Lower limb microcirculatory ischemic disease is a vascular
disorder
primarily characterized by limb pain, gangrene, and potential amputation.
It can be caused by various factors, such as hyperglycemia, atherosclerosis,
and infection. Due to the extremely narrow luminal diameter in lower
limb microcirculatory ischemic lesions, both surgical and medical
interventions face challenges in achieving satisfactory therapeutic
outcomes within the microvessels. Extracellular vesicles derived from
mesenchymal stem cells (MSCs-EVs) exhibit promising potential in the
treatment of microcirculation ischemic lesions due to their small
size and ability to promote angiogenesis. After undergoing substantial
losses during the process of EVs transportation, only a minimal fraction
of EVs can effectively reach the site of microcirculatory lesions,
thereby compromising the therapeutic efficacy for microcirculatory
disorders. Herein, an ultrasound-responsive system utilizing 2-(dimethylamino)ethyl
methacrylate-
b
-2-tetrahydropyranyl methacrylate (DMAEMA-
b
-THPMA) micelles to encapsulate MSCs-EVs has been successfully
constructed, with the aim of achieving localized and targeted release
of EVs at the site of microcirculatory lesions. The reversible addition–fragmentation
chain transfer (RAFT) polymerization method facilitates the successful
synthesis of diblock copolymers comprising monomer 2-(dimethylamino)ethyl
methacrylate (DMAEMA) and monomer 2-tetrahydropyranyl methacrylate
(THPMA). The DMAEMA-
b
-THPMA micelles exhibit a nanoscale
structure, reliable biocompatibility, ultrasound responsiveness, and
conspicuous protection of EVs. Furthermore, the implementation of
low-energy-density ultrasound can enhance angiogenesis by upregulating
the levels of the vascular endothelial growth factor (VEGF). In
in vivo
experiments, the ultrasound-responsive system of
the DMAEMA-
b
-THPMA micelles and MSCs-EVs synergistically
enhances therapeutic efficacy by promoting angiogenesis, improving
vascular permeability, and optimizing vascular. In conclusion, this
work demonstrates bioapplication of an ultrasound-responsive micellar
nanosystem loaded with EVs for the treatment of lower limb microcirculatory
ischemic disorders.