Mn₃[Co(CN)₆]₂@SiO₂ core-shell nanocubes: novel bimodal contrast agents for MRI and optical imaging

Novel Salinomycin-Based Paramagnetic Complexes-First Evaluation of Their Potential Theranostic Properties

Combining therapeutic with diagnostic agents (theranostics) can revolutionize the course of malignant diseases. Chemotherapy, hyperthermia, or radiation are used together with diagnostic methods such as magnetic resonance imaging (MRI). In contrast to conventional contrast agents (CAs), which only enable non-specific visualization of tissues and organs, the theranostic probe offers targeted diagnostic imaging and therapy simultaneously.

METHODS

Novel salinomycin (Sal)-based theranostic probes comprising two different paramagnetic metal ions, gadolinium(III) (Gd(III)) or manganese(II) (Mn(II)), as signal emitting motifs for MRI were synthesized and characterized by elemental analysis, infrared spectral analysis (IR), electroparamagnetic resonance (EPR), thermogravimetry (TG) differential scanning calorimetry (DSC) and electrospray ionization mass spectrometry (ESI-MS). To overcome the water insolubility of the two Sal-complexes, they were loaded into empty bacterial ghosts (BGs) cells as transport devices. The potential of the free and BGs-loaded metal complexes as theranostics was evaluated by in vitro relaxivity measurements in a high-field MR scanner and in cell culture studies.

RESULTS

Both the free Sal-complexes (Gd(III) salinomycinate (Sal-Gd(III) and Mn(II) salinomycinate (Sal-Mn(II)) and loaded into BGs demonstrated enhanced cytotoxic efficacy against three human tumor cell lines (A549, SW480, CH1/PA-1) relative to the free salinomycinic acid (Sal-H) and its sodium complex (Sal-Na) applied as controls with IC₅₀ in a submicromolar concentration range. Moreover, Sal-H, Sal-Gd(III), and Sal-Mn(II) were able to induce perturbations in the cell cycle of treated colorectal and breast human cancer cell lines (SW480 and MCF-7, respectively). The relaxivity (r₁) values of both complexes as well as of the loaded BGs, were higher or comparable to the relaxivity values of the clinically applied contrast agents gadopentetate dimeglumine and gadoteridol.

CONCLUSION

This research is the first assessment that demonstrates the potential of Gd(III) and Mn(II) complexes of Sal as theranostic agents for MRI. Due to the remarkable selectivity and mode of action of Sal as part of the compounds, they could revolutionize cancer therapy and allow for early diagnosis and monitoring of therapeutic follow-up.

Designing heterostructured core@satellite Prussian Blue Analogue@Au–Ag nanoparticles: Effect on the magnetic properties and catalytic activity

Prussian Blue Analogue@Au–Ag nanoparticles: Effect on the magnetic properties and catalytic activity.

Robust dual modality antibacterial action using silver-Prussian blue nanoscale coordination polymer

We report the synthesis of novel silver-doped Prussian blue nanoscale coordination polymers (SPB NCPs), for dual modality photothermal ablation and oxidative toxicity in bacterial cells. The comparison of SPB NCPs (having Fe-CN-Ag bonds) with the conventionally used Prussian blue nanoscale coordination polymers (PB NCPs, having Fe-CN-Fe bonds) was investigated in terms of their physical and therapeutic properties. It was observed that both PB and SPB NCPs have similar physical dimensions, crystalline phase and optical properties. Both these NCPs showed robust photothermal effect by heat generation (hyperthermia) upon exposure to red laser light. However, among the two, only SPB NCP showed oxidase-like activity by generating H₂O₂ in aqueous medium, presumably due to its silver content. In vitro antibacterial studies revealed that the SPB NCPs, but not PB NCPs, show inherent toxicity towards bacteria with an IC₅₀ value close to 2.5 μg/ml. It can be inferred that this toxicity is oxidative in nature, as a result of the oxidase-like behaviour shown by SPB NCPs. Furthermore, light activation resulted in substantial additional antibacterial effect (photothermal toxicity) in bacterial cells treated with SPB NCPs. In comparison, marginal additional photothermal toxicity was observed in PB NCP-treated bacteria. Thus, we conclude that the combination of dual modality oxidative and photothermal toxicities demonstrated by SPB NCPs, but not by control PB NCPs, makes the former promising antibacterial agents at low dosages.

Computational characterization of halogen vapor attachment, diffusion and desorption processes in zeolitic imidazolate framework-8

Computational simulation methods are used for characterizing the detailed attachment, diffusion and desorption of halogen vapor molecules in zeolitic imidazolate framework-8 (ZIF-8). The attachment energies of Cl2, Br2 and I2 are -55.2, -48.5 and -43.0 kJ mol-1, respectively. The framework of ZIF-8 is disrupted by Cl2, which bonds with Zn either on the surface or by freely diffusing into the cage. A framework deformation on the surface of ZIF-8 can be caused by the attachment of Br2, but only reorientation of the 2-methylimidazolate linkers (mIms) for I2. In diffusion, the halogen molecules have a tendency to vertically permeate the apertures of cages followed with swing effect implemented by the mIms. Larger rotation angles of mIms are caused by Br2 because of its stronger interaction with mIms than I2. A maximum of 7 Br2 or 5 I2 molecules can be accommodated in one cage. Br2 are clinging to the mIms and I2 are arranged as crystal layout in the cages, therefore in desorption processes molecules attached to the surface and free inside are desorbed while some remained. These results are beneficial for better understanding the adsorption and desorption processes of halogen vapors in the porous materials.

Large-scale synthesis of monodisperse Prussian blue nanoparticles for cancer theranostics via an "in situ modification" strategy

Background

The intrinsic properties of Prussian blue (PB) nanoparticles make them an attractive tool in nanomedicine, including magnetic resonance imaging (MRI), photoacoustic imaging (PAI), and photothermal therapy (PTT) properties. However, there still remains the challenge of their poor dispersible stability in the physiological environment. In this study, we developed an efficient hydrothermal method to address the poor dispersible stability of PB nanoparticles in the physiological environment.

Materials and methods

The concentration of H⁺, the mass of polyvinylpyrrolidone (PVP), and iron sources (K₃[Fe(CN)₆]) are very vital in the preparation of PB nanoparticles. Through exploring the preparation process, optimized PB nanoparticles (OPBs) with excellent physiological stability were prepared. Hydrodynamic diameter and UV-vis absorption properties were measured to verify the stability of the prepared OPBs. Properties of dual-mode imaging, including MRI/PAI, and PTT of OPBs were investigated both in vitro and in vivo. In addition, the in vivo biosafety of OPBs was systematically assessed.

Results

OPBs were stable in different environments including various media, pH, and temperatures for at least 90 days, indicating that they are suitable for biomedical application via intravenous administration and easily stored in a robust environment. Compared with other research into the synthesis of PB nanoparticles, the “in situ modification” synthesis of PB nanoparticles had advantages, including a simple process, low cost, and easy mass preparation. OPBs showed no significant signs of toxicity for 90 days. As a proof of concept, the OPBs served as dual-mode image contrast agents and photothermal conversion agents for cancer diagnosis and therapy both in vitro and in vivo.

Conclusion

Our findings suggest a facile but efficient strategy with low cost to address the poor dispersible stability of PB nanoparticles in physiological environments. This will promote the development of further clinical transformations of PB nanoparticles, especially in cancer theranostics.

Multimodal Prussian blue analogs as contrast agents for X-ray computed tomography

Prussian blue analogs (PBAs) are versatile materials with a wide range of applications. Due to their tunability, intrinsic biocompatibility, as well as low toxicity, these nanoscale coordination polymers have been successfully studied as multimodal contrast agents for multiple imaging techniques. Herein, we report the expanded biomedical application of PBAs to X-ray computed tomography (CT). In our systematic study of the series A{MnII[FeIII(CN)6]} (A = K+, Rb+, Cs+), we showed that derivatives incorporating Rb+ and Cs+ ions in the tetrahedral sites of the parent face-centered cubic cyano-bridged networks exhibited substantially increased X-ray attenuation coefficients, thus yielding significant contrast compared to the clinically approved X-ray contrast agent iohexol at the same concentrations. Additionally, our μ-CT studies revealed that these PBAs could be useful as dual-energy CT contrast agents for different biological specimens by using the lower varying scanning X-ray tube voltages. Finally, in vitro studies using U87-Luc cells treated with PBAs, including cellular CT imaging and bioluminescence cell viability assays, revealed that PBAs were taken up by the glioblastoma cells, with moderate biocompatibility at concentrations below the mM range.

Bimetallic Zeolitic Imidazolate Framework as an Intrinsic Two-Photon Fluorescence and pH-Responsive MR Imaging Agent

Zeolitic imidazolate framework-8 (ZIF-8) has received wide attention in recent years as a potential drug vehicle for the treatment of cancer due to its acid-responsiveness and moderate biocompatibility. However, its congenital deficiency of intrinsic imaging capability limits its wider applications; therefore, a postsynthetic exchange approach was utilized to introduce paramagnetic manganese(II) ions into the ZIF-8 matrix. As a result, bimetallic zeolitic imidazolate frameworks (Mn-Zn-ZIF) were thus fabricated and exhibited pH-responsive T1-weighted magnetic resonance imaging (MRI) contrast effect. Remarkably, we also found its own fluorescence derived from 2-methylimidazole, which is the first report of the intrinsic two-photon fluorescence imaging of ZIFs to our knowledge. Mn-Zn-ZIF still preserves the original properties of ZIF-8 of high surface areas, microporosity, and acid sensitivity. After further PEGylation of Mn-Zn-ZIF, the nanoparticles showed no obvious toxicity and its MRI contrast effect has also been enhanced. Our work highlights the promise of modified zeolitic imidazolate frameworks as potential cancer theranostic platforms.

Novel Intrapolymerization Doped Manganese-Eumelanin Coordination Nanocomposites with Ultrahigh Relaxivity and Their Application in Tumor Theranostics

While magnetic resonance imaging contrast agents have potential in noninvasive image-guided tumor treatment, further developments are needed to increase contrast, biodegradability, and safety. Here, novel engineered manganese-eumelanin coordination nanocomposites (MnEMNPs) are developed via a facile one-pot intrapolymerization doping (IPD) approach in aqueous solution, through simple chemical oxidation-polymerization of the 3,4-dihydroxy-DL-phenylalanine precursor with potassium permanganate serving as the Mn source and an oxidant. The resulting MnEMNPs possess ultrahigh longitudinal relaxivity (r1 value up to 60.8 mM-1 s-1 at 1.5 T) attributed to the high manganese doping efficiency (>10%) and geometrically confined conformation. Due to their high manganese chelation stability, excellent biocompatibility, and strong near-infrared absorption, high-performance longitudinal-transverse (T1-T2) dual-modal magnetic resonance/photoacoustic imaging and photothermal tumor ablation are achieved. Furthermore, the hydrogen peroxide-triggered decomposition behavior of MnEMNPs circumvents the poor biodegradation issue of many nanomaterials. This facile, convenient, economical, and efficient IPD strategy will open up new avenues for the development of high-performance multifunctional theranostic nanoplatforms in bionanomedicine.

Novel Intrapolymerization Doped Manganese-Eumelanin Coordination Nanocomposites with Ultrahigh Relaxivity and Their Application in Tumor Theranostics

While magnetic resonance imaging contrast agents have potential in noninvasive image-guided tumor treatment, further developments are needed to increase contrast, biodegradability, and safety. Here, novel engineered manganese-eumelanin coordination nanocomposites (MnEMNPs) are developed via a facile one-pot intrapolymerization doping (IPD) approach in aqueous solution, through simple chemical oxidation-polymerization of the 3,4-dihydroxy-DL-phenylalanine precursor with potassium permanganate serving as the Mn source and an oxidant. The resulting MnEMNPs possess ultrahigh longitudinal relaxivity (r₁ value up to 60.8 mM^-1 s^-1 at 1.5 T) attributed to the high manganese doping efficiency (>10%) and geometrically confined conformation. Due to their high manganese chelation stability, excellent biocompatibility, and strong near-infrared absorption, high-performance longitudinal-transverse (T₁-T₂) dual-modal magnetic resonance/photoacoustic imaging and photothermal tumor ablation are achieved. Furthermore, the hydrogen peroxide-triggered decomposition behavior of MnEMNPs circumvents the poor biodegradation issue of many nanomaterials. This facile, convenient, economical, and efficient IPD strategy will open up new avenues for the development of high-performance multifunctional theranostic nanoplatforms in bionanomedicine.

In Situ One-Pot Synthesis of MOF-Polydopamine Hybrid Nanogels with Enhanced Photothermal Effect for Targeted Cancer Therapy

Herein, a simple one-pot way is designed to prepare a type of multifunctional metal-organic framework (MOF)-based hybrid nanogels by in situ hybridization of dopamine monomer in the skeleton of MnCo. The resultant hybrid nanoparticles (named as MCP) show enhanced photothermal conversion efficiency in comparison with pure polydopamine or MnCo nanoparticles (NPs) synthesized under a similar method and, therefore, show great potential for photothermal therapy (PTT) in vivo. The MCP NPs are expected to possess T1 positive magnetic resonance imaging ability due to the high-spin Mn-N6 (S = 5/2) in the skeleton of MnCo. To improve the therapy efficiency as a PTT agent, the MCP NPs are further modified with functional polyethylene glycol (PEG) and thiol terminal cyclic arginine-glycine-aspartic acid peptide, respectively: the first one is to increase the stability, biocompatibility, and blood circulation time of MCP NPs in vivo; the second one is to increase the tumor accumulation of MCP-PEG NPs and improve their therapeutic efficiency as photothermal agent.

Bioinspired, Manganese-Chelated Alginate-Polydopamine Nanomaterials for Efficient in Vivo T1-Weighted Magnetic Resonance Imaging

Manganese-based nanomaterials are an emerging new class of magnetic resonance imaging (MRI) contrast agents (CAs) that provide impressive contrast abilities. MRI CAs that can respond to pathophysiological parameters such as pH or redox potential are also highly in demand for MRI-guided tumor diagnosis. Until now, synthesizing nanomaterials with good biocompatibility, physiochemical stability, and good contrast effects remains a challenge. This study investigated two new systems of calcium/manganese cations complexed with either alginate-polydopamine or alginate-dopamine nanogels [AlgPDA(Ca/Mn) NG or AlgDA(Ca/Mn) NG]. Under such systems, Ca cations form ionic interactions via carboxylic acids of the Alg backbone to enhance the stability of the synthetic nanogels (NGs). Likewise, complexation of Mn cations also increased the colloidal stability of the synthetic NGs. The magnetic property of the prepared CAs was confirmed with superconducting quantum interference device measurements, proving the potential paramagnetic property. Hence, the T₁ relaxivity measurement showed that PDA-complexed synthetic NGs reveal a strong positive contrast enhancement with r₁ = 12.54 mM^-1·s^-1 in 7.0 T MRI images, whereas DA-complexed synthetic NGs showed a relatively lower T₁ relaxivity effect with r₁ = 10.13 mM^-1·s^-1. In addition, both the synthetic NGs exhibit negligible cytotoxicity with >92% cell viability up to 0.25 mM concentration, when incubated with the mouse macrophage (RAW 264.7) and HeLa cells, and high biocompatibility under in vivo analysis. The in vivo MRI test indicates that the synthetic NG exhibits a high signal-to-noise ratio for longer hours, which provides a longer image acquisition time for tumor and anatomical imaging. Furthermore, T₁-weighted MRI results revealed that PEGylated AlgPDA(Ca/Mn) NGs significantly enhanced the signals from liver and tumor tissues. Therefore, owing to the enhanced permeability and retention effect, significantly enhanced in vitro and in vivo imagings, low cost, and one-pot synthesis method, the Mn-based biomimetic approach used in this study provides a promising and competitive alternative for noninvasive tumor detection and comprehensive anatomical diagnosis.

Novel Metal Polyphenol Framework for MR Imaging-Guided Photothermal Therapy

Phothermal therapy has received increasing attention in recent years as a potentially effective way to treat cancer. In pursuit of a more biocompatible photothermal agent, we utilize biosafe materials including ellagic acid (EA), polyvinylpyrrolidone (PVP), and iron element as building blocks, and we successfully fabricate a homogeneous nanosized Fe-EA framework for the first time by a facile method. As expected, the novel nanoagent exhibits no obvious cytotoxicity and good hemocompatibility in vitro and in vivo. The microenvironment responsiveness to both pH and hydrogen peroxide makes the NPs biodegradable in tumor tissues, and the framework should be easily cleared by the body. Photothermal potentials of the nanoparticles are demonstrated with relevant features of strong NIR light absorption, moderately effective photothermal conversion efficiency, and good photothermal stability. The in vivo photothermal therapy also achieved effective tumor ablation with no apparent toxicity. On the other hand, it also exhibits T2 MR imaging ability originated from ferric ions. Our work highlights the promise of the Fe-EA framework for imaging-guided photothermal therapy.

Preparation of highly dispersed γ-Fe2O3 and GdPO4 co-functionalized mesoporous carbon spheres for dual-mode MR imaging and anti-cancer drug carrying

Dual-mode MR imaging and drug carrying properties have been integrated into carbon nanospheres by using Wells–Dawson like clusters.

Au@MnS@ZnS Core/Shell/Shell Nanoparticles for Magnetic Resonance Imaging and Enhanced Cancer Radiation Therapy

Although conventional radiotherapy (RT) has been widely used in the clinic to treat cancer, it often has limited therapeutic outcomes and severe toxic effects. There is still a need to develop theranostic agents with both imaging and RT-enhancing functions to improve the accuracy and efficiency of RT. Herein we synthesize Au@MnS@ZnS core/shell/shell nanoparticles with polyethylene glycol (PEG) functionalization, yielding Au@MnS@ZnS-PEG nanoparticles with great stability in different physiological solutions and no significant cytotoxicity. It is found that Au@MnS@ZnS-PEG nanoparticles can enhance the cancer cell killing efficiency induced by RT, as evidenced by multiple in vitro assays. Owing to the existence of paramagnetic Mn(2+) in the nanoparticle shell, our Au@MnS@ZnS-PEG can be used as a contrast agent for T1-weighted magnetic resonance (MR) imaging, which reveals the efficient accumulation and retention of nanoparticles in the tumors of mice after intravenous injection. Importantly, by exposing tumor-bearing mice that were injected with Au@MnS@ZnS-PEG to X-ray irradiation, the tumor growth can be significantly inhibited. This result shows clearly improved therapeutic efficacy compared to RT alone. Furthermore, no obvious side effect of Au@MnS@ZnS-PEG is observed in the injected mice. Therefore, our work presents a new type of radiosensitizing agent, which is promising for the imaging-guided enhanced RT treatment of cancer.

Copper Prussian blue analogue: investigation into multifunctional activities for biomedical applications

We have designed and developed stable and biocompatible copper analogues of a Prussian blue (PB) nanoparticle based drug delivery system containing doxorubicin that show selective quenching of fluorescence of doxorubicin compared to PB analogues with other metals and inhibition of cancer cell proliferation, suggesting future potential multifunctional applications in biomedical sciences.

A copper hexacyanocobaltate nanocubes based dopamine sensor in the presence of ascorbic acid

A highly selective and sensitive dopamine sensor was demonstrated based on copper hexacyanocobaltate nanocubes in the presence of ascorbic acid.

Magnetic and fluorescent carbon-based nanohybrids for multi-modal imaging and magnetic field/NIR light responsive drug carriers

This mini-review summarizes the latest developments and addresses the future perspectives of carbon-based magnetic and fluorescent nanohybrids in the biomedical field.

Novel Mn3 [Co(CN)6]2@SiO2@Ag Core-Shell Nanocube: Enhanced Two-Photon Fluorescence and Magnetic Resonance Dual-Modal Imaging-Guided Photothermal and Chemo-therapy

The versatile Mn3[Co(CN)6]2@SiO2@Ag core-shell NCs are prepared by a simple coprecipitation method. Ag nanoparticles with an average diameter of 12 nm deposited on the surface of Mn3[Co(CN)6]2@SiO2 through S-Ag bonding are fabricated in ethanol solution by reducing silver nitrate (AgNO3 ) with NaBH4 . The NCs possess T1 -T2 dual-modal magnetic resonance imaging ability. The inner Prussian blue analogs (PBAs) Mn3[Co(CN)6]2 exhibit bright two-photon fluorescence (TPF) imaging when excited at 730 nm. Moreover, the TPF imaging intensity displays 1.85-fold enhancement after loading of Ag nanoparticles. Besides, the sample also has multicolor fluorescence imaging ability under 403, 488, and 543 nm single photon excitation. The as-synthesized Mn3[Co(CN)6]2@SiO2@Ag NCs show a DOX loading capacity of 600 mg g(-1) and exhibit an excellent ability of near-infrared (NIR)-responsive drug release and photothermal therapy (PTT) which is induced from the relative high absorbance in NIR region. The combined chemotherapy and PTT against cancer cells in vitro test shows high therapeutic efficiency. The multimodal treatment and imaging could lead to this material a potential multifunctional system for biomedical diagnosis and therapy.

One-Pot Hydrothermal Synthesis of FeMoO₄ Nanocubes as an Anode Material for Lithium-Ion Batteries with Excellent Electrochemical Performance

Metal molybdates nanostructures hold great promise as high-performance electrode materials for next-generation lithium-ion batteries. In this work, the facial design and synthesis of monodisperse FeMoO4 nanocubes with the edge lengths of about 100 nm have been successfully prepared and present as a novel anode material for highly efficient and reversible lithium storage. Well-defined single-crystalline FeMoO4 with high uniformity are first obtained as nanosheets and then self-aggregated into nanocubes. The morphology of the product is largely controlled by the experimental parameters, such as the reaction temperature and time, the ratio of reactant, the solution viscosity, etc. The molybdate nanostructure would effectively promote the insertion of lithium ions and withstand volume variation upon prolonged charge/discharge cycling. As a result, the FeMoO4 nanocubes exhibit high reversible capacities of 926 mAh g(-1) after 80 cycles at a current density of 100 mA g(-1) and remarkable rate performance, which indicate that the FeMoO4 nanocubes are promising materials for high-power lithium-ion battery applications.

Au@Ag core-shell nanocubes: epitaxial growth synthesis and surface-enhanced Raman scattering performance

Novel Au@Ag core-shell nanocubes (NCs) were successfully prepared by the controlled epitaxial growth of Ag shells onto Au nanoellipsoids (NEs) in the presence of surfactants. The growth mechanism of the Au@Ag core-shell NCs was systematically investigated by analyzing their morphology, optical properties, and crystallography. The localized surface plasmon resonance (LSPR) characteristics and the electric field distribution of the Au@Ag core-shell NCs were studied using the finite element method (FEM) based on the plasmon hybridization theory. Compared with pure Ag NCs, the absorption spectrum of the Au@Ag core-shell NCs exhibits a red shift and a weak shoulder near 550 nm, and the notable enhancement of electric field occurs around the corners along the long-axis of the Au ellipsoidal core because of plasmonic resonant coupling. Surface-enhanced Raman scattering (SERS) of the Au@Ag core-shell NCs labeled with 4-mercaptobenzoic acid molecules reveals that the bimetallic core-shell NCs possess efficient SERS activity with an enhancement factor EF = 2.27 × 10(6), thus confirming the possibility of using the Au@Ag core-shell NCs as a stable probe for SERS-based biosensing applications.

Nanoparticles for multimodal in vivo imaging in nanomedicine

While nanoparticles are usually designed for targeted drug delivery, they can also simultaneously provide diagnostic information by a variety of in vivo imaging methods. These diagnostic capabilities make use of specific properties of nanoparticle core materials. Near-infrared fluorescent probes provide optical detection of cells targeted by real-time nanoparticle-distribution studies within the organ compartments of live, anesthetized animals. By combining different imaging modalities, we can start with deep-body imaging by magnetic resonance imaging or computed tomography, and by using optical imaging, get down to the resolution required for real-time fluorescence-guided surgery.