Gold nanoshells: Contrast agents for cell imaging by cardiovascular optical coherence tomography

Optical coherence tomography (OCT) has gained considerable attention in interventional cardiovascular medicine and is currently used in clinical settings to assess atherosclerotic lesions and to optimize stent placement. Artery imaging at the cellular level constitutes the first step towards cardiovascular molecular imaging, which represents a major advance in the development of personalized noninvasive therapies. In this work, we demonstrate that cardiovascular OCT can be used to detect individual cells suspended in biocompatible fluids. Importantly, the combination of this catheter-based clinical technique with gold nanoshells (GNSs) as intracellular contrast agents led to a substantial enhancement in the backscattered signal produced by individual cells. This cellular contrast enhancement was attributed to the large backscattering cross-section of GNSs at the OCT laser wavelength (1,300 nm). A simple intensity analysis of OCT cross-sectional images of suspended cells makes it possible to identify the sub-population of living cells that successfully incorporated GNSs. The generalizability of this method was demonstrated using two different cell lines (HeLa and Jurkat cells). This work provides novel insights into cardiovascular molecular imaging using specifically modified GNSs.

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Preliminary results on the identification of ultraviolet and beta radiation exposure in KCl:Eu single crystals by thermoluminescence

The thermoluminescence (TL) sensitivity to ionising (beta source) and non-ionising (UV) radiation on KCl:Eu²⁺ single crystals has been investigated. The different shapes of the TL glow curves allow us to detect specific peaks (over 220–250 °C) due to UV exposure that exhibit a negligible contribution associated with ionising radiation. The UV-induced TL emission could be deconvoluted into five groups of components peaked at about 120, 150, 210, 250 and 330 °C assuming first order kinetic processes. Dose saturation and linearity region have been determined for a wavelength of 254.7 nm. The effect of several cycles of UV irradiation processes on the linearity of the high energy ultraviolet KCl:Eu²⁺ dosimeter has been also studied to determine the potential reusability.     

In Vivo Subcutaneous Thermal Video Recording by Supersensitive Infrared Nanothermometers

Some of the old and unrealizable dreams of biomedicine have become possible thanks to the appearance of novel advanced materials such as luminescent nanothermometers, nanoparticles capable of providing a contactless thermal reading through their light emission properties. Luminescent nanothermometers have already been demonstrated to be capable of in vivo subcutaneous punctual thermal reading but their real application as diagnosis tools still requires demonstrating their actual capacity for the acquisition of in vivo, time‐resolved subcutaneous thermal images. The transfer from 1D to 2D subcutaneous thermal sensing is blocked in the last years mainly due to the lack of high sensitivity luminescent nanothermometers operating in the infrared biological windows. This work demonstrates how core/shell engineering, in combination with selective rare earth doping, can be used to develop supersensitive infrared luminescent nanothermometers. Erbium, thulium, and ytterbium core–shell LaF₃ nanoparticles, operating within the biological windows, provide thermal sensitivities as large as 5% °C^?1. This “record” sensitivity has allowed for the final acquisition of subcutaneous thermal videos of a living animal. Subsequent analysis of thermal videos allows for an unequivocal determination of intrinsic properties of subcutaneous tissues, opening the venue to the development of novel thermal imaging‐based diagnosis tools.     

Single‐Cell Biodetection by Upconverting Microspinners

Near‐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 biodetection.     

High-Sensitivity Fluorescence Lifetime Thermal Sensing Based on CdTe Quantum Dots

The potential use of CdTe quantum dots as luminescence nano-probes for lifetime fluorescence nano-thermometry is demonstrated. The maximum thermal sensitivity achievable is strongly dependent on the quantum dot size. For the smallest sizes (close to 1 nm) the lifetime thermal sensitivity overcomes those of conventional nano-probes used in fluorescence lifetime thermometry.     

Optical properties of single doped Cr and co-doped Cr–Nd aluminum tantalum tellurite glasses

The optical properties for single doped Cr³⁺ and co-doped Cr³⁺–Nd³⁺ aluminum tantalum tellurite glasses have been studied as a function of temperature. For the single doped glass, the existence of two bands in the emission spectra at low temperature indicates the presence of two different sites for the Cr³⁺ ions, labelled as usual as low- and high-field sites. The broad band centred in the Near Infrared region, corresponds to low-field sites transition ⁴T₂→⁴A₂, and the narrow band centred at approximately 715 nm to the high-field sites transition ²E→⁴A₂. The emission intensity for both high- and low-field sites shows a strong decrease with increasing temperature, with the emission for the former sites vanishing at RT. In both cases the quenching observed with the increase of temperature can be ascribed to the presence of non-radiative relaxation mechanisms. Experimental observations for the co-doped glass show that both radiative and non-radiative energy transfer processes from Cr³⁺ to Nd³⁺ are present.     

Infrared‐Emitting QDs for Thermal Therapy with Real‐Time Subcutaneous Temperature Feedback

Nowadays, one of the most exciting applications of nanotechnology in biomedicine is the development of localized, noninvasive therapies for diverse diseases, such as cancer. Among them, nanoparticle‐based photothermal therapy (PTT), which destroys malignant cells by delivering heat upon optical excitation of nanoprobes injected into a living specimen, is emerging with great potential. Two main milestones that must be reached for PTT to become a viable clinical treatment are deep penetration of the triggering optical excitation and real‐time accurate temperature monitoring of the ongoing therapy, which constitutes a critical factor to minimize collateral damage. In this work, a yet unexplored capability of near‐infrared emitting semiconductor nanocrystals (quantum dots, QDs) is demonstrated. Temperature self‐monitored ­QD‐based PTT is presented for the first time using PbS/CdS/ZnS QDs emitting in the second biological window. These QDs are capable of acting, simultaneously, as photothermal agents (heaters) and high‐resolution fluorescent thermal sensors, making it possible to achieve full control over the intratumoral temperature increment during PTT. The differences observed between intratumoral and surface temperatures in this comprehensive investigation, through different irradiation conditions, highlight the need for real‐time control of the intratumoral temperature that allows for a dynamic adjustment of the treatment conditions in order to maximize the efficacy of the therapy.