Plasmonically enhanced two-photon absorption induced photoacoustic microscopy with laser-synthesized TiN nanoparticles

Abstract

Combining photonic excitation and acoustic detection, photoacoustic imaging (PAI) presents one of the most promising noninvasive biomedical diagnostic modalities, but this technique still lacks efficient nano-sized contrast agents absorbing light in the region of relative tissue transparency (630–900 nm). Here, we explore the use of titanium nitride (TiN) nanoparticles (NPs) fabricated by methods of pulsed laser ablation in liquids as a contrast agent in PAI. When prepared in acetone, the NPs are spherical, have an average size of 25 nm, and exhibit a broad plasmonic absorption peak around 700 nm. We show that solutions of these NPs render possible a strong nonlinear photoacoustic response and the generation of photoacoustic images with 67 μm resolution within the biological transparency window. The observed effect is explained by a plasmonically enhanced two-photon absorption process in TiN NPs. Combined with earlier demonstrated capability of generating photothermal therapeutic effect, relative chemical purity, and excellent biocompatibility, laser-synthesized TiN NPs promise attractive applications in biomedical theranostics involving imaging modalities based on photoacoustics microscopy or tomography.

Er3+-Yb3+ co-doped nanoparticles as contrast agents for near infrared biomedical photoacoustic imaging application

“…The experimental setup is similar to the one employed in ref. 11 and shown in Figure 4. The optical excitation pulses were generated from an optical parametric amplifier (OPA) capable of generating 7 ns pulses at 10 Hz repetition rate, with energies up to 20 mJ from 400 nm to 2000 nm.…”

“…The requirement for the materials choice, besides an easy, not expensive and ecofriendly fabrication process, includes biocompatibility, biodegradability, non-toxicity and low doses as being necessary for real life biomedical applications. There have been many studies on such materials, such as gold, silver, titanium nitrite and RED nanomaterials, as can be found in the not extensive list of recent review articles 6,7,8,9,10,11 . The use RED particles as photoacoustic contrast agents have also been reported by Sheng et al 2,12,13 .…”

Comparison of optical and photoacoustic response of laser-synthesized TiN nanoparticles

“…In addition to their remarkable photothermal properties, laser-synthesized TiN NPs exhibit excellent biocompatibility both in vivo and in vitro 32 . Moreover, we already demonstrated strong non-linear PA response of the laser-synthesized TiN in colloidal state and developed a procedure to make tissue-mimicking phantoms containing these NPs 33,34 . These findings highlight the potential of TiN NPs as both exogenous contrast agents for PAI and as sensitizers for PTT.…”

A tissue-mimicking phantom with flexible optical properties for studying photoacoustic response of nanoparticles

“…and demonstrated their good biocompatibility both in vivo and in vitro as well as high photothermal effect in vitro even at very low concentrations 20,26,27 . TiN NPs were already used as exogenous contrast agents in PAI and as sensitizers in PTT 18,19,28,29 .…”