Two-photon microscopy for real-time monitoring of focused ultrasound-mediated drug delivery to the brain in a mouse model of Alzheimer's disease

Abstract

There is substantial evidence that focused ultrasound (FUS) in combination with microbubble contrast agent can cause disruption of the blood-brain barrier (BBB) to aid in drug delivery to the brain. We have previously demonstrated that FUS efficiently delivers antibodies against amyloid-β peptides (Aβ) through the BBB, leading to a reduction in amyloid pathology at 4 days in a mouse model of Alzheimer’s disease. In the current study, we used two-photon microscopy to characterize the effect of FUS in real time on amyloid pathology in the mouse brain. Mice were anesthetized and a cranial window was made in the skull. A custom-built ultrasound transducer was fixed to a coverslip and attached to the skull, covering the cranial window. Methoxy-X04 [2-5mg/kg] delivered intravenously 1 hr prior to the experiment clearly labelled the Aβ surrounding the vessels and the amyloid plaques in the cortex. Dextran conjugated Texas Red (70kDa) administered intravenously, confirmed BBB disruption. BBB disruption occurred in transgenic and non-transgenic animals at similar ultrasound pressures tested. However, the time required for BBB closure following FUS was longer in the Tg mice. We have conjugated Aβ antibodies to the fluorescent molecule FITC for real time monitoring of the antibody distribution in the brain. Our current experiments are aimed at optimizing the parameters to achieve maximal fluorescent intensity of the BAM10 antibody at the plaque surface. Two-photon microscopy has proven to be a valuable tool for evaluating the efficacy of FUS mediated drug delivery, including antibodies, to the Alzheimer brain.