Steve P. Armes

Internalization and biodistribution of polymersomes into oral squamous cell carcinoma cells in vitro and in vivo.

The prognosis for oral squamous cell carcinoma (OSCC) is not improving despite advances in surgical treatment. As with many cancers, there is a need to deliver therapeutic agents with greater efficiency into OSCC to improve treatment and patient outcome. The development of polymersomes offers a novel way to deliver therapy directly into tumor cells. Here we examined the internalization and biodistribution of two different fluorescently labeled polymersome formulations; polyethylene oxide (PEO)-poly 2-(diisopropylamino)ethyl methacrylate (PDPA) and poly 2-(methacryloyloxy)ethyl phosphorylcholine (PMPC)-PDPA, into SCC4 OSCC cells in vitro and in vivo. In vitro SCC4 monolayers internalized PMPC-PDPA and PEO-PDPA at similar rates. However, in vivo PMPC-PDPA polymersomes penetrated deeper and were more widely dispersed in SCC4 tumors than PEO-PDPA polymersomes. In the liver and spleen PMPC-PDPA mainly accumulated in tissue macrophages. However, in tumors PMPC-PDPA was found extensively in the nucleus and cytoplasm of tumor cells as well as in tumor-associated macrophages. Use of PMPC-PDPA polymersomes may enhance polymersome-mediated antitumor therapy.

Micellization in pH-sensitive amphiphilic block copolymers in aqueous media and the formation of metal nanoparticles.

Dynamic light scattering, potentiometric titration, transmission electron microscopy and atomic force microscopy have been used to investigate the micellar behaviour and metal-nanoparticle formation in poly(ethylene oxide)-block-poly(2-vinylpyridine), PEO-b-P2VP, poly(hexa(ethylene glycol) methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate), PHEGMA-b-PDEAEMA, and PEO-b-PDEAEMA amphiphilic diblock copolymers in water. The hydrophobic block of these copolymers (P2VP or PDEAEMA) is pH-sensitive: at low pH it can be protonated and becomes partially or completely hydrophilic leading to molecular solubility whereas at higher pH micelles are formed. These micelles consist of a P2VP or PDEAEMA core and a PEO or PHEGMA corona, respectively, where the core forming amine units can incorporate metal compounds due to coordination. The metal compounds (e.g., H2PtCl6, K2PtCl6) can either be introduced in a micellar solution, where they are incorporated within the micelle core via coordination with functional groups, or can be added to a unimer solution at low pH, where they lead to a metal-induced micellization. In these micellar nanoreactors, metal nanoparticles nucleate and grow upon reduction with sizes in the range of a few nanometers as observed by TEM. The effect of the metal incorporation method on the characteristics of the micelles and of the synthesized nanoparticles is investigated.

The involvement of microtubules and actin filaments in the intracellular transport of non-viral gene delivery system

It is known that two cytoskeleton components, microtubules and actins filaments, are required for efficient endocytosis. The relative importance of these two components in the cellular uptake of 2-(dimethylamino)ethyl methacrylate (DMAEMA)-DNA polyplexes was investigated in this study by applying microtubule depolymerising agent, colchicine, and actin polymerising inhibitor, cytochalasin D, in a cell transfection study. The effect of colchicine on transfection efficiency of polyplexes was found to be a time-dependent phenomenon, whereby the level of gene expression was inhibited at early stage, presumably to the disruption of a transport of vesicles along microtubules by colchicine. As time progressed, the level of gene expression was significantly enhanced relative to the control, possibly due to the failure in transport of vesicles from endosomes to late lysosomes, or due to the breakdown of nuclear membrane when mitosis was arrested at metaphase by colchicine. On the other hand, transfection efficiency was significantly reduced at all time points by cytochalasin D, which is considered to primarily affects invagination of vesicles at the early stage of endocytosis by inhibiting actin polymerisation. Further investigation to identify the endocytotic route of DMAEMA polyplexes was conducted applying clathrin- and caveolae- pathways inhibitors in cell transfection study. The results indicate that DMAEMA polyplexes were internalized primarily through clathrin-mediated pathway, with a minor fraction possibly entering cells via a caveolae-mediated pathway.