Intrafibrillar Mineralization of Self-Assembled Elastin-Like Recombinamer Fibrils

Producción CientíficaBiomineralization of bone, a controlled process where hydroxyapatite nanocrystals preferentially deposit in collagen fibrils, is achieved by the interplay of the collagen matrix and noncollagenous proteins. Mimicking intrafibrillar mineralization in synthetic systems is highly attractive for the development of advanced hybrid materials with elaborated morphologies and outstanding mechanical properties, as well as understanding the mechanisms of biomineralization. Inspired by nature, intrafibrillar mineralization of collagen fibrils has been successfully replicated in vitro via biomimetic systems, where acidic polymeric additives are used as analogue of noncollagenous proteins in mediating mineralization. The development of synthetic templates that mimic the structure and functions of collagenous matrix in mineralization has yet to be explored. In this study, we demonstrated that self-assembled fibrils of elastin-like recombinamers (ELRs) can induce intrafibrillar mineralization. The ELRs displayed a disordered structure at low temperature but self-assembled into nanofibrils above its inverse transition temperature. In the presence of the self-assembled ELR fibrils, polyaspartate-stabilized amorphous calcium phosphates preferentially infiltrated into the fibrils and then crystallized into hydroxyapatite nanocrystals with their [001] axes aligned parallel to the long axis of the ELR fibril. As the recombinant technology enables designing and producing well-defined ELRs, their molecular and structural properties can be fine-tuned. By examining the ultrastructure of the self-assembled ELRs fibrils as well as their mineralization, we concluded that the spatial confinement formed by a continuum β-spiral structure in an unperturbed fibrillar structure rather than electrostatic interactions or bioactive sequences in the recombinamer composition played the crucial role in inducing intrafibrillar mineralization.2018-08-01Ministerio de Economía, Industria y Competitividad (Project MAT2013-42473-R and MAT2015-68901R)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA244U13, VA313U14 and VA015U16

Self-assembly of minimal peptoid sequences

Peptoids are biofunctional N-substituted glycine peptidomimics. Their self-assembly is of fundamental interest because they demonstrate alternatives to conventional peptide structures based on backbone chirality and beta-sheet hydrogen bonding. The search for self-assembling, water-soluble “minimal” sequences, be they peptide or peptidomimic, is a further challenge. Such sequences are highly desired for their compatibility with biomacromolecules and convenient synthesis for broader application. We report the self-assembly of a set of trimeric, water-soluble α-peptoids that exhibit a relatively low critical aggregation concentration (CAC ∼ 0.3 wt %). Cryo-EM and angle-resolved DLS show different sequence-dependent morphologies, namely uniform ca. 6 nm wide nanofibers, sheets, and clusters of globular assemblies. Absorbance and fluorescence spectroscopies indicate unique phenyl environments for π-interactions in the highly ordered nanofibers. Assembly of our peptoids takes place when the sequences are fully ionized, representing a departure from superficially similar amyloid-type hydrogen-bonded peptide nanostructures and expanding the horizons of assembly for sequence-specific bio- and biomimetic macromolecules

2D & 3D Nanomaterial Fabrication With Biological Molecular Frameworks

Recently, there has been a heightened amount of work done in the field of biomineralization. By taking inspiration from natures\u27 phenomenonal individualities as a means to develop new and interesting nanostructures of varying sizes and dimensions, there is a newly developed design, namely Biomimetic Crystallization Nanolithography (BCN). With this method, the simultaneous nano-patterning and crystallization has been achieved using urease as the nucleation point and the hydrolysis of urea to obtain patterns of oxide semiconductor material, namely zinc oxide, at room temperature and aqueous solvent. The new and interesting characteristic of BCN involves the construction of amorphous inks of ZnO through the use of an enzyme, its hydrolyzing abilities, and Zn-precursors. These inks are nano-patterned with the tip of an atomic force microscope, which has found to induce the crystallization of the amorphous inks into crystalline patterns. Also, a micro-contact printing process was developed and utilized as a means to directly pattern enzymes in a single step without the loss of enzyme activity after printing. By modifying the substrate to display aldehyde groups, the direct stamping of urease enables the simultaneous patterning and covalent cross-linking of urease under the reducing agent NaCNBH4, which does not degrade the enzyme activity. The exposed urease particles on the substrate, free from the cross-linker, were still catalytically active and utilized to grow crystalline ZnO nanoparticles on the enzyme patterns in ambient conditions and in aqueous solution. Recently, there has been a growing demand to have the ability of fabricating nanosized structures that are 3D in orientation, produced in large quantities and yield uniform shapes and sizes. Biomimetic assembly has been given attention in that it relies on the use of bio-inspired materials that are characteristically organized from the macroscale all the way to the nanoscale. Peptides are one of nature\u27s building blocks that have the ability to take an active role in self-assembly and that can further be integrated to consequently yield the self-organization of structures with interesting properties in high quantities. In this study, first, micron-sized assembly of streptavidin-functionalized Au nanoparticles and biotinylated collagen peptides into cubic structures was demonstrated as assembled peptide frameworks incorporate nanoparticles in the exact position of unit cell, and then other fluorescent molecules or nanoparticles with biotin moieties were co-assembled to generate complex 3D nanoparticle assemblies. Energy transfer (FRET) and excitonic lifetime change of between QDs (donors) and AuNPs (acceptors) in these assemblies were investigated. As the interparticle distance was changed, the FRET efficiency also changed, shown by emission lifetime measurements. The energy transfer efficiency was also affected by the number of acceptor nanoparticles around the donor QDs. This type of robust large-scale 3D material assembly technique with precise positioning could be beneficial for future bottom-up device assembly such as solar cells, batteries, and metamaterials