title: Interactions between oligonucleotides and cationic polymers investigated by fluorescence correlation spectroscopy.
abstract: OBJECTIVE
  To evaluate whether fluorescence correlation spectroscopy (FCS) can be used to characterize the complexation between oligonucleotides and cationic polymers.
  
  
  METHODS
  The features of the complexes between rhodamine labeled oligonucleotides (Rh-ONs) and poly(2-dimethylamino)ethyl methacrylate (pDMAEMA), poly(ethylene glycol)-poly(ethyleneimine) (pEG-pEI), and diaminobutane-dendrimer-(NH2)64 (DAB64) were characterized by light scattering, electrophoretic mobility, electrophoresis, and FCS.
  
  
  RESULTS
  At low polymer/Rh-ON ratios, a decrease of the fluorescence of the Rh-ONs was observed on binding of the Rh-ONs to all cationic polymers. This was explained by the creation of "multimolecular complexes" in which the Rh-labels quench each other. The multimolecular complexes, which are highly fluorescent as they carry a number of Rh-ONs, resulted in high fluorescence peaks in the fluorescence fluctuation profile as measured by FCS. For pDMAEMA and DAB64, at higher polymer/Rh-ON ratios the fluorescence of the polyplexes increased, caused by the formation of "monomolecular complexes," which consist of only one Rh-ON per polymer. In the case of pEG-pEI, the fluorescence stayed constant when the polymer/Rh-ON ratio increased, so multimolecular polyplexes remained. FCS confirmed these results as the high fluorescence peaks disappeared in case of pDMAEMA/Rh-ON and DAB64/Rh-ON dispersions, but remained present for pEG-pEI/Rh-ON dispersions.
  
  
  CONCLUSIONS
  FCS seems applicable for study of the interactions between ONs and different types of cationic polymers.
authors.affiliation: Laboratory of General Biochemistry and Physical Pharmacy, Ghent University, Belgium.
authors.forename: E
authors.initials: E
authors.lastname: Van Rompaey
authors.forename: Y
authors.initials: Y
authors.lastname: Engelborghs
authors.forename: N
authors.initials: N
authors.lastname: Sanders
authors.forename: S C
authors.initials: SC
authors.lastname: De Smedt
authors.forename: J
authors.initials: J
authors.lastname: Demeester
mesh_terms: D002412:Cations / Q000737:chemistry / Q000493:pharmacokinetics; D004347:Drug Interactions; D004587:Electrophoresis, Agar Gel / Q000379:methods; D009841:Oligonucleotides / Q000737:chemistry* / Q000493:pharmacokinetics; D011108:Polymers / Q000737:chemistry* / Q000493:pharmacokinetics; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D002412:Cations; D009841:Oligonucleotides; D011108:Polymers