Our previous research showed that a simple ultra-high-pressure process made poly(vinyl alcohol) (PVA) solution into a macrogel and nanoparticles. To investigate the release properties of PVA hydrogels prepared by the ultra-high-pressure treatment, we prepared hydrogels containing model drugs by pressurizing a PVA solution with Alfa-G Hesperidin or Oil Blue N as a water-soluble or an oil-soluble model drug, respectively. In the case of the oil-soluble drug, an oil-in-water emulsion, Oil Blue N containing dodecane in a PVA solution, was used by homogenization before pressurization. The average diameter and the diameter distribution of oil droplets before and after the ultra-high-pressure treatment were almost the same. However, the PVA hydrogel prepared at 10,000 atm for 10 min exhibited the slowest release rate of model drugs. Thus, we found that the release rates of the model drugs from the PVA hydrogels were controlled by the degree of crosslinking in the resulting gels, which was determined from the operation parameters of the ultra-high-pressure treatment, such as the pressure, time, and concentration of the PVA solution. Therefore, an ultra-high-pressure process is promising for drug-carrier development because of the nonharmful simple preparation process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Controlling the noncovalent bondings such as electrostatic interaction, van der Waals force and hydrogen bond, is the key factor to generate molecular assembly. We show that pressure is one of the most intensive variables for controlling these intermolecular forces and producing assembled structure. Macrogel and nanoparticles of hydrogen-bonded polymers were simply obtained through an ultrahigh-pressure process. The morphology of the obtained assembly depends on concentration and various conditions of the pressurization. These results indicate that the ultrahigh-pressure induces inter/intra-hydrogen bond, which is strong enough to maintain microassemblies such as gels and particles. This methodology leads to the molecular design of pressure-induced molecular assembly, and nonharmful processes for molecular separation and drug development.(C) 2008 Wiley Periodicals, Inc.

Poly(vinyl alcohol) (PVA) hydrogels interacting with DNA mediated by hydrogen bonds (PVA/DNA hydrogel) were developed using ultra-high pressure (UHP) technology. The goal was to create a new method of gene delivery by controlled release of DNA. Mixed solutions of DNA and PVA at various concentrations were pressurized at 10000 atmospheres at 37 degrees C for 10min. PVA/DNA hydrogels with good formability were produced at PVA concentrations of more than 5% w/v. The presence of DNA in the obtained hydrogels was confirmed by spectroscopic analysis and nucleic acid dye staining. DNA release from the hydrogels was investigated using PVA/DNA hydrogel samples of 5% and 10% w/v formed by UHP treatment or by conventional freeze-thaw methods. The DNA release curves from both types of samples showed a rapid phase in the initial 15 h followed by a sustained release phase. However, there was a difference in the amount of DNA released. Less DNA was released by the pressurized hydrogels than by the freeze-thaw hydrogels. Also, the cumulative amount of DNA released decreased as the PVA content in the hydrogels increased. These results indicate that DNA release from the hydrogels can be modulated by changing the preparation method and the PVA content. Furthermore, it was demonstrated that DNA release could be controlled by varying the amount and duration of pressurizing used to form the hydrogels. Intact fractions of plasmid DNA released from the hydrogels were separated by agarose gel electrophoretic analysis. These results suggest that, using controlled release, DNA from PVA/DNA hydrogels formed by UHP treatment can be transfected into cells.

Yoshiyuki Miura, Tsuyoshi Kimura, Kwangwoo Nam, Shingo Mutsuo, Hidekazu Yoshizawa, Toshiya Fujisato, Akio Kishida Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan Department of Material and Energy Science, Gradual School of Environmental Science, Okayama University, Okayama, Japan Department of Regeneration Medicine and Tissue Engineering, National Cardiovascular Center Research Institute, Osaka, Japan

Polyvinyl alcohol (PVA)–DNA nanoparticles have been developed by ultra high pressure (UHP) technology. Mixture solutions of DNA and PVA having various molecular weights (Mw) and degree of saponifications (DS) were treated under 10,000 atmospheres (981 MPa) condition at 40 °C for 10 min. Agarose gel electrophoresis and scanning electron microscope observation revealed that the PVA–DNA nanoparticles with average diameter of about 200 nm were formed. Using PVA of higher Mw and degree of saponifications, the amount of nanoparticles formed increased. The driving force of nanoparticle formation was the hydrogen bonding between DNA and PVA. In order to apply the PVA–DNA nanoparticles for gene delivery, the cytotoxicity and the cellular uptake of them were investigated using Raw264 cell lines. The cell viability was not influenced whether the presence of the PVA–DNA nanoparticles. Further, the nanoparticles internalized into cells were observed by fluorescent microscope. These results indicates that the PVA–DNA nanoparticles prepared by UHP technology showed be useful as drug carrier, especially for gene delivery.