The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

CdSe/ZnS Quantum Rods (QRs) and Phenyl Boronic Acid BODIPY as Efficient Förster Resonance Energy Transfer (FRET) Donor-Acceptor Pair

The reversibility of the covalent interaction between boronic acids and 1,2- or 1,3-diols has put the spotlight on this reaction for its potential in the development of sensors and for the fishing of bioactive glycoconjugates. In this work, we describe the investigation of this reaction for the reversible functionalization of the surface of CdSe/ZnS Quantum Rods (QRs). With this in mind, we have designed a turn-off Förster resonance energy transfer (FRET) system that ensures monitoring the extent of the reaction between the phenyl boronic residue at the meso position of a BODIPY probe and the solvent-exposed 1,2-diols on QRs' surface. The reversibility of the corresponding boronate ester under oxidant conditions has also been assessed, thus envisioning the potential sensing ability of this system.

Ball milled glyco-graphene oxide conjugates markedly disrupted Pseudomonas aeruginosa biofilms

The engineering of the surface of nanomaterials with bioactive molecules allows controlling their biological identity thus accessing functional materials with tuned physicochemical and biological profiles suited for specific applications. Then, the manufacturing process, by which the nanomaterial surface is grafted, has a significant impact on their development and innovation. In this regard, we report herein the grafting of sugar headgroups on a graphene oxide (GO) surface by exploiting a green manufacturing process that relies on the use of vibrational ball mills, a grinding apparatus in which the energy is transferred to the reacting species through collision with agate spheres inside a closed and vibrating vessel. The chemical composition and the morphology of the resulting glyco-graphene oxide conjugates (glyco-GO) are assessed by the combination of a series of complementary advanced techniques (i.e. UV-vis and Raman spectroscopy, transmission electron microscopy, and Magic Angle Spinning (MAS) solid-state NMR (ssNMR) providing in-depth insights into the chemical reactivity of GO in a mechanochemical route. The conjugation of monosaccharide residues on the GO surface significantly improves the antimicrobial activity of pristine GO against P. aeruginosa. Indeed, glyco-GO conjugates, according to the monosaccharide derivatives installed into the GO surface, affect the ability of sessile cells to adhere to a polystyrene surface in a colony forming assay. Scanning electron microscopy images clearly show that glyco-GO conjugates significantly disrupt an already established P. aeruginosa biofilm.

Combining cross-coupling reaction and Knoevenagel condensation in the synthesis of glyco-BODIPY probes for DC-SIGN super-resolution bioimaging

Lectins are involved in a wide range of carbohydrate mediated recognition processes. Therefore, the availability of highly performant fluorescent tools tailored for lectin targeting and able to efficiently track events related to such key targets is in high demand. We report here on the synthesis of the glyco-BODIPYs 1 and 2, based on the efficient combination of a Heck-like cross coupling and a Knoevenagel condensation, which revealed efficient in addressing lectins. In particular, glyco-BODIPY 1 has two glycosidase stable C-mannose residues, which act as DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin) targeting modules. By using live-cell fluorescence microscopy, we proved that BODIPY-mannose 1 was efficiently taken up by immune cells expressing DC-SIGN receptors. Super-resolution stimulated emission depletion (STED) microscopy further revealed that the internalized 1 localized in membranes of endosomes, proving that 1 is a reliable tool also in STED applications. Of note, glyco-BODIPY 1 contains an aryl-azido group, which allows further functionalization of the glycoprobe with bioactive molecules, thus paving the way for the use of 1 for tracking lectin-mediated cell internalization in diverse biological settings.