Preparation and performance of biocompatible gadolinium polymer as liver-targeting magnetic resonance imaging contrast agent

A biocompatible macromolecule-conjugated gadolinium chelate complex (PAV2-EDA-DOTA-Gd) as a new liver-specific contrast agent for magnetic resonance imaging (MRI) was synthesized and evaluated. An aspartic acid-valine copolymer was used as a carrier and ethylenediamine as a chemical linker, and the aspartic acid-valine copolymer was covalently linked to the small molecule MRI contrast agent Gd-DOTA (Dotarem) to synthesize a large molecule contrast agent. In vitro MR relaxation showed that the T1-relaxivity of PAV2-EDA-DOTA-Gd (13.7 mmol-1 L s-1) was much higher than that of the small-molecule Gd-DOTA (4.9 mmol-1 L s-1). In vivo imaging of rats showed that the enhancement effect of PAV2-EDA-DOTA-Gd (55.37 ± 2.80%) on liver imaging was 2.6 times that of Gd-DOTA (21.12 ± 3.86%), and it produced a longer imaging window time (40-70 min for PAV2-EDA-DOTA-Gd and 10-30 min for Gd-DOTA). Preliminary safety experiments, such as cell experiments and tissue sectioning, showed that PAV2-EDA-DOTA-Gd had low toxicity and satisfactory biocompatibility. The results of this study indicated that PAV2-EDA-DOTA-Gd had high potential as a liver-specific MRI contrast agent.

Tumor microenvironment-responsive histidine modified-hyaluronic acid-based MnO2 as in vivo MRI contrast agent

Tumor microenvironment (TME)-responsive manganese dioxide (MnO₂) nanoparticles as a good T₁ contrast agent could reduce unwanted toxicity and improve the accuracy of cancer detection. Despite these distinct advantages of MnO₂-based nanoparticles, their synthesis involves multi-step processes with relatively long synthesis times. In this study, we synthesized histidine-modified hyaluronic acid (HA-His), and the prepared HA-His conjugates quickly reduce permanganate to MnO₂, leading to facile production of HA-His/MnO₂ nanoparticles with good water-dispersibility and stability under biological conditions. The synthesized HA-His/MnO₂ nanoparticles readily responded to the TME (low pH, high H₂O₂, and high glutathione), and they were internalized into SCC7 cells with high CD44 expression. Moreover, the systemically administered HA-His/MnO₂ nanoparticles with biocompatibility were specifically accumulated in tumor tissues, thereby efficiently enhancing T₁ contrast in MRI. Therefore, the HA-His/MnO₂ nanoparticles synthesized herein can be used as a promising T₁ contrast agent for tumor MR imaging.

Stimuli-responsive poly(N-isopropyl acrylamide)-co-tyrosine@gadolinium: Iron oxide nanoparticle-based nanotheranostic for cancer diagnosis and treatment

In this paper, we have prepared a stimuli-responsive polymer modified gadolinium doped iron oxide nanoparticle (poly@Gd-MNPs) as cancer theranostic agent. The responsive polymer is composed of the poly(N-isopropyl acrylamide)-co-tyrosine unit, which shows excellent loading for the anti-cancer drug (methotrexate) and stimuli dependent release (change in pH and temperature). The in vitro experiment revealed that the poly@Gd-MNPs exhibited T1-weighted MRI capability (r1=11.314mM(-1)s(-1)) with good in-vitro hyperthermia response. The prepared poly@Gd-MNPs has generated quick heating (45°C in 2min) upon exposure to an alternating magnetic field and able to travel a distance of 35cm in 1min in the presence of an external magnet. The poly@Gd-MNPs shows 86% of drug loading capacity with 70% drug release in first 2h. The cytotoxic assay (MTT) demonstrated that the nanoparticle did not affect the viability of normal human fibroblast and efficiently kill the MCF7 cancer cells in the presence of an external magnetic field. To explore the uptake of poly@Gd-MNPs in the cells, bright field cell imaging study was also performed. This study provides a valuable approach for the design of highly sensitive polymer modified gadolinium doped iron oxide-based T1 contrast agents for cancer theranostics.