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Evaluation of Three Morphologically Distinct Virus-Like Particles as Nanocarriers for Convection-Enhanced Drug Delivery to Glioblastoma - PubMed

  • ️Mon Jan 01 2018

Evaluation of Three Morphologically Distinct Virus-Like Particles as Nanocarriers for Convection-Enhanced Drug Delivery to Glioblastoma

Joel A Finbloom et al. Nanomaterials (Basel). 2018.

Abstract

Glioblastoma is a particularly challenging cancer, as there are currently limited options for treatment. New delivery routes are being explored, including direct intratumoral injection via convection-enhanced delivery (CED). While promising, convection-enhanced delivery of traditional chemotherapeutics such as doxorubicin (DOX) has seen limited success. Several studies have demonstrated that attaching a drug to polymeric nanoscale materials can improve drug delivery efficacy via CED. We therefore set out to evaluate a panel of morphologically distinct protein nanoparticles for their potential as CED drug delivery vehicles for glioblastoma treatment. The panel consisted of three different virus-like particles (VLPs), MS2 spheres, tobacco mosaic virus (TMV) disks and nanophage filamentous rods modified with DOX. While all three VLPs displayed adequate drug delivery and cell uptake in vitro, increased survival rates were only observed for glioma-bearing mice that were treated via CED with TMV disks and MS2 spheres conjugated to doxorubicin, with TMV-treated mice showing the best response. Importantly, these improved survival rates were observed after only a single VLP⁻DOX CED injection several orders of magnitude smaller than traditional IV doses. Overall, this study underscores the potential of nanoscale chemotherapeutic CED using virus-like particles and illustrates the need for further studies into how the overall morphology of VLPs influences their drug delivery properties.

Keywords: bioconjugation; convection-enhanced delivery; doxorubicin; drug delivery; glioblastoma; protein-based nanomaterials; tobacco mosaic virus; viral capsid; virus-like particles.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1

Panel of virus-like particles under evaluation. Three different nanocarriers composed of MS2 spheres, TMV disks and nanophage filamentous rods were tested to determine drug delivery efficacies. Each VLP contains reactive handles for bioconjugation, such as cysteines (red), reactive amines (green), or noncanonical p-aminophenylalanine moieties (purple).

Figure 2
Figure 2

Doxorubicin (DOX) and PEG conjugation to virus-like particles for drug delivery studies. (a) Bioconjugation scheme for the modification of MS2 with (a) DOX–EMCH and (b) PEG. DOX–VLP conjugates contain an acid-labile hydrazone linkage, which is anticipated to cleave upon VLP endocytosis and degradation. Modification schemes for TMV and nanophage are available in the Supporting Information. (c) Each VLP was modified with DOX–EMCH using maleimide addition to cysteine residues (MS2, TMV) or to thiols synthetically installed onto lysine residues (nanophage) as shown in Figure S1. All VLPs were modified with PEG using either oxidative couplings (MS2, TMV) or NHS ester reactions (nanophage) to improve biodistribution.

Figure 3
Figure 3

VLP delivery of doxorubicin to U87-MG glioblastoma cells. U87-MG glioblastoma cells were treated with varying amounts of VLP–DOX conjugates for 72 h. Significant cell death was observed for all VLPs tested. Treatment with the VLPs alone displayed no toxicity (data not shown).

Figure 4
Figure 4

VLP-DOX uptake into U87-MG cells at 48 h. Uptake kinetics of VLP-DOX conjugates into U87-MG glioblastoma cells were monitored in the green channel to detect DOX fluorescence. Data are presented with consistent scaling. Initial intensities are artificially high due to the presence of autofluorescent compounds in the cell media. Upon photobleaching, the FLI drops to more accurate baselines. Both (a) MS2 and (b) TMV demonstrated significant cellular uptake, while the uptake of (c) nanophage (NP) was markedly slower. The TMV data appeared previously in reference [30].

Figure 5
Figure 5

Evaluation of VLP panel for glioblastoma treatment. MS2 spheres, TMV disks and nanophage rods bearing DOX payloads of 20 µg/kg were injected via convection-enhanced delivery infusion (CED) into U87-MG glioma-bearing mice. (a) Tumor growth analysis suggested modest tumor growth inhibition from MS2 and TMV-treated groups. (b) Kaplan-Meier survival curves of mice with U87-MG glioma. The survival curve results suggest improved efficacy with TMV–DOX treatment.

Figure 6
Figure 6

Tumor size dependence of mouse response to VLP treatment. Treatment groups could be divided into two categories based on tumor size as measured by bioluminescence intensity (BLI). Small tumors (as defined by a BLI < 107 AU) showed significantly increased response to CED treatment in the case of TMV and MS2 treated mice when compared to larger tumors (BLI > 107 AU). This BLI cutoff led to a relatively even distribution of mice within each treatment group with the exception of Lipo–DOX, where only two mice had large tumors. Both MS2–DOX and TMV–DOX treatment of small tumors led to significantly enhanced survival when compared to PBS treatment. ** p < 0.05. *** p < 0.01 as measured by log rank test of survival points. See Supporting Information Figures S5–S7 for the tumor size and survival data for individual animals.

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