Modified polyethylenimines as non-viral gene delivery systems for aerosol gene therapy: investigations of the complex structure and stability during air-jet and ultrasonic nebulization.

Polyelectrolyte complexes between DNA and polyethylenimine (PEI) are promising non-viral delivery systems for pulmonary inhalation gene therapy and thus require sufficient stability during nebulization. The structure and stability of four different PEI-DNA polyplexes, namely branched (bPEI), linear (linPEI), poly(ethylene glycol)-grafted PEI (PEGPEI), biodegradable (bioPEI) PEI with DNA, were investigated. Using atomic force microscopy, the morphology of DNA and polyplexes before and after both air-jet and ultrasonic nebulization was characterized. The influence of nebulization on physico-chemical properties, particle size and zeta potential, was studied. Efficient DNA condensation to spherical particles was achieved with bPEI (90 nm) and PEGPEI (110 nm). By contrast, incomplete DNA condensations, seen as flower structures, were observed with linPEI (110 nm) and bioPEI (105 nm). Air-jet nebulization altered the polyplex structure to a greater extent than ultrasonic nebulization and resulted mainly in smaller and non-spherical particles (30-200 nm). Ultrasonic nebulization did not change the spherical structure or particle size of the polyplexes. In particular, the shape and size of the PEGPEI polyplexes did not change. We conclude that ultrasonic nebulization is a milder aerosolization method for gene delivery systems based on PEI. Additionally, PEGPEI-DNA polyplexes seem to be more stable than their counterparts, which may be advantageous in pulmonary inhalation gene therapy.

Direct atomic force microscopy observations of monovalent ion induced binding of DNA to mica.

Multivalent ions in solution are known to mediate attraction between two like-charged molecules. Such attraction has proved useful in atomic force microscopy (AFM) where DNA may be immobilized to a mica surface facilitating direct imaging in liquid. Theories of DNA immobilization suggest that either 'salt bridging' or fluctuation in the positions of counter ions about both the mica surface and DNA backbone secure DNA to the mica substrate. Whilst both theoretical and experimental evidence suggest that immobilization is possible in the presence of divalent ions, very few studies identify that such immobilization is possible with monovalent ions. Here we present direct AFM evidence of DNA immobilized to mica in the presence of only monovalent ions. Our data depict E. coli plasmid pBR322 adsorbed onto the negatively charged mica both after short (10 min) and long (24 h) incubation periods. These data suggest the need to re-explore current theories of like-charge attraction to include the possibility of monovalent interactions. We suggest that this DNA immobilization strategy may offer the potential to image natural processes with limited immobilization forces and hence enable maximum conformational freedom of the immobilized biomolecule.

Comparison of ondansetron with ondansetron plus dexamethasone in the prevention of postoperative nausea and vomiting.

The purpose of this double-blind, randomized study was to compare the effectiveness of ondansetron plus saline versus ondansetron plus dexamethasone in the prevention of postoperative nausea and vomiting. Of 180 women having general anesthesia for major gynecologic surgery, 89 received intravenous ondansetron, 4 mg, plus saline (Group 1) and 91 received intravenous ondansetron, 4 mg, plus dexamethasone 8 mg (Group 2) during their operation. A complete response, defined as no emesis and no need for rescue antiemetic during the 24-h postoperative period, occurred in 38% of patients in Group 1 and in 52% in Group 2 (P = 0.048). Emesis occurred in 34% of patients in Group 1 and in 15% in Group 2 (P = 0.003). Nausea scores were significantly lower for patients in Group 2 at 2 h (P = 0.023) and at 24 h (P = 0.001). In the ondansetron plus dexamethasone group, 9 out of 10 patients who received propofol for induction of anesthesia had no emesis. The only failure occurred in a patient who had a single emetic episode during the 24th postoperative hour. The combination of ondansetron and dexamethasone was more effective than ondansetron and saline in the prevention of postoperative nausea and vomiting for women having major gynecologic surgery.