Gadolinium‐based chelates are a mainstay of contrast agents for magnetic resonance imaging (MRI) in the clinic. However, their toxicity elicits severe side effects and the Food and Drug Administration has issued many warnings about their potential retention in patients’ bodies, which causes safety concerns. Iron oxide nanoparticles (IONPs) are a potentially attractive alternative, because of their nontoxic and biodegradable nature. Studies in developing IONPs as T1 contrast agents have generated promising results, but the complex, interrelated parameters influencing contrast enhancement make the development difficult, and IONPs suitable for T1 contrast enhancement have yet to make their way to clinical use. Here, the fundamental principles of MRI contrast agents are discussed, and the current status of MRI contrast agents is reviewed with a focus on the advantages and limitations of current T1 contrast agents and the potential of IONPs to serve as safe and improved alternative to gadolinium‐based chelates. The past advances and current challenges in developing IONPs as a T1 contrast agent from a materials science perspective are presented, and how each of the key material properties and environment variables affects the performance of IONPs is assessed. Finally, some potential approaches to develop high‐performance and clinically relevant T1 contrast agents are discussed.

Human tumor necrosis factor α-related apoptosis-inducing ligand (TRAIL) is an attractive cancer therapeutic because of its ability to induce apoptosis in tumor cells while having a negligible effect on normal cells. However, the short serum half-life of TRAIL and lack of efficient in vivo administration approaches have largely hindered its clinical use. Using nanoparticles (NPs) as carriers in gene therapy is considered as an alternative approach to increase TRAIL delivery to tumors as transfected cells would be induced to secrete TRAIL into the tumor microenvironment. To enable effective delivery of plasmid DNA encoding TRAIL into glioblastoma (GBM), we develop a targeted iron oxide NP coated with chitosan-polyethylene glycol-polyethyleneimine copolymer and chlorotoxin (CTX), and evaluate its effect in delivering TRAIL in vitro and in vivo. NP-TRAIL successfully delivers TRAIL into human T98G GBM cells and induces secretion of 40 pg/ml of TRAIL in vitro. Transfected cells show 3-fold increased apoptosis as compared to the control DNA bound NPs. Systemic administration of NP-TRAIL-CTX to mice bearing T98G derived flank xenografts results in near zero tumor growth, and induces apoptosis in tumor tissue. Our results suggest that NP-TRAIL-CTX could potentially serve as a targeted anticancer therapeutic for more efficient TRAIL delivery to GBM.

Surface functionalization of theranostic nanoparticles (NPs) typically relies on lengthy, aqueous post-synthesis labeling chemistries that have limited ability to fine tune surface properties and can lead to NP heterogeneity. The need for a rapid, simple synthesis approach that can provide great control over the display of functional moieties on NP surfaces has led to increased use of highly selective bioorthoganol chemistries including metal-affinity coordination. Here we report a simple approach for rapid production of a superparamagnetic iron oxide NPs (SPIONs) with tunable functionality and high reproducibility under aqueous conditions. We utilize the high affinity complex formed between catechol and Fe(III) as a means to dock well-defined catechol modified polymer modules on the surface of SPIONs during sonochemical co-precipitation synthesis. Polymer modules consisted of chitosan and poly(ethylene glycol) (PEG) copolymer (CP) modified with catechol (CCP), and CCP functionalized with cationic polyethylenimine (CCP-PEI) to facilitate binding and delivery of DNA for gene therapy. This rapid synthesis/functionalization approach provided excellent control over the extent of PEI labeling, improved SPION magnetic resonance imaging (MRI) contrast enhancement and produced an efficient transfection agent.

Hepatocellular carcinoma (HCC) is one of the deadliest cancers worldwide. Small interfering RNA (siRNA) holds promise as a new class of therapeutics for HCC as it can achieve sequence-specific gene knockdown with low cytotoxicity. However, the main challenge in the clinical application of siRNA lies in the lack of effective delivery approaches that need to be highly specific and thus incur low or no systemic toxicity. Here, we present a non-viral nanoparticle-based gene carrier that can specifically deliver siRNA to HCC. The nanovector (NP-siRNA-GPC3 Ab) is made of an iron oxide core coated with chitosan-PEG grafted PEI copolymer, which is further functionalized with siRNA and conjugated with a monoclonal antibody (Ab) against human glypican-3 (GPC3) receptor highly expressed in HCC. A rat RH7777 HCC cell line that co-expresses human GPC3 and firefly luciferase (Luc) is established to evaluate the nanovector. The nanoparticle-mediated delivery of siRNA against Luc effectively suppresses Luc expression in vitro without notable cytotoxicity. Significantly, NP-siLuc-GPC3 Ab administered intravenously in an orthotopic model of HCC is able to specifically bound to tumor and induce remarkable inhibition of Luc expression. Our findings demonstrate the potential of using this nanovector for targeted delivery of therapeutic siRNA to HCC.

Nanoparticles (NPs) for targeted therapy are required to have appropriate size, stability, drug loading and release profiles, and efficient targeting ligands. However, many of existing NPs such as albumin, liposomes, polymers, gold NPs, etc. encounter size limit, toxicity and stability issues when loaded with drugs, fluorophores, and targeting ligands. Furthermore, antibodies are bulky and can greatly affect the physicochemical properties of the NPs, whereas many small molecule-based targeting ligands lack specificity. Here, we report utilization of biocompatible, biodegradable, small (~30 nm) and stable iron oxide NPs (IONPs) for targeted delivery of paclitaxel (PTX) to HER2/neu positive breast cancer using an anti-HER2/neu peptide (AHNP) targeting ligand. We demonstrate the uniform size and high stability of these NPs in biological medium, effective tumour targeting in live mice, as well as their efficient cellular targeting and selective killing in human HER2/neu-positive breast cancer cells.

Applications of hydrophobic drug-based nanocarriers (NCs) remain largely limited because of their low loading capacity. Here, we report development of a multifunctional hybrid NC made of a magnetic Fe3O4 nanoparticle core and a mesoporous silica shell embedded with fluorescent carbon dots (CDs) and paclitaxel (PTX), and covered by another layer of silica. The NC is prepared via a one-pot process under mild condition. The PTX loading method introduced in this study simplifies drug loading process and demonstrates a high loading capacity as a result of the mesoporous silica dual-shell structure, supramolecular π-stacking between the conjugated rings of PTX molecules and aromatic rings of the CDs in the hybrid NC. The CDs also serve as both confocal and two-photon fluorescence imaging probes, while the Fe3O4 core serves as an MRI contrast agent. Significantly, NC releases PTX in response to NIR irradiation as a result of local heating of the embedded CDs and the heating of CDs also provides an additional therapeutic effect by thermally killing cancer cells in tumor in addition to the chemotherapeutic effect of released PTX. Both in vitro and in vivo results show that NC demonstrates high therapeutic efficacy through a synergistic effect from the combined chemo-photothermal treatments.

Despite the preponderance of iron oxide nanoparticles (NPs) designed for theranostic applications, widespread clinical translation of these NPs lags behind. A better understanding of how NP pharmacokinetics vary between small and large animal models is needed to rapidly customize NPs for optimal performance in humans. Here we use noninvasive magnetic resonance imaging (MRI) to track iron oxide NPs through a large number of organ systems in vivo to investigate NP biokinetics in both mice and nonhuman primates. We demonstrate that pharmacokinetics are similar between mice and macaques in the blood, liver, spleen, and muscle, but differ in the kidneys, brain, and bone marrow. Our study also demonstrates that full-body MRI is practical, rapid and cost-effective for tracking NPs non-invasively with high spatiotemporal resolution. Our techniques using a nonhuman primate model may provide a platform for testing a range of NP formulations.

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