Treatment of glioblastoma using multicomponent silica nanoparticles

Abstract

Glioblastomas (GBMs) remain highly lethal. This partially stems from the presence of brain tumor initiating cells (BTICs), a highly plastic cellular subpopulation that is resistant to current therapies. In addition to resistance, the blood-brain barrier limits the penetration of most drugs into GBMs. To effectively deliver a BTIC-specific inhibitor to brain tumors, we developed a multicomponent nanoparticle, termed Fe@MSN, which contains a mesoporous silica shell and an iron oxide core. Fibronectin-targeting ligands directed the nanoparticle to the near-perivascular areas of GBM. After Fe@MSN particles deposited in the tumor, an external low-power radiofrequency (RF) field triggered rapid drug release due to mechanical tumbling of the particle resulting in penetration of high amounts of drug across the blood-brain tumor interface and widespread drug delivery into the GBM. We loaded the nanoparticle with the drug 1400W, which is a potent inhibitor of the inducible nitric oxide synthase (iNOS). It has been shown that iNOS is preferentially expressed in BTICs and is required for their maintenance. Using the 1400W-loaded Fe@MSN and RF-triggered release, in vivo studies indicated that the treatment disrupted the BTIC population in hypoxic niches, suppressed tumor growth and significantly increased survival in BTIC-derived GBM xenografts.

Keywords: brain tumor initiating cells; brain tumors; glioma stem cells; multicomponent silica nanoparticles; triggered drug release.

Figure 1.. Illustration of multicomponent nanoparticle.

(a) The Fe@MSN nanoparticle consists of an iron oxide core surrounded by a drug-loaded mesoporous silica shell. (b) The drug cargo is released from the nanoparticles is using an external low-power radiofrequency (RF) field at frequencies of 50 kHz, which forces the particle to vibrate giving sufficient energy to the drug molecules to escape the silica shell. (c) To eliminate the resistant cell subpopulations of GBMs in the hypoxic regions, we will deliver an anti-BTIC drug using the Fe@MSN nanoparticle.

Figure 2.

Synthesis and characterization of the nanoparticles. (a) TEM image of the nanoparticles shows the mesoporous silica shell and the iron oxide core. (b) Different drugs were loaded into Fe@MSN nanoparticles including the iNOS inhibitor (1400W) and the chemotherapeutic drug (DOX). (c) The zeta potential of the nanoparticle was measured in 1M KCl using a Malvern Zeta Potential Analyzer. (d) Drug release is shown from the DOX-loaded nanoparticle and the 1400W-loaded nanoparticle after a 30-min application of the RF field at 50 kHz. (e) The release of 1400W was measured after different duration of exposure to the RF field. (f) The drug release from Fe@MSN was measured at different times in the absence of RF (n=3; two-tailed t-test; n.s.=not significant).

Figure 3.

Histological evaluation of the therapeutic efficacy of the 1400W-loaded Fe@MSN treatment in vivo. Immunohistochemistry was performed to confirm the deposition of Fe@MSN in hypoxic regions enriched with brain tumor initiating cells. Mice bearing orthotopic GL261 tumors were euthanized 24 h after a single injection of Fe@MSN loaded with 1400W at a dose of 10 mg/kg drug. Representative images are shown from neighboring histological sections that were stained for (a) endothelial cells (CD31), hypoxia (pimonidazole HCl), nanoparticles (Prussian Blue), fibronectin, and glioma stem cell markers (OLIG2 and SOX2) and apoptosis (TUNEL) in the absence of RF (b) or with RF (c).

Figure 4.

Histological assessment of the response of brain tumor-initiating cells (BTICs) to the 1400W-loaded Fe@MSN in a semi-quantitative manner. The number of glioma cells stained for SOX2 or OLIG2 was counted in multiple histological sections (3 slices) per tumor (n=3 mice in each group; unpaired t-test; P value **0.006, ***0.0003).

Figure 5.

Measurement of therapeutic efficacy of various treatments in vivo using longitudinal bioluminescence imaging (BLI). Drugs were administered via a tail vein injection in mice with orthotopic GL261 brain tumor on day 6, 7 and 9 after tumor inoculation. Treatments included a combination of free DOX (5 mg/kg) and 1400W (10 mg/kg), TMZ-loaded Fe@MSN (5 mg/kg), DOX-loaded Fe@MSN (5 mg/kg) or a cocktail containing DOX-loaded Fe@MSN (5 mg/kg) and 1400W-loaded Fe@MSN (10 mg/kg). When the RF field was used, the animals were subjected to the RF field (5 mT, 50 kHz) for 60 min. The whole head BLI emission was quantified (n=7 mice in each group; unpaired t-test P=0.028).

Figure 6.

Survival curves. (a) Mice bearing orthotopic 9L glioma were treated with DOX-loaded nanoparticles and 1400W-loaded nanoparticles (+RF), liposomal DOX (+RF), and free unmodified TMZ (+RF) or 1400W + DOX (+RF) and the untreated group (n=8 mice in each group). Depending on the drug, the dose of each formulation contained 5 mg DOX, 10 mg 1400W and 10 mg TMZ per kg of body weight. Treatments were intravenously injected four times at day 2, 3, 6 and 7 after tumor inoculation (blue arrows). Statistical significance of the survival times was determined using the log-rank (Mantel-Cox) test (P<0.0001). (b) The average % change of body weight is shown for animals treated with the DOX-loaded nanoparticles and 1400W-loaded nanoparticles (+RF) and a few representative treatments. (c) The average weight progression of animals is shown after treatment with the DOXloaded nanoparticles and 1400W-loaded nanoparticles (+RF).

Figure 7.

Survival curves. Mice with orthotopic T4121 glioma were treated with DOX-loaded nanoparticles and 1400W-loaded nanoparticles (+RF), or 1400W + DOX (+RF) (n=8 mice in each group). The dose of each formulation contained 5 mg DOX and 10 mg 1400W per kg of body weight. Treatments were intravenously injected three times at day 4, 6, and 14 after tumor inoculation (blue arrows). Statistical significance of the survival times was determined using the log-rank (Mantel-Cox) test (P<0.0001).