Development of a multi-functional preclinical device for the treatment of glioblastoma

Abstract

Glioblastoma multiforme (GBM) is one of the most common and aggressive malignant primary brain tumors in adults. The treatment of GBM is limited by the blood-brain barrier (BBB), which limits the diffusion of appropriate concentrations of therapeutic agents at the tumor site. Among experimental therapies, photo-thermal therapy (PTT) mediated by nanoparticles is a promising strategy. To propose a preclinical versatile research instrument for the development of new PTT for GBM, a multipurpose integrated preclinical device was developed. The setup is able to perform: i) BBB permeabilization by focused ultrasound sonication (FUS); ii) PTT with continuous wave laser; iii) in situ temperature monitoring with photo-acoustic (PA) measurements. In vivo preliminary subcutaneous and transcranial experiments were conducted on healthy or tumor-bearing mice. Transcranial FUS-induced BBB permeabilization was validated using single photon emission computed tomography (SPECT) imaging. PTT capacities were monitored by PA thermometry, and are illustrated through subcutaneous and transcranial in vivo experiments. The results show the therapeutic possibilities and ergonomy of such integrated device as a tool for the validation of future treatments.

Fig. 1.

Top: Schema of the integrated experimental setup (PBS: Polarizing beam splitter; BS: Beam sampler; KTP: Frequency doubling KTP crystal; KG3: Filter glass (Bandpass: 315 - 710 nm); PD: Si Photodetector (Detector, 200 - 1100 nm); $\lambda /2$: Achromatic half-wave plate). Bottom: Cross-section (left) and 3D view (right) of the FUS/PTT/PA probe.

Fig. 2.

Calibration of ultrasound transducer. Top: Experimental setup Bottom left: axial slice view of the focal spot. Bottom right: cross-section view of the focal spot, measurement performed at 0.65 MPa.

Fig. 3.

Example of BBB disruption 30 minutes after single-spot focused ultrasound and ^99mTc-DTPA intravenous injection in a healthy mouse. Left: representative SPECT tomographic image of ^99mTc-DTPA distribution in the head of the animal merged with CT (the contours of the skull are visible in white) with sagittal (left) and coronal (right) sections. Two regions of interest (ROI) are highlighted with white rectangles: ROI 1 is the sonicated volume, ROI 2 is an untreated zone. Center: Segmentation in the brain area. Right: Quantification of ^99mTc-DTPA activity in ROI 1 and ROI 2. Results are expressed as percentage of injected activity per mass of tissue ($\mathrm{\%}$ID/g).

Fig. 4.

Left: Surface (black curves) and intratumoral (blue curves) temperature measurements with thermocouples for three animals for PTT times of 4, 5 and 6 minutes (upward arrow, CW illumination ’ON’: beginning of the PTT; downward arrow, CW illumination ’OFF’: end of the PTT); Center: Example of time-resolved PA measurement, during a 5 minutes PTT, at three different heating times 0.006 min (rising slope, in blue), 2.3 min (plateau, in red) and 5 min (downward slope); Right: Calculated values of ratios $\mathrm{\Delta }P/P_o$ (thin lines) and $\alpha \mathrm{\Delta }T$ (thick lines), $\alpha =0.027\pm 0.003$ °${\mathrm{C}}^{-1}$.

Fig. 5.

Top: PA registered signals [A.U.] during a 10 min PTT for the three mice of Group 2 (without NPs), for 0.007 min (blue), 1 min (red) and 8.5 min (green)

Fig. 6.

Evolution of the estimated temperature rise during the PTT on Group 2 (Left) and Group 3 (Right) mice.

Fig. 7.

PA registered signals [A.U.] during a 10 min PTT for a mouse without NPs (left) and a mouse with NPs (middle) at 0.007 min (blue), 1 min (red) and 8.5 min (green). For a better readability, only one signal per minute is represented. Right: Estimated temperature rise during the PTT for the mouse with (Black curve) and without (Grey curve) NPs.