Surface-engineered nanobubbles with pH-/light-responsive drug release and charge-switchable behaviors for active NIR/MR/US imaging-guided tumor therapy

Active drug-loaded nanocarriers have been widely employed as efficient drug delivery systems for tumor theranostics. Herein, we report folate-mediated “all-in-one” nanobubbles for tumor-targeted NIR/MR/US imaging and combined chemo-photothermal therapy. The surface-engineered nanobubbles are constructed from oleylamine-/IR-780-loaded hollow structures, folate and the GdDTPA-BSA@5-FU complex via electrostatic adsorption and further filled with gas after freeze drying. DLS data show that the nanobubbles have a hydrodynamic diameter of 120.41？±？18.30？nm. TEM observations show a hollow inner cavity and a shell thickness of approximately 10？nm. The relaxivity (r1) of the nanobubbles reaches 16.56？s？1/mM, indicating suitable features for use as a T1-weighted MR contrast agent. Moreover, due to the gas core inside, the nanobubbles are suitable for ultrasound contrast imaging. Interestingly, ξ-potential data and cumulative release measurements demonstrate that the nanobubbles undergo charge-switchable behaviors and pH-/light-sensitive drug-release behaviors after surface engineering, which could facilitate deep tumor penetration and accelerate drug release for efficient killing of cancer cells. In vivo trimodal imaging and chemo-photothermal therapy for MGC-803 tumor-bearing mice reveal selective tumor accumulation, long tumor retention, and enhanced antitumor behaviors. Therefore, the all-in-one nanobubbles could be applied for active tumor-targeting theranostics