New Functional Handle for Use as a Self-Reporting
Contrast and Delivery Agent in Nanomedicine
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Abstract
The synthesis and
photophysical characterization of a chromophore-bridged
block copolymer system is presented. This system is based on a dithiomaleimide
(DTM) functional group as a highly emissive functionality which can
readily be incorporated into polymeric scaffolds. A key advantage
of this new reporter group is its versatile chemistry, ease of further
functionalization, and notably small size, which allows for ready
incorporation without affecting or disrupting the self-assembly process
critical to the formation of core–shell polymeric contrast
and drug delivery agents. We demonstrate the potential of this functionality
with a diblock system which has been shown to be appropriate for micellization
and, when in the micellar state, does not self-quench. The block copolymer
is shown to be significantly more emissive than the lone dye, with
a concentration-independent emission and anisotropy profile from 1.5
mM to 0.15 μM. An emission lifetime and anisotropy decay comparison
of the block copolymer to its micelle displays that time-domain fluorescence
lifetime imaging (FLIM) is able to rapidly resolve differences in
the supramolecular state of this block–dye–block polymer
system. Furthermore, the ability to resolve these differences in the
supramolecular state means that the DTM micelles are capable of self-reporting
when disassembly occurs, simply by monitoring with FLIM. We demonstrate
the great potential for in vitro applications that this system provides
by using FLIM to observe micelle disassembly in different vascular
components of rat hippocampal tissue. In total this system represents
a new class of in-chain emitter which is appropriate for application
in quantitative imaging and the tracking of particle degradation/disassembly
events in biological environments