In biomineralization, living organisms carefully control the crystallization of calcium carbonate to create functional materials and thereby often take advantage of polymorphism by stabilizing a specific phase that is most suitable for a given demand. In particular, the lifetime of usually transient amorphous calcium carbonate (ACC) seems to be thoroughly regulated by the organic matrix, so as to use it either as an intermediate storage depot or directly as a structural element in a permanently stable state. In the present study, we show that the temporal stability of ACC can be influenced in a deliberate manner also in much simpler purely abiotic systems. To illustrate this, we have monitored the progress of calcium carbonate precipitation at high pH from solutions containing different amounts of sodium silicate. It was found that growing ACC particles provoke spontaneous polymerization of silica in their vicinity, which is proposed to result from a local decrease of pH nearby the surface. This leads to the deposition of hydrated amorphous silica layers on the ACC grains, which arrest growth and alter the size of the particles. Depending on the silica concentration, these skins have different thicknesses and exhibit distinct degrees of porosity, therefore impeding to varying extents the dissolution of ACC and energetically favored transformation to calcite. Under the given conditions, crystallization of calcium carbonate was slowed down over tunable periods or completely prevented on time scales of years, even when ACC coexisted side by side with calcite in solution.
In this study, we examined and compared two different lipid-based nanosystems (LBNs), namely Transferosomes (TFs) and Monoolein Aqueous Dispersions (MADs), as delivery systems for the topical application of Ferulic Acid (FA), an antioxidant molecule derived from natural sources. Our results, as demonstrated through Franz-cell experiments, indicate that the LBNs produced with poloxamer 188 in their composition create a multilamellar system. This system effectively controls the release of the drug. Nonetheless, we found that the type of non-ionic surfactant can impact the drug release rate. Regarding FA diffusion from the MAD, this showed a lower diffusion rate compared with the TF. In terms of an in vivo application, patch tests revealed that all LBN formulations tested were safe when applied under occlusive conditions for 48 h. Additionally, human skin biopsies were used to determine whether FA-containing formulations could influence skin tissue morphology or provide protection against O3 exposure. Analyses suggest that treatment with TFs composed of poloxamer 188 and MAD formulations might protect against structural skin damage (as observed in hematoxylin/eosin staining) and the development of an oxidative environment (as indicated by 4-hyroxinonenal (4HNE) expression levels) induced by O3 exposure. In contrast, formulations without the active ingredient did not offer protection against the detrimental effects of O3 exposure.Inizio modulo.
Abstract Gaining external control over self‐organization is of vital importance for future smart materials. Surfactants are extremely valuable for the synthesis of diverse nanomaterials. Their self‐assembly is dictated by microphase separation, the hydrophobic effect, and head‐group repulsion. It is desirable to supplement surfactants with an added mode of long‐range and directional interaction. Magnetic forces are ideal, as they are not shielded in water. We report on surfactants with heads containing tightly bound transition‐metal centers. The magnetic moment of the head was varied systematically while keeping shape and charge constant. Changes in the magnetic moment of the head led to notable differences in surface tension, aggregate size, and contact angle, which could also be altered by an external magnetic field. The most astonishing result was that the use of magnetic surfactants as structure‐directing agents enabled the formation of porous solids with 12‐fold rotational symmetry.
Many neuroactive drugs are characterized by poor solubility, hampering their therapeutic potential and clinical research studies. For instance, the lipophilic molecules dimethylfumarate, retinyl palmitate, progesterone, and URB597 can be employed in the treatment of relapsing remitting multiple, early brain injury, learning deficits, and/or traumatic brain injuries. In this study, the possibility to encapsulate these drugs in lipid nanoparticles is investigated. Solid lipid nanoparticles and nanostructured lipid carriers have been produced by melt and ultrasonication of stearic triglyceride or a mixture of stearic triglyceride and caprylic/capric triglycerides. Mean diameters and morphology of lipid particles were studied by photon correlation spectroscopy, cryo-transmission electron microscopy, and x-ray diffraction, while encapsulation efficiency and in vitro drug release have been determined by HPLC. A behavioral study was conducted in rats to study the capability of lipid nanoparticles containing URB597 to alter behaviors relevant to psychiatric disorders after intranasal administration. In this regard, the nanoparticle surface has been modified by polysorbate 80 in order to obtain "stealth" nanoparticles. The nanoencapsulation strategy allowed increased drug solubility with respect to unphysiological solvent or solvent mixtures usually employed for animal and clinical studies. In particular, retinyl palmitate solubility in nanostructured lipid carriers has been increased up to eight-fold. Moreover, rat behavioral effects observed by nanoencapsulated URB597 administered intranasally suggest the therapeutic potential of this non-invasive route to treat social dysfunctions, such as autism.
Abstract Biogenic nucleation and crystallization occur in confined spaces with defined interfacial properties. However, the regulatory functions of organic players in the stabilization and transport of inorganic precursors such as ion clusters, liquid‐condensed phases, and amorphous particles are unclear. Given the prevalence of unstructured proteins in biogenic materials, the present study investigates the effects of biomineral‐associated, intrinsically disordered protein domains with simple and repetitive amino acid compositions on mineral nucleation and their capability to form distinct supramolecular assemblies. The quantitative assessment and structural evaluation of the nucleation process reveal that disordered regions confine hydrated mineral precursors within vesicles, transiently suppressing mineral precipitation. Stabilization of the amorphous mineral is attributed to protein self‐association and restructuration toward β‐configurations, triggered by specific bioinorganic interactions. In consequence, the conditioned macromolecules localize at phase boundaries formed upon liquid–liquid demixing of mineral precursors and stabilize the fluidic mineral precursors against crystallization. Thus, the conformational plasticity and self‐association of intrinsically disordered sequences in response to crystallization environments mediates the selection of functional macromolecular subensembles dedicated to biomaterial growth.
Spider silk-DNA conjugates comprising the recombinant spider silk protein eADF4(C16) and short oligonucleotides were arranged in a linear antiparallel and parallel as well as in a branched manner via designed complementarity of the DNA moieties. After cross-β fibril self-assembly, temperature-induced annealing of the DNA moieties triggered fibril association into ribbons, composed of aligned nanofibrils, and rafts composed of ribbons ordered into sharply bordered, squared fibrous microstructures. The formation of the superstructures was clearly dependent on the individual silk-DNA conjugate. A combination of 5'-conjugated silk moieties via complementary nucleic acids enhanced fibril association, whereas mixing complementary 5'- and 3'-silk conjugates inhibited the formation of higher-order structures.
