Could albumin affect the self-assembling properties of a block co-polymer system and drug release? An in-vitro study.

PURPOSE: This work investigated the influence of a model protein, bovine serum albumin (BSA), on the properties of a thermogelling formulation intended for administration inside body compartments where there is high albumin content, as in the case of inflamed joints; it also explored the relation between the variation of these properties and release performance of methotrexate (MTX), a drug used to treat forms of arthritis and rheumatic conditions.

METHODS: The influence of BSA on the micellisation and gelation behaviour of Poloxamer 407, chosen as a model copolymer, was studied by differential scanning calorimetry (microDSC), dynamic light scattering (DLS), fluorescence spectroscopy and rheology studies. A release study of MTX loaded inside the hydrogel in presence and in absence of BSA was performed.

RESULTS: DLS and microDSC data revealed that the micellisation process was not affected by the protein, as demonstrated by unaltered micellar size and thermodynamic parameters. While the presence of BSA in the copolymer system reduced gel consistency, the hydrogel release performance was only slightly affected.

CONCLUSION: Our results suggested that the kinetics of MTX release mainly depended on the presence of the thermogelling copolymer, although other mechanisms related to BSA could be involved. Finally, the study assessed the feasibility of using a thermogelling hydrogel for in situ drug administration in areas with the presence of high protein concentrations.