Conspectus
Fluorophore probes are widely used for bioimaging in cells, tissues,
and animals as well as for monitoring of multiple biological processes
in complex environments. Such imaging properties allow scientists
to make direct visualizations of pathological events and cellular
targets. Conventional fluorescent molecules have been developed for
several decades and achieved great successes, but their emissions
are often weakened or quenched at high concentrations that might suffer
from the aggregation-caused quenching (ACQ) effect, which reduces
the efficiencies of their applications.
In contrast to the ACQ
effect, aggregation-induced emission (AIE)
luminogens (AIEgens) display much higher fluorescence in aggregated
states and possess various advantages such as low background, long-term
tracking ability, and strong resistance to photobleaching. Therefore,
AIEgens are employed as unique fluorescence molecules and building
blocks for biosensing applications in the fields of ions, amino acids,
carbohydrates, DNAs/RNAs, peptides/proteins, cellular organelles,
cancer cells, bacteria, and so on.
Quite a few of the above
biosensing missions are accomplished by
modular peptide-modified AIEgen probes (MPAPs) or modular DNA-modified
AIEgen probes (MDAPs) because of the multiple capabilities of peptide
and DNA modules, including solubility, biocompatibility, and recognition.
Meanwhile, both electrostatic interactions and coupling reactions
could provide efficient methods to construct different MPAPs and MDAPs,
finally resulting in a large variety of biosensing probes. Those probes
exhibit leading features of detecting nucleic acids or proteins and
imaging mass biomolecules. For example, under modular design, peptide
modules possessing versatile recognition abilities enable MPAPs to
detect numerous targets, such as integrin αvβ3, aminopeptidase N, MMP-2, MPO, H2O2, and so forth; MDAP could allow the imaging of mRNA in cells and
tissue chips, suggesting the diagnostic functions of MDAP in clinical
samples. Modular design offers a novel strategy to generate AIEgen-based
probes and expedites functional biomacromolecules research. In this
vein, here we review the progress on MPAPs and MDAPs in the most recent
10 years and highlight the modular design strategy as well as their
advanced biosensing applications including briefly two aspects: (1)
detection and (2) imaging. By the use of MPAPs/MDAPs, multiple bioanalytes
can be efficiently analyzed at low concentrations and directly visualized
through high-contrast and luminous imaging. Compared with MPAPs, the
quantities of MDAPs are limited because of the difficult synthesis
of long-length DNA strands. In future work, multifunctional of DNA
sequences are needed to explore varieties of MDAPs for diverse biosensing
purposes. At the end of this Account, some deficiencies and challenges
are mentioned for briging more attention to accelerate the development
of AIEgen-based probes.