Saponin-Based Near-Infrared Nanoparticles with Aggregation-Induced Emission Behavior: Enhancing Cell Compatibility and Permeability

Fluorescence imaging
is critical for physiological activities and
cell biology but limited by the poor solubility, cell compatibility,
and permeability. Herein, we develop a novel engineering methodology
to prepare biocompatible and penetrable aggregation-induced emission
(AIE) nanoparticles with the assistance of flash nanoprecipitation
(FNP) technology. On the basis of the donor-π-acceptor (D-π-A)
system, the AIE building block of tricyano-methylene-pyridine (TCM) is fine-tuned to long emission wavelength by modulating
the π-conjugation bridge and electron-donating group, thereby
achieving high solid fluorescent quantum yield, near-infrared (NIR)
characteristic, large Stokes shift, and excellent photostability.
On the basis of the FNP technology, the amphiphilic saponin solution
and TCMN-5 in organic solvent are quickly mixed in the
multi-inlet vortex mixer (MIVM), followed by saponin-encapsulation
of the hydrophobic AIE nucleation with inhibiting further growth of
nanoparticles. The biocompatible amphiphilic saponin such as α-hederin
can encapsulate and micellize the AIE TCM fluorophore
for efficient cell imaging. The kinetic FNP technology can not only
modulate the uniform diameter size, but also distinctly increase the
micelle stability when compared to the conventional thermodynamic
self-aggregation method, which provides an alternative opportunity
for scale-up preparation of drugs and probes in delivery vehicles.