Effective in vitro evaluation of vaccine adjuvants would allow higher throughput screening compared to in vivo studies. However, vaccine adjuvants comprise a wide range of structures and formulations ranging from soluble TLR agonists to complex lipid-based formulations. The effects of formulation parameters on in vitro bioactivity assays and the correlations with in vivo adjuvant activity is not well understood. In the present work, we employ the Limulus amebocyte lysate assay and a human macrophage cellular cytokine production assay to demonstrate the differences in in vitro bioactivity of four distinct formulations of the synthetic TLR4 agonist GLA: an aqueous nanosuspension (GLA-AF), an oil-in-water emulsion (GLA-SE), a liposome (GLA-LS), and an alum-adsorbed formulation (GLA-Alum). Furthermore, we demonstrate the importance of the localization of GLA on in vitro potency. By comparing to previous published reports on the in vivo bioactivity of these GLA-containing formulations, we conclude that the most potent activators of the in vitro systems may not be the most potent in vivo adjuvant formulations. Furthermore, we discuss the formulation considerations which should be taken into account when interpreting data from in vitro adjuvant activity assays.

Liposomes are small vesicles that can be used in various targeting applications as carrier vehicles. In this paper, we show that real-time surface plasmon resonance imaging microscopy (SPRI microscopy) can be used to detect diffraction patterns of these singular vesicles in water phase at room temperature and without any additives. The diffraction pattern intensities, related to the particle size, are shown to follow the log-normal distribution in a cumulative distribution function (CDF) that is very well in accordance with the normal size distribution of liposomes prepared with the extrusion method. In addition, this distribution is further analyzed to determine the number of gold nanoparticle (GNP) encapsulated liposomes in a set of liposomal adsorption events. Thus, we obtain the encapsulation efficiency and present a method to study the intrinsic properties of liposomes and other soft nanomaterials.

Development of lipid-based adjuvant formulations to enhance the immunogenicity of recombinant vaccine antigens is a focus of modern vaccine research. Characterizing interactions between vaccine antigens and formulation excipients is important for establishing compatibility between the different components and optimizing vaccine stability and potency. Cryogenic transmission electron microscopy (TEM) is a highly informative analytical technique that may elucidate various aspects of protein- and lipid-based structures, including morphology, size, shape, and phase structure, while avoiding artifacts associated with staining-based TEM. In this work, cryogenic TEM is employed to characterize a recombinant tuberculosis vaccine antigen, an anionic liposome formulation, and antigen–liposome interactions. By performing three-dimensional tomographic reconstruction analysis, the formation of a population of protein-containing flattened liposomes, not present in the control samples, was detected. It is shown that cryogenic TEM provides unique information regarding antigen–liposome interactions not detectable by light-scattering-based methods. Employing a suite of complementary analytical techniques is important to fully characterize interactions between vaccine components.

Ordered nanocone arrays of the electroactive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) were fabricated by the simultaneous oxygen plasma etching of an electrodeposited PEDOT thin film coated with a hexagonally closed packed polystyrene bead monolayer. PEDOT nanocone arrays with an intercone spacing of 200 nm and an average nanocone height of 350 nm exhibited a low broadband reflectivity of <1.5% from 550 to 800 nm. Electrochemical modulation of the oxidation state of the PEDOT nanocone array film was used to change both its ex situ absorption spectrum (electrochromism) and reflection spectrum (electroreflectivity). The sign of the PEDOT nanocone array electroreflectivity was opposite to that observed from unmodified PEDOT thin films; this significant difference is attributed to the unique optical behavior of nanostructured surfaces with an interfacial layer that contains a graded mix of air and highly absorptive nanocones. The combined electrochromic and electroreflective behavior of the antireflective PEDOT nanocone array films should find promising applications in solar energy cells, sensors and other optical devices.

International audienceNovel broadband ultra-antireflective surfaces were created via the electrodeposition of a nanostructured zinc oxide thin film onto conductive, light absorbing periodic nanocone arrays. Nanocone arrays of (i) fluorinated ethylene propylene (FEP) coated with a 50 nm plasmonic gold thin film and (ii) the electroactive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) exhibited a very low broadband reflectivity of less than 0.1% from 475 to 800 nm at a wide range of incident angles after the electrodeposition of a nanostructured ZnO thin film onto the surface. SEM images reveal the formation of ZnO nanoflowers and nanorods on both nanocone array surfaces; these additional ZnO nanostructures enhance the coupling of the incident visible light into the absorptive gold or PEDOT nanocones to significantly reduce the reflectivity of these surfaces. The ZnO-coated nanocone array surfaces also exhibited an enhanced photoreactivity for the oxidative degradation of methylene blue, suggesting their potential to be used as a self-cleaning antireflective surface