NGIWY-Amide: A Bioinspired Ultrashort Self-Assembled Peptide Gelator for Local Drug Delivery Applications

Fibrillar structures derived from plant or animal origin have long been a source of inspiration for the design of new biomaterials. The Asn-Gly-Ile-Trp-Tyr-NH2 (NGIWY-amide) pentapeptide, isolated from the sea cucumber Apostichopus japonicus, which spontaneously self-assembles in water to form hydrogel, pertains to this category. In this study, we evaluated this ultra-short cosmetic bioinspired peptide as vector for local drug delivery applications. Combining nuclear magnetic resonance, circular dichroism, infrared spectroscopy, X-ray diffraction, and rheological studies, the synthesized pentapeptide formed a stiff hydrogel with a high β-sheet content. Molecular dynamic simulations aligned well with scanning electron and atomic-force microscopy studies, revealing a highly filamentous structure with the fibers adopting a helical-twisted morphology. Model dye localization within the supramolecular hydrogel provided insights on the preferential distribution of hydrophobic and hydrophilic compounds in the hydrogel network. That was further depicted in the diffusion kinetics of drugs differing in their aqueous solubility and molecular weight, namely, doxorubicin hydrochloride, curcumin, and octreotide acetate, highlighting its versatility as a delivery vector of both hydrophobic and hydrophilic compounds of different molecular weight. Along with the observed cytocompatibility of the hydrogel, the NGIWY-amide pentapeptide may offer new approaches for cell growth, drug delivery, and 3D bioprinting tissue-engineering applications.

Development of Physics-Based Morphology Model with an Emphasis on the Interaction of Incoming Waves with Transient Bed Profile due to Scouring and Accretion using Dynamic Mesh

A physics-based morphology model [Seoul Foam] was developed using the dynamic mesh technique to explain the interaction between the sea bed, which undergoes deformation due to siltation and scouring, and the incoming waves. In doing so, OlaFlow, an Open Foam-based toolbox, was used as a hydrodynamic model. To verify the proposed physically-based morphology [Seoul Foam] in this study, numerical simulations of the shoaling process over the beach of the uniform slope were implemented. The numerical result shows that the formation process of a sand bar over the foreshore was successfully simulated. As can be easily anticipated, the size of the sand bar was closely linked to the nature of incoming waves, and in the case of a rough sea, the foreshore slope was rapidly deformed due to scouring. In mild seas, several sand waves were formed near the shoreline, and when the exposure time was the same, the size of the sand waves was not as large as in rough seas.

Simulation and experiment analysis of relationship between voids and permeability of composites

Due to the significant weight reduction advantage, aerospace composite tanks have become the focus of international competition of spacecraft. However, the permeation of small molecules at low temperature caused by the internal voids of composites is one of the key technical problems which restrict the engineering application of composite tanks. In this study, a combination of theoretical research and experimental research was adopted. By changing the curing pressures of the composites’ autoclave process, laminates with different porosities were prepared and tested for low-temperature permeability. Based on the grayscale processing and median filtering methods, a permeability prediction model with the true voids morphology of composite materials was established. Based on the random medium theory, the random voids model of composites was built to study the effect of void size and shape on the permeability of laminates. The results showed that the finite element analysis of composites, permeability based on the real voids morphology model was in good agreement with the experimental results, which proved the feasibility of this method. The permeation rate of laminates increased with the raised of porosity, and the internal porosity of the laminates could be diminished by improving the curing pressure so as to reduce the permeation of the composite components. Under the condition of a certain porosity, the laminates with small, stripe voids had a higher permeation rate than the laminates with large, circular voids.

Numerical Analysis of Modified Seabed Topography Due to the Presence of Breakwaters of Varying Reflection Characteristics using Physics-based Morphology Model [SeoulFoam]

Numerical simulations were implemented to look into the modified seabed topography due to the presence of breakwaters of varying reflection characteristics. The numerical model was composed of OlaFlow, an OpenFoam-based tool box, and a physics-based morphology model [Seoul Foam]. In doing so, the interaction between the seabed, which undergoes deformation due to siltation and scouring, and the incoming waves was described using Dynamic Mesh. The rubble-mound, vertical, and curved slit caisson breakwaters with varying reflection characteristics resulted in standing waves that differ from each other, shown to have a significant influence on the seabed topography. These results are in line with Nielsen’s study (1993) that sands saltated under the surface nodes of standing waves, where the near-bed velocities are most substantial, convected toward the surface antinodes by boundary-layer drift. Moreover, the crest of sand waves was formed under the surface antinodes of standing waves, and the trough of sand waves was formed under the surface antinodes. In addition, sand wave amplitude reaches its peak in the curved slit caisson with a significant reflection coefficient, and the saltation of many grains of sand would cause this phenomenon due to the increased near-bed velocity under the nodes when the reflection coefficient is getting large.

Numerical Analysis of Modified Bed-profiles due to the Presence of a Rubble Mound Breakwater using Physics-Based Morphology Model[SeoulFoam]

Among the many scouring-protection works near a rubble mound breakwater, stacking armoring rocks in multiple or single layers are most popular. The rationale of these scouring-protection works is based on the Equilibrium regime or the maximum scouring depth. However, considering natural beaches, which constantly change their shape according to sea waves conditions, the equilibrium regime or the maximum scouring depth mentioned above seems to foot on the fragile physical background. In this study, in order to test the above hypothesis, numerical simulations were carried out on the partial reflection from the slopes of rubble mound breakwater, and its ensuing standing waves formed in the front seas of a breakwater, the change in the bed profiles due to the formation of standing waves, and scouring depth at the base of a rubble mound breakwater. In doing so, numerical simulations were implemented using OlaFoam, an OpenFoam-based toolbox, and SeoulFoam (Cho, 2020), a physics-based morphology model. Numerical results show that the wave length of sand waves is closely linked with the incoming wave period, while amplitudes of sand waves are determined by incoming wave height. Moreover, the seabed profiles underwent significant changes due to the presence of a rubble mound breakwater. It was shown that the size of sand waves increased when compared before the installation, and the shape of sand waves is getting skewed toward the shore direction. It was also shown that as exposure time to standing waves increased, the amplitude of sand waves also increased, and the scouring depth near the base of a breakwater increased. These results are contrary to the Equilibrium regime, and the scouring prevention works based on the stacking of armoring rocks should be re-evaluated.

A new reduced-morphology model for CA1 pyramidal cells and its validation and comparison with other models using HippoUnit

Modeling long-term neuronal dynamics may require running long-lasting simulations. Such simulations are computationally expensive, and therefore it is advantageous to use simplified models that sufficiently reproduce the real neuronal properties. Reducing the complexity of the neuronal dendritic tree is one option. Therefore, we have developed a new reduced-morphology model of the rat CA1 pyramidal cell which retains major dendritic branch classes. To validate our model with experimental data, we used HippoUnit, a recently established standardized test suite for CA1 pyramidal cell models. The HippoUnit allowed us to systematically evaluate the somatic and dendritic properties of the model and compare them to models publicly available in the ModelDB database. Our model reproduced (1) somatic spiking properties, (2) somatic depolarization block, (3) EPSP attenuation, (4) action potential backpropagation, and (5) synaptic integration at oblique dendrites of CA1 neurons. The overall performance of the model in these tests achieved higher biological accuracy compared to other tested models. We conclude that, due to its realistic biophysics and low morphological complexity, our model captures key physiological features of CA1 pyramidal neurons and shortens computational time, respectively. Thus, the validated reduced-morphology model can be used for computationally demanding simulations as a substitute for more complex models.

A 3-D MODEL USING REPRESENTATIVE WAVES METHOD FOR SHORELINE MORPHODYNAMICS AROUND COASTAL STRUCTURES

The Fort Pierce Shore Protection Project nourishes a 2.1-km Atlantic Ocean shoreline south of Fort Pierce Inlet in St. Lucie County, Florida. The beach fill erodes nonuniformly with a hotspot along the northernmost 0.7 km requiring nourishment after about two years of normal wave regime. This study validated and applied to beach stabilization a shoreline morphology model to evaluate designs and combinations of coastal structures to increase the nourishment interval. Simulations of long-term normal tides, waves, and storm conditions show (a) shoreline movement pattern similar to the general historical pattern observed in the project area, including accurately indicating the largest erosion rate and shoreline retreat along the first 0.7 km south of the jetty; (b) the coastal structures retain beach fill longer, resulting in lower erosion rates from 0.8 to 6.4 km south of the jetty; and (c) the coastal structures alternative extends the normal beach nourishment interval from the current two years to four years. Application of representative waves allows accurate and efficient modeling of long-term 3-D beach and shoreline deformation.