The present invention relates to a method and apparatus for the isolation, modification and re-administration of a molecule or biomolecule, or a class of biomolecules, from the body fluid of a mammal via an extracorporeal closed circuit device. The device is able to capture and modify the biomolecule by the covalent or non-covalent attachment of a secondary molecule or protein, by cross-linking the captured molecule, or by altering the structure of the molecule (for example, by deglycosylation, peptide cleavage, or aggregation). The apparatus can be used to return the modified molecule or biomolecule to the mammalian subject. The device and methods may be utilized for the patient-specific diagnosis and/or treatment of a disease state which presents an associated molecule or protein in plasma or any other fluidized physiological system.The methods and apparatus may also be employed as a closed system allowing the on-line purification and/or modification of a target molecule or biomolecule from a fluid source such as a bioreactor or perfusion bioreactor.
