Ferritin-nanocaged copper arsenite minerals with oxidative stress-amplifying activity for targeted cancer therapy.

We report copper(II) arsenite-encapsulated ferritin nanoparticles (CuAS-FNs) as oxidative stress-amplifying anticancer agents. The CuAS-FNs were fabricated through CuAS mineralization in the cavity of the FNs. The formation of crystalline CuAS complex minerals in the FNs was systematically identified using various analytical tools, including X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM)-associated energy-dispersive X-ray spectroscopy (TEM-EDS). The CuAS-FNs showed pH-dependent release behavior, in which the CuAS mineral was effectively retained at physiological pH, in contrast, at lysosomal pH, the CuAS complex was dissociated to release arsenite and Cu2+ ions. At lysosomal pH, the release rate of arsenite (HAsO32-) and Cu2+ ions from the CuAS-FNs more accelerated than at physiological pH. Upon transferrin receptor-1-mediated endocytosis, the CuAS-FNs simultaneously released arsenite and Cu2+ ions in cells. The released arsenite ions can increase the intracellular concentration of hydrogen peroxide (H2O2), with which the Cu2+ ions can elevate the level of hydroxyl radicals (·OH) via Fenton-like reaction. Thus, the CuAS-FNs could target cancer cell through the recognizing ability of FNs and kill cancer cells by amplifying the ·OH level through the synergistic activity of Cu2+ and arsenic ions. Importantly, MCF-7 tumors were effectively suppressed by CuAS-FNs without systemic in vivo toxicity. Therefore, the CuAS-FNs is a promising class of Fenton-like catalytic nanosystem for cancer treatment.

MnCO3-mineralized polydopamine nanoparticles as an activatable theranostic agent for dual-modality imaging-guided photothermal therapy of cancers.

Background: Single imaging modality is still insufficient to evaluate the biological and anatomical structures of tumors with high accuracy and reliability. Generation of non-specific contrast, leading to a low target-to-background signal ratio, results in low imaging resolution and accuracy. Tumor environment-specific activatable multifunctional contrast agents need to maximize the contrast signals, representing a dual imaging-guided photothermal therapy (PTT) at target tumor sites. Methods: Cellular uptake, cytotoxicity assay, and in vitro photothermal conversion efficiency of MnCO3-mineralized fluorescent polydopamine nanoparticles (MnCO3-FPNPs) were evaluated using 4T1 breast cancer cells. In vivo dual-modality imaging was performed using IVIS imaging and a 4.7 T animal MRI systems after injection into 4T1 tumor-bearing nude mice. The effects of photothermal therapeutic through PTT were measured after irradiation with an 808 nm laser (1.5 W/cm2) for 10 min, measuring the size of the tumors every 2 days. Results: At physiological pH (7.4), MnCO3-FPNP is efficiently quenched. Conversely, at acidic pH (5.4), the strong fluorescence (FL) is recovered due to the dissociation of Mn2+ from the FPNPs. At pH 7.4, MnCO3-FPNP activity is silenced to enhance water proton relaxation due to unionized MnCO3 maintenance; conversely, at acidic pH (5.4), MnCO3-FPNPs efficiently release Mn2+ ions, thereby resulting in T 1-weighted magnetic resonance (MR) contrast enhancement. MnCO3-FPNPs display a promising diagnostic ability for 4T1 breast cancer xenograft models, as well as exhibit a high photothermal conversion efficiency. A successful tumor treatment via their photothermal activity is accomplished within 14 days. Conclusions: Our studies exhibited unique "OFF-ON" activation abilities in FL/MR dual imaging and PTT functions. This approach suggests that the MnCO3-FPNPs may serve as a useful platform for various mineralization-based multimodal imaging-guided PTT models for many cancer theranostic applications.

Genetically Modified Ferritin Nanoparticles with Bone-Targeting Peptides for Bone Imaging.

Bone homeostasis plays a major role in supporting and protecting various organs as well as a body structure by maintaining the balance of activities of the osteoblasts and osteoclasts. Unbalanced differentiation and functions of these cells result in various skeletal diseases, such as osteoporosis, osteopetrosis, and Paget's disease. Although various synthetic nanomaterials have been developed for bone imaging and therapy through the chemical conjugation, they are associated with serious drawbacks, including heterogeneity and random orientation, in turn resulting in low efficiency. Here, we report the synthesis of bone-targeting ferritin nanoparticles for bone imaging. Ferritin, which is a globular protein composed of 24 subunits, was employed as a carrier molecule. Bone-targeting peptides that have been reported to specifically bind to osteoblast and hydroxyapatite were genetically fused to the N-terminus of the heavy subunit of human ferritin in such a way that the peptides faced outwards. Ferritin nanoparticles with fused bone-targeting peptides were also conjugated with fluorescent dyes to assess their binding ability using osteoblast imaging and a hydroxyapatite binding assay; the results showed their specific binding with osteoblasts and hydroxyapatite. Using in vivo analysis, a specific fluorescent signal from the lower limb was observed, demonstrating a highly selective affinity of the modified nanoparticles for the bone tissue. These promising results indicate a specific binding ability of the nanoscale targeting system to the bone tissue, which might potentially be used for bone disease therapy in future clinical applications.

Bone-targeting carbon dots: effect of nitrogen-doping on binding affinity.

Novel fluorescent carbon dots (CDs) for bone imaging were fabricated via a facile hydrothermal method using alendronate in the absence of a nitrogen-doping precursor to enhance bone affinity. One-step synthesized alendronate-based CDs (Alen-CDs) had strong binding activity for calcium-deficient hydroxyapatite (CDHA, the mineral component of bones) scaffold, rat femur, and bone structures of live zebrafish. This was attributed to the bisphosphonate group present on the CD surface, even after carbonization. For comparison, the surface effects of nitrogen-doped CDs obtained using ethylenediamine (EDA), i.e., Alen-EDA-CDs, were also investigated, focusing on the targeting ability of distinct surface functional groups when compared with Alen-CDs. An in vivo study to assess the impact on bone affinity revealed that Alen-CDs effectively accumulated in the bone structures of live zebrafish larvae after microinjections, as well as in the bone tissues of femur extracted from rats. Moreover, Alen-CD-treated zebrafish larvae had superior toleration, retaining skeletal fluorescence for 7 days post-injection (dpi). The sustainable capability, surpassing that of Alizarin Red S, suggests that Alen-CDs have the potential for targeted drug delivery to damaged bone tissues and provides motivation for additional in vivo investigations. To our knowledge, this is the first in vitro, ex vivo, and in vivo demonstration of direct bone-targeted deliveries, supporting the use of fluorescent CDs in the treatment of various bone diseases such as osteoporosis, Paget's disease, and metastatic bone cancer.