Light source-dependent photooxidation of therapeutic monoclonal antibodies: a comparative study of light-emitting...

Although therapeutic proteins are susceptible to visible light-induced photooxidation, the underlying mechanisms remain unclear because amino acid residues do not directly absorb light above 400 nm. To evaluate the role of light source characteristics, three monoclonal antibodies formulated in water were exposed to spectrally distinct fluorescent and light-emitting diode (LED) sources, eliminating excipient-related effects. Following exposure to visible light (400-800 nm), degradation was assessed by size-exclusion, Protein A, and ion-exchange chromatography, together with mass spectrometry. The LED spectrum displayed a pronounced emission at 451 nm and a broad band between 480 and 800 nm, whereas the fluorescent lamp exhibited prominent emissions at 436, 545, and 612 nm, with additional blue-light contributions overlapping antibody absorption. Both light sources induced dose- and antibody-dependent photodegradation, characterized by increased high molecular weight species, Fc-oxidation, acidic and basic charge variants, and methionine and tryptophan oxidation, without detectable fragmentation. Monomer content decreased by 1-4 %, Fc-oxidized variants increased by 5-20 %, and the ion-exchange main peak decreased by 2-8 %. LED-induced degradation was less pronounced than that induced by fluorescent light, reflecting reduced short-wavelength emission. These findings support photosensitizer-mediated oxidation at 400-450 nm and highlight the importance of controlling light exposure during bioprocessing.