Non-lamellar lyotropic liquid crystalline nanoparticles enhance the antibacterial effects of rifampicin against Staphylococcus aureus.

The fight against infection in an era of emerging antibiotic resistant bacteria is one of the grandest scientific challenges facing society today. Nano-carriers show great promise in improving the antibacterial activity of antibiotics as they are able to enhance their solubility, provide sustained release and reduce toxic side effects via specifically targeting infection sites. Here, we investigate the antibacterial effect of two lipidic nano-carriers that contain the poorly soluble antibiotic rifampicin in their bilayers. One nanoparticle is assembled solely from the lipid monoolein, thus is neutral at physiological pH and the other contains a mixture of monoolein and the cationic lipid N-[1-(2,3-Dioleoyloxy)propyl]-N,N,N-trimethylammonium methyl-sulfate (DOTAP), thus is positively charged. Our results show that rifampicin-loaded nanoparticles reduce the minimum inhibitory concentration against Staphylococcus aureus compared to rifampicin alone, however this reduction was most pronounced for the positively charged nanoparticles. Fluorescent microscopy revealed binding of all nanoparticles to the bacteria and enhanced binding was observed for the charged nanoparticles. This suggests that the cationic lipids promote electrostatic interactions with the negatively charged bacterial membrane. Förster resonance energy transfer demonstrated that the cationic charged nanoparticles were able to fuse with bacterial membranes whilst atomic force microscopy and transmission electron microscopy revealed structural damage to the bacterial membranes caused by the nanoparticles. Significantly, we identified a concentration window in which the nanoparticles exhibited antibacterial activity while not affecting HeLa and CHO cell viability. This ability to improve the efficacy of antibiotics without affecting their eukaryotic cytotoxicity is of significant importance for future development of nanomedicine based strategies to combat infections.

Glycosylated Reversible Addition-Fragmentation Chain Transfer Polymers with Varying Polyethylene Glycol Linkers Produce Different Short Interfering RNA Uptake, Gene Silencing, and Toxicity Profiles.

Achieving efficient and targeted delivery of short interfering (siRNA) is an important research challenge to overcome to render highly promising siRNA therapies clinically successful. Challenges exist in designing synthetic carriers for these RNAi constructs that provide protection against serum degradation, extended blood retention times, effective cellular uptake through a variety of uptake mechanisms, endosomal escape, and efficient cargo release. These challenges have resulted in a significant body of research and led to many important findings about the chemical composition and structural layout of the delivery vector for optimal gene silencing. The challenge of targeted delivery vectors remains, and strategies to take advantage of nature's self-selective cellular uptake mechanisms for specific organ cells, such as the liver, have enabled researchers to step closer to achieving this goal. In this work, we report the design, synthesis, and biological evaluation of a novel polymeric delivery vector incorporating galactose moieties to target hepatic cells through clathrin-mediated endocytosis at asialoglycoprotein receptors. An investigation into the density of carbohydrate functionality and its distance from the polymer backbone is conducted using reversible addition-fragmentation chain transfer polymerization and postpolymerization modification.

Rapid expansion of pigmentation genes in penaeid shrimp with absolute preservation of function.

Crustaceans form their distinct patterns and colours through the interaction of the carotenoid astaxanthin with a protein called crustacyanin (CRCN). Presently, the expression of just two CRCN genes is thought to provide the protein subunits that combine to form the crustacyanin complex and associated carotenoid colour change from red to blue. This study aimed to explore the genetic complexity underlying the production of pigmentation and camouflage in penaeid shrimp. We isolated 35 new CRCN genes from 12 species, and their sequence analysis indicated that this gene family has undergone significant expansion and diversification in this lineage. Despite this duplication and sequence divergence, the structure of the CRCN proteins and their functional role in shrimp colour production has been strictly conserved. Using CRCN isoforms from Penaeus monodon as an example, we showed that isoforms were differentially expressed, and that subtle phenotypes were produced by the specific downregulation of individual isoforms. These findings demonstrate that our knowledge of the molecular basis of pigmentation in shrimp was overly simplistic, and suggests that multiple copies of the CRCN genes within species may be advantageous for colour production. This result is of interest for the origin and evolution of pigmentation in crustaceans, and the mechanisms by which gene function is maintained, diversified or sub-functionalized.

Polymers in the Delivery of siRNA for the Treatment of Virus Infections.

Viral diseases remain a major cause of death worldwide. Despite advances in vaccine and antiviral drug technology, each year over three million people die from a range of viral infections. Predominant viruses include human immunodeficiency virus, hepatitis viruses, and gastrointestinal and respiratory viruses. Now more than ever, robust, easily mobilised and cost-effective antiviral strategies are needed to combat both known and emerging disease threats. RNA interference and small interfering (si)RNAs were initially hailed as a "magic bullet", due to their ability to inhibit the synthesis of any protein via the degradation of its complementary messenger RNA sequence. Of particular interest was the potential for attenuating viral mRNAs contributing to the pathogenesis of disease that were not able to be targeted by vaccines or antiviral drugs. However, it was soon discovered that delivery of active siRNA molecules to the infection site in vivo was considerably more difficult than anticipated, due to a number of physiological barriers in the body. This spurred a new wave of investigation into nucleic acid delivery vehicles which could facilitate safe, targeted and effective administration of the siRNA as therapy. Amongst these, cationic polymer delivery vehicles have emerged as a promising candidate as they are low-cost and easy to produce at an industrial scale, and bind to the siRNA by non-specific electrostatic interactions. These nanoparticles (NPs) can be functionally designed to target the infection site, improve uptake in infected cells, release the siRNA inside the endosome and facilitate delivery into the cell cytoplasm. They may also have the added benefit of acting as adjuvants. This chapter provides a background around problems associated with the translation of siRNA as antiviral treatments, reviews the progress made in nucleic acid therapeutics and discusses current methods and progress in overcoming these challenges. It also addresses the importance of combining physicochemical characterisation of the NPs with in vitro and in vivo data.

A QCM-D and SAXS Study of the Interaction of Functionalised Lyotropic Liquid Crystalline Lipid Nanoparticles with siRNA.

Biophysical studies were undertaken to investigate the binding and release of short interfering ribonucleic acid (siRNA) from lyotropic liquid crystalline lipid nanoparticles (LNPs) by using a quartz crystal microbalance (QCM). These carriers are based on phytantriol (Phy) and the cationic lipid DOTAP (1,2-dioleoyloxy-3-(trimethylammonium)propane). The nonlamellar phase LNPs were tethered to the surface of the QCM chip for analysis based on biotin-neutravidin binding, which enabled the controlled deposition of siRNA-LNP complexes with different lipid/siRNA charge ratios on a QCM-D crystal sensor. The binding and release of biomolecules such as siRNA from LNPs was demonstrated to be reliably characterised by this technique. Essential physicochemical parameters of the cationic LNP/siRNA lipoplexes-such as particle size, lyotropic phase behaviour, cytotoxicity, gene silencing and uptake efficiency-were also assessed. The SAXS data show that when the pH was lowered to 5.5 the structure of the lipoplexes did not change, thus indicating that the acidic conditions of the endosome were not a significant factor in the release of siRNA from the cationic lipidic carriers.

Macromolecular Prodrugs of Ribavirin: Structure-Function Correlation as Inhibitors of Influenza Infectivity.

The requirement for new antiviral therapeutics is an ever present need. Particularly lacking are broad spectrum antivirals that have low toxicity. We develop such agents based on macromolecular prodrugs whereby both the polymer chain and the drug released from the polymer upon cell entry have antiviral effects. Specifically, macromolecular prodrugs were designed herein based on poly(methacrylic acid) and ribavirin. Structure-function parameter space was analyzed via the synthesis of 10 polymer compositions varied by molar mass and drug content. Antiviral activity was tested in cell culture against both low and high pathogenic strains of influenza. Lead compounds were successfully used to counter infectivity of influenza in chicken embryos. The lead composition with the highest activity against influenza was also active against another respiratory pathogen, respiratory syncytial virus, providing opportunity to potentially treat infection by the two pathogens with one antiviral agent. In contrast, structure-function activity against the herpes simplex virus was drastically different, revealing limitations of the broad spectrum antiviral agents based on macromolecular prodrugs.

Dual-modality NIRF-MRI cubosomes and hexosomes: High throughput formulation and in vivo biodistribution.

Engineered nanoparticles with multiple complementary imaging modalities are of great benefit to the rapid treatment and diagnosis of disease in various organs. Herein, we report the formulation of cubosomes and hexosomes that carry multiple amphiphilic imaging contrast agents in their self-assembled lipid bilayers. This is the first report of the use of both near infrared fluorescent (NIRF) imaging and gadolinium lipid based magnetic resonance (MR) imaging modalities in cubosomes and hexosomes. High-throughput screening was used to rapidly optimize formulations with desirable nano-architectures and low in vitro cytotoxicity. The dual-modal imaging nanoparticles in vivo biodistribution and organ specific contrast enhancement were then studied. The NIRF in vivo imaging results indicated accumulation of both cubosomes and hexosomes in the liver and spleen of mice up to 20h post-injection. Remarkably, the biodistribution of the nanoparticle formulations was affected by the mesophase (i.e. cubic or hexagonal), a finding of significant importance for the future use of these compounds, with hexosomes showing higher accumulation in the spleen than the liver compared to cubosomes. Furthermore, in vivo MRI data of animals injected with either type of lyotropic liquid crystal nanoparticle displayed enhanced contrast in the liver and spleen.

Comparing Gene Silencing and Physiochemical Properties in siRNA Bound Cationic Star-Polymer Complexes.

The translation of siRNA into clinical therapies has been significantly delayed by issues surrounding the delivery of naked siRNA to target cells. Here we investigate siRNA delivery by cationic acrylic polymers developed by Reversible Addition-Fragmentation chain Transfer (RAFT) mediated free radical polymerization. We investigated cell uptake and gene silencing of a series of siRNA-star polymer complexes both in the presence and absence of a protein "corona". Using a multidisciplinary approach including quantitative nanoscale mechanical-atomic force microscopy, dynamic light scattering and nanoparticle tracking analysis we have characterized the nanoscale morphology, stiffness, and surface charge of the complexes with and without the protein corona. This is one of the first examples of a comprehensive physiochemical analysis of siRNA-polymer complexes being performed alongside in vitro biological assays, allowing us to describe a set of desirable physical features of cationic polymer complexes that promote gene silencing. Multifaceted studies such as this will improve our understanding of structure-function relationships in nanotherapeutics, facilitating the rational design of polymer-mediated siRNA delivery systems for novel treatment strategies.

Amphiphilic brush polymers produced using the RAFT polymerisation method stabilise and reduce the cell cytotoxicity of lipid lyotropic liquid crystalline nanoparticles.

Self-assembled lipid lyotropic liquid crystalline nanoparticles such as hexosomes and cubosomes contain internal anisotropic and isotropic nanostructures, respectively. Despite the remarkable potential of such nanoparticles in various biomedical applications, the stabilisers used in formulating the nanoparticles are often limited to commercially available polymers such as the Pluronic block copolymers. This study explored the potential of using Reversible Addition-Fragmentation chain Transfer (RAFT) technology to design amphiphilic brush-type polymers for the purpose of stabilising phytantriol and monoolein-based lipid dispersions. The synthesised brush-type polymers consisted of a hydrophobic C12 short chain and a hydrophilic poly(ethylene glycol)methyl ether acrylate (PEGA) long chain with multiple 9-unit poly(ethylene oxide) (PEO) brushes with various molecular weights. It was observed that increasing the PEO brush density and thus the length of the hydrophilic component improved the stabilisation effectiveness for phytantriol and monoolein-based cubosomes. Synchrotron small-angle X-ray scattering (SAXS) experiments confirmed that the RAFT polymer-stabilised cubosomes had an internal double-diamond cubic phase with tunable water channel sizes. These properties were dependent on the molecular weight of the polymers, which were considered in some cases to be anisotropically distributed within the cubosomes. The in vitro toxicity of the cubosomes was assessed by cell viability of two human adenocarcinoma cell lines and haemolytic activities to mouse erythrocytes. The results showed that phytantriol cubosomes stabilised by the RAFT polymers were less toxic compared to their Pluronic F127-stabilised analogues. This study provides valuable insight into designing non-linear amphiphilic polymers for the effective stabilisation and cellular toxicity improvement of self-assembled lipid lyotropic liquid crystalline nanoparticles.

Polyanionic Macromolecular Prodrugs of Ribavirin: Antiviral Agents with a Broad Spectrum of Activity.

Macromolecular prodrugs are developed as multiarmed agents against diverse viral pathogens. Lead candidates inhibit infectivity and replication of HIV, Ebola, influenza, measles, RSV, etc-thus being broad-spectrum antiviral agents.

Lipid-PEG conjugates sterically stabilize and reduce the toxicity of phytantriol-based lyotropic liquid crystalline nanoparticles.

Lyotropic liquid crystalline nanoparticle dispersions are of interest as delivery vectors for biomedicine. Aqueous dispersions of liposomes, cubosomes, and hexosomes are commonly stabilized by nonionic amphiphilic block copolymers to prevent flocculation and phase separation. Pluronic stabilizers such as F127 are commonly used; however, there is increasing interest in using chemically reactive stabilizers for enhanced functionalization and specificity in therapeutic delivery applications. This study has explored the ability of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated with poly(ethylene glycol) (DSPE-PEGMW) (2000 Da ≤ MW ≤ 5000 Da) to engineer and stabilize phytantriol-based lyotropic liquid crystalline dispersions. The poly(ethylene glycol) (PEG) moiety provides a tunable handle to the headgroup hydrophilicity/hydrophobicity to allow access to a range of nanoarchitectures in these systems. Specifically, it was observed that increasing PEG molecular weight promotes greater interfacial curvature of the dispersions, with liposomes (Lα) present at lower PEG molecular weight (MW 2000 Da), and a propensity for cubosomes (QII(P) or QII(D) phase) at MW 3400 Da or 5000 Da. In comparison to Pluronic F127-stabilized cubosomes, those made using DSPE-PEG3400 or DSPE-PEG5000 had enlarged internal water channels. The toxicity of these cubosomes was assessed in vitro using A549 and CHO cell lines, with cubosomes prepared using DSPE-PEG5000 having reduced cytotoxicity relative to their Pluronic F127-stabilized analogues.

Colloidally stabilized magnetic carbon nanotubes providing MRI contrast in mouse liver tumors.

The use of medical imaging contrast agents may lead to improved patient prognosis by potentially enabling an earlier detection of diseases and therefore an earlier initiation of treatments. In this study, we fabricated superparamagnetic iron oxide (SPIO) nanoparticles within the inner cavity of multiwalled carbon nanotubes (MWCNTs) for the first time; thereby ensuring high mechanical stability of the nanoparticles. A simple, but effective, self-assembled coating with RAFT diblock copolymers ensured the SPIO-MWCNTs have a high dispersion stability under physiological conditions. In vivo acute tolerance testing in mice showed a high tolerance dose up to 100 mg kg(-1). Most importantly, after administration of the material a 55% increase in tumor to liver contrast ratio was observed with in vivo MRI measurements compared to the preinjection image enhancing the detection of the tumor.

Nitroxide-loaded hexosomes provide MRI contrast in vivo.

The purpose of this work was to synthesize and screen, for their effectiveness to act as T1-enhancing magnetic resonance imaging (MRI) contrast agents, a small library of nitroxide lipids incorporated into cubic-phase lipid nanoparticles (cubosomes). The most effective nitroxide lipid was then formulated into lower-toxicity lipid nanoparticles (hexosomes), and effective MR contrast was observed in the aorta and spleen of live rats in vivo. This new class of lower-toxicity lipid nanoparticles allowed for higher relaxivities on the order of those of clinically used gadolinium complexes. The new hexosome formulation presented herein was significantly lower in toxicity and higher in relaxivity than cubosome formulations previously reported by us.

A simple way to track single gold-loaded alginate microcapsules using x-ray CT in small animal longitudinal studies.

The use of alginate based microcapsules to deliver drugs and cells with a minimal host interaction is increasingly being proposed. A proficient method to track the position of the microcapsules during such therapies, particularly if they are amenable to commonly used instrumentation, would greatly help the development of such treatments. Here we propose to label the microcapsules with gold nanoparticles to provide a bright contrast on small animal x-ray micro-CT systems enabling single microcapsule detection. The microcapsules preparation is based on a simple protocol using inexpensive compounds. This, combined with the widespread availability of micro-CT apparatus, renders our method more accessible compared with other methods. Our labeled microcapsules showed good mechanical stability and low cytotoxicity in-vitro. Our post-mortem rodent model data strongly suggest that the high signal intensity generated by the labeled microcapsules permits the use of a reduced radiation dose yielding a method fully compatible with longitudinal in-vivo studies. FROM THE CLINICAL EDITOR: The authors of this study report the development of a micro-CT based tracking method of alginate-based microcapsules by incorporating gold nanoparticles in the microcapsules. They demonstrate the feasibility of this system in rodent models, where due to the high signal intensity, even reduced radiation dose is sufficient to track these particles, providing a simple and effective method to track these commonly used microcapsules and allowing longitudinal studies.

Inhibition of influenza virus in vivo by siRNA delivered using ABA triblock copolymer synthesized by reversible addition-fragmentation chain-transfer polymerization.

AIM: Influenza virus remains a major threat, with outbreaks continuing to occur. Few treatment options are available and drug resistance can emerge rapidly. New drugs that can quickly be adapted to virus mutations are needed. Several highly effective siRNAs targeting influenza that inhibit virus replication are known; however, effective delivery of these siRNAs remains a challenge. The aim of this study was to demonstrate the safety and efficacy of ABA triblock copolymer-delivered siRNA to inhibit influenza virus replication in vivo. MATERIALS & METHODS: We report on the delivery of a siRNA targeting the influenza virus in chicken embryos using an ABA triblock copolymer prepared by reversible addition-fragmentation chain-transfer polymerization, containing a central cationic block and two outer hydrophilic polyethylene glycol blocks. RESULTS: A significant reduction of virus titer was observed with the polymer/anti-influenza siRNA complexes, whereas the control with polymer/control siRNA complexes showed no effect. CONCLUSION: These data suggest that a reversible addition-fragmentation chain transfer-based siRNA delivery platform may be suitable for combating infectious diseases in vivo.

Water-dispersible magnetic carbon nanotubes as T2-weighted MRI contrast agents.

An efficient MRI T2-weighted contrast agent incorporating a potential liver targeting functionality was synthesized via the combination of superparamagnetic iron oxide (SPIO) nanoparticles with multiwalled carbon nanotubes (MWCNTs). Poly(diallyldimethylammonium chloride) (PDDA) was coated on the surface of acid treated MWCNTs via electrostatic interactions and SPIO nanoparticles modified with a potential targeting agent, lactose-glycine adduct (Lac-Gly), were subsequently immobilized on the surface of the PDDA-MWCNTs. A narrow magnetic hysteresis loop indicated that the product displayed superparamagnetism at room temperature which was further confirmed by ZFC (zero field cooling)/FC (field cooling) curves measured by SQUID. The multifunctional MWCNT-based magnetic nanocomposites showed low cytotoxicity in vitro to HEK293 and Huh7 cell lines. Enhanced T2 relaxivities were observed for the hybrid material (186 mM(-1) s(-1)) in comparison with the pure magnetic nanoparticles (92 mM(-1) s(-1)) due to the capacity of the MWCNTs to "carry" more nanoparticles as clusters. More importantly, after administration of the composite material to an in vivo liver cancer model in mice, a significant increase in tumor to liver contrast ratio (277%) was observed in T2 weighted magnetic resonance images.

The chicken TH1 response: potential therapeutic applications of ChIFN-γ.

The outcomes of viral infections are costly in terms of human and animal health and welfare worldwide. The observed increase in the virulence of some viruses and failure of many vaccines to stop these infections has lead to the apparent need to develop new anti-viral strategies. One approach to dealing with viral infection may be to employ the therapeutic administration of recombinant cytokines to act as 'immune boosters' to assist in augmenting the host response to virus. With this in mind, a greater understanding of the immune response, particularly cell mediated T-helper-1 (TH1) type responses, is imperative to the development of new anti-viral and vaccination strategies. Following the release of the chicken genome, a number of TH1-type cytokines have been identified, including chicken interleukin-12 (ChIL-12), ChIL-18 and interferon-γ ChIFN-γ), highlighting the nature of the TH1-type response in this non-mammalian vertebrate. To date a detailed analysis of the in vivo biological function of these cytokines has been somewhat hampered by access to large scale production techniques. This review describes the role of TH-1 cytokines in immune responses to viruses and explores their potential use in enhancing anti-viral treatment strategies in chickens. Furthermore, this review focuses on the example of ChIFN-γ treatment of Chicken Anemia Virus (CAV) infection. CAV causes amongst other things thymocyte depletion and thymus atrophy, as well as immunosuppression in chickens. However, due to vaccination, clinical disease appears less often, nevertheless, the subclinical form of the disease is often associated with secondary complicating infections due to an immunocompromised state. Since CAV-induced immunosuppression can cause a marked decrease in the immune response against other pathogens, understanding this aspect of the disease is critically important, as well as providing insights into developing new control approaches. With increasing emphasis on developing alternative control programs for poultry diseases, novel therapeutic strategies provide one approach. We show here that the in ovo administration of ChIFN-γ impacts the depletion of T-cell precursors during CAV infection. Therefore, it appears that ChIFN-γ may have the potential to be used as a novel therapeutic reagent to impact virus infection and alter immunosuppression caused by CAV and potentially other pathogens.

Synthesis and evaluation of degradable polyurea block copolymers as siRNA delivery agents.

Chain extension by diisocyanate condensation provides a versatile and convenient means for preparing block copolymers. We have utilized this chemistry to prepare reducible multiblock polycations for siRNA delivery. This approach, an alternative to oxidative coupling, was suitable for preparing multiblock polycations with defined molecular weight and architecture. The polymer, PEG-b-multi-(polyhexylurea-co-oligo-L-lysine)-b-PEG, was capable of electrostatically condensing siRNA to form nano-sized polyplexes across a broad compositional range. We demonstrated that the polyplexes enter the cells via endocytosis and interact with the endosome membrane leading to destabilization and hence endosome escape. Another feature of these polymers is their multiple intra-chain disulfide linkages. This enables weakening of the polyplex via chain scission within the cytosol's reductive environment. In addition to the controlled preparation of the polymer, the polyplexes were capable of delivering siRNA in vitro to silence greater than 50% green fluorescent protein expression with negligible toxicity.

Mesoporous gadolino-aluminosilicate nanoparticles as magnetic resonance imaging contrast agents.

Enhanced T1 MRI contrast was observed in mesoporous gadolinosilicates co-doped with aluminium. The effect of gadolinium and aluminium dopant concentration was explored using a high-throughput workflow. The T1 relaxivity increases with lower gadolinium and higher aluminium loadings.

The effect of RAFT-derived cationic block copolymer structure on gene silencing efficiency.

In this work a series of ABA tri-block copolymers was prepared from oligo(ethylene glycol) methyl ether methacrylate (OEGMA(475)) and N,N-dimethylaminoethyl methacrylate (DMAEMA) to investigate the effect of polymer composition on cell viability, siRNA uptake, serum stability and gene silencing. Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization was used as the method of polymer synthesis as this technique allows the preparation of well-defined block copolymers with low polydispersity. Eight block copolymers were prepared by systematically varying the central cationic block (DMAEMA) length from 38 to 192 monomer units and the outer hydrophilic block (OEGMA(475)) from 7 to 69 units. The polymers were characterized using size exclusion chromatography and (1)H NMR. Chinese Hamster Ovary-GFP and Human Embryonic Kidney 293 cells were used to assay cell viability while the efficiency of block copolymers to complex with siRNA was evaluated by agarose gel electrophoresis. The ability of the polymer-siRNA complexes to enter into cells and to silence the targeted reporter gene enhanced green fluorescent protein (EGFP) was measured by using a CHO-GFP silencing assay. The length of the central cationic block appears to be the key structural parameter that has a significant effect on cell viability and gene silencing efficiency with block lengths of 110-120 monomer units being the optimum. The ABA block copolymer architecture is also critical with the outer hydrophilic blocks contributing to serum stability and overall efficiency of the polymer as a delivery system.