A multicentre and multi-national evaluation of the accuracy of quantitative Lu-177 SPECT/CT imaging performed within the MRTDosimetry project

Purpose Patient-specific dosimetry is required to ensure the safety of molecular radiotherapy and to predict response. Dosimetry involves several steps, the first of which is the determination of the activity of the radiopharmaceutical taken up by an organ/lesion over time. As uncertainties propagate along each of the subsequent steps (integration of the time–activity curve, absorbed dose calculation), establishing a reliable activity quantification is essential. The MRTDosimetry project was a European initiative to bring together expertise in metrology and nuclear medicine research, with one main goal of standardizing quantitative 177Lu SPECT/CT imaging based on a calibration protocol developed and tested in a multicentre inter-comparison. This study presents the setup and results of this comparison exercise. Methods The inter-comparison included nine SPECT/CT systems. Each site performed a set of three measurements with the same setup (system, acquisition and reconstruction): (1) Determination of an image calibration for conversion from counts to activity concentration (large cylinder phantom), (2) determination of recovery coefficients for partial volume correction (IEC NEMA PET body phantom with sphere inserts), (3) validation of the established quantitative imaging setup using a 3D printed two-organ phantom (ICRP110-based kidney and spleen). In contrast to previous efforts, traceability of the activity measurement was required for each participant, and all participants were asked to calculate uncertainties for their SPECT-based activities. Results Similar combinations of imaging system and reconstruction lead to similar image calibration factors. The activity ratio results of the anthropomorphic phantom validation demonstrate significant harmonization of quantitative imaging performance between the sites with all sites falling within one standard deviation of the mean values for all inserts. Activity recovery was underestimated for total kidney, spleen, and kidney cortex, while it was overestimated for the medulla. Conclusion This international comparison exercise demonstrates that harmonization of quantitative SPECT/CT is feasible when following very specific instructions of a dedicated calibration protocol, as developed within the MRTDosimetry project. While quantitative imaging performance demonstrates significant harmonization, an over- and underestimation of the activity recovery highlights the limitations of any partial volume correction in the presence of spill-in and spill-out between two adjacent volumes of interests.

Partial Purification of Polyphenol Oxidase (PPO) from Mango Seed Kernel (MSK) using Alcohol/Salt-based Aqueous Two-Phase System (ATPS)

Background: Polyphenol oxidase (PPO) has applications in pharmaceutical, environmental, and food industries, however, conventional techniques for its purification are considered costly and laborious. Alternative methods of purification are needed. Methods: This study explored the use of an alcohol/salt-based aqueous two-phase system (ATPS) to partially purify PPO from mango seed kernel (MSK). Specifically, this study determined the effects of 1-propanol/potassium phosphate buffer mass ratio on the partition parameters such as partition coefficients, activity recovery, and purification fold. Results: The enzyme partition coefficient (K E ) was greater than 1, which signified that more PPO was partitioned in the top phase due to its hydrophobic nature. Specifically, the 3.22 1-propanol/PPB mass ratio had the highest K E of 1.91 ± 0.16 and 1.46 ± 0.16 for runs 1 and 2, respectively. Moreover, the same mass ratio led to the highest activity recovery in the top phase reaching up to 73.99 ± 1.56% for run 1 and 64.27 ± 2.48% for run 2. In terms of purification fold, runs 1 and 2 had PF values of 0.55 ± 0.05 and 0.70 ± 0.01, respectively. Since the values obtained were low due to the large number of contaminants extracted together with the target enzyme in the top phase, the use of a back-extraction step recovered the PPO in the bottom phase and resulted in an activity recovery of 82.94 ± 1.05% and a purification fold of 7.01 ± 0.95. Conclusion: Results have shown that varying the mass ratio had significant effects on the partition parameters.

Immobilization of Old Yellow Enzymes via Covalent or Coordination Bonds

Ene-reductases (ERs) belonging to the old yellow enzyme (OYE) family have been thoroughly investigated for the stereospecific reduction of activated prochiral C=C double bonds. In this work, OYE3 was immobilized both by covalent binding on glyoxyl-agarose (OYE3-GA), and by affinity-based adsorption on EziGTM particles (OYE3-EziG). The immobilized OYE3-GA was demonstrated to be active (activity recovery = 52%) and to retain almost 100% of its activity under the enzymatic assay conditions (50 mM phosphate buffer pH 7, 28 °C) for six days, whereas the activity of the non-immobilized enzyme dropped to 50% after two days. In the case of EziGTM, the highest activity recovery (54%) was achieved by using the most hydrophilic carrier (EziGTM Opal) that was selected for the full characterization of this type of enzyme preparation (stability, recycling, re-use, enzyme leakage). OYE3-EziG was slightly less stable than OYE3-GA under the same experimental conditions. OYE3-GA could be recycled and re-used for up to 12 reaction cycles in the bioreduction of α-methyl-trans-cinnamaldehyde; after 12 runs, the highest conversion achieved was 40%. In the case of the co-immobilized OYE3/GDH-EziG, the conversion dropped to 56% after two reaction cycles. No enzyme leakage was detected over 48 h for both OYE3-GA and OYE3/GDH-EziG (50 mM phosphate buffer pH 7, 28 °C). These seed results pave the way for a true optimization of the immobilization of OYE3, as well as for the use of immobilized OYE3 for preparative applications both in batch and continuous flow conditions.

Regeneration of Raney®-Nickel Catalyst for the Synthesis of High-Value Amino-Ester Renewable Monomers

Aiming to synthesize high-value renewable monomers for the preparation of renewable specialty polyamides, we designed a new protocol. Amino-esters, produced via the hydrogenation of unsaturated nitrile-esters, are alternative monomers for the production of these polymers. A high monomer yield can be obtained using a Raney®-nickel catalyst despite the drawback of fast deactivation. The hydrogenation of 10-cyano-9-decenoate (UNE11) was tentatively reactivated by three different regeneration procedures: solvent wash, regeneration under hydrogen, and regeneration under sonication. Among these procedures, the in-pot catalyst regeneration (H2 30 bar, 150 °C) demonstrated complete activity recovery and full recycling.