Light activated microbubbles for imaging and microsurgery

Cavigli, Lucia; Micheletti, Filippo; Tortoli, Paolo; Centi, Sonia; Lai, Sarah; Borri, Claudio; Rossi, Francesca; Ratto, Fulvio; Pini, Roberto

doi:10.1117/12.2252783

Cited by 4 publications

(8 citation statements)

References 39 publications

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“…Another method that exploits the dependence of the photoacoustic response on the optical absorbance of the gold nanorods [ 14 ] is based on the dynamic analysis of the trend of the signal amplitude with the extant fluence of the optical excitation [ 151 , 153 , 154 , 155 ]. For each condition, the signal amplitude is averaged over a given time or number of pulses, and then added to a scatter plot as a function of optical fluence.…”

Section: Contrast Agents For Photoacoustic Imagingmentioning

confidence: 99%

“…When the sample is not refreshed from condition to condition, this method compares to the first case described in this paragraph, because it does not decouple from cumulative effects that may add up from pulse to pulse and depend on all details of the particular sequence and protocol in use. In order to avoid such effects, it is possible to implement a microfluidic set-up to continuously keep the sample in flow [ 153 , 154 , 155 ]. In this case, the trend captures the onset of particle reshaping within the duration of a single pulse, and the relevant threshold may differ from the previous methods.…”

Section: Contrast Agents For Photoacoustic Imagingmentioning

confidence: 99%

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Photostability of Contrast Agents for Photoacoustics: The Case of Gold Nanorods

et al. 2021

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Plasmonic particles as gold nanorods have emerged as powerful contrast agents for critical applications as the photoacoustic imaging and photothermal ablation of cancer. However, their unique efficiency of photothermal conversion may turn into a practical disadvantage, and expose them to the risk of overheating and irreversible photodamage. Here, we outline the main ideas behind the technology of photoacoustic imaging and the use of relevant contrast agents, with a main focus on gold nanorods. We delve into the processes of premelting and reshaping of gold nanorods under illumination with optical pulses of a typical duration in the order of few ns, and we present different approaches to mitigate this issue. We undertake a retrospective classification of such approaches according to their underlying, often implicit, principles as: constraining the initial shape; or speeding up their thermal coupling to the environment by lowering their interfacial thermal resistance; or redistributing the input energy among more particles. We discuss advantages, disadvantages and contexts of practical interest where one solution may be more appropriate than the other.

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Section: Contrast Agents For Photoacoustic Imagingmentioning

confidence: 99%

Section: Contrast Agents For Photoacoustic Imagingmentioning

confidence: 99%

Photostability of Contrast Agents for Photoacoustics: The Case of Gold Nanorods

et al. 2021

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“…Photoacoustic experiments were carried out with a homemade inverted photoacoustic microscope. , The optical source was a fiber-coupled diode-pumped microchip laser by Asclepion Laser Technologies (Jena, Germany) emitting pulses with a wavelength of 1064 nm, duration of 3.3 ns, and repetition rate of 10 Hz. An attenuator placed in front of the output was used to tune the optical fluence, which was monitored in real time with a QE8SP pyroelectric detector from Gentec-EO (Quebec, QC, Canada).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Flow chambers (μ-Slide I Luer Family, channel height 200 μm, IBIDI GmbH, Planegg/Martinsried, Germany) were filled with suspensions of gold nanorods, coupled to a peristaltic pump (model FH10, Thermo Scientific, Waltham, MA U.S.A.), and immersed in DI water . The use of microfluidic chambers is a promising tool to assess the performance of photoacoustic systems and contrast agents. , The laser beam was focused perpendicular to the flow chamber with a spot diameter of 300 μm.…”

Section: Experimental Methodsmentioning

confidence: 99%

Small Thiols Stabilize the Shape of Gold Nanorods

et al. 2020

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The stabilization of the optical properties of anisotropic plasmonic particles upon thermal annealing and laser irradiation is an important issue in many biomedical applications. Here, we address the effect of small thiols on the thermal and photostability of gold nanorods. As-synthesized colloids were treated with mixtures of thiolated polyethylene glycol and methylbenzenethiol with molar ratios ranging from 0, for pure PEG, to 20 and then incubated in an oven at sub-boiling conditions. We found that small thiols dramatically enhance the thermal stability of gold nanorods. For instance, after 1 h at 90 °C samples with pure PEG lost more than 70% of optical absorbance at their initial peak position, while particles coated with a thicker layer of methylbenzenethiol remained nearly unchanged. We ascribe this effect to a modulation of the activation barrier for surface diffusion of gold atoms. Additionally, we addressed the translation of this effect to the photostability of gold nanorods irradiated under conditions of interest in photoacoustic imaging and found that small thiols delay relevant damage thresholds by as much as a factor of 2. Our findings will help researchers design novel tags that overcome the limitations related to thermal and photoinstabilities in a broad variety of applicative contexts.

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“…11,12 There have been limited reports on the use of other PNP shapes for bubble generation, and many have been performed using femtosecond pulsed lasers. [16][17][18][19][20][21][22] With diagnostic biophotonic techniques employing NIR-resonant nanoparticles and nanosecond pulsed lasers, such as photoacoustic imaging, [23][24][25] it is important to evaluate the possibility of bubble generation, which may lead to unintended biological effects.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of parameters influencing plasmonic nanoparticle-mediated bubble generation with nanosecond laser pulses

et al. 2019

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Plasmonic nanoparticles (PNPs) continue to see increasing use in biophotonics for a variety of applications, including cancer detection and treatment. Several PNP-based approaches involve the generation of highly transient nanobubbles due to pulsed laser-induced vaporization and cavitation. While much effort has been devoted to elucidating the mechanisms behind bubble generation with spherical gold nano particles, the effects of particle shape on bubble generation thresholds are not well understood, especially in the nanosecond pulse regime. Our study aims to compare the bubble generation thresholds of gold nanospheres, gold nanorods, and silica-core gold nanoshells with different sizes, resonances, and surface coatings. Bubble generation is detected using a multimodality microscopy platform for simultaneous, nanosecond resolution pump-probe imaging, integrated scattering response, and acoustic transient detection. Nanoshells and large (40-nm width) nanorods were found to have the lowest thresholds for bubble generation, and in some cases they generated bubbles at radiant exposures below standard laser safety limits for skin exposure. This has important implications for both safety and performance of techniques employing pulsed lasers and PNPs.

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Light activated microbubbles for imaging and microsurgery

Cited by 4 publications

References 39 publications

Photostability of Contrast Agents for Photoacoustics: The Case of Gold Nanorods

Photostability of Contrast Agents for Photoacoustics: The Case of Gold Nanorods

Small Thiols Stabilize the Shape of Gold Nanorods

Experimental investigation of parameters influencing plasmonic nanoparticle-mediated bubble generation with nanosecond laser pulses

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