Self‐Assembled Nanomicelles as MRI Blood‐Pool Contrast Agent

Abstract

Gadolinium-loaded nanomicelles show promise as future magnetic resonance imaging (MRI) contrast agents (CAs). Their increased size and high gadolinium (Gd) loading gives them an edge in proton relaxivity over smaller molecular Gd-complexes. Their size and stealth properties are fundamental for their long blood residence time, opening the possibility for use as blood-pool contrast agents. Using l-tyrosine as a three-functional scaffold we synthesized a nanostructure building block 8. The double C18 aliphatic chain on one side, Gd-1,4,7,10-tetraazacyclododecane-1-4-7-triacetic acid (Gd-DO3A) with access to bulk water in the center and 2 kDa PEG on the hydrophilic side gave the amphiphilic properties required for the core-shell nanomicellar architecture. The self-assembly into Gd-loaded monodispersed 10-20 nm nanomicelles occurred spontaneously in water. These nanomicelles (Tyr-MRI) display very high relaxivity at 29 mm s at low field strength and low cytotoxicity. Good contrast enhancement of the blood vessels and the heart together with prolonged circulation time in vivo, makes Tyr-MRI an excellent candidate for a new supramolecular blood-pool MRI CA.

PEGylated amphiphilic polymeric manganese(ii) complexes as magnetic resonance angiographic agents

“…A T 1 contrast agent can significantly shorten the T 1 relaxation time of protons surrounding it, resulting in the effect of enhancing the contrast of tissue images of the body. 42,46 In this work, small molecule (MnL) and mPEG 2k -P(MnL-a-HMDI)-mPEG 2k micelles Mn(II) complexes were selected for contrast enhanced magnetic resonance angiography (MRA) of SD rats on a clinical 3.0 T MR scanner. Fig.…”

Synthesis of a Thermal‐Responsive Dual‐Modal Supramolecular Probe for Magnetic Resonance Imaging and Fluorescence Imaging

“…[ 34–36 ] For the small molecule CAs, they can be easily cleared by kidney and exhibit a low relaxation rate. [ 37,38 ] In order to achieve the effect of MRI, the dose of the small molecule CAs need to be increased, which will cause nephrotoxicity. [ 39–42 ] As reported by Ling et al, small molecule aggregation or self‐assembled micelle seems to be able to solve the above problems.…”

Cyclodextrins: promising scaffolds for MRI contrast agents

“…This time s m is dependent on the exchange mechanism, the steric hindrance, and the rigidity of the ligand, as well as the overall charge of the complex. The increase in correlation time and reduction of the rate of rotation of the complex can be obtained by the use of supramolecular molecules such as polymers, [19][20][21] dendrimers, [22][23][24] micelles, [25][26][27][28] proteins, [29][30][31][32] or nanoparticles. [33][34][35] Moreover, an excessive exchange can limit the contact between the nuclear spin of the proton and the electronic spin of the metal and can also lead to a decrease in relaxivity.…”