Carlos Sierra Sanchez

Transcranial cavitation detection in primates during blood-brain barrier opening-a performance assessment study

Focused ultrasound (FUS) has been shown promise in treating the brain locally and noninvasively. Transcranial passive cavitation detection (PCD) provides methodology for monitoring the treatment in real time, but the skull effects remain a major challenge for its translation to the clinic. In this study, we investigated the sensitivity, reliability, and limitations of PCD through primate (macaque and human) skulls in vitro. The results were further correlated with the in vivo macaque studies including the transcranial PCD calibration and real-time monitoring of blood-brain barrier (BBB) opening, with magnetic resonance imaging assessing the opening and safety. The stable cavitation doses using harmonics (SCDh) and ultraharmonics (SCDu), the inertial cavitation dose (ICD), and the cavitation SNR were quantified based on the PCD signals. Results showed that through the macaque skull, the pressure threshold for detecting the SCDh remained the same as without the skull in place, whereas it increased for the SCDu and ICD; through the human skull, it increased for all cavitation doses. The transcranial PCD was found to be reliable both in vitro and in vivo when the transcranial cavitation SNR exceeded the 1-dB detection limit through the in vitro macaque (attenuation: 4.92 dB/mm) and human (attenuation: 7.33 dB/ mm) skull. In addition, using long pulses enabled reliable PCD monitoring and facilitate BBB opening at low pressures. The in vivo results showed that the SCDh became detectable at pressures as low as 100 kPa; the ICD became detectable at 250 kPa, although it could occur at lower pressures; and the SCDu became detectable at 700 kPa and was less reliable at lower pressures. Real-time monitoring of PCD was further implemented during BBB opening, with successful and safe opening achieved at 250 to 600 kPa in both the thalamus and the putamen. In conclusion, this study shows that transcranial PCD in macaques in vitro and in vivo, and in humans in vitro, is reliable by improving the cavitation SNR beyond the 1-dB detection limit.

Characterizing Focused-Ultrasound Mediated Drug Delivery to the Heterogeneous Primate Brain In Vivo with Acoustic Monitoring

Focused ultrasound with microbubbles has been used to noninvasively and selectively deliver pharmacological agents across the blood-brain barrier (BBB) for treating brain diseases. Acoustic cavitation monitoring could serve as an on-line tool to assess and control the treatment. While it demonstrated a strong correlation in small animals, its translation to primates remains in question due to the anatomically different and highly heterogeneous brain structures with gray and white matteras well as dense vasculature. In addition, the drug delivery efficiency and the BBB opening volume have never been shown to be predictable through cavitation monitoring in primates. This study aimed at determining how cavitation activity is correlated with the amount and concentration of gadolinium delivered through the BBB and its associated delivery efficiency as well as the BBB opening volume in non-human primates. Another important finding entails the effect of heterogeneous brain anatomy and vasculature of a primate brain, i.e., presence of large cerebral vessels, gray and white matter that will also affect the cavitation activity associated with variation of BBB opening in different tissue types, which is not typically observed in small animals. Both these new findings are critical in the primate brain and provide essential information for clinical applications.

Focused ultrasound-enhanced intranasal brain delivery of brain-derived neurotrophic factor

The objective of this study was to unveil the potential mechanism of focused ultrasound (FUS)-enhanced intranasal (IN) brain drug delivery and assess its feasibility in the delivery of therapeutic molecules. Delivery outcomes of fluorescently-labeled dextrans to mouse brains by IN administration either before or after FUS sonication were compared to evaluate whether FUS enhances IN delivery by active pumping or passive diffusion. Fluorescence imaging of brain slices found that IN administration followed by FUS sonication achieved significantly higher delivery than IN administration only, while pre-treatment by FUS sonication followed by IN administration was not significantly different from IN administration only. Brain-derived neurotrophic factor (BDNF), a promising neurotrophic factor for the treatment of many central nervous system diseases, was delivered by IN followed by FUS to demonstrate the feasibility of this technique and compared with the established FUS technique where drugs are injected intravenously. Immunohistochemistry staining of BDNF revealed that FUS-enhanced IN delivery achieved similar locally enhanced delivery as the established FUS technique. This study suggested that FUS enhances IN brain drug delivery by FUS-induced active pumping of the drug and demonstrated that FUS-enhanced IN delivery is a promising technique for noninvasive and localized delivery of therapeutic molecules to the brain.

Behavioral effects of targeted drug delivery via non-invasive microbubble enhanced focused ultrasound blood brain barrier opening in non-human primates

The Blood Brain Barrier (BBB) in Non-Human Primates (NHP) can be non-invasively opened through the use of Focused Ultrasound (FUS) in conjunction with microbubbles. This procedure allows for a targeted, transient opening in the BBB of the NHP which can be utilized to facilitate drug delivery. While FUS has been used to deliver various pharmacological compounds to promote neurogenesis or treat cancer, no group has investigated if drug delivery can affect behavioral responses. In this study, we show the effects of targeted ME-FUS drug delivery on the responses of NHP to a decision making task.

Monitoring of focused ultrasound-induced blood-brain barrier opening in non-human primates using transcranial cavitation detection in vivo and the primate skull effect

Focused ultrasound (FUS) with microbubbles (MB) is promising for assisting the delivery of drugs across the blood-brain barrier (BBB). To assess the safety and efficacy, the monitoring using passive cavitation detection (PCD) is critical and yet the reliability of transcranial detection in large animals remained questioned. To study the primate skull effect, the PCD through the in-vitro monkey and human skulls and in the in vivo monkeys during the sonication (FUS frequency: 500 kHz) were investigated, with the use of in-house made lipid-shelled, monodisperse MB (median diameter: 4-5 μm) and a flatband hydrophone served as a passive cavitation detector. In the in vitro experiments, the MB were injected to the channel of the phantom under a degassed skull for sonication (peak negative pressure/PNP: 50-450 kPa, pulse length/PL: 0.2 ms, PRF: 10 Hz, duration: 2 s). A diagnostic B-mode imaging system was also used to monitor the cavitation. In the in vivo study, the PCD was realtime monitored during the sonication for PCD calibration (PNP: 50-700 kPa, PL: 0.2 ms and 10 ms, PRF: 2 Hz, duration: 10 s) and BBB opening (PNP: 200-600 kPa, PL: 10 ms, PRF: 2 Hz, duration: 2 min). The stable cavitation dose using harmonics (SCDh) and ultraharmonics (SCDu) and the inertial cavitation dose (ICD) were quantified. Results showed that the SCDh, SCDu, and ICD were detectable in vitro at 50 kPa and above, and the B-mode imaging showed bubble collapse at 200 kPa and above. The detection thresholds increased with the skulls in place, with the signal reduction of 15.4 dB for the monkey skull and 34.1 dB for the human skull. In the in vivo experiments, the SCDh and ICD was detectable at and above 100 kPa and 250 kPa, respectively, and the SCDu was less reliable due to spontaneous occurrence. The BBB was found to be disrupted in 250-600 kPa without edema, hemorrhage, and physiological changes were found. In conclusion, the SCDh was more detectable and reliable than the SCDu in assessing stable cavitation in vivo, and the inertial cavitation was detected at 250 kPa and may occur at lower pressures.

Live Intracellular Biorthogonal Imaging by Surface Enhanced Raman Spectroscopy using Alkyne-Silver Nanoparticles Clusters

Live intracellular imaging is a valuable tool in modern diagnostics and pharmacology. Surface Enhanced Raman Spectroscopy (SERS) stands out as a non-destructive and multiplexed technique, but intracellular SERS imaging still suffers from interfering background from endogenous components. Here we show the assembly of small colloidal SERS probes with Raman signal in the cell-silent window of 1800–2900 cm−1 for biorthogonal intracellular SERS imaging of dopamine that was undistinguishable from the endogenous cell background. By linking colloidal silver nanoparticles with alkyne-dopamine adducts, clusters are formed by 2–6 nanoparticles spaced by tight interparticle gaps that exhibited high electric field enhancement and strong SERS signals of alkyne and dopamines. Due to the cell-silent signals of the alkyne, intracellular in-vitro Raman imaging shows that the dopamines on the internalized clusters remain distinguishable across the cytoplasm with good spatial resolution. Our method can be a general-purpose method for real-time imaging of biomolecules, such as proteins, peptides, DNA and drugs.

Author Correction: Live Intracellular Biorthogonal Imaging by Surface Enhanced Raman Spectroscopy using Alkyne-Silver Nanoparticles Clusters

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Focused-ultrasound mediated anti-alpha-synuclein antibody delivery for the treatment of Parkinson’s disease

Focused ultrasound (FUS) in conjunction with microbubbles is a technique to achieve noninvasive, transient, and localized blood-brain barrier (BBB) opening to enhance drug delivery to the brain. Here we explored the potential of FUS-mediated delivery of anti-alpha synuclein (

Focused ultrasound-enhanced intranasal delivery of brain-derived neurotrophic factor

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Efficient Blood-Brain Barrier Opening in Primates with Neuronavigation-Guided Ultrasound and Real-Time Acoustic Mapping

-syn) monoclonal antibodies (mAb) for the treatment of Parkinsons disease. Transgenic A53T mice that express the human A53T