Enhancing Ocular Drug Delivery: The Effect of Physicochemical Properties of Nanoparticles on the Mechanism of Their Uptake by Human Cornea Epithelial Cells.

This study investigates the effect of nanoparticle size and surface chemistry on interactions of the nanoparticles with human cornea epithelial cells (HCECs). Poly(lactic-co-glycolic) acid (PLGA) nanoparticles were synthesized using the emulsion-solvent evaporation method and surface modified with mucoadhesive (alginate [ALG] and chitosan [CHS]) and mucopenetrative (polyethylene glycol [PEG]) polymers. Particles were found to be monodisperse (polydispersity index (PDI) below 0.2), spherical, and with size and zeta potential ranging from 100 to 250 nm and from -25 to +15 mV, respectively. Evaluation of cytotoxicity with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay indicated that incubating cells with nanoparticles for 24 h at concentrations up to 100 µg/mL caused only mild toxicity (70-100% cell viability). Cellular uptake studies were conducted using an in vitro model developed with a monolayer of HCECs integrated with simulated mucosal solution. Evaluation of nanoparticle uptake revealed that energy-dependent endocytosis is the primary uptake mechanism. Among the different nanoparticles studied, 100 nm PLGA NPs and PEG-PLGA-150 NPs showed the highest levels of uptake by HCECs. Additionally, uptake studies in the presence of various inhibitors suggested that macropinocytosis and caveolae-mediated endocytosis are the dominant pathways. While clathrin-mediated endocytosis was found to also be partially responsible for nanoparticle uptake, phagocytosis did not play a role within the studied ranges of size and surface chemistries. These important findings could lead to improved nanoparticle-based formulations that could improve therapies for ocular diseases.

Improving Cancer Targeting: A Study on the Effect of Dual-Ligand Density on Targeting of Cells Having Differential Expression of Target Biomarkers.

Silica nanoparticles with hyaluronic acid (HA) and folic acid (FA) were developed to study dual-ligand targeting of CD44 and folate receptors, respectively, in colon cancer. Characterization of particles with dynamic light scattering showed them to have hydrodynamic diameters of 147-271 nm with moderate polydispersity index (PDI) values. Surface modification of the particles was achieved by simultaneous reaction with HA and FA and results showed that ligand density on the surface increased with increasing concentrations in the reaction mixture. The nanoparticles showed minimal to no cytotoxicity with all formulations showing ≥ 90% cell viability at concentrations up to 100 µg/mL. Based on flow cytometry results, SW480 cell lines were positive for both receptors, the WI38 cell line was positive for CD44 receptor, and Caco2 was positive for the folate receptor. Cellular targeting studies demonstrated the potential of the targeted nanoparticles as promising candidates for delivery of therapeutic agents. The highest cellular targeting was achieved with particles synthesized using folate:surface amine (F:A) ratio of 9 for SW480 and Caco2 cells and at F:A = 0 for WI38 cells. The highest selectivity was achieved at F:A = 9 for both SW480:WI38 and SW480:Caco2 cells. Based on HA conjugation, the highest cellular targeting was achieved at H:A = 0.5-0.75 for SW480 cell, at H:A = 0.75 for WI38 cell and at H:A = 0.5 for Caco2 cells. The highest selectivity was achieved at H:A = 0 for both SW480:WI38 and SW480:Caco2 cells. These results demonstrated that the optimum ligand density on the nanoparticle for targeting is dependent on the levels of biomarker expression on the target cells. Ongoing studies will evaluate the therapeutic efficacy of these targeted nanoparticles using in vitro and in vivo cancer models.

MRI-traceable theranostic nanoparticles for targeted cancer treatment.

Current cancer therapies, including chemotherapy and radiotherapy, are imprecise, non-specific, and are often administered at high dosages - resulting in side effects that severely impact the patient's overall well-being. A variety of multifunctional, cancer-targeted nanotheranostic systems that integrate therapy, imaging, and tumor targeting functionalities in a single platform have been developed to overcome the shortcomings of traditional drugs. Among the imaging modalities used, magnetic resonance imaging (MRI) provides high resolution imaging of structures deep within the body and, in combination with other imaging modalities, provides complementary diagnostic information for more accurate identification of tumor characteristics and precise guidance of anti-cancer therapy. This review article presents a comprehensive assessment of nanotheranostic systems that combine MRI-based imaging (T1 MRI, T2 MRI, and multimodal imaging) with therapy (chemo-, thermal-, gene- and combination therapy), connecting a range of topics including hybrid treatment options (e.g. combined chemo-gene therapy), unique MRI-based imaging (e.g. combined T1-T2 imaging, triple and quadruple multimodal imaging), novel targeting strategies (e.g. dual magnetic-active targeting and nanoparticles carrying multiple ligands), and tumor microenvironment-responsive drug release (e.g. redox and pH-responsive nanomaterials). With a special focus on systems that have been tested in vivo, this review is an essential summary of the most advanced developments in this rapidly evolving field.

Development and application of high-throughput screens for the discovery of compounds that disrupt ErbB4 signaling: Candidate cancer therapeutics.

Whereas recent clinical studies report metastatic melanoma survival rates high as 30-50%, many tumors remain nonresponsive or become resistant to current therapeutic strategies. Analyses of The Cancer Genome Atlas (TCGA) skin cutaneous melanoma (SKCM) data set suggests that a significant fraction of melanomas potentially harbor gain-of-function mutations in the gene that encodes for the ErbB4 receptor tyrosine kinase. In this work, a drug discovery strategy was developed that is based on the observation that the Q43L mutant of the naturally occurring ErbB4 agonist Neuregulin-2beta (NRG2ß) functions as a partial agonist at ErbB4. NRG2ß/Q43L stimulates tyrosine phosphorylation, fails to stimulate ErbB4-dependent cell proliferation, and inhibits agonist-induced ErbB4-dependent cell proliferation. Compounds that exhibit these characteristics likely function as ErbB4 partial agonists, and as such hold promise as therapies for ErbB4-dependent melanomas. Consequently, three highly sensitive and reproducible (Z' > 0.5) screening assays were developed and deployed for the identification of small-molecule ErbB4 partial agonists. Six compounds were identified that stimulate ErbB4 phosphorylation, fail to stimulate ErbB4-dependent cell proliferation, and appear to selectively inhibit ErbB4-dependent cell proliferation. Whereas further characterization is needed to evaluate the full therapeutic potential of these molecules, this drug discovery platform establishes reliable and scalable approaches for the discovery of ErbB4 inhibitors.

Improving the Size Homogeneity of Multicore Superparamagnetic Iron Oxide Nanoparticles.

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely explored for use in many biomedical applications. Methods for synthesis of magnetic nanoparticle (MNP), however, typically yield multicore structures with broad size distribution, resulting in suboptimal and variable performance in vivo. In this study, a new method for sorting SPIONs by size, labeled diffusive magnetic fractionation (DMF), is introduced as an improvement over conventional magnetic field flow fractionation (MFFF). Unlike MFFF, which uses a constant magnetic field to capture particles, DMF utilizes a pulsed magnetic field approach that exploits size-dependent differences in the diffusivity and magnetic attractive force of SPIONs to yield more homogenous particle size distributions. To compare both methods, multicore SPIONs with a broad size distribution (polydispersity index (PdI) = 0.24 ± 0.05) were fractionated into nine different-sized SPION subpopulations, and the PdI values were compared. DMF provided significantly improved size separation compared to MFFF, with eight out of the nine fractionations having significantly lower PdI values (p value < 0.01). Additionally, the DMF method showed a high particle recovery (>95%), excellent reproducibility, and the potential for scale-up. Mathematical models were developed to enable optimization, and experimental results confirmed model predictions (R2 = 0.98).

Quantitative, real-time in vivo tracking of magnetic nanoparticles using multispectral optoacoustic tomography (MSOT) imaging.

The goal of this work was to demonstrate real-time tracking of in vivo nanoparticle concentrations utilizing multispectral optoacoustic tomography (MSOT). Combining the high contrast of optical imaging with the high resolution of ultrasound imaging, MSOT was utilized for non-invasive, real-time tomographic imaging of particles in mice and the results calibrated against analysis of tissue samples with electron paramagnetic resonance (EPR) spectroscopy. In a longitudinal study, the pharmacokinetics (pK) and biodistribution of Cyanine-7 (Cy7) conjugated superparamagnetic iron oxide nanoparticles (Cy7-SPIONs) were monitored after intravenous administration into the tail vein of healthy B6-albino mice. Concentrations of Cy7-SPIONs determined by MSOT image analysis of the liver, spleen, and kidneys showed excellent agreement with EPR data obtained on tissue samples ‒ validating MSOT's ability to quantify SPION concentrations with high spatial resolution. Both methods of analysis indicated highest accumulation of Cy7-SPIONs in the liver followed by the spleen, and negligible accumulation in the kidneys; SPION accumulation in organs with high concentrations of mononuclear phagocytic system macrophages is typical. Additionally, our study observed that particles modified with a 2 kDa polyethylene glycol (PEG) demonstrated significantly prolonged half-life in circulation compared to particles with 5 kDa PEG. The study demonstrates the potential of Cy7-SPIONs and MSOT for quantitative localization of magnetic nanoparticles in vivo, which can potentially be used to study their toxicity, quantify the efficacy of targeted drug delivery (e.g. within tumors), and their use as a multi-modal diagnostic agent to monitor disease progression.

Nanoparticle-based probes to enable noninvasive imaging of proteolytic activity for cancer diagnosis.

Proteases play a key role in tumor biology, with high expression levels often correlating with poor prognosis for cancer patients - making them excellent disease markers for tumor diagnosis. Despite their significance, quantifying proteolytic activity in vivo remains a challenge. Nanoparticles, with their ability to serve as scaffolds having unique chemical, optical and magnetic properties, offer the promise of merging diagnostic medicine with material engineering. Such nanoparticles can interact preferentially with proteases enriched in tumors, providing the ability to assess disease state in a noninvasive and spatiotemporal manner. We review recent advances in the development of nanoparticles for imaging and quantification of proteolytic activity in tumor models, and prognosticate future advancements.

Toward Accumulation of Magnetic Nanoparticles into Tissues of Small Porosity.

Magnetic concentration of drug-laden magnetic nanoparticles has been proven to increase the delivery efficiency of treatment by 2-fold. In these techniques, particles are concentrated by the presence of a magnetic source that delivers a very high magnetic field and a strong magnetic field gradient. We have found that such magnetic conditions cause even 150 nm particles to aggregate significantly into assemblies that exceed several micrometers in length within minutes. Such assembly sizes exceed the effective intercellular pore size of tumor tissues preventing these drug-laden magnetic nanoparticles from reaching their target sites. We demonstrate that by using dynamic magnetic fields instead, we can break up these magnetic nanoparticles while simultaneously concentrating them at target sites. The dynamic fields we investigate involve precessing the field direction while maintaining a field gradient. Manipulating the field direction drives the particles into attractive and repulsive configurations that can be tuned to assemble or disassemble these particle clusters. Here, we develop a simple analytic model to describe the kinetic thresholds of disassembly and we compare both experimental and numerical results of magnetic particle suspensions subjected to dynamic fields. Finally we apply these methods to demonstrate penetration in a porous scaffold with a similar pore size to that expected of a tumor tissue.

PTD-Modified ATTEMPTS for Enhanced Toxin-based Cancer Therapy: An In Vivo Proof-of-Concept Study.

PURPOSE: To investigate the feasibility of applying PTD-modified ATTEMPTS (Antibody Targeted Triggered Electrically Modified Prodrug-Type Strategy) for enhanced toxin therapy for the treatment of cancer. METHODS: A heparin-functionalized murine anti-CEA monoclonal antibody (mAb), T84.66-heparin (T84.66-Hep), was chemically synthesized and characterized for specific binding to CEA overexpressed cells. The T84.66-Hep was then applied to the PTD-modified ATTEMPTS approach and the crucial features of the drug delivery system (DDS), 'antibody targeting' and 'heparin/protamine-based prodrug', were evaluated in vitro to examine whether it could selective delivery a PTD-modified toxin, recombinant TAT-gelonin chimera (TAT-Gel), to CEA high expression cancer cells (LS174T). Furthermore, the feasibility of the drug delivery system (DDS) was assessed in vivo by biodistribution and efficacy studies using LS174T s.c. xenograft tumor bearing mice. RESULTS: T84.66-Hep displayed specific binding, but limited internalization (35% after 48 h incubation) to CEA high expression LS174T cells over low expression HCT116 cells. When mixed together with TAT-Gel, the T84.66-Hep formed a strong yet reversible complex. This complex formation provided an effective means of active tumor targeting of TAT-Gel, by 1) directing the TAT-Gel to CEA overexpressed tumor cells and 2) preventing nonspecific cell transduction to non-targeted normal cells. The cell transduction of TAT-Gel could, however, be efficiently reversed by addition of protamine. Feasibility of in vivo tumor targeting and "protamine-induced release" of TAT-Gel from the T84.66-Hep counterpart was confirmed by biodistribution and preliminary efficacy studies. CONCLUSIONS: This study successfully demonstrated in vitro and in vivo the applicability of PTD-modified ATTEMPTS for toxin-based cancer therapy.

Effects of Iron-Oxide Nanoparticle Surface Chemistry on Uptake Kinetics and Cytotoxicity in CHO-K1 Cells.

Superparamagnetic iron-oxide nanoparticles (SPIONs) show great promise for multiple applications in biomedicine. While a number of studies have examined their safety profile, the toxicity of these particles on reproductive organs remains uncertain. The goal of this study was to evaluate the cytotoxicity of starch-coated, aminated, and PEGylated SPIONs on a cell line derived from Chinese Hamster ovaries (CHO-K1 cells). We evaluated the effect of particle diameter (50 and 100 nm) and polyethylene glycol (PEG) chain length (2k, 5k and 20k Da) on the cytotoxicity of SPIONs by investigating cell viability using the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and sulforhodamine B (SRB) assays. The kinetics and extent of SPION uptake by CHO-K1 cells was also studied, as well as the resulting generation of intracellular reactive oxygen species (ROS). Cell toxicity profiles of SPIONs correlated strongly with their cellular uptake kinetics, which was strongly dependent on surface properties of the particles. PEGylation caused a decrease in both uptake and cytotoxicity compared to aminated SPIONs. Interestingly, 2k Da PEG-modifed SPIONs displayed the lowest cellular uptake and cytotoxicity among all studied particles. These results emphasize the importance of surface coatings when engineering nanoparticles for biomedical applications.

Cell-penetrating peptides: achievements and challenges in application for cancer treatment.

One of the major hurdles to cure cancer lies in the low potency of currently available drugs, which could eventually be solved by using more potent therapeutic macromolecules, such as proteins or genes. However, although these macromolecules possess greater potency inside the cancer cells, the barely permeable cell membrane remains a formidable barrier to exert their efficacy. A widely used strategy is to use cell penetrating peptides (CPPs) to improve their intracellular uptake. Since the discovery of the first CPP, numerous CPPs have been derived from natural or synthesized products. Both in vitro and in vivo studies have demonstrated that those CPPs are highly efficient in transducing cargoes into almost all cell types. Therefore, to date, CPPs have been widely used for intracellular delivery of various cargoes, including peptides, proteins, genes, and even nanoparticles. In addition, recently, based on the successes of CPPs in cellular studies, their applications in vivo have been actively pursued. This review will focus on the advanced applications of CPP-based in vivo delivery of therapeutics (e.g., small molecule drugs, proteins, and genes). In addition, we will highlight certain updated applications of CPPs for intracellular delivery of nanoparticulate drug carriers, as well as several "smart" strategies for tumor targeted delivery of CPP-cargoes.

Long-circulating heparin-functionalized magnetic nanoparticles for potential application as a protein drug delivery platform.

Starch-coated, PEGylated, and heparin-functionalized iron oxide magnetic nanoparticles (DNPH) were successfully synthesized and characterized in detail. The PEGylation (20 kDa) process resulted in an average coating of 430 PEG molecules per nanoparticle. After that, heparin conjugation was carried out to attain the final DNPH platform with 35.4 µg of heparin/mg of Fe. Commercially acquired heparin-coated magnetic nanoparticles were also PEGylated (HP) and characterized for comparison. Protamine was selected as a model protein to demonstrate the strong binding affinity and high loading content of DNPH for therapeutically relevant cationic proteins. DNPH showed a maximum loading of 22.9 µg of protamine/mg of Fe. In the pharmacokinetic study, DNPH displayed a long-circulating half-life of 9.37 h, 37.5-fold longer than that (0.15 h) of HP. This improved plasma stability enabled extended exposure of DNPH to the tumor lesions, as was visually confirmed in a flank 9L-glioma mouse model using magnetic resonance imaging (MRI). Quantitative analysis of the Fe content in excised tumor lesions further demonstrated the superior tumor targeting ability of DNPH, with up to 31.36 µg of Fe/g of tissue (13.07% injected dose (I.D.)/g of tissue) and 7.5-fold improvement over that (4.27 µg of Fe/g of tissue; 1.78% I.D./g of tissue) of HP. Overall, this study shed light on the potential of DNPH to be used as a protein drug delivery platform.

Magnetic tumor targeting of ß-glucosidase immobilized iron oxide nanoparticles.

Directed enzyme/prodrug therapy (DEPT) has promising application for cancer therapy. However, most current DEPT strategies face shortcomings such as the loss of enzyme activity during preparation, low delivery and transduction efficiency in vivo and difficultly of monitoring. In this study, a novel magnetic directed enzyme/prodrug therapy (MDEPT) was set up by conjugating ß-glucosidase (ß-Glu) to aminated, starch-coated, iron oxide magnetic iron oxide nanoparticles (MNPs), abbreviated as ß-Glu-MNP, using glutaraldehyde as the crosslinker. This ß-Glu-MNP was then characterized in detail by size distribution, zeta potential, FTIR spectra, TEM, SQUID and magnetophoretic mobility analysis. Compared to free enzyme, the conjugated ß-Glu on MNPs retained 85.54% ± 6.9% relative activity and showed much better temperature stability. The animal study results showed that ß-Glu-MNP displays preferable pharmacokinetics characteristics in relation to MNPs. With an adscititious magnetic field on the surface of a tumor, a significant quantity of ß-Glu-MNP was selectively delivered into a subcutaneous tumor of a glioma-bearing mouse. Remarkably, the enzyme activity of the delivered ß-Glu in tumor lesions showed as high as 20.123±5.022 mU g(-1) tissue with 2.14 of tumor/non-tumor ß-Glu activity.

Chemically and biologically synthesized CPP-modified gelonin for enhanced anti-tumor activity.

The ineffectiveness of small molecule drugs against cancer has generated significant interest in more potent macromolecular agents. Gelonin, a plant-derived toxin that inhibits protein translation, has attracted much attention in this regard. Due to its inability to internalize into cells, however, gelonin exerts only limited tumoricidal effect. To overcome this cell membrane barrier, we modified gelonin, via both chemical conjugation and genetic recombination methods, with low molecular weight protamine (LMWP), a cell-penetrating peptide (CPP) which was shown to efficiently ferry various cargoes into cells. Results confirmed that gelonin-LMWP chemical conjugate (cG-L) and recombinant gelonin-LMWP chimera (rG-L) possessed N-glycosidase activity equivalent to that of unmodified recombinant gelonin (rGel); however, unlike rGel, both gelonin-LMWPs were able to internalize into cells. Cytotoxicity studies further demonstrated that cG-L and rG-L exhibited significantly improved tumoricidal effects, with IC50 values being 120-fold lower than that of rGel. Moreover, when tested against a CT26 s.c. xenograft tumor mouse model, significant inhibition of tumor growth was observed with rG-L doses as low as 2 µg/tumor, while no detectable therapeutic effects were seen with rGel at 10-fold higher doses. Overall, this study demonstrated the potential of utilizing CPP-modified gelonin as a highly potent anticancer drug to overcome limitations of current chemotherapeutic agents.

Pulsed magnetic field improves the transport of iron oxide nanoparticles through cell barriers.

Understanding how a magnetic field affects the interaction of magnetic nanoparticles (MNPs) with cells is fundamental to any potential downstream applications of MNPs as gene and drug delivery vehicles. Here, we present a quantitative analysis of how a pulsed magnetic field influences the manner in which MNPs interact with and penetrate across a cell monolayer. Relative to a constant magnetic field, the rate of MNP uptake and transport across cell monolayers was enhanced by a pulsed magnetic field. MNP transport across cells was significantly inhibited at low temperature under both constant and pulsed magnetic field conditions, consistent with an active mechanism (i.e., endocytosis) mediating MNP transport. Microscopic observations and biochemical analysis indicated that, in a constant magnetic field, transport of MNPs across the cells was inhibited due to the formation of large (>2 µm) magnetically induced MNP aggregates, which exceeded the size of endocytic vesicles. Thus, a pulsed magnetic field enhances the cellular uptake and transport of MNPs across cell barriers relative to a constant magnetic field by promoting accumulation while minimizing magnetically induced MNP aggregation at the cell surface.

Magnetic nanoparticles for MRI of brain tumors.

Despite advances in surgery and drug discovery, brain tumors remain fatal diseases. Early detection and diagnosis of brain tumors is of great importance for improving treatment outcomes. Magnetic resonance imaging (MRI) is a prominent, clinically-relevant imaging modality because of its excellent tissue contrast resolution, direct multiplanar imaging and increased sensitivity to edema. MRI utility is further enhanced with the use of magnetic iron oxide nanoparticles, which can function as both a contrast agent for imaging and as a drug delivery vehicle for treating brain cancer. In this review, the principles of various imaging modalities for brain tumors are discussed with focus on monocrystalline iron oxide nanoparticle (MION)-based MRI contrast agents. A summary is given on the mechanism of contrast effect, magnetophoretic mobility and magnetic retention, and strategies to enhance tumor selectivity, increase spatial resolution and reduce nonspecific uptake of MION.

In vivo delivery of cell-permeable antisense hypoxia-inducible factor 1α oligonucleotide to adipose tissue reduces adiposity in obese mice.

Ongoing research has gradually recognized and understood the importance of adipose tissue (AT) angiogenesis as a key modulating factor of adipogenesis in the development of obesity. Previously, we carried out the first in vitro demonstration of the down-regulation of hypoxic angiogenesis during adipogenesis using cell-permeable chemical conjugates composed of antisense hypoxia-inducible factor 1α (HIF1α) oligonucleotide (ASO) and low-molecular weight protamine (LMWP). To further confirm the in vivo feasibility, we administered ASO-LMWP conjugates (AL) to diet-induced obese (DIO) mice by intraperitoneal injection (IP). Results showed that the AL conjugates significantly reduced the body weight, total fat tissue weight, and plasma lipid concentrations in the mice. Moreover, the AL conjugates not only decreased liver weight and hepatic triglyceride concentration but also significantly attenuated subcutaneous adipocyte cell size, which was conversely increased in the AL-untreated high-fat diet (HFD) group. Interestingly, more blood vessels were observed in the HFD group than in the lean group, indicating that blood vessel development could induce growth of the fat mass. This pattern was reversed in the AL-treated groups, which displayed a decrease in blood vessel density compared to the AL-untreated HFD group. This study presents the first in vivo evidence, in an obese mouse model, of the feasibility of achieving a biological treatment modality for obesity by blocking the angiogenic transcriptional factor HIF1α, thereby limiting angiogenesis, via the use of an adipose tissue-permeable ASO-LMWP.

Brain tumor targeting of magnetic nanoparticles for potential drug delivery: effect of administration route and magnetic field topography.

Our previous studies demonstrated feasibility of magnetically-mediated retention of iron oxide nanoparticles in brain tumors after intravascular administration. The purpose of this study was to elucidate strategies for further improvement of this promising approach. In particular, we explored administration of the nanoparticles via a non-occluded carotid artery as a way to increase the passive exposure of tumor vasculature to nanoparticles for subsequent magnetic entrapment. However, aggregation of nanoparticles in the afferent vasculature interfered with tumor targeting. The magnetic setup employed in our experiments was found to generate a relatively uniform magnetic flux density over a broad range, exposing the region of the afferent vasculature to high magnetic force. To overcome this problem, the magnetic setup was modified with a 9-mm diameter cylindrical NdFeB magnet to exhibit steeper magnetic field topography. Six-fold reduction of the magnetic force at the injection site, achieved with this modification, alleviated the aggregation problem under the conditions of intact carotid blood flow. Using this setup, carotid administration was found to present 1.8-fold increase in nanoparticle accumulation in glioma compared to the intravenous route at 350mT. This increase was found to be in reasonable agreement with the theoretically estimated 1.9-fold advantage of carotid administration, R(d). The developed approach is expected to present an even greater advantage when applied to drug-loaded nanoparticles exhibiting higher values of R(d).

Magnetically-enabled and MR-monitored selective brain tumor protein delivery in rats via magnetic nanocarriers.

The delivery of bioactive proteins to tumors is associated with many difficulties that have impeded clinical translation of these promising therapeutics. Herein we present an approach, including (1) use of magnetically-responsive and MRI-visible nanoparticles as drug carriers, (2) topography-optimized intra-arterial magnetic targeting, (3) MRI-guided subject alignment within the magnetic field, and (4) surface modification of the protein drug with membrane-permeable polyethyleneimine (PEI), to prevail over the obstacles in protein delivery. Applying these methodologies, we demonstrated the delivery of a significant quantity of ß-galactosidase selectively into brain tumors of glioma-bearing rats, while limiting the exposure of normal brain regions. Clinical viability of the technologies utilized, and the ability to deliver proteins at high nanomolar-range tumor concentrations, sufficient to completely eradicate a tumor lesion with existing picomolar-potency protein toxins, renders the prospect of enabling protein-based cancer therapy extremely promising.