One-pot preparation of hydrophilic manganese oxide nanoparticles as T1 nano-contrast agent for molecular magnetic resonance imaging of renal carcinoma in vitro and in vivo

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.

Facile Synthesis of Rigid Binuclear Manganese Complexes for Magnetic Resonance Angiography and SLC39A14-Mediated Hepatic Imaging

Manganese(II)-based contrast agents (MBCAs) are potential candidates for gadolinium-free enhanced magnetic resonance imaging (MRI). In this work, a rigid binuclear MBCA (Mn2-PhDTA2) with a zero-length linker was developed via facile synthetic routes, while the other dimer (Mn2-TPA-PhDTA2) with a longer rigid linker was also synthesized via more complex steps. Although the molecular weight of Mn2-PhDTA2 is lower than that of Mn2-TPA-PhDTA2, their T1 relaxivities are similar, being increased by over 71% compared to the mononuclear Mn-PhDTA. In the presence of serum albumin, the relaxivity of Mn2-PhDTA2 was slightly lower than that of Mn2-TPA-PhDTA2, possibly due to the lower affinity constant. The transmetalation reaction with copper(II) ions confirmed that Mn2-PhDTA2 has an ideal kinetic inertness with a dissociation half-life of approximately 10.4 h under physiological conditions. In the variable-temperature 17O NMR study, both Mn-PhDTA and Mn2-PhDTA2 demonstrated a similar estimated q close to 1, indicating the formation of monohydrated complexes with each manganese(II) ion. In addition, Mn2-PhDTA2 demonstrated a superior contrast enhancement to Mn-PhDTA in in vivo vascular and hepatic MRI and can be rapidly cleared through a dual hepatic and renal excretion pattern. The hepatic uptake mechanism of Mn2-PhDTA2 mediated by SLC39A14 was validated in cellular uptake studies.

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.

Mn-Based MRI Contrast Agents: An Overview

MRI contrast agents are required in the clinic to detect some pathologies, such as cancers. Nevertheless, at the moment, only small extracellular and non-specific gadolinium complexes are available for clinicians. Moreover, safety issues have recently emerged concerning the use of gadolinium complexes; hence, alternatives are urgently needed. Manganese-based MRI contrast agents could be one of these alternatives and increasing numbers of studies are available in the literature. This review aims at synthesizing all the research, from small Mn complexes to nanoparticular agents, including theranostic agents, to highlight all the efforts already made by the scientific community to obtain highly efficient agents but also evidence of the weaknesses of the developed systems.

Anti-nucleolin aptamer AS1411: an advancing therapeutic

Targeted therapy is highly desirable, as it allows for selective cytotoxicity on diseased cells without off-target side effects. Nucleolin is a remarkable target for cancer therapy given its high abundance, selective presence on the plasma membrane, and multifaceted influence on the initiation and progression of cancer. Nucleolin is a protein overexpressed on the cell membrane in many tumors and serves as a binding protein for several ligands implicated in angiogenesis and tumorigenesis. Nucleolin is present in the cytoplasm, nucleoplasm, and nucleolus and is used by selected pathogens for cell entry. AS1411 is a guanosine-rich oligonucleotide aptamer that binds nucleolin and is internalized in the tumor cells. AS1411 is well tolerated at therapeutic doses and localizes to tumor cells overexpressing nucleolin. AS1411 has a good safety profile with efficacy in relapsed acute myeloid leukemia and renal cell carcinoma producing mild or moderate side effects. The promising potential of AS1411 is its ability to be conjugated to drugs and nanoparticles. When a drug is bound to AS1411, the drug will localize to tumor cells leading to targeted therapy with fewer systemic side effects than traditional practices. AS1411 can also be bound to nanoparticles capable of detecting nucleolin at concentrations far lower than lab techniques used today for cancer diagnosis. AS1411 has a promising potential to change cancer diagnoses and treatment.

Unleashing novel horizons in advanced prostate cancer treatment: investigating the potential of prostate specific membrane antigen-targeted nanomedicine-based combination therapy

Prostate cancer (PCa) is a prevalent malignancy with increasing incidence in middle-aged and older men. Despite various treatment options, advanced metastatic PCa remains challenging with poor prognosis and limited effective therapies. Nanomedicine, with its targeted drug delivery capabilities, has emerged as a promising approach to enhance treatment efficacy and reduce adverse effects. Prostate-specific membrane antigen (PSMA) stands as one of the most distinctive and highly selective biomarkers for PCa, exhibiting robust expression in PCa cells. In this review, we explore the applications of PSMA-targeted nanomedicines in advanced PCa management. Our primary objective is to bridge the gap between cutting-edge nanomedicine research and clinical practice, making it accessible to the medical community. We discuss mainstream treatment strategies for advanced PCa, including chemotherapy, radiotherapy, and immunotherapy, in the context of PSMA-targeted nanomedicines. Additionally, we elucidate novel treatment concepts such as photodynamic and photothermal therapies, along with nano-theragnostics. We present the content in a clear and accessible manner, appealing to general physicians, including those with limited backgrounds in biochemistry and bioengineering. The review emphasizes the potential benefits of PSMA-targeted nanomedicines in enhancing treatment efficiency and improving patient outcomes. While the use of PSMA-targeted nano-drug delivery has demonstrated promising results, further investigation is required to comprehend the precise mechanisms of action, pharmacotoxicity, and long-term outcomes. By meticulous optimization of the combination of nanomedicines and PSMA ligands, a novel horizon of PSMA-targeted nanomedicine-based combination therapy could bring renewed hope for patients with advanced PCa.

New insight in urological cancer therapy: From epithelial-mesenchymal transition (EMT) to application of nano-biomaterials

A high number of cancer-related deaths (up to 90) are due to metastasis and simple definition of metastasis is new colony formation of tumor cells in a secondary site. In tumor cells, epithelial-mesenchymal transition (EMT) stimulates metastasis and invasion, and it is a common characteristic of malignant tumors. Prostate cancer, bladder cancer and renal cancer are three main types of urological tumors that their malignant and aggressive behaviors are due to abnormal proliferation and metastasis. EMT has been well-documented as a mechanism for promoting invasion of tumor cells and in the current review, a special attention is directed towards understanding role of EMT in malignancy, metastasis and therapy response of urological cancers. The invasion and metastatic characteristics of urological tumors enhance due to EMT induction and this is essential for ensuring survival and ability in developing new colonies in neighboring and distant tissues and organs. When EMT induction occurs, malignant behavior of tumor cells enhances and their tend in developing therapy resistance especially chemoresistance promotes that is one of the underlying reasons for therapy failure and patient death. The lncRNAs, microRNAs, eIF5A2, Notch-4 and hypoxia are among common modulators of EMT mechanism in urological tumors. Moreover, anti-tumor compounds such as metformin can be utilized in suppressing malignancy of urological tumors. Besides, genes and epigenetic factors modulating EMT mechanism can be therapeutically targeted for interfering malignancy of urological tumors. Nanomaterials are new emerging agents in urological cancer therapy that they can improve potential of current therapeutics by their targeted delivery to tumor site. The important hallmarks of urological cancers including growth, invasion and angiogenesis can be suppressed by cargo-loaded nanomaterials. Moreover, nanomaterials can improve chemotherapy potential in urological cancer elimination and by providing phototherapy, they mediate synergistic tumor suppression. The clinical application depends on development of biocompatible nanomaterials.

Contrast Agents of Magnetic Resonance Imaging and Future Perspective

In recent times, magnetic resonance imaging (MRI) has emerged as a highly promising modality for diagnosing severe diseases. Its exceptional spatiotemporal resolution and ease of use have established it as an indispensable clinical diagnostic tool. Nevertheless, there are instances where MRI encounters challenges related to low contrast, necessitating the use of contrast agents (CAs). Significant efforts have been made by scientists to enhance the precision of observing diseased body parts by leveraging the synergistic potential of MRI in conjunction with other imaging techniques and thereby modifying the CAs. In this work, our focus is on elucidating the rational designing approach of CAs and optimizing their compatibility for multimodal imaging and other intelligent applications. Additionally, we emphasize the importance of incorporating various artificial intelligence tools, such as machine learning and deep learning, to explore the future prospects of disease diagnosis using MRI. We also address the limitations associated with these techniques and propose reasonable remedies, with the aim of advancing MRI as a cutting-edge diagnostic tool for the future.

Magnetic Nanoparticle-Based High-Performance Positive and Negative Magnetic Resonance Imaging Contrast Agents

In recent decades, magnetic nanoparticles (MNPs) have attracted considerable research interest as versatile substances for various biomedical applications, particularly as contrast agents in magnetic resonance imaging (MRI). Depending on their composition and particle size, most MNPs are either paramagnetic or superparamagnetic. The unique, advanced magnetic properties of MNPs, such as appreciable paramagnetic or strong superparamagnetic moments at room temperature, along with their large surface area, easy surface functionalization, and the ability to offer stronger contrast enhancements in MRI, make them superior to molecular MRI contrast agents. As a result, MNPs are promising candidates for various diagnostic and therapeutic applications. They can function as either positive (T₁) or negative (T₂) MRI contrast agents, producing brighter or darker MR images, respectively. In addition, they can function as dual-modal T₁ and T₂ MRI contrast agents, producing either brighter or darker MR images, depending on the operational mode. It is essential that the MNPs are grafted with hydrophilic and biocompatible ligands to maintain their nontoxicity and colloidal stability in aqueous media. The colloidal stability of MNPs is critical in order to achieve a high-performance MRI function. Most of the MNP-based MRI contrast agents reported in the literature are still in the developmental stage. With continuous progress being made in the detailed scientific research on them, their use in clinical settings may be realized in the future. In this study, we present an overview of the recent developments in the various types of MNP-based MRI contrast agents and their in vivo applications.

Polyethylene glycol and chitosan functionalized manganese oxide nanoparticles for antimicrobial and anticancer activities

Biocompatible polymer-functionalized magnetic nanoparticles could offer promising applications in biomedical sciences. We fabricated polymer functionalized tri-manganese tetra oxide (Mn₃O₄) nanoparticles with the co-precipitation method and an octahedral crystal structure having a crystallite size of 10-17 nm was identified via XRD analyses. The SEM graph depicted the non-uniform and smooth surface of PEG-functionalized Mn₃O₄ NPs as compared to Mn₃O₄ and chitosan-coated Mn₃O₄ NPs. Elemental composition in the prepared sample was examined by EDX analysis. Various modes such as MnO, MnOH, OH, symmetric, and anti-symmetric of CH₂ attached to the spectrum of Mn₃O₄ NPs were observed with FTIR analysis. The magnetization factor decreased and increase the coreacivity and retentivity of surface functionalized Mn₃O₄-NPs was calculated via VSM analysis. In-vitro bioassay, antibacterial activity was tested against Escherichiacoli, Bacillus cereus, and anti-fungal activities against two Fusarium strains indicated clear antimicrobial activities. The MTT assay to examine the anticancer activity against the MCF-7 cancer cell line was performed and the T₁ MRI contrast agent demonstrated that PEG-coated Mn₃O₄ NPs exhibited anti-cancer activities. We propose that surface-functionalized magnetic NPs used for the treatment of cancer by using a remote controlled process of hyperthermia therapy.

Caveat Emptor: Commercialized Manganese Oxide Nanoparticles Exhibit Unintended Properties

Nano-encapsulated manganese oxide (NEMO) particles are noteworthy contrast agents for magnetic resonance imaging (MRI) due to their bright, pH-switchable signal ("OFF" to "ON" at low pH), high metal loading, and targeting capability for increased specificity. For the first time, we performed a head-to-head comparison of NEMO particles from In-house and commercialized sources (US Nano vs Nanoshel) to assess their potential as bright T₁ MRI contrast agents. Manganese oxide nanocrystals (MnO, Mn₂O₃, and Mn₃O₄) were systematically evaluated for size, chemistry, release of manganese ions, and MRI signal pre- and post-encapsulation within poly(lactic-co-glycolic acid) (PLGA). Suprisingly, a majority of the commercialized formulations were not as advertised by displaying unintended sizes, morphologies, chemistry, dissolution profiles, and/or MRI signal that precludes in vivo use. US Nano's Mn₃O₄ and Mn₂O₃ nanocrystals contained impurities that impacted Mn ion release as well as micron-sized rodlike structures. Nanoshel's MnO and Mn₂O₃ nanoparticles had very large hydrodynamic sizes (>600 nm). In-house MnO and Nanoshel's Mn₃O₄ nanoparticles demonstrated the best characteristics with brighter T₁ MRI signals, small hydrodynamic sizes, and high encapsulation efficiencies. Our findings highlight that researchers must confirm the properties of purchased nanomaterials before utilizing them in desired applications, as their experimental success may be impacted.

Ultra-small manganese dioxide nanoparticles with high T1 relaxivity for magnetic resonance angiography

Gadolinium (Gd)-based contrast agents (CAs) for clinical magnetic resonance imaging are facing the problems of low longitudinal relaxivity (r₁) and toxicity caused by gadolinium deposition. Manganese-based small molecule complexes and manganese oxide nanoparticles (MONs) are considered as potential alternatives to Gd-based CAs due to their better biocompatibility, but their relatively low r₁ values and complicated synthesis routes slow down their clinical translation. Herein, we presented a facile one-step co-precipitation method to prepare MONs using poly(acrylic acid) (PAA) as a coating agent (MnO₂/PAA NPs), which exhibited good biocompatibility and high r₁ values. A series of MnO₂/PAA NPs with different particle sizes were prepared and the relationship between the particle size and r₁ was studied, revealing that the MnO₂/PAA NPs with a particle size of 4.9 nm exhibited higher r₁. The finally obtained MnO₂/PAA NPs had a high r₁ value (29.0 Mn mM^-1 s^-1) and a low r₂/r₁ ratio (1.8) at 1.5 T, resulting in a strong T₁ contrast enhancement. In vivo magnetic resonance angiography with Sprague-Dawley (SD) rats further proved that the MnO₂/PAA NPs showed better angiographic performance at low-dosage administration than commercial Gadovist® (Gd-DO3A-Butrol). Moreover, the MnO₂/PAA NPs could be rapidly cleared out after imaging, which effectively minimized the toxic side effects. The MnO₂/PAA NPs are promising candidates for MR imaging of vascular diseases.

Nanomedicine for renal cell carcinoma: imaging, treatment and beyond

The kidney is a vital organ responsible for maintaining homeostasis in the human body. However, renal cell carcinoma (RCC) is a common malignancy of the urinary system and represents a serious threat to human health. Although the overall survival of RCC has improved substantially with the development of cancer diagnosis and management, there are various reasons for treatment failure. Firstly, without any readily available biomarkers, timely diagnosis has been greatly hampered. Secondly, the imaging appearance also varies greatly, and its early detection often remains difficult. Thirdly, chemotherapy has been validated as unavailable for treating renal cancer in the clinic due to its intrinsic drug resistance. Concomitant with the progress of nanotechnological methods in pharmaceuticals, the management of kidney cancer has undergone a transformation in the recent decade. Nanotechnology has shown many advantages over widely used traditional methods, leading to broad biomedical applications ranging from drug delivery, prevention, diagnosis to treatment. This review focuses on nanotechnologies in RCC management and further discusses their biomedical translation with the aim of identifying the most promising nanomedicines for clinical needs. As our understanding of nanotechnologies continues to grow, more opportunities to improve the management of renal cancer are expected to emerge.

Transferrin-Enabled Blood–Brain Barrier Crossing Manganese-Based Nanozyme for Rebalancing the Reactive Oxygen Species Level in Ischemic Stroke

(1) Background: Acute ischemic stroke (IS) is one of the main causes of human disability and death. Therefore, multifunctional nanosystems that effectively cross the blood–brain barrier (BBB) and efficiently eliminate reactive oxygen species (ROS) are urgently needed for comprehensive neuroprotective effects. (2) Methods: We designed a targeted transferrin (Tf)-based manganese dioxide nanozyme (MnO2@Tf, MT) using a mild biomimetic mineralization method for rebalancing ROS levels. Furthermore, MT can be efficiently loaded with edaravone (Eda), a clinical neuroprotective agent, to obtain the Eda-MnO2@Tf (EMT) nanozyme. (3) Results: The EMT nanozyme not only accumulates in a lesion area and crosses the BBB but also possesses satisfactory biocompatibility and biosafety based on the functional inheritance of Tf. Meanwhile, EMT has intrinsic hydroxyl radical-scavenging ability and superoxide-dismutase-like and catalase-like nanozyme abilities, allowing it to ameliorate ROS-mediated damage and decrease inflammatory factor levels in vivo. Moreover, the released Mn2+ ions in the weak acid environment of the lesion area can be used for magnetic resonance imaging (MRI) to monitor the treatment process. (4) Conclusions: Our study not only paves a way to engineer alternative targeted ROS scavengers for intensive reperfusion-induced injury in ischemic stroke but also provides new insights into the construction of bioinspired Mn-based nanozymes.

Boosting Vascular Imaging-Performance and Systemic Biosafety of Ultra-Small NaGdF4 Nanoparticles via Surface Engineering with Rationally Designed Novel Hydrophilic Block Co-Polymer

Revealing the anatomical structures, functions, and distribution of vasculature via contrast agent (CA) enhanced magnetic resonance imaging (MRI) is crucial for precise medical diagnosis and therapy. The clinically used MRI CAs strongly rely on Gd-chelates, which exhibit low T₁ relaxivities and high risks of nephrogenic systemic fibrosis (NSF) for patients with renal dysfunction. It is extremely important to develop high-performance and safe CAs for MRI. Herein, it is reported that ultra-small NaGdF₄ nanoparticles (UGNs) can serve as an excellent safe MRI CA via surface engineering with rationally designed novel hydrophilic block co-polymer (BP_n ). By optimizing the polymer molecular weights, the polymer-functionalized UGNs (i.e., UGNs-BP₁₄ ) are obtained to exhibit remarkably higher relaxivity (11.8 mm^-1 s^-1 at 3.0 T) than Gd-DTPA (3.6 mm^-1 s^-1 ) due to their ultracompact and abundant hydrophilic surface coating. The high performance of UGNs-BP₁₄ enables us to sensitively visualize microvasculature with a small diameter of ≈0.17 mm for up to 2 h, which is the thinnest blood vessel and the longest time window for low field (1.0 T) MR angiography ever reported, and cannot be achieved by using the clinically used Gd-DTPA under the same conditions. More importantly, renal clearable UGNs-BP₁₄ show lower risks of inducing NSF in comparison with Gd-DTPA due to their negligible release of Gd³⁺ ions after modification with the novel hydrophilic block copolymer. The study presents a novel avenue for boosting imaging-performance and systemic biosafety of UGNs as a robust MRI CA with great potential in precise diagnosis of vasculature-related diseases.

Progress in cancer drug delivery based on AS1411 oriented nanomaterials

Targeted cancer therapy has become one of the most important medical methods because of the spreading and metastatic nature of cancer. Based on the introduction of AS1411 and its four-chain structure, this paper reviews the research progress in cancer detection and drug delivery systems by modifying AS1411 aptamers based on graphene, mesoporous silica, silver and gold. The application of AS1411 in cancer treatment and drug delivery and the use of AS1411 as a targeting agent for the detection of cancer markers such as nucleoli were summarized from three aspects of active targeting, passive targeting and targeted nucleic acid apharmers. Although AS1411 has been withdrawn from clinical trials, the research surrounding its structural optimization is still very popular. Further progress has been made in the modification of nanoparticles loaded with TCM extracts by AS1411.

A Comprehensive Updated Review on Magnetic Nanoparticles in Diagnostics

Magnetic nanoparticles (MNPs) have been studied for diagnostic purposes for decades. Their high surface-to-volume ratio, dispersibility, ability to interact with various molecules and superparamagnetic properties are at the core of what makes MNPs so promising. They have been applied in a multitude of areas in medicine, particularly Magnetic Resonance Imaging (MRI). Iron oxide nanoparticles (IONPs) are the most well-accepted based on their excellent superparamagnetic properties and low toxicity. Nevertheless, IONPs are facing many challenges that make their entry into the market difficult. To overcome these challenges, research has focused on developing MNPs with better safety profiles and enhanced magnetic properties. One particularly important strategy includes doping MNPs (particularly IONPs) with other metallic elements, such as cobalt (Co) and manganese (Mn), to reduce the iron (Fe) content released into the body resulting in the creation of multimodal nanoparticles with unique properties. Another approach includes the development of MNPs using other metals besides Fe, that possess great magnetic or other imaging properties. The future of this field seems to be the production of MNPs which can be used as multipurpose platforms that can combine different uses of MRI or different imaging techniques to design more effective and complete diagnostic tests.

Recent advancements and future submissions of silica core-shell nanoparticles

The core-shell silica-based nanoparticles (CSNPs) possess outstanding properties for developing next-generation therapeutics. CSNPs provide greater surface area owing to their mesoporous structure, which offers a high opportunity for surface modification. This review highlights the potential of core-shell silica-based nanoparticle (CSNP) based injectable nanotherapeutics (INT); its role in drug delivery, biomedical imaging, light-triggered phototherapy, Plasmonic enhancers, gene delivery, magnetic hyperthermia, immunotherapy, and potential as next-generation theragnostic. Specifically, the conceptual crosstalk on modern synthetic strategies, biodistribution profiles with a mechanistic view on the therapeutics loading and release modeling are dealt in detail. The manuscript also converses the challenges associated with CSNPs, regulatory hurdles, and their current market position.

Complex supramolecular fiber formed by coordination-induced self-assembly of benzene-1,3,5-tricarboxamide (BTA)

HYPOTHESIS

In the quest for large but well-controlled supramolecular structures, the discotic benzene-1,3,5-tricarboxamide (BTA) has received quite some attention, because it can form hydrogen-bonded stacks that can be regarded as supramolecular polymers of which the single BTA molecule is the monomer. In this report, we consider a more complex BTA-based supramolecular polymer, namely one that is built up from supramolecular 'monomers'.

EXPERIMENTS

We design a tris-ligand L₃ consisting of a BTA core carrying three dipicolinic acid (DPA) groups. L₃ itself is too small to form polymers, but in the presence of appropriate metal ions, each L₃ can form three coordination bonds and so form (L₃)_n clusters that are large enough to stack successfully: at an appropriate metal dose, long and stable filaments with a cross-sectional diameter of 12 nm appear. We monitor the growth process by UV-vis spectroscopy and light scattering, and use small angle X-ray scattering (SAXS), TEM as well as molecular simulation to confirm the filamentous structure of the fibers and determine their dimensions.

FINDINGS

The formation and structure of the fiber are very similar for various transition metal ions, which enables introducing different functionalities, e.g., magnetic relaxivity, by proper choice of the metal ions. Hence, we obtain a doubly supramolecular polymer, connected axially by hydrogen bonds, and radially by coordination bonds. Not only does this realize a higher level of complexity, but it also allows to easily introduce and vary metal-derived functionalities.

Manganese-based advanced nanoparticles for biomedical applications: future opportunity and challenges

Nanotechnology is the most promising technology to evolve in the last decade. Recent research has shown that transition metal nanoparticles especially manganese (Mn)-based nanoparticles have great potential for various biomedical applications due to their unique fundamental properties. Therefore, globally, scientists are concentrating on the development of various new manganese-based nanoparticles (size and shape dependent) due to their indispensable utilities. Although numerous reports are available regarding the use of manganese nanoparticles, there is no comprehensive review highlighting the recent development of manganese-based nanomaterials and their potential applications in the area of biomedical sciences. The present review article provides an overall survey on the recent advancement of manganese nanomaterials in biomedical nanotechnology and other fields. Further, the future perspectives and challenges are also discussed to explore the wider application of manganese nanoparticles in the near future. Overall, this review presents a fundamental understanding and the role of manganese in various fields, which will attract a wider spectrum of the scientific community.

Spontaneous reduction of KMnO4 with MoS2 quantum dots for glutathione sensing in tumors

Transition-metal dichalcogenides (TMDCs) have attracted a lot of attention due to their electronic, optical, mechanical, and catalytic properties. In addition, TMDCs possess rich redox chemistry that enables the decoration of metal nanoparticles directly on their surfaces. In this paper, MnO2/MoS2 nanocomplexes were obtained by the spontaneous reduction of KMnO4 with MoS2 QDs as the reductive agent. The formed MnO2/MoS2 nanocomplexes exhibited activated fluorescence and MR imaging signal in the presence of glutathione (GSH). After conjugation with an AS1411 aptamer, specific in vivo MR imaging and fluorescence labeling of the 786-O tumor cells were realized, showing their promising potential for biomedical applications.

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.

Manganese-Based Targeted Nanoparticles for Postoperative Gastric Cancer Monitoring via Magnetic Resonance Imaging

Postoperative recurrence is a common and severe problem in the treatment of gastric cancer; consequently, a prolonged course of chemotherapy treatment is inevitable. Monitoring by imaging could provide an accurate evaluation of the therapeutic effects, which would be beneficial to guide a treatment strategy adjustment over time. However, current imaging technologies remain insufficient for the continuous postoperative monitoring of gastric cancer. In this case, molecular imaging offers an efficient strategy. Targetable contrast agents are an essential part of molecular imaging, which could greatly enhance the accuracy and quality of monitoring. Herein, we synthesized a Mn-based contrast agent for magnetic resonance imaging (MRI) of gastric cancer monitoring. Initially, small-sized Mn3O4 nanoparticles (NPs) were synthesized. Then, a functionalized polyethylene glycol (PEG) lipid was attached to the surface of the Mn3O4 NPs, to improve biocompatibility. The targetable MRI contrast agent (Mn3O4@PEG-RGD NPs) was further prepared by the conjugation of the arginine-glycine-aspartic acid (RGD) peptides. The completed Mn3O4@PEG-RGD NPs had the small size of 7.3 ± 2.7 nm and exhibited superior colloidal stability in different solution environments. In addition, Mn3O4@PEG-RGD NPs exhibited reliable biotolerance and low toxicity both in vitro and in vivo. Imaging experiments amply demonstrated that Mn3O4@PEG-RGD NPs could efficiently accumulate in gastric cancer tissues and cells via RGD mediation, and immediately significantly increased the MRI effects. Through this study, we can conclude that Mn3O4@PEG-RGD NPs have the potential to be a novel MRI contrast agent for the postoperative monitoring of gastric cancer.

Absorption, distribution, metabolism, and excretion of nanocarriers in vivo and their influences

As one of the most promising and effective delivery systems for targeted controlled-release drugs, nanocarriers (NCs) have been widely studied. Although the development of nanoparticle preparations is very prosperous, the safety and effectiveness of NCs are not guaranteed and cannot be precisely controlled due to the unclear processes of absorption, distribution, metabolism, and excretion (ADME), as well as the drug release mechanism of NCs in the body. Thus, the approval of NCs for clinical use is extremely rare. This paper reviews the research progress and challenges of using NCs in vivo based on a review of several hundred closely related publications. First, the ADME of NCs under different administration routes is summarized; second, the influences of the physical, chemical, and biosensitive properties, as well as targeted modifications of NCs on their disposal process, are systematically analyzed; third, the tracer technology related to the in vivo study of NCs is elaborated; and finally, the challenges and perspectives of nanoparticle research in vivo are introduced. This review may help readers to understand the current research progress and challenges of nanoparticles in vivo, as well as of tracing technology in nanoparticle research, to help researchers to design safer and more efficient NCs. Furthermore, this review may aid researchers in choosing or exploring more suitable tracing technologies to further advance the development of nanotechnology.

New Strategies in the Design of Paramagnetic CAs

Nowadays, magnetic resonance imaging (MRI) is the first diagnostic imaging modality for numerous indications able to provide anatomical information with high spatial resolution through the use of magnetic fields and gradients. Indeed, thanks to the characteristic relaxation time of each tissue, it is possible to distinguish between healthy and pathological ones. However, the need to have brighter images to increase differences and catch important diagnostic details has led to the use of contrast agents (CAs). Among them, Gadolinium-based CAs (Gd-CAs) are routinely used in clinical MRI practice. During these last years, FDA highlighted many risks related to the use of Gd-CAs such as nephrotoxicity, heavy allergic effects, and, recently, about the deposition within the brain. These alerts opened a debate about the opportunity to formulate Gd-CAs in a different way but also to the use of alternative and safer compounds to be administered, such as manganese- (Mn-) based agents. In this review, the physical principle behind the role of relaxivity and the T₁ boosting will be described in terms of characteristic correlation times and inner and outer spheres. Then, the recent advances in the entrapment of Gd-CAs within nanostructures will be analyzed in terms of relaxivity boosting obtained without the chemical modification of CAs as approved in the chemical practice. Finally, a critical evaluation of the use of manganese-based CAs will be illustrated as an alternative ion to Gd due to its excellent properties and endogenous elimination pathway.

Current Drug Nano-targeting Strategies for Improvement in the Diagnosis and Treatment of Prevalent Pathologies such as Cardiovascular and Renal Diseases

BACKGROUND

The kidney and cardiovascular system are closely related to each other during the modulation of the cardiovascular homeostasis. However, the search for new alternatives for the treatment and diagnosis of cardiovascular diseases does not take into account this relationship, so their evaluation results and the advantages offered by their global and integrative analysis are wasted. For example, a variety of receptors that are overexpressed in both pathologies is large enough to allow expansion in the search for new molecular targets and ligands. Nanotechnology offers pharmacological targeting strategies to kidney, heart, and blood vessels for overcoming one of the essential restrictions of traditional cardiovascular therapies the ones related to their unspecific pharmacodynamics distribution in these critical organs.

RECENT FINDINGS

Drug or contrast agent nano-targeting for treatment or diagnosis of atherosclerosis, thrombosis, renal cancer or fibrosis, glomerulonephritis, among other renal, cardiac and blood vessels pathologies would allow an increase in their efficacy and a reduction of their side effects. Such effects are possible because, through pharmacological targeting, the drug is mainly found at the desired site. Review Purpose: In this mini-review, active, passive, and physical targeting strategies of several nanocarriers that have been assessed and proposed for the treatment and diagnosis of different cardiovascular diseases, are being addressed.

Water-Nanomaterial Interaction to Escalate Twin-Mode Magnetic Resonance Imaging

Molecular imaging has gained utmost importance in the recent past in early diagnosis of diseases. In comparison to other imaging modalities, magnetic resonance imaging (MRI) has proven to extend its abilities not only for its usage of non-ionizing radiation but also for the high spatial resolution in soft tissues. A major limitation faced by MRI is the sensitivity in detecting diseased conditions until a certain stage. At present, this limitation is overcome with the use of contrast agents that show potential in altering the T1 and T2 relaxation times of the hydrogen protons. This modulation to the relaxation times leads to better contrast differences based on the type of contrast agent and the pulse sequence being engaged for acquiring images. Water molecules, as the major contributor of hydrogen protons, are proven to interact with such contrast agents. Major drawbacks noted with the marketed MRI contrast agents are their toxicity and renal clearance. To conquer these issues, magnetic nanomaterials are being researched for their abilities to match the contrast enhancement offered by traditional agents reducing their drawbacks. Furthermore, comparative diagnosis with both T1 and T2 contrast at the same time has also interested investigators. To achieve this, twin mode T1 and T2 weighted contrast agents are developed utilizing the remarkable properties extended by magnetic nanoplatforms. As a step forward, multimodal imaging agents are also being engineered based on these magnetic nanoplatforms that will generate cross-verified diagnoses using multiple imaging modalities with a unique imaging agent. This review starts by introducing the basics of MRI with major focus on the typical interactions of water molecules with a variety of magnetic nanomaterials. The review also concentrates on the clinical needs and nanomaterials available for twin T1 and T2 contrast with a minor introduction to multimodal imaging agents. In conclusion, the advent of MRI with the advantages offered by magnetic nanomaterials is summarized, leading to insights for future developments.

Magnetic Nanoparticles as MRI Contrast Agents

Iron oxide nanoparticles (IONPs) have emerged as a promising alternative to conventional contrast agents (CAs) for magnetic resonance imaging (MRI). They have been extensively investigated as CAs due to their high biocompatibility and excellent magnetic properties. Furthermore, the ease of functionalization of their surfaces with different types of ligands (antibodies, peptides, sugars, etc.) opens up the possibility of carrying out molecular MRI. Thus, IONPs functionalized with epithelial growth factor receptor antibodies, short peptides, like RGD, or aptamers, among others, have been proposed for the diagnosis of various types of cancer, including breast, stomach, colon, kidney, liver or brain cancer. In addition to cancer diagnosis, different types of IONPs have been developed for other applications, such as the detection of brain inflammation or the early diagnosis of thrombosis. This review addresses key aspects in the development of IONPs for MRI applications, namely, synthesis of the inorganic core, functionalization processes to make IONPs biocompatible and also to target them to specific tissues or cells, and finally in vivo studies in animal models, with special emphasis on tumor models.

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.

GMBP1-conjugated manganese oxide nanoplates for in vivo monitoring of gastric cancer MDR using magnetic resonance imaging

Multidrug resistance (MDR) is a huge challenge for gastric cancer chemotherapy. Therefore, MDR accurate monitoring is of great significance for the treatment of gastric cancer. GMBP1, an extracellular internalization peptide, can target MDR gastric cancer cells through specific binding to GRP78, which is an MDR-related protein that is overexpressed in gastric cancer cells. Herein, we constructed GMBP1 conjugated Mn₃O₄ nanoplates (Mn₃O₄@PEG-GMBP1 NPs) for in vivo monitoring of MDR gastric cancer through magnetic resonance imaging (MRI). The generated Mn₃O₄@PEG-GMBP1 NPs had a size of about 11 nm and exhibited a good colloidal stability in PBS and in 10% FBS medium. Serial in vivo MRI studies in mice demonstrated that the magnetic resonance signal intensity, at the tumor site, reached a peak at 3 h after tail vein injection of Mn₃O₄@PEG-GMBP1 NPs. The specific targeting ability of MDR gastric cancer cells (SGC7901/ADR) by Mn₃O₄@PEG-GMBP1 NPs was authenticated in vitro, in vivo and by immunofluorescence analysis experiments. The systematic safety evaluation indicated that the toxicity of Mn₃O₄@PEG-GMBP1 NPs in mice was negligible. Therefore, the GMBP1 conjugated Mn₃O₄ nanoplates can be clinically used for accurate imaging and monitoring of MDR gastric cancer.

Manganese Oxide Nanomaterials: Synthesis, Properties, and Theranostic Applications

Despite the comprehensive applications in bioimaging, biosensing, drug/gene delivery, and tumor therapy of manganese oxide nanomaterials (MONs including MnO₂ , MnO, Mn₂ O₃ , Mn₃ O₄ , and MnO_x ) and their derivatives, a review article focusing on MON-based nanoplatforms has not been reported yet. Herein, the representative progresses of MONs on synthesis, heterogene, properties, surface modification, toxicity, imaging, biodetection, and therapy are mainly introduced. First, five kinds of primary synthetic methods of MONs are presented, including thermal decomposition method, exfoliation strategy, permanganates reduction method, adsorption-oxidation method, and hydro/solvothermal. Second, the preparations of hollow MONs and MON-based composite materials are summarized specially. Then, the chemical properties, surface modification, and toxicity of MONs are discussed. Next, the diagnostic applications including imaging and sensing are outlined. Finally, some representative rational designs of MONs in photodynamic therapy, photothermal therapy, chemodynamic therapy, sonodynamic therapy, radiotherapy, magnetic hyperthermia, chemotherapy, gene therapy, starvation therapy, ferroptosis, immunotherapy, and various combination therapy are highlighted.

Recent progress in nanomaterial-based electrochemical biosensors for pathogenic bacteria

This review (with 118 refs.) discusses the progress made in electroanalytical methods based on the use of organic and inorganic nanomaterials for the determination of bacteria, specifically of E. coli, Salmonella, Staphylococcus, Mycobacterium, Listeria and Klebsiella species. We also discuss advantages and limitations of electrochemical methods. Strategies based on the use of aptamers, DNA and antibodies are covered. Following an introduction into electrochemical biosensing, a first large section covers methods for pathogen detection using metal nanoparticles, with subsections on silver nanoparticles, gold nanoparticles, magnetic nanoparticles and carbon-based nanomaterials. A second large section covers methods based on the use of organic nanocomposites, graphene and its derivatives. Other nanoparticles are treated in a final section. Several tables are presented that give an overview on the wealth of methods and materials. A concluding section summarizes the current status, addresses challenges, and gives an outlook on potential future trends. Graphical abstract This review demonstrates the progress made in electroanalytical methods based on the use of organic and inorganic nanomaterials for the detection and determination of pathogenic bacteria. We also discuss advantages and limitations of electrochemical methods. Strategies based on the use of aptamers, DNA and antibodies are covered.

Advances in Contrast Agents for Contrast-Enhanced Magnetic Resonance Imaging

INTRODUCTION

Magnetic resonance imaging (MRI) is a well-established medical invention in modern medical technology diagnosis. It is a nondestructive, versatile, and sensitive technique with a high spatial resolution for medical diagnosis. However, MRI has some limitations in differentiating certain tissues, particularly tiny blood vessels, pathological to healthy tissues, specific tumors, and inflammatory conditions such as arthritis, atherosclerosis, and multiple sclerosis. The contrast agent (CA) assisted imaging is the best possible solution to resolve the limitations of MRI.

METHOD

The literature review was carried out using the keywords, "MRI, T1&T2 relaxation, MRI CAs, delivery and adverse effects, classification of CAs." The tools used for the literature search were PubMed, Scopus, and Google Scholar.

RESULT AND DISCUSSION

The literature findings focus on MRI technique, limitations, and possible solutions. Primarily, the review focuses on the mechanism of CAs in image formation with detailed explanations of T1 and T2 relaxations, the mechanism of the MRI-CA image formations. This review presents the adverse effects of CA as well as available marketed formulations and recent patents to extent complete information about the MRI-CA.

CONCLUSION

MRI generates detailed visual information of various tissues with high resolution and contrast. The proton present in the biological fluid plays a crucial role in MR image formation, and it is unable to distinguish pathological conditions in many cases. The CAs are the best solution to resolve the limitation by interacting with native protons. The present review discusses the mechanism of CAs in contrast enhancement and its broad classification with the latest literature. Furthermore, the article presents information about CA biodistribution and adverse effects. The review concludes with an appropriate solution for adverse effects and presents the future prospective for researchers to develop advanced formulations.

Manganese Oxide Nanoparticles As MRI Contrast Agents In Tumor Multimodal Imaging And Therapy

Contrast agents (CAs) play a crucial role in high-quality magnetic resonance imaging (MRI) applications. At present, as a result of the Gd-based CAs which are associated with renal fibrosis as well as the inherent dark imaging characteristics of superparamagnetic iron oxide nanoparticles, Mn-based CAs which have a good biocompatibility and bright images are considered ideal for MRI. In addition, manganese oxide nanoparticles (MONs, such as MnO, MnO2, Mn3O4, and MnOx) have attracted attention as T1-weighted magnetic resonance CAs due to the short circulation time of Mn(II) ion chelate and the size-controlled circulation time of colloidal nanoparticles. In this review, recent advances in the use of MONs as MRI contrast agents for tumor detection and diagnosis are reported, as are the advances in in vivo toxicity, distribution and tumor microenvironment-responsive enhanced tumor chemotherapy and radiotherapy as well as photothermal and photodynamic therapies.

The Transition from Metal-Based to Metal-Free Contrast Agents for T1 Magnetic Resonance Imaging Enhancement

Magnetic resonance imaging (MRI) has received significant attention as the noninvasive diagnostic technique for complex diseases. Image-guided therapeutic strategy for diseases such as cancer has also been at the front line of biomedical research, thanks to the innovative MRI, enhanced by the prior delivery of contrast agents (CAs) into patients' bodies through injection. These CAs have contributed a great deal to the clinical utility of MRI but have been based on metal-containing compounds such as gadolinium, manganese, and iron oxide. Some of these CAs have led to cytotoxicities such as the incurable Nephrogenic Systemic Fibrosis (NSF), resulting in their removal from the market. On the other hand, CAs based on organic nitroxide radicals, by virtue of their structural composition, are metal free and without the aforementioned drawbacks. They also have improved biocompatibility, ease of functionalization, and long blood circulation times, and have been proven to offer tissue contrast enhancement with longitudinal relaxivities comparable with those for the metal-containing CAs. Thus, this Review highlights the recent progress in metal-based CAs and their shortcomings. In addition, the remarkable goals achieved by the organic nitroxide radical CAs in the enhancement of MR images have also been discussed extensively. The focal point of this Review is to emphasize or demonstrate the crucial need for transition into the use of organic nitroxide radicals-metal-free CAs-as against the metal-containing CAs, with the aim of achieving safer application of MRI for early disease diagnosis and image-guided therapy.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

A literature review on multimodality molecular imaging nanoprobes for cancer detection

Molecular imaging techniques using nanoparticles have significant potential to be widely used for the detection of various types of cancers. Nowadays, there has been an increased focus on developing novel nanoprobes as molecular imaging contrast enhancement agents in nanobiomedicine. The purpose of this review article is to summarize the use of a variety of nanoprobes and their current achievements in accurate cancer imaging and effective treatment. Nanoprobes are rapidly becoming potential tools for cancer diagnosis by using novel molecular imaging modalities such as Ultrasound (US) imaging, Computerized Tomography (CT), Single Photon Emission Tomography (SPECT) and Positron Emission Tomography (PET), Magnetic Resonance Imaging (MRI), and Optical Imaging. These imaging modalities may facilitate earlier and more accurate diagnosis and staging the most of cancers.

Mn(II) compounds as an alternative to Gd-based MRI probes

Mn(II) has several favorable physicochemical characteristics and a good toxicity profile, which makes it a viable alternative to the Gd(III)-based MRI contrast agents currently used in clinics. Although many studies have been undertaken in the last 10 years, this is a field of investigation still in rapid and continuous development. This review aims to critically discuss the chemical and magnetic properties of Mn(II) compounds relevant as MRI probes, both small complexes and nanosystems containing a large number of metal centers, the possible approaches for optimizing their efficiency by understanding the role of various molecular parameters that control the relaxation processes, and the most important issues related to stability and kinetic inertness.

Nanoparticle-Based Paramagnetic Contrast Agents for Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a noninvasive medical imaging modality that is routinely used in clinics, providing anatomical information with micron resolution, soft tissue contrast, and deep penetration. Exogenous contrast agents increase image contrast by shortening longitudinal (T 1) and transversal (T 2) relaxation times. Most of the T 1 agents used in clinical MRI are based on paramagnetic lanthanide complexes (largely Gd-based). In moving to translatable formats of reduced toxicity, greater chemical stability, longer circulation times, higher contrast, more controlled functionalisation and additional imaging modalities, considerable effort has been applied to the development of nanoparticles bearing paramagnetic ions. This review summarises the most relevant examples in the synthesis and biomedical applications of paramagnetic nanoparticles as contrast agents for MRI and multimodal imaging. It includes the most recent developments in the field of production of agents with high relaxivities, which are key for effective contrast enhancement, exemplified through clinically relevant examples.

Nanocomposites as biomolecules delivery agents in nanomedicine

Nanoparticles (NPs) are atomic clusters of crystalline or amorphous structure that possess unique physical and chemical properties associated with a size range of between 1 and 100 nm. Their nano-sized dimensions, which are in the same range as those of vital biomolecules, such as antibodies, membrane receptors, nucleic acids, and proteins, allow them to interact with different structures within living organisms. Because of these features, numerous nanoparticles are used in medicine as delivery agents for biomolecules. However, off-target drug delivery can cause serious side effects to normal tissues and organs. Considering this issue, it is essential to develop bioengineering strategies to significantly reduce systemic toxicity and improve therapeutic effect. In contrast to passive delivery, nanosystems enable to obtain enhanced therapeutic efficacy, decrease the possibility of drug resistance, and reduce side effects of "conventional" therapy in cancers. The present review provides an overview of the most recent (mostly last 3 years) achievements related to different biomolecules used to enable targeting capabilities of highly diverse nanoparticles. These include monoclonal antibodies, receptor-specific peptides or proteins, deoxyribonucleic acids, ribonucleic acids, [DNA/RNA] aptamers, and small molecules such as folates, and even vitamins or carbohydrates.