title: Spectrophotometric determination of polyethylenimine in the presence of an oligonucleotide for the characterization of controlled release formulations.
abstract: Polyethylenimine (PEI) is a cationic polymer that can be associated to oligonuclotides to promote their transfection both in vitro and in vivo. The controlled release of oligonucleotide/polyethylenimine complexes from biodegradable systems can result in an increased cellular internalisation of the oligonucleotide and a reduced cytotoxicity of the complex. This effect strongly depends on the amount of PEI loaded in and released from the delivery system. In this work we describe a rapid, sensitive and reproducible spectrophotometric method for the quantitative analysis of PEI by itself or in the presence of an associated oligonucleotide. PEI does not possess chromophores, hence the determination by ordinary spectrophotometry is not possible. However, upon addition of copper (II) ions, PEI forms a dark blue cuprammonium complex that can be detected by UV-vis spectrophotometry. The optimum conditions in terms of optical parameters, copper (II) concentration required for a quantitative PEI complexation, and the most suitable medium for the reaction were ascertained. A linear relationship (r(2)=0.9997) between absorbance and amounts of PEI was found at lambda(max) of 285 nm over the concentration range 5.0-50.0 microg ml(-1). The detection limit (QOD) was 4.0 microg ml(-1). The method was validated for the quantitation of PEI in the presence of an oligonucleotide, which absorbs at 285 nm as well.
authors.affiliation: Dipartimento di Chimica Farmaceutica e Tossicologica, Facoltà di Farmacia, Università degli Studi di Napoli Federico II-Via Domenico Montesano 49, 80131 Napoli, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Ungaro
authors.forename: Giuseppe
authors.initials: G
authors.lastname: De Rosa
authors.forename: Agnese
authors.initials: A
authors.lastname: Miro
authors.forename: Fabiana
authors.initials: F
authors.lastname: Quaglia
mesh_terms: D000465:Algorithms; D003300:Copper / Q000737:chemistry; D003692:Delayed-Action Preparations; D005079:Excipients; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D019344:Lactic Acid; D008863:Microspheres; D009841:Oligonucleotides / Q000032:analysis*; D011094:Polyethyleneimine / Q000032:analysis*; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D012015:Reference Standards; D015203:Reproducibility of Results; D012972:Sodium Hydroxide / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003692:Delayed-Action Preparations; D005079:Excipients; D007202:Indicators and Reagents; D009841:Oligonucleotides; D011108:Polymers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D012972:Sodium Hydroxide; D003300:Copper; D011094:Polyethyleneimine