Sequential Double “Clicks” toward Structurally Well‐Defined Heterogeneous N‐Glycoclusters: The Importance of Cluster Heterogeneity on Pattern Recognition In Vivo

Abstract

Structurally well‐defined heterogeneous N‐glycoclusters are prepared on albumin via a double click procedure. The number of glycan molecules present, in addition to the spatial arrangement of glycans in the heterogeneous glycoclusters, plays an important role in the in vivo kinetics and organ‐selective accumulation through glycan pattern recognition mechanisms.

A Strategy for Tumor Targeting by Higher‐Order Glycan Pattern Recognition: Synthesis and In Vitro and In Vivo Properties of Glycoalbumins Conjugated with Four Different N‐Glycan Molecules

“…Synthesis of heterogeneous glycan‐azides 2 was analogous to the approach described previously for preparation of 2ac and 2ae . [ 5 ] Formation of the target heterogeneous glycan‐azides 2 was accompanied by the production of the bis‐homo‐ 3 and mono‐substituted 4 , 5 products. Letters in compounds 2 – 5 indicate glycans included into the glycan‐azide.…”

“…The spatial arrangement of glycans on the albumin template, which relies on the order of glycans immobilization, plays an important role in pattern recognition. [ 3c,5 ] In this regard, we synthesized regioisomers of each glycoconjugate by changing the glycan immobilization sequence. Thus, for example, the regioisomer of the representative cluster 10aebd is glycoalbumin 10bdae , which was synthesized by reacting albumin 8 first with glycan‐aldehyde 7bd and then with glycan‐aldehyde 7ae (Scheme 3B).…”

“…As an alternative, we have also developed more structurally defined glycoalbumins, by simultaneously introducing two N ‐glycans that were linked in advance by the RIKEN click reaction (Protocol B, Figure 2). [ 5 ] This glycoconjugation method is superior in terms of controlled spatial arrangement of two different glycan molecules. When using both glycoalbumins prepared by two different RIKEN click methods (Protocols A and B, Figure 2), we found that the positions of two different glycans within the heterogeneous glycocluster played a significant role in pattern recognition.…”

Revealing biomedically relevant cell and lectin type-dependent structure–activity profiles for glycoclusters by using tissue sections as an assay platform

“…This favourable aspect is also a part of the in vivo studies with labelled neoglycoproteins presenting natural and synthetic glycans up to custom-made microheterogeneity used for targeting and imaging. [83][84][85][86][87][88][89] On the side of the proteins, mimicking the natural occurrence of lectins in mixtures, in terms of constituents and relative concentrations, will enable to trace currently not well-dened consequences of competition for binding sites and crossreactivity of glycoclusters among lectins. Given the assay's reliability and sensitivity as well as its use with any type of tissue, its application is advised, prior to considering testing glycoclusters in vivo, for example to minimise such overlaps in target binding by iterative structural renements including headgroup chemistry.…”

In Vivo Gold Complex Catalysis within Live Mice

“…Previously, our laboratory developed an innovative targeting method based on N‐glycoalbumins (Figure A), which were readily synthesized by immobilizing ten N‐glycan molecules onto albumin through the “RIKEN click” reaction . Changing the attached N‐glycan structure had a direct impact on the trafficking pathways, leading to organ‐selective accumulation (e.g., in the liver, intestine, spleen, and even tumors) –. One advantage of this approach is that translocalization of the metal complexes to target organs proceeds rapidly (within less than a few hours), thus limiting unwanted internalization or metabolization.…”