1-Introduction 1.1-Reminders on bioactive molecules (drugs, nucleic acids, proteins) in interaction with polymer systems 1.2-Medical diagnostics: definition, challenges, ELISA method 1.3-Medical imaging: presentation of the major imaging techniques 1.4-Therapy: role of drug delivery systems, pharmacokinetics, pharmacodynamics, targeting methods 1.5-Interaction modes between polymer systems and-bioactive molecules 2- Colloids 2.1-Colloids obtained from preformed polymers