Hydrophobicity Switching on Nanoscale and its Applications.

Sergei N. Smirnov, New Mexico State University, DMR 0900238

Hydrophobicity is a fundamental property that is responsible for numerous physical and biophysical aspects of molecular interactions in water. Behavior of water in sub micrometer and nanometer size hydrophobic structures is peculiar and can be utilized in various appli-cations, often mimicking natural phenomena.

Our research group at NMSU has recently demonstrated that the two states of hydro-phobic nanopores in water, dry and wet, can be manipulated not only by pressure but also by voltage. Even though the wet state is ther-modynamically unstable, we showed for the first time that voltage–induced gating in short nanopores can be realized in a reversible manner through electrowetting of inner walls of the nanopores, opposite to long nanopores.

A. Pressure induced wetting of hydrophobic pores that becomes reversible only with pore narrowing.

B, C. Voltage gating in short hydropho-bic nanopores.

D. pH sensitive membrane opens upon lowering pH to 5.

E. Hydrophobic nanotubes release cargo via hydrophobicity switching

We also have succeeded in realization of hydrophobicity switching induced by phospholipids or by pH, applicable in drug delivery systems, where hydrophobic nanopores yield to water intrusion due decoration by phospholipids of the cell membrane or due a drop of pH. In the first mechanism, the cargo release into cytosol can proceed without endocytosis.

Prof. Sergei Smirnov has mentored numerous students and researchers over the past 3 years work on hydrophobic nanopores, many of them from minority groups. Some pictures of students worked in the lab are shown: Fabian is from Columbia (now a postdoc at UNMC), Areen is from Jordan (mother of three), Daniel was a MARC (minority access to research). Highlights of outreach activities include:• Provided high-school teachers and students with online activities, such chemistry exercises for projects in their classrooms and at home: web.nmsu.edu/~snsm/classes/ exercises• Judged at science fairs and Chemical Olympics for high school students.

ACS Sponsored New Mexico High School Chemical Olympics

Recent graduate, currently a technician: Jessica Curtiss

Graduate Students:, Fabian Rios (now a postdoc at UNMC) and Areen KhattabiUndergraduate Students:, Daniel Mendez (not shown)

Hydrophobicity Switching on Nanoscale and its Applications.

Sergei N. Smirnov, New Mexico State University, DMR 0900238