection [7][8] and drug delivery agents. [9][10] Although these cell-level studies are attractive, some important issues, such as the cellular uptake efficiency, toxicity, and circulation behavior of MSNs in living animals, still have to be addressed for further practical animal-level applications.Superparamagnetic nanoparticles (i.e., magnetite) with diameters of less than 20 nm exhibit effective magnetic resonance imaging (MRI) contrast enhancement behavior. Because MRI is a noninvasive imaging method, it is a powerful tool with which to track the migration of cells and to investigate the distribution of nanoparticles in the living body. The main drawbacks of the MRI technique, however, are low sensitivity and resolution, which make it unable to provide detailed biological information.In previous reports, magnetic-optical bifunctional nanoparticles have been fabricated for imaging applications. However, they are nonporous hybrid magnetic composites. [11][12] To offset the shortcomings and to expand the bioimaging/delivery A C H T U N G T R E N N U N G applications, simultaneous attachment of a fluorescent probe (subcellular imaging) and a MRI probe (noninvasive imaging) to MSN is an important task. Recently, we adopted a strategy involving the simultaneous fusion of amorphous silica shells of Fe 3 O 4 @SiO 2 nanoparticles with MSNs that are attached to fluorescein isothiocyanate (FITC).[13] These nanoparticles with multifunctionalities-fluorescent, magnetic, and porous (MagDye@MSNs)-can simultaneously serve as bimodal imaging probes and drug reservoirs. Thus, we believe that MagDye@MSNs would be a suitable material with which to study the cellular uptake efficiency, toxicity, and accumulative behavior of MSNs in living animals. To the best of our knowledge, this is the first report of direct injection of mesoporous silica nanoparticles (MSNs) into mice and of in vivo visualization of the localization of MSNs by MRI.Mag-Dye@MSNs were synthesized according to the method we previously developed [13] (the detailed synthetic method is described in the Experimental Section). A transmission electron microscopy (TEM) image of the Mag-Dye@MSNs (Figure 1) shows that mostly one Fe 3 O 4 @SiO 2 nanoparticle was attached to one MSN. The inset figure further confirms that MagDye@MSNs have a well ordered 2D hexagonal structure, which is consistent with the X-ray diffraction (XRD) spectrum. With regard to the physical properties of Mag-Dye@MSNs, their A C H T U N G T R E N N U N G surface area, pore volume, and pore size are 839 m 2 g À1 , 0.67 cm 3 g À1 , and 2.5 nm, respectively. Water-suspended MagDye@MSNs exhibit the typical fluorescein emission (l em = 515 nm). The T 2 relaxivity (r 2 , the efficiency of a...

Macroporous TaON (mac-TaON) is prepared using polymer sphere templating and controlled ammonolysis. In contrast to typical powder synthesis, which gives the β polymorph, mac-TaON is a mixture of β and γ polymorphs. mac-TaON shows twice the activity for photocatalytic hydrogen generation in comparison to mac-TaON when normalised for surface area.

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