Development of an Effective Tumor-Targeted Contrast Agent for Magnetic Resonance Imaging Based on Mn/H-Ferritin Nanocomplexes.

Magnetic resonance imaging (MRI) is one of the most sophisticated diagnostic tools that is routinely used in clinical practice. Contrast agents (CAs) are commonly exploited to afford much clearer images of detectable organs and to reduce the risk of misdiagnosis caused by limited MRI sensitivity. Currently, only a few gadolinium-based CAs are approved for clinical use. Concerns about their toxicity remain, and their administration is approved only under strict controls. Here, we report the synthesis and validation of a manganese-based CA, namely, Mn@HFn-RT. Manganese is an endogenous paramagnetic metal able to produce a positive contrast like gadolinium, but it is thought to result in less toxicity for the human body. Mn ions were efficiently loaded inside the shell of a recombinant H-ferritin (HFn), which is selectively recognized by the majority of human cancer cells through their transferrin receptor 1. Mn@HFn-RT was characterized, showing excellent colloidal stability, superior relaxivity, and a good safety profile. In vitro experiments confirmed the ability of Mn@HFn-RT to efficiently and selectively target breast cancer cells. In vivo, Mn@HFn-RT allowed the direct detection of tumors by positive contrast enhancement in a breast cancer murine model, using very low metal dosages and exhibiting rapid clearance after diagnosis. Hence, Mn@HFn-RT is proposed as a promising CA candidate to be developed for MRI.

Evaluation of TFR-1 Expression in Feline Mammary Cancer and In Vitro Antitumor Efficacy Study of Doxorubicin-Loaded H-Ferritin Nanocages.

The transferrin receptor 1 (TFR-1) has been found overexpressed in a broad range of solid tumors in humans and is, therefore, attracting great interest in clinical oncology for innovative targeted therapies, including nanomedicine. TFR-1 is recognized by H-Ferritin (HFn) and has been exploited to allow selective binding and drug internalization, applying an HFn nanocage loaded with doxorubicin (HFn(DOX)). In veterinary medicine, the role of TFR-1 in animal cancers remains poorly explored, and no attempts to use TFR-1 as a target for drug delivery have been conducted so far. In this study, we determined the TFR-1 expression both in feline mammary carcinomas during tumor progression, as compared to healthy tissue, and, in vitro, in a feline metastatic mammary cancer cell line. The efficacy of HFn(DOX) was compared to treatment with conventional doxorubicin in feline mammary cancer cells. Our results highlighted an increased TFR-1 expression associated with tumor metastatic progression, indicating a more aggressive behavior. Furthermore, it was demonstrated that the use of HFn(DOX) resulted in less proliferation of cells and increased apoptosis when compared to the drug alone. The results of this preliminary study suggest that the use of engineered bionanocages also offers unprecedented opportunities for selective targeted chemotherapy of solid tumors in veterinary medicine.

Engineered Ferritin Nanoparticles for the Bioluminescence Tracking of Nanodrug Delivery in Cancer.

The identification of a highly sensitive method to check the delivery of administered nanodrugs into the tumor cells is a crucial step of preclinical studies aimed to develop new nanoformulated cures, since it allows the real therapeutic potential of these devices to be forecast. In the present work, the ability of an H-ferritin (HFn) nanocage, already investigated as a powerful tool for cancer therapy thanks to its ability to actively interact with the transferrin receptor 1, to act as an efficient probe for the monitoring of nanodrug delivery to tumors is demonstrated. The final formulation is a bioluminescent nanoparticle, where the luciferin probe is conjugated on nanoparticle surface by means of a disulfide containing linker (Luc-linker@HFn) which is subjected to glutathione-induced cyclization in tumor cell cytoplasm. The prolonged imaging of luciferase+ tumor models, demonstrated by an in vitro and an in vivo approach, associated with the prolonged release of luciferin into cancer cells by disulfide bridge reduction, clearly indicates the high efficiency of Luc-linker@HFn for drug delivery to the tumor tissues.

Impact of the strategy adopted for drug loading in nonporous silica nanoparticles on the drug release and cytotoxic activity.

Nanoparticles are normally classified as "hard", mainly consisting of metal or metal oxide cores, or "soft", including polymer-based, liposomes and biomimetic nanoparticles. Soft nanoparticles have been studied in depth for drug formulation and therapeutic delivery applications, albeit hard nanoparticles may offer easier synthesis, smaller size and more effective tumor penetration. Among them, silica nanoparticles maintain excellent biocompatibility and biodegradability and can be finely adjusted in size and shape, easily produced in a large scale and functionalized or loaded with active molecules. To help filling the gap of a poor clinical translation of hard nanoparticles, we have designed and developed three different nonporous silica nanocarriers loading the chemotherapeutic doxorubicin within the core matrix, on the surface or both inside and outside, respectively. A comparative study was performed on drug loading and drug release, silica matrix degradation and nanodrug cytotoxic activity, highlighting unexpected correlation between the strategy adopted for drug incorporation and nanoparticle behavior in a physiological environment. This study offers a new insight on the impact of the choice of the prodrug nanoparticles on the kinetics and efficacy of drug delivery, which may encourage the scientific community in developing a new generation of drug delivery systems based on hard nanocarriers.

H-Ferritin Enriches the Curcumin Uptake and Improves the Therapeutic Efficacy in Triple Negative Breast Cancer Cells.

Triple negative breast cancer (TNBC) is a highly aggressive, invasive, and metastatic tumor. Although it is reported to be sensitive to cytotoxic chemotherapeutics, frequent relapse and chemoresistance often result in treatment failure. In this study, we developed a biomimetic nanodrug consisting of a self-assembling variant (HFn) of human apoferritin loaded with curcumin. HFn nanocage improved the solubility, chemical stability, and bioavailability of curcumin, allowing us to reliably carry out several experiments in the attempt to establish the potential of this molecule as a therapeutic agent and elucidate the mechanism of action in TNBC. HFn biopolymer was designed to bind selectively to the TfR1 receptor overexpressed in TNBC cells. HFn-curcumin (CFn) proved to be more effective in viability assays compared to the drug alone using MDA-MB-468 and MDA-MB-231 cell lines, representative of basal and claudin-low TNBC subtypes, respectively. Cellular uptake of CFn was demonstrated by flow cytometry and label-free confocal Raman imaging. CFn could act as a chemosensitizer enhancing the cytotoxic effect of doxorubicin by interfering with the activity of multidrug resistance transporters. In addition, CFn exhibited different cell cycle effects on these two TNBC cell lines, blocking MDA-MB-231 in G0/G1 phase, whereas MDA-MB-468 accumulated in G2/M phase. CFn was able to inhibit the Akt phosphorylation, suggesting that the effect on the proliferation and cell cycle involved the alteration of PI3K/Akt pathway.

Nanometronomic treatment of 4T1 breast cancer with nanocaged doxorubicin prevents drug resistance and circumvents cardiotoxicity.

Chemotherapeutic treatment of breast cancer is based on maximum tolerated dose (MTD) approach. However, advanced stage tumors are not effectively eradicated by MTD owing to suboptimal drug targeting, onset of therapeutic resistance and neoangiogenesis. In contrast, "metronomic" chemotherapy is based on frequent drug administrations at lower doses, resulting in neovascularization inhibition and induction of tumor dormancy. Here we show the potential of H-ferritin (HFn)-mediated targeted nanodelivery of metronomic doxorubicin (DOX) in the setting of a highly aggressive and metastatic 4T1 breast cancer mouse model with DOX-inducible expression of chemoresistance. We find that HFn-DOX administered at repeated doses of 1.24 mg kg-1 strongly improves the antitumor potential of DOX chemotherapy arresting the tumor progression. We find that such a potent antitumor effect is attributable to multiple nanodrug actions beyond cell killing, including inhibition of tumor angiogenesis and avoidance of chemoresistance. Multiparametric assessment of heart tissues, including histology, ultrastructural analysis of tissue morphology, and measurement of markers of reactive oxygen species and hepatic/renal conditions, provided evidence that metronomic HFn-DOX allowed us to overcome cardiotoxicity. Our results suggest that HFn-DOX has tremendous potential for the development of "nanometronomic" chemotherapy toward safe and tailored oncological treatments.

"Blind" targeting in action: From phage display to breast cancer cell targeting with peptide-gold nanoconjugates.

Tumor homing peptides (THPs) specific for a representative breast cancer cell line (MCF-7) were carefully selected basing on a phage-displayed peptide library freely available on the web, namely the "TumorHoPe: A Database of Tumor Homing Peptides". The selected THPs were synthesized and evaluated in terms of their affinity toward MCF-7 cells. Out of 5 tested THPs, 3 best-performing peptide sequences and 1 scrambled sequence were separately conjugated to spherical gold nanoparticles yielding stable nanoconjugates. THP nanoconjugates were examined for their ability to actively target MCF-7 cells in comparison to noncancerous 3T3-L1 fibroblast cells. These THP-gold nanoconjugates exhibited good selectivity and binding affinity by flow cytometry, and low cytotoxicity as assayed by cell death experiments. The uptake of targeted nanoconjugates by the breast cancer cells was confirmed by transmission electron microscopy analysis. This work demonstrates that it is possible to exploit the conjugation of short peptides selected from phage-displayed libraries to develop nanomaterials reliably endowed with tumor targeting potential irrespective of a specific knowledge of the target cell biology.

Protein nanocages for self-triggered nuclear delivery of DNA-targeted chemotherapeutics in Cancer Cells.

A genetically engineered apoferritin variant consisting of 24 heavy-chain subunits (HFn) was produced to achieve a cumulative delivery of an antitumor drug, which exerts its cytotoxic action by targeting the DNA at the nucleus of human cancer cells with subcellular precision. The rationale of our approach is based on exploiting the natural arsenal of defense of cancer cells to stimulate them to recruit large amounts of HFn nanoparticles loaded with doxorubicin inside their nucleus in response to a DNA damage, which leads to a programmed cell death. After demonstrating the selectivity of HFn for representative cancer cells compared to healthy fibroblasts, doxorubicin-loaded HFn was used to treat the cancer cells. The results from confocal microscopy and DNA damage assays proved that loading of doxorubicin in HFn nanoparticles increased the nuclear delivery of the drug, thus enhancing doxorubicin efficacy. Doxorubicin-loaded HFn acts as a "Trojan Horse": HFn was internalized in cancer cells faster and more efficiently compared to free doxorubicin, then promptly translocated into the nucleus following the DNA damage caused by the partial release in the cytoplasm of encapsulated doxorubicin. This self-triggered translocation mechanism allowed the drug to be directly released in the nuclear compartment, where it exerted its toxic action. This approach was reliable and straightforward providing an antiproliferative effect with high reproducibility. The particular self-assembling nature of HFn nanocage makes it a versatile and tunable nanovector for a broad range of molecules suitable both for detection and treatment of cancer cells.

Assessing the in vivo targeting efficiency of multifunctional nanoconstructs bearing antibody-derived ligands.

A great challenge in nanodiagnostics is the identification of new strategies aimed to optimize the detection of primary breast cancer and metastases by the employment of target-specific nanodevices. At present, controversial proof has been provided on the actual importance of surface functionalization of nanoparticles to improve their in vivo localization at the tumor. In the present paper, we have designed and developed a set of multifunctional nanoprobes, modified with three different variants of a model antibody, that is, the humanized monocolonal antibody trastuzumab (TZ), able to selectively target the HER2 receptor in breast cancer cells. Assuming that nanoparticle accumulation in target cells is strictly related to their physicochemical properties, we performed a comparative study of internalization, trafficking, and metabolism in MCF7 cells of multifunctional nanoparticles (MNP) functionalized with TZ or with alternative lower molecular weight variants of the monoclonal antibody, such as the half-chain (HC) and scFv fragments (scFv). Hence, to estimate to what extent the structure of the surface bioligand affects the targeting efficiency of the nanoconjugate, three cognate nanoconstructs were designed, in which only the antibody form was differentiated while the nanoparticle core was maintained unvaried, consisting of an iron oxide spherical nanocrystal coated with an amphiphilic polymer shell. In vitro, in vivo, and ex vivo analyses of the targeting efficiency and of the intracellular fate of MNP-TZ, MNP-HC, and MNP-scFv suggested that the highly stable MNP-HC is the best candidate for application in breast cancer detection. Our results provided evidence that, in this case, active targeting plays an important role in determining the biological activity of the nanoconstruct.