Sponges, Abalone Shells Provide Living Models for Nanoscientists

By GAIL GALLESSICH

"Nature was nano before nano was cool," wrote Henry Fountain in a recent New York Times article on the proliferation of nanotechnology research. No one is more aware of this than molecular biologist Dan Morse. His UCSB research groups have been studying the ways that nature builds ocean organisms on the nanoscale for over 10 years.

For example, they have studied the abalone shell for its high-performance, super-resistant, composite mineral structure. Now they are looking to learn new biotechnological routes to make high performance electronic and optical materials.

"We are now learning how to harness the biomolecular mechanism that directs the nanofabrication of silica in living organisms," says Morse. "This is to learn to direct the synthesis of photovoltaic and semiconductor nanocrystals of titanium dioxide, gallium oxide, and other semiconductors—materials with which nature has never built structures before."

Morse directs the new Institute for Collaborative Biotechnologies, a UCSB-led initiative funded by a grant of $50 million from the Army Research Office, which operates in partnership with MIT and Caltech.

Recently, Morse and his students have made advances in copying the way marine sponges construct skeletal glass needles at the nanoscale. The research group is using nature's example to produce semiconductors and photovoltaic materials in an environmentally benign way.

"Sponges are abundant here offshore and they provide a uniquely tractable model system that opens the paths to the discovery of the molecular mechanism that governs biological synthesis from silicon," says Morse. "The sponge produces copious quantities of fiberglass needles made from silicon and oxygen."

The work is particularly exciting, according to Morse, because silicon has been called the most important element on the planet technologically—silicon chips are fundamental components of computers, telecommunications devices, and in combination with oxygen form fiber optics.

His research group discovered that the center of the sponge's fine glass needles contains a filament of protein that controls the synthesis of the needles. By cloning and sequencing the DNA of the gene that codes for this protein, they discovered that the protein is an enzyme that acts as a catalyst.

Never before had a protein been found to serve as a catalyst to promote chemical reactions to form the glass or a rock-like material of a biomineral. From that discovery, the research group learned that this enzyme actively promotes the formation of the glass while simultaneously serving as a template to guide the shape of the growing mineral (glass) that it produces.

"Most recently in this research, we've discovered that these activities can be applied to the synthesis of valuable semiconductors, metal oxides, such as titanium and gallium, that have photovoltaic and semiconductor properties," says Morse.