Optimization of upconversion luminescence excitation mode for deeper in vivo bioimaging without contrast loss or overheating

Abstract

Upconversion nanoparticles have attracted considerable attention as luminescent markers for bioimaging and sensing due to their capability to convert near-infrared (NIR) excitation into visible or NIR luminescence. However, the wavelength of about 970 nm is commonly used for the upconversion luminescence excitation, where the strong absorption of water is observed, which can lead to laser-induced overheating effects. One of the strategies for avoiding such laser-induced heating involves shifting the excitation into shorter wavelengths region. However, the influence of wavelength change on luminescent images quality has not been investigated yet. In this work, we compare wavelengths of 920, 940 and 970 nm for upconversion luminescence excitation in the thickness of biological tissues in terms of detected signal intensity and obtained image quality (contrast and signal-to-background ratio). Studies on biological tissue phantoms with various scattering and absorbing properties were performed to analyze the influence of optical parameters on the depth and contrast of the images obtained under 920–970 nm excitation. It was shown that at the same power the excitation wavelength shift reduces the detected signal intensity and the resulting image contrast. Visualization of biological tissue samples using shorter excitation wavelengths 920 and 940 nm also reduces signal-to-background ratio (S/B) of the obtained images. The S/B of the obtained images amounted to 2, 6 and 8 for 920, 940 and 970 nm, respectively. It was demonstrated that pulse-periodic excitation mode is preferable for obtaining high quality luminescent images of biological tissues deep layers and minimize overheating. Short pulse durations (duty cycle 20%) don’t result in heating even for 1 W cm−2 pumping power density and allow obtaining high luminescence intensity, which provides good images quality.

Functionalization of Magnetic Nanowires for Active Targeting and Enhanced Cell-Killing Efficacy

“…Based on the magnetic properties of the material, magnetic field strength and frequency, it can be remotely guided, 46,47 rotated, 47,48 or magnetically heated. 49 To avoid the effect of overheating of the biological sample, a spectral range of 650−900 nm 50 that fits into the biological window is preferred to be used, where the biological tissues (such as skin, tissues, and hemoglobin) are relatively transparent as a result of the reduction in both absorption and scattering. 51 In this work, the ability of anti-CD44-functionalized NWs (CD44-NWs) to actively target colon cancer cells was studied in the context of a combined treatment consisting of magnetomechanical (100 mT, 10 Hz) and photothermal (808 nm, 0.7 W/cm 2 ) therapies.…”

“…Based on the magnetic properties of the material, magnetic field strength and frequency, it can be remotely guided, , rotated, , or magnetically heated . To avoid the effect of overheating of the biological sample, a spectral range of 650–900 nm that fits into the biological window is preferred to be used, where the biological tissues (such as skin, tissues, and hemoglobin) are relatively transparent as a result of the reduction in both absorption and scattering …”

Solid optical tissue phantom tools based on upconverting nanoparticles for biomedical applications

“…The four UCNP-containing type 3 inclusion phantoms had varying UCNP concentrations, including 10, 40, 70, and 100 μg/g. A realistic series of UCNP dosages was chosen in accordance with commonly used UCNP dosages in a number of animal studies in the literature 18 , 24 , 29 , 30 …”

“…Type 3 phantoms consist of four smaller A realistic series of UCNP dosages was chosen in accordance with commonly used UCNP dosages in a number of animal studies in the literature. 18,24,29,30 2.2 Instrumentation, Measurement Protocols, and Data Analysis…”

Photoinactivation of coronaviruses: going along the optical spectrum

“…A number of medical laser devices based on LD with various wavelengths in the visible and near infrared spectral ranges have been created. They have permission for clinical PDT (see, for example [25,26]). These devices are widely used to excite various PSs and UNPs for in vitro and in vivo studies and can be used in the antiviral PDT in medical practice, especially in models with laser radiation output through the optical fiber.…”