Emerging Standards and Analytical Science for Nanoenabled Medical Products

Development and application of nanotechnology-enabled medical products, including drugs, devices, and in vitro diagnostics, are rapidly expanding in the global marketplace. In this review, the focus is on providing the reader with an introduction to the landscape of commercially available nanotechnology-enabled medical products as well as an overview of the international documentary standards and reference materials that support and facilitate efficient regulatory evaluation and reliable manufacturing of this diverse group of medical products. We describe the materials, test methods, and standards development needs for emerging medical products. Scientific and measurement challenges involved in the development and application of innovative nanoenabled medical products motivate discussion throughout this review.

The NIST Length Scale Interferometer

The National Institute of Standards and Technology (NIST) interferometer for measuring graduated length scales has been in use since 1965. It was developed in response to the redefinition of the meter in 1960 from the prototype platinum-iridium bar to the wavelength of light. The history of the interferometer is recalled, and its design and operation described. A continuous program of modernization by making physical modifications, measurement procedure changes and computational revisions is described, and the effects of these changes are evaluated. Results of a long-term measurement assurance program, the primary control on the measurement process, are presented, and improvements in measurement uncertainty are documented.

Metrological Timelines in Traceability

There is a growing requirement for an internationally accepted system of recognition of measurement capabilities and relationships within and among countries, to facilitate seamless global commerce and trade. As a result, metrologists worldwide have recently developed increased interest in the concept and definition of traceability. Classically, traceability provides a way of relating the results of a measurement (or value of a standard) to higher level standards. Such standards are usually national or international standards, and the comparisons used to provide the traceability must have well-understood uncertainties. An additional complexity arises because all instruments and standards are subject to change, however slight, over time. This paper develops approaches for dealing with the effects of such time-dependent changes as a part of traceability statements. The use of metrological time-lines provides a means of effectively visualizing these relationships in a statement of traceability. When the rate of change in the measurement process is sufficiently small, the approach proposed here is less important. However, documented measurement assurance procedures are required at all levels so that appropriate uncertainties may be estimated with confidence. When laboratory or national boundaries are crossed in the traceability process, other factors come into play, and the original concept of traceability can become obscure. It is becoming common to hear the term "equivalence" used to describe these more complex measurement relationships.

Foundations of Metrology

The theory of measurement has attracted the attention of a number of philosphers whose works remain largely unknown to metrologists. Recent work in the development of Measurement Assurance Programs has demonstrated the power of this theory as a tool for guiding the development of measurement systems. The elements of the theory, especially that of Carnap and its applications to metrology, are developed as an aid to program planning and evaluation.