Synthesis and self-assembly of polypeptide- and lipid-glycosylated dendron hybrids into glyconanoparticles

Abstract

Event Abstract Back to Event Synthesis and self-assembly of polypeptide- and lipid-glycosylated dendron hybrids into glyconanoparticles John F. Trant1*, Ariane Peyret2*, Colin V. Bonduelle2*, Khalid Ferji2*, Namrata Jain1*, Sebastien Lecommandoux2* and Elizabeth Gillies1, 3* 1 The University of Western Ontario, Chemistry, Canada 2 Université Bordeaux/IPB, ENSCBP, Laboratoire de Chimie des Polymères Organique, France 3 The University of Western Ontario, Chemical and Biochemical Engineering, Canada Introduction: Glycolsylated nanoparticles hold promise in targeted delivery, inhibition of viral or bacterial infection, and in immunotherapy through their ability to mimic or intercept the functions of carbohydrates in biological systems[1],[2]. Different approaches have been developed to prepare glycosylated polymer assemblies including the conjugation of glycans to preformed assemblies[3] and the formation of assemblies from macromolecules comprising carbohydrate-based hydrophilic blocks[4],[5]. Presented here is an alternative new approach involving the use of carbohydrate-functionalized dendrons as the hydrophilic block and poly(gamma-benzyl-L-glutamate) (PBLG) or distearoyl glycerol (DSG) as the hydrophobic block. Assembly of the resulting linear-dendritic copolymers into glyconanoparticles is described. Materials and Methods: The synthetic approach involved the conjugation of an azide-terminated PBLG (Figure 1)[6] or azide-functionalized DSG (Figure 2) to an alpha-galactose-functionalized dendron with a focal point alkyne. Using PBLG with degrees of polymerization (DP) of 14, 28, and 54 as well as 2nd, 3rd, and 4th generation dendrons, amphiphilies with varying hydrophilic fractions were prepared. Self-assembly was performed by a nanoprecipitation procedure involving the dissolution of the copolymer in dimethylsulfoxide (DMSO) and the addition of water to the organic solution or the rapid injection of the organic solution into water. The organic solvent was then removed by dialysis. Results and Discussion: It was found that a copolymer comprising PBLG with a DP of 28 and a 4th generation dendron with 16 peripheral galactose moieties assembled into well-defined micelles with a diameter of 20 nm when a DMSO solution was added to water, as measured by transmission electron microscopy (TEM) (Figure 3A) and 40 nm as measured by dynamic light scattering (DLS). While the sizes of these assemblies could be tuned by the addition of PBLG homopolymer or by changing the organic solvent, the assemblies tended to aggregate in salt solutions and aggregates were observed for the other copolymers. This was attributed to the competition between the tendency of the dendron to form curved interfaces between the blocks versus the tendency of PBLG to behave as a rod due to its alpha-helical structure, which favors lamellar assemblies[7]-[9]. Use of DSG as a hydrophobic block provides greater conformational flexibility and a lower hydrophobic volume fraction. Indeed, assemblies of the lipid-dendron amphiphilies were less susceptible to aggregation with the 2nd generation hybrid forming vesicles (Figure 3B) and the 3rd and 4th generation systems forming stable micelles in both water and buffer. Conclusion: A series of amphiphiles composed of hydrophobic PBLG or DSG and hydrophilic glycolsylated dendrons were synthesized and their self-assembly behavior was studied. A copolymer composed of PBLG-28 and a 4th generation dendron assembled into micelles. Lipid-dendron hybrids composed of 3rd and 4th generation dendrons provided micelles, whereas the 2nd generation system provided vesicles. These glyconanoparticles serve as new platforms for biomedical applications, in particular as immunotherapeutics due to the important role of alpha-galactose in immunostimulation and pathogenesis[10].