Neodymium-Sensitized Nanoconstructs for Near-Infrared Enabled Photomedicine

Stabilizing Dye-Sensitized Upconversion Hybrids by Cyclooctatetraene

Lanthanide-doped upconversion nanoparticles (UCNPs) can convert low-energy near-infrared (NIR) light into high-energy visible light, making them valuable for broad applications. UCNPs often suffer from poor light-harvesting capabilities, which can be significantly improved by incorporating organic dye antennas. However, the dye-sensitized upconversion systems are prone to severe photobleaching in an ambient atmosphere. Here, we present a synergistic approach to mitigate photobleaching by introducing triplet state quencher cyclooctatetraene (COT). COT effectively suppresses the generation of singlet oxygen by quenching the triplet states of the dye and consumes the existing singlet oxygen through oxidant reactions. The inclusion of COT extends the half-life of IR806 by 4.7-times by preventing the oxidation of its poly(methylene) chains. Without significantly affecting emission intensity and dynamics, COT effectively stabilized dye-UCNPs, demonstrating a notable 3.9-fold increase in half-life under continuous laser irradiation. Our findings suggest a new strategy to enhance the photostability of near-infrared dyes and dye-sensitized upconversion nanohybrids.

Development of Broad-Range Microbial Minimal Culture Medium for Lanthanide Studies

Rare Earth Elements (REE), also known as Lanthanides (Ln3+), are a group of 17 elements showing peculiar physical and chemical properties. Unlike technological applications, very little is known about the physiological role and toxicity of Ln3+ on biological systems, in particular on microorganisms (e.g., bacteria), which represent the most abundant domains on our planet. Up to now, very limited studies have been conducted due to Ln3+ precipitation with some anions commonly present in the culture media. Therefore, the development of a minimal medium is essential to allow the study of Ln3+-microbial interactions, limiting considerably the precipitation of insoluble salts. In this regard, a new minimal culture medium capable of solubilizing large amounts of Ln3+ and allowing the growth of different microbial taxa was successfully developed. Assays have shown that the medium is capable of solubilizing Ln3+ up to 100 times more than other common culture media and allowing the growth of 63 bacteria and 5 fungi. The kinetic growth of one yeast and one Gram-positive bacterium has been defined, proving to support superior growth and biomass compared to other commonly used minimal media. Moreover, the sensitivity and uptake/absorption of a Bacillus stratosphericus strain were tested, highlighting its capability to tolerate concentrations up to 10 mM of either Cerium, Gadolinium or Lanthanum and accumulate different quantities of the three.

Portable Near-Infrared to Near-Infrared Platform for Homogeneous Quantification of Biomarkers in Complex Biological Samples

Förster resonance energy transfer (FRET)-based homogeneous immunoassay obviates tedious washing steps and thus is a promising approach for immunoassays. However, a conventional FRET-based homogeneous immunoassay operating in the visible region is not able to overcome the interference of complex biological samples, thus resulting in insufficient detection sensitivity and poor accuracy. Here, we develop a near-infrared (NIR)-to-NIR FRET platform (Ex = 808 nm, Em = 980 nm) that enables background-free high-throughput homogeneous quantification of various biomarkers in complex biological samples. This NIR-to-NIR FRET platform is portable and easy to operate and is mainly composed of a high-performance NIR-to-NIR FRET pair based on lanthanide-doped nanoparticles (LnNPs) and a custom-made microplate reader for readout of NIR luminescence signals. We demonstrate that this NIR-to-NIR FRET platform is versatile and robust, capable of realizing highly sensitive and accurate detection of various critical biomarkers, including small molecules (morphine and 1,25-dihydroxyvitamin D), proteins (human chorionic gonadotropin), and viral particles (adenovirus) in unprocessed complex biological samples (urine, whole blood, and feces) within 5-10 min. We expect this NIR-to-NIR FRET platform to provide low-cost healthcare for populations living in resource-limited areas and be widely used in many other fields, such as food safety and environmental monitoring.

Handheld NIR-to-NIR Platform for on-site evaluating protective neutralizing antibody against SARS-CoV-2 ancestral strain and Omicron variant after vaccination or infection

Lateral flow assays (LFAs) are promising points-of-care tests, playing a vital role in diseases screening, diagnosis and surveillance. However, development of portable, cheap, and smart LFAs platform for sensitive and accurate quantification of disease biomarkers in complex media is challenging. Here, a cheap handheld device was developed to realize on-site detection of disease biomarkers by Nd³⁺/Yb³⁺ co-doped near-infrared (NIR)-to-NIR downconversion nanoparticles (DCNPs) based LFA. Its sensitivity is at least 8-fold higher for detecting NIR light signal from Nd³⁺/Yb³⁺ co-doped nanoparticles than conventional expensive InGaAs camera based detection platform. Additionally, we enhance NIR quantum yield of Nd³⁺/Yb³⁺ co-doped nanoparticles up to 35.5% via simultaneous high dopant of sensitizer ions Nd³⁺ and emitter ions Yb³⁺. Combination of NIR-to-NIR handheld detection device and ultra-bright NIR emitting NaNbF₄:Yb60%@NaLuF₄ nanoparticle probe allows the detection sensitivity of SARS-CoV-2 ancestral strain and Omicron variants specific neutralizing antibodies LFA up to the level of commercial enzyme linked immunosorbent assay kit. Furthermore, by this robust method, enhanced neutralizing antibodies against SARS-CoV-2 ancestral strain and Omicron variants are observed in healthy participants with Ad5-nCoV booster on top of two doses of inactivated vaccine. This NIR-to-NIR handheld platform provides a promising strategy for on-site evaluating protective humoral immunity after SARS-CoV-2 vaccination or infection.

Overcoming Vascular Barriers to Improve the Theranostic Outcomes of Nanomedicines

Nanotheranostics aims to utilize nanomaterials to prevent, diagnose, and treat diseases to improve the quality of patients' lives. Blood vessels are responsible to deliver nutrients and oxygen to the whole body, eliminate waste, and provide access for patrolling immune cells for healthy tissues. Meanwhile, they can also nourish disease tissues, spread disease factors or cells into other healthy tissues, and deliver nanotheranostic agents to cover all the regions of a disease tissue. Thus, blood vessels are the first and the most important barrier for highly efficient nanotheranostics. Here, the structure and function of blood vessels are explored and how these characteristics affect nanotheranostics is discussed. Moreover, new mechanisms and related strategies about overcoming vascular obstacles for improved nanotheranostic outcomes are critically summarized, and their merits and demerits of each strategy are analyzed. Moreover, the present challenges to completely exhibit the potential of overcoming vascular barriers to improve the theranostic outcomes of nanomedicines in life science are also discussed. Finally, the future perspective is further discussed.

Water stable, red emitting, carbon nanoparticles stimulate 3D cell invasion via clathrin-mediated endocytic uptake

Bright fluorescent nanoparticles with excitation and emission towards the red end of the spectrum are highly desirable in the field of bioimaging. We present here a new class of organic carbon-based nanoparticles (CNPs) with a robust quantum yield and fluorescence towards the red region of the spectrum. Using organic substrates such as para-phenylenediamine (PPDA) dispersed in diphenyl ether under reflux conditions, we achieved scalable amounts of CNPs with an average size of 27 nm. These CNPs were readily taken up by different mammalian cells, and we show that they prefer clathrin-mediated endocytosis for their cellular entry route. Not only can these CNPs be specifically taken up by cells, but they also stimulate cellular processes such as cell invasion from 3D spheroid models. This new class of CNPs, which have sizes similar to those of proteinaceous ligands, hold immense potential for their surface functionalization. These could be explored as promising bioimaging agents for biomedical imaging and intracellular drug delivery.

Degradable mesoporous semimetal antimony nanospheres for near-infrared II multimodal theranostics

Metallic and semimetallic mesoporous frameworks are of great importance owing to their unique properties and broad applications. However, semimetallic mesoporous structures cannot be obtained by the traditional template-mediated strategies due to the inevitable hydrolytic reaction of semimetal compounds. Therefore, it is yet challenging to fabricate mesoporous semimetal nanostructures, not even mention controlling their pore sizes. Here we develop a facile and robust selective etching route to synthesize monodispersed mesoporous antimony nanospheres (MSbNSs). The pore sizes of MSbNSs are tunable by carefully controlling the partial oxidation of Sb nuclei and the selective etching of the as-formed Sb₂O₃. MSbNSs show a wide absorption from visible to second near-infrared (NIR-II) region. Moreover, PEGylated MSbNSs are degradable and the degradation mechanism is further explained. The NIR-II photothermal performance of MSbNSs is promising with a high photothermal conversion efficiency of ~44% and intensive NIR-II photoacoustic signal. MSbNSs show potential as multifunctional nanomedicines for NIR-II photoacoustic imaging guided synergistic photothermal/chemo therapy in vivo. Our selective etching process would contribute to the development of various semimetallic mesoporous structures and efficient multimodal nanoplatforms for theranostics.

Gram-scale synthesis of a neodymium chelate as a spectral CT and second near-infrared window imaging agent for visualizing the gastrointestinal tract in vivo

The diagnosis of gastrointestinal (GI) tract diseases is frequently performed in the clinic, so it is crucial to develop high-performance contrast agents for real-time and non-invasive imaging examination of the GI tract. Herein, we show a novel method to synthesize a neodymium (Nd) chelate, Nd-diethylenetriaminepentaacetic acid (Nd-DTPA), on a large scale without byproducts for spectral computed tomography (CT) and second near-infrared window imaging of the GI tract in vivo. The Nd-DTPA was simply generated by heating the mixture of Nd2O3 and DTPA in water at 85 °C for 2 h. This dual-modal imaging agent has the advantages of a simple and green synthesis route, no need of purification process, high yield (86.24%), large-scale production capability (>10 g in lab synthesis), good chemical stability and excellent water solubility (≈2 g mL-1). Moreover, the Nd-DTPA emitted strong near-infrared fluorescence at 1308 nm, and exhibited superior X-ray attenuation ability compared to clinical iohexol. The proposed Nd-DTPA can integrate the complementary merits of dual-modal imaging to realize spatial-temporal and highly sensitive imaging of the GI tract in vivo, and accurate diagnosis of the location of intestinal obstruction and monitor its recovery after surgery. The developed highly efficient method for the gram-scale synthesis of Nd-DTPA and the proposed spectral CT and second near-infrared window dual-modal imaging strategy provide a promising route for accurate visualization of the GI tract in vivo.

Lanthanide doped luminescence nanothermometers in the biological windows: strategies and applications

The development of lanthanide-doped non-contact luminescent nanothermometers with accuracy, efficiency and fast diagnostic tools attributed to their versatility, stability and narrow emission band profiles has spurred the replacement of conventional contact thermal probes. The application of lanthanide-doped materials as temperature nanosensors, excited by ultraviolet, visible or near infrared light, and the generation of emissions lying in the biological window regions, I-BW (650 nm-950 nm), II-BW (1000 nm-1350 nm), III-BW (1400 nm-2000 nm) and IV-BW (centered at 2200 nm), are notably growing due to the advantages they present, including reduced phototoxicity and photobleaching, better image contrast and deeper penetration depths into biological tissues. Here, the different mechanisms used in lanthanide ion-doped nanomaterials to sense temperature in these biological windows for biomedical and other applications are summarized, focusing on factors that affect their thermal sensitivity, and consequently their temperature resolution. Comparing the thermometric performance of these nanomaterials in each biological window, we identified the strategies that allow boosting of their sensing properties.

Antimony Nanopolyhedrons with Tunable Localized Surface Plasmon Resonances for Highly Effective Photoacoustic-Imaging-Guided Synergistic Photothermal/Immunotherapy

Antimony (Sb), a typical group VA semimetal, has rarely been studied both experimentally and theoretically in plasmonic photothermal therapy, possibly due to the lack of effective morphology-controllable methods for the preparation of high-quality Sb nanocrystals. In this study, an effective ligand-guided growth strategy to controllably synthesize Sb nanopolyhedrons (Sb NPHs) with ultrahigh photothermal conversion efficiency (PTCE), good photothermal stability, as well as biocompatibility is presented. Furthermore, the modulation effect of different morphologies on localized surface plasmon resonance (LSPR) of Sb NPHs in experimentation is successfully observed. When the resonance frequency of the Sb NPHs is matched well with the excitation wavelength (808 nm), the PTCE of the Sb NPHs is as high as 62.1%, which is noticeably higher compared to most of the reported photothermal agents. The Sb NPHs also exhibit good photothermal stability. In addition, Sb-NPHs-based multifunctional nanomedicines are further constructed via loading 1-methyl-d-tryptophan on PEGylated Sb NPHs for a highly efficient photoacoustic-imaging-guided synergistic photothermal/immune-therapy of tumors in vivo. This work can stimulate further theoretical and experimental investigations of Sb NPHs and other semimetal nanomaterials regarding their LSPR properties and inspire various potential applications of semimetals in biomedicine and sensors.

Water-soluble green-emitting carbon nanodots with enhanced thermal stability for biological applications

High stability and water solubility of fluorescent nanomaterials are considered key factors to evaluate their feasibility for fundamental applications. Herein, water-soluble and thermally stable, green-emitting carbon nanodots (CNDs) have been synthesized via a facile hydrothermal method with an average size of 1.9 nm. CNDs showed green emission centered at 544 nm with the photo-luminescence quantum yield (PLQY) of up to 10.1% under the excitation of 400 nm. The obtained CNDs demonstrated high resistance towards photo-bleaching and an ionic (KCl) environment. Moreover, the aqueous solution of CNDs exhibited excellent stability under harsh thermal conditions from 10 °C to 80 °C. The as-prepared CNDs showed stable performance at high temperatures, even after keeping them at 80 °C for 30 min. Furthermore, the green emissive CNDs were incubated in T-ca cancer cells for bio-imaging applications. The results indicated that CNDs can served as an effective thermally-stable bio-imaging agent in T-ca cells at the physiological temperature range of 25 °C-45 °C. Green emission and excellent thermal stability make these CNDs promising fluorescent materials for potential applications in the medical field, which requires long-wavelength fluorescence and high-temperature imaging.

Second near-infrared photothermal materials for combinational nanotheranostics

This review summarizes the recent development of second near-infrared photothermal combinational nanotheranostics for cancer, infectious diseases and regenerative medicine.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Near-infrared-II activated inorganic photothermal nanomedicines

The emergence of near-infrared-II (NIR-II) activated photomedicines has extended the penetration depth for noninvasive theranostics, especially for photothermal nanomedicines. The current early development stage for NIR-II activated photomedicines has focused on creating a greater variety of photothermal agents (PTAs) with superior photothermal conversion ability. However, there is no thorough review for NIR-II inorganic PTAs and most comparisons of the photothermal performances of NIR-II inorganic PTAs are made with NIR-I PTAs. This review will first discuss about the key mechanisms of NIR-II absorption and photothermal conversion. Subsequently, this review will summarize recently developed advanced NIR-II inorganic PTAs based on the dominant inorganic elements and provide a comparison of their NIR-II photothermal performances. The nanostructure design, enhancement strategies and potential biomedical applications will be listed and discussed. We hope this review will further inspire active development and study of NIR-II activated inorganic PTAs with good photothermal conversion ability, multifunctionality, biocompatibility or biodegradability, and disease targeting ability.

Recent advances of near infrared inorganic fluorescent probes for biomedical applications

Near infrared (NIR)-excitable and NIR-emitting probes have fuelled advances in biomedical applications owing to their power in enabling deep tissue imaging, offering high image contrast and reducing phototoxicity. There are essentially three NIR biological windows, i.e., 700-950 nm (NIR I), 1000-1350 nm (NIR II) and 1550-1870 nm (NIR III). Recently emerging optical probes that can be excited by an 800 nm laser and emit in the NIR II or III windows, denoted as NIR I-to-NIR II/III, are particularly attractive. That is because the longer wavelengths in the NIR II and NIR III windows offer deeper penetration and higher signal to noise ratio than those in the NIR I window. NIR imaging has indeed become a quickly evolving field and, simultaneously, stimulated the further development of new classes of NIR I-to-NIR II/III inorganic fluorescent probes, which include PbS, Ag₂S-based quantum dots (QDs) and rare earth (RE) doped NPs (RENPs) that possess quite diverse optical properties and follow different emission mechanisms. This review summarizes the recent progress on material merits, synthetic routes, the rational choice of excitation in the NIR I window, NIR II/III emission optimization, and surface modification of aforementioned fluorescent probes. We also introduce the latest notable accomplishments enabled by these probes in fluorescence imaging, lifetime-based multiplexed imaging and photothermal therapy (PTT), together with a critical discussion of forthcoming challenges and perspectives for clinic use.

Remote Control of Neural Stem Cell Fate Using NIR-Responsive Photoswitching Upconversion Nanoparticle Constructs

Light-mediated remote control of stem cell fate, such as proliferation, differentiation, and migration, can bring a significant impact on stem cell biology and regenerative medicine. Current UV/vis-mediated control approaches are limited in terms of nonspecific absorption, poor tissue penetration, and phototoxicity. Upconversion nanoparticle (UCNP)-based near-infrared (NIR)-mediated control systems have gained increasing attention for vast applications with minimal nonspecific absorption, good penetration depth, and minimal phototoxicity from NIR excitations. Specifically, 808 nm NIR-responsive upconversion nanomaterials have shown clear advantages for biomedical applications owing to diminished heating effects and better tissue penetration. Herein, a novel 808 nm NIR-mediated control method for stem cell differentiation has been developed using multishell UCNPs, which are optimized for upconverting 808 nm NIR light to UV emission. The locally generated UV emissions further toggle photoswitching polymer capping ligands to achieve spatiotemporally controlled small-molecule release. More specifically, with 808 nm NIR excitation, stem cell differentiation factors can be released to guide neural stem cell (NSC) differentiation in a highly controlled manner. Given the challenges in stem cell behavior control, the developed 808 nm NIR-responsive UCNP-based approach to control stem cell differentiation can represent a new tool for studying single-molecule roles in stem cell and developmental biology.

Photoactivatable Protherapeutic Nanomedicine for Cancer

Therapeutic systems with site-specific pharmaceutical activation hold great promise to enhance therapeutic efficacy while reducing systemic toxicity in cancer therapy. With operational flexibility, noninvasiveness, and high spatiotemporal resolution, photoactivatable nanomedicines have drawn growing attention. Distinct from traditional controlled release systems relying on the difference of biomarker concentrations between disease and healthy tissues, photoactivatable nanomedicines capitalize on the interaction between nanotransducers and light to either trigger photochemical reactions or generate reactive oxygen species (ROS) or heat effect to remotely induce pharmaceutical actions in living subjects. Herein, the recent advances in the development of photoactivatable protherapeutic nanoagents for oncology are summarized. The design strategies and therapeutic applications of these nanoagents are described. Representative examples of each type are discussed in terms of structure, photoactivation mechanism, and preclinical models. Last, potential challenges and perspectives to further develop photoactivatable protherapeutic nanoagents in cancer nanomedicine are discussed.

Balancing the thickness of sensitizing and inert layers in neodymium-sensitized tetralayer nanoconstructs for optimal ultraviolet upconversion and near-infrared cross-linked hydrogel tissue sealants

Balancing the thickness of sensitizing and inert layers in neodymium-sensitized tetralayer nanoconstructs for optimal ultraviolet upconversion.

Lanthanide nanoparticles with efficient near-infrared-II emission for biological applications

We discuss designing efficient NIR-II-emitting lanthanide NPs and summarize their recent progress in bioimaging, therapy, and biosensing, as well as their limitations and future opportunities.