A novel alkaline pH-responsive probe based on an asymmetric aza-BODIPY was synthesized in a one-pot Schiff base formation reaction. This pH-sensitive probe comprises an asymmetric aza-BODIPY as the luminescent core, with a benzothiazole moiety connected via an imine bond serving as the recognition site. The probe exhibits a turn-off fluorescence response upon exposure to alkaline pH (9.6–12.4), while a bathochromic band in the absorption emerges due to its extended π-conjugation system, accompanied by a visible colorimetric change from yellow to orange to red. Furthermore, the probe responds linearly in the highly alkaline region, with a p K a of 11.65. The recognition mechanism of the probe towards alkaline pH relies on the deprotonation of the imine group on the aza-BODIPY core, leading to an enhanced degree of π-electron conjugation. The quenched fluorescence intensity is attributed to the increased non-radiative decay of the deprotonated form of the probe. The probe demonstrates high reliability for practical applications due to its photostability and reversibility. This study provides new insights into the design of probes for detecting high alkaline pH levels.
Youliang Tian,Dalong Yin,Quan Cheng,Huiping Dang,Changchang Teng,Lifeng Yan
Achieving J-aggregation of a molecule is a fascinating way to construct fluorescent imaging and photothermal therapy agents in the second near-infrared window. Modulation of the balance between intermolecular π–π stacking and steric interactions is an elegant method to acquire J-aggregation dyes. Herein, we succeeded in synthesizing an aza-BODIPY dye with J-aggregation characteristics by introducing steric hindrance (TPA) and a π-bridge (thiophene) in the aza-BODIPY skeleton. In aqueous solutions, supramolecular J-aggregates with a regular lamellar stacking structure could quickly be formed by the dye-templated self-assembly and longer absorption (λmax = 939 nm) and emission (λmax = 1039 nm) bands were observed. After co-assembly of the dye and an amphiphilic polypeptide (POEGMA23–PAsp20), the obtained J-aggregation nanoparticles (J-NPs) with good water solubility and smaller size were more suitable for application in living organisms. In addition, the J-NPs exhibited good stability, considerable photothermal conversion capacity (η = 35.6%), and excellent resistance to pH, H2O2, and photobleaching. In vitro and in vivo experiments revealed that the J-NPs show great NIR-II fluorescence imaging capabilities and anti-tumor effects under 915 nm irradiation (1 W cm−2). This is a rare example of using BODIPY dyes to perform NIR-II fluorescence imaging-guided photothermal therapy under NIR-II irradiation.
Siao Yang,Xiaoxiao Hu,Zhengze Yong,Qingqing Dou,Cuilu Quan,Hong-Bo Cheng,Mo Zhang,Jing Wang
Photoimmunotherapy represents an innovative approach to enhancing the efficiency of immunotherapy in cancer treatment. This approach involves the fusion of immunotherapy and phototherapy (encompassing techniques like photodynamic therapy (PDT) and photothermal therapy (PTT)). Boron-dipyrromethene (BODIPY) has the potential to trigger immunotherapy owing to its excellent PD and PT efficiency. However, the improvements in water solubility, bioavailability, PD/PT combined efficiency, and tumor tissue targeting of BODIPY require introduction of suitable carriers for potential practical application. Herein, a disulfide bond-based hollow mesoporous organosilica (HMON) with excellent biocompatibility and GSH-responsive degradation properties was used as a carrier to load a bithiophene Aza-BODIPY dye (B5), constructing a sample chemotherapy reagent-free B5@HMON nanoplatform achieving triple-synergistic photoimmunotherapy. HMON, involving disulfide bond , is utilized to improve water solubility, tumor tissue targeting, and PD efficiency by depleting GSH and enhancing host-guest interaction between B5 and HMO. The study reveals that HMON’s large specific surface area and porous properties significantly enhance the light collection and oxygen adsorption capacity. The HMON’s rich mesoporous structure and internal cavity achieved a loading rate of B5 at 11 %. It was found that the triple-synergistic nanoplatform triggered a stronger anti-tumor immune response, including tumor invasion, cytokine production, calreticulin translocation, and dendritic cell maturation, eliciting specific tumor-specific immunological responses in vivo and in vitro . The BALB/c mouse model with 4T1 tumors was used to assess tumor suppression efficiency in vivo , showing that almost all tumors in the B5@HMON group disappeared after 14 days. Such a simple chemotherapy reagent-free B5@HMON nanoplatform achieved triple-synergistic photoimmunotherapy.
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