Synthesis of polyvinyl alcohol hydrogel grafted by modified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles: characterization and doxorubicin delivery studies

During the last two decades, serious efforts have been directed towards the synthesis and coating magnetic nanoparticles for biomedical applications. Among many different types of polymeric coating materials that have been utilized in previous studies, we have selected polyvinyl alcohol (PVA). In this study, we report a novel type of magnetite nanocomposite-based PVA hydrogel. For this purpose, first, Fe₃O₄ nanoparticles were modified through hexamethylene diisocyanate (HMDI) and then PVA was modified by bromoacetyl bromide to produce bromoacetylated PVA. The modified PVA was cross-linked through various diamines such as ethylene-diamine, propylene-diamine and hexamethylenediamine. The prepared weak tridimensional PVA hydrogels were further reacted through unreacted hydroxyl groups with Fe₃O₄, modified by HMDI to form magnetite hard tridimensional hydrogels. The swelling behavior of the prepared magnetite nanocomposites were investigated and showed a fast initial swelling followed by a mild increase until attaining equilibrium. The structural, morphological, thermal and magnetic properties of the synthesized magnetite nanocomposites were confirmed by FTIR, thermal gravimetric analysis, vibrating sample magnetometer and scanning electron microscopy. The doxorubicin anti-tumor drug was loaded on a selected synthesized magnetic hydrogel and in vitro drug release studies were done in phosphate buffer solution in 37 °C.     

Genetic circuit building blocks for cellular computation,communications, and signal processing

In this paper, we review an emerging engineering discipline to programcell behaviors by embedding synthetic gene networks that performcomputation, communications, and signal processing. To accomplishthis goal, we begin with a genetic component library and a biocircuitdesign methodology for assembling these components into compoundcircuits. The main challenge in biocircuit design lies in selectingwell-matched genetic components that when coupled, reliably producethe desired behavior. We use simulation tools to guide circuitdesign, a process that consists of selecting the appropriatecomponents and genetically modifying existing components until thedesired behavior is achieved. In addition to such rational design, wealso employ directed evolution to optimize genetic circuitbehavior. Building on Nature's fundamental principle of evolution,this unique process directs cells to mutate their own DNA until theyfind gene network configurations that exhibit the desired systemcharacteristics. The integration of all the above capabilities infuture synthetic gene networks will enable cells to performsophisticated digital and analog computation, both asindividual entities and as part of larger cell communities. Thisengineering discipline and its associated tools will advance thecapabilities of genetic engineering, and allow us to harness cells fora myriad of applications not previously achievable.