Table 2.

Most used functional groups and relative chemistries to obtain biomolecules conjugation on nanoparticles (Adapted with permission from [113]; published by American Chemical Society, 2013).

Biomolecule Functional Group	Reactive Group	Reaction Product
Aldehyde/ketone	Amines Hydrazine	Imine Hydrazone
(free) Amine	Acyl azides Aldehydes Arylating agents Carbodiimides Carbonates Epoxides Imidoesters N-hydroxysuccinimide ester (NHS) Isocyanates, Isothiocyanates Sulfonyl chlorides	Amide Imine Arylamine Amine Carbamate Secondary amine Amidine Amide Urea/thiourea Sulfonamide
Carboxylate	Carbodiimides, Carbonyldiimidazole Diazoalkanes, Diazoacetyl	Amides Esters
Hydroxyl	Epoxides/Alkyl halogens Periodate Isocyanates, Carbonyldiimidazole N,N′-disuccinimidyl carbonate, N-hydroxysuccinimidyl chloroformate	Ethers Aldehydes Carbamate or urethane
Reactive carbon (e.g., Tyr)	Diazonium	Diazo bond
(free) Thiol	Acryloyl derivatives Arylating agents Aziridine Haloacetyl/Alkyl Halide Maleimide Pyridyl disulfides, 5-thio-2-nitrobenzoic acid	Thioether Thioether Thioether Thioether Thioether Mixed disulfides