Entrapment of Gold Nanoparticles in Liposomes for Controlled Intracellular Self-assembly

Background: Self-assembling nanomaterials (SANs) promise technological innovation at all stages of healthcare, encompassing fields of genomics, biosensors, immuno-analysis, drug delivery, detection, monitoring and treatment of diseases and infections. The generalised aim across these disciplines can be described as working towards the design of smart multifunctional nanosystems that interact, respond and provide treatment. To effectively exploit this approach, a high-level of behavioural understanding and control under biological conditions is required.Methods: Molecular recognition and electrostatic attraction, two different strategies of gold nanoparticle self-assembly were studied. Corresponding nanoparticles were incorporated into PEGylated liposomes using a novel method. Two formulations were manufactured and characterised with gold and lipid concentrations determined using analytical and microscopy techniques. Toxicity evaluation between liposomal systems and corresponding gold nanoparticles was performed in-vitro on hamster lung fibroblasts (V79), employing MTT and LDH assays. Cellular uptake and self-assembly of nanoparticles was investigated using a combination of electron microscopy and elemental analysis.Results: Both strategies facilitated spontaneous self-assembly of nanoparticles under aqueous conditions. However, within a biologically relevant medium considerable bio-complex formation occurred and only particles exploiting electrostatic interactions persisted to self-assemble. Nanoparticles were capable of being encapsulated within multilamellar liposomes by electrostatic exploiting interactions between oppositely charged components. The novel method resulted in variable internalised gold to lipid ratios, as a result of differing magnitudes of electrostatic attraction during preparation. Gold nanoparticles with cationic or anionic surfaces did not display cytotoxicity, although a significant difference in cytotoxicity was displayed as they underwent in-situ self-assembly. Liposomes with and without encapsulated gold nanoparticles exhibited significant dose-dependant cytotoxicity. Cellular internalisation of gold nanoparticles was evidenced within cellular vacuoles, although no confirmation of self-assembly was obtained.Conclusions: Nanomaterial-biological interactions preceding the process of self-assembly can hinder activity and result in unpredictable outcomes. Individual SANs can be incorporated within traditional drug delivery systems, which could be further investigated towards controlling self-assembly activity. Toxicity studies demonstrate that a unique biological response could arise when nanomaterials self-assemble. Intracellular evaluation of SANs is inherently difficult and current techniques and approaches would benefit from further development to enable routine and reliable assessment of analogous nanosystems

Preparation of liposomes containing small gold nanoparticles using electrostatic interactions

Abstract The development of liposome-nanoparticle colloid systems offers a versatile approach towards the manufacture of multifunctional therapeutic platforms. A strategy to encapsulate small metallic nanoparticles (<4nm) within multilamellar vesicles, effected by exploiting electrostatic interactions was investigated. Two liposome-gold nanoparticle (lipo-GNP) systems were prepared by the reverse-phase evaporation method employing cationic or anionic surface functionalised particles in combination with oppositely charged lipid compositions with subsequent post-formulation PEGylation. Structural characterisation using electron microscopy and elemental analysis revealed a regular distribution of GNPs between adjacent lipid bilayers of intact liposomes. Nanoparticle encapsulation efficacy of the two lipo-GNP systems was revealed to be significantly different (p=0.03), evaluated by comparing the ratio of measured lipid to gold concentration (loading content) determined by a colorimetric assay and atomic emission spectroscopy, respectively. It was concluded that the developed synthetic strategy is an effective approach for the preparation of liposome-nanoparticle colloids with potential to control the relative concentration of encapsulated particles to lipids by providing favourable electrostatic interactions

Single-layer graphenes functionalized with polyurea: architectural control and biomolecule reactivity

The nondestructive, covalent reactivity of single-layer graphene oxide (SLGO) and hydrazine-reduced graphene oxide (rGO) in relation to its 3-dimensional geometry has been previously considered for various chemical reactions. However, the capability of the modified system to undergo additional chemistry is now demonstrated through an in-situ polycondensation reaction resulting in various linear or hyperbranched condensed polymers [e.g., polyureas, polyurethanes, and poly(urea–urethane)-bonded graphenes]. The use of aliphatic diisocyanates as the anchor molecule initially forms star-like clusters of SLGO and rGO, and on in-situ polycondensation reaction with aliphatic diamines, the underlying graphene architecture is further modified into scroll-like domains with extensive intersheet bridging. The use of aromatic isocyanates as bridging molecules keeps the graphene structure flat and is maintained throughout the polycondensation reaction with aromatic diamines. Critical point drying of the graphene–polymer composites shows that changes to the architecture of the composite occur in the solution phase and not through surface tension effects on drying. According to TGA analysis, the aliphatic systems have higher grafted polymer weight proportions of polyurea than the aromatic counterparts and the rGO systems are found to be greater than the SLGO composites. In all experiments, the external surface of the graphene–polyurea macrostructure is demonstrated to be reactive toward biomolecules such as ferritin and is therefore useful toward a solution chemistry development of morphology-controlled graphene-based bio-nano applications

Synthesis and applications of copillar[5]arene dithiols

<p>A novel copillar[4+1]arene incorporating alkylthiol substituents was synthesised in three steps and structurally characterised as the first example of a pillar[n]arene to incorporate two terminal thiols on the same aromatic ring. The macrocycle was attached to gold electrodes through a standard dipping technique. Cyclic voltammetry demonstrated selectivity for Li⁺ over other alkali metal cations. The copillar[4+1]arene was also used as a capping agent in the preparation of 3 nm gold nanoparticles.</p