title: Interaction between the photosensitizer lumichrome and human serum albumin: effect of excipients.
abstract: Lumichrome (Lc) is a photodegradation product of riboflavin that can be used as a photosensitizer (PS) in antibacterial photodynamic therapy (aPDT). The binding of Lc with plasma proteins such as human serum albumin (HSA) could affect its efficiency as PS. Excipients are necessary to prepare stable formulations to be used in aPDT and they may affect the PS-HSA binding. Hydroxypropyl (HP)-α, β, γ-cyclodextrin (CD), polyethylene glycol 400 (PEG400) and Pluronic®F-127 (PF127) were selected as model excipients in this study. The intrinsic HSA fluorescence quenching and absorption and fluorescence spectroscopy were used to evaluate the Lc-HSA interaction in the absence and presence of excipients. Nano-differential scanning calorimetry (DSC) was used to determine the effect of excipients on HSA. The photostability of the samples was also evaluated. The combined results showed a modest interaction between Lc and HSA which was reduced mainly by HPβCD. No major alterations of the HSA nano-DSC thermogram were observed after addition of excipients. HSA did enhance Lc photodegradation. The presence of PF127 did also induce photochemical destabilization of Lc independent of HSA. In conclusion, HPαCD, HPγCD and PEG400 seemed to be the excipients more suitable for use in topical preparations containing Lc.
authors.affiliation: a School of Pharmacy, Department of Pharmaceutics , University of Oslo , Oslo , Norway.
authors.forename: Victoria J
authors.initials: VJ
authors.lastname: Valerón Bergh
authors.affiliation: a School of Pharmacy, Department of Pharmaceutics , University of Oslo , Oslo , Norway.
authors.forename: Hanne
authors.initials: H
authors.lastname: Hjorth Tønnesen
mesh_terms: D005079:Excipients; D005415:Flavins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D017319:Photosensitizing Agents / Q000737:chemistry / Q000378:metabolism; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism
chemical_list: D005079:Excipients; D005415:Flavins; D017319:Photosensitizing Agents; D012709:Serum Albumin; C001559:7,8-dimethylalloxazine
keywords: Cyclodextrin; Pluronic®; Stern–Volmer; fluorescence quenching; photostability; polyethylene glycol