BONE TISSUE ENGINEERING VIA LOCAL GENE DELIVERY

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Gene delivery into mesenchymal stem cells: a biomimetic approach using RGD nanoclusters based on poly(amidoamine) dendrimers

Publication . Pandita, Deepti; Santos, José L.; Rodrigues, João; Pêgo, Ana P.; Granja, Pedro L.; Tomás, Helena

Poly(amidoamine) dendrimers (generations 5 and 6) with amine termini were conjugated with peptides containing the arginine-glycine-aspartic acid (RGD) sequence having in view their application as gene delivery vectors. The idea behind the work was to take advantage of the cationic nature of dendrimers and of the integrin targeting capabilities of the RGD motif to improve gene delivery. Dendrimers were used as scaffolds for RGD clustering and, by controlling the number of peptides (4, 8, and 16) linked to each dendrimer, it was possible to evaluate the effect of RGD density on the gene delivery process. The new vectors were characterized in respect to their ability to neutralize and compact plasmid DNA (pDNA). The complexes formed by the vectors and pDNA were studied concerning their size, zeta potential, capacity of being internalized by cells and ability of transferring genes. Transfection efficiency was analyzed, first, by using a pDNA encoding for Enhanced Green Fluorescent Protein and Firefly Luciferase and, second, by using a pDNA encoding for Bone Morphogenetic Protein-2. Gene expression in mesenchymal stem cells was enhanced using the new vectors in comparison to native dendrimers and was shown to be dependent on the electrostatic interaction established between the dendrimer moiety and the cell surface, as well as on the RGD density of nanoclusters. The use of dendrimer scaffolds for RGD cluster formation is a new approach that can be extended beyond gene delivery applications, whenever RGD clustering is important for modulating cellular responses.

2011-02-14Journal article

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Functionalization of poly(amidoamine) dendrimers with hydrophobic chains for improved gene delivery in mesenchymal stem cells

Publication . Santos, José L.; Oliveira, Hugo; Pandita, Deepti; Rodrigues, João; Pêgo, Ana P.; Granja, Pedro L.; Tomás, Helena

A new family of gene delivery vectors is synthesized consisting of a medium-size generation PAMAM dendrimer (generation 5, with amine termini) core randomly linked at the periphery to hydrophobic chains that vary in length (12 to 16 carbon alkyl chains) and number (from 4.2 to 9.7 in average). The idea subjacent to the present work is to join the advantages of the cationic nature of the dendrimer with the capacity of lipids to interact with biological membranes. Unlike other amphiphilic systems designed for the same purpose, where the hydrophobic and hydrophilic moieties coexist in opposite sides, the present vectors have a hydrophilic interior and a hydrophobic corona. The vectors are characterized in respect to their ability to neutralize, bind and compact plasmid DNA (pDNA). The complexes formed between the vectors and pDNA are analyzed concerning their size, zeta-potential, resistance to serum nucleases, capacity of being internalized by cells and transfection efficiency. These new vectors show a remarkable capacity for mediating the internalization of pDNA with minimum cytotoxicity, being this effect positively correlated with the -CH(2)- content present in the hydrophobic corona. Gene expression in MSCs, a cell type with relevancy in the regenerative medicine clinical context, is also enhanced using the new vectors but, in this case, the higher efficiency is shown by the vectors containing the smallest hydrophobic chains.

2010Journal article

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Receptor-mediated gene delivery using PAMAM dendrimers conjugated with peptides recognized by mesenchymal stem cells

Publication . Santos, José L.; Pandita, Deepti; Rodrigues, João; Pêgo, Ana P.; Granja, Pedro L.; Balian, Gary; Tomás, Helena

As mesenchymalstemcells(MSCs)candifferentiateintomultiplecelltypes,thedeliveryof exogenous genes to this type of cell can be an important tool in tissue regeneration and engineering. HowevertransfectionofMSCsusingnonviralgenedeliveryvectorsisdifﬁcult,thedevelopmentofmore efﬁcientandsafeDNAvehiclesbeingnecessary.Moreover,speciﬁctransfectionofMSCsmayberequired to avoid unwanted side effects in other tissues. In this study, a novel family of gene delivery vectors based on poly(amidoamine) (PAMAM) dendrimers functionalized with peptides displaying high afﬁnity toward MSCs was prepared. The vectors were characterized with respect to their ability to neutralize, bindandcompactplasmidDNA(pDNA).ThecomplexesformedbetweenthevectorsandpDNAwere analyzedconcerningtheirsize, -potential,capacityofbeinginternalizedbycellsandtransfectionefﬁciency. Thesenewvectorsexhibitedlowcytotoxicity,receptor-mediatedgenedeliveryintoMSCsandtransfection efﬁciencies superior to those presented by native dendrimers and by partially degraded dendrimers.

2010-06-07Journal article

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