Geoffry Laufersky’s research while affiliated with Victoria University of Wellington and other places

Climate change necessitates the need for new renewable energy technologies. Luminescent solar concentrators (LSCs) could decrease the cost of solar photovoltaic (PV) systems. However highly fluorescent dyes suffer from high levels of reabsorption, compounding losses. We explore the covalent attachment of three organic chromophore ligands (an anthracene carboxylic acid and two perylene diimide carboxylic acids) to silicon dioxide nanoparticles. This allows us to study inter-ligand energy transfer when attached to SiO2 nanoparticles, since these cannot couple to the wide-bandgap silicon dioxide, creating a simple system with a large ratio of donors to acceptors – reducing reabsorption. Using steady-state and transient spectroscopy measurements we quantify this energy transfer between ligands. We show a maximum transfer efficiency of 30% and measure the 2D diffusion length of anthracene carboxylic acid on SiO2 to be between 0.6 and 2.2 nm. This study proves the feasibility of a new approach to increasing LSC efficiency with cheap and scalable chemistry.

Indium phosphide quantum dots (QDs) passivated with zinc sulphide in a core/shell architecture (InP/ZnS) with different surface chemistries were introduced to RAW 264.7 murine “macrophage-like” cells to understand their potential toxicities. The InP/ZnS quantum dots were conjugated with an oligonucleotide, a carboxylic acid, or an amino-polyethylene glycol ligand, and cell viability and cell proliferation were investigated via a metabolic assay. Membrane integrity was measured through the production of lactate dehydrogenase. Fluorescence microscopy showed cellular uptake. All quantum dots exhibited cytotoxic behaviour less than that observed from cadmium- or lead-based quantum dots; however, this behaviour was sensitive to the ligands used. In particular, the amino-polyethylene glycol conjugated quantum dots proved to possess the highest cytotoxicity examined here. This provides quantitative evidence that aqueous InP/ZnS quantum dots can offer a safer alternative for bioimaging or in therapeutic applications.

Quantum dots are attractive alternatives to organic fluorophores for the purposes of fluorescent labeling and the detection of biomarkers. They can also be made to specifically target a protein of interest by conjugating biomolecules, such as antibodies. However, the majority of the fluorescent labeling using quantum dots is done using toxic materials such as cadmium or lead due to the well-established synthetic processes for these quantum dots. Here, we demonstrate the use of indium phosphide quantum dots with a zinc sulfide shell for the purposes of labeling and the detection of exosomes derived from the THP-1 cell line (monocyte cell line). Exosomes are nano-sized vesicles that have the potential to be used as biomarkers due to their involvement in complex cell processes. However, the lack of standardized methodology around the detection and analysis of exosomes has made it difficult to detect these membrane-containing vesicles. We targeted a protein that is known to exist on the surface of the exosomes (CD63) using a CD63 antibody. The antibody was conjugated to the quantum dots that were first made water-soluble using a ligand-exchange method. The conjugation was done using carbodiimide coupling, and was confirmed using a range of different methods such as dynamic light scattering, surface plasmon resonance, fluorescent microscopy, and Fourier transform infrared spectroscopy. The conjugation of the quantum dot antibody to the exosomes was further confirmed using similar methods. This demonstrates the potential for the use of a non-toxic conjugate to target nano-sized biomarkers that could be further used for the detection of different diseases.

Research over the past decade has identified several of the key limiting features in multidrug resistance (MDR) cancer ther-apy applications, such as evolving glycoprotein receptors at the surface of the cell that limit therapeutic uptake, metabolic changes leading to protection from multidrug resistant mediators by enhanced degradation or efflux of therapeutics, and difficulty ensuring retention of intact and functional drugs once endocytosed. Nanoparticles have been demonstrated to be effective delivery vehicles for a plethora of therapeutic agents and, in the case of nucleic acid-based agents, they provide protective advantages. Functionalizing cell penetrating peptides (CPPs), also known as protein transduction domains, onto the surface of a fluorescent quantum dots creates a labelled delivery package to investigate the nuances and difficulties of drug transport in MDR cancer cells for potential future clinical applications of diverse nanoparticle therapeutic delivery strategies. In this study, eight distinct cell penetrating peptides were used (CAAKA, VP-22, HIV-TAT, Ku-70, and hCT(9-32), integrin-β3, HIV-gp41, and K-FGF) to examine the different cellular uptake profiles in cancer versus drug resistant melano-ma (A375 & A375-R), mesothelioma (MSTO & MSTO-R), and glioma (rat 9L & 9L-R, and human U87 & LN18), cell lines. The results of this study demonstrate that cell penetrating peptide uptake varies with the amount of drug resistance and cell type, likely due to changes in cell surface markers. This study provides insight to developing functional nanoplatform deliv-ery systems in drug resistant cancer models.

The synthesis of colloidal indium phosphide quantum dots (InP QDs) has always been plagued by difficulties arising from limited P3− sources. Being effectively restricted to the highly pyrophoric tris(trimethylsilyl) phosphine (TMS3P) creates complications for the average chemist and presents a significant risk for industrially scaled reactions. The adaptation of tris(dialkylamino) phos- phines for these syntheses has garnered attention, as these new phosphines are much safer and can generate nanoparticles with competitive photoluminescent properties to those from (TMS)3P routes. Until now, the reaction mechanics of this precursor were elusive due to many experimental optimizations, such as the inclusion of a high concentration of zinc salts, being atypical of previous InP syntheses. Herein, we utilize density functional theory calculations to outline a logical reaction mechanism. The aminophosphine precursor is found to require activation by a zinc halide before undergoing a disproportionation reaction to self-reduce this P(III) material to a P(-III) source. We use this understanding to adapt this precursor for a two-pot nanoparticle synthesis in a nonco- ordinating solvent outside of glovebox conditions. This allowes us to generate spherical InP/ZnS nanoparticles possessing fluorescent quantum yields >55% and lifetimes as fast as 48 ns, with tunable emission according to varying zinc halide acidity. The development of high quality and efficient InP QDs with this safer aminophosphine under simple Schlenk environments will enable a broader range of researchers to synthesize these nontoxic materials for a variety of high-value applications.