Biodegradable Poly(2-Dimethylamino Ethylamino)Phosphazene for In Vivo Gene Delivery to Tumor Cells. Effect of Polymer Molecular Weight

Purpose. Previously, we have shown that complexes of plasmid DNA with the biodegradable polymer poly(2-dimethylamino ethylamino)phosphazene (p(DMAEA)-ppz) mediated tumor selective gene expression after intravenous administration in mice. In this study, we investigated the effect of p(DMAEA)-ppz molecular weight on both in vitro and in vivo tumor transfection, as well as on complex induced toxicity. Materials and Methods. p(DMAEA)-ppz with a broad molar mass distribution was fractionated by preparative size exclusion chromatography. Polyplexes consisting of plasmid DNA and the collected polymer fractions were tested for biophysical properties, (cyto)toxicity and transfection activity. Results. Four p(DMAEA)-ppz fractions were collected with weight average molecular weights ranging from 130 to 950 kDa, and with narrow molecular mass distributions (Mw/Mn from 1.1 to 1.3). At polymer-to-DNA (N/P) ratios above 6, polyplexes based on these polymers were all positively charged (zeta potential 25–29 mV), and had a size of 80–90 nm. The in vitro cytotoxicity of the polyplexes positively correlated with polymer molecular weight. The in vitro transfection activity of the different polyplexes depended on their N/P ratio, and was affected by the degree of cytotoxicity, as well as the colloidal stability of the different polyplexes. Intravenous administration of polyplexes based on the high molecular weight polymers led to apparent toxicity, as a result of polyplex-induced erythrocyte aggregation. On the other hand, administration of polyplexes based on low molecular weight p(DMAEA)-ppz_s (Mw130 kDa) did not show signs of toxicity and resulted in tumor selective gene expression. Conclusion. Polymer molecular weight fractionation enabled us to optimize the transfection efficiency/ toxicity ratio of p(DMAEA)-ppz polyplexes for in vitro and in vivo tumor transfection. KEY WORDS: biodegradable; cationic polymer; DNA; molecular weight; tumor gene delivery

Enzyme promiscuity shapes adaptation to novel growth substrates

<p>Evidence suggests that novel enzyme functions evolved from low-level promiscuous activities in ancestral enzymes. Yet, the evolutionary dynamics and physiological mechanisms of how such side activities contribute to systems-level adaptations are not well characterized. Furthermore, it remains untested whether knowledge of an organism's promiscuous reaction set, or underground metabolism, can aid in forecasting the genetic basis of metabolic adaptations. Here, we employ a computational model of underground metabolism and laboratory evolution experiments to examine the role of enzyme promiscuity in the acquisition and optimization of growth on predicted non-native substrates in Escherichia coli K-12 MG1655. After as few as approximately 20 generations, evolved populations repeatedly acquired the capacity to grow on five predicted non-native substrates-D-lyxose, D-2-deoxyribose, D-arabinose, m-tartrate, and monomethyl succinate. Altered promiscuous activities were shown to be directly involved in establishing high-efficiency pathways. Structural mutations shifted enzyme substrate turnover rates toward the new substrate while retaining a preference for the primary substrate. Finally, genes underlying the phenotypic innovations were accurately predicted by genome-scale model simulations of metabolism with enzyme promiscuity.</p

Developing a Personality Model for Speech-based Conversational Agents Using the Psycholexical Approach

We present the first systematic analysis of personality dimensions developed specifically to describe the personality of speech-based conversational agents. Following the psycholexical approach from psychology, we first report on a new multi-method approach to collect potentially descriptive adjectives from 1) a free description task in an online survey (228 unique descriptors), 2) an interaction task in the lab (176 unique descriptors), and 3) a text analysis of 30,000 online reviews of conversational agents (Alexa, Google Assistant, Cortana) (383 unique descriptors). We aggregate the results into a set of 349 adjectives, which are then rated by 744 people in an online survey. A factor analysis reveals that the commonly used Big Five model for human personality does not adequately describe agent personality. As an initial step to developing a personality model, we propose alternative dimensions and discuss implications for the design of agent personalities, personality-aware personalisation, and future research.Comment: 14 pages, 2 figures, 3 tables, CHI'2

Antigen-expressing immunostimulatory liposomes as a genetically programmable synthetic vaccine

Liposomes are versatile (sub)micron-sized membrane vesicles that can be used for a variety of applications, including drug delivery and in vivo imaging but they also represent excellent models for artificial membranes or cells. Several studies have demonstrated that in vitro transcription and translation can take place inside liposomes to obtain compartmentalized production of functional proteins within the liposomes (Kita et al. in Chembiochem 9(15):2403–2410, 2008; Moritani et al.in FEBS J, 2010; Kuruma et al. in Methods Mol Biol 607:161–171, 2010; Murtas et al. in Biochem Biophys Res Commun 363(1):12–17, 2007; Sunami et al. in Anal Biochem 357(1):128–136, 2006; Ishikawa et al. in FEBS Lett 576(3):387–390, 2004; Oberholzer et al. in Biochem Biophys Res Commun 261(2):238–241, 1999). Such a minimal artificial cell-based model is ideal for synthetic biology based applications. In this study, we propose the use of liposomes as artificial microbes for vaccination. These artificial microbes can be genetically programmed to produce specific antigens at will. To show proof-of-concept for this artificial cell-based platform, a bacterial in vitro transcription and translation system together with a gene construct encoding the model antigen β-galactosidase were entrapped inside multilamellar liposomes. Vaccination studies in mice showed that such antigen-expressing immunostimulatory liposomes (AnExILs) elicited higher specific humoral immune responses against the produced antigen (β-galactosidase) than control vaccines (i.e. AnExILs without genetic input, liposomal β-galactosidase or pDNA encoding β-galactosidase). In conclusion, AnExILs present a new platform for DNA-based vaccines which combines antigen production, adjuvanticity and delivery in one system and which offer several advantages over existing vaccine formulations

Personality traits and mental disorders

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