Pall Thordarson - Academia.edu (original) (raw)

Papers by Pall Thordarson

Nanoscale, 2020

Correction for ‘Non-reversible heat-induced gelation of a biocompatible Fmoc-hexapeptide in water... more Correction for ‘Non-reversible heat-induced gelation of a biocompatible Fmoc-hexapeptide in water’ by Jonathan P. Wojciechowski et al., Nanoscale, 2020, 12, 8262–8267, DOI: 10.1039/D0NR00289E.

Nanotheranostics, 2022

Lanthanide-based beta-tricalcium phosphate (β-TCP) upconversion nanoparticles are exploited as a ... more Lanthanide-based beta-tricalcium phosphate (β-TCP) upconversion nanoparticles are exploited as a non-viral vector for imaging guided-gene therapy by virtue of their unique optical properties and multi-modality imaging ability, high transfection efficiency, high biocompatibility, dispersibility, simplicity of synthesis and surface modification. Ytterbium and thulium-doped β-TCP nanoparticles (βTCPYbTm) are synthesized via co-precipitation method, coated with polyethylenimine (PEI) and functionalized with a nuclear-targeting peptide (TAT). Further, in vitro studies revealed that the nanotheranostic carriers are able to transfect cells with the plasmid eGFP at a high efficiency, with approximately 60% of total cells producing the fluorescent green protein. The optimized protocol developed comprises the most efficient βTCPYbTm/PEI configuration, the amount and the order of assembly of βTCPYbTm:PEI, TAT, plasmid DNA and the culturing conditions. With having excellent dispersibility and h...

Chemical Society Reviews, 2021

This review highlights the importance of incorporating molecular organisation, spatial configurat... more This review highlights the importance of incorporating molecular organisation, spatial configuration and handedness in biomaterial design to arrive at improved native biomolecule interactions.

Peptide Science, 2020

Peptide‐functionalized nanoparticles combine the best of both; the ability of nanoparticles to de... more Peptide‐functionalized nanoparticles combine the best of both; the ability of nanoparticles to deliver a drug “cargo” throughout the body and the ability of peptides to selectively target certain cell types or biological systems. The vast majority of peptide‐functionalized nanoparticles employ only one type of peptide, however, to truly realize the potential of these systems in medicine, nanoparticles equipped with two or even more peptide functionalities are desirable. In this review, the latest developments in dual‐peptide functionalized nanoparticles are discussed. These are categorized depending on their structure; first broadly into grafted and self‐assembled dual‐peptide‐nanoparticles with the former then subdivided further into nonconjugated, linearly conjugated and branched conjugated dual‐peptide functionalized nanoparticles. These different categories of dual‐peptide nanoparticles are then discussed with regards to the type of functional peptides used and their role in selective targeting nanomedicine.

Advanced Healthcare Materials, 2020

There is a need for improved nanomaterials to simultaneously target cancer cells and avoid non-sp... more There is a need for improved nanomaterials to simultaneously target cancer cells and avoid non-specific clearance by phagocytes. An ellipsoidal polymersome system is developed with a unique tunable size and shape property. These particles are functionalized with in-house phage-display cell-targeting peptide to target a medulloblastoma cell line in vitro. Particle association with medulloblastoma cells is modulated by tuning the peptide ligand density on the particles. These polymersomes has low levels of association with primary human blood phagocytes. The stealth properties of the polymersomes are further improved by including the peptide targeting moiety, an effect that is likely driven by the peptide protecting the particles from binding blood plasma proteins. Overall, this ellipsoidal polymersome system provides a promising platform to explore tumor cell targeting in vivo.

Polymer Journal, 2020

Factorial analysis of the interactions between three hydrogel-forming peptides based on three dif... more Factorial analysis of the interactions between three hydrogel-forming peptides based on three different biological motifs, namely, fibronectin: Fmoc-GFFRGD, collagen: Fmoc-GFFGER, and laminin: Fmoc-DDIKVAV, was conducted through rheology and live cell imaging using L929 fibroblasts. Gels were formed from each of these three peptide gelators alone and in various combinations. Cellular growth was tracked for the first 48 h in time-lapse movies by counting fluorescent nuclei and segmenting the cell area. The correlation between cell growth and the gel structure was characterized by linear regression analysis. While all peptide combinations showed good biocompatibility, the single-component Fmoc-DDIKVAV gel had the most positive effect on cell growth, while Fmoc-GFFRGD was the least biocompatible and had the lowest growth rate and cell area. Linear regression modeling demonstrated possible negative and positive interactions between Fmoc-GFFRGD*Fmoc-DDIKVAV and Fmoc-GFFRGD*Fmoc-GFFGER, respectively. No correlation was observed between gel stiffness and cellular growth. However, an increase in the strain crossover point for the elastic and loss moduli was associated with greater cell proliferation. This may indicate that elastic gels that store the work of cell deformation during cytokinesis are required for proliferation. Multicomponent hydrogel systems were formed using combinations of three self-assembled peptide based gelators with motifs inspired by fibronectin, collagen, and laminin, respectively. After a systematic study on the how the properties of hydrogels correlate with cell growth and proliferation, it was found that cell growth was significantly impacted by the hydrogels’ resistance to strain which was defined by their crossover point. This indicates that the ability of the gel to efficiently store the work of deformation during cell division is the most important factor for cellular proliferation.

Journal of Materials Chemistry B, 2020

Self-assembling short peptides have widespread applications in energy materials, tissue engineeri... more Self-assembling short peptides have widespread applications in energy materials, tissue engineering, sensing and drug delivery. In this review we discuss the effect of functional N-terminal capping groups on peptide structure and function.

Chemical Science, 2020

The mobility of hydrophobic moieties at a peptide nanofibre surface determines its suitability as... more The mobility of hydrophobic moieties at a peptide nanofibre surface determines its suitability as a scaffold for sensitive primary cells.

Chemical Society Reviews, 2019

This tutorial review summarizes recent efforts over the past decade to study the morphological tr... more This tutorial review summarizes recent efforts over the past decade to study the morphological transformation of conventionally spherical polymersomes into non-spherical polymersomes.

ChemPlusChem, 2018

A small library of short peptides is synthesized based around the repeat tetrapeptide sequence Gl... more A small library of short peptides is synthesized based around the repeat tetrapeptide sequence Gly-Val-Ala-Pro (GVAP) which is found in the hydrophobic domain of tropoelastin. Of the five peptides synthesized, four formed self-supporting hydrogels, with similar secondary structures. The ability to tune the mechanical properties of the resultant hydrogels is demonstrated, and this is understood in relation to fiber bundling. Finally, the cytotoxicity of these elastin-based short peptide hydrogels towards HeLa cells is assessed, with clear evidence that increased aromaticity of the peptide is detrimental towards cell viability.

ChemPhysChem, 2019

To investigate the role of the capping group in the solution and solid-state self-assembly of sho... more To investigate the role of the capping group in the solution and solid-state self-assembly of short peptide amphiphiles, dialanine and diphenylalanine have been linked via the N-terminus to a benzene (phenyl) and 3-naphthyl capping groups using three different methylene linkers; (CH 2)n, n = 0-4 for the benezene and 0, 1 and 2 for the naphthalene capping group). Atomic force microscopy (AFM), oscillatory rheology, circular dichroism (CD) and IR analysis have been employed to understand the properties of these peptidebased hydrogels. Several X-ray structures of these short peptide gelators give useful conformational information regarding packing. A comparison of these solid state structures with their gel state properties yielded greater insights into the process of self-assembly in short peptide gelators, particularly in terms of the important role of C•••H interactions appear to play in determining if a short aromatic peptide does form a gel or not.

Materials, 2018

Finding a cancer-selective drug that avoids damaging healthy cells and organs is a holy grail in ... more Finding a cancer-selective drug that avoids damaging healthy cells and organs is a holy grail in medical research. In our previous studies, gold-coated iron (Fe@Au) nanoparticles showed cancer selective anti-cancer properties in vitro and in vivo but were found to gradually lose that activity with storage or "ageing.” To determine the reasons for this diminished anti-cancer activity, we examined Fe@Au nanoparticles at different preparation and storage stages by means of transmission electron microscopy combined with and energy-dispersive X-ray spectroscopy, along with X-ray diffraction analysis and cell viability tests. We found that dried and reconstituted Fe@Au nanoparticles, or Fe@Au nanoparticles within cells, decompose into irregular fragments of γ-F2O3 and agglomerated gold clumps. These changes cause the loss of the particles’ anti-cancer effects. However, we identified that the anti-cancer properties of Fe@Au nanoparticles can be well preserved under argon or, better st...

Nature nanotechnology, 2018

Studying the interactions between nanoengineered materials and biological systems plays a vital r... more Studying the interactions between nanoengineered materials and biological systems plays a vital role in the development of biological applications of nanotechnology and the improvement of our fundamental understanding of the bio-nano interface. A significant barrier to progress in this multidisciplinary area is the variability of published literature with regards to characterizations performed and experimental details reported. Here, we suggest a 'minimum information standard' for experimental literature investigating bio-nano interactions. This standard consists of specific components to be reported, divided into three categories: material characterization, biological characterization and details of experimental protocols. Our intention is for these proposed standards to improve reproducibility, increase quantitative comparisons of bio-nano materials, and facilitate meta analyses and in silico modelling.

Journal of the American Chemical Society, Feb 28, 2018

It remains challenging to program soft materials to show dynamic, tunable time-dependent properti... more It remains challenging to program soft materials to show dynamic, tunable time-dependent properties. In this work, we report a strategy to design transient supramolecular hydrogels based on kinetic control of competing reactions. Specifically, the pH-triggered self-assembly of a redox-active supramolecular gelator, N,N'-dibenzoyl-l-cystine (DBC) in the presence of a reducing agent, which acts to disassemble the system. The lifetimes of the transient hydrogels can be tuned simply by pH or reducing agent concentration. We find through kinetic analysis that gel formation hinders the ability of the reducing agent and enables longer transient hydrogel lifetimes than would be predicted. The transient hydrogels undergo clean cycles, with no kinetically trapped aggregates observed. As a result, multiple transient hydrogel cycles are demonstrated and can be predicted. This work contributes to our understanding of designing transient assemblies with tunable temporal control.

Food Chemistry, 2017

The sweetest tasting molecule known is the protein thaumatin, first isolated from the katemfe fru... more The sweetest tasting molecule known is the protein thaumatin, first isolated from the katemfe fruit, Thaumatococcus daniellii. Thaumatin is used in the food and beverage industry as a low-calorie sugar substitute. Thaumatin interacts with taste receptors in the oral cavity eliciting a persistent sweet taste and a bitter, liquorice flavor. Recombinant thaumatin was expressed in Pichia pastoris and through a coexpression strategy with a molecular chaperone, yields of one engineered thaumatin variant increased by greater than twofold. A detailed purification strategy for thaumatin is reported resulting in a homogenous sample recovered at a yield of 42%. The recombinant thaumatins were extensively characterised using size exclusion chromatography for homogeneity, reversed-phase HPLC for purity (99%), peptide digest LC-MS/MS for sequence determination, and circular dichroism and tryptophan fluorescence spectroscopies for conformational characterisation. These new thaumatin variants are amenable for bioconjugation, providing chemical biology tools for thaumatin:taste receptor interaction studies.

ChemPlusChem, 2016

In this study, we synthesized two peptide derived low molecular weight gelators bearing different... more In this study, we synthesized two peptide derived low molecular weight gelators bearing different capping groups (Fmoc and phenothiazine) and characterized their gel networks. We find that the variation of the N-terminal capping group effects the viability of these hydrogels as a three-dimensional cell culture for multicellular tumor spheroids. The results from this study indicate that the phenothiazine capping group is a more biocompatible alternative to the widely used Fmoc moiety.

Chemical communications (Cambridge, England), Jan 25, 2016

Data analysis is central to understanding phenomena in host-guest chemistry. We describe here rec... more Data analysis is central to understanding phenomena in host-guest chemistry. We describe here recent developments in this field starting with the revelation that the popular Job plot method is inappropriate for most problems in host-guest chemistry and that the focus should instead be on systematically fitting data and testing all reasonable binding models. We then discuss approaches for estimating uncertainties in binding studies using case studies and simulations to highlight key issues. Related to this is the need for ready access to data and transparency in the methodology or software used, and we demonstrate an example a webportal () that aims to address this issue. We conclude with a list of best-practice protocols for data analysis in supramolecular chemistry that could easily be translated to other related problems in chemistry including measuring rate constants or drug IC50 values.

Chemical Society reviews, Jan 29, 2017

This tutorial review summarises different aspects of cooperativity in supramolecular complexes. W... more This tutorial review summarises different aspects of cooperativity in supramolecular complexes. We propose a systematic categorisation of cooperativity into cooperative aggregation, intermolecular (allosteric) cooperativity, intramolecular (chelate) cooperativity and interannular cooperativity and discuss approaches to quantify them thermodynamically using cooperativity factors. A brief summary of methods to determine the necessary thermodynamic data is given with emphasis on isothermal titration calorimetry (ITC), a method still underrepresented in supramolecular chemistry, which however offers some advantages over others. Finally, a discussion of very few selected examples, which highlight different aspects to illustrate why such an analysis is useful, rounds up this review.

Australian Journal of Chemistry, 2017

With the recent developments in cell cultures and biomimetic materials, there is growing evidence... more With the recent developments in cell cultures and biomimetic materials, there is growing evidence indicating that long-established two-dimensional (2D) cell culture techniques are slowly being phased out and replaced with three-dimensional (3D) cell cultures. This is due to the 3D cell cultures better mimicking the natural extracellular matrix (ECM) where cells are found. The emergence of self-assembled hydrogels as an ECM mimic has revolutionised the field owing to their ability to closely simulate the fibrous nature of the ECM. Here, we review recent progress in using hydrogels as biomimetic materials in 3D cell cultures, particularly supramolecular peptide hydrogels. With greater comprehension of the behaviour of cells in these hydrogels, a cell culture system that can be used in a wide array of 3D culture-based applications can be developed.