Amalgamation of complex iron(III) ions and iron nanoclusters with MWCNTs as a route to potential T2 MRI contrast agents

Nikodem Kuźnik,1 Mateusz M Tomczyk,1 Marzena Wyskocka,1 Łukasz Przypis,1 Artur P Herman,1 Rafał Jędrysiak,1 Krzysztof K Koziol,2 Slawomir Boncel11Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Faculty of Chemistry, Silesian University of Technology, Gliwice, Poland; 2Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UKAbstract: Iron-filled multiwall carbon nanotubes (Fe@MWCNTs) were functionalized toward a variety of potential magnetic resonance imaging contrast agents. Oxidized Fe@MWNCTs were covered with PEG5000 via direct esterification or using acyl chloride derivatives. Alternatively, the latter were functionalized with an aminophenol ligand (Fe@O-MWCNT-L). Moreover, pristine Fe@MWCNTs were functionalized with N-phenylaziridine groups (Fe@f-MWCNT) via [2+1] cycloaddition of nitrene. All of these chemically modified nanotubes served as a vehicle for anchoring Fe3+ ions. The new hybrids – Fe(III)/Fe@(f-/O-)MWCNTs – containing 6%–14% of the “tethered” Fe3+ ions were studied in terms of the acceleration of relaxation of water protons in nuclear magnetic resonance. The highest transverse relaxivity r2=63.9±0.9 mL mg-1 s-1 was recorded for Fe(III)/Fe@O-MWCNT-L, while for Fe(III)/Fe@f-MWCNT, with r2=57.9±2.9 mL mg-1 s-1, the highest impact of the anchored Fe(III) ions was observed. The T1/T2 ratio of 30–100 found for all of the nanotube hybrids presented in this work is a very important factor for their potential application as T2 contrast agents. Increased stability of the hybrids was confirmed by ultraviolet–visible spectrophotometry.Keywords: multiwall carbon nanotubes, Fe3+, transverse relaxation time T2, MRI contrast agen

Leloir Glycosyltransferases in Applied Biocatalysis: A Multidisciplinary Approach

Enzymes are nature's catalyst of choice for the highly selective and efficient coupling of carbohydrates. Enzymatic sugar coupling is a competitive technology for industrial glycosylation reactions, since chemical synthetic routes require extensive use of laborious protection group manipulations and often lack regio- and stereoselectivity. The application of Leloir glycosyltransferases has received considerable attention in recent years and offers excellent control over the reactivity and selectivity of glycosylation reactions with unprotected carbohydrates, paving the way for previously inaccessible synthetic routes. The development of nucleotide recycling cascades has allowed for the efficient production and reuse of nucleotide sugar donors in robust one-pot multi-enzyme glycosylation cascades. In this way, large glycans and glycoconjugates with complex stereochemistry can be constructed. With recent advances, LeLoir glycosyltransferases are close to being applied industrially in multi-enzyme, programmable cascade glycosylations.BT/Biocatalysi

Engineering of continuous bienzymatic cascade process using monolithic microreactors – In flow synthesis of trehalose

Here, we present a two-step continuous flow enzymatic synthesis process in monolithic microreactors using basic sugars as substrates. In the first step UDP-glucose pyrophosphorylase (TaGalU) catalyses the synthesis of uridine-diphosphate-glucose (UDP-Glc) using uridine triphosphate (UTP) and glucose-1-phosphate (Glc-1-P). This is followed by the trehalose transferase (mCherry-TuTreT) catalysed reaction of UDP-Glc and Glc, to obtain trehalose. First, procedures for immobilisation of both enzymes on functionalised silica supports were studied and it was found that covalent bonding by amino groups using a glutaraldehyde linker gives highly active biocatalysts. Due to a drastic difference in temperature range of activity and stability of the immobilised enzymes a bi-reactor cascade was rationally the best solution. Depending on the applied flow rate and hence reaction (residence) time (1.5–10 min) the space-time-yield values varied, respectively, from 1.9 to 14.4 and 8.3 to 49.6 gproduct·L-1·h−1·mgprotein-1, for UDP-glucose pyrophosphorylase and trehalose transferase catalysed reactions. Prolonged (100 h) continuous flow operation showed that the system is operationally stable, but owing to neutral pH, it is prone to microbiological infections. They can be eliminated applying an antibacterial/antifungal therapy or preventive actions by storing and washing the reactors with a NaN3 solution. The presented process paves the way for the continuous in flow synthesis of natural and non-natural trehalose analogues and disaccharides.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.BT/Biocatalysi