Enrichment of hepatocytes in a HepaRG culture using spatially selective photodynamic treatment

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Single-Cell Biodetection by Upconverting Microspinners

This is the peer reviewed version of the following article: Ortiz‐Rivero, E., Prorok, K., Skowickł, M., Lu, D., Bednarkiewicz, A., Jaque, D., & Haro‐González, P. (2019). Single‐Cell Biodetection by Upconverting Microspinners. Small, 15(46), 1904154, which has been published in final form at https://doi.org/10.1002/smll.201904154. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsNear-infrared-light-mediated optical tweezing of individual upconverting particles has enabled all-optical single-cell studies, such as intracellular thermal sensing and minimally invasive cytoplasm investigations. Furthermore, the intrinsic optical birefringence of upconverting particles renders them light-driven luminescent spinners with a yet unexplored potential in biomedicine. In this work, the use of upconverting spinners is showcased for the accurate and specific detection of single-cell and single-bacteria attachment events, through real-time monitoring of the spinners rotation velocity of the spinner. The physical mechanisms linking single-attachment to the angular deceleration of upconverting spinners are discussed in detail. Concomitantly, the upconversion emission generated by the spinner is harnessed for simultaneous thermal sensing and thermal control during the attachment event. Results here included demonstrate the potential of upconverting particles for the development of fast, high-sensitivity, and cost-effective systems for single-cell biodetectionThis work was partially supported by the Ministerio de Economía y Competitividad de España (MAT2016‐75362‐C3‐1‐R) and by the Instituto de Salud Carlos III (PI16/00812), by the Comunidad Autónoma de Madrid (B2017/BMD‐3867RENIMCM), and cofinanced by the European Structural and investment fund Additional funding was provided by COST action CM1403. D.L. thanks the Chinese Scholarship Council for financial support. K.P. acknowledges the support from Foundation for Polish Science (FNP) under START program. A.B. acknowledges financial support from NCN OPUS DEC‐2017/27/B/ST7/01255 gran

Laser refrigeration by an Ytterbium-doped NaYF4 microspinner

Thermal control of liquids with high (micrometric) spatial resolution is required for advanced research such as single molecule/cell studies (where temperature is a key factor) or for the development of advanced microfluidic devices (based on the creation of thermal gradients at the microscale). Local and remote heating of liquids is easily achieved by focusing a laser beam with wavelength adjusted to absorption bands of the liquid medium or of the embedded colloidal absorbers. The opposite effect, that is highly localized cooling, is much more difficult to achieve. It requires the use of a refrigerating micro-/nanoparticle which should overcome the intrinsic liquid heating. Remote monitoring of such localized cooling, typically of a few degrees, is even more challenging. In this work, a solution to both problems is provided. Remote cooling in D2O is achieved via anti-Stokes emission by using an optically driven ytterbium-doped NaYF4 microparticle. Simultaneously, the magnitude of cooling is determined by mechanical thermometry based on the analysis of the spinning dynamics of the same NaYF4 microparticle. The angular deceleration of the NaYF4 particle, caused by the cooling-induced increase of medium viscosity, reveals liquid refrigeration by over −6 K below ambient conditionsThis work was supported by the Ministerio de Ciencia e Innovación de España (PID2019-106211RB-I00 and PID2019-105195RA-I00) and by Universidad Autónoma de Madrid and Comunidad Autónoma de Madrid (SI1/PJI/2019-00052). E.O.R gratefully acknowledges the financial support provided by the Spanish Ministerio de Universidades, through the FPU program (FPU19/04803). K.P. acknowledges financial support from NCN, Poland, grant number 2018/31/D/ST5/0132

Upconversion FRET quantitation: the role of donor photoexcitation mode and compositional architecture on the decay and intensity based responses

Lanthanide-doped colloidal nanoparticles capable of photon upconversion (UC) offer long luminescence lifetimes, narrowband absorption and emission spectra, and efficient anti-Stokes emission. These features are highly advantageous for Forster Resonance Energy Transfer (FRET) based detection. Upconverting nanoparticles (UCNPs) as donors may solve the existing problems of molecular FRET systems, such as photobleaching and limitations in quantitative analysis, but these new labels also bring new challenges. Here we have studied the impact of the core-shell compositional architecture of upconverting nanoparticle donors and the mode of photoexcitation on the performance of UC-FRET from UCNPs to Rose Bengal (RB) molecular acceptor. We have quantitatively compared luminescence rise and decay kinetics of Er3+ emission using core-only NaYF4: 20% Yb, 2% Er and core-shell NaYF4: 20% Yb @ NaYF4: 20% Yb, 5% Er donor UCNPs under three photoexcitation schemes: (1) direct short-pulse photoexcitation of Er3+ at 520 nm; indirect photoexcitation of Er3+ through Yb3+ sensitizer with (2) 980 nm short (5-7 ns) or (3) 980 nm long (4 ms) laser pulses. The donor luminescence kinetics and steady-state emission spectra differed between the UCNP architectures and excitation schemes. Aiming for highly sensitive kinetic upconversion FRET-based biomolecular assays, the experimental results underline the complexity of the excitation and energy-migration mechanisms affecting the Er3+ donor responses and suggest ways to optimize the photoexcitation scheme and the architecture of the UCNPs used as luminescent donors

Optical forces at the nanoscale: Size and electrostatic effects

“This document is the Accepted Manuscript version of a Published Work that appeared in final form in Nano Letters copyright © American Chemical Society after peer review and technical editing by publisher. To acces final work see Optical Forces at the Nanoscale: Size and Electrostatic Effects, Nano Letters, 18.1 (2018), pags. 602-609. http://doi.org/10.1021/acs.nanolett.7b04804"The reduced magnitude of the optical trapping forces exerted over sub-200 nm dielectric nanoparticles complicates their optical manipulation, hindering the development of techniques and studies based on it. Improvement of trapping capabilities for such tiny objects requires a deep understanding of the mechanisms beneath them. Traditionally, the optical forces acting on dielectric nanoparticles have been only correlated with their volume, and the size has been traditionally identified as a key parameter. However, the most recently published research results have shown that the electrostatic characteristics of a sub-100 nm dielectric particle could also play a significant role. Indeed, at present it is not clear what optical forces depend. In this work, we designed a set of experiments in order to elucidate the different mechanism and properties (i.e., size and/or electrostatic properties) that governs the magnitude of optical forces. The comparison between experimental data and numerical simulations have shown that the double layer induced at nanoparticle’s surface, not considered in the classical description of nanoparticle’s polarizability, plays a relevant role determining the magnitude of the optical forces. Here, the presented results constitute the first step toward the development of the dielectric nanoparticle over which enhanced optical forces could be exerted, enabling their optical manipulation for multiples purposes ranging from fundamental to applied studiesThis work has been supported by the Spanish Ministerio de Economia y Competitividad (project Nr.MAT2016-75362-C3-1-R), FIS2015-69295-C3-3-P and the “María de Maeztu” Program Ref: MDM-2014-0377. P.R.S. thanks MINECO and the Fondo Social Europeo (FSE) for the “Promoción del talento y su Empleabilidad en I+D+i” statal program (BES-2014-069410). K.P. acknowledges financial support from the National Science Center Poland (NCN) under the ETIUDA doctoral scholarship on the basis of decision number DEC-2014/12/T/ST5/00646. A.B. acknowledges the statutory financial support from ILT&SR PAS. P.H.G. thanks MINECO for the Juan de la Cierva program (IJCI-2015- 24551). The European Upconversion Network (COST Action CM1403) is acknowledge

Highly sensitive luminescence nanothermometry and thermal imaging facilitated by phase transition

Currently available temperature measurements or imaging at nano-micro scale are limited to fluorescent molecules and luminescent nanocrystals, whose spectral properties respond to temperature variation. The principle of operation of these conventional temperature probes is typically related to temperature induced multiphonon quenching or temperature dependent energy transfers, therefore, above 12%/K sensitivity and high thermal resolution remain a serious challenge. Here we demonstrate a novel class of highly sensitive thermographic phosphors operating in room temperature range with sub-kelvin thermal resolution, whose temperature readings are reproducible, luminescence is photostable and brightness is not compromised by thermal quenching. Corroborated with phase transition structural characterization and high spatio-temporal temperature imaging, we demonstrated that optically active europium ions are highly and smoothly susceptible to monoclinic to tetragonal phase transition in nanocrystalline (54 ± 14 nm) LiYO2 host, which is evidenced by changed number and the splitting of Stark components as well as by smooth variation of contribution between magnetic and electric dipole transitions. Further, reducing the size of phosphor from bulk to nanocrystalline matrix, shifted the phase transition temperature from 100 °C down to room temperature. These findings provide insights into the mechanism underlaying phase transition based luminescence nanothermometry and motivate future research toward new, highly sensitive, high temporal and spatial resolution nano-thermometers aiming at precise studying heat generation or diffusion in numerous biological and technology applications

Giant nonlinear optical responses from photon avalanching nanoparticles

Avalanche phenomena leverage steeply nonlinear dynamics to generate disproportionately high responses from small perturbations and are found in a multitude of events and materials, enabling technologies including optical phase-conjugate imaging, infrared quantum counting, and efficient upconverted lasing. However, the photon avalanching (PA) mechanism underlying these optical innovations has been observed only in bulk materials and aggregates, and typically at cryogenic temperatures, limiting its utility and impact. Here, we report the realization of PA at room temperature in single nanostructures--small, Tm-doped upconverting nanocrystals--and demonstrate their use in superresolution imaging at near-infrared (NIR) wavelengths within spectral windows of maximal biological transparency. Avalanching nanoparticles (ANPs) can be pumped by continuous-wave or pulsed lasers and exhibit all of the defining features of PA. These hallmarks include excitation power thresholds, long rise time at threshold, and a dominant excited-state absorption that is >13,000x larger than ground-state absorption. Beyond the avalanching threshold, ANP emission scales nonlinearly with the 26th power of pump intensity. This enables the realization of photon-avalanche single-beam superresolution imaging (PASSI), achieving sub-70 nm spatial resolution using only simple scanning confocal microscopy and before any computational analysis. Pairing their steep nonlinearity with existing superresolution techniques and computational methods, ANPs allow for imaging with higher resolution and at ca. 100-fold lower excitation intensities than is possible with other probes. The low PA threshold and exceptional photostability of ANPs also suggest their utility in a diverse array of applications including sub-wavelength bioimaging, IR detection, temperature and pressure transduction, neuromorphic computing, and quantum optics.Comment: 14 pages, 4 figure