title: Towards effective non-viral gene delivery vector.
abstract: Despite very good safety records, clinical trials using plasmid DNA failed due to low transfection efficiency and brief transgene expression. Although this failure is both due to poor plasmid design and to inefficient delivery methods, here we will focus on the former. The DNA elements like CpG motifs, selection markers, origins of replication, cryptic eukaryotic signals or nuclease-susceptible regions and inverted repeats showed detrimental effects on plasmids' performance as biopharmaceuticals. On the other hand, careful selection of promoter, polyadenylation signal, codon optimization and/or insertion of introns or nuclear-targeting sequences for therapeutic protein expression can enhance the clinical efficacy. Minimal vectors, which are devoid of the bacterial backbone and consist exclusively of the eukaryotic expression cassette, demonstrate better performance in terms of expression levels, bioavailability, transfection rates and increased therapeutic effects. Although the results are promising, minimal vectors have not taken over the conventional plasmids in clinical trials due to challenging manufacturing issues.
authors.affiliation: a MIT-Portugal Program.|b iBB-Institute for Bioengineering and Biosciences , Lisbon , Portugal.
authors.forename: Michaela
authors.initials: M
authors.lastname: Šimčíková
authors.affiliation: a MIT-Portugal Program.|c Department of Chemical Engineering , Massachusetts Institute of Technology , Cambridge , MA , USA.
authors.forename: Kristala L J
authors.initials: KL
authors.lastname: Prather
authors.affiliation: a MIT-Portugal Program.|c Department of Chemical Engineering , Massachusetts Institute of Technology , Cambridge , MA , USA.|d Department of Bioengineering , Instituto Superior Técnico , Lisbon , Portugal.
authors.forename: Duarte M F
authors.initials: DM
authors.lastname: Prazeres
authors.affiliation: a MIT-Portugal Program.|c Department of Chemical Engineering , Massachusetts Institute of Technology , Cambridge , MA , USA.|d Department of Bioengineering , Instituto Superior Técnico , Lisbon , Portugal.
authors.forename: Gabriel A
authors.initials: GA
authors.lastname: Monteiro
mesh_terms: D000818:Animals; D004247:DNA / Q000235:genetics; D018014:Gene Transfer Techniques; D005822:Genetic Vectors / Q000235:genetics*; D006801:Humans; D010957:Plasmids / Q000235:genetics*; D011401:Promoter Regions, Genetic; D018741:Replication Origin; D019076:Transgenes
chemical_list: D004247:DNA
keywords: DNA vaccine; gene therapy; minicircle; minimal vectors; recombination; transgene silencing