Ultrasonic treatment has attracted much attention because of its physical and chemical effects that are distinct from those of chemical agents. In particularly, high-frequency ultrasound is known as an effective method because the theoretical resonance frequency of the gas vesicles in Microcystis aeruginosa is in the high frequency range (>100 kHz), which causes gas vesicles collapse and changes the settleability of the algal cells. In this work, the effects of the ultrasonic frequency, acoustic power density and duration on enhancing coagulation to remove turbidity in algae-laden water were studied. In order to explain the mechanism, the morphology of algae cells, the changes in extracellular organic substances, the zeta potential and the formation of hydroxyl radicals were analyzed systematically. Finally, Zeta potentials and flocs morphology after adding PAC were investigated to verify the mechanism. The results showed that the frequency exhibited fewer effects than power and duration on coagulation. SEM images showed that there were more severe cellular damages at 430 and 740 kHz than other frequencies. Sonication could cause the collapse of gas vesicle inside the cell, which was due to the instantaneous high pressure generated by the ultrasonic cavitation instead of the resonance. Furthermore, sonication would result in an increase in proteins in extracellular organic matter (EOM) with continuous ultrasonic irradiation, indicating that a small amount of proteins could promote coagulation and that the accumulation of proteins would inhibit coagulation. Free radical content testing showed that the production of excessive free radicals was often accompanied by a deterioration of the coagulation. The proper mechanical effects were the main mechanism of ultrasonic enhanced coagulation. Thus, it was recommended that the appropriate ultrasonic condition was the one that resulted in a small amount of protein leakage and little generation of free radicals, which occurred at 740 kHz and 0.02 W/mL in approximately 5 min, and would significantly enhance the turbidity removal rate in algae-containing water from approximately 80–90%.
Juanjuan Li,Yutong Cui,Xiaoli Jiang,Xue Chi,Hong Li,Xiang Ma,Yanqiong Tang,Denggao Huang,Zhu Liu
Integrated imaging techniques offer enhanced medical insights into the central nervous system by combining different modalities. In glioma diagnosis, the challenge often lies in delivering contrast agents effectively across the blood-brain barrier. We present an integrated multimodal imaging biohybrid, GV@pCY5, which enables blood-brain barrier penetrating as well as fluorescence and ultrasound (FL/US) imaging capabilities. This biohybrid is created by decorating a far-red-fluorescent cyanine dye (CY5) onto polyethyleneimine (PEI)-coated gas vesicles (GV). The layer-by-layer assembly improves the stability and performance of GV@pCY5 under ultrasound, thanks to the hydration shell variation induced by PEI. Given to the blood-brain barrier penetrating ability, GV@pCY5 demonstrates increase both in fluorescence and ultrasound imaging performance compared to single-component systems, proving effective for glioma diagnosis in vivo. This study underscores the potential of the FL/US platform for dual ratiometric imaging of various cerebral conditions.
Background Focused ultrasound (FUS) combined with microbubbles (MBs) has emerged as a potential approach for opening the blood–brain barrier (BBB) for delivering drugs into the brain. However, MBs range in size of microns and thus can hardly extravasate into the brain parenchyma. Recently, growing attention has been paid to gas vesicles (GVs), which are genetically encoded gas-filled nanostructures with protein shells, due to their potential for extravascular targeting in ultrasound imaging and therapy. However, the use of GVs as agents for BBB opening has not yet been investigated. Methods In this study, GVs were extracted and purified from Halobacterium NRC-1 . Ultrasound imaging performance of GVs was assessed in vitro and in vivo. Then, FUS/GVs-mediated BBB opening for small molecular Evans blue or large molecular liposome delivery across the BBB was examined. Results The results showed a good contrast performance of GVs for brain perfusion ultrasound imaging in vivo. At the acoustic negative pressure of 1.5 MPa, FUS/GVs opened the BBB safely, and effectively enhanced Evans blue and 200-nm liposome delivery into the brain parenchyma. Conclusion Our study suggests that biosynthetic GVs hold great potential to serve as local BBB-opening agents in the development of new targeted drug delivery strategies for central nervous system disorders.
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