Search for common conjugation chemistries, and coupling reagent based attachments BUT have to be careful with purification and water solubility issues etc. Bonding through spacers is another feasible way to attach two groups which otherwise can not be linked through direct covalent bonding. With liberties to structural changes, a redox-based reaction between the two can be carried out!

https://www.researchgate.net/post/How_could_I_crosslink_D-Mannose_on_polystyrene_particles

https://www.researchgate.net/post/Have_anyone_ever_use_amine-coated_polystyrene_beads_for_conjugating_with_protein_or_carbohydrate

Also, check Bolton-Hunter Reagent and Method!

First of all, thank you very much for your help.

The base idea - behind my question - is to form a microparticle, which can specifically activate the alternative pathway of the complement system in vitro and in vivo as well.