After targeting the nanoparticle to brain tumors, widespread drug delivery to the entire tumor is triggered by a radiofrequency field.

No abstract

Glioblastoma multiforme (GBM) remains 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, a multicomponent nanoparticle, termed Fe@MSN, which contains a mesoporous silica shell and an iron oxide core, is developed. Fibronectin-targeting ligands direct the nanoparticle to the near-perivascular areas of GBM. After Fe@MSN particles are deposited in the tumor, an external low-power radiofrequency (RF) field triggers 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. The nanoparticle is loaded with the drug 1400W, which is a potent inhibitor of the inducible nitric oxide synthase (iNOS). It is 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 indicate that the treatment disrupts the BTIC population in hypoxic niches, suppresses tumor growth and significantly increases survival in BTIC-derived GBM xenografts.

Deposition of nanoparticles to tumors often can be enhanced by targeting receptors overexpressed in a tumor. However, a tumor may exhibit a finite number of a biomarker that is accessible and targetable by nanoparticles, limiting the available landing spots. To explore this, we selected two different biomarkers that effectively home nanoparticles in brain tumors. Specifically, we used either an α v β 3 integrin-targeting peptide or a fibronectin-targeting peptide as a ligand on nanoparticles termed RGD-NP and CREKA-NP, respectively. In mouse models of glioblastoma multiforme, we systemically injected the nanoparticles loaded with a cytotoxic drug at different doses ranging from 2 to 8 mg/kg drug. The upper dose threshold of RGD-NP is ∼2 mg/kg. CREKA-NP reached its upper dose threshold at 5 mg/ kg. For both targeted nanoparticle variants, higher dose did not ensure higher intratumoral drug levels, but it contributed to elevated off-target deposition and potentially greater toxicity. A cocktail combining RGD-NP and CREKA-NP was then administered at a dose corresponding to the upper dose threshold for each formulation resulting in a 3-fold higher intratumoral deposition than the individual formulations. The combination of the two different targeting schemes at the appropriate dose for each nanoparticle variant facilitated remarkable increase in intratumoral drug levels that was not achievable by a sole targeting nanoparticle alone.