Conjugated polymer nanoparticles are being developed for a variety of diagnostic and theranostic applications. The conjugated polymer, F8BT, a polyfluorene derivative, was used as a model system to examine the biological behavior of conjugated polymer nanoparticle formulations stabilized with ionic (sodium dodecyl sulfate; F8BT-SDS; ∼207 nm; -31 mV) and nonionic (pegylated 12-hydroxystearate; F8BT-PEG; ∼175 nm; -5 mV) surfactants, and compared with polystyrene nanoparticles of a similar size (PS200; ∼217 nm; -40 mV). F8BT nanoparticles were as hydrophobic as PS200 (hydrophobic interaction chromatography index value: 0.96) and showed evidence of protein corona formation after incubation with serum-containing medium; however, unlike polystyrene, F8BT nanoparticles did not enrich specific proteins onto the nanoparticle surface. J774A.1 macrophage cells internalized approximately ∼20% and ∼60% of the F8BT-SDS and PS200 delivered dose (calculated by the ISDD model) in serum-supplemented and serum-free conditions, respectively, while cell association of F8BT-PEG was minimal (<5% of the delivered dose). F8BT-PEG, however, was more cytotoxic (IC50 4.5 μg cm(-2)) than F8BT-SDS or PS200. The study results highlight that F8BT surface chemistry influences the composition of the protein corona, while the properties of the conjugated polymer nanoparticle surfactant stabilizer used determine particle internalization and biocompatibility profile.

The development of clinically acceptable albumin-based nanoparticle formulations for use in pulmonary drug delivery has been hindered by concerns about the toxicity of nanomaterials in the lungs combined with a lack of information on albumin nanoparticle clearance kinetics and biodistribution. In this study, the in vivo biocompatibility of albumin nanoparticles was investigated following a single administration of 2, 20, and 390 μg/mouse, showing no inflammatory response (TNF-α and IL-6, cellular infiltration and protein concentration) compared to vehicle controls at the two lower doses, but elevated mononucleocytes and a mild inflammatory effect at the highest dose tested. The biodistribution and clearance of 111In labelled albumin solution and nanoparticles over 48 h following a single pulmonary administration to mice was investigated by single photon emission computed tomography and X-ray computed tomography imaging and terminal biodistribution studies. 111In labelled albumin nanoparticles were cleared more slowly from the mouse lung than 111In albumin solution (64.1 ± 8.5% vs 40.6 ± 3.3% at t = 48 h, respectively), with significantly higher (P < 0.001) levels of albumin nanoparticle-associated radioactivity located within the lung tissue (23.3 ± 4.7%) compared to the lung fluid (16.1 ± 4.4%). Low amounts of 111In activity were detected in the liver, kidneys, and intestine at time points > 24 h indicating that small amounts of activity were cleared from the lungs both by translocation across the lung mucosal barrier, as well as mucociliary clearance. This study provides important information on the fate of albumin vehicles in the lungs, which may be used to direct future formulation design of inhaled nanomedicines.

Understanding the molecular aggregation of therapeutic agents is particularly important when applying low doses of a drug to the surface of the skin. The aim of this study was to understand how the concentration of a drug influenced its molecular aggregation and its subsequent percutaneous penetration after topical application. A model drug tetracaine was shown to form a series of different aggregates across the μM (fluorescence spectroscopy) to mM (light scattering analysis) concentration range. The aggregate formation process was sensitive to the pH of the vehicle in which the drug was dissolved (pH 4, critical aggregation concentration (CAC) - 11 μM; pH 8, CAC - 7 μM) and it appeared to have an impact upon the drug's percutaneous penetration. At pH 4, increasing the concentration of the drug in the donor solution decreased the skin permeability coefficient (Kp) of tetracaine (13.7 ± 4.3 × 10(-3)cm/h to 0.06 ± 0.02 × 10(-3)cm/h), whilst at pH 8, it increased the Kp (29.9 ± 9.9 × 10(-3)cm/h to 75.1 ± 41.7 × 10(-3)cm/h). These data trends were reproduced in a silicone membrane and this supported the notion that the more polar aggregates formed at pH 4 acted to decrease the proportion of species available to pass through the skin, whilst the more hydrophobic aggregates formed in pH 8 increased the membrane diffusing species.

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ArdA antirestriction proteins are encoded by genes present in many conjugative plasmids and transposons within bacterial genomes. Antirestriction is the ability to prevent cleavage of foreign incoming DNA by restrictionmodification (RM) systems. Antimodification, the ability to inhibit modification by the RM system, can also be observed with some antirestriction proteins. As these mobile genetic elements can transfer antibiotic resistance genes, the ArdA proteins assist their spread. The consequence of antirestriction is therefore the enhanced dissemination of mobile genetic elements. ArdA proteins cause antirestriction by mimicking the DNA structure bound by Type I RM enzymes. The crystal structure of ArdA showed it to be a dimeric protein with a highly elongated curved cylindrical shape [McMahon SA et al. (2009) Nucleic Acids Res 37, 4887-4897]. Each monomer has three domains covered with negatively charged side chains and a very small interface with the other monomer. We investigated the role of the domain forming the dimer interface for ArdA activity via sitedirected mutagenesis. The antirestriction activity of ArdA was maintained when up to seven mutations per monomer were made or the interface was disrupted such that the protein could only exist as a monomer. The antimodification activity of ArdA was lost upon mutation of this domain. The ability of the monomeric form of ArdA to function in antirestriction suggests, first, that it can bind independently to the restriction subunit or the modification subunits of the RM enzyme, and second, that the many ArdA homologues with long amino acid extensions, present in sequence databases, may be active in antirestriction. Structured digital abstractArdA and ArdA bind by molecular sieving (1, 2) ArdA and ArdA bind by cosedimentation in solution (1,2)