Abstract Real‐time measurements of biological/chemical/physical processes, with no interferences, are an ultimate goal for in vivo intracellular studies. To construct intracellular biosensors that meet such a goal, nanoparticle (NP) platforms seem to be
most promising, because of their small size and excellent engineerability. This review describes the development of NP‐based
opical sensors and their intracellular applications. The sensor designs are classified into two types, based on the sensor
structures regarding analyte receptor and signal transducer. Type 1 sensors, with a single component for both receptor and
transducer, work by mechanisms similar to those of ‘molecular probes’. Type 2 sensors, with a separate component for receptor
and transducer, work by different mechanisms that require the presence of specific NPs. A synergistic increase in optical
signal or selectivity has been reported for these second type of NP sensors. With ongoing rapid advances in nanotechnology
and instrumentation, these NP systems will soon be capable of sensing at the single‐molecule level, at the point of interest
within the living cell, and capable of simultaneously detecting multiple analytes and physical parameters. Copyright © 2008
John Wiley & Sons, Inc.
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