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Effect of Arginine on the Aggregation of Protein in Freeze-Dried Formulations Containing Sugars and Polyol: II. BSA Reconstitution and Aggregation

The current paper continues our study on the ability of l-arginine to prevent/reduce the aggregation of proteins that results from the various stresses during the lyophilisation and/or storage of lyophilized protein-based products. The first part of our study, i.e. formulation development, was devoted to the rational design and optimization of an l-arginine containing lyophilized formulation which can resist the natural tendency of l-arginine to absorb atmosphere moisture. Mannitol and trehalose were chosen among other excipients to be included in the protein-based formulation, as mannitol in a combination with l-arginine has been shown to reduce moisture sorption while trehalose provides a degree of lyoprotection. In the present study, a number of formulations, which comprised bovine serum albumin (BSA) with and without l-arginine, and with five different ratios of trehalose-to-mannitol (from 30:70 to 80:20) were lyophilised and assessed. The internal structures and the moisture sorption/retention of the lyophilized formulations were characterised. To study the effect of l-arginine on BSA solid-phase stability, the lyophilized powder was exposed to accelerated storage conditions (high moisture (75% RH) and temperature (22 or 45 °C)) for up to 24 h. The lyophilized BSA formulations were then reconstituted and solution-state protein aggregation assessed by turbidimetry at 360 nm and fluorescence spectroscopy using the thioflavin T assay. It was demonstrated that l-arginine can be used in protein-based freeze-dried formulations to significantly reduce the aggregation of protein during the manufacturing, storage and subsequent reconstitution. The results also revealed the importance of a sufficient amount of mannitol in the arginine-containing formulations.