Nanoparticle initiative to tackle safety fears

Paul Boughton

Sean Ottewell reports on how the concerns over the safety of nanoparticles has prompted a major research project into their potential hazards. At the same time theyy continue to offer exciting new opportunities for chemical companies.

The latest move to improve our understanding of nanoparticles is being made by the US National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health. The organisation is increasing investment in understanding the potential health, safety and environmental issues related to tiny particles that are used in many everyday products such as sunscreens, cosmetics and electronics. It will award about US$13million over two-years to bolster its ongoing research portfolio in the area of engineered nanomaterials (ENMs).

"We currently know very little about nanoscale materials' effect on human health and the environment," said Linda Birnbaum, director of the NIEHS and the US National Toxicology Programme (NTP). "Nanomaterials come in so many shapes and sizes, with each one having different chemical properties and physical and surface characteristics. They are tricky materials to get a handle on. The same properties that make nanomaterials so potentially beneficial in drug delivery and product development are some of the same reasons we need to be cautious about their presence in the environment."

The new awards focus on ensuring that we have reliable and reproducible methods and models to assess exposure, exposure metrics, and biological response to nanomaterials. This research is also essential for the harmonisation of research results and forming a scientifically sound basis for hazard assessment, as well as the safe design and development of ENMs.

"There are inconsistencies in the biological effects of ENMs reported in the scientific literature, and a major reason for this is lack of detailed characterisation of the physical and chemical properties of the ENMs used in these studies," said Sri Nadadur, programme administrator at the NIEHS. "One of our goals is to identify three or four reliable and reproducible test methods using the same ENMs by investigators across different labs."

Meanwhile, the International Council of Chemical Associations (ICCA) is supporting the OECD's extensive work to improve global understanding towards the responsible development of nanotechnology. As such it is working with a number of different stakeholders including the OECD, the International Chamber of Commerce, the NanoBusiness Alliance, academia and NGOs on related programmes.

"These efforts will help to evaluate and develop EHS-related issues, identify common priorities for responsible innovation, evaluate and address potential risks, and develop reporting programmes," it says (Fig. 1).

Nevertheless, for chemical companies, nanotechnologies remain an important area of research and investment. For example BASF Venture Capital has invested in the US start-up company NanoMas Technologies which develops inks containing silver nanoparticles that are easily processed to electrical circuits in printed electronics, solar cells and special adhesives. NanoMas will use the funds to expand its nanoparticle production capacity, invest further in R&D, and to support the marketing of its silver inks.

The US start-up's silver nanoparticles are suitable for use in transistors, conductors and semiconductors. Silver is highly conductive and functions better than other metals under oxidative conditions. The NanoMas chemical process enables the silver nanoparticles to be processed at low temperatures, thereby increasing efficiency and lowering cost.

The process is also ideal for printing electronics on temperature-sensitive materials such as paper and plastics. Printed electronics is the basis for developing enhanced performance printed labels - radio frequency identification (RFID) - which can be used for low cost labelling of consumer goods. The technology will enable RFID labels in the long term to replace the barcodes used by retailers today. In the RFID manufacturing process, the NanoMas silver nanoparticles are ideal for processing to electronic conductors.

Another area of interest for BASF is in nanocubes which can act as a storage medium for hydrogen. The desire to be mobile and yet not to be without communication and entertainment had led to ever smaller and lighter electronic devices. Whether it's laptops, cell phones or CD players, a key issue is how to power these portable devices (Fig. 2).

DuPont has also develpoed a technique to sort carbon nanotubes using specific sequences of DNA. This is the first demonstration that nanotubes can be sorted by size, property and symmetry - or chirality. Up to now, one of the main problems with single-walled carbon nanotubes is that they are produced as complex mixtures of different nanotube species with different properties - greatly limiting their applications.

The work has been carried out by DuPont researchers Ming Zheng and Xiamin Tu, with Lehigh University professor of chemical engineering Anand Jagota and student Suresh Manohar (Fig. 3). "Our technique is similar to sorting snowflakes by wrapping DNA around each flake," Zheng said. "Nanotubes come in many sizes and designs, and each type offers unique properties for uses that can range from transistors for electronics, light sources for displays or conducting films for photovoltaic materials. The difficult part of our approach is identifying which DNA sequence is most efficient at separation. Our approach was a bit like probing into the DNA library to determine sequences. We tried over 350 sequences and identified more than 20 that showed useful separation properties."

Bayer is focusing on developing nano-scale formulations to help in the design and delivery of drugs. Formulation of poorly soluble actives in life science applications, for example for pharmaceutical and agricultural applications, in animal health, personal care, and in the food industry, is one of the most important challenges in the development of new chemical entities (NCEs). The company offers a method for stabilising amorphous submicron active formulations using a polymer matrix and several different technologies for embedding the active substance: melt dispersion, precipitation, solvent evaporation, supercritical processes or milling - depending on the individual properties of the active.