Insights on the Mechanism of Formation of Protein Microspheres in a Biphasic System

Abstract

Microspheres of bovine serum albumin (BSA) and silk fibroin are produced by applying ultrasound in a biphasic system consisting of an aqueous protein solution and an organic solvent. The protein microspheres are dispersed in an aqueous media where the protein remains at the interface covering the organic solvent. This only occurs when high shear forces are applied that induce changes to force the protein to the interface. Fourier transform infrared results indicate a large increase in the content of the β-sheet during the formation of silk fibroin microspheres. Molecular dynamics simulations show a clear adaption on the 3D structure of BSA when stabilized at the interface, without major changes in secondary structure. Further studies demonstrate that high water content, oil solvents, and larger peptides with separated and clear hydrophobic and hydrophilic areas lead to more stable and smaller spheres. This is the first time that these results are presented. We also present herein the rationale to produce tailored protein microspheres with a controlled size, controlled charge, and increased stability.

Orange IV stabilizes silk fibroin microemulsions

“…The results obtained are in accordance with the literature [12,21,23,53], where it is described that SF particles prepared by mechanical mixing and self-assembly process are predominantly composed by β-sheets. The formation of β-sheets increases encapsulation efficiency of small molecules and enables a tight control of the release kinetics [12,13].…”

“…Despite that n ‐dodecane can cause cytotoxicity (according to manufacturer's product data sheet), previous work done by our research group showed that only high ratios of n ‐dodecane (above 40%) were considered toxic in the human cell line RKO (unpublished data and ). Although a proven absence of toxicity can only be evaluated with direct tests to evaluate the SF‐ME effect on cells, we may predict that the formulations produced in this study should be biocompatible and will not lead to cytotoxicity due to n ‐dodecane.…”

“…The use of emulsification processes in SF solutions, associated to the enrichment of β-sheet content in the protein, usually promotes the formation of spherical particles [12,19,54]. Particularly, Silva et al [21] have observed by STEM the morphology of SF-MPs produced by sonochemical emulsification and described a spherical shape with smooth surfaces. The authors also highlight that particles with spherical morphology provide minimum contact with the aqueous environment and longer diffusion transport, thus allowing efficient entrapment of drugs and higher controlled release over time [21].…”

Smart Nanocontainers: Preparation, Loading/Release Processes and Applications

“…Protein nanocapsules could be prepared by various emulsification methods, such as single/double emulsions [59,60], polymerization [61], phase separation/coacervation [62], spray drying/spray congealing [63,64] and ultrasonic emulsification [65].…”

On the Routines of Wild-Type Silk Fibroin Processing Toward Silk-Inspired Materials: A Review

“…Currently, there is a modest number of examples for the silk‐derived materials, formulated by ultrasonication. Our group reported on both bovine serum albumin (BSA) and SF‐based microspheres, formed by high‐intensity ultrasound . BSA secondary structure was not disturbed during the microsphere synthesis, but an increase in the β‐sheet content for silk was detected.…”