Dual-modality and Noninvasive Diagnostic of MNP-PEG-Mn Nanoprobe for Renal Fibrosis Based on Photoacoustic and Magnetic Resonance Imaging

The Recent Applications of Magnetic Nanoparticles in Biomedical Fields

Magnetic nanoparticles (MNPs) have found extensive application in the biomedical domain due to their enhanced biocompatibility, minimal toxicity, and strong magnetic responsiveness. MNPs exhibit great potential as nanomaterials in various biomedical applications, including disease detection and cancer therapy. Typically, MNPs consist of a magnetic core surrounded by surface modification coatings, such as inorganic materials, organic molecules, and polymers, forming a nucleoshell structure that mitigates nanoparticle agglomeration and enhances targeting capabilities. Consequently, MNPs exhibit magnetic responsiveness in vivo for transportation and therapeutic effects, such as enhancing medical imaging resolution and localized heating at the site of injury. MNPs are utilized for specimen purification through targeted binding and magnetic separation in vitro, thereby optimizing efficiency and expediting the process. This review delves into the distinctive functional characteristics of MNPs as well as the diverse bioactive molecules employed in their surface coatings and their corresponding functionalities. Additionally, the advancement of MNPs in various applications is outlined. Additionally, we discuss the advancements of magnetic nanoparticles in medical imaging, disease treatment, and in vitro assays, and we anticipate the future development prospects and obstacles in this field. The objective is to furnish readers with a thorough comprehension of the recent practical utilization of MNPs in biomedical disciplines.

Controllable synthesis of barium carbonate nano- and microparticles for SPECT and CT imaging

The design and synthesis of nano- and microcarriers for preclinical and clinical imaging are highly attractive due to their unique features, for example, multimodal properties. However, broad translation of these carriers into clinical practice is postponed due to the unknown biological reactivity of the new components used for their synthesis. Here, we have developed microcarriers (∼2-3 μm) and  nanocarriers (<200 nm) made of barium carbonate (BaCO3) for multiple imaging applications in vivo. In general, barium in the developed carriers can be used for X-ray computed tomography, and the introduction of a diagnostic isotope (99mTc) into the BaCO3 structure enables in vivo visualization using single-photon emission computed tomography. The bioimaging has shown that the radiolabeled BaCO3 nano- and microcarriers had different biodistribution profiles and tumor accumulation efficiencies after intratumoral and intravenous injections. In particular, in the case of intratumoral injection, all the types of used carriers mostly remained in the tumors (>97%). For intravenous injection, BaCO3 microcarriers were mainly localized in the lung tissues. However, BaCO3 NPs were mainly accumulated in the liver. These results were supported by ex vivo fluorescence imaging, direct radiometry, and histological analysis. The BaCO3-based micro- and nanocarriers showed negligible in vivo toxicity towards major organs such as the heart, lungs, liver, kidneys, and spleen. This study provides a simple strategy for the design and fabrication of the BaCO3-based carriers for the development of dual bioimaging.

Highly Sensitive Early Diagnosis of Kidney Damage Using Renal Clearable Zwitterion-Coated Ferrite Nanoprobe via Magnetic Resonance Imaging In Vivo

Iron oxide nanoprobes exhibit substantial potential in magnetic resonance imaging (MRI) of kidney diseases and can eliminate the nephrotoxicity of gadolinium-based contrast agents (GBCAs). Nevertheless, there is an extreme shortage of highly sensitive and renal clearable iron oxide nanoprobes suitable for early kidney damage detection through MRI. Herein, a renal clearable ultra-small ferrite nanoprobe (UMFNPs@ZDS) is proposed for highly sensitive early diagnosis of kidney damage via structural and functional MRI in vivo for the first time. The nanoprobe comprises a ferrite core coated with a zwitterionic layer, and possesses a high T1 relaxivity (12.52 mm-1s-1), a small hydrodynamic size (6.43 nm), remarkable water solubility, excellent biocompatibility, and impressive renal clearable ability. In a rat model of unilateral ureteral obstruction (UUO), the nanoprobe-based MRI can not only accurately visualize the locations of renal injury, but also provide comprehensive functional data including peak value, peak time, relative renal function (RRF), and clearance percentage via MRI. The findings prove the immense potential of ferrite nanoprobes as a superior alternative to GBCAs for the early diagnosis of kidney damage.

Purification-free synthesis of bright lactoglobulin@dye nanoprobe for second near-infrared fluorescence imaging of kidney dysfunction in vivo

Kidney disease is currently prevalent worldwide but only shows insidious symptoms in the early stages. The second near-infrared window (NIR-II) fluorescence imaging has become a widely used preclinical technology for evaluating renal dysfunction due to its high resolution and sensitivity. However, bright renal clearable NIR-II fluorescence nanoprobes with a simple synthesis process are still lacking. Herein, we develop a lactoglobulin (LG)@dye nanoprobe for NIR-II fluorescence imaging of kidney dysfunction in vivo based on a purification-free method. The nanoprobe was synthesized by simply mixing LG and IR820 in aqueous solutions at 70 °C for 2 h based on the covalent interaction between the meso-Cl in IR820 and LG. The synthesized LG@IR820 nanoprobe has bright and stable NIR-II fluorescence, ultra-small size (<5 nm), low toxicity, and renal-clearable ability. The high reaction efficiency and pure aqueous reaction media make the synthesis method purification-free. In a unilateral ureteral obstruction mouse model, incipient renal dysfunction assessment was achieved by LG@IR820 nanoprobe, which couldn't be diagnosed with conventional kidney function indicators. This study provides a bright and purification-free NIR-II LG@IR820 nanoprobe to visualize kidney dysfunction at the early stage.

Platelet Membrane-Encapsulated Nanocomplexes Based on Profundity Scavenging ROS Strategy for Myocardial Infarction Therapy

Ischemia-induced myocardial injury has become a serious threat to human health, and its treatment remains a challenge. The occurrence of ischemic events leads to a burst release of reactive oxygen species (ROS), which triggers extensive oxidative damage and leads to dysfunctional autophagy, making it difficult for cells to maintain homeostasis. Antioxidants and modulation of autophagy have thus become promising strategies for the treatment of ischemic myocardial injury. This study proposes an antioxidant-activated autophagy therapeutic regimen based on combining melanin (Mel), an excellent antioxidant with metformin mimetic ploymetformin via electrostatic interactions, to obtain a nanocomplex (Met-Mel). The nanocomplex is finally encapsulated with platelet membranes (PMN) to construct a biomimetic nanoparticle (PMN@Met-Mel) capable of targeting injured myocardium. The prepared PMN@Met-Mel has good Mel loading capacity and optimal biosafety. It exhibits excellent antioxidant activity and autophagy activation, rapidly restoring mitochondrial function. Moreover, RNA sequencing (RNA-seq) analysis reveals that PMN@Met-Mel operates mechanistically by triggering the activation of the autophagy pathway. Subsequent in vivo experiments showcase promising cardioprotective effects of these nanoparticles. These discoveries present a newly devised nanoplatform with promising potential for the effective treatment of myocardial infarction.

Noninvasive Diagnosis of Kidney Dysfunction Using a Small-Molecule Manganese-Based Magnetic Resonance Imaging Probe

Contrast-enhanced magnetic resonance imaging (CE-MRI) is a promising approach for the diagnosis of kidney diseases. However, safety concerns, including nephrogenic systemic fibrosis, limit the administration of gadolinium (Gd)-based contrast agents (GBCAs) in patients who suffer from renal impairment. Meanwhile, nanomaterials meet biosafety concerns because of their long-term retention in the body. Herein, we propose a small-molecule manganese-based imaging probe Mn-PhDTA as an alternative to GBCAs to assess renal insufficiency for the first time. Mn-PhDTA was synthesized via a simple three-step reaction with a total yield of up to 33.6%, and a gram-scale synthesis can be realized. Mn-PhDTA has an r1 relaxivity of 2.72 mM-1 s-1 at 3.0 T and superior kinetic inertness over Gd-DTPA and Mn-EDTA with a dissociation time of 60 min in the presence of excess Zn2+. In vivo and in vitro experiments demonstrate their good stability and biocompatibility. In the unilateral ureteral obstruction rats, Mn-PhDTA provided significant MR signal enhancement, enabled distinguishing structure changes between the normal and damaged kidneys, and evaluated the renal function at different injured stages. Mn-PhDTA could act as a potential MRI contrast agent candidate for the replacement of GBCAs in the early detection of kidney dysfunction and analysis of kidney disease progression.

Bioinspired BSA@polydopamine@Fe Nanoprobe with Self-Purification Capacity for Targeted Magnetic Resonance Imaging of Acute Kidney Injury

Contrast-enhanced magnetic resonance imaging (CE-MRI) of acute kidney injury (AKI) is severely hindered by the poor targeting capacity and potential toxicity of current contrast agents. Herein, we propose one-step fabrication of a bovine serum albumin@polydopamine@Fe (BSA@PDA@Fe, BPFe) nanoprobe with self-purification capacity for targeted CE-MRI of AKI. BSA endows the BPFe nanoprobe with renal tubule-targeting ability, and PDA is capable of completely inhibiting the intrinsic metal-induced reactive oxygen species (ROS), which are always involved in Fe/Mn-based agents. The as-prepared nanoprobe owns a tiny size of 2.7 nm, excellent solubility, good T1 MRI ability, superior biocompatibility, and powerful antioxidant capacity. In vivo CE-MRI shows that the BPFe nanoprobe can accumulate in the renal cortex due to the reabsorption effect toward the serum albumin. In the AKI model, impaired renal reabsorption function can be effortlessly detected via the diminishment of renal cortical signal enhancement. More importantly, the administration of the BPFe nanoprobe would not aggravate renal damage of AKI due to the outstanding self-purification capacity. Besides, the BPFe nanoprobe is employed for CE-MR angiography to visualize fine vessel structures. This work provides an MRI contrast agent with good biosafety and targeting ability for CE-MRI of kidney diseases.

Noninvasive Assessment of Kidney Injury by Combining Structure and Function Using Artificial Intelligence-Based Manganese-Enhanced Magnetic Resonance Imaging

Contrast-enhanced magnetic resonance imaging (MRI) is seriously limited in kidney injury detection due to the nephrotoxicity of clinically used gadolinium-based contrast agents. Herein, we propose a noninvasive method for the assessment of kidney injury by combining structure and function information based on manganese (Mn)-enhanced MRI for the first time. As a proof of concept, the Mn-melanin nanoprobe with good biocompatibility and excellent T1 relaxivity is applied in MRI of a unilateral ureteral obstruction mice model. The abundant renal structure and function information is obtained through qualitative and quantitative analysis of MR images, and a brand new comprehensive assessment framework is proposed to precisely identify the degree of kidney injury successfully. Our study demonstrates that Mn-enhanced MRI is a promising approach for the highly sensitive and biosafe assessment of kidney injury in vivo.

Amide Proton Transfer-Weighted Magnetic Resonance Imaging for Application in Renal Fibrosis: A Radiological-Pathological-Based Analysis

INTRODUCTION

Renal fibrosis (RF), being the most important pathological change in the progression of CKD, is currently assessed by the evaluation of a biopsy. This present study aimed to apply a novel functional MRI (fMRI) protocol named amide proton transfer (APT) weighting to evaluate RF noninvasively.

METHODS

Male Sprague-Dawley (SD) rats were initially subjected to bilateral kidney ischemia/reperfusion injury (IRI), unilateral ureteral obstruction, and sham operation, respectively. All rats underwent APT mapping on the 7th and 14th days after operation. Besides, 26 patients underwent renal biopsy at the Nephrology Department of Shanghai Tongji Hospital between July 2022 and May 2023. Patients underwent APT and apparent diffusion coefficient (ADC) mappings within 1 week before biopsy. MRI results of both patients and rats were calculated by comparing with gold standard histology for fibrosis assessment.

RESULTS

In animal models, the cortical APT (cAPT) and medullary APT (mAPT) values were positively correlated with the degree of RF. Compared to the sham group, IRI group showed significantly increased cAPT and mAPT values on the 7th and 14th days after surgery, but no group differences were found in ADC values. Similar results were found in human patients. Cortical/medullary APT values were significantly increased in patients with moderate-to-severe fibrosis than in patients with mild fibrosis. ROC curve analysis indicated that APT value displayed a better diagnostic value for RF. Furthermore, combination of cADC and cAPT improved fibrosis detection by imaging variables alone (p < 0.1).

CONCLUSION

APT values had better diagnostic capability at early stage of RF compared to ADC values, and the addition of APT imaging to conventional ADC will significantly improve the diagnostic performance for predicting kidney fibrosis.