Role of sheet-edge interactions in β-sheet self-assembling peptide hydrogels

Hydrogels’ hydrated fibrillar nature makes them the material of choice for the design and engineering of 3D scaffolds for cell culture, tissue engineering, and drug-delivery applications. One particular class of hydrogels which has been the focus of significant research is self-assembling peptide hydrogels. In the present work, we were interested in exploring how fiber–fiber edge interactions affect the self-assembly and gelation properties of amphipathic peptides. For this purpose, we investigated two β-sheet-forming peptides, FEFKFEFK (F8) and KFEFKFEFKK (KF8K), the latter one having the fiber edges covered by lysine residues. Our results showed that the addition of the two lysine residues did not affect the ability of the peptides to form β-sheet-rich fibers, provided that the overall charge carried by the two peptides was kept constant. However, it did significantly reduce edge-driven hydrophobic fiber–fiber associative interactions, resulting in reduced tendency for KF8K fibers to associate/aggregate laterally and form large fiber bundles and consequently network cross-links. This effect resulted in the formation of hydrogels with lower moduli but faster dynamics. As a result, KF8K fibers could be aligned only under high shear and at high concentration while F8 hydrogel fibers were found to align readily at low shear and low concentration. In addition, F8 hydrogels were found to fragment at high concentration because of the high aggregation state stabilizing the fiber bundles, resulting in fiber breakage rather than disentanglement and alignment

Elastic flow instabilities and macroscopic textures in graphene oxide lyotropic liquid crystals

Graphene oxide (GO) forms a well-aligned lyotropic liquid crystal (LC) phase in aqueous dispersions at relatively low concentrations. Under a remarkably wide range of shear rates, we report hitherto unobserved shear-induced polarized light image patterns, a Maltese cross combined with shear banding, recorded in real time and in situ during rheological measurements. This is shown to be a result of elastic flow instabilities that manifest as a helical flow in alternating bands of left- and right-handed helices, arising from a combination of shear flow and Taylor-type vortex flow. The instability is observed for LCs formed from large aspect ratio GO particles owing to their unique viscoelastic properties, but not for smaller aspect ratio particles. This phenomenon coincides with rheopecty and anomalous small-angle X-ray scattering patterns under shear flow, which confirm the instabilities. The results presented here could lead to advanced control over macroscopic periodic alignment in technologically relevant dispersions of two-dimensional material particles

Magnetic Chitosan Bionanocomposite Films as a Versatile Platform for Biomedical Hyperthermia

Responsive magnetic nanomaterials offer significant advantages for innovative therapies, for instance, in cancer treatments that exploit on-demand delivery on alternating magnetic field (AMF) stimulus. In this work, biocompatible magnetic bionanocomposite films are fabricated from chitosan by film casting with incorporation of magnetite nanoparticles (MNPs) produced by facile one pot synthesis. The influence of synthesis conditions and MNP concentration on the films’ heating efficiency and heat dissipation are evaluated through spatio-temporal mapping of the surface temperature changes by video-thermography. The cast films have a thickness below 100 µm, and upon exposure to AMF (663 kHz, 12.8 kA m−1), induce exceptionally strong heating, reaching a maximum temperature increase of 82 °C within 270 s irradiation. Further, it is demonstrated that the films can serve as substrates that supply heat for multiple hyperthermia scenarios, including: i) non-contact automated heating of cell culture medium, ii) heating of gelatine-based hydrogels of different shapes, and iii) killing of cancerous melanoma cells. The films are versatile components for non-contact stimulus with translational potential in multiple biomedical applications. © 2023 The Authors. Advanced Healthcare Materials published by Wiley-VCH GmbH.This work was developed within the scope of the projects CICECO– Aveiro Institute of Materials UIDB/50011/2020, UIDP/50011/2020 &LA/P/0006/2020, CESAM -UIDP/50017/2020, and UIDB/50017/2020 andLA/P/0094/2020 and M-ERA-NET2/0021/2016 – BIOFOODPACK – Bio-composite Packaging for Active Preservation of Food. A.B. is thankfulto FCT for grant SFRH/BD/148856/2019. C.N. is grateful to the Por-tuguese national funds (OE) through FCT IP in the scope of the frame-work contract foreseen in the numbers 4, 5, and 6 of the Article 23of the Decree-Law 57/2016 of August 29 changed by Law 57/2017 ofJuly 19. J.K.W., D.W., and D.F.B. acknowledge support from the ScienceFoundation Ireland (16/IA/4584). E.R.-H. acknowledges financial supportfrom the MCIN/AEI/10.13039/501100011033 (Spain, project PID2019-105479RB-I00). M.M.C. and L.P.F. acknowledge FCT for Centre grantsUIDB/04046/2020 and UIDP/04046/2020 to BioISI. Part of the work in this article is based on the mobility exchange program of COST ActionCA18132, supported by COST (European Cooperation in Science and Tech-nology). FCT is also acknowledged for the research contract under Scien-tific Employment Stimulus to H.O. (CEECIND/04050/2017).Open access funding provided by IReLSupporting InformationPeer reviewe