Challenges for optical nanothermometry in biological environments.

Temperature monitoring is useful in medical diagnosis, and essential during hyperthermia treatments to avoid undesired cytotoxic effects. Aiming to control heating doses, different temperature monitoring strategies have been developed, largely based on luminescent materials, a.k.a. nanothermometers. However, for such nanothermometers to work, both excitation and emission light beams must travel through tissue, making its optical properties a relevant aspect to be considered during the measurements. In complex tissues, heterogeneity, and real-time alterations as a result of therapeutic treatment may have an effect on light-tissue interaction, hindering accuracy in the thermal reading. In this Tutorial Review we discuss various methods in which nanothermometers can be used for temperature sensing within heterogeneous environments. We discuss recent developments in optical (nano)thermometry, focusing on the incorporation of luminescent nanoparticles into complex in vitro and in vivo models. Methods formulated to avoid thermal misreading are also discussed, considering their respective advantages and drawbacks.

Is adenosine deaminase (ADA) activity in saliva and serum a more accurate disease detection tool than traditional redox balance parameters in early-lactating dairy cows?

Enzyme adenosine deaminase (ADA) is a marker of inflammation in domestic animals, but it is unclear whether it is a reliable marker of oxidative stress, especially in the transition period in dairy cows. This study aims to assess if ADA and redox status measurements in saliva provide the same utility to detect disease condition as that obtained from serum. Sixty-eight multiparous Holstein cows, between 2 and 3 weeks postpartum were selected. Five study groups were established: control (healthy), and cows with ketosis, mastitis, laminitis, and metritis. The parameters measured were ADA activity, total oxidants (TOS), antioxidants (TAC), and OSi ratio.Regarding redox status, no significant differences arise in both saliva and serum being the correlations negative and not significant. In saliva, ADA activity in healthy cows differs from those with pathological processes, having the lowest activities. In serum, ADA activity is similar in the healthy and ketosis cows, showing the lowest activities meanwhile animals with mastitis, laminitis, or metritis have significantly higher activities. In conclusion, the measurement of ADA activities and redox status in saliva does not give consistent results, being preferable to measure them in serum during the transition period.

Cubic versus hexagonal - phase, size and morphology effects on the photoluminescence quantum yield of NaGdF4:Er3+/Yb3+ upconverting nanoparticles.

Upconverting nanoparticles (UCNPs) are well-known for their capacity to convert near-infrared light into UV/visible light, benefitting various applications where light triggering is required. At the nanoscale, loss of luminescence intensity is observed and thus, a decrease in photoluminescence quantum yield (PLQY), usually ascribed to surface quenching. We evaluate this by measuring the PLQY of NaGdF4:Er3+,Yb3+ UCNPs as a function of size (ca. 15 to 100 nm) and shape (spheres, cubes, hexagons). Our results show that the PLQY of α-phase NaGdF4 Er3+,Yb3+ surpasses that of ß-NaGdF4 for sizes below 20 nm, an observation related to distortion of the crystal lattice when the UCNPs become smaller. The present study also underlines that particle shape must not be neglected as a relevant parameter for PLQY. In fact, based on a mathematical nucleus/hull volumetric model, shape was found to be particularly relevant in the 20 to 60 nm size range of the investigated UCNPs.

Eficacy of Cryotherapy in the Prevention of Oral Mucosistis in Adult Patients with Chemotherapy.

Oral mucositis (OM) is a common side effect of cancer therapies. It causes ulcerative, painful lesions in the oral cavity that can provoke malnutrition, increased risk of infection, longer hospital stays, and seriously affect the quality of life. Cooling the mucosa with oral cryotherapy (OC) during and/or after chemotherapy is the most accessible and tolerable intervention available. The aim of this study is to define the efficacy of OC for preventing OM induced by chemotherapy/radiotherapy in adult patients with cancer. Secondary endpoints include associated problems as pain. A systematic search was performed using the Pubmed, WOS (Web of Science), Cochrane Library, CINAHL, and BVS databases for articles published up to 2010. After inclusion and exclusion criteria were applied, a total of eight articles were analyzed in this review. In seven of the eight articles, the incidence of OM of all grades was significantly lower in the OC group compared with the no-OC group. Use of opioids and level of pain were also significantly reduced. OC is an effective intervention to reduce the incidence of OM induced by chemotherapy as well as the associated severity and pain. Based on these results, OC with only water or with chamomile, associated or not with other mouthwash therapies, is an effective intervention to reduce the incidence of OM induced by chemotherapy as well as the associated severity and pain.

Micro-Raman characterization of Zn-diffused channel waveguides in Tm(3+):LiNbO(3).

In this work micro-Raman scattering experiments have been performed in LiNbO(3):Tm(3+) samples with waveguides fabricated by Zn(2+) in-diffusion. The results shown that Zn(2+) ions enter the lattice in Li(+) sites, but also in interstitial positions. This produces a compaction of the lattice close to the surface of the sample, generating the waveguide. It is shown that this region is surrounded by a different area in which the lattice is relaxed to recover the characteristic lattice parameters of LiNbO(3):Tm(3+).

Engineering efficient upconverting nanothermometers using Eu3+ ions.

Upconversion nanothermometry combines the possibility of optically sensing temperatures in very small areas, such as microfluidic channels or on microelectronic chips, with a simple detection setup in the visible spectral range and reduced heat transfer after near-infrared (NIR) excitation. We propose a ratiometric strategy based on Eu3+ ion luminescence activated through upconversion processes. Yb3+ ions act as a sensitizer in the NIR region (980 nm), and energy is transferred to Tm3+ ions that in turn excite Eu3+ ions whose luminescence is shown to be thermally sensitive. Tridoped SrF2:Yb3+,Tm3+,Eu3+ nanoparticles (average size of 17 nm) show a relative thermal sensitivity of 1.1% K-1 at 25.0 °C, in the range of the best ones reported to date for Ln3+-based nanothermometers based on upconversion emission. The present nanoparticle design allows us to exploit upconversion of lanthanide ions that otherwise cannot be directly excited upon NIR excitation and that may provide operational wavelengths with a highly stable read out to fill the spectral gaps currently existing in upconversion-based nanothermometry.

SERS and plasmonic heating efficiency from anisotropic core/satellite superstructures.

The optical properties of nanoparticle assemblies can be tailored via hybridization of plasmon modes. Isotropic core/satellite superstructures made of spherical nanoparticles are known to exhibit coupled modes with a strongly scattering (radiative) character, and provide hot spots yielding high activity in surface-enhanced Raman scattering (SERS). However, to complement this functionality with plasmonic heating, additional absorbing (non-radiative) modes are required. We introduce herein anisotropic superstructures formed by decorating a central nanorod with spherical satellite nanoparticles, which feature two coupled modes that allow application for both SERS and heating. On the basis of diffuse reflectance spectroscopy, small-angle X-ray scattering (SAXS), and electromagnetic simulations, the origin of the coupled modes is disclosed and thus serves as a basis toward alternative designs of functional superstructures. This work represents a proof-of-principle for the combination of high SERS efficiency with efficient plasmonic heating by near-infrared irradiation.

Heat generation by branched Au/Pd nanocrystals: influence of morphology and composition.

Bimetallic gold-palladium particles were originally proposed as catalysts with tunable reaction rates. Following the development of synthesis routes that offer better control on the morphology and composition of the particles, novel optical sensing functionalities were more recently proposed. Since temperature is a fundamental parameter that interplays with every other proposed application, we studied the light-to-heat conversion ability of Au/Pd bimetallic nanoparticles with a regular octapodal shape. Both compositional (Au-to-Pd ratio) and structural (diagonal tip-to-tip distance and tip width) characteristics were screened and found to be essential control parameters to promote light absorption and efficient conversion into heat. Electromagnetic simulations reveal that the Pd content, and specifically its distribution inside the branched particle geometry, has a profound impact on the optical properties and is an essential criterion for efficient heating. Notably, the optical and photothermal responses are shown to remain stable throughout extended illumination, with no noticeable structural changes to the branched nanocrystals due to heat generation.

Thermal monitoring during photothermia: hybrid probes for simultaneous plasmonic heating and near-infrared optical nanothermometry.

The control of temperature during photothermal therapy is key to preventing unwanted damage in surrounding tissue or post-treatment inflammatory responses. Lack of accurate thermal control is indeed one of the main limitations that hyperthermia techniques present to allow their translation into therapeutic applications. We developed a nanoprobe that allows controlled local heating, combined with in situ nanothermometry. The design of the probe follows a practical rationale that aims at simplifying experimental requirements and exploits exclusively optical wavelengths matching the first and second biological windows in the near-infrared. Methods: Hybrid nanostructures were chemically synthesized, and combine gold nanostars (photothermal agents) with CaF2:Nd3+,Y3+ nanoparticles (luminescent nanothermometers). Both components were simultaneously excited in the near-infrared range, at 808 nm. Following the goal of simplifying the thermal monitoring technique, the luminescent signal was recorded with a portable near-infrared detector. The performance of the probes was tested in 3D tumor spheroids from a human glioblastoma (U87MG) cell line. The location of the beads within the spheroids was determined measuring Nd3+ emission in a commercial Lightsheet microscope, modified in-house to be able to select the required near-infrared wavelengths. The temperature achieved inside the tumor spheroids was deduced from the luminescence of Nd3+, following a protocol that we developed to provide reliable thermal readings. Results: The choice of materials was shown to work as an optically excited hybrid probe. Depending on the illumination parameters, temperature can be controlled in a range between 37 ºC and 100 ºC. The near-infrared emission of nanothermometers also allows microscopic tracking of the hybrid nanostructures, confirming that the probes can penetrate deeper into the spheroid mass. We observed that, application of optical thermometry in biological environments requires often neglected considerations, since the optical signal changes along the optical path. Accordingly, we developed data analysis protocols that guarantee reliable thermal readings. Conclusions: The prepared hybrid probes are internalized in 3D tumor spheroids and can be used to induce cell death through photothermal effects, while simultaneously measuring the local temperature in situ. We show that luminescent thermometry in biomedical applications requires the development of protocols that guarantee accurate readings. Regarding photothermal treatments, we observe a sharp thermal threshold at around 55 ºC (for 10 min treatments) that separates high survival ratio from complete cell death.

Iron-Based Core-Shell Nanowires for Combinatorial Drug Delivery and Photothermal and Magnetic Therapy.

Combining different therapies into a single nanomaterial platform is a promising approach for achieving more efficient, less invasive, and personalized treatments. Here, we report on the development of such a platform by utilizing nanowires with an iron core and iron oxide shell as drug carriers and exploiting their optical and magnetic properties. The iron core has a large magnetization, which provides the foundation for low-power magnetic manipulation and magnetomechanical treatment. The iron oxide shell enables functionalization with doxorubicin through a pH-sensitive linker, providing selective intracellular drug delivery. Combined, the core-shell nanostructure features an enhanced light-matter interaction in the near-infrared region, resulting in a high photothermal conversion efficiency of >80% for effective photothermal treatment. Applied to cancer cells, the collective effect of the three modalities results in an extremely efficient treatment with nearly complete cell death (∼90%). In combination with the possibility of guidance and detection, this platform provides powerful tools for the development of advanced treatments.

Near-infrared triggered generation of reactive oxygen species from upconverting nanoparticles decorated with an organoiridium complex.

Recently, research efforts have been focused on developing near-infrared perturbable nanoparticles to sensitize photostimulable molecules for the production of reactive oxygen species. Research in this direction is looking to broaden the use of photodynamic therapy, an indispensable clinical tool for cancer therapeutics, which relies on the photoexcitation of a suitable photosensitizer, to convert light into reactive oxygen species that are toxic to cells. To date most commercially available photosensitizers are excited with high energy light (UV or visible) presenting disadvantages that limit the clinical use of this technique to cancers that are on or near the surface of the skin. Here, we develop a hybrid platform capable of near-infrared triggered generation of reactive oxygen species. This hybrid nanostructure is based on LiYF4:Tm3+,Yb3+ nanoparticles, which are capable of producing strong UV emissions, following excitation at 980 nm, through a multiphoton process known as upconversion. When appropriately surface functionalized with an organoiridium complex, excitation at 980 nm produces a strong UV emission, which is absorbed by the organoiridium molecules on the surface, in turn generating reactive oxygen species. Moreover, the effect of the organoiridium concentration on the surface of the upconverting nanoparticles as well as the nature of the sensitization process is discussed.

Sensitive Detection of ssDNA Using an LRET-Based Upconverting Nanohybrid Material.

Water-dispersible, optical hybrid nanoparticles are preferred materials for DNA biosensing due to their biocompatibility. Upconverting nanoparticles are highly desirable optical probes in sensors and bioimaging owing to their sharp emission intensity in the visible region. We herein report a highly sensitive ss-DNA detection based on an energy transfer system that uses a nanohybrid material synthesized by doping NaYF4:Tm(3+)/Yb(3+) upconverting nanoparticles (UCNPs) on silica coated polystyrene-co-acrylic acid (PSA) nanoparticles (PSA/SiO2) as the donor, and gold nanoparticles (AuNPs) decorated with Ir(III) complex as the acceptor. UCNPs tagged on PSA/SiO2 and the cyclometalated Ir(III)/AuNP conjugates were then linked through the ss-DNA sequence. Sequential addition of the target DNA to the probe molecular beacon complex resulted in the separation of the optical nanohybrid material and the quencher, leading to a measurable increase in the blue fluorescence emission intensity. Our results have shown a linear relationship between the fluorescence intensity and target DNA concentration down to the picomolar.

Tuning from blue to magenta the up-converted emissions of YF3:Tm3+/Yb3+ nanocrystals.

Monodisperse YF3:Tm3+/Yb3+ nanocrystals have been synthesized to explore the visible up-converting properties under near infrared (975 nm) excitation. It has been found that the nanoparticles exhibit intense red up-converted emissions, in addition to the characteristic UV and blue Tm3+-bands. It is demonstrated that, by carefully selecting Tm3+ and Yb3+ contents, the relative intensity of the different emissions can be changed producing an overall emission colour that can be tuned from blue to magenta.