Early in vivo detection of denervation-induced atrophy by luminescence transient nanothermometry

Denervation induces skeletal muscle atrophy due to the loss of control and feedback with the nervous system. Unfortunately, muscle atrophy only becomes evident days after the denervation event when it could be irreversible. Alternative diagnosis tools for early detection of denervation-induced muscle atrophy are, thus, required. In this work, we demonstrate how the combination of transient thermometry, a technique already used for early diagnosis of tumors, and infrared-emitting nanothermometers makes possible the in vivo detection of the onset of muscle atrophy at short (<1 day) times after a denervation event. The physiological reasons behind these experimental results have been explored by performing three dimensional numerical simulations based on the Pennes' bioheat equation. It is concluded that the alterations in muscle thermal dynamics at the onset of muscle atrophy are consequence of the skin perfusion increment caused by the alteration of peripheral nervous autonomous system. This work demonstrates the potential of infrared luminescence thermometry for early detection of diseases of the nervous system opening the venue toward the development of new diagnosis tools.

Neural Networks Push the Limits of Luminescence Lifetime Nanosensing

Luminescence lifetime-based sensing is ideally suited to monitor biological systems due to its minimal invasiveness and remote working principle. Yet, its applicability is limited in conditions of low signal-to-noise ratio (SNR) induced by, e.g., short exposure times and presence of opaque tissues. Herein this limitation is overcome by applying a U-shaped convolutional neural network (U-NET) to improve luminescence lifetime estimation under conditions of extremely low SNR. Specifically, the prowess of the U-NET is showcased in the context of luminescence lifetime thermometry, achieving more precise thermal readouts using Ag2 S nanothermometers. Compared to traditional analysis methods of decay curve fitting and integration, the U-NET can extract average lifetimes more precisely and consistently regardless of the SNR value. The improvement achieved in the sensing performance using the U-NET is demonstrated with two experiments characterized by extreme measurement conditions: thermal monitoring of free-falling droplets, and monitoring of thermal transients in suspended droplets through an opaque medium. These results broaden the applicability of luminescence lifetime-based sensing in fields including in vivo experimentation and microfluidics, while, hopefully, spurring further research on the implementation of machine learning (ML) in luminescence sensing.

Ion-induced bias in Ag2S luminescent nanothermometers

Luminescence nanothermometry allows measuring temperature remotely and in a minimally invasive way by using the luminescence signal provided by nanosized materials. This technology has allowed, for example, the determination of intracellular temperature and in vivo monitoring of thermal processes in animal models. However, in the biomedical context, this sensing technology is crippled by the presence of bias (cross-sensitivity) that reduces the reliability of the thermal readout. Bias occurs when the impact of environmental conditions different from temperature also modifies the luminescence of the nanothermometers. Several sources that cause loss of reliability have been identified, mostly related to spectral distortions due to interaction between photons and biological tissues. In this work, we unveil an unexpected source of bias induced by metal ions. Specifically, we demonstrate that the reliability of Ag2S nanothermometers is compromised during the monitoring of photothermal processes produced by iron oxide nanoparticles. The observed bias occurs due to the heat-induced release of iron ions, which interact with the surface of the Ag2S nanothermometers, enhancing their emission. The results herein reported raise a warning to the community working on luminescence nanothermometry, since they reveal that the possible sources of bias in complex biological environments, rich in molecules and ions, are more numerous than previously expected.

Spotlight on Luminescence Thermometry: Basics, Challenges, and Cutting-Edge Applications

Luminescence (nano)thermometry is a remote sensing technique that relies on the temperature dependency of the luminescence features (e.g., bandshape, peak energy or intensity, and excited state lifetimes and risetimes) of a phosphor to measure temperature. This technique provides precise thermal readouts with superior spatial resolution in short acquisition times. Although luminescence thermometry is just starting to become a more mature subject, it exhibits enormous potential in several areas, e.g., optoelectronics, photonics, micro- and nanofluidics, and nanomedicine. This work reviews the latest trends in the field, including the establishment of a comprehensive theoretical background and standardized practices. The reliability, repeatability, and reproducibility of the technique are also discussed, along with the use of multiparametric analysis and artificial-intelligence algorithms to enhance thermal readouts. In addition, examples are provided to underscore the challenges that luminescence thermometry faces, alongside the need for a continuous search and design of new materials, experimental techniques, and analysis procedures to improve the competitiveness, accessibility, and popularity of the technology.

3D Optical Coherence Thermometry Using Polymeric Nanogels

In nanothermometry, the use of nanoparticles as thermal probes enables remote and minimally invasive sensing. In the biomedical context, nanothermometry has emerged as a powerful tool where traditional approaches, like infrared thermal sensing and contact thermometers, fall short. Despite the strides of this technology in preclinical settings, nanothermometry is not mature enough to be translated to the bedside. This is due to two major hurdles: the inability to perform 3D thermal imaging and the requirement for tools that are readily available in the clinics. This work simultaneously overcomes both limitations by proposing the technology of optical coherence thermometry (OCTh). This is achieved by combining thermoresponsive polymeric nanogels and optical coherence tomography (OCT)-a 3D imaging technology routinely used in clinical practice. The volume phase transition of the thermoresponsive nanogels causes marked changes in their refractive index, making them temperature-sensitive OCT contrast agents. The ability of OCTh to provide 3D thermal images is demonstrated in tissue phantoms subjected to photothermal processes, and its reliability is corroborated by comparing experimental results with numerical simulations. The results included in this work set credible foundations for the implementation of nanothermometry in the form of OCTh in clinical practice.

Exploring the Origin of the Thermal Sensitivity of Near-Infrared-II Emitting Rare Earth Nanoparticles

Rare-earth doped nanoparticles (RENPs) are attracting increasing interest in materials science due to their optical, magnetic, and chemical properties. RENPs can emit and absorb radiation in the second biological window (NIR-II, 1000-1400 nm) making them ideal optical probes for photoluminescence (PL) in vivo imaging. Their narrow emission bands and long PL lifetimes enable autofluorescence-free multiplexed imaging. Furthermore, the strong temperature dependence of the PL properties of some of these RENPs makes remote thermal imaging possible. This is the case of neodymium and ytterbium co-doped NPs that have been used as thermal reporters for in vivo diagnosis of, for instance, inflammatory processes. However, the lack of knowledge about how the chemical composition and architecture of these NPs influence their thermal sensitivity impedes further optimization. To shed light on this, we have systematically studied their emission intensity, PL decay time curves, absolute PL quantum yield, and thermal sensitivity as a function of the core chemical composition and size, active-shell, and outer-inert-shell thicknesses. The results revealed the crucial contribution of each of these factors in optimizing the NP thermal sensitivity. An optimal active shell thickness of around 2 nm and an outer inert shell of 3.5 nm maximize the PL lifetime and the thermal response of the NPs due to the competition between the temperature-dependent back energy transfer, the surface quenching effects, and the confinement of active ions in a thin layer. These findings pave the way for a rational design of RENPs with optimal thermal sensitivity.

Optomagnetic nanofluids for controlled brain hyperthermia: a critical study

Optomagnetic nanofluids (OMNFs) are colloidal dispersions of nanoparticles (NPs) with combined magnetic and optical properties. They are especially appealing in biomedicine since they can be used as minimally invasive platforms for controlled hyperthermia treatment of otherwise difficultly accessible tumors such as intracranial ones. On the one hand, magnetic NPs act as heating mediators when subjected to alternating magnetic fields or light irradiation. On the other hand, suitably tailored luminescent NPs can provide a precise and remote thermal readout in real time. The combination of heating and thermometric properties allows, in principle, to precisely monitor the increase in the temperature of brain tumors up to the therapeutic level, without causing undesired collateral damage. In this work we demonstrate that this view is an oversimplification since it ignores the presence of relevant interactions between magnetic (γ-Fe₂O₃ nanoflowers) and luminescent nanoparticles (Ag₂S NPs) that result in a detrimental alteration of their physicochemical properties. The magnitude of such interactions depends on the interparticle distance and on the surface properties of nanoparticles. Experiments performed in mouse brains (phantoms and ex vivo) revealed that OMNFs cannot induce relevant heating under alternating magnetic fields and fail to provide reliable temperature reading. In contrast, we demonstrate that the use of luminescent nanofluids (containing only Ag₂S NPs acting as both photothermal agents and nanothermometers) stands out as a better alternative for thermally monitored hyperthermia treatment of brain tumors in small animal models.

Thermoresponsive Polymeric Nanolenses Magnify the Thermal Sensitivity of Single Upconverting Nanoparticles

Lanthanide-based upconverting nanoparticles (UCNPs) are trustworthy workhorses in luminescent nanothermometry. The use of UCNPs-based nanothermometers has enabled the determination of the thermal properties of cell membranes and monitoring of in vivo thermal therapies in real time. However, UCNPs boast low thermal sensitivity and brightness, which, along with the difficulty in controlling individual UCNP remotely, make them less than ideal nanothermometers at the single-particle level. In this work, it is shown how these problems can be elegantly solved using a thermoresponsive polymeric coating. Upon decorating the surface of NaYF₄ :Er³⁺ ,Yb³⁺ UCNPs with poly(N-isopropylacrylamide) (PNIPAM), a >10-fold enhancement in optical forces is observed, allowing stable trapping and manipulation of a single UCNP in the physiological temperature range (20-45 °C). This optical force improvement is accompanied by a significant enhancement of the thermal sensitivity- a maximum value of 8% °C⁺¹ at 32 °C induced by the collapse of PNIPAM. Numerical simulations reveal that the enhancement in thermal sensitivity mainly stems from the high-refractive-index polymeric coating that behaves as a nanolens of high numerical aperture. The results in this work demonstrate how UCNP nanothermometers can be further improved by an adequate surface decoration and open a new avenue toward highly sensitive single-particle nanothermometry.

Less is more: dimensionality reduction as a general strategy for more precise luminescence thermometry

Thermal resolution (also referred to as temperature uncertainty) establishes the minimum discernible temperature change sensed by luminescent thermometers and is a key figure of merit to rank them. Much has been done to minimize its value via probe optimization and correction of readout artifacts, but little effort was put into a better exploitation of calibration datasets. In this context, this work aims at providing a new perspective on the definition of luminescence-based thermometric parameters using dimensionality reduction techniques that emerged in the last years. The application of linear (Principal Component Analysis) and non-linear (t-distributed Stochastic Neighbor Embedding) transformations to the calibration datasets obtained from rare-earth nanoparticles and semiconductor nanocrystals resulted in an improvement in thermal resolution compared to the more classical intensity-based and ratiometric approaches. This, in turn, enabled precise monitoring of temperature changes smaller than 0.1 °C. The methods here presented allow choosing superior thermometric parameters compared to the more classical ones, pushing the performance of luminescent thermometers close to the experimentally achievable limits.

Quantitative Comparison of the Light-to-Heat Conversion Efficiency in Nanomaterials Suitable for Photothermal Therapy

Functional colloidal nanoparticles capable of converting between various energy types are finding an increasing number of applications. One of the relevant examples concerns light-to-heat-converting colloidal nanoparticles that may be useful for localized photothermal therapy of cancers. Unfortunately, quantitative comparison and ranking of nanoheaters are not straightforward as materials of different compositions and structures have different photophysical and chemical properties and may interact differently with the biological environment. In terms of photophysical properties, the most relevant information to rank these nanoheaters is the light-to-heat conversion efficiency, which, along with information on the absorption capacity of the material, can be used to directly compare materials. In this work, we evaluate the light-to-heat conversion properties of 17 different nanoheaters belonging to different groups (plasmonic, semiconductor, lanthanide-doped nanocrystals, carbon nanocrystals, and metal oxides). We conclude that the light-to-heat conversion efficiency alone is not meaningful enough as many materials have similar conversion efficiencies─in the range of 80-99%─while they significantly differ in their extinction coefficient. We therefore constructed their qualitative ranking based on the external conversion efficiency, which takes into account the conventionally defined light-to-heat conversion efficiency and its absorption capacity. This ranking demonstrated the differences between the samples more meaningfully. Among the studied systems, the top-ranking materials were black porous silicon and CuS nanocrystals. These results allow us to select the most favorable materials for photo-based theranostics and set a new standard in the characterization of nanoheaters.

Luminescence Thermometry for Brain Activity Monitoring: A Perspective

Minimally invasive monitoring of brain activity is essential not only to gain understanding on the working principles of the brain, but also for the development of new diagnostic tools. In this perspective we describe how brain thermometry could be an alternative to conventional methods (e.g., magnetic resonance or nuclear medicine) for the acquisition of thermal images of the brain with enough spatial and temperature resolution to track brain activity in minimally perturbed animals. We focus on the latest advances in transcranial luminescence thermometry introducing a critical discussion on its advantages and shortcomings. We also anticipate the main challenges that the application of luminescent nanoparticles for brain thermometry will face in next years. With this work we aim to promote the development of near infrared luminescence for brain activity monitoring, which could also benefit other research areas dealing with the brain and its illnesses.

P372 PATIENTS WITH MINOR NON–DISABLING STROKE (MINDS): RESULTS OF A STRUCTURED CARDIOVASCULAR REHABILITATION PROGRAM

Background

Ischemic cerebral and cardiac events are the leading causes of mortality and morbidity in Minor non–Disabling Stroke (MiNDS) patients. Control of cardiovascular risk factors, including physical activity levels, is a key strategy in secondary prevention of MiNDS. However, there is a gap between recommendations and real achieved physical activity levels in these patients. Clinical benefits obtained with cardiovascular rehabilitation in cardiac ischemic patients could be obtained with similar programs also in patients with MiNDS, given the common pathophysiological substrate of these two diseases Purpose To evaluate safety, effectiveness and feasibility of a cardiovascular rehabilitation program based on structured physical exercise (SPE) in patients with MiNDS

Methods

39 MiNDS patients (26 males, mean age 66 years) underwent an accurate medical screening process, body composition evaluation, cardiopulmonary exercise test (CPET) and muscular strength assessment, before and after a 12–sessions in–hospital SPE program, and after 6– and 12–months follow–up during which they could continue their training schedule on their own Results After in–hospital rehabilitation program, a significant improvement in CPET parameters, body composition and muscular strength was observed. These modifications persisted in the 32 patients who continued 6– and 12– months follow–up training, while regressed in the 7 patients who stopped training

Conclusions - Results

of the present study show that a SPE–based cardiovascular rehabilitation program provides clinical benefit in patients with MiNDS

P368 PHYSICAL AND PSYCHOLOGICAL RECONDITIONING IN LONG COVID SYNDROME: RESULTS OF AN OUT–OF–HOSPITAL EXERCISED–BASED CARDIOVASCULAR REHABILITATION PROGRAM

Background

Long Covid Syndrome (LCS) is used to describe signs and symptoms that continue or develop after acute COVID–19 infection. Natural history and treatments of this syndrome are still poorly understood, even if evidence suggests the potential role of physical rehabilitation in improving symptoms in these subjects.

Aim

The aim of the present study was to evaluate safety, effectiveness and feasibility of a multidisciplinary, out–of–hospital, exercise–based cardiac rehabilitation (EBCR) program, of two months duration, in improving symptoms and physical and psychological parameters in patients with LCS Methods Thirty consecutive patients with LCS (18 males, mean age 58 years) underwent an accurate medical screening process including anthropometric and muscular strength evaluation, cardiopulmonary exercise test (CPET), quality of life (QoL) and psychological appraisal before and after an EBCR program.

Results

At baseline, all LCS patients were strongly symptomatic and showed severe impairments in physical performance, QoL and psychological parameters. No adverse effects and dropouts were observed during the exercise training sessions. After the EBCR program, COVID–19 residual symptoms significantly decreased and significant improvements in upper and lower limb muscular strength, CPET parameters, perceived physical and mental health, depression and anxiety were observed.

Conclusions

The present study confirms the severe physical and psychological impairment of patients with LCS and suggests that a multidisciplinary EBCR program could promote their physical and psychological recovery

Patients with Minor Non-Disabling Stroke (MiNDS): results of a structured cardiovascular rehabilitation program

Funding Acknowledgements

Type of funding sources: None.

Background

Ischemic cerebral and cardiac events are the leading causes of mortality and morbidity in Minor non-Disabling Stroke (MiNDS) patients. Control of cardiovascular risk factors, including physical activity levels, is a key strategy in secondary prevention of MiNDS. However, there is a gap between recommendations and real achieved physical activity levels in these patients. Clinical benefits obtained with cardiovascular rehabilitation in cardiac ischemic patients could be obtained with similar programs also in patients with MiNDS, given the common pathophysiological substrate of these two diseases.

Purpose

To evaluate safety, effectiveness and feasibility of a cardiovascular rehabilitation program based on structured physical exercise (SPE) in patients with MiNDS.

Methods

39 MiNDS patients (26 males, mean age 66 years) underwent an accurate medical screening process, body composition evaluation, cardiopulmonary exercise test (CPET) and muscular strength assessment, before and after a 12-sessions in-hospital SPE program, and after 6- and 12-months follow-up during which they could continue their training schedule on their own.

Results

After in-hospital rehabilitation program, a significant improvement in CPET parameters, body composition and muscular strength was observed. These modifications persisted in the 32 patients who continued 6- and 12- months follow-up training, while regressed in the 7 patients who stopped training.

Conclusions

Results of the present study show that a SPE-based cardiovascular rehabilitation program provides clinical benefit in patients with MiNDS.

Physical and psychological reconditioning in long covid syndrome patients: results of a structured physical exercise program

Funding Acknowledgements

Type of funding sources: None.

Background

Long Covid Syndrome (LCS) is used to describe signs and symptoms that continue or develop after acute COVID-19 infection. Natural history and treatments of this syndrome is still poorly understood. In literature there is currently a lack of data on the real effectiveness of a multidisciplinary rehabilitation program based on structured physical exercise (SPE) in these patients.

Purpose

To evaluate safety, effectiveness and feasibility of a structured individualized rehabilitation program in improving physical and psychological parameters in patients with LCS.

Methods

Twenty-eight patients with LCS (19 males, mean age 57 years) underwent an accurate medical screening process, body composition evaluation, cardiopulmonary exercise test (CPET), muscular strength assessment, quality of life (QoL), psychological assessment and counselling, before and after a 12-sessions SPE program.

Results

At baseline, all LCS patients showed severe impairments in physical performance, QoL and psychological parameters. No adverse effects and dropouts were observed during training session. After the rehabilitation program, significant improvement in CPET parameters, upper and lower limb muscular strength, perceived physical and mental health, body composition, depression and anxiety and Covid residual symptoms was observed.

Conclusions

The present study confirms severe impairment of patients with LCS and suggest that a multidisciplinary rehabilitation program based on SPE could promote their physical and psychological recovery.

New opportunities for light-based tumor treatment with an "iron fist"

The efficacy of photodynamic treatments of tumors can be significantly improved by using a new generation of nanoparticles that take advantage of the unique properties of the tumor microenvironment.

Bismuth Selenide Nanostructured Clusters as Optical Coherence Tomography Contrast Agents: Beyond Gold-Based Particles

Optical coherence tomography (OCT) is an imaging technique currently used in clinical practice to obtain optical biopsies of different biological tissues in a minimally invasive way. Among the contrast agents proposed to increase the efficacy of this imaging method, gold nanoshells (GNSs) are the best performing ones. However, their preparation is generally time-consuming, and they are intrinsically costly to produce. Herein, we propose a more affordable alternative to these contrast agents: Bi₂Se₃ nanostructured clusters with a desert rose-like morphology prepared via a microwave-assisted method. The structures are prepared in a matter of minutes, feature strong near-infrared extinction properties, and are biocompatible. They also boast a photon-to-heat conversion efficiency of close to 50%, making them good candidates as photothermal therapy agents. In vitro studies evidence the prowess of Bi₂Se₃ clusters as OCT contrast agents and prove that their performance is comparable to that of GNSs.

Reliable and Remote Monitoring of Absolute Temperature during Liver Inflammation via Luminescence-Lifetime-Based Nanothermometry

Temperature of tissues and organs is one of the first parameters affected by physiological and pathological processes, such as metabolic activity, acute trauma, or infection-induced inflammation. Therefore, the onset and development of these processes can be detected by monitoring deviations from basal temperature. To accomplish this, minimally invasive, reliable, and accurate measurement of the absolute temperature of internal organs is required. Luminescence nanothermometry is the ideal technology for meeting these requirements. Although this technique has lately undergone remarkable developments, its reliability is being questioned due to spectral distortions caused by biological tissues. In this work, how the use of bright Ag₂ S nanoparticles featuring temperature-dependent fluorescence lifetime enables reliable and accurate measurement of the absolute temperature of the liver in mice subjected to lipopolysaccharide-induced inflammation is demonstrated. Beyond the remarkable thermal sensitivity (≈ 3% °C^-1 around 37 °C) and thermal resolution obtained (smaller than 0.3 °C), the results included in this work set a blueprint for the development of new diagnostic procedures based on the use of intracorporeal temperature as a physiological indicator.

Near infrared bioimaging and biosensing with semiconductor and rare-earth nanoparticles: recent developments in multifunctional nanomaterials

Research in novel materials has been extremely active over the past few decades, wherein a major area of interest has been nanoparticles with special optical properties. These structures can overcome some of the intrinsic limitations of contrast agents routinely used in medical practice, while offering additional functionalities. Materials that absorb or scatter near infrared light, to which biological tissues are partially transparent, have attracted significant attention and demonstrated their potential in preclinical research. In this review, we provide an at-a-glance overview of the most recent developments in near infrared nanoparticles that could have far-reaching applications in the life sciences. We focus on materials that offer additional functionalities besides diagnosis based on optical contrast: multiple imaging modalities (multimodal imaging), sensing of physical and chemical cues (multivariate diagnosis), or therapeutic activity (theranostics). Besides presenting relevant case studies for each class of optically active materials, we discuss their design and safety considerations, detailing the potential hurdles that may complicate their clinical translation. While multifunctional nanomaterials have shown promise in preclinical research, the field is still in its infancy; there is plenty of room to maximize its impact in preclinical studies as well as to deliver it to the clinics.

Spectral Shape Recovery and Analysis Via Data-driven Connections

We introduce a novel learning-based method to recover shapes from their Laplacian spectra, based on establishing and exploring connections in a learned latent space. The core of our approach consists in a cycle-consistent module that maps between a learned latent space and sequences of eigenvalues. This module provides an efficient and effective link between the shape geometry, encoded in a latent vector, and its Laplacian spectrum. Our proposed data-driven approach replaces the need for ad-hoc regularizers required by prior methods, while providing more accurate results at a fraction of the computational cost. Moreover, these latent space connections enable novel applications for both analyzing and controlling the spectral properties of deformable shapes, especially in the context of a shape collection. Our learning model and the associated analysis apply without modifications across different dimensions (2D and 3D shapes alike), representations (meshes, contours and point clouds), nature of the latent space (generated by an auto-encoder or a parametric model), as well as across different shape classes, and admits arbitrary resolution of the input spectrum without affecting complexity. The increased flexibility allows us to address notoriously difficult tasks in 3D vision and geometry processing within a unified framework, including shape generation from spectrum, latent space exploration and analysis, mesh super-resolution, shape exploration, style transfer, spectrum estimation for point clouds, segmentation transfer and non-rigid shape matching.

In Vivo Near-Infrared Imaging Using Ternary Selenide Semiconductor Nanoparticles with an Uncommon Crystal Structure

The implementation of in vivo fluorescence imaging as a reliable diagnostic imaging modality at the clinical level is still far from reality. Plenty of work remains ahead to provide medical practitioners with solid proof of the potential advantages of this imaging technique. To do so, one of the key objectives is to better the optical performance of dedicated contrast agents, thus improving the resolution and penetration depth achievable. This direction is followed here and the use of a novel AgInSe₂ nanoparticle-based contrast agent (nanocapsule) is reported for fluorescence imaging. The use of an Ag₂ Se seeds-mediated synthesis method allows stabilizing an uncommon orthorhombic crystal structure, which endows the material with emission in the second biological window (1000-1400 nm), where deeper penetration in tissues is achieved. The nanocapsules, obtained via phospholipid-assisted encapsulation of the AgInSe₂ nanoparticles, comply with the mandatory requisites for an imaging contrast agent-colloidal stability and negligible toxicity-and show superior brightness compared with widely used Ag₂ S nanoparticles. Imaging experiments point to the great potential of the novel AgInSe₂ -based nanocapsules for high-resolution, whole-body in vivo imaging. Their extended permanence time within blood vessels make them especially suitable for prolonged imaging of the cardiovascular system.

Automatic classification of autism spectrum disorder in children using cortical thickness and support vector machine

OBJECTIVE

Autism spectrum disorder (ASD) is a neurodevelopmental condition with a heterogeneous phenotype. The role of biomarkers in ASD diagnosis has been highlighted; cortical thickness has proved to be involved in the etiopathogenesis of ASD core symptoms. We apply support vector machine, a supervised machine learning method, in order to identify specific cortical thickness alterations in ASD subjects.

METHODS

A sample of 76 subjects (9.5 ± 3.4 years old) has been selected, 40 diagnosed with ASD and 36 typically developed subjects. All children underwent a magnetic resonance imaging (MRI) examination; T1-MPRAGE sequences were analyzed to extract features for the characterization and parcellation of regions of interests (ROI); average cortical thickness (CT) has been measured for each ROI. For the classification process, the extracted features were used as input for a classifier to identify ASD subjects through a "learning by example" procedure; the features with best performance was then selected by "greedy forward-feature selection." Finally, this model underwent a leave-one-out cross-validation approach.

RESULTS

From the training set of 68 ROIs, five ROIs reached accuracies of over 70%. After this phase, we used a recursive feature selection process in order to identify the eight features with the best accuracy (84.2%). CT resulted higher in ASD compared to controls in all the ROIs identified at the end of the process.

CONCLUSION

We found increased CT in various brain regions in ASD subjects, confirming their role in the pathogenesis of this condition. Considering the brain development curve during ages, these changes in CT may normalize during development. Further validation on a larger sample is required.

Infrared-Emitting Multimodal Nanostructures for Controlled In Vivo Magnetic Hyperthermia

Deliberate and local increase of the temperature within solid tumors represents an effective therapeutic approach. Thermal therapies embrace this concept leveraging the capability of some species to convert the absorbed energy into heat. To that end, magnetic hyperthermia (MHT) uses magnetic nanoparticles (MNPs) that can effectively dissipate the energy absorbed under alternating magnetic fields. However, MNPs fail to provide real-time thermal feedback with the risk of unwanted overheating and impeding on-the-fly adjustment of the therapeutic parameters. Localization of MNPs within a tissue in an accurate, rapid, and cost-effective way represents another challenge for increasing the efficacy of MHT. In this work, MNPs are combined with state-of-the-art infrared luminescent nanothermometers (LNTh; Ag₂ S nanoparticles) in a nanocapsule that simultaneously overcomes these limitations. The novel optomagnetic nanocapsule acts as multimodal contrast agents for different imaging techniques (magnetic resonance, photoacoustic and near-infrared fluorescence imaging, optical and X-ray computed tomography). Most crucially, these nanocapsules provide accurate (0.2 °C resolution) and real-time subcutaneous thermal feedback during in vivo MHT, also enabling the attainment of thermal maps of the area of interest. These findings are a milestone on the road toward controlled magnetothermal therapies with minimal side effects.

Switching to the brighter lane: pathways to boost the absorption of lanthanide-doped nanoparticles

Lanthanide-doped nanoparticles (LNPs) are speedily colonizing several research fields, such as biological (multimodal) imaging, photodynamic therapy, volumetric encoding displays, and photovoltaics. Yet, the electronic transitions of lanthanide ions obey the Laporte rule, which dramatically hampers their light absorption capabilities. As a result, the brightness of these species is severely restricted. This intrinsic poor absorption capability is the fundamental obstacle for untapping the full potential of LNPs in several of the aforementioned fields. Among others, three of the most promising physicochemical approaches that have arisen during last two decades to face the challenges of increasing LNP absorption are plasmonic enhancement, organic-dye sensitization, and coupling with semiconductors. The fundamental basis, remarkable highlights, and comparative achievements of each of these pathways for absorption enhancement are critically discussed in this minireview, which also includes a detailed discussion of the exciting perspectives ahead.

Quo Vadis, Nanoparticle-Enabled In Vivo Fluorescence Imaging?

The exciting advancements that we are currently witnessing in terms of novel materials and synthesis approaches are leading to the development of colloidal nanoparticles (NPs) with increasingly greater tunable properties. We have now reached a point where it is possible to synthesize colloidal NPs with functionalities tailored to specific societal demands. The impact of this new wave of colloidal NPs has been especially important in the field of biomedicine. In that vein, luminescent NPs with improved brightness and near-infrared working capabilities have turned out to be optimal optical probes that are capable of fast and high-resolution in vivo imaging. However, luminescent NPs have thus far only reached a limited portion of their potential. Although we believe that the best is yet to come, the future might not be as bright as some of us think (and have hoped!). In particular, translation of NP-based fluorescence imaging from preclinical studies to clinics is not straightforward. In this Perspective, we provide a critical assessment and highlight promising research avenues based on the latest advances in the fields of luminescent NPs and imaging technologies. The disillusioned outlook we proffer herein might sound pessimistic at first, but we consider it necessary to avoid pursuing "pipe dreams" and redirect the efforts toward achievable-yet ambitious-goals.

Asymmetric Ring Opening in a Tetrazine-Based Ligand Affords a Tetranuclear Opto-Magnetic Ytterbium Complex

We report the formation of a tetranuclear lanthanide cluster, [Yb₄ (bpzch)₂ (fod)₁₀ ] (1), which occurs from a serendipitous ring opening of the functionalised tetrazine bridging ligand, bpztz (3,6-dipyrazin-2-yl-1,2,4,5-tetrazine) upon reacting with Yb(fod)₃ (fod^- =6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octandionate). Compound 1 was structurally elucidated via single-crystal X-ray crystallography and subsequently magnetically and spectroscopically characterised to analyse its magnetisation dynamics and its luminescence behaviour. Computational studies validate the observed M_J energy levels attained by spectroscopy and provides a clearer picture of the slow relaxation of the magnetisation dynamics and relaxation pathways. These studies demonstrate that 1 acts as a single-molecule magnet (SMM) under an applied magnetic field in which the relaxation occurs via a combination of Raman, direct, and quantum tunnelling processes, a behaviour further rationalised analysing the luminescent properties. This marks the first lanthanide-containing molecule that forms by means of an asymmetric tetrazine decomposition.

Double check discharge planning to improve the results of a heart failure programme

Background

Reduction of readmissions in heart failure (HF) patients is a main goal of HF programmes. Establishing a discharge planning for the patient and coordinating it with primary care teams are key aspects for their success.

Purpose

Evaluate whether a double check discharge planning based on adding face-to-face joint weekly sessions with primary care managers to the conventional electronic communication of care plan reduces 6-month readmission and 6-month mortality.

Methods

We evaluated all patients discharged from hospital with HF as primary diagnosis between September 2017 and January 2019. We compared outcomes between patients discharged during Period #1 (single check; September 2017 - April 2018) and those discharged during Period #2 (double check; May 2018 - January 2019).

Primary endpoint was the combined endpoint of all-cause death or all-cause hospitalization 6 months after discharge from the index hospitalization.

Results

The study enrolled 317 patients: 182 in Period #1 and 135 in Period #2.

Mean age was 76±9 years. There was a higher proportion of patients with diabetes and COPD in Period #1, with no differences in other baseline characteristics.

The combined endpoint of all cause-death and all-cause hospitalization at 6 months was significantly reduced in patients in the double check discharge planning group (27% vs. 16%, p 0.021).

Conclusions

In a HF programme, the addition of a double check discharge planning based on having joint weekly sessions with primary care managers on top of the conventional electronic communication of care plan reduces 6-month readmission and 6-month mortality.

Funding Acknowledgement

Type of funding source: Public hospital(s). Main funding source(s): Hospital Universitari de Bellvitge

Effectiveness of nurse-led hospital-based heart failure programmes in octagenarians and nonagenarians: is age important?

Background

Efficacy of HF programmes in oldest old (octogenarians and nonagenarians) has not been fully explored.

Methods

We conducted a natural experiment evaluating all patients after hospitalization for heart failure as primary diagnosis between January 2017 and January 2019. We compared outcomes between patients discharged during Period #1, before the implementation of the program with patients discharged during Period #2, after the implementation of the 7-step bundle of interventions. We explored the interaction between age group (&lt;80 vs. ≥80 years old) by the intervention modality (HF programme vs. usual care). Primary end-point was the combined end-point of all-cause death or all-cause hospitalization at 6 months after discharge from the index hospitalization.

Results

The study enroled 440 patients. Mean age of the whole cohort was 75±9 years. In the oldest old subgroup (n=160), mean age was 84±3. No differences were found in baseline characteristics of patients between usual care and HF program. 30-day all-cause readmission was significantly reduced in patients in the HF programme group compared to patients in the usual care group in both age strata. In unadjusted Cox regression analyses in the oldest old group, management of patients in the HF programme was significanty associated with a reduction in the risk of the primary end-point (HR: 0.50; 95% CI [0.29–0.85]; p=0.011).

Conclusions

Management of patients in a nurse-led integrated care-based heart failure programme results in reduction of all-cause death or all-cause hospitalizations in oldest old patients.

Event-free survival cumulative curves.

Funding Acknowledgement

Type of funding source: None

Epidemiology of potassium derangements among chronic cardiovascular, metabolic and renal conditions: a population-based analysis data from more than 375,000 individuals

Introduction

In patients with chronic cardiovascular, metabolic and renal disorders, potassium (K)+ homeostasis is often delicate, especially in the presence of renin-angiotensin-aldosterone system inhibition (RAASI) and/or diuretic therapies. In this context, current clinical practical guidelines for the management of these patients recommend close monitoring of renal function and K+ levels, particularly in the presence of drug titration. Nevertheless, very limited epidemiological data on their importance at a population level is available.

Purpose

The objectives of the present analysis are to estimate the prevalence of potassium (K+) derangements in five key chronic cardiovascular, metabolic and renal conditions at the population level, its use of RAASI medication and describe potassium derangements among RAASI users.

Methods

We used data from more than 375,000 individuals 55 years of age or older included in the population-based healthcare database of a public Institute of Health between 2015 and 2017. The conditions of interest were chronic heart failure (CHF), chronic kidney disease (CKD), diabetes mellitus (DM), ischemic heart disease (IHD), and hypertension (HTN). RAASI medications included angiotensin converting enzyme inhibitors, angiotensin II receptor blockers, mineralocorticoid receptor antagonists (MRAs), and rennin inhibitors. Hyperkalemia was defined as K+ levels &gt;5.0 mEq/L and hypokalemia as K+ &lt;3.5 mEq /L

Results

The prevalence of chronic cardiovascular, metabolic and renal conditions was high, particularly of HTN (48.2–48.9%). The prevalence of hyperkalemia was ranging between 10% and 25% depending of the condition, more frequent in CKD and less frequent in HTN patients. In figure, we display the prevalence of hyperkalemia among individuals with each of the relevant chronic conditions, January 1st, 2016 and January 1st, 2017. Use of at least one RAASI medication was very prevalent in HTN patients (75.2–77.3%). Among RAASI users, the frequency of K+ derangements and mainly of hyperkalemia was very noticeable (12% overall), especially in patients with CKD, CHF, elderly individuals, and users of MRAs. Hypokalemia was less frequent (1%).

Conclusion

The high prevalence of K+ derangements and predominantly hyperkalemia among RAASI users highlights the real-world relevance of K+ derangements and the importance of close monitoring and management of K+ levels in routine clinical practice. This is likely to benefit a large number of patients, particularly those at higher risk.

Figure 1. Prevalence of hyperkalemia

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Josep Comin-Colet and Miguel Cainzos-Achirica have participated in other research projects funded by unrestricted grants from Vifor Pharma

Association between self-care and prognosis in 1123 patients with chronic heart failure

Background

Self-care is a crucial factor in the education of patients with heart failure (HF) and directly impacts in the progression of the disease. However, little is published about its major clinical implications as admission or mortality in patients with HF.

Aims and methods

The aim of the study was to analyze time to admission due to acute heart failure and mortality associated with poor self-care in patients with chronic HF.

We prospectively recruited consecutive patients with stable chronic HF referred to a nurse-led HF programme. Selfcare was evaluated at baseline with the 9 item European Heart Failure Self-Care Behavior Scale. Scores were standardized and reversed from 0 (worst selfcare) to 100 (better self care). For the purpose of this study we analyzed the associations of worse self-care (defined as scores below the lower tertile of the scale) with demographic, disease-related (clinical) and psychosocial factors in all patients at baseline.

Results

We included 1123 patients, mean age 72±11, 639 (60%) were male, mean LVEF 45±17 and 454 (40,4%) were in NYHA class III or IV. Mean score of the 9-item ESCBE was 69±28. Score below 55 (lower tertile) defined impaired selfcare behaviour.

Those patients with worse self-care had more ischaemic heart disease, more COPD, and they achieved less distance in the 6 minute walking test. Regarding psychosocial items patients in lower tertile of self-care needed a caregiver more frequently, they present more cognitive impairment, depressive symptoms and worse score in terms of health self-perception.

Multivariate Cox Models showed that a score below 55 points in 9-item ESCBE was independently associated with higher readmission due to acute heart failure [HR 1.26 (1.02–1.57), p value=0.034] and with mortality [HR 1.24 CI95% (1.02–1.50), p value=0.028]

Conclusion

Poor self-care measured with the modified 9-item ESCBE was associated with higher risk of admission due to acute decompensation and higher risk of mortality in patients with chronic heart failure.

These results highlight the importance of assessing self-care and provide measures to improve them.

Funding Acknowledgement

Type of funding source: Public hospital(s). Main funding source(s): Hospital Univesitario de Bellvitge

A population-based analysis in 375,233 cases of heart failure stages A, B and C. Real world epidemiology of prevalence and temporal trends in South-European populations

Background

Prevalence of congestive heart failure (CHF) and predisposing conditions has described previously. Most of these studies evaluated centre-European or north-American populations. However, the prevalence and evolutionary changes of Heart Failure stages A, B and C has not been fully elucidated in Mediterranean cohorts.

Purpose

To estimate the prevalence of CHF (HF Stage C) and four additional key chronic cardiovascular, metabolic and renal conditions predisposing to the development of CHF (HF Stages A and B) at a population level in a south-European healthcare area. We analysed the evolutionary changes in the prevalence in these five conditions.

Methods

In a healthcare area of 1,3Millions inhabitants, we extracted health related information of all individuals ≥55 years old. We analysed data of 375,233 individuals included in the population-based healthcare database of a public Institute of Health between 2015 and 2017. The conditions of interest were CHF, chronic kidney disease (CKD), diabetes mellitus (DM), ischemic heart disease (IHD) and hypertension (HTN).

Results

The prevalence of chronic conditions was high, particularly of HTN (48.2–48.9%) and DM individuals (14.6–14.8%). The other conditions were less frequent, with prevalence around 2–4% for IHD, 5–9% for CKD and 2–4% for CHF (Table). However, the less frequent conditions had a striking upward trend with over 1,500 new prevalent cases per year between 2015 and 2017 for CHF (45% relative increase), more than 2,500 new prevalent cases for IHD (67% relative increase) and more than 4,000 new prevalent cases per year for CKD (44% relative increase).

Conclusion

In this south European cohort, there were a high prevalence of HTN and DM as risk factors and a significant trend of increasing prevalence in high cost chronic conditions such as CHF, IHD and CKD.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): The present study was funded by an unrestricted research grant from Vifor Pharma.

Long-term effectiveness of a nurse-led 7-step transitional intervention programme in heart failure

Background

Reduction of 30-day readmission in heart failure (HF) patients is a main goal of health-care systems. Programmes to decrease 30-day readmission have successfully reduced it but have failed to neither maintain benefit afterwards nor decrease mortality. Moreover, in many cases the price of reducing 30-day readmission is a mortality increase.

Purpose

Evaluate whether the impact of a fully nurse-led HF programme directed to reduce 30-day readmission and mortality extends to longer periods of time, including 90 days and 180 days after discharge.

Methods

We evaluated all patients discharged from hospital with HF as primary diagnosis between January 2017 and January 2019. We compared outcomes between patients discharged during Period #1 (pre-programme; Jan 2017 - Aug 2017) and those discharged during Period #2 (HF programme; Sept 2017 - Jan 2019).

Primary endpoint was the combined endpoint of all-cause death or all-cause hospitalization 90 days and 180 days after discharge from the index hospitalization.

Results

The study enrolled 440 patients: 123 in Period #1 and 317 in Period #2.

Mean age was 75±9 years. There was a higher proportion of female patients in Period #2 (38.2% vs 26.8%, p=0.025), with no differences in other baseline characteristics.

The combined endpoint of all cause-death and all-cause hospitalization was significantly reduced in patients in the HF programme group, both at 90 days [OR 0.37 (0.22–0.63), p&lt;0.001] and at 180 days [OR 0.27 (CI 0.17–0.43), p&lt;0.001]. Such a decrease was at expense of a reduction in cardiovascular (CV) hospitalization and HF hospitalization.

There were no differences between groups in mortality [OR 0.96 (0.18–5.00), p=0.293].

Conclusions

A fully nurse-led HF programme reduces the combined endpoint of all-cause death and all-cause hospitalization both at 90 days and 180 days after an index discharge for HF.

Such a decrease is driven by a reduction of CV and HF hospitalization, which are maintained over time. There were no differences between groups in mortality.

Funding Acknowledgement

Type of funding source: Public hospital(s). Main funding source(s): Hospital Universitari de Bellvitge

Spectral characterization of LiYbF4 upconverting nanoparticles

In light of the recent developments on Yb³⁺-based upconverting rare-earth nanoparticles (RENPs), we have systematically explored the spectral features of LiYbF₄:RE³⁺/LiYF₄ core/shell RENPs doped with various amounts of Tm³⁺, Er³⁺, or Ho³⁺. Tm³⁺-RENPs displayed photoluminescence from the UV to near-infrared (NIR), and the dominant high-photon-order upconversion emission of these RENPs was tunable by Tm³⁺ doping. Similarly, Er³⁺- and Ho³⁺-RENPs with green and red upconversion showed wide color tuning, depending on the doping amount and excitation power density. From steady-state power plot and photoluminescence decay studies we have observed respective changes in upconversion photon order and average lifetime that attest to a number of cross-relaxation processes occurring at higher RE³⁺ doping concentration. Particularly in the case of Tm³⁺-RENPs, cross-relaxation promotes four- and five-photon order upconversion emission in the UV and blue spectral regions. The quantum yield of high-order upconversion emission was on par with classic Yb³⁺/Tm³⁺-doped systems, yet due to the high number of sensitizer ions in the LiYbF₄ host these RENPs are expected to be brighter and thus better suited for applications such as controlled drug delivery or optogenetics. Overall, LiYbF₄:RE³⁺/LiYF₄ RENPs are promising systems to effectively generate high-order upconversion emissions, owing to excitation energy confinement within the Yb³⁺ network and its efficient funneling to the activator dopants.

A randomized comparison trial of culturally adapted HIV prevention approaches for Native Americans reducing trauma symptoms versus substance misuse: The Healing Seasons protocol

Native Americans (NA) experience interrelated risks of trauma exposure, substance use, and HIV risk behaviors that put them at increased risk for HIV infection. Despite these known risk factors, there are very few published randomized trials testing interventions to reduce trauma-related symptoms and substance misuse among NA.

METHODS

The Healing Seasons study is a randomized comparsion trial of two counseling strategies, Narrative Exposure Therapy (NET) addressing PTSD or Motivational interviewing with cognitive behavioral therapy skills training (MIST) addressing substance misuse as a means to prevent HIV among NA. Using a community-based participatory research approach, we adapted both evidence-based interventions to be specific to the risk contexts and realities of NA and to include psychoeducational and skill-building components that include cultural-specific stories, virtues, and traditional treatment strategies. Participants, 16 years and older, were recruited from a Pacific Northwest tribal community, screened over the phone, enrolled in person, and randomized in equal numbers to NET or MIST. We stratified by age (16-29 years and 30 or older) and gender (male or female identified) to ensure balance between treatment arms. The primary outcomes were number of sex partners and frequency of sexual acts (with and without condoms), sex under the influence of substances, frequency of substance use, and PTSD severity.

DISCUSSION

Behavioral interventions for NA are needed to prevent HIV risk behaviors when faced with trauma symptoms and substance misuse. This study will provide evidence to determine feasibility and efficacy of addressing related risk factors as part of counseling-based HIV prevention intervention to reduce sexual risk among this population.

TRIAL REGISTRATION

ClinicalTrials.gov number, NCT03112369, registered April 12, 2017.

Investigation of the concentration- and temperature-dependent motion of colloidal nanoparticles

Although the motion of a single nanoparticle suspended in a fluid can be easily modeled, things get complicated for non-infinitely diluted systems. Coincidentally, these are the systems of interest in relevant fields such as, nanomedicine, microfluidics and miniaturized energy storage devices. Hence, a better understanding of the dynamics of colloidal nanoparticles is utterly needed. Herein, the motion of colloidal suspension of plasmonic nanoparticles (i.e., gold nanoshells) is investigated via laser speckle imaging. The method relies on the analysis of the speckle pattern generated by colloidal suspensions forced to flow at specific velocities. Temperature-dependent measurements corroborated that the dynamics of non-infinitely diluted nanoparticle suspensions are better described through a diffusive model rather than by the equipartition theorem. Under the tested experimental conditions, an average diffusion velocity between 0.37 and 1.57 mm s-1 was found. Most importantly, these values were largely dependent on the nanoparticle concentration. These results are in agreement with previous reports and indicate the existence of long-range interactions between nanoparticles.

Influence of halide ions on the structure and properties of copper indium sulphide quantum dots

In the synthesis of CuInS2 quantum dots (QDs), the halide ions present in the copper salts influence the QD growth and optical properties. X-ray absorption spectroscopy allowed rationalizing the halide incorporation in the lattice and the dependence of electronic properties of the material on the ion's polarizability and interaction with hydrophobic moieties.

Plasmonic Copper Sulfide Nanoparticles Enable Dark Contrast in Optical Coherence Tomography

Optical coherence tomography (OCT) is an imaging technique affording noninvasive optical biopsies. Like for other imaging techniques, the use of dedicated contrast agents helps better discerning biological features of interest during the clinical practice. Although bright OCT contrast agents have been developed, no dark counterpart has been proposed yet. Herein, plasmonic copper sulfide nanoparticles as the first OCT dark contrast agents working in the second optical transparency window are reported. These nanoparticles virtually possess no light scattering capabilities at the OCT working wavelength (≈1300 nm); thus, they exclusively absorb the probing light, which in turn results in dark contrast. The small size of the nanoparticles and the absence of apparent cytotoxicity support the amenability of this system to biomedical applications. Importantly, in the pursuit of systems apt to yield OCT dark contrast, a library of copper sulfide nanoparticles featuring plasmonic resonances spanning the three optical transparency windows is prepared, thus highlighting the versatility and potential of these systems in light-controlled biomedical applications.

Exploring the dual functionality of an ytterbium complex for luminescence thermometry and slow magnetic relaxation

We present a comprehensive investigation of the magnetic and optical properties of an ytterbium complex, which combines two desirable and practical features into a single molecular system. Based upon YbIII ions that promote near-infrared optical activity and a chemical backbone that is ideal for an in-depth understanding of the magnetic behaviour, we have designed a multifunctional opto-magnetic species that operates as a luminescent thermometer and as a single-molecule magnet (SMM). Our magnetic investigations, in conjunction with ab initio calculations, reveal one of the highest energy barriers reported for an YbIII-based complex. Moreover, we correlate this anisotropic barrier with the emission spectrum of the compound, wherein we provide a complete assignment of the energetic profile of the complex. Such studies lay the foundation for the design of exciting multi-faceted materials that are able to retain information at the single-molecule level and possess built-in thermal self-monitoring capabilities.

A Luminescent Thermometer Exhibiting Slow Relaxation of the Magnetization: Toward Self-Monitored Building Blocks for Next-Generation Optomagnetic Devices

The development and integration of Single-Molecule Magnets (SMMs) into molecular electronic devices continue to be an exciting challenge. In such potential devices, heat generation due to the electric current is a critical issue that has to be considered upon device fabrication. To read out accurately the temperature at the submicrometer spatial range, new multifunctional SMMs need to be developed. Herein, we present the first self-calibrated molecular thermometer with SMM properties, which provides an elegant avenue to address these issues. The employment of 2,2'-bipyrimidine and 1,1,1-trifluoroacetylacetonate ligands results in a dinuclear compound, [Dy₂(bpm)(tfaa)₆], which exhibits slow relaxation of the magnetization along with remarkable photoluminescent properties. This combination allows the gaining of fundamental insight in the electronic properties of the compound and investigation of optomagnetic cross-effects (Zeeman effect). Importantly, spectral variations stemming from two distinct thermal-dependent mechanisms taking place at the molecular level are used to perform luminescence thermometry over the 5-398 K temperature range. Overall, these properties make the proposed system a unique molecular luminescent thermometer bearing SMM properties, which preserves its temperature self-monitoring capability even under applied magnetic fields.

Cubic versus hexagonal - effect of host crystallinity on the T1 shortening behaviour of NaGdF4 nanoparticles

Sodium gadolinium fluoride (NaGdF4) nanoparticles are promising candidates as T1 shortening magnetic resonance imaging (MRI) contrast agents due to the paramagnetic properties of the Gd3+ ion. Effects of size and surface modification of these nanoparticles on proton relaxation times have been widely studied. However, to date, there has been no report on how T1 relaxivity (r1) is affected by the different polymorphs in which NaGdF4 crystallizes: cubic (α) and hexagonal (β). Here, a microwave-assisted thermal decomposition method was developed that grants selective access to NaGdF4 nanoparticles of either phase in the same size range, allowing the influence of host crystallinity on r1 to be investigated. It was found that at 3 T cubic NaGdF4 nanoparticles exhibit larger r1 values than their hexagonal analogues. This result was interpreted based on Solomon-Bloembergen-Morgan theory, suggesting that the inner sphere contribution to r1 is more pronounced for cubic NaGdF4 nanoparticles as compared to their hexagonal counterparts. This holds true irrespective of the chosen surface modification, i.e. small citrate groups or longer chain poly(acrylic acid). Key aspects were found to be a polymorph-induced larger hydrodynamic diameter and the higher magnetization possessed by cubic nanoparticles.

Highly Efficient Copper Sulfide-Based Near-Infrared Photothermal Agents: Exploring the Limits of Macroscopic Heat Conversion

Among the foreseeable therapeutic approaches at the cellular level, nanoplatform-driven photothermal therapy is a thriving tool for the selective eradication of malignant tissues with minimal side effects to healthy ones. Hence, chemically versatile, near-infrared absorbing plasmonic nanoparticles are distinctly appealing and most sought after as efficient photothermal agents. In this work, a straightforward method to synthesize monodisperse PEGylated copper sulfide nanoparticles of pure covellite (CuS) phase, featuring strong localized surface plasmonic resonance absorption in the near-infrared and flexible surface chemistry, imparted by monomethyl ether polyethylene glycol molecules, is developed and optimized. These nanoparticles show a remarkable photothermal heat conversion efficiency (HCE) of 71.4%, which is among the highest for CuS systems and rivals that of plasmonic noble metal nanostructures. Moreover, through critical evaluation and mathematical modeling of the material's properties and measurement methodology, it is assessed that the calculated HCE values drastically depend on experimental conditions such as wavelength-dependent solvent absorption properties, sol concentration, and optical path. These findings are of paramount relevance to the photothermal community, since they call for a standardization of the procedure for the evaluation of the HCE of proposed photothermal agents, in order to make the reported values universally and reliably comparable.