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This work reports new soft photothermal materials based on liquid crystalline nickel bis(dithiolene) complexes bearing pentakis(dodecyloxy)triphenylene units in which the triphenylene core and the metal complex are linked through -(CH2)n- (n = 2, 4, 10) connectors. The mesomorphic properties of these materials can be modulated by the length of the linker. All the complexes, except the derivative with the longest linker, show columnar mesomorphism, characterized by polarized optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray scattering studies. The structure of the mesophases contains segregated organic and inorganic columns supported respectively by π-stacking of the triphenylene discs and weak intermolecular nickel-sulfur interactions. The photothermal activity was studied on the complex with n = 2. Under laser irradiation with a power density of 0.098 W cm-2 for just over a minute an increase in temperature of ΔT = 50 °C was achieved. This produced the melting of the crystalline solid to give rise to the columnar mesophase, where, interestingly, the photothermal effect was enhanced. Quantum chemical calculations have also been performed to gain insight into the supramolecular self-assembled columnar structure at the molecular level, as well as into the photothermal behavior. [ABSTRACT FROM AUTHOR]

There is a continuous vivid search for biocompatible hybrid magneto-optical nanoprobes with high heating and photoluminescence efficiencies for photothermal theranostics. Herein, two tailored multipurpose hybrid PEGylated gold (Au) and silver sulfide (Ag2S) magnetic iron oxide nanoparticle formulations (Au-PEG-MNPs and Ag2S-PEG-MNPs) with unique opto-magnetic properties for simultaneous photothermal therapy were prepared. The physiochemical properties of the hybrid MNPs were fully characterized using various electronic and spectroscopic techniques, showing colloidal stabilized small-sized nanoparticles (core sizes = 10 nm, DH = 200 nm) with high saturation magnetizations (Ms up to 85 emu/g) and superparamagnetic behavior. Thermal effects in response to an alternating magnetic field (AMF) at different frequencies (f = 25–300 kHz) and field intensities (H = 12 and 24 kA/m) were assessed using an ultrafast magnetometric method, revealing high heating efficiencies with distinctive heating responses. The "optothermal" efficacies were then evaluated using a unique experimental setup equipped with a highly sensitive thermal camera for recording temperatures in real time, along with a simultaneous clinically safe near-infrared (NIR) laser (λ = 808 nm and power = 0.5 W cm–2) and AMF (H = 12 kA/m, f = 180 kHz) dual effect. Remarkably, when irradiated with an NIR laser and AMF, both hybrid Au- and Ag2S-PEG-MNPs displayed superior heat induction power (SAR = 384 and 441 W/g), rapidly reaching hyperthermia temperatures of 42 °C in only a few seconds. Temperatures could reach up to 75 °C for Au-PEG-MNPs and 90 °C for Ag2S-PEG-MNPs in only 5 min. Such superior heating efficiencies for the hybrid MNPs increased ∼1.5–2 times under concurrent irradiation compared to the action by laser alone. Finally, cytotoxicity assays against cancerous and normal cells confirmed the safety profiles and low toxicities of the hybrid nanoformulations. This unique synergistic platform has great potential to be utilized for multimodal photothermal therapy with reduced field strengths, laser intensities, and short irradiation times in the unceasing search for tangible hyperthermal clinical nanoprobes. [ABSTRACT FROM AUTHOR]

The technological advancements made in optics and semiconductors (e.g., cameras and laser diodes) working with infrared have brought interest in optical bioimaging back to the forefront of research investigating in vivo medical imaging techniques. The definition of the near-infrared transparency windows has turned optical imaging into more than just a method for topical imaging applications. Moreover, this has focused attention back to tissue fluorescence, emissions by tissues and organs that occur when excited by external illumination sources. Most endogenous fluorophores emit in the blue to green range of the electromagnetic spectrum and the resulting tissue fluorescence can be employed in studies from cells to tissue metabolism or avoided by shifting to the red if seen as unwanted autofluorescence. With the more recent move to infrared, it was discovered that autofluorescence is not limited to the visible but also strongly affects in vivo imaging in the infrared. In this Tutorial, we give an overview on tissue fluorescence and tissue interactions with excitation light as well as their effect on in vivo imaging. Furthermore, potential sources of tissue fluorescence in the near-infrared are identified and we describe approaches for successful biomedical imaging in the biological windows, taking into consideration infrared autofluorescence and summarizing techniques for avoiding it in in vivo imaging experiments. [ABSTRACT FROM AUTHOR]

Lifetime‐based luminescence thermometry has been shown to enable accurate deep‐tissue monitoring of temperature changes – even at the in vivo level – in a minimally invasive way. However, major limiting factors to the performance of this approach are short lifetimes and poor brightness. These are characteristics, respectively, of semiconductor nanocrystals and lanthanide‐doped nanoparticles, of which most luminescent nanothermometers are made. To address these limitations, the composition of luminescent nanothermometers co‐doped with transition metal (Mn5+) and Er3+ ions are designed and optimized. The salient features of these nanothermometers are strong, near‐infrared emission and long, temperature‐dependent photoluminescence lifetime. The potential of these luminescent nanophosphors for thermal sensing is then showcased by monitoring a thermal gradient using a one‐of‐a‐kind piece of equipment designed for lifetime‐based luminescence thermometry measurements. The combination of the newly developed nanothermometers and the custom‐made instrument allows for obtaining 2D thermal maps both in the absence and presence of tissue phantoms mimicking the optical properties of the skin. The results presented in this study thus provide credible foundations for the deployment of lifetime‐based thermometry for accurate deep‐tissue thermal mapping at the preclinical level. [ABSTRACT FROM AUTHOR]

Simple Summary: This work describes a nanoplatform for deep-tissue photodynamic therapy (PDT) and imaging using upconverting nanoparticles functionalized with eosin Y (EY), a photosensitizer (PS) that have been demonstrated to be effective even in hypoxic environments. These structures take advantage of the capability of the nanoparticles to be excited by 800 nm near infrared light, where penetration is higher in comparison with visible light commonly used in PDT, and the thermal load is minimum. Additionally, the combination with UCNPs enables the transport of EY into the cell, which is not possible for EY alone. The generation of reactive oxygen species (ROS) under 800 nm light inside the cell becomes therefore possible based on upconversion and energy transfer processes. These UCNPs also present long lasting infrared fluorescence under 808 nm excitation, thus enabling their use as deep tissue bioimaging agent during PDT. Functionalized upconverting nanoparticles (UCNPs) are promising theragnostic nanomaterials for simultaneous therapeutic and diagnostic purposes. We present two types of non-toxic eosin Y (EY) nanoconjugates derived from UCNPs as novel nanophotosensitizers (nano-PS) and deep-tissue bioimaging agents employing light at 800 nm. This excitation wavelength ensures minimum cell damage, since the absorption of water is negligible, and increases tissue penetration, enhancing the specificity of the photodynamic treatment (PDT). These UCNPs are uniquely qualified to fulfil three important roles: as nanocarriers, as energy-transfer materials, and as contrast agents. First, the UCNPs enable the transport of EY across the cell membrane of living HeLa cells that would not be possible otherwise. This cellular internalization facilitates the use of such EY-functionalized UCNPs as nano-PS and allows the generation of reactive oxygen species (ROS) under 800 nm light inside the cell. This becomes possible due to the upconversion and energy transfer processes within the UCNPs, circumventing the excitation of EY by green light, which is incompatible with deep tissue applications. Moreover, the functionalized UCNPs present deep tissue NIR-II fluorescence under 808 nm excitation, thus demonstrating their potential as bioimaging agents in the NIR-II biological window. [ABSTRACT FROM AUTHOR]

Ag2S nanodots have already been demonstrated as promising near-infrared (NIR-II, 1.0–1.45 μm) emitting nanoprobes with low toxicity, high penetration and high resolution for in vivo imaging of, for example, tumors and vasculature. In this work, we have systematically investigated the potential application of functionalized Ag2S nanodots for accurate imaging of damaged myocardium tissues after a myocardial infarction induced by either partial or global ischemia. Ag2S nanodots surface-functionalized with the angiotensin II peptide (ATII) have shown over 10-fold enhanced binding efficiency to damaged tissues than non-specifically (PEG) functionalized Ag2S nanodots due to their interaction with the upregulated angiotensin II receptor type I (AT1R). It is demonstrated how the NIR-II images generated by ATII-functionalized Ag2S nanodots contain valuable information about the location and extension of damaged tissue in the myocardium allowing for a proper identification of the occluded artery as well as an indirect evaluation of the damage level. The potential application of Ag2S nanodots in the near future for in vivo imaging of myocardial infarction was also corroborated by performing proof of concept whole body imaging experiments. [ABSTRACT FROM AUTHOR]