At high concentration or in the aggregated state, most
of the traditional
luminophores suffer from the general aggregation-caused quenching
(ACQ) effect, which significantly limits their biomedical applications.
On the contrary, a few fluorophores exhibit an aggregation-induced
emission (AIE) feature which is just the opposite of ACQ. The luminophores
with aggregation-induced emission (AIEgens) have exhibited noteworthy
advantages to get tunable emission, excellent photostability, and
biocompatibility. Incorporating AIEgens into polymer design has yielded
diversified polymer systems with fascinating photophysical characteristics.
Again, stimuli-responsive polymers are capable of undergoing chemical
and/or physical property changes on receiving signals from single
or multiple stimuli. The combination of the AIE property and stimuli
responses in a single polymer platform provides a feasible and effective
strategy for the development of smart polymers with promising biomedical
applications. Herein, the advancements in stimuli-responsive polymers
with AIE characteristics for biomedical applications are summarized.
AIE-active polymers are first categorized into conventional π–π
conjugated and nonconventional fluorophore systems and then subdivided
based on various stimuli, such as pH, redox, enzyme, reactive oxygen
species (ROS), and temperature. In each section, the design strategies
of the smart polymers and their biomedical applications, including
bioimaging, cancer theranostics, gene delivery, and antimicrobial
examples, are introduced. The current challenges and future perspectives
of this field are also stated at the end of this review article.