Periodic table screening for enhanced positive contrast in MRI and in vivo uptake in glioblastoma

The quest for nanomaterial-based imaging probes that can provide positive contrast in MRI is fueled by the necessity of developing novel diagnostic applications with potential for clinical translation that current gold standard probes cannot provide. Although interest in nanomaterials for positive contrast has increased in recent years, their study is less developed than that of traditional negative contrast probes in MRI. In our search for new magnetic materials with enhanced features as positive contrast probes for MRI, we decided to explore the chemical space to comprehensively analyze the effects of different metals on the performance of iron oxide nanomaterials already able to provide positive contrast in MRI. To this end, we synthesized 30 different iron oxide-based nanomaterials. Thorough characterization was performed, including multivariate analysis, to study the effect of different variables on their relaxometric properties. Based on these results, we identified the best combination of metals for in vivo imaging and tested them in different experiments. First, we tested its performance on magnetic resonance angiography using a concentration ten times lower than that clinically approved for Gd. Finally, we studied the capability of these nanomaterials to cross the affected blood-brain barrier in a glioblastoma model. The results showed that the selected nanomaterials provided excellent positive contrast at large magnetic field and were able to accumulate at the tumor site, highlighting the affected tissue.

Direct large-scale synthesis of water-soluble and biocompatible upconversion nanoparticles for in vivo imaging

Deep tissues can be optically imaged using near-infrared windows without radiation hazard. This work proposes a straightforward one-pot method for directly synthesizing water-soluble and biocompatible upconversion nanoparticles on a large scale for in vivo imaging. Safety assessment, coupled with luminescence imaging in mice, demonstrates the excellent stability and promising biological applications of the upconversion nanoparticles.

A Targeted Multi-Crystalline Manganese Oxide as a Tumor-Selective Nano-Sized MRI Contrast Agent for Early and Accurate Diagnosis of Tumors

Introduction

Magnetic resonance imaging (MRI) is an important tool for the accurate diagnosis of malignant tumors in clinical settings. However, the lack of tumor-specific MRI contrast agents limits diagnostic accuracy.

Methods

Herein, we developed αv integrin receptor-targeting multi-crystalline manganese oxide (MCMO) as a novel MRI contrast agent for accurate diagnosis of tumors by coupling iRGD cyclopeptide PEGylation polymer onto the surface of MCMO (iRGD-pMCMO).

Results

The MCMO consisted of numerous small crystals and exhibited an oval structure of 200 nm in size. The iRGD-pMCMO actively recognizes tumor cells and effectively accumulates at the tumor site, consequently releasing abundant Mn2+ ions in a weakly acidic and high-GSH-expressing tumor microenvironment. Subsequently, Mn2+ ions interact with cellular GSH to form Mn-GSH chelates, enabling efficient T1-weighted MR contrast imaging. In vivo experiments indicated that iRGD-pMCMO significantly improved T1-weighted images, achieving an accurate diagnosis of subcutaneous and orthotopic tumors. The results verified that the T1 contrast effect of iRGD-pMCMO was closely associated with the expression of GSH in tumor cells.

Conclusion

Altogether, the novel tumor-targeting, highly sensitive MRI contrast agent developed in this study can improve the accuracy of MRI for tumor diagnosis.

The Promise of Metal-Doped Iron Oxide Nanoparticles as Antimicrobial Agent

Antibiotic resistance (AMR) is one of the pressing global public health concerns and projections indicate a potential 10 million fatalities by the year 2050. The decreasing effectiveness of commercially available antibiotics due to the drug resistance phenomenon has spurred research efforts to develop potent and safe antimicrobial agents. Iron oxide nanoparticles (IONPs), especially when doped with metals, have emerged as a promising avenue for combating microbial infections. Like IONPs, the antimicrobial activities of doped-IONPs are also linked to their surface charge, size, and shape. Doping metals on nanoparticles can alter the size and magnetic properties by reducing the energy band gap and combining electronic charges with spins. Furthermore, smaller metal-doped nanoparticles tend to exhibit enhanced antimicrobial activity due to their higher surface-to-volume ratio, facilitating greater interaction with bacterial cells. Moreover, metal doping can also lead to increased charge density in magnetic nanoparticles and thereby elevate reactive oxygen species (ROS) generation. These ROS play a vital role to disrupt bacterial cell membrane, proteins, or nucleic acids. In this review, we compared the antimicrobial activities of different doped-IONPs, elucidated their mechanism(s), and put forth opinions for improved biocompatibility.

Large-scale in situ self-assembly and doping engineering of zinc ferrite nanoclusters for high performance bioimaging

Iron oxide nanomaterials has good biocompatibility and safety, and has been used as contrast agents for magnetic resonance imaging (MRI). However, its clinical usefulness is hampered by its difficult preparation on large scale, its rapid clearance in vivo and low target tissue enrichment efficiency. Here, we report the synthesis of water-soluble, biocompatible, superparamagnetic non-stoichiometric zinc ferrite nanoclusters (nZFNCs) of approximately 50 g in a single batch using a one-pot synthesis technique. nZFNCs is a secondary cluster structure with a size of about 40 nm composed of zinc-doped iron oxide nanoparticles with a size of about 6 nm. The surface of nZFNCS is endowed with a large number of carboxyl groups as active sites. By simply controlling the synthesis process and adjusting the proportion of metal precursors, the amount of zinc doping can be controlled, while maintaining the same size to ensure similar pharmacokinetics. Compared with undoped, the magnetic responsiveness and relaxation efficiency of nZFNCs are significantly improved, and the transverse relaxation efficiency (r2) can reach 425.5 mM-1 s-1 (doping amount x = 0.25), which is 7 times higher than that of commercial Resovist and 10 times higher than that of Feridex. In vivo imaging results also further confirmed the excellent contrast enhancement performance of the nanoclusters, which can achieve high contrast for more than 2 h in the liver. The advantage of this platform over comparable systems is that the contrast enhancement features are derived from simple techniques that do not require complex physical and chemical methods.

Nickel sulfide and dysprosium-doped nickel sulfide nanoparticles: Dysprosium-induced variation in properties, in vitro chemo-photothermal behavior, and antibacterial activity

Newer materials for utilization in multi-directional therapeutic actions are investigated, considering delicate design principles involving size and shape control, surface modification, and controllable drug loading and release. Multi-faceted properties are imparted to the engineered nanoparticles, like magnetism, near-infrared absorption, photothermal efficiency, and suitable size and shape. This report presents nickel sulfide and dysprosium-doped nickel sulfide nanoparticles with poly-β-cyclodextrin polymer coating. The nanoparticles belong to the orthorhombic crystal systems, as indicated by X-ray diffraction studies. The size and shape of the nanoparticles are investigated using Transmission Electron Microscope (TEM) and a particle-size analyzer. The particles show soft ferromagnetic characteristics with definite and moderate saturation magnetization values. The nickel sulfide nanoparticles' in vitro anticancer and antibacterial activities are investigated in free and 5-fluorouracil/penicillin benzathine-loaded forms. The 5-fluorouracil-encapsulation efficiency of the nanoparticles is around 87%, whereas it is above 92% in the case of penicillin benzathine. Both drugs are released slowly in a controlled fashion. The dysprosium-doped nickel sulfide nanoparticles show better anticancer activity, and the efficacy is more significant than the free drug. The nanoparticles are irradiated with a low-power 808 nm laser. The dysprosium-doped nickel sulfide nanoparticles attain a higher temperature on irradiation, i.e., above 59 °C. The photothermal conversion efficiency of this material is determined, and the significance of dysprosium doping is discussed. Contrarily, the undoped nickel sulfide nanoparticles show more significant antibacterial activity. This study presents a novel designed nanoparticle system and the exciting variation of properties on dysprosium doping in nickel sulfide nanoparticles.

Preclinical Evaluation of a Protein-Based Nanoscale Contrast Agent for MR Angiography at an Ultralow Dose

PURPOSE

BSA-biomineralized Gd nanoparticles (Gd@BSA NPs) have been recognized as promising nanoscale MR contrast agents. The aim of this study was to carry out a preclinical evaluation of these NPs in a middle-sized animal model (rabbits).

METHODS

New Zealand white rabbits were treated intravenously with Gd@BSA NPs (0.02 mmol Gd/kg) via a clinically-used high-pressure injector, with commercial Gd-diethylene triamine pentaacetate (Gd-DTPA)-injected group as control. Then MR angiography was performed according to the standard clinical protocol with a 3.0-T MR scanner. The SNR and CNR of the main arteries and branches were monitored. Pharmacokinetics and bioclearance were continuously evaluated in blood, urine, and feces. Gd deposition in vital organs was measured by ICP‒MS. Weight monitoring, HE staining, and blood biochemical analysis were also performed to comprehensively estimate systemic toxicity.

RESULTS

The ultrasmall Gd@BSA NPs (<6 nm) exhibited high stability and T1 relaxivity. Compared to Gd-DTPA, Gd@BSA NPs demonstrated superior vascular system imaging performance at ultralow doses, especially of the cardiac artery and other main branches, and exhibited a significantly higher SNR and CNR. Notably, the Gd@BSA NPs showed a shorter half-life in blood, less retention in organs, and improved biocompatibility.

CONCLUSION

The preclinical evaluations here demonstrated that Gd@BSA NPs are promising and advantageous MR CA candidates that can be used at a low dose with excellent MR imaging performance, thus suggesting its further clinical trials and applications.

Single-Atom Gd Nanoprobes for Self-Confirmative MRI with Robust Stability

Gadolinium (Gd)-based complexes are extensively utilized as contrast agents (CAs) in magnetic resonance imaging (MRI), yet, suffer from potential safety concerns and poor tumor targeting. Herein, as a mimic of Gd complex, single-atom Gd nanoprobes with r₁ and r₂ values of 34.2 and 80.1 mM^-1 s^-1 (far higher than that of commercial Gd CAs) at 3 T are constructed, which possessed T₁ /T₂ dual-mode MRI with excellent stability and good tumor targeting ability. Specifically, single-atom Gd is anchored on nitrogen-doped carbon matrix (Gd-N_x C) through spatial-confinement method, which is further subjected to controllable chemical etching to afford fully etched bowl-shape Gd-N_x C (feGd-N_x C) with hydrophilic properties and defined coordination structure, similar to commercial Gd complex. Such nanostructures not only maximized the Gd³⁺ site exposure, but also are suitable for self-confirmative diagnosis through one probe with dual-mode MRI. Moreover, the strong electron localization and interaction between Gd and N atoms afforded feGd-N_x C excellent kinetic inertness and thermal stability (no significant Gd³⁺ leaching is observed even incubated with Cu²⁺ and Zn²⁺ for two months), providing a creative design protocol for MRI CAs.