Hair without treatment (silver), at 1 day (gold), at 16 days (brown). Image courtesy Amercian Chemical Society.

Philippe Walter and colleagues at the Université Pierre et Marie Curie in Paris, France, have pinpointed gold nanoparticles inside human hair. Due to the different amino acids present in human hair, the researchers were able to reduce a solution of chloroauric acid to gold. The gold nanoparticles form mostly in the keratin-rich area of the hair shaft, and are arranged in a pattern of whirls like a fingerprint.

Scientists are exploring various uses, ranging from electronics and sensors to medical diagnostic tests and cancer treatments. Gold nanoparticles have already been used for drug delivery to treat certain diseases, and they have the potential for use as microelectrodes in hair.

An image shows the change of color inside the shaft under white light (A, F). Under blue light, an observable, intense red fluorescence (E) is present instead of the light green fluorescence of hair without treatment (B). Hair dyeing at different intervals of time follows (C-E). The radial development of fluorescence shows a direct correlation with formation of gold nanoparticles.

Observation of cross sections of treated hair by optical microscopy: under white light (A) and under blue light filter (B). Image courtesy American Chemical Society.

A full text version of the published research, Hair Fiber as a Nanoreactor in Controlled Synthesis of Fluorescent Gold Nanoparticles, is available at www.acs.org.

- Amber Harmon