Noninvasive and minimally-invasive optical monitoring technologies.

With recent advancements in micro-fabrication and nano-fabrication techniques as well as advancements in the photonics industry, there is now the potential to develop less invasive portable sensors for monitoring micronutrients and other substances used to assess overall health. There have been many technology innovations in the central laboratory for these substances for overall health status but the primary motivation for the research and development of a portable field instrument has come from a diabetic patient and market-driven desire to minimally invasively or noninvasively monitor glucose concentrations in vivo. Such a sensor system has the potential to significantly improve the quality of life for the estimated 16 million diabetics in this country by making routine glucose measurements less painful and more convenient. In addition, there is a critical need for the development of less invasive portable technologies to assess micronutrient status (iron, vitamin A, iodine and folate), environmental hazards (lead) and for other disease-related substances, such as billirubin for infant jaundice. Currently, over 100 small companies and universities are working to develop improved monitoring devices, primarily for glucose, and optical methods are a big part of these efforts. In this article many of these potentially less invasive and portable optical sensing technologies, which are currently under investigation, will be reviewed including optical absorption spectroscopy, polarimetry, Raman spectroscopy and fluorescence.