Filterable Agents for Hyperpolarization of Water,Metabolites, and Proteins

Hyperpolarization is generated by dissolution dynamic nuclear polarization (d‐DNP) using a polymer‐based polarizing agent dubbed FLAP (filterable labeled agents for polarization). It consists of a thermo‐responsive poly(N‐isopropylacrylamide), also known as pNiPAM‐COOH, labeled with nitroxide radicals. The polymer powder is impregnated with an arbitrary solution of interest and frozen as is. Dissolution is followed by a simple filtration, leading to hyperpolarized solutions free from any contaminants. We demonstrated the use of FLAP to hyperpolarize partially deuterated water up to P(¹H)=6 % with a long relaxation T₁ >36 s characteristic of high purity. Water hyperpolarization can be transferred to drugs, metabolites, or proteins that are waiting in an NMR spectrometer, either by exchange of labile protons or through intermolecular Overhauser effects. We also show that FLAPs are suitable polarizing agents for ¹³C‐labeled metabolites such as pyruvate, acetate, and alanine.     

Mössbauer spectroscopy of europium-containing glasses: optical activator study for x-ray image plates

A fluorozirconate glass (ZBLAN) containing BaCl ₂ nanocrystals doped with divalent Eu is a promising material for x-ray image plates for medical diagnosis. Since it is known that Eu ²⁺ readily oxidizes to Eu ³⁺, which reduces fluorescence efficiency of the image plates, ¹⁵¹Eu Mössbauer spectroscopy was used in this work to monitor the Eu oxidation state of the samples during degradation over time in the presence of ambient humidity. In addition, Mössbauer spectroscopic experiments show that the oxidation state has already changed during the glass melt: The sample made from 5 mol% EuCl ₂ contained 78 % EuCl ₂ + 22 % EuCl ₃ deduced from the relative areas of the absorption lines. The sample made from 2.5 mol% EuCl₂ + 2.5 mol% EuCl₂ contained 37 % EuCl₂ + 63 % EuCl₃, i.e. 26 % of the original EuCl ₂ was oxidized to EuCl ₃.