Oxygen‐Vacancy‐Rich Piezoelectric BiO_2−x Nanosheets for Augmented Piezocatalytic, Sonothermal, and Enzymatic Therapies

Abstract

Piezocatalytic therapy is a new-emerging reactive oxygen species (ROS)-enabled therapeutic strategy that relies on built-in electric field and energy-band bending of piezoelectric materials activated by ultrasound (US) irradiation. Despite becoming a hot topic, material development and mechanism exploration are still underway. Herein, as-synthesized oxygen-vacancy-rich BiO 2−x nanosheets (NSs) demonstrate outstanding piezoelectric properties. Under US, a piezo-potential of 0.25 V for BiO 2−x NSs is sufficient to tilt the conduction band to be more negative than the redox potentials of O 2 / • O 2 − , • O 2 − /H 2 O 2 , and H 2 O 2 / • OH, which initiates a cascade reaction for ROS generation. Moreover, the BiO 2−x NSs exhibit peroxidase and oxidase-like activities to augment ROS production, especially in the H 2 O 2 -overexpressed tumor microenvironment. Density functional theory calculations show that the generated oxygen vacancies in BiO 2−x NSs are favorable for H 2 O 2 adsorption and increasing the carrier density to produce ROS. Furthermore, the quick movement of electrons enables an excellent sonothermal effect, for example, rapid rise in temperature to nearly 65 °C upon US with low power (1.2 W cm −2 ) and short time (96 s). Therefore, this system realizes a multimode synergistic combination of piezocatalytic, enzymatic, and sonothermal therapies, providing a new direction for defect engineering-optimized piezoelectric materials for tumor therapy.

Reactive oxygen species for therapeutic application: Role of piezoelectric materials

“…47,48 The interference of proton (H + ) with superoxide radical yields H 2 O 2 . 49 The source of ROS is the molecular oxygen which is a strong oxidant by nature and its power of oxidation is determined by two parallel unpaired electrons which have the highest level of energy related to other electrons in the oxygen molecule. [50][51][52] Yoshio Nosaka et al clearly demonstrate the electronic states and successive transformation of its molecular entity to free radicals.…”

A Comprehensive Review on Non‐Trivalent Bismuth‐Based Materials: Structure, Synthesis, and Strategies for Improving Photocatalytic Performance

“…More recently, Gai et al reported that the presence of rich OVs at the surface of BiO 2− x is favorable for H 2 O 2 adsorption, activation, and dissociation to produce reactive oxygen species (ROS). [ 36 ] Moreover, except the commonly investigated photocatalytic performance, they found that BiO 2− x nanosheets possess piezoelectric properties activated by ultrasound irradiation and exhibit peroxides and oxidase‐like activity to augment ROS production, thus providing a direction for tumor therapy. [ 36 ] In addition, Chen’ s group reported that BiO 2− x nanosheets exhibited low‐temperature thermal catalytic activity for removing 4‐chlorophenol (4‐CP), where ROS come from the release of lattice oxygen in BiO 2− x and OVs could enhance the fluidity of lattice oxygen.…”

“…[ 36 ] Moreover, except the commonly investigated photocatalytic performance, they found that BiO 2− x nanosheets possess piezoelectric properties activated by ultrasound irradiation and exhibit peroxides and oxidase‐like activity to augment ROS production, thus providing a direction for tumor therapy. [ 36 ] In addition, Chen’ s group reported that BiO 2− x nanosheets exhibited low‐temperature thermal catalytic activity for removing 4‐chlorophenol (4‐CP), where ROS come from the release of lattice oxygen in BiO 2− x and OVs could enhance the fluidity of lattice oxygen. [ 40 ] In addition, vacancy‐rich BiO 2− x also could activate persulfate into sulfate radicals under NIR irradiation through light/heat mode due to good light‐ and heat‐absorption ability.…”

Novel rod‐like carbon nanomaterials as near infrared‐responsive drug delivery system for potential anticancer applications

“…In recent years, stimuli-responsive controlled nano-drug delivery systems have been proposed to improve the efficiency of treatment, while the stimulus response form included but is not limited to temperature stimuli [23][24][25], magnetism stimuli [26], enzyme stimuli [27][28][29], and pH stimuli [30]. For example, a novel multifunctional WS 2 -IO@MS-PEG nanoscale platform was prepared by the Yang group [31].…”