pubs.acs.org/NanoLett
Colchicine-Loaded Lipid Bilayer-Coated 50 nm Mesoporous Nanoparticles Efficiently Induce Microtubule Depolymerization upon Cell Uptake Valentina Cauda,†,§ Hanna Engelke,‡,§ Anna Sauer,†,§ Delphine Arcizet,‡,§ Christoph Bra¨uchle,† Joachim Ra¨dler,‡ and Thomas Bein*,† †
Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstrasse 5-13 (E), 81377 Munich, Germany, and ‡ Faculty of Physics and Center for NanoScience (CeNS), University of Munich (LMU), Geschwister-Scholl-Platz 1, 80539 Munich, Germany ABSTRACT We report on a one-step assembly route where supported lipid bilayers (SLB) are deposited on functionalized colloidal mesoporous silica (CMS) nanoparticles, resulting in a core-shell hybrid system (SLB@CMS). The supported membrane acts as an intact barrier against the escape of encapsulated dye molecules. These stable SLB@CMS particles loaded with the anticancer drug colchicine are readily taken up by cells and lead to the depolymerization of microtubules with remarkably enhanced efficiency as compared to the same dose of drug in solution. KEYWORDS Supported lipid bilayer, colloidal mesoporous silica nanoparticles, monodisperse colloidal suspension, drug release-on-demand, colchicine, living cancer cells.
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anoparticles show a vast potential as intelligent drug delivery systems and as nanoagents for medical imaging and in situ diagnostics. Mesoporous silica nanoparticles are particularly interesting candidates due to their ability to encapsulate guest molecules efficiently and specifically.1,2 Their large surface area (between 800 and 1200 m2/g) and pore volume (about 1 cm3/g), their uniform pore diameter, combined with accessible nanoscale morphologies and stable colloidal suspensions3 all point to their potential as powerful drug carriers. An important challenge in the current development is the design of controlled cap systems to prevent uncontrolled and premature release of the drug from the mesopores. Molecular pore sealing systems based on large molecules, clusters or molecular assemblies have been reported.4-6 Such a cap system should also fulfill more specific functions, such as a stimuliresponsive delivery, biocompatibility, and possibly contain specific ligands for cell targeting. An alternative design involves the use of supported lipid bilayers (SLB) to coat mesoporous nanoparticles, which mimic cellular envelopes and should provide several natural advantages.7-9 First, the lipid membrane can enhance circulation time and accumulation in tumor cells as shown for the liposome-based delivery of doxorubicin.10 Moreover, features such as high biocompatibility, low toxicity and low immunogenicity of the
lipid bilayers are important assets for the future use in cancer therapy. Finally, nanoparticle-supported lipid membranes far exceed the structural stability of liposomes and offer narrow size distributions, both factors of key importance for successful drug delivery.7,8,11 In principle, mesoporous nanoparticles can retain and protect the guest molecules before reaching the target cells if an intact lipid bilayer is deposited on the surface, thus minimizing their toxicity and maximizing the drug effectiveness. Brinker and co-workers showed that lipid coating of mesoporous silica can be achieved by fusion with negatively charged liposomes followed by incubation with positively charged liposomes.7 The protocol yielded 100 nm lipidcoated mesoporous nanoparticles capable of retaining 75% of a loaded dye.8 The encapsulation of even smaller nanoparticles in lipid bilayers was reported for fluorescent 50 nm quantum dots (QDs) and 20 nm silica nanoparticles using reverse-phase evaporation methods.12 However, in this case the authors found at least three QDs encapsulated inside a single lipid vesicle due to the difference in size between the QDs and the liposome (300 nm) and the method used for their incorporation. Hence the preparation of intact supported bilayers on mesoporous nanoparticles for long-term encapsulation of a drug load and controlled release after delivery is still a demanding issue. Here we present the efficient preparation of SLB@CMS, that is, single colloidal mesoporous silica (CMS) nanoparticles coated with an intact supported lipid bilayer (SLB) using a solvent-exchange method (Figure 1). We demonstrate the feasibility of this strategy using three different kinds of lipid
* To whom correspondence should be addressed. E-mail:
[email protected]. § These authors have equally contributed to the article. Received for review: 03/20/2010 Published on Web: 06/01/2010
© 2010 American Chemical Society
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FIGURE 1. Schematic depiction of the assembly of colchicine-loaded CMS-nanoparticles. (Left) Adsorption of colchicine (green particles and magnified as molecules) into the core-shell functionalized CMS nanoparticle (gray), followed by assembly of a supported lipid bilayer (free lipids in yellow/red) on the surface of the CMS. (Right) The fully assembled colchicine-loaded SLB@CMS system.
formulations (the neutral phospholipids DOPC and POPC, and a mixture of cationic and neutral lipids DOTAP/DOPC) and 50 nm CMS particles. The integrity of SLB@CMS was characterized by fluorescence cross-correlation spectroscopy (FCCS), dynamic light scattering (DLS), and fluorescence microscopy. To demonstrate the effectiveness of our system for biomedical applications, we chose colchicine, a drug deactivating microtubule polymerization, whose efficiency is enhanced by mediated transport across the cell membrane.13 Here we show that colchicine can be effectively delivered into HuH7 liver cancer cells. The drug is released inside the living cells and inhibits after 120 min the microtubule polymerization and hence induces cell death. We discuss the potential use of SLB@CMS as a drug delivery system with the advantages of providing a stable colloidal suspension in aqueous media, carrying large amounts of drug inside the mesopores (Figure 1). Furthermore, the uptake of colchicine-loaded SLB@CMS into the cells leads to cell death due to intracellular diffusive release of colchicine. This results in a strongly enhanced efficiency of this drug. To prepare a defect-free and intact lipid bilayer supported on single mesoporous silica nanoparticles, we developed the method summarized in Figure 2. The principle relies on the fact that lipids dissolved in ethanolic solution prevail as monomers, while they self-assemble into solid surfacesupported bilayers or liposomes as the water content of the solution is shifted toward 100%vol14 (for details see the Supporting Information). We used three types of lipid mixtures, DOPC, POPC, and a mixture of 30% vol DOTAP-70% vol DOPC (Figure 2d). Lipids were mixed in chloroform, then © 2010 American Chemical Society
desiccated, and finally dispersed in a mixture of 60% vol water and 40% vol ethanol (Figure 2a). The lipids were labeled with 0.04% w fluorescent dyes (Texas red or BODIPY, see S.I.) for subsequent stability and tracking as well as colocalization studies. By suspending the CMS nanoparticles in the lipid solution, a supporting surface is offered for lipid bilayer formation upon water addition to the solvent (up to 95%vol), thus allowing a direct and efficient coverage of the silica surface (Figure 2c). The CMS nanoparticles were synthesized following a previously developed approach.15 The so-called sol-gel method uses tetraethylorthosilicate (TEOS) as silica source and the surfactant cetyltrimethylammonium chloride (CTAC) as pore template. The electrostatic interactions between the positively charged ammonium heads of CTAC and the negatively charged silica species lead to the self-assembly of mesoporous structure with amorphous silica walls and surfactant-templated mesopores. By using the polyalcohol triethanolamine (TEA) during the polymerization of silica, the condensation rate of the silica species is slowed down, thus forming mesoporous nanoparticles growing radially, and resulting in a nonaggregated colloidal suspension of CMS. We have recently developed the synthesis of functionalized core-shell mesoporous silica nanoparticles (based on this radial particle growth),15,16 which enables us to functionalize exclusively the outer nanoparticle surface with amino-propyl functional groups (see Figure 2b and Supporting Information for the synthesis details). After template extraction, the CMS particles show a large mesopore volume. The external aminopropyl surface of these particles was selectively functionalized with the dyes fluorescein isothio2485
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FIGURE 2. Scheme of the synthetic procedure for the formation of SLB on CMS nanoparticles. (a) The lipids in chloroform were mixed with dye-labeled lipids. After chloroform evaporation, the mixture of unlabeled and labeled lipids was desiccated and redispersed in a mixture of 40% vol EtOH/60% vol water. (b) After the synthesis of outer surface amino-functionalized CMS, the amino-propyl groups were labeled with fluorescent dye. The labeled particles were then centrifuged. (c) The lipid solution was added to the centrifuged dye-labeled CMS nanoparticles. Upon addition of water, the SLB was formed on the surface of the CMS nanoparticles. (d) The three kinds of lipids used are DOPC, POPC, and DOTAP (used in a mixture of 30% vol DOTAP and 70% vol DOPC).
cyanate or ATTO 633 NHS ester, as reported in detail in the Supporting Information. Nitrogen sorption in the externally amino-functionalized CMS (Figure 3a) shows the high specific surface area and pore volume, and the narrow pore size distribution (inset of Figure 3a; Table 1) centered at 3.7 nm. Transmission electron microscopy (TEM, Figure 3b) shows spherically shaped nanoparticles with an average size of 50 nm and a wormlike mesoporous structure, also confirmed by the broad (100)-like reflection in the X-ray diffraction pattern (Figure 3c). The effective assembly of the supported lipid bilayers on single CMS nanoparticles was confirmed by several characterization techniques. We ask if the lipid bilayer is indeed tightly bound to the surface of the mesoporous nanoparticle. This can be answered through the analysis of correlated movements of two dye labels, one on the surface of the CMS particle, the other in the lipid bilayer, based on FCCS. This technique analyses the fluorescence intensity fluctuations due to molecules diffusing in and out of a femtoliter detection volume defined by a tightly focused laser beam.17,18 © 2010 American Chemical Society
Autocorrelation of these fluctuations then yields information on diffusion, size and concentration of the molecules. The cross-correlation of the intensity traces, resulting from two species labeled with different colors, gives evidence of correlated movements, for example due to binding of the two species.19 Figure 4a shows the autocorrelation curves of the ATTO 633-labeled CMS and the BODIPY-labeled lipid coating, both revealing diffusion characteristics resulting from monodisperse particles of about 60 nm diameter. The autocorrelation results of both channels are in agreement, suggesting colocalization of CMS and lipids. This coupling is further confirmed by analysis of the cross-correlation function, thus demonstrating the successful lipid coating of the CMS. Evaluation of the colocalization ratios obtained from the FCCS data results in an estimated colocalization of near 100%. The colloidal stability of the SLB@CMS in comparison with the uncoated CMS was shown with DLS (Figure 4b). The uncoated CMS nanoparticles show a monodisperse distribution in ethanol (curve A) with a maximum at 80 nm, which 2486
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110 nm). However, when the SLB is fused with the CMS surface a better stabilization of the nanoparticles in water is observed (curve C) with a monodisperse distribution peaking at 100 nm. These findings not only confirm the formation of the SLB on the CMS nanoparticles but also demonstrate the role of the lipid bilayer as a steric stabilizer preventing the aggregation of CMS nanoparticles in aqueous solution. Using wide-field fluorescence microscopy (Figure 4c), ATTO 633-labeled CMS nanoparticles (red) and BODIPYlabeled POPC lipids (green) can be visualized in both channels. The optical resolution of wide-field fluorescence microscopy is naturally not high enough to allow for a resolution of single SLB@CMS nanoparticles. Here it is used to visually show the colocalization of the two dyes, thus confirming that nearly 100% of the CMS nanoparticles are encapsulated by the lipid bilayer. To show the use of SLB@CMS as a release-on-demand system, we demonstrate that the SLB layer formed on each CMS nanoparticle is compact and defect-free for fluorescent dyes and that it prevents any premature release of these guest molecules from the mesostructure. For this purpose, we encapsulated fluorescent dyes (fluorescein sodium salt and calcein, respectively, for details see Supporting Information) into the mesopores of the CMS and capped the mesopores with one of the three different lipid bilayers (POPC, DOPC, and the mixture DOTAP/DOPC). The dye-loaded SLB@CMS was confined in a tube sealed by a dialysis membrane (Figure 5e), which is placed on top of a fluorescence cuvette filled with water. The dialysis membrane allows only the dye molecules to diffuse into the cuvette volume, thus the monitored fluorescence emission results only from the released guest molecules. If the SLB@CMS remains closed with zero release, no fluorescence emission is detected (see Figure 5a, where the fluoresceinloaded DOPC-SLB@CMS is monitored). For comparison, the release of fluorescein from uncoated CMS nanoparticles (without the lipid bilayer) was also monitored for 1 h, showing a rapid and continuous increase of the fluorescence intensity with time (Figure 5b). While this reference sample releases 100% of the adsorbed guest molecule within 10 min, the DOPC-SLB@CMS nanoparticles show no release for one hour (Figure 5d). In fact, within the accuracy of the experiment we conclude that better than 99.9% of the dye is retained in DOPC-SLB@CMS. After one hour of monitoring without any increase in the fluorescence emission, a membrane-disrupting agent, such as ethanol or the surfactant triton X-100, was added into the tube containing the SLB@CMS. The fluorescence emission shows a rapid increase in intensity due to the prompt release of the dye molecules from the mesoporous particles (Figure 5c). The final fluorescence intensity of both the reference sample and the lysed-SLB@CMS sample, one hour after the lipid lysis, are similar (Figure 5d). The release rate displayed by the SLB@CMS after vesicle lysis appears to be slower than that of the uncoated CMS nanoparticles; we attribute this to
FIGURE 3. Characterization results of mesoporous silica nanoparticles. (a) Nitrogen sorption isotherm and density functional theory (DFT) pore size distribution. (b) Scanning transmission electron microscopy. (c) X-ray diffraction pattern with (100)-like reflection.
TABLE 1. Structural Parameters of the Colloidal Mesoporous Silica Nanoparticles sample
DFT pore size (nm)
pore volume (cm3/g)
BET surface area (m2/g)
CMS
3.77
0.75
1050
suggests moderate agglomeration as compared with the TEM results. The CMS nanoparticles aggregate more distinctly in water (curve B, two distribution peaks at 80 and © 2010 American Chemical Society
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FIGURE 4. Characterization results of SLB@CMS nanoparticles. (a) FCCS of DOTAP/DOPC supported lipid bilayers on CMS nanoparticles. The nanoparticles were labeled with ATTO 633, DOTAP/DOPC with BODIPY. (b) DLS measurements of the CMS nanoparticles in EtOH and water, and of DOTAP/DOPC lipids supported on CMS in water. (c) Fluorescence microscopy image of POPC-supported bilayers on CMS nanoparticles. (Left) ATTO 633-labeled CMS (red); (middle) BODIPY-labeled POPC lipids (green); (right) merged channels (yellow indicates colocalization of CMS and lipids).
the diffusion resistance that might arise from the presence of lysed lipid fragments around the CMS nanoparticles. Similar results were obtained with the two other lipid compositions and with the larger fluorescent molecule calcein. Consequently, the results show the unprecedented efficiency of our SLB@CMS system in capping the mesopores and leading to zero premature release of the adsorbed molecules. The in vitro experiments strongly suggest the potential of SLB@CMS as a drug delivery system. Here we show the delivery of the anticancer drug colchicine from SLB@CMS into HuH7 liver cancer cells (for cell culture and delivery experiments see the Supporting Information). Colchicine binds to tubulin, thus inhibiting microtubule polymerization and leading to cell death. After loading the drug into the CMS mesopores, the CMS particles were centrifuged and then fused with a bilayer of the lipid POPC. The supernatant with residual dissolved colchicine was removed and the drugloaded POPC-SLB@CMS particles were redispersed in a cell culture medium. During the incubation of the cells with loaded nanoparticles, we expect delivery of colchicine into the cell interior upon internalization of POPC-SLB@CMS. To monitor in detail the impact of colchicine-loaded POPC© 2010 American Chemical Society
SLB@CMS on a single cell level, we performed live cell imaging with high-resolution spinning-disk confocal microscopy using two separate detection channels. While the green channel monitored the HuH7 cells expressing GFP-labeled tubulin, the red channel was tuned to detect the fluorescence of the ATTO 633-labeled CMS nanoparticles. The two channels were overlaid to colocalize the SLB@CMS with the tubular network of the HUH7 cells. The spinning-disk confocal microscope also allowed us to acquire z-stacks through the entire cell volume. Taken together, the three spatial dimensions (x,y,z) and the temporal information give us detailed insights into the behavior of the cells incubated with the colchicine-loaded POPC-SLB@CMS. Microtubules are structural components of the cellular cytoskeleton that play an important role in the structure and form of a cell and can be depolymerized by the drug colchicine. For our live cell imaging experiments we used HuH7 liver cancer cells with a GFP-labeled network of microtubules. This well-structured microtubule network can be visualized by fluorescence microscopy, as shown for the untreated cell in Figure 6a. The inset (Figure 6b) displays an HuH7 cell (in green) exposed to colchicine-loaded POPCSLB@CMS nanoparticles (in red) for 25 min. The microtu2488
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FIGURE 5. Fluorescein (FLUO) delivery profile from SLB@CMS. (a) Absence of fluorescence emission of FLUO from FLUO-DOPC-SLB@CMS nanoparticles during the measured interval of 60 min. Note that the y-axis scale displays 10-fold lower values in comparison with the next graphs, since no increase of the fluorescence intensity was detected. (b) Fluorescence emission spectra of FLUO released within 120 min from CMS nanoparticles without lipids. For clarity reasons, we report only the spectra between 0 and 10 min (time lapse: 1 min each). The spectra do not change after 10 min and therefore only the last spectrum at 120 min is shown thereafter. (c) Fluorescence emission spectra of FLUO released from FLUO-DOPC-SLB@CMS after lysis of the lipid bilayer upon triton addition. The spectra were recorded from 60 to 120 min with graph d showing the time dependence. The black line shown in the gray rectangle corresponds to the spectra reported in Figure 5a. (d) Comparison of the FLUO release profiles versus time of the FLUO-DOPC-SLB@CMS sample and the CMS nanoparticles without lipids (the data points correspond to the intensities at the peak maxima at 512 nm in Figure 5a-c). In the latter system, a prompt release of FLUO was observed within 10 min, whereas no release was detected from the lipid supported nanoparticles. Just after triton addition (at 60 min), a fast release of FLUO was observed due to lysis of the lipid. (e) Scheme and photo of the fluorescence cuvette used for the release experiments: the sample was confined in the tube and closed by a cap with a dialysis membrane; the volume of the fluorescence cuvette was filled with water.
bule network still looks intact after this time. This can be attributed to the fact that nearly none of the colchicineloaded POPC-SLB@CMS nanoparticles have been uptaken into the cell at this time (extracted from 3D data of the cell, not shown here). In previous studies, we could show that nontargeted gene delivery lipoplexes and polyplexes show a similarly slow uptake behavior.20,21 In contrast, after 120 min of incubation, cells are observed (see Figure 6c) where the individual microtubule filaments can hardly be recognized. The diffuse green fluorescence arises from the depolymerized microtubules. If one looks for internalized nanoparticles in the cell displayed in Figure 6c by creating a crosssection of the cell volume (Figure 6d), several internalized nanoparticles (in red) are visible in the green cytoplasm. Twenty-four minutes later (at total time of 144 min, Figure 6e) the morphology of the same cell had changed considerably: a shrunk and flat cell surface is observed (see Movie S-1 in the Supporting Information), clearly indicating cell death. We attribute these dramatic changes to the uptake © 2010 American Chemical Society
of the colchicine-loaded POPC-SLB@CMS into the cell, followed by release of the colchicine from the nanoparticles, binding of colchicine to tubulin, microtubule depolymerization and cell death. Three-dimensional reconstructions of the HuH7 cell shown in Figure 6c,e are given in the Supporting Information (Movies S-2 and S-3, Figure S-1 and S-2). To prove that the microtubule depolymerization and cell death are caused by the colchicine drug and not by the carrier itself, the POPC-SLB@CMS nanoparticles without colchicine were also incubated with HuH7 cells. Figure 6f shows a living HuH7 cell with an intact microtubule network after 2 h incubation with the SLB@CMS nanoparticles. Internalization is evident by a z-stack through the cell volume and by the observation of typical intracellular motion of nanoparticles along the microtubular network of the cells (see Movie S-4 in the Supporting Information). We conclude that the cell death cannot be attributed to the lipid-coated carrier itself, but to the effect of the released colchicine molecule. 2489
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FIGURE 6. Drug delivery by colchicine loaded POPC-SLB@CMS nanoparticles to HuH7 liver cancer cells. (a) Spinning disk confocal live cell imaging of untreated HuH7 cells showed a GFP-labeled well-structured microtubule network (green). (b) HuH7 cells with GFP-labeled microtubules (green) were exposed to colchicine-loaded POPC-SLB@CMS (CMS labeled with ATTO 633, shown in red) for 25 min. The microtubule network still appears to be intact. (c) After 120 min, the microtubule network disappeared and a diffuse fluorescence due to microtubule depolymerization was observed. (d) Side view of the HuH7 cell represented in panel c, where the internalized nanoparticles (in yellow, due to the overlay of green and red colors) are visible. Several other nanoparticles (in red) are on the top of the cell. (e) After 144 min the cell morphology was disintegrated, confirming cell death. (f) HuH7 cells (green) after 2 h of incubation with POPC-SLB@CMS without colchicine. (g) Colchicine release from POPC-SLB@CMS in vitro, using the dialysis-capped tube fitting on the fluorescence cuvette. The molecule showed a slight permeability through the lipid bilayer. After the injection of ethanol, the lipid bilayer was lysed, leading to a prompt release of colchicine. (h) Dissolved colchicine from POPC-SLB@CMS confined into the dialysis-capped tube on the cell culture holder. After 6 h the microtubule network of the HuH7 cells was still intact as shown by live cell imaging. Thus the same dose of colchicine released from CMS to the cell culture medium did not induce the tubulin depolymerization and cell death.
To clarify in more detail how colchicine is released from the SLB@CMS nanoparticles, we performed live cell imaging experiments with nanoparticles, where the CMS part is labeled with ATTO 633 and the lipids are labeled with BODIPY. As cells we used HuH7 cells without GFP labeling of the microtubules in order not to interfere with the two dyes at the nanoparticles. The uptake of the SLB@CMS © 2010 American Chemical Society
nanoparticles by the cells was monitored and the overlay of the red ATTO 633 channel and the green BODIPY channel clearly indicates colocalization of both components over the whole time span of the experiments from 25 min up to 4 h (see Figure S-3 and Movie S-5 in the S. I.). This means that the lipid layer around the CMS nanoparticles seems not to be detached by the uptake process. Therefore the question 2490
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arises how colchicine is delivered into the cytosol from the SLB@CMS nanoparticles uptaken into the cell. It is known that colchicine has a small but finite permeability across cell membranes.13,22 Thus it may also be able to cross the lipid bilayer in the SLB@CMS nanoparticles. Control experiments (Figure 6g) to clarify this issue were performed using the same in vitro dialysis assay as described in Figure 5e. Indeed, monitoring the cuvette during 2 h showed a slight release of colchicine within the first 60 min, reaching a plateau thereafter. Upon lipid displacement by addition of ethanol, a significant increase of the fluorescence intensity was observed. This shows that colchicine is slightly membrane permeable, but the SLB prevents a prompt release of the drug out of the mesopores. Therefore, we propose as a mechanism for colchicine delivery an initial uptake of the SLB@CMS particles into the cell followed by intracellular release of colchicine via diffusion through the mostly intact lipid bilayer. To investigate the effect of free colchicine potentially leached from the SLB@CMS nanoparticles into the cell culture medium, we applied the dialysis setup to the live cell imaging experiment (Figure 6h). The cells were exposed to the same concentration of colchicine-loaded POPC-SLB@CMS as used in the previously described in vivo experiment (see Figure 6b-e). Even after 6 h of exposure to free colchicine diffusing out of the drug-loaded POPC-SLB@CMS, the microtubule network remained intact and no cell death was observed. This finding clearly shows that the amount of colchicine, leaking out of the SLB without nanoparticle uptake into the cells, is too low to trigger cell death. In summary, we have developed an efficient and reproducible method, based on solvent exchange, to encapsulate individual core-shell CMS nanoparticles of 50 nm diameter with an intact lipid bilayer. Dual color FCCS of the labeled CMS nanoparticles and lipids shows that the SLB@CMS are monodisperse and that they form stable colloidal suspensions in aqueous solutions. The novel SLB@CMS nanoparticles feature significantly increased stability of the supported lipid membrane in comparison to the corresponding free liposome and a high capacity for the incorporation of drugs into the mesopores. In vitro experiments show the complete sealing of the CMS nanoparticle by the lipid bilayer and the absence of premature release of guest molecules such as dyes and prove the stability of the SLB acting as a capping system. The in vitro displacement of the lipid bilayer by ethanol or triton leads to the opening of the mesopores, thus enabling a tunable release-on-demand of the adsorbed molecules. As a proof of principle, we showed the delivery of the microtubule depolymerizing drug colchicine into HuH7 liver cancer cells. This experiment clearly exposes the important role of the SLB, mostly preventing the release of the drug under undesired conditions and allowing delivery into the cell by uptake of the nanoparticles. The microtubule network of the cells is destroyed within 2 h of incubation with the © 2010 American Chemical Society
colchicine-SLB@CMS nanoparticles, thus showing an enhanced effect compared to the same dose of colchicine in solution. We believe that the enhancement is due to the fact that colchicine delivery mediated by SLB@CMS nanoparticles results in small concentrated doses rather than slow infiltration of colchicine from a rather diluted extracellular pool. This enhancement effect, if substantiated in systemic delivery, would improve cancer drug administration and consequently be important in clinical applications such as chemotherapy protocols. Our feasibility study encourages further development of the SLB@CMS system toward targeted drug delivery and controlled local release strategies in cancer therapy. Acknowledgment. Support from DFG-SFB 486 and 749, from the NIM and CIPSM Excellence Cluster (LMU Mu¨nchen), and CeNS is gratefully acknowledged. A.S. and H.E. thank the Elitenetzwerk Bayern for funding and A.S. additionally thanks the Ro¨mer foundation for support. The authors gratefully acknowledge the help of Bastian Ru¨hle for the preparation of Figure 1 and the help of Monika Franke with cell culture. Supporting Information Available. The CMS nanoparticle synthesis and its labeling, the preparation of the lipids and of the SLB@CMS and their loading with guest molecules, the experimental methods and equipment as well as spinning disk confocal live cell imaging, 3D reconstructions, and movies. This material is available free of charge via the Internet at http://pubs.acs.org. REFERENCES AND NOTES (1) (2)
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