Biocatalytic Synthesis of Coumarin S-Glycosides: Towards Non-Cytotoxic Probes for Biomedical Imaging and Sensing.

This study unveils an innovative method for synthesizing coumarin S-glycosides, employing original biocatalysts able to graft diverse carbohydrate structures onto 7-mercapto-4-methyl-coumarin in one-pot reactions. The fluorescence properties of the generated thio-derivatives were assessed, providing valuable insights into their potential applications in biological imaging or sensing. In addition, the synthesized compounds exhibited no cytotoxicity across various human cell lines. This research presents a promising avenue for the development of coumarin S-glycosides, paving the way for their application in diverse biomedical research areas.

"Mix and match" auto-assembly of glycosyltransferase domains delivers biocatalysts with improved substrate promiscuity.

Glycosyltransferases (GT) catalyze the glycosylation of bioactive natural products, including peptides and proteins, flavonoids, and sterols, and have been extensively used as biocatalysts to generate glycosides. However, the often narrow substrate specificity of wild-type GTs requires engineering strategies to expand it. The GT-B structural family is constituted by GTs that share a highly conserved tertiary structure in which the sugar donor and acceptor substrates bind in dedicated domains. Here, we have used this selective binding feature to design an engineering process to generate chimeric glycosyltransferases that combine auto-assembled domains from two different GT-B enzymes. Our approach enabled the generation of a stable dimer with broader substrate promiscuity than the parent enzymes that were related to relaxed interactions between domains in the dimeric GT-B. Our findings provide a basis for the development of a novel class of heterodimeric GTs with improved substrate promiscuity for applications in biotechnology and natural product synthesis.

Niosomes Functionalized with a Synthetic Carbohydrate Binding Agent for Mannose-Targeted Doxorubicin Delivery.

Niosomes are a potential tool for the development of active targeted drug delivery systems (DDS) for cancer therapy because of their excellent behaviour in encapsulating antitumorals and the possibility to easily functionalise their surface with targeting agents. Recently, some of us developed a synthetic carbohydrate binding agent (CBA) able to target the mannosidic residues of high-mannose-type glycans overexpressed on the surface of several cancer cell lines, promoting their apoptosis. In this article, we modified the structure of this mannose receptor to obtain an amphiphilic analogue suitable for the functionalization of doxorubicin-based niosomes. Several niosomal formulations and preparation methods were investigated deeply to finally obtain functionalized niosomes suitable for parental administration, which were stable for over six months and able to encapsulate up to 85% of doxorubicin (DOXO). In vitro studies, carried out towards triple-negative cancer cells (MDA-MB231), overexpressing high-mannose-type glycans, showed a cytotoxic activity comparable to that of DOXO but with an appreciable increment in apoptosis given by the CBA. Moreover, niosomal formulation was observed to reduce doxorubicin-induced cytotoxicity towards normal cell lines of rat cardiomyocytes (H9C2). This study is propaedeutic to further in vivo investigations that can aim to shed light on the antitumoral activity and pharmacokinetics of the developed active targeted DDS.