Rutin-coated ultrasmall manganese oxide nanoparticles for targeted magnetic resonance imaging and photothermal therapy of malignant tumors

Manganese oxide nanoparticles (MONs)-based contrast agents have attracted increasing attention for magnetic resonance imaging (MRI), attributed to their good biocompatibility and advantageous paramagnetism. However, conventional MONs have poor imaging performance due to low T1 relaxivity. Additionally, their lack of tumor-targeting theranostics capabilities and complex synthesis pathways have impeded clinical applications. Rutin (Ru) is an ideal tumor-targeted ligand that targets glucose transporters (GLUTs) overexpressed in various malignant tumors, and exhibits photothermal effects upon chelation with metal ions. Herein, a series of Ru-coated MONs (Ru/MnO2) were synthesized using a straightforward, rapid one-step process. Specifically, Ru/MnO2-5, with the smallest crystal size of approximately 4 nm, exhibits the highest T1 relaxivity (33.3 mM-1s-1 at 1.5 T, surpassing prior MONs) along with notable stability, photothermal efficacy, and tumor-targeting ability. Furthermore, Ru/MnO2-5 shows promise in MRI and photothermal therapy of H22 tumors owing to its superior GLUTs-mediated tumor-targeting capability.

Advancements in manganese complex-based MRI agents: Innovations, design strategies, and future directions

This review focuses on the advancements in manganese (Mn) complex-based magnetic resonance imaging (MRI) agents for imaging different diseases. Here we emphasize the unique redox properties of Mn to deliver innovative MRI contrast agents, including small molecules, nanoparticles (NPs), metal-organic frameworks (MOFs), and polymer hybrids. Aspects of their rational design have been discussed, including size dependence, morphology tuning, surface property enhancement, etc., while also discussing the existing challenges and potential solutions. The present work will inspire and motivate scientists to emphasize MRI-guided applications and bring clinical success in the coming years.

Design of manganese-based nanomaterials for pharmaceutical and biomedical applications

In the past few years, manganese-based nanostructures have been extensively investigated in the biomedical field particularly to design highly biocompatible theranostics, which can not only act as efficient diagnostic imaging contrast agents but also deliver the drugs to the target sites. The nanoscale size, large surface area-to-volume ratio, availability of cheap precursors, flexibility to synthesize nanostructures with reproducible properties and high yield, and easy scale up are the major reasons for the attraction towards manganese nanostructures. Along with these properties, the nontoxic nature, pH-sensitive degradation, and easy surface functionalization are additional benefits for the use of manganese nanostructures in biomedical and pharmaceutical sciences. Therefore, in this review, we discuss the recent progress made in the synthesis of manganese nanostructures, describe the attempts made to modify their surfaces to impart biocompatibility and stability in biological fluids, and critically discuss their use in magnetic resonance imaging, drug and gene delivery, hyperthermia, photothermal/photodynamic, immunotherapy, biosensing and tumor diagnosis.

Tannic acid-mediated synthesis of flower-like mesoporous MnO2 nanostructures as T1-T2 dual-modal MRI contrast agents and dual-enzyme mimetic agents

This study introduces a simple method for preparing a new generation of MnO2 nanomaterials (MNMs) using tannic acid as a template. Two shapes of MnO2 NMs, flower-like M1-MnO2 and near-spherical M2-MnO2, were prepared and compared as dual-active nanozymes and contrast agents in magnetic resonance imaging (MRI). Various parameters, including the crystallinity, morphology, magnetic saturation (Ms), surface functionality, surface area, and porosity of the MNMs were investigated. Flower-like M1-MnO2 NMs were biocompatible and exhibited pH-sensitive oxidase and peroxidase mimetic activity, more potent than near-spherical M2-MnO2. Furthermore, the signal intensity and r1 relaxivity strongly depended on the crystallinity, morphology, pore size, and specific surface area of the synthesized MNMs. Our findings suggest that flower-like M1-MnO2 NM with acceptable dual-enzyme mimetic (oxidase-like and peroxidase-like) and T1 MRI contrast activities could be employed as a promising theranostic system for future purposes.

A Nanomedicine Structure-Activity Framework for Research, Development, and Regulation of Future Cancer Therapies

Despite their clinical success in drug delivery applications, the potential of theranostic nanomedicines is hampered by mechanistic uncertainty and a lack of science-informed regulatory guidance. Both the therapeutic efficacy and the toxicity of nanoformulations are tightly controlled by the complex interplay of the nanoparticle's physicochemical properties and the individual patient/tumor biology; however, it can be difficult to correlate such information with observed outcomes. Additionally, as nanomedicine research attempts to gradually move away from large-scale animal testing, the need for computer-assisted solutions for evaluation will increase. Such models will depend on a clear understanding of structure-activity relationships. This review provides a comprehensive overview of the field of cancer nanomedicine and provides a knowledge framework and foundational interaction maps that can facilitate future research, assessments, and regulation. By forming three complementary maps profiling nanobio interactions and pathways at different levels of biological complexity, a clear picture of a nanoparticle's journey through the body and the therapeutic and adverse consequences of each potential interaction are presented.

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.

Unveiling the role of surface, size, shape and defects of iron oxide nanoparticles for theranostic applications

Iron oxide nanoparticles (IONPs) are well-known contrast agents for MRI for a wide range of sizes and shapes. Their use as theranostic agents requires a better understanding of their magnetic hyperthermia properties and also the design of a biocompatible coating ensuring their stealth and a good biodistribution to allow targeting of specific diseases. Here, biocompatible IONPs of two different shapes (spherical and octopod) were designed and tested in vitro and in vivo to evaluate their abilities as high-end theranostic agents. IONPs featured a dendron coating that was shown to provide anti-fouling properties and a small hydrodynamic size favoring an in vivo circulation of the dendronized IONPs. While dendronized nanospheres of about 22 nm size revealed good combined theranostic properties (r₂ = 303 mM s^-1, SAR = 395 W g_Fe^-1), octopods with a mean size of 18 nm displayed unprecedented characteristics to simultaneously act as MRI contrast agents and magnetic hyperthermia agents (r₂ = 405 mM s^-1, SAR = 950 W g_Fe^-1). The extensive structural and magnetic characterization of the two dendronized IONPs reveals clear shape, surface and defect effects explaining their high performance. The octopods seem to induce unusual surface effects evidenced by different characterization techniques while the nanospheres show high internal defects favoring Néel relaxation for magnetic hyperthermia. The study of octopods with different sizes showed that Néel relaxation dominates at sizes below 20 nm while the Brownian one occurs at higher sizes. In vitro experiments demonstrated that the magnetic heating capability of octopods occurs especially at low frequencies. The coupling of a small amount of glucose on dendronized octopods succeeded in internalizing them and showing an effect of MH on tumor growth. All measurements evidenced a particular signature of octopods, which is attributed to higher anisotropy, surface effects and/or magnetic field inhomogeneity induced by tips. This approach aiming at an analysis of the structure-property relationships is important to design efficient theranostic nanoparticles.

Biotinylated Mn3O4 nanocuboids for targeted delivery of gemcitabine hydrochloride to breast cancer and MRI applications

Multifunctional nanocarriers have been found as potential candidate for the targeted drug delivery and imaging applications. Herein, we have developed a biocompatible and pH-responsive manganese oxide nanocuboid system, surface modified with poly (ethylene glycol) bis(amine) and functionalized with biotin (Biotin-PEG-MNCs), for an efficient and targeted delivery of an anticancer drug (gemcitabine, GEM) to the human breast cancer cells. GEM-loaded Biotin-PEG@MNCs showed high drug loading efficiency, controlled release of GEM and excellent storage stability in the physiological buffers and different temperature conditions. GEM-loaded Biotin-PEG@MNCs showed dose- and time-dependent decrease in the viability of human breast cancer cells. Further, it exhibited significantly higher cell growth inhibition than pure GEM which suggested that Biotin-PEG@MNCs has efficiently delivered the GEM into cancerous cells. The role of biotin in the uptake was proved by the competitive binding-based cellular uptake study. A significant decrease in the amount of manganese was observed in biotin pre-treated cancer cells as compared to biotin untreated cancer cells. In MRI studies, Biotin-PEG-MNCs showed both longitudinal and transverse relaxivity about 0.091 and 7.66 mM^-1 s^-1 at 3.0 T MRI scanner, respectively. Overall, the developed Biotin-PEG-MNCs presents a significant potential in formulation development for cancer treatment via targeted drug delivery and enhanced MRI contrast imaging properties.

The Renal Clearable Magnetic Resonance Imaging Contrast Agents: State of the Art and Recent Advances

The advancements of magnetic resonance imaging contrast agents (MRCAs) are continuously driven by the critical needs for early detection and diagnosis of diseases, especially for cancer, because MRCAs improve diagnostic accuracy significantly. Although hydrophilic gadolinium (III) (Gd3+) complex-based MRCAs have achieved great success in clinical practice, the Gd3+-complexes have several inherent drawbacks including Gd3+ leakage and short blood circulation time, resulting in the potential long-term toxicity and narrow imaging time window, respectively. Nanotechnology offers the possibility for the development of nontoxic MRCAs with an enhanced sensitivity and advanced functionalities, such as magnetic resonance imaging (MRI)-guided synergistic therapy. Herein, we provide an overview of recent successes in the development of renal clearable MRCAs, especially nanodots (NDs, also known as ultrasmall nanoparticles (NPs)) by unique advantages such as high relaxivity, long blood circulation time, good biosafety, and multiple functionalities. It is hoped that this review can provide relatively comprehensive information on the construction of novel MRCAs with promising clinical translation.

Inner structure- and surface-controlled hollow MnO nanocubes for high sensitive MR imaging contrast effect

Manganese oxide (MnO) nanocubes were fabricated and their surface were modified by ligand encapsulation or ligand exchange, to render them water-soluble. And then, MnO formed the hollow structure by etching using acidic solution (phthalate buffer, pH 4.0). Depending on the ligand of the MnO surface, it increases the interaction between MnO and water molecules. Also, the hollow structure of MnO, as well as the ligand, can greatly enhance the accessibility of water molecules to metal ions by surface area-to-volume ratio. These factors provide high R1 relaxation, leading to strong T1 MRI signal. We have confirmed T1-weighted MR contrast effect using 4-kinds of MnO nanocubes (MnOEn, MnOEnHo, MnOEx and MnOExHo). They showed enough a MR contrast effect and biocompatibility. Especially, among them, MnOExHo exhibited high T1 relaxivity (r1) (6.02 mM^-1 s^-1), even about 1.5 times higher sensitivity than commercial T1 MR contrast agents. In vitro/in vivo studies have shown that MnOExHo provides highly sensitive T1-weighted MR imaging, thereby improving diagnostic visibility at the disease site.

Iron Oxide Nanoparticles: An Alternative for Positive Contrast in Magnetic Resonance Imaging

Iron oxide nanoparticles have been extensively utilised as negative (T2) contrast agents in magnetic resonance imaging. In the past few years, researchers have also exploited their application as positive (T1) contrast agents to overcome the limitation of traditional Gd3+ contrast agents. To provide T1 contrast, these particles must present certain physicochemical properties with control over the size, morphology and surface of the particles. In this review, we summarise the reported T1 iron oxide nanoparticles and critically revise their properties, synthetic protocols and application, not only in MRI but also in multimodal imaging. In addition, we briefly summarise the most important nanoparticulate Gd and Mn agents to evaluate whether T1 iron oxide nanoparticles can reach Gd/Mn contrast capabilities.

A Review on Cancer Therapy Based on the Photothermal Effect of Gold Nanorod

Background:

Cancer causes millions of deaths and huge economic losses every year. The currently practiced methods for cancer therapy have many defects, such as side effects, low curate rate, and discomfort for patients.

Objective:

Herein, we summarize the applications of gold nanorods (AuNRs) in cancer therapy based on their photothermal effect-the conversion of light into local heat under irradiation.

Methods:

The recent advances in the synthesis and regulation of AuNRs, and facile surface functionalization further facilitate their use in cancer treatment. For cancer therapy, AuNRs need to be modified or coated with biocompatible molecules (e.g. polyethylene glycol) and materials (e.g. silicon) to reduce the cytotoxicity and increase their biocompatibility, stability, and retention time in the bloodstream. The accumulation of AuNRs in cancerous cells and tissues is due to the high leakage in tumors or the specific interaction between the cell surface and functional molecules on AuNRs such as antibodies, aptamers, and receptors.

Results:

AuNRs are employed not only as therapeutics to ablate tumors solely based on the heat produced under laser that could denature protein and activate the apoptotic pathway, but also as synergistic therapies combined with photodynamic therapy, chemotherapy, and gene therapy to kill cancer more efficiently. More importantly, other materials like TiO2, graphene oxide, and silicon, etc. are incorporated on the AuNR surface for multimodal cancer treatment with high drug loadings and improved cancer-killing efficiency. To highlight their applications in cancer treatment, examples of therapeutic effects both in vitro and in vivo are presented.

Conclusion:

AuNRs have potential applications for clinical cancer therapy.

Renal-clearable zwitterionic conjugated hollow ultrasmall Fe3O4 nanoparticles for T1-weighted MR imaging in vivo

Monodispersed hollow Fe₃O₄ nanoparticles with the diameters of 7 and 10 nm were prepared via a high-temperature pyrolysis method and the Kirkendall effect by regulating the ratio of oleylamine to oleic acid.

Dendron based antifouling, MRI and magnetic hyperthermia properties of different shaped iron oxide nanoparticles

Owing to the great potential of iron oxide nanoparticles (NPs) for nanomedicine, large efforts have been made to better control their magnetic properties, especially their magnetic anisotropy to provide NPs able to combine imaging by MRI and therapy by magnetic hyperthermia. In that context, the design of anisotropic NPs appears as a very promising and efficient strategy. Furthermore, their bioactive coating also remains a challenge as it should provide colloidal stability, biocompatibility, furtivity along with good water diffusion for MRI. By taking advantage of our controlled synthesis method of iron oxide NPs with different shapes (cubic, spherical, octopod and nanoplate), we demonstrate here that the dendron coating, shown previously to be very suitable for 10 nm sized iron oxide, also provided very good colloidal, MRI and antifouling properties to the anisotropic shaped NPs. These antifouling properties, demonstrated through several experiments and characterizations, are very promising to achieve specific targeting of disease tissues without affecting healthy organs. On the other hand, the magnetic hyperthermia properties were shown to depend on the saturation magnetization and the ability of NPs to self-align, confirming the need of a balance between crystalline and dipolar magnetic anisotropies.

Bifunctional Pyrrolidin-2-one Terminated Manganese Oxide Nanoparticles for Combined Magnetic Resonance and Fluorescence Imaging

Multimodal probes are an asset for simplified, improved medical imaging. In particular, fluorescence and magnetic resonance imaging (MRI) are sought-after combined capabilities. Here, we show that pyrrolidin-2-one-capped manganese oxide nanoparticles (MnO^pyrr NPs) combine MRI with fluorescence microscopy to function as efficient bifunctional bio-nanoprobes. We employ a one-pot synthesis for ca. 10 nm MnO NPs, wherein manganese(II) 2,4-pentadionate is thermally decomposed using pyrrolidin-2-one as a solvent and capping ligand. The MnO^pyrr NPs are soluble in water without any further postsynthetic modifications. The r₁ relaxivity and r₂ /r₁ ratio indicate that these NPs are potential T₁ MRI contrast agents at clinical (3 T) and ultrahigh (9.4 T) magnetic fields. Serendipitously, the as-prepared NPs are photoluminescent. The unexpected luminescence is ascribed to the modification of the pyrrolidin-2-one during the thermal treatment. MnO^pyrr NPs are successfully used to enable fluorescence microscopy of HeLa cells, demonstrating bifunctional imaging capabilities. A low cytotoxic response in two distinct cell types (HeLa, HepG2) supports the suitability of MnO^pyrr NPs for biological imaging applications.

Polydopamine-coated magnetic mesoporous silica nanoparticles for multimodal cancer theranostics

Polydopamine-coated mesoporous silica nanoparticles loaded with ultrasmall Fe₃O₄ nanoparticles can be prepared for multimodal imaging and combination therapy of tumors.

Effective pH-Activated Theranostic Platform for Synchronous Magnetic Resonance Imaging Diagnosis and Chemotherapy

Current magnetic resonance imaging (MRI)-guided pH-switching therapeutic platforms have encountered problems such as low relaxation rates, poor pH-switching efficiencies, and a lag in the drug release behind the MRI. Herein, we designed a nanoplatform with tunable pore size, which could match the size of drug molecules for pH-switching MRI and chemotherapy via ultrasmall manganese oxide-capped mesoporous silica nanoparticles (USMO@MSNs). USMO@MSN could quickly dissolve under weakly acidic conditions and leach abundant Mn²⁺ ions (leaching ratio: 76%), enhancing the MR contrast. The longitudinal relaxation rate ( r₁) of USMO@MSNs significantly increased from 0.65 to 5.61 mM^-1 s^-1 as the pH decreased from 7.4 to 4.5, showing an ultrahigh-efficiency pH-switching T₁-weighted MR contrast ability for in vivo tumor. Meanwhile, the matching pore structure allowed effective loading of doxorubicin (DOX) on USMO@MSNs to form smart therapeutic system (USMO@MSNs-DOX). The DOX release rate was strongly proportional to the pH-switching MRI signal of USMO@MSNs-DOX, allowing the release of DOX to be efficiently monitored by MRI. Confocal observations indicated that USMO@MSNs-DOX could be effectively internalized by HSC3 cells, and the entire system showed a good pH-switching theranostic performance for HSC3 cells. Therefore, this simple pH-switching system provides a new avenue for timely cancer diagnosis and personalized therapy.

Surface engineering of SPIONs: role of phosphonate ligand multivalency in tailoring their efficacy

We report the design of scaffolds containing mono-, bis-, and tris-phosphonate coordinating groups, and a polyethylene glycol chain, for stabilizing superparamagnetic iron oxide nanoparticles (SPIONs), using simple and versatile chemistry. We demonstrate that the number of anchoring phosphonate sites on the ligand influence the colloidal stability, magnetic and biological properties of SPIONs, and the latter do not solely depend on attaching moieties that can enhance their aqueous dispersion. These parameters can be tailored by the number of conjugation sites on the ligand, as evidenced from dynamic light scattering at various salt concentrations, magnetic relaxivities and cell viability studies.

Relaxivity and toxicological properties of manganese oxide nanoparticles for MRI applications

Manganese oxide nanoparticles (MONs) have received growing attention as alternative T ₁ MRI contrast agents due to the association of commercial gadolinium-based contrast agents with nephrogenic systemic fibrosis. Since the seminal publication first describing the use of MONs as positive T ₁ contrast agents, there is an ongoing impetus to develop MONs of higher T ₁ signal intensity for better diagnostic efficacy. Indeed, various MON-based nanoprobe designs have been proposed, such as the employment of a mesoporous nanomaterial with MONs evenly dispersed within, or the traditional coating of a biocompatible layer onto the surface of MONs to form a core-shell configuration. Recent advances in this field also propose stimuli-responsive MONs that capitalize on an acidic dissolution or in situ reduction to release Mn²⁺ ions for a multi-fold increase in MRI contrast. However, the potential nanotoxicity of MONs remains a key obstacle to the clinical translation of MON-based T ₁ contrast agents. Due to the wide variety of functionalities and physicochemical properties of MONs, there is also a lack of consensus on the toxicological properties of MONs. In addition, the r ₁ relaxivity of MRI contrast agents typically decreases at higher field strength. Hence, it highlights the need to develop MON-based contrast agents with higher relaxivities. In this regard, this article aims to present a thorough review of MONs for MRI applications, with particular emphasis on their relaxivity and toxicological properties. In order to systematically review the current state-of-the-art for the development of MONs for MRI applications, the MON-based T ₁ contrast agents are categorized based on the structure of the nanomaterial system. Key parameters that influence the nanotoxicity of MONs are also examined while the absorption, distribution, metabolism and excretion of MON in vivo are evaluated to discern how long the nanoparticles will be present within the body, as well as to predict the organs or tissues in which they distribute.

Nanoparticle-liver interactions: Cellular uptake and hepatobiliary elimination

30-99% of administered nanoparticles will accumulate and sequester in the liver after administration into the body. This results in reduced delivery to the targeted diseased tissue and potentially leads to increased toxicity at the hepatic cellular level. This review article focuses on the inter- and intra-cellular interaction between nanoparticles and hepatic cells, the elimination mechanism of nanoparticles through the hepatobiliary system, and current strategies to manipulate liver sequestration. The ability to solve the "nanoparticle-liver" interaction is critical to the clinical translation of nanotechnology for diagnosing and treating cancer, diabetes, cardiovascular disorders, and other diseases.

Assembly of near infra-red emitting upconverting nanoparticles and multiple Gd(III)-chelates as a potential bimodal contrast agent for MRI and optical imaging

Linking multiple paramagnetic gadolinium(III)-chelates based on the 2-[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl]acetate (DOTA) ligand to the surface of NaGdF4:Yb(3+),Tm(3+) upconverting nanoparticles with an average particle size of 20 nm resulted in an assembly that has favorable properties for bimodal Magnetic Resonance Imaging (MRI) and Optical Imaging (OI). An improved synthetic pathway was used to couple the paramagnetic precursor to the nanoparticles. The nanoparticles were rendered water dispersible via citrate capping, leaving one acid group free for amide coupling with the mono-amino precursor of the DOTA ligand. Luminescence spectroscopy measurements have shown that the excitation of the nanoconstruct at 980 nm resulted in intense upconverted emission of thulium(III) at 800 nm. The assembly of several paramagnetic centers on the nanoparticle scaffold reduces the overall tumbling rate, resulting in enhanced longitudinal relaxation times and improved relaxivity. The proton NMRD profiles show a characteristic hump at higher frequencies, which is caused by the slow rotation of the nanoconstruct, resulting in r1 values of 25 mM(-1) s(-1) per gadolinium(III)-ion at 60 MHz and 310 K. This is a significant improvement compared to the Gd-DO3A-ethylamine precursor (4) for which a value of r1 of 3.23 mM(-1) s(-1) was observed under the same conditions. Theoretical fitting by two different approaches showed an increase of τR from 57.3 ps for the Gd-DO3A-ethylamine precursor (4) to 392.0 ps for the nanoconstruct, which is responsible for the overall substantial increase in relaxivity.

Dendrimer–nanoparticle conjugates in nanomedicine

Nanomedicine can take advantage of the recent developments in nanobiotechnology research areas for the creation of platforms with superior drug carrier capabilities, selective responsiveness to the environment, unique contrast enhancement profiles and improved accumulation at the disease site. Colloidal inorganic nanoparticles (NPs) have been attracting considerable interest in biomedicine, from drug and gene delivery to imaging, sensing and diagnostics. It is essential to modify the NPs surface to have enhanced biocompatibility and reach multifunctional systems for the in vitro and in vivo applications, especially in delivering drugs locally and recognizing overexpressed biomolecules. This paper describes the rational design for dendrimer–nanoparticle conjugates elaboration and reviews their state-of-the-art uses as efficient nanomedicine tools.

Validation of a dendron concept to tune colloidal stability, MRI relaxivity and bioelimination of functional nanoparticles

A dendritic coating induces colloidal stability of nanoparticles through electrostatic and steric interactions.