Researchers from the University of California and Harvard-MIT have developed a new type of biodegradable, non-toxic nanoparticle (NP) that break down readily and can be excreted via the kidneys after delivering a drug payload to the target site thereby avoiding a major drawback with some other nanoparticle delivery systems that may have limited biodegradability, toxicity issues or which are rejected immediately by the body’s immune system.

The novel NPs were formed by electrochemical etching of single-crystal silicon wafers followed by ultrasonication and filtration, yielding NPs with 5-10nm pore diameters. Silicon oxide grown onto the surfaces provides an intrinsic photoluminescence at 650-900nm which is a range where organs and tissues exhibit very low adsorption, thereby providing a mechanism for monitoring accumulation and degradation in-vivo.

In-vivo tests in a mouse model with the anti-cancer drug doxorubicin showed accumulation in a tumour followed by subsequent breakdown of the NPs, probably into soluble silicic acid, and elimination by renal clearance within 1-4 weeks of injection with no indications of toxicity.

Source: Nanowerk

Paper: Nature Materials

Posted: April 16th, 2009 under Chemistry, Nanomedicine.
Comments: none

Researchers at New York University and Harvard University have created an autonomous, bipedal DNA “walker” that can mimic a cell’s transportation system and which marks a step toward creating more complex synthetic molecular motors.

Previous versions of walkers, which are able to move along a track of DNA, were unable to function autonomously and were liable to become uncoordinated and fall off the DNA “track”.

The New York and Harvard team overcame this problem by employing two DNA “fuel strands” which worked with the walker as a catalytic unit pushing the walker along the DNA tracks. More base pairs are formed at every step and this creates the energy necessary for movement. The fuel strands bind to the track and also release the walker’s legs allowing it to take a “step”.

The researchers hope that the research may mark a step toward creating more complex synthetic molecular motors capable of carrying a cargo from one part of a cell to another.

Video animation of walker

Science paper

Source: Nanowerk

Posted: April 6th, 2009 under Chemistry, Nanomedicine.
Comments: none

While a large number of colours in nature are produced by pigments some, like the vibrant feathers of many types of birds, are instead produced by nanostructures.

An interdisciplinary team at Yale University has found that these structures, which appear sponge-like with air bubbles, form by a process of self-assembly. They compared the natural nanostructures to examples of materials undergoing phase separation in which mixtures of different materials become unstable and separate from one another. In the case of feathers, bubbles of water form in a protein-rich soup inside the living cells and are replaced by air as the feather grows forming ?-keratin and air nanostructures. The colour produced depends on the exact size and shape of the individual nanostructure.

The research provides important insights into how organisms use self-assembly of materials at the nanoscale to produce colour. The researchers are also interested in the potential technological applications of their finding to produce novel optical materials.

Publication: Soft Matter

Source: Nanowerk

Posted: April 6th, 2009 under Advanced materials, Chemistry.
Comments: none