Antonio Benayas

Exploiting the biological windows: current perspectives on fluorescent bioprobes emitting above 1000 nm

With the goal of developing more accurate, efficient, non-invasive and fast diagnostic tools, the use of near-infrared (NIR) light in the range of the second and third biological windows (NIR-II: 1000-1350 nm, NIR-III: 1550-1870 nm) is growing remarkably as it provides the advantages of deeper penetration depth into biological tissues, better image contrast, reduced phototoxicity and photobleaching. Consequently, NIR-based bioimaging has become a quickly emerging field and manifold new NIR-emitting bioprobes have been reported. Classes of materials suggested as potential probes for NIR-to-NIR bioimaging (using NIR light for the excitation and emission) are quite diverse. These include rare-earth based nanoparticles, Group-IV nanostructures (single-walled carbon nanotubes, carbon nanoparticles and more recently Si- or Ge-based nanostructures) as well as Ag, In and Pb chalcogenide quantum dots. This review summarizes and discusses current trends, material merits, and latest developments in NIR-to-NIR bioimaging taking advantage of the region above 1000 nm (i.e. the second and third biological windows). Further consideration will be given to upcoming probe materials emitting in the NIR-I region (700-950 nm), thus do not possess emissions in these two windows, but have high expectations. Overall, the focus is placed on recent discussions concerning the optimal choice of excitation and emission wavelengths for deep-tissue high-resolution optical bioimaging and on fluorescent bioprobes that have successfully been implemented in in vitro and in vivo applications.

Hybrid Nanostructures for High‐Sensitivity Luminescence Nanothermometry in the Second Biological Window

Hybrid nanostructures containing neodymium-doped nanoparticles and infrared-emitting quantum dots constitute highly sensitive luminescent thermometers operating in the second biological window. They demonstrate that accurate subtissue fluorescence thermal sensing is possible.

Chapter 5:Luminescent Nanothermometry with Lanthanide-doped Nanoparticles

The remarkable optical properties of the trivalent lanthanide ions including their characteristically narrow emission bands, size-independent emission and their capacity to (up)convert near-infrared (NIR) radiation to higher energies spanning the UV–NIR range of the spectrum renders them ideal for biological applications and especially for temperature measurements both in vitro and in vivo. In this chapter, we discuss the fundamental luminescent properties of lanthanide-doped nanoparticles with a special emphasis on temperature-sensitive emissions and their applications in nanothermometry, encompassing ratiometric approaches related to the variation of the relative peak intensities of two transitions or Stark levels of a dopant ion, as well as the temperature-dependent lifetimes of the emitting states.

Highly Efficient Copper Sulfide-Based Near-Infrared Photothermal Agents: Exploring the Limits of Macroscopic Heat Conversion

Among the foreseeable therapeutic approaches at the cellular level, nanoplatform-driven photothermal therapy is a thriving tool for the selective eradication of malignant tissues with minimal side effects to healthy ones. Hence, chemically versatile, near-infrared absorbing plasmonic nanoparticles are distinctly appealing and most sought after as efficient photothermal agents. In this work, a straightforward method to synthesize monodisperse PEGylated copper sulfide nanoparticles of pure covellite (CuS) phase, featuring strong localized surface plasmonic resonance absorption in the near-infrared and flexible surface chemistry, imparted by monomethyl ether polyethylene glycol molecules, is developed and optimized. These nanoparticles show a remarkable photothermal heat conversion efficiency (HCE) of 71.4%, which is among the highest for CuS systems and rivals that of plasmonic noble metal nanostructures. Moreover, through critical evaluation and mathematical modeling of the materials properties and measurement methodology, it is assessed that the calculated HCE values drastically depend on experimental conditions such as wavelength-dependent solvent absorption properties, sol concentration, and optical path. These findings are of paramount relevance to the photothermal community, since they call for a standardization of the procedure for the evaluation of the HCE of proposed photothermal agents, in order to make the reported values universally and reliably comparable.

New confocal microscopy hyperspectral imager for NIR-emitting bioprobes: high spectral resolution for a wide spectral range(Conference Presentation)

Functional nanoscale materials are being extensively investigated for applications in biology and medicine and are ready to make significant contributions in the realization of exciting advancements in diverse areas of diagnostics and therapeutics. Aiming for more accurate, efficient, non-invasive and fast diagnostic tools, the use of near-infrared (NIR) light in the range of the 1st and 2nd biological window (NIR-I: 0.70-0.95 µm; NIR-II: 1.00-1.35 µm) provides deeper penetration depth into biological tissue, better image contrast, reduced phototoxicity and photobleaching. Consequently, NIR-based bioimaging became a quickly emerging field and manifold new NIR-emitting bioprobes have been reported. Since commercially available microscopes are not optimized for this kind of NPs, a new microscopy hyperspectral confocal imager has been developed to cover a broad spectral range (400 to 1700 nm) with high spectral resolution. The smallest spectral variation can be easily monitored thanks to the high spectral resolution (as low as 0.2 nm). This is possible thanks to a combination of an EMCCD and an InGaAs camera with a high resolution spectrometer. An extended number of NPs can be excited with a Ti:Sapphire laser, which provides tunable illumination within 690-1040 nm. Cells and tissues can be mapped in less than 100 ms, allowing in-vivo imaging. As a proof of concept, here we present the preliminary results of the spatial distribution of the fluorescence signal intensity from lanthanide doped nanoparticles incorporated into a system of biological interest. The temperature sub-mm gradient – analyzing the spectral features so gathered through an all-optical route is also thoroughly discussed.