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Gold Nanomaterials at Work in Biomedicine *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Xuan Yang, Miaoxin Yang, Pang Bo, Madeline Vara, Younan Xia
Compared to organic dyes, which have also been explored as photothermal agents for PTT [630, 631], Au nanostructures offer a number of distinctive advantages: (i) higher stability against photobleaching, (ii) better targeting capability due to their nanoscale sizes, and (iii) much greater absorption cross sections and thus higher photothermal conversion efficiency [632, 633]. In addition, Au nanostructures can serve as contrast agents for various imaging techniques, making it possible to achieve imaging-guided therapy. The high photothermal conversion efficiency of Au nanostructures minimizes the required particle dosage for PTT. This makes Au a more attractive choice as a hyperthermia-inducing agent over magnetic nanomaterials, which are also known to induce hyperthermia under an alternating magnetic field, but require a relatively high dose for effective treatment (10–100 mg/mm3 tumor) [634]. It is worth emphasizing that Au nanostructures with strong absorption in the NIR region (including nanorods, nanoshells, nanocages, and nanostars) are particularly well-suited for PTT, owing to the penetration depth of lasers at such wavelengths.
Photodynamic Therapy
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
In addition to interacting with molecular oxygen to produce single oxygen, the excited-state photosensitizer molecule can undergo a side reaction leading to loss of absorbance and photosensitizing ability. This process of photobleaching can modify the reciprocity between photosensitizer level and light, since with irradiation there will be a progressive loss of sensitizer. Photobleaching therefore places a limit on the total amount of phototoxicity (PTmax) that can be produced by a given level of photosensitizer for a given light dose. While this can be a problem, it can also be an advantage. Photosensitizer near the surface of the tissue will absorb light and decrease the illumination at a depth. As photosensitizer near the surface bleaches, more light will penetrate more deeply into the tissue.
Check the Cancer Before It Checks You Out
Published in Prakash Srinivasan Timiri Shanmugam, Understanding Cancer Therapies, 2018
Another photosensitizer, hypericin, has shown excellent fluorescence diagnostic properties in oral cavity cancers. Hypericin is a plant-based photosensitizer that accumulates in abnormal cells including tumor cells. Hypericin fluorescence diagnostic imaging as a technique can facilitate guided biopsies in the clinic, thereby reducing the number of biopsies taken. It can also provide visualization of tumor margins during surgical procedures and assist for same-day diagnosis in the clinic. Studies have reported that hypericin fluorescence can provide improved specificity and is subject to reduced photobleaching compared to 5-ALA (Olivo et al. 2011).
Surface modified NIR magnetic nanoprobes for theranostic applications.
Published in Expert Opinion on Drug Delivery, 2021
Ramya Dhandapani, Ayyappan Sathya, Swaminathan Sethuraman, Anuradha Subramanian
FIO dispersed in phantom agar showed strong NIR emission evidencing traceability even at lower concentrations (0.01 mg/mL) (Figure 5(g)). Also, cells labeled with various concentrations of FIO showed an increasing Fe and ICG content with respect to increasing concentration (Supplementary table 2). Faster uptake and enhanced cellular localization would promote enhanced sensitivity and accuracy in tracing cells. Images of FIO loaded cells embedded on phantom agar showed strong NIR emission proving potentials of cell tracking and localization even at deeper tissues (Figure 5(g)). Zeng et al. used ICG loaded mesoporous silica nanoparticles to target residual microtumors and satellite lesions that are lesser than 1 mm in mice. However, a shorter half-life restricted its traceability after 24 h [6]. Interestingly, FIO showed photostability for over 5 days when compared to free ICG, which underwent photobleaching/degradation within 6 h under aqueous conditions (Figure 5(g)). Similarly, ICGylation of magnetic nanoparticles-labeled-dendritic cells showed fluorescence upto 3 days [30]. This can be correlated to the prevention of aggregation of ICG molecules in solution that causes photobleaching and integrating them on the surface of HIO has facilitated longer fluorescence signals.
An Immunosuppressive Effect of Melanoma-derived Exosomes on NY-ESO-1 Antigen-specific Human CD8+ T Cells is Dependent on IL-10 and Independent of BRAFV600E Mutation in Melanoma Cell Lines
Published in Immunological Investigations, 2020
ShinLa Shu, Junko Matsuzaki, Muzamil Y. Want, Alexis Conway, Shawna Benjamin-Davalos, Cheryl L. Allen, Marina Koroleva, Sebastiano Battaglia, Adekunle Odunsi, Hans Minderman, Marc S. Ernstoff
Labeled HMEX were acquired using an imaging flow cytometer ImageStream MK-II (Millipore, USA). About 5,000 individual images were recorded; spectral compensation and analyses were performed using ImageStream Data Exploration Software. Unlike fluorescent NTA which necessitated the need for the PD-L1 antibody to be conjugated to photostable Qdot 705 (see Results section), the shorter excitation of the fluorochromes during imaging flow cytometry does not present a problem with regards to photobleaching. Therefore, an anti-PD-L1 antibody directly conjugated to Brilliant violet 421 (BV421; BD, USA) could be used. The antibody was clone-matched with the antibody used during fluorescent NTA and used at a dilution factor of 1:100. For an antibody only control, BV421 antihuman-PD-L1 antibody was diluted 1:100, without the addition of exosomes. To determine which population in the image corresponded to exosomes, the test sample was then lysed with 0.5% Triton-X prepared in 1X PBS, mixed by inverting the tube several times over the course of 10 minutes and re-analyzed by ImageStream for the loss of any specific population.
Towards defining reference materials for measuring extracellular vesicle refractive index, epitope abundance, size and concentration
Published in Journal of Extracellular Vesicles, 2020
Joshua A. Welsh, Edwin van der Pol, Britta A. Bettin, David R. F. Carter, An Hendrix, Metka Lenassi, Marc-André Langlois, Alicia Llorente, Arthur S. van de Nes, Rienk Nieuwland, Vera Tang, Lili Wang, Kenneth W. Witwer, Jennifer C. Jones
NTA size particles not by a single intensity measurement, as in flow cytometry, but rather by tracking the Brownian motion of particles (multiple measurements) [21]. Size is then inferred from the Stokes-Einstein equation. NTA does, however, rely on optical intensity to track particles over a sufficient length of time to derive an accurate size. Determining the limit of sensitivity for NTA would therefore require light scatter modelling or fluorescence calibration, depending on tracking mode, as well as some way to account for: (1) the movement of particles in and out of the field of view, (2) changing intensities and (3) the ability of the instrument to track them. In light scatter mode, intensity depends on refractive index and illumination wavelength. The enumeration of particles is then affected by the camera’s varying noise, fluctuating at a pixel level over time, over which the software must identify and track a particle over several time frames. In fluorescence mode, additional information includes the amount of dye and rate of photobleaching. Currently, there is no demonstrated method to express limit of sensitivity for NTA in standard units, irrespective of factors such as refractive index of fluorescence intensity, such that comparisons could be made across instrumentation.