In contrast to similarly functionalized nanoparticles, endocytosed microparticles were not contained within a lysosome. of mesoporous silica particles involve simultaneously grafting two types of organosilanes to the silica, which cannot provide a controlled spatial distribution of functional groups. development of mesoporous silica particles as drug delivery devices. Nanoparticle-based drug-delivery brokers have made strides in the past decade,18,19 but questions remain about the acute and/or chronic toxicities of nanoparticles.20C23 As an alternative to nanoparticles, particles with KN-92 phosphate diameters in the micrometer range (microparticles) could avoid many of the toxicity issues of nanoparticles while retaining the ability to be functionalized with the moieties for cell uptake and targeting that are important in drug delivery. Although a variety of mesoporous particles are available for these experiments, we used a type of mesoporous silica called APMS (acid-prepared mesoporous spheres).13,24C27 This material has a KN-92 phosphate spherical particle morphology that is easily observed by microscopy, and a particle diameter that can be varied from 1 to 10 m by simple manipulation of synthesis conditions. In addition, the pore structure is usually disordered and highly interconnected, allowing molecules to diffuse very easily throughout the particles interiors, and the pore diameter can also be varied between 2 and 10 nm. Other microparticles KN-92 phosphate for drug delivery have previously been prepared from biodegradable polymers,28,29 but mesoporous silica microparticles are an especially attractive delivery device because the large internal pore volume and surface area of these materials allow large amounts of molecular material to be adsorbed and released. In contrast to crystalline silicas,30,31 numerous studies have shown no adverse long-term health effects or developmental effects due to exposure to amorphous silicas by several routes of administration.32C36 Moreover, silica can be easily modified for tissue-specific targeting using a wide array of functionalization strategies.37,38 In a recent report, we showed that a surface modification with a short poly(ethylene glycol) chain, tetraethylene glycol (TEG), allowed APMS to be readily taken up by malignant mesothelioma (MM) KN-92 phosphate cells and without any adverse effects.39 TEG enhanced the fusion of the particles with plasma membranes and facilitated uptake by cells. In related work, we found that TEG-modified APMS loaded with the chemotherapeutic doxorubicin were 30 to 50 occasions more effective in killing MM cells lifetime of the particles.6,11,47,48 Open in a separate window Determine 2 Images of particles labeled with either TEG (APMS-TEG, A-D) or anti-mesothelin (APMS-ME1, E-H) interacting with cells 4 h after their addition to MM cells. SEM images showed that only particles transporting the TEG functional group were internalized by cells (arrows in A and B). APMS-TEG particles directly exposed to cytoplasm were observed in TEM (D). The arrow in image G indicates the lone APMS-ME1 particle found within an MM cell; it is enlarged in image H. In our next set of experiments, we compared the uptake of APMS-ME1 and APMS-TEG(ME1) to study whether bifunctionally altered particles were taken up as readily as particles modified only with TEG. In these experiments, particles were labeled with a fluorescent molecule exclusively in the pores by using a diffusion-controlled deprotection strategy previously explained by our group,13 and confocal laser scanning microscopy was used to provide a three-dimensional view of particle uptake by MM cells. To fluorescently Ncam1 tag the particles, an Fmoc-protected aminopropylsilane was reacted with APMS and a rapid deprotection of the external amines (20 min) was performed with 5% piperidine in with an antibody to mesothelin (APMS-ME1, A and B), or particles altered with TEG and the antibody (APMS-TEG(ME1), C and D) for 4 h. While particles were found on the outer membranes of all cells, only those particles with TEG were found within the cells; background fluorescence observed in panel B is KN-92 phosphate usually from particles located outside the focal plane. (Bar = 20 m in each image). The specificity of the uptake of bifunctionally.