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This paper explores how vacuum foam-drying of a protein is influenced by formulation parameters by investigating the foam structure, physical properties of the foam, and the stability of the protein. Recombinant human bile salt-stimulated lipase was used as a model of a protein drug. The stability of the lipase was evaluated through activity measurements. Two disaccharides (sucrose and trehalose), strongly tending to an amorphous form, were used as matrix formers, and the physical properties were assessed through residual water content, glass transition temperature, and crystalline state. Moreover, some formulations included surfactants with different sizes and structures of the head group. The alkyl chain length was kept constant to only investigate the impact of the surfactant head group, in the presence of the lipase, on the foamability and surface coverage of the lipase. The study demonstrated that the lipase allowed for a dry, solid foam with a foam overrun of up to 2600 %. The wall thickness of the dry, solid foam was estimated to be 20–50 µm. Clear differences between sucrose and trehalose as matrix former were identified. The lipase showed no tendency to lose activity because of the drying and rehydration, despite a proportion of the lipase covering the surfaces of the dry material., 'Correspondence Address: D. Tristan Osanlóo; RISE Research Institutes of Sweden, Stockholm, Box 5604, SE-114 86, Sweden; The authors would like to thank Swedish Orphan Biovitrum for providing the lipase and Croda Nordica AB for the delivery of the surfactants. Dr. Stefan Ulvenlund (ENZA Biotech AB) is gratefully acknowledged for the delivery of surfactants and valuable discussions. This research was funded by the Swedish Governmental Agency for Innovation Systems (VINNOVA) and was carried out within the competence center NextBioForm (grant number 2018-04730).

These results show that membrane interactions play a prominent role during intestinal translocation of an acylated peptide. Acylation benefits permeation for shorter and medium chains due to increased membrane interactions, however, for longer chains insertion in the membrane becomes dominant and hinders translocation, i.e. the peptides get 'stuck' in the cell membrane. Applying a transcellular absorption enhancer increases the dynamics of membrane insertion and detachment by fluidizing the membrane, thus facilitating its effects primarily on membrane associated peptides.

Udgivelsesdato: November

The applicability of different techniques, that is, Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), and intrinsic tryptophan fluorescence, for probing the structural changes of proteins in the water-in-oil emulsions are investigated using nondefatted bovine (BSA) and human serum albumin (HSA) as model proteins. FTIR shows that the overall secondary structure of the proteins changes to some extent, 12% for BSA and 9% for HSA, when these are incorporated into the emulsion. There was no evidence of changes in the distribution of secondary structural elements apart from the changes in overall secondary structure. A blue shift of 12 to 14 nm in the fluorescence emission maximum was observed for proteins in the emulsion and 3 to 11 nm in the simulated interior of the aqueous phase, thus indicating structural changes around the tryptophan residues. DSC scans indicated that the domains in the proteins change because the shape of the transition peaks changes, when the proteins were incorporated into the emulsions. The total enthalpy decreases for BSA and HSA when these are incorporated into the emulsion, and some changes to the transition temperatures are observed. All the applied techniques supplement each other to give a more complete picture of the structural changes in proteins in intact water-in-oil emulsions.