Functionalisation of magnetic nanoparticles (MNPs) plays an important role in achieving their full potential in biomedical applications. The coupling strategy used for linking the functionalising agent to the particle is a key component for success and will depend both on the coating of the MNP and the available functional groups on the targeting moiety. This chapter discusses the most common attachment methods and gives an overview of the essential biological

5.1 Strategies for Conjugation .................................................................................................... 130 5.1.1 Carbodiimide Coupling ............................................................................................ 130 5.1.2 Cyanogen Bromide Conjugation ............................................................................... 131 5.1.3 Maleimide Coupling ................................................................................................. 132 5.1.4 Click Chemistry ........................................................................................................ 132 5.1.5 Disulšde Bridges ...................................................................................................... 133 5.1.6 Histidine-Tagged Proteins ........................................................................................ 134 5.1.7 Ionic Coupling .......................................................................................................... 134

5.2 Biological Molecules for Conjugation .................................................................................. 134 5.2.1 Oligonucleotides and Nucleic Acids ......................................................................... 134 5.2.2 Peptides ..................................................................................................................... 135 5.2.3 Proteins ..................................................................................................................... 136 5.2.4 Phospholipids ............................................................................................................ 137 5.2.5 Carbohydrates ........................................................................................................... 137 5.2.6 Hormones .................................................................................................................. 138

5.3 Biological Interactions .......................................................................................................... 138 5.3.1 Antibody-Antigen .................................................................................................... 138 5.3.2 Avidin-Biotin ........................................................................................................... 139 5.3.3 DNA-DNA ............................................................................................................... 139 5.3.4 Ligand-Receptors ..................................................................................................... 140

5.4 Quality Control ..................................................................................................................... 140 5.4.1 Experimental Design ................................................................................................ 141 5.4.2 Purišcation ............................................................................................................... 141 5.4.3 Analysis of the Conjugate ......................................................................................... 142

5.5 Future Outlook ...................................................................................................................... 143 Acknowledgements ........................................................................................................................ 143 References ...................................................................................................................................... 143

molecules used for functionalising MNPs. We focus mainly on MNPs, but for comprehensiveness we refer to non-MNPs where applicable.