5 research outputs found
Arginine-Presenting Peptide Hydrogels Decorated with Hydroxyapatite as Biomimetic Scaffolds for Bone Regeneration
Hydrogels are promising
candidates for biomimetic scaffolds of
the extracellular matrix in tissue engineering applications. However,
their use in bone tissue engineering is limited due to their low mechanical
properties. In this study, we designed and synthesized multicomponent
peptide-based hydrogels composed of fluorenyl-9-methoxycarbonyl diphenylalanine
(FmocFF), which contributed to the rigidity and stability of the hydrogel,
and Fmoc-arginine (FmocR), which mediated high affinity to hydroxyapatite
(HAP) due to the arginine moiety. The new hydrogels composed of nanometric
fibril networks were decorated with HAP and demonstrated high mechanical
strength with a storage modulus of up to 29 kPa. In addition, the
hydrogels supported cell adhesion and in vitro cell viability. These
properties suggest using these multicomponent organic–inorganic
hydrogels as functional biomaterials for improved bone regeneration
Highly Stretchable and Notch-Insensitive Hydrogel Based on Polyacrylamide and Milk Protein
Protein-based
hydrogels have received attention for biomedical applications and
tissue engineering because they are biocompatible and abundant. However,
the poor mechanical properties of these hydrogels remain a hurdle
for practical use. We have developed a highly stretchable and notch-insensitive
hydrogel by integrating casein micelles into polyacrylamide (PAAm)
networks. In the casein-PAAm hybrid gels, casein micelles and polyacrylamide
chains synergistically enhance the mechanical properties. Casein-PAAm
hybrid gels are highly stretchable, stretching to more than 35 times
their initial length under uniaxial tension. The hybrid gels are notch-insensitive
and tough with a fracture energy of approximately 3000 J/m<sup>2</sup>. A new mechanism of energy dissipation that includes friction between
casein micelles and plastic deformation of casein micelles was suggested
Water-Floating Giant Nanosheets from Helical Peptide Pentamers
One of the important challenges in
the development of protein-mimetic
materials is understanding the sequence-specific assembly behavior
and dynamic folding change. Conventional strategies for constructing
two-dimensional (2D) nanostructures from peptides have been limited
to using β-sheet forming sequences as building blocks due to
their natural tendency to form sheet-like aggregations. We have identified
a peptide sequence (YFCFY) that can form dimers <i>via</i> a disulfide bridge, fold into a helix, and assemble into macroscopic
flat sheets at the air/water interface. Due to the large driving force
for 2D assembly and high elastic modulus of the resulting sheet, the
peptide assembly induces flattening of the initially round water droplet.
Additionally, we found that stabilization of the helix by dimerization
is a key determinant for maintaining macroscopic flatness over a few
tens of centimeters even with a uniform thickness of <10 nm. Furthermore,
the ability to transfer the sheets from a water droplet to another
substrate allows for multiple stacking of 2D peptide nanostructures,
suggesting possible applications in biomimetic catalysis, biosensors,
and 2D related electronic devices
Revisiting Whitlockite, the Second Most Abundant Biomineral in Bone: Nanocrystal Synthesis in Physiologically Relevant Conditions and Biocompatibility Evaluation
The synthesis of pure whitlockite (WH: Ca<sub>18</sub>Mg<sub>2</sub>(HPO<sub>4</sub>)<sub>2</sub>(PO<sub>4</sub>)<sub>12</sub>) has remained a challenge even though it is the second most abundant inorganic in living bone. Although a few reports about the precipitation of WH in heterogeneous phases have been published, to date, synthesizing WH without utilizing any effects of a buffer or various other ions remains difficult. Thus, the related research fields have encountered difficulties and have not been fully developed. Here, we developed a large-scale synthesis method for pure WH nanoparticles in a ternary Ca(OH)<sub>2</sub>–Mg(OH)<sub>2</sub>–H<sub>3</sub>PO<sub>4</sub> system based on a systematic approach. We used excess Mg<sup>2+</sup> to impede the growth of hydroxyapatite (HAP: Ca<sub>10</sub>(PO<sub>4</sub>)<sub>6</sub>(OH)<sub>2</sub>) and the formation of other kinetically favored calcium phosphate intermediate phases. In addition, we designed and investigated the synthesis conditions of WH under the acidic pH conditions required to dissolve HAP, which is the most thermodynamically stable phase above pH 4.2, and to incorporate the HPO<sub>4</sub><sup>2–</sup> group into the chemical structure of WH. We demonstrated that pure WH nanoparticles can be precipitated under Mg<sup>2+</sup>-rich and acidic pH conditions without any intermediate phases. Interestingly, this synthesized nano-WH showed comparable biocompatibility with HAP. Our methodology for determining the synthesis conditions of WH could provide a new platform for investigating other important precipitants in aqueous systems
Tailoring a Tyrosine-Rich Peptide into Size- and Thickness-Controllable Nanofilms
Self-assembled
nanostructures of tyrosine-rich peptides have a
number of potential applications such as biocatalysts, organic conducting
films, and ion-selective membranes. In modulating a self-assembly
process of peptides, the interfacial force is an important factor
for kinetic control. Here, we present the formation of large-sized
and thickness-controllable nanofilms from the YYACAYY peptide sequence
(Tyr-C7mer peptide) using Langmuir–Blodgett and Langmuir–Schaefer
deposition methods. The Tyr-C7mer peptide showed typical surfactant-like
properties, which were demonstrated via the isotherm test (surface
pressure–area) by spreading the Tyr-C7mer peptide solution
onto an air/water interface. Uniform and flat peptide nanofilms were
successfully fabricated and characterized. The redox activity of densely
packed tyrosine moieties on the peptide nanofilm was also evaluated
by assembling silver nanoparticles on the nanofilm without requiring
any additives