Dissipative Particle Dynamics Simulation On The Self-assembled Behavior In Dendrimer And Block Copolymer Systems

Dendrimers and block copolymer have important applications in everyday life, chemicalengineering, pharmaceutical, food science, as well as life science. Using DPD method toinvestigate the dendrimer-drug system and quantum dots (QDs) nanocomposites system arehelpful for us to understand the loading/release mechanism of the simulation system, whichcould provide theoretical support and guidance in design and develop novel Materials.First of all, Dissipative particle dynamics (DPD) simulation was performed toinvestigate the self-assembly dynamics process of PS-b-PEO block copolymer and QDs withdifferent emission wavelengths in aqueous solution. Four sequential transient stages werefound during the formation process of CNPs:(1) all components are randomly distributed inaqueous solution;(2) QDs disperse into the microsphere formed by block copolymer;(3)some spheres crash and form four larger aggregates;(4) the stabilization stage. Thesimulation results also showed that the composition of PS-PEO block copolymer and thevolume fraction of QDs had significant effects on the structures and size of theself-assembled micelles. When the length of PEO segment is constant, the diameter of thehydrophobic core was increased with the increase of PS segment length. When the length ofPS segment is constant, the thickness of the micelle shell was increased with the increase ofPEO segment length. Furthermore, with the increase of molecular weight of PS-b-PEO blockcopolymer, the size of self-assembled micelle was increased. The simulation results alsoshowed that different self-assembled morphologies, such as sphere, cylinder, disk-annulusetc., could be obtained by varying the volume fraction of QDs.Finally DPD method was used to investigate the loading/release mechanism ofanti-cancer drug doxorubicin (DOX) in G5-PEGpolyester dendrimer. Four sequential transientstages were found during the drug encapsulation process. Meanwhile, the simulation resultsalso showed the influence of drug content and the oil content (G5-PEGand DOX) on themorphologies of self-assembled micelles. At pH7.4(37℃), no DOX molecule was releasedfrom G5-PEG/DOX when only considered the influence of temperature increase on drugrelease. It demonstrates that the increase of system temperature (from25°C to37°C) is notthe major factor for drug release at pH7.4. At pH5, when considered the protonation of DOX and temperature increase: some pores were generated on the surface of G5-PEG/DOXmicrospheres and the aperture of the pores increased with the simulation steps increased,which leads to the increasingly exposure of DOX molecules to water. However, the drugcould not release toward the aqueous solution. It demonstrated that the protonation of DOX isnot the major factor for the drug fast release at pH5though it may facilitate the drug releaseprocess.