Structure-dynamics correlations in composite PF127-PEG-based hydrogels; cohesive/hydrophobic interactions determine phase and rheology and identify the role of micelle concentration in controlling 3D extrusion printability.

A library of composite polymer networks (CPNs) were formed by combining Pluronic F127, as the primary gelator, with a range of di-acrylate functionalised PEG polymers, which tune the rheological properties and provide UV crosslinkability. A coarse-grained sol-gel room temperature phase diagram was constructed for the CPN library, which identifies PEG-dependent disruption of micelles as leading to liquefication. Small angle X-ray scattering and rheological measurements provide detailed insight into; (i) micelle-micelle ordering; (ii) micelle-micelle disruption, and; (iii) acrylate-micelle disruption; with contributions that depend on composition, including weak PEG chain length and end group effects. The influence of composition on 3D extrusion printability through modulation of the cohesive/hydrophobic interactions was assessed. It was found that only micelle content provides consistent changes in printing fidelity, controlled largely by printing conditions (pressure and feed rate). Finally, the hydrogels were shown to be UV photo-crosslinkable, which further improves fidelity and structural integrity, and usefully reduces the mesh size. Our results provide a guide for design of 3D-printable CPN inks for future biomedical applications.

Graphene oxide modulates inter-particle interactions in 3D printable soft nanocomposite hydrogels restoring magnetic hyperthermia responses.

Hydrogels loaded with magnetic iron oxide nanoparticles that can be patterned and which controllably induce hyperthermic responses on AC-field stimulation are of interest as functional components of next-generation biomaterials. Formation of nanocomposite hydrogels is known to eliminate any Brownian contribution to hyperthermic response (reducing stimulated heating) while the Néel contribution can also be suppressed by inter-particle dipolar interactions arising from aggregation induced before or during gelation. We describe the ability of graphene oxide (GO) flakes to restore the hyperthermic efficiency of soft printable hydrogels formed using Pluronics F127 and PEGylated magnetic nanoflowers. Here, by varying the amount of GO in mixed nanocomposite suspensions and gels, we demonstrate GO-content dependent recovery of hyperthemic response in gels. This is due to progressively reduced inter-nanoflower interactions mediated by GO, which largely restore the dispersed-state Néel contribution to heating. We suggest that preferential association of GO with the hydrophobic F127 blocks increases the preponderance of cohesive interactions between the hydrophilic blocks and the PEGylated nanoflowers, promoting dispersion of the latter. Finally we demonstrate extrusion-based 3D printing with excellent print fidelity of the magnetically-responsive nanocomposites, for which the inclusion of GO provides significant improvement in the spatially-localized open-coil heating response, rendering the prints viable components for future cell stimulation and delivery applications.

The UCD nanosafety workshop (03 December 2018): towards developing a consensus on safe handling of nanomaterials within the Irish university labs and beyond - a report.

Careful handling of the nanomaterials (NMs) in research labs is crucial to ensure a safe working environment. As the largest university in Ireland, University College Dublin (UCD) has invested significant resources to update researchers working with NMs. Due to sizes often <100 nm, the NMs including nanoparticles, harbor unprecedented materialistic properties, for example, enhanced reactivity, conductivity, fluorescence, etc. which albeit conferring the NMs an edge over bulk materials regarding the applied aspects; depending on the dose, also render them to be toxic. Thus, a set of regulatory guidelines have emerged regarding safe handling of the NMs within occupational set-ups. Unfortunately, the current regulations based on the toxic chemicals and carcinogens are often confusing, lack clarity, and difficult to apply for the NMs. As a research-intensive university, a diverse range of research activities occur within the UCD labs, and it is difficult, at times impossible, for the UCD Safety, Insurance, Operational Risk & Compliance (SIRC) office to develop a set of common guidelines and cater throughout all its labs conducting research with the NMs. Hence, a necessity for dialog and exchange of ideas was felt across the UCD which encouraged the researchers including early stage researchers (e.g. PhDs, Postdocs) from multiple schools to participate in a workshop held on the 03 December 2018. The workshop tried to follow a pragmatic approach, where apart from discussing both the in vitro and in vivo scenarios, practical cases simulating situations faced frequently in the labs were discussed. This report summarizes the findings made during the workshop by this emerging critical mass in UCD.