Black Mesoporous Silicon as a Contrast Agent for LED-Based 3D Photoacoustic Tomography

Abstract

Mesoporous silicon (PSi) nanoparticles have been widely studied in different biomedical imaging modalities due to their several beneficial material properties. However, they have not been found to be suitable for photoacoustic imaging due to their poor photothermal conversion performance. In the present study, biodegradable black mesoporous silicon (BPSi) nanoparticles with strong light absorbance were developed as superior image contrast agents for photoacoustic tomography (PAT), which was realized with a light-emitting diode (LED) instead of the commonly used laser. LED-based PAT offers the advantages of low cost, compactness, good mobility, and easy operation as compared to the traditional laser-based PAT modality. Nevertheless, the poor imaging sensitivity of the LED-PAT systems has been the main barrier to prevent their wide biomedical application because the LED light has low optical energy. The present study demonstrated that the imaging sensitivity of the LED-PAT system was significantly enhanced with the PEGylated BPSi (PEG–BPSi) nanoparticles. The PEG–BPSi nanoparticles were clearly detectable with a low concentration of 0.05 mg/mL in vitro and with an LED radiation energy of 5.2 μJ. The required concentration of the PEG–BPSi nanoparticles was 10 times lesser than that of the reference gold nanoparticles to reach the corresponding level of the imaging contrast. The ex vivo studies demonstrated that the submillimeter BPSi nanoparticle-based absorbers were distinguishable in chicken breast tissues. The strong contrast provided by the BPSi particles indicated that these particles can be utilized as novel contrast agents in PAT, especially in LED-based systems with low light intensity.

Engineering Plasmonic Nanoparticles for Enhanced Photoacoustic Imaging

“…Nanoparticles are employed as PA contrast agents because of their high absorption cross section compared to that of other small molecules . Generally increasing the absorbance leads to an increase in photoacoustic signal. − Coatings like polydopamine, , melanin, titanium dioxide, graphene oxide, and reduced graphene oxide , on gold nanoparticles increase the absorbance and subsequent PA amplitude. Although uncoated nanoparticles and coatings alone showed no enhancement in all these reports, they do not show if a mixture of the core and shell materials leads to PA enhancement.…”

Inorganic Nanomaterials for Photothermal‐Based Cancer Theranostics

“…Nevertheless, imaging sensitivity and specificity are not enough to meet clinical demands in many cases. To overcome these challenges, many types of inorganic NPs, such as gold NPs, [233] porous silicon, [234] carbonbased nanomaterials, [235] and metal sulfides [236] have been studied as exogenous contrast agents to improve the imaging sensitivity and contrast, and further enable cellular and molecular PAI. [235,237] Moreover, the NPs have the potential of passive cancer targeting due to an enhanced permeability and retention (EPR) effect [63b] and active targeting via ligand grafting, [103k,235,237,238] thus improving the imaging specificity of the PAI.…”

Experimental Evaluation of Radiation Response and Thermal Properties of NPs-Loaded Tissues-Mimicking Phantoms

“…In addition, the recently developed black PSi (BPSi) has superior photothermal conversion performance, as compared to the widely used nanomaterials such as carbon nanotubes [ 14 ]. Thus, the BPSi NPs have been successfully used for photothermal therapy and photoacoustic tomography [ 14 , 26 , 27 ].…”