Polymersomes Eradicating Intracellular Bacteria.

Mononuclear phagocytes such as monocytes, tissue-specific macrophages, and dendritic cells are primary actors in both innate and adaptive immunity. These professional phagocytes can be parasitized by intracellular bacteria, turning them from housekeepers to hiding places and favoring chronic and/or disseminated infection. One of the most infamous is the bacteria that cause tuberculosis (TB), which is the most pandemic and one of the deadliest diseases, with one-third of the world's population infected and an average of 1.8 million deaths/year worldwide. Here we demonstrate the effective targeting and intracellular delivery of antibiotics to infected macrophages both in vitro and in vivo, using pH-sensitive nanoscopic polymersomes made of PMPC-PDPA block copolymer. Polymersomes showed the ability to significantly enhance the efficacy of the antibiotics killing Mycobacterium bovis, Mycobacterium tuberculosis, and another established intracellular pathogen, Staphylococcus aureus. Moreover, they demonstrated to easily access TB-like granuloma tissues-one of the harshest environments to penetrate-in zebrafish models. We thus successfully exploited this targeting for the effective eradication of several intracellular bacteria, including M. tuberculosis, the etiological agent of human TB.

Targeting Neutrophilic Inflammation Using Polymersome-Mediated Cellular Delivery.

Neutrophils are key effector cells in inflammation and play an important role in neutralizing invading pathogens. During inflammation resolution, neutrophils undergo apoptosis before they are removed by macrophages, but if apoptosis is delayed, neutrophils can cause extensive tissue damage and chronic disease. Promotion of neutrophil apoptosis is a potential therapeutic approach for treating persistent inflammation, yet neutrophils have proven difficult cells to manipulate experimentally. In this study, we deliver therapeutic compounds to neutrophils using biocompatible, nanometer-sized synthetic vesicles, or polymersomes, which are internalized by binding to scavenger receptors and subsequently escape the early endosome through a pH-triggered disassembly mechanism. This allows polymersomes to deliver molecules into the cell cytosol of neutrophils without causing cellular activation. After optimizing polymersome size, we show that polymersomes can deliver the cyclin-dependent kinase inhibitor (R)-roscovitine into human neutrophils to promote apoptosis in vitro. Finally, using a transgenic zebrafish model, we show that encapsulated (R)-roscovitine can speed up inflammation resolution in vivo more efficiently than the free drug. These results show that polymersomes are effective intracellular carriers for drug delivery into neutrophils. This has important consequences for the study of neutrophil biology and the development of neutrophil-targeted therapeutics.

Purification of Nanoparticles by Size and Shape.

Producing monodisperse nanoparticles is essential to ensure consistency in biological experiments and to enable a smooth translation into the clinic. Purification of samples into discrete sizes and shapes may not only improve sample quality, but also provide us with the tools to understand which physical properties of nanoparticles are beneficial for a drug delivery vector. In this study, using polymersomes as a model system, we explore four techniques for purifying pre-formed nanoparticles into discrete fractions based on their size, shape or density. We show that these techniques can successfully separate polymersomes into monodisperse fractions.

pH-sensitive tubular polymersomes: formation and applications in cellular delivery.

Optimizing the shape of a nanovector influences its interaction with a cell and determines the internalization kinetics. Block copolymer amphiphiles self-assemble into monodisperse structures in aqueous solutions and have been explored extensively as drug delivery vectors. However, the structure of self-assembled block copolymers has mainly been limited to spherical vesicles or spherical and worm-like micelles. Here we show the controlled formation and purification of tubular polymersomes, long cylindrical vesicles. Tubular polymersomes are purified from other structures, and their formation is manipulated by incorporating the biocompatible membrane components cholesterol and phospholipids. Finally we show that these tubular polymersomes have different cellular internalization kinetics compared with spherical polymersomes and can successfully encapsulate and deliver fluorescent bovine serum albumin protein intracellularly.

Chronic pravastatin but not atorvastatin treatment impairs cognitive function in two rodent models of learning and memory.

Statins are some of the most commonly prescribed drugs and are used to reduce blood cholesterol. Recent evidence suggests that, in some patients, they may adversely influence cognitive function including causing memory impairments. These clinical observations have led to statin prescriptions now including a warning about possible cognitive impairments. In order to better understand the relationship between statin treatment and cognitive function, studies in animals are needed. The present study investigated the effects of chronic treatment with two statins, pravastatin and atorvastatin, in two rodent models of learning and memory. Adult rats were treated once daily with pravastatin (10 mg/kg, orally) or atorvostatin (10 mg/kg, orally) for 18 days. Before, during and after treatment, animals were tested in a simple discrimination and reversal learning task. On the last day of treatment and following one week withdrawal, animals were also tested in a task of novel object discrimination. Pravastatin tended to impair learning over the last few days of treatment and this effect was fully reversed once treatment ceased. In the novel object discrimination task, pravastatin significantly impaired object recognition memory. No effects were observed for atorvostatin in either task. These data suggest that chronic treatment with pravastatin impairs working and recognition memory in rodents. The reversibility of the effects on cessation of treatment is similar to what has been observed in patients, but the lack of effect of atorvostatin suggests that lipophilicity may not be a major factor influencing statin-induced cognitive impairments.