4 research outputs found
Insights on the Mechanism of Formation of Protein Microspheres in a Biphasic System
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
Enzymatically Active Microgels from Self-Assembling Protein Nanofibrils for Microflow Chemistry
Amyloid fibrils represent a generic class of protein structure associated with both pathological states and with naturally occurring functional materials. This class of protein nanostructure has recently also emerged as an excellent foundation for sophisticated functional biocompatible materials including scaffolds and carriers for biologically active molecules. Protein-based materials offer the potential advantage that additional functions can be directly incorporated <i>via</i> gene fusion producing a single chimeric polypeptide that will both self-assemble and display the desired activity. To succeed, a chimeric protein system must self-assemble without the need for harsh triggering conditions which would damage the appended functional protein molecule. However, the micrometer to nanoscale patterning and morphological control of protein-based nanomaterials has remained challenging. This study demonstrates a general approach for overcoming these limitations through the microfluidic generation of enzymatically active microgels that are stabilized by amyloid nanofibrils. The use of scaffolds formed from biomaterials that self-assemble under mild conditions enables the formation of catalytic microgels while maintaining the integrity of the encapsulated enzyme. The enzymatically active microgel particles show robust material properties and their porous architecture allows diffusion in and out of reactants and products. In combination with microfluidic droplet trapping approaches, enzymatically active microgels illustrate the potential of self-assembling materials for enzyme immobilization and recycling, and for biological flow-chemistry. These design principles can be adopted to create countless other bioactive amyloid-based materials with diverse functions
Sequential Release of Proteins from Structured Multishell Microcapsules
In nature, a wide range of functional
materials is based on proteins.
Increasing attention is also turning to the use of proteins as artificial
biomaterials in the form of films, gels, particles, and fibrils that
offer great potential for applications in areas ranging from molecular
medicine to materials science. To date, however, most such applications
have been limited to single component materials despite the fact that
their natural analogues are composed of multiple types of proteins
with a variety of functionalities that are coassembled in a highly
organized manner on the micrometer scale, a process that is currently
challenging to achieve in the laboratory. Here, we demonstrate the
fabrication of multicomponent protein microcapsules where the different
components are positioned in a controlled manner. We use molecular
self-assembly to generate multicomponent structures on the nanometer
scale and droplet microfluidics to bring together the different components
on the micrometer scale. Using this approach, we synthesize a wide
range of multiprotein microcapsules containing three well-characterized proteins:
glucagon, insulin, and lysozyme. The localization of each protein
component in multishell microcapsules has been detected by labeling
protein molecules with different fluorophores, and the final three-dimensional
microcapsule structure has been resolved by using confocal microscopy
together with image analysis
techniques. In addition, we show that
these structures can be used to tailor the release of such functional
proteins in a sequential manner. Moreover, our observations demonstrate
that the protein release mechanism from multishell capsules is driven
by the kinetic control of mass transport of the cargo and by the dissolution
of the shells. The ability to generate artificial materials that incorporate
a variety of different proteins with distinct functionalities increases
the breadth of the potential applications of artificial protein-based
materials and provides opportunities to design more refined functional
protein delivery systems
From Basic Principles of Protein–Polysaccharide Association to the Rational Design of Thermally Sensitive Materials
Biology resolves
design requirements toward functional materials
by creating nanostructured composites, where individual components
are combined to maximize the macroscale material performance. A major
challenge in utilizing such design principles is the trade-off between
the preservation of individual component properties and emerging composite
functionalities. Here, polysaccharide pectin and silk fibroin were
investigated in their composite form with pectin as a thermal-responsive
ion conductor and fibroin with exceptional mechanical strength. We
show that segregative phase separation occurs upon mixing, and within
a limited compositional range, domains ∼50 nm in size are formed
and distributed homogeneously so that decent matrix collective properties
are established. The composite is characterized by slight conformational
changes in the silk domains, sequestering the hydrogen-bonded β-sheets
as well as the emergence of randomized pectin orientations. However,
most dominant in the composite’s properties is the introduction
of dense domain interfaces, leading to increased hydration, surface
hydrophilicity, and increased strain of the composite material. Using
controlled surface charging in X-ray photoelectron spectroscopy, we
further demonstrate Ca ions (Ca2+) diffusion in the pectin
domains, with which the fingerprints of interactions at domain interfaces
are revealed. Both the thermal response and the electrical conductance
were found to be strongly dependent on the degree of composite hydration.
Our results provide a fundamental understanding of the role of interfacial
interactions and their potential applications in the design of material
properties, polysaccharide–protein composites in particular