In this paper we describe enzyme-responsive fluorogenic micellar nanoparticles with detectable spectrophotometric properties unique to the particles and their aggregated state. These micelles are assembled from peptide-polymer amphiphiles (PPAs) labeled with either fluorescein or rhodamine. This is achieved by labeling otherwise similar block copolymer amphiphiles with each of the dyes. When mixed together, signals from the FRET-pairs can be utilized to detect particle assembly and hence enzymatic activity. Furthermore, we show FRET signals within the shell of the assembled micelles can be used to estimate particle stability (critical aggregation concentration) and enable a determination of intraparticle distances between amphiphiles in the micellar aggregates leading to elucidation of the packing arrangement of amphiphilic copolymers within the micelles.
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