Mechanical behaviour of gel-filled additively-manufactured lattice structures under quasi-static compressive loading

The worldwide incidence of traumatic brain injuries (TBIs) is on the rise. Helmets are one of the best technologies available to prevent TBIs from impacts to the head during recreational and occupational activities. The most commonly used material for helmet liners is expanded polystyrene (EPS) foam. However, while EPS can reduce linear accelerations from impacts, it does not perform as well at reducing rotational accelerations which are considered to be the most harmful to brain tissue. Recently, prismatic lattice structures have shown promise in reducing these harmful rotational accelerations. Here, a new structure for energy dissipation applications is presented that is hypothesised to improve the energy dissipation of the prismatic lattice by filling it with a gel. To test this hypothesis, 3D printed prismatic lattices fabricated from PLA, PET-G, and ABS were filled with 5 wt% and 10 wt% agar and tested to failure under quasi-static compression. Compared to the unfilled control group, it was found that PLA lattices filled with 10 wt% agar had the best performance demonstrating a 46.1% increase in energy absorbed and 57.4% increase in displacement to failure. These results demonstrate the superior energy dissipation properties of gel-filled prismatic lattices compared to unfilled prismatic lattices during quasi-static compression. </p

Charge Density Modulated Shape-Dependent Electrocatalytic Activity of Gold Nanoparticles for the Oxidation of Ascorbic Acid

The electrocatalytic performance of noble metal nanoparticles depends upon their size, shape, composition, and crystalline facets. Here we demonstrate the shape-dependent electrocatalytic activity of Au nanoparticles toward ascorbic acid oxidation in acidic medium, wherein the catalysis is strongly influenced by the shape of the nanoparticles. The synthesis of (popcorn, tetrapod, and bipod shaped) Au nanoparticles was carried out using a systematic variation of the surfactant concentrations based on the seed-mediated growth technique at room temperature. Due to the facile electrostatic interaction of the positively charged Au nanoparticles with glassy carbon electrode, the modification of the surface with variable-shaped Au nanoparticles is accomplished without involving any binding agents. Among variable-shaped face-centered cubic (fcc) crystalline AuNPs, bipod-shaped Au nanoparticles (GNBipd) exhibit a superior electrocatalytic performance over tetrapod-shaped (GNTepd) and popcorn-shaped (GNPop) nanoparticles as inferred from the differential pulse voltammetry and electrochemical impedance spectroscopy. The results have been explained by invoking the relative surface free energy (γ) with preferentially exposed crystal planes, relative surface area (<i>A</i>), zeta potential (ξ), and the curvature-induced charge density (σ_q) at the apex for individual variable-shaped gold nanoparticles

Modulating Early Stage Amyloid Aggregates by Dipeptide-Linked Perylenebisimides: Structure–Activity Relationship, Inhibition of Fibril Formation in Human CSF and Aβ1–40

Amyloid aggregation is observed in many neurodegenerative diseases, but the formation of final plaque seldom correlates to the disease severity. Early and intermediate structures such as soluble oligomers are considered as primary toxic species in protein misfolding diseases specifically linked to Aβ in Alzheimer’s disease (AD). Two peptide-linked perylenebisimide isomers (PAPAP and APPPA) were developed to study the structure–activity relationship with a toxic Aβ oligomer in commercial Aβ as well as in human cerebrospinal fluid (CSF), diminish and inhibit them, and prevent them from forming toxic amyloid fibrils from an early stage. Self-aggregation of perylenebisimides enables the formation of nano/micro-objects that are used to interact with the hydrophobic regions of the peptide and direct the peptide aggregation into an “off-pathway”, preventing mature fibril formation. Remarkably, one of the Ala-Phe dipeptide-linked perylenebisimide isomers (APPPA) showed a high selectivity toward an Aβ oligomer and could also cross the endothelial monolayer barrier (blood–brain barrier, BBB) more efficiently than the other derivative (PAPAP). Kinetic ThT studies and AFM imaging provided strong proof of both of the isomers being able to inhibit fibrillation of prefibrillar and oligomeric Aβ in both the commercial Aβ1–40 peptide as well as in the real human CSF sample. Further, a correlation has been built using pristine fluorescence of perylenebisimides, showing modulation and “oligo-blocking”. The obtained data provides clear evidence that the mutual aggregation between the modulator and amyloid aggregate becomes predominant compared to their individual aggregation. These results reinforce the development of the structural platform design to diminish toxic oligomers, inhibit them, and prevent the formation of toxic amyloid fibrils at an early stage