Alison C. Savage

Peptide coated gold nanoparticles that bind lanthanide ions

Water soluble gold nanoparticles are coated with peptides bearing a dithiol surface active group for studies of lanthanide binding; characteristic red luminescence is observed upon europium binding to the nanoparticles.

Botulinum Neurotoxin Serotypes Detected by Electrochemical Impedance Spectroscopy

Botulinum neurotoxin is one of the deadliest biological toxins known to mankind and is able to cause the debilitating disease botulism. The rapid detection of the different serotypes of botulinum neurotoxin is essential for both diagnosis of botulism and identifying the presence of toxin in potential cases of terrorism and food contamination. The modes of action of botulinum neurotoxins are well-established in literature and differ for each serotype. The toxins are known to specifically cleave portions of the SNARE proteins SNAP-25 or VAMP; an interaction that can be monitored by electrochemical impedance spectroscopy. This study presents a SNAP-25 and a VAMP biosensors for detecting the activity of five botulinum neurotoxin serotypes (A–E) using electrochemical impedance spectroscopy. The biosensors are able to detect concentrations of toxins as low as 25 fg/mL, in a short time-frame compared with the current standard methods of detection. Both biosensors show greater specificity for their compatible serotypes compared with incompatible serotypes and denatured toxins.

Luminescent ruthenium(II) tris-bipyridyl complex caged in nanoscale silica for particle velocimetry studies in microchannels

Luminescence and imaging studies of 500 nm diameter colloidal silica stained with the transition metal complex [Ru(bpy)3Cl2], [Ru(bpy)3?SiNP], have been detailed and suggest that such particles are ideal for particle tracking velocimetry (PTV) or particle imaging velocimetry (PIV) for analysis of fluid flow in microchannels. Silica particles were synthesized using a modification to the St?ber synthesis to cage the transition metal complex within the core of the nanoscale particles. The particles [Ru(bpy)3?SiNP] exhibit luminescence at 620 nm, characteristic of the caged [Ru(bpy)3]2+?species with a lifetime of 790 ns upon excitation at 450 nm. A collection of the luminescence spectra from the images of the particles in a microchannel have the same profile as the spectra collected from solutions of [Ru(bpy)3?SiNP], confirming that the luminescence images are attributed to [Ru(bpy)3]2+?luminescence. PIV and PTV measurements from image sequences give flow velocities that match well with the theoretical velocity profile for a rectangular-sided microchannel of 100 ?m depth.

Towards a Maraviroc Long-Acting Injectable Nanoformulation

ABSTRACT Suboptimal adherence to antiretroviral (ARV) therapy can lead to insufficient drug exposure leading to viral rebound and increased likelihood of resistance. This has driven the development of long‐acting injectable (LAI) formulations which may mitigate some of these problems. Maraviroc (MVC) is an orally dosed CCR5 antagonist approved for use in patients infected with CCR5‐trophic HIV‐1. MVC prevents viral entry into host cells, is readily distributed to biologically relevant tissues and has an alternative resistance profile compared to more commonly used therapies. This makes a MVC LAI formulation particularly appealing for implementation in Pre‐Exposure Prophylaxis (PrEP). A 70wt% MVC‐loaded nanodispersion stabilised with polyvinyl alcohol (PVA) and sodium 1,4‐bis(2‐ethylhexoxy)‐1,4‐dioxobutane‐2‐sulfonate (AOT) was prepared using emulsion‐templated freeze‐drying. In vitro release rate studies revealed over a 22% decrease in MVC release rate constant across a size selective membrane compared with an aqueous solution of MVC (<5% DMSO). Pharmacokinetic studies in rats were subsequently carried out following intramuscular injection of either the nanodispersion or an aqueous MVC preparation (<5% DMSO). Results demonstrated over a 3.4‐fold increase in AUC0‐∞ (1959.71 vs 567.17ng.h ml), over a 2.6‐fold increase in MVCs terminal half‐life (t½) (140.69 vs 53.23h) and MVC concentrations present up to 10‐days. These data support development of a MVC LAI formulation with potential application in HIV therapy or prevention.

Improving maraviroc oral bioavailability by formation of solid drug nanoparticles

ABSTRACT Oral drug administration remains the preferred approach for treatment of HIV in most patients. Maraviroc (MVC) is the first in class co‐receptor antagonist, which blocks HIV entry into host cells. MVC has an oral bioavailability of approximately 33%, which is limited by poor permeability as well as affinity for CYP3A and several drug transporters. While once‐daily doses are now the favoured option for HIV therapy, dose‐limiting postural hypotension has been of theoretical concern when administering doses high enough to achieve this for MVC (particularly during coadministration of enzyme inhibitors). To overcome low bioavailability and modify the pharmacokinetic profile, a series of 70wt% MVC solid drug nanoparticle (SDN) formulations (containing 30wt% of various polymer/surfactant excipients) were generated using emulsion templated freeze‐drying. The lead formulation contained PVA and AOT excipients (MVCSDNPVA/AOT), and was demonstrated to be fully water‐dispersible to release drug nanoparticles with z‐average diameter of 728nm and polydispersity index of 0.3. In vitro and in vivo studies of MVCSDNPVA/AOT showed increased apparent permeability of MVC, compared to a conventional MVC preparation, with in vivo studies in rats showing a 2.5‐fold increase in AUC (145.33 vs. 58.71nghml−1). MVC tissue distribution was similar or slightly increased in tissues examined compared to the conventional MVC preparation, with the exception of the liver, spleen and kidneys, which showed statistically significant increases in MVC for MVCSDNPVA/AOT. These data support a novel oral format with the potential for dose reduction while maintaining therapeutic MVC exposure and potentially enabling a once‐daily fixed dose combination product.

In vitro characterisation of solid drug nanoparticle compositions of efavirenz in a brain endothelium cell line: Efavirenz uptake via the BBB

The antiretroviral drug efavirenz displays many desirable pharmacokinetic properties such as a long half‐life enabling once daily dosing but suffers from central nervous system safety issues. Various nanotechnologies have been explored to mitigate some of the limitations with efavirenz. While there has been progress in increasing the bioavailability, there has been no attempt to assess the impact of increased exposure to efavirenz on central nervous system safety. The uptake of aqueous and solid drug nanoparticle (SDN) formulations of efavirenz was assessed in the human cerebral microvessel endothelial cells/D3 brain endothelial cell line. The mechanisms of uptake were probed using a panel of transport and endocytosis inhibitors. The cellular accumulation of an efavirenz aqueous solution was significantly reduced by amantadine, but this was not observed with SDNs. The uptake of efavirenz SDNs was reduced by dynasore, but concentrations of the efavirenz aqueous solution were not affected. These data indicate that efavirenz is a substrate for transporters in brain endothelial cells (amantadine is an inhibitor of organic cation transporters 1 and 2), and formation of SDNs may bypass this interaction in favour of a mechanism involving dynamin‐mediated endocytosis.