Researchers develop new drug release mechanism utilizing 3-D superhydrophobic materials

The study was electronically published on January 16, 2012 in the Journal of the American Chemical Society.

Boston University (BU) graduate student Stefan Yohe, under the mentorship of Mark Grinstaff , PhD, BU professor of biomedical engineering and chemistry, and Yolonda Colson, MD, PhD, director of the Dana-Farber Cancer Institute/Brigham and Women's Hospital (BWH) Cancer Center, prepared drug-loaded superhydrophobic meshes from biocompatible polymers using an electrospinning fabrication method.

By monitoring drug release in aqueous solution and mesh performance in cytotoxicity assays, the team demonstrated that the rate of drug release correlates with the removal of the air pocket within the material, and that the rate of drug release can be maintained over an extended period.

"The ability to control drug release over a 2-3 month period is of significant clinical interest in thoracic surgery with applications in pain management and in the prevention of tumor recurrence after surgical resection," said Colson. Colson is also a thoracic surgeon at BWH with an active practice focused on the treatment of lung cancer patients.

This approach along with the design requirements for creating 3D superhydrophobic drug-loaded materials, the authors write, should facilitate further exploration and evaluation of these drug delivery materials in a variety of cancer and non-cancer applications.

Provided by Brigham and Women's Hospital

Novel polymers release their drug cargo in response to body temperature

Yiyan Yang and Jeremy Tan from the A*STAR Institute of Bioengineering and Nanotechnology, working in collaboration with researchers from the IBM Almaden Research Center and Stanford University in the USA, have reported the preparation of biodegradable, water-soluble polymers that can be loaded with the cancer drug Paclitaxel and injected directly into tumor tissues. Warming to body temperature causes the release of the therapeutic cargo with the system showing improvement in killing cancer cells over treatment with the drug alone.

Rather than being made from repeating units of a single monomer, the polymers described are a type of block copolymer—a polymer with one block that contains hydrophilic and hydrophobic groups and another block that contains hydrophobic groups. It is through the careful balance between these groups that the temperature-responsive property of the polymer is achieved.

To make the copolymers, Yang and co-workers used the process of living polymerization, which allows the polymer chains to keep growing until the supply of monomer is exhausted. When more monomers are added, polymerization will restart. The approach allows polymers with different sized blocks of hydrophilic and hydrophobic groups to be built easily to optimize the properties. It also results in polymers with a narrow distribution of molecular weights—an important factor in producing polymers with consistent properties throughout a sample.

Thermoresponsive polymers have been studied before, with one of the most intensively investigated being poly(N-isopropylacrylamide) (PNIPAAm), which was first synthesized in the 1950s. The critical difference in the new polymers described by Yang and co-workers is that they are both non-toxic and biodegradable. “After these polymers performed their task of delivering their important cargos, they should break down and be excreted without significant additional side effects,” says Yang. “We are now planning to further work with the IBM Almaden Research Center and other industrial partners to evaluate the in vivo toxicity and efficacy of this system for the delivery of therapeutics.”

More information: Research article in Biomaterials

Provided by Agency for Science, Technology and Research (A*STAR)

Progress toward smell television: Targeted release of various scents from individually addressable chambers

 3-D movies, Dolby surround for a more realistic audio experience -- virtual reality is on the march. And how much more realistic would a film be if a barbecue actually smelled of grilled meat or if you could smell a sea breeze when the protagonist takes his love for an evening stroll on the beach? This type of smell experience may become reality for the home television viewer in the not-too-distant future.

In the journal Angewandte Chemie, a team led by Jongmin Kim at Samsung Electronics in Korea and Sungho Jin at the University of California, San Diego, USA, have now introduced a new approach for making a compact device that could fit on the back of a television to produce thousands of different scents.

Previous technologies for the controlled release of scents were not simple enough and were much too crude for the sensitive electronics of our televisions and video players. An odor module needs to be small and robust and deliver results that are reproducible over multiple cycles; the response should be rapid and the user should be able to regulate the strength of the odor. Kim, Jin, and their co-workers aim to overcome these challenges with their new concept.

Their method is based on an array of individual cells that are filled with scent-containing solutions. The miniature containers are made from a cross-linked silicone polymer. Except for a tiny hole in the top, they are completely sealed. A needle can be sued to inject a different scent solution into each cell. In the “off” state the tiny hole stays closed. The scent containers are switched on by heating. This causes the silicone to expand and the pressure on the inside to increase, forcing a small amount of gas-phase scent out of the tiny hole.

A two-dimensional lattice of heating wires, known as an X-Y matrix, can be used to specifically address individual containers. The scientists prepared a prototype, which they successfully tested with two different perfumes, “Live by Jenifer Lopez” and “Passion by Elizabeth Taylor”. Testers could detect both scents and differentiate between them.

“Our new concept is not only of interest for the entertainment industry,” state Kim and Jin, “it could also be used for combinatorial studies of gas-phase reactions and the development of vapor-based pharmaceuticals.”

More information: Sungho Jin, An X–Y Addressable Matrix Odor-Releasing System Using an On–Off Switchable Device, Angewandte Chemie International Edition, http://dx.doi.org/ … ie.201102759

Provided by Wiley (news : web)

Caught red-handed: Detection of latent fingerprints through release of fluorescein from a nanofiber mat

When a forensic agent dusts a surface with powder or exposes it to the vapors of an iodine chamber, mystery fans know what is going on: This is how latent fingerprints are made visible so that they can be compared to those of a suspect. Su Chen and a team at Nanjing University of Technology have now developed a new process for especially rapid and simple detection of fingerprints. As the Chinese researchers report in the journal Angewandte Chemie, all it takes is a special nanofiber mat that is pressed onto the suspect surface and briefly treated with hot air -- the fingerprints appear as red ridge patterns.

When we touch a surface, tiny traces of perspiration and oils stay behind, mirroring the ridge patterns on our fingertips. There are now a number of different methods to make these latent fingerprints visible. The new method is significantly faster than the classic technique of dusting with powder. Unlike spectroscopic methods, it does not require complex technical instruments, and problematic chemicals like ninydrin are not needed either. In addition, it is suitable for all types of surfaces: by lightly pressing the mat onto the surface, the researchers were able to reliably transfer fingerprints from a wide variety of materials, including steel, quartz, glass, plastic, marble, and wood.

The secret of their success is the special mat, a fleece made from nanofibers of thermoplastic polyurethane and fluorescein, a dye. The mat is made in a process called electrospinning. When the mat comes into contact with a fingerprint, components of the perspiration react with the polyurethane, causing cross-linking of the polymer chains. The hot air accelerates the reaction. In the cross-linked regions, the fluorescein cannot remain within the fibers so it comes out as a powdery solid. However, the dye only fluoresces when it is very finely dispersed in the nanofibers, not when it is in small solid clumps. This causes the color of the mat to change from straw yellow to red, making the fingerprint visible within 30 seconds in daylight. The method only works with nanofibers, because only they have enough surface area to produce a visible reaction.

The mat can identify more than mere fingerprints. The researchers were able to "print" an image of a small dragon onto the mat by using an ink-jet printer. Their ink was simply water, which can also cause the cross-linking reaction. The combination of ink-jet printing and the release of a chemical from a nanofiber mat could also be used to produce miniaturized systems such as sensors, microreactors, and diagnostic chips.

More information: Su Chen, et al., A Release-Induced Response for the Rapid Recognition of Latent Fingerprints and Formation of Inkjet-Printed Patterns, Angewandte Chemie International Edition 2011, 50, No. 16, 3706–3709, Permalink to the article: http://dx.doi.org/ … ie.201006537

Provided by Wiley (news : web)