Lin Meng-Ting, Chan Tsai-Yun, Liao Wei-Hao, Wu Chueh-Hung, Young Tai-Horng, Chen Wen-Shiang
Department of Biomedical Engineering, College of Medicine, National Taiwan University, Taipei, Taiwan; Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan.
Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan.
Ultrasound Med Biol. 2025 May;51(5):788-796. doi: 10.1016/j.ultrasmedbio.2025.01.003. Epub 2025 Feb 2.
Nasal-to-brain (NtoB) delivery is a noninvasive approach that uses the nasal cavity as a pathway to transport therapeutic agents directly to the brain. This approach bypasses systemic circulation and avoids the blood-brain barrier (BBB). Transcranial ultrasound, coupled with microbubbles (MB), is a technique used to oscillate and generate acoustic cavitation to open the capillary tight junctions of BBB temporarily. Its efficacy in facilitating NtoB delivery has been demonstrated in vivo. However, while opening the BBB, sonication with MB poses the risk of cerebral microhemorrhage or brain tissue damage due to sonication-induced physical injury. This study aimed to assess the effectiveness of low-intensity ultrasound treatment to facilitate NtoB delivery in a mouse model without using MB.
In this study, 10-kDa dextran was administered intranasally (IN), and transcranial planar US was applied to the entire mouse brain without MB assistance. Ex-vivo whole brain imaging via fluorescence macroscopy, brain slice analysis with fluorescence microscope, and quantification of dextran concentration in distinct brain regions were conducted to compare the IN-only, IN combined with US (IN+US), and sham groups. For the trigeminal nerves (TN), fluorescence macroscopy, microscopy, and TN concentration quantification were performed to compare the three groups.
Whole brain imaging revealed that US facilitated the IN delivery of dextran to the olfactory bulb (OB) in the IN+US group compared with that in the IN-only and sham groups; however, this difference was not observed after a 24 h follow-up. Conversely, brain slice images showed that the tracer was delivered to the OB, cerebral cortex, striatum and brainstem in the IN+US group, but this finding was not observed in the IN-only group at the 4 h mark. The quantification of fluorescence intensity at two follow-up time points revealed no significant difference between the IN and IN+US groups in these specific regions. Dextran concentration analysis for distinct brain areas and TN showed that ultrasound significantly increased the tracer concentration delivered to the OB and TN in the IN+US group at the 4 h mark compared with that in the IN-only and sham groups; however, this effect was not sustained at 24 h. Confocal microscopy indicated that the dextran tracer accumulated in the perivascular space along the microvascular structures.
We demonstrated the efficacy of low-intensity ultrasound without using MB, in enhancing nose-to-OB and nose-to-TN drug delivery, and proposed the potential for future clinical application. Thus, we showed that this approach was safe, without evidence of microhemorrhage or brain tissue damage.
鼻-脑（NtoB）给药是一种非侵入性方法，它利用鼻腔作为将治疗药物直接输送到大脑的途径。这种方法绕过了体循环，避免了血脑屏障（BBB）。经颅超声与微泡（MB）相结合，是一种用于振荡并产生声空化以暂时打开BBB毛细血管紧密连接的技术。其在促进NtoB给药方面的功效已在体内得到证实。然而，在打开BBB的同时，用MB进行超声处理存在因超声诱导的物理损伤而导致脑微出血或脑组织损伤的风险。本研究旨在评估在不使用MB的小鼠模型中低强度超声治疗促进NtoB给药的有效性。
在本研究中，将10 kDa的葡聚糖经鼻内（IN）给药，并在不借助MB的情况下对整个小鼠脑进行经颅平面超声处理。通过荧光宏观成像进行离体全脑成像、用荧光显微镜进行脑切片分析以及对不同脑区的葡聚糖浓度进行定量，以比较单纯IN组、IN联合超声（IN+US）组和假手术组。对于三叉神经（TN），进行荧光宏观成像、显微镜检查以及TN浓度定量以比较三组。
全脑成像显示，与单纯IN组和假手术组相比，IN+US组中超声促进了葡聚糖向嗅球（OB）的IN给药；然而，在24小时随访后未观察到这种差异。相反，脑切片图像显示，IN+US组中示踪剂被输送到OB、大脑皮层、纹状体和脑干，但在4小时时单纯IN组未观察到这一发现。在两个随访时间点对荧光强度的定量显示，在这些特定区域，IN组和IN+US组之间无显著差异。对不同脑区和TN的葡聚糖浓度分析表明，与单纯IN组和假手术组相比，在4小时时超声显著增加了IN+US组中输送到OB和TN的示踪剂浓度；然而，这种效应在24小时时未持续。共聚焦显微镜检查表明，葡聚糖示踪剂沿微血管结构在血管周围间隙中积聚。
我们证明了在不使用MB的情况下低强度超声在增强鼻至OB和鼻至TN药物递送方面的功效，并提出了其未来临床应用的潜力。因此，我们表明这种方法是安全的，没有脑微出血或脑组织损伤的证据。
