Phospholipid-polyethylene Glycol Research Articles

Single Molecule Imaging of Sp3 Functionalized Ultrashort Carbon Nanotubes for Deep Brain Tissue Investigation

Near-infrared (NIR) fluorescence microscopy has attracted significant attention for in vivo deep tissue imaging due to the combination of low light scattering and absorption by the tissues, resulting in good light penetration depth, especially in the NIR-II window (~1000–1350 nm). In this context, NIR photoluminescence (PL) (λem ~ 900–1400 nm) of single-walled carbon nanotubes overlapping with the so-called “tissue transparency window” laid the foundation for their use in bioimaging and sensing applications. Interestingly, although ultrashort carbon nanotubes (usCNTs) had long been sought for their advantages of mimicking bio-molecular dimensions, it is only when sp3 defects introduced bright fluorescent usCNTs could be generated [1]. In this work, we demonstrate the efficient preparation of bright fluorescent usCNTs specifically designed for biological applications, and we show how to create bright usCNTs wrapped by a biocompatible encapsulating agent (phospholipid-polyethylene glycol, PL-PEG). More precisely, we adapted a synthesis route where the sp3 functionalization is followed by chemical cutting [2]. We will present their full characterization and demonstrate their performance for deep tissue imaging in neuroscience. More precisely, our results performed on live brain tissue allow us to analyze their length specific behaviors in different compartments of mouse brains in comparison to the long sp3 functionalized CNTs [3].

Selective photothermal and photodynamic capabilities of conjugated polymer nanoparticles

We found out that the conjugated polymers with different molecular weights and fullerene addition selectively controlled the photothermal and photodynamic effects of conjugated polymer nanoparticles (CPNs). It turned out that the use of high molecular weight (MW) conjugated polymer increase near infrared absorption, resulting in more photothermal effect than photodynamic effect. The highest photothermal effect was achieved when the more molecular ordering was expected by using a high MW conjugated polymer, phase-separated film dispersion process and a phospholipid-polyethylene glycol with alkyl tails for dense association with alkyl side chains of a conjugated polymer. On the other hand, the photodynamic effect was generally enhanced when less-organized molecular assemblies were expected by using a low MW conjugated polymer, a nanoprecipitation process, and/or a surfactant without compact alkyl chain association with a conjugated polymer. It was notable that fullerene acted differently on the photophysical properties of CPNs, depending on the molecular ordering. With limited fluctuation in the photothermal effect, the fullerene addition into CPNs enhanced the photodynamic effect under situations that can disrupt molecular ordering. In the meantime, the fullerene in CPNs enhanced the photothermal effect while maintaining the photodynamic effect with higher molecular ordering. Our results show that the combination of fullerenes can selectively and significantly increase the phototherapeutic capabilities based on molecular ordering of CPNs, suggesting a strategic approach for efficiency enhancement in the phototherapeutic medicinal applications.

Spatiotemporal Tracking of Near‐Infrared Fluorescent Single‐Walled Carbon Nanotubes in C. Elegans Nematodes Confined in a Microfluidics Platform

AbstractCaenorhabditis elegans (C. elegans) nematodes are a powerful model organism for diverse biological and biomedical studies, benefiting from their genetic similarities to humans, small size, and transparency. However, fluorescence imaging of C. elegans can be challenging due to the strong autofluorescence in the visible range, which obscures the signal of common fluorescent proteins or dyes. Single‐walled carbon nanotubes (SWCNTs) fluoresce in the near‐infrared (NIR) range, where there is no autofluorescence background. Herein, a platform is developed for in vivo NIR imaging of C. elegans gastrointestinal tract using biocompatible SWCNTs functionalized by single‐stranded DNA or phospholipid‐polyethylene glycol (PEG). The SWCNTs serve as fluorescent tracking probes within the worm gut, following internalization along with food intake. A microfluidic confinement device is employed to ensure an anesthetics‐free feeding environment, allowing spatiotemporal control over the SWCNTs intake imaging. Furthermore, improvements in spectral colocalization, real‐time detection of intracorporeal SWCNT dynamics, and digestive trajectory tracking are demonstrated. Owing to the unique optical properties of SWCNTs and the confinement of the worms in the microfluidics system, the proposed platform facilitates advanced in vivo imaging of C. elegans in both the visible and NIR regions, opening numerous avenues for advancing research of C. elegans and other microscopic model organisms.

(Invited, Digital Presentation) Carbon Nanotube Near-Infrared Fluorescent Labels, and Biodistribution of Carbon Nanotubes after Intravenous Injection

Single-walled carbon nanotubes (CNTs) are promising candidates for near-infrared (NIR) fluorescent labels in diagnostic fields. We here report a complex of oxygen-doped CNT (o-CNT) and streptavidin (SA) to prepare CNT-based NIR labels with a high reaction efficiency in immunoassays [1]. This complex specifically binds to biotin molecules by conjugating a linker molecule of phospholipid polyethylene glycol (PL-PEG) to SA (o-CNT-SA). The immunoprecipitation (IP) reaction efficiency between o-CNT-SA and biotin reaches 79.3% by uniformly covering the surface of o-CNTs with SA conjugated PL-PEG (SA-PEG). Further, we also report the biodistribution and toxicity of oxidized super-growth single-wall carbon nanotubes (oxSG) injected intravenously into mice over 3months [2].[1] K. Kojima, Y. Iizumi, M. Zhang, T. Okazaki, submitted.[2] M. Zhang, Y. Xu, M. Yang, M. Yudasaka, T. Okazaki, 15, 798-811 (2021).

Streptavidin-Conjugated Oxygen-Doped Single-Walled Carbon Nanotubes as Near-Infrared Labels for Immunoassays.

Single-walled carbon nanotubes (CNTs) are promising candidates for near-infrared (NIR) fluorescent labels in diagnostic fields. We report a complex of oxygen-doped CNT (o-CNT) and streptavidin (SA) for preparing CNT-based NIR labels with a high reaction efficiency in immunoassays. This complex specifically binds to biotin molecules by conjugating a linker molecule of phospholipid polyethylene glycol (PL-PEG) to SA (o-CNT-SA). The immunoprecipitation reaction efficiency between o-CNT-SA and biotin reaches 79.3% when the surface of o-CNTs is uniformly covered with SA-conjugated PL-PEG. The strong affinity between SA and biotin is useful for preparing CNT-based sensitive NIR fluorescent labels.

Precise Delivery of Nanomedicines to M2 Macrophages by Combining "Eat Me/Don't Eat Me" Signals and Its Anticancer Application.

Targeted delivery of nanomedicines to M2 tumor-associated macrophages (TAMs) has been proposed to reduce tumor promotion and enhance the efficacy of anticancer therapy. However, upregulated receptors on M2 TAMs are also expressed on M1 TAMs and other macrophages in normal tissues. Therefore, improving targeting specificity remains a key challenge. Here, we developed a precise M2 TAM-targeted delivery system using "eat-me" and "don't-eat-me" signals. A CD47-derived self-peptide ligand (don't-eat-me signal) and galactose ligand (eat-me signal) were introduced on liposomes. Cleavable phospholipid-polyethylene glycol was covered on the surface and could combine with the self-peptide to inhibit macrophage recognition even after immunoglobulin M adsorption and protect galactose from hepatic clearance to prolong the circulation time and promote the accumulation of liposomes in tumors. This detachable polymer can be removed by the redox microenvironment upon transcytosis through the tumor endothelium and re-expose the self-peptide and galactose. The self-peptide highly reduced M1 macrophage phagocytosis, and the galactose ligand enhanced the interaction between the liposomes and M2 macrophages. Thus, the modified liposomes enabled specific recognition of M1/M2 TAMs. In vitro evidence revealed reduced endocytosis of the liposomes by M1 macrophages. Moreover, in vivo studies demonstrated that doxorubicin-loaded liposomes efficiently eliminated M2 TAMs but did not affect M1 TAMs, enhancing the potency of the antitumor therapy. Collectively, our results demonstrate the potential of combining active escape and active targeting for precisely delivering a drug of interest to M2 macrophages and suggest its application in anticancer therapy.

Near-Infrared Fluorescence Immunoassay Using Streptavidin-Conjugated Oxygen-Doped Carbon Nanotubes

Single-walled carbon nanotubes (CNTs) have been introduced to near-infrared (NIR) immunoassay systems for recent years. NIR lights have low absorption and scattering of biological matter and avoid autofluorescence from blood. Compared with other NIR molecules and materials, CNTs have several advantages such as strong emissions, large Stokes-shifts and high photo-stabilities as NIR labels. Previously, our research group reported that immunoprecipitation (IP) was successfully conducted between IgG-conjugated CNTs and protein G magnetic beads. Although the system can ideally measure target analytes at concentrations as low as 600 pmol/L, the practical reaction efficiency was insufficient, around ~18% [1] .To improve the IP reaction yield, we here made the streptavidin-conjugated oxygen-doped CNTs (o-CNT-SA) that can selectively bind with biotin molecules. The o-CNTs [3] were coated by streptavidin which combined with phospholipid polyethylene glycol (SA-PEG). While IgG forms a 1:1 complex with an antigen, SA can bind biotin molecules at four sites. The strength of streptavidin-biotin interaction is larger than antigen-antibody interaction, therefore it expects that the reaction efficiency become larger.Some amounts of phospholipid polyethylene glycol (PL-PEG) were added to stabilize the dispersion state of o-CNT-SA. For assessing the IP reactivity, the fluorescent intensity ratio between the eluted solution and the original o-CNT-SA dispersion was calculated (Fig. 1(a)). Figure 1(b) shows the relationship of the reaction efficiency and SA-PEG/PL-PEG concentrations. The contour lines indicate the reaction efficiency. At around ~50 µg/mL of SA-PEG concentration, the reaction efficiency shows the maximum. On the other hand, the reaction efficiency is better when the PL-PEG concentration is low while o-CNTs aggregate occurs at the PL-PEG concentration of ~144 µg/mL. Figure 1(c) shows the NIR fluorescence spectra observed from the eluted and the original o-CNT-SA solutions. By adjusting the concentrations of o-CNTs, SA-PEG and PL-PEG, the IP reaction yield increased up to 79.3 %. In this condition, molecular number ratio of o-CNT and SA-PEGs was estimated to be 1 : 11 – 46. Comparing the length of o-CNT, 500 nm, with the diameter of streptavidin, 8.2 nm, it expects that SA-PEGs adsorb on almost all surface of o-CNT. In the poster, we will show the detailed experimental procedures and discuss the proper structure of the o-CNT-SA NIR label based on the obtained results.[1] Y. Iizumi et al., ACS Appl. Mater. Interfaces, 5, 7665 (2013).[2] Y. Iizumi et al., Sci. Rep., 8, 6272 (2018). Figure 1

Magnetic and GRPR-targeted reduced graphene oxide/doxorubicin nanocomposite for dual-targeted chemo-photothermal cancer therapy

Herein, we design a rGO-based magnetic nanocomposite by decorating rGO with citrate-coated magnetic nanoparticles (CMNP). The magnetic rGO (mrGO) was modified by phospholipid-polyethylene glycol to prepare PEGylated mrGO, for conjugating with gastrin-releasing peptide receptor (GRPR)-binding peptide (mrGOG). The anticancer drug doxorubicin (DOX) was bound to mrGO (mrGOG) by π-π stacking for drug delivery triggered by the low pH value in the endosome. The mrGOG showed enhanced photothermal effect under NIR irradiation, endorsing its role for dual targeted DOX delivery. With efficient DOX release in the endosomal environment and heat generation from light absorption in the NIR range, mrGOG/DOX could be used for combination chemo-photothermal therapy after intracellular uptake by cancer cells. We characterized the physico-chemical as well as biological properties of the synthesized nanocomposites. The mrGOG is stable in biological buffer solution, showing high biocompatibility and minimum hemolytic properties. Using U87 glioblastoma cells, we confirmed the magnetic drug targeting effect in vitro for selective cancer cell killing. The peptide ligand-mediated targeted delivery increases the efficiency of intracellular uptake of both nanocomposite and DOX up to ~3 times due to the over-expressed GRPR on U87 surface, leading to higher cytotoxicity. The increased cytotoxicity using mrGOG over mrGO was shown from a decreased IC50 value (0.70 to 0.48 μg/mL) and an increased cell apoptosis rate (19.8% to 47.1%). The IC50 and apoptosis rate changed further to 0.19 μg/mL and 76.8% in combination with NIR laser irradiation, with the photothermal effect supported from upregulation of heat shock protein HSP70 expression. Using U87 tumor xenograft model created in nude mice, we demonstrated that magnetic guidance after intravenous delivery of mrGOG/DOX could significantly reduce tumor size and prolong animal survival over free DOX and non-magnetic guided groups. Augmented with NIR laser treatment for 5 min, the anti-cancer efficacy significantly improves with elevated cell apoptosis and reduced cell proliferation. Together with safety profiles from hematological as well as major organ histological analysis of treated animals, the mrGOG nanocomposite is an effective nanomaterial for combination chemo-photothermal cancer therapy.

The Novel DPP-BDT Nanoparticles as Efficient Photoacoustic Imaging and Positron Emission Tomography Agents in Living Mice.

BackgroundMolecular imaging is of great benefit to early disease diagnosis and timely treatment. One of the most striking innovations is the development of multimodal molecular imaging technology, which integrates two or more imaging modalities, largely in view of making the best of the advantages of each modality while overcoming their respective shortcomings. Hence, engineering a versatile and easily prepared nanomaterial with integrating multimodal molecular imaging function holds great promise, but is still a great challenge.Materials and MethodsWe firstly designed and synthesized a BDT-DPP conjugated polymer and then noncovalent self-assembly with phospholipid-polyethylene glycol endowed BDT-DPP with water solubility and biocompatibility. Followed by [Cu] labeling, the acquired multifunctional nanoparticles (NPs) were studied in detail for the photophysical property. The cytotoxicity and biocompatibility of DPP-BDT NPs were examined through MTT assay and H&E stained analysis. In addition, we investigated the accumulation of the NPs in HepG2 tumor models by positron emission tomography (PET) and photoacoustic (PA) dual-mode imaging.Results and DiscussionThe DPP-BDT NPs exhibited excellent optical stability, strong near-infrared (NIR) light absorption as well as fine biocompatibility. After tail vein injection into the living mice, the PA signals in the neoplastic tissues were gradually increased and reached to the maximum at the 4-h post-injection, which was consistent with the PET analysis. Such strong PA and PET signals were attributed to the efficient NPs accumulation resulting from the enhanced permeability and retention (EPR) effect.ConclusionThe biocompatible DPP-BDT NPs demonstrated to be strong NIR absorption property and PAI sensitivity. Besides, these novel DPP-BDT NPs can act not only as a PA imaging contrast agent but also as an imaging agent for PET.

Fluorescent sp3 Defect-Tailored Carbon Nanotubes Enable NIR-II Single Particle Imaging in Live Brain Slices at Ultra-Low Excitation Doses

Cellular and tissue imaging in the second near-infrared window (NIR-II, ~1000–1350 nm) is advantageous for in vivo studies because of low light extinction by biological constituents at these wavelengths. However, deep tissue imaging at the single molecule sensitivity has not been achieved in the NIR-II window due to lack of suitable bio-probes. Single-walled carbon nanotubes have emerged as promising near-infrared luminescent molecular bio-probes; yet, their inefficient photoluminescence (quantum yield ~1%) drives requirements for sizeable excitation doses (~1–10 kW/cm2) that are significantly blue-shifted from the NIR-II region (<850 nm) and may thus ultimately compromise live tissue. Here, we show that single nanotube imaging can be achieved in live brain tissue using ultralow excitation doses (~0.1 kW/cm2), an order of magnitude lower than those currently used. To accomplish this, we synthesized fluorescent sp3-defect tailored (6,5) carbon nanotubes which, when excited at their first order excitonic transition (~985 nm) fluoresce brightly at ~1160 nm. The biocompatibility of these functionalized nanotubes, which are wrapped by encapsulation agent (phospholipid-polyethylene glycol), is demonstrated using standard cytotoxicity assays. Single molecule photophysical studies of these biocompatible nanotubes allowed us to identify the optimal luminescence properties in the context of biological imaging.

Characterization and Biodistribution Analysis of Oxygen-Doped Single-Walled Carbon Nanotubes Used as in Vivo Fluorescence Imaging Probes.

Single-walled carbon nanotubes (SWCNTs) show strong fluorescence in the 1000-1700 nm second near-infrared (NIR-II) wavelength range and are considered promising candidates for angiographic imaging probes. Oxygen-doped SWCNTs coated with phospholipid-polyethylene glycol (o-SWCNT-PEG) show exceptional potential, as they emit fluorescence at ∼1300 nm through excitation with 980 nm light. Here, with the aim of putting o-SWCNTs to practical use as an angiographic agent in animal experiments, the retention time after intravenous administration in the vasculature of mice and the biodistribution were studied. To provide bio affinity, the o-SWCNTs were coated with phospholipid polyethylene glycol. The intravenously injected o-SWCNT-PEG circulated within the vasculature for 3 h and cleared within 1 day. There was prominent fluorescence and Raman signals from the SWCNTs in the liver and spleen early in the experiment; the signals remained for 1 month. No apparent abnormalities in weight or appearance were observed after 2 months, suggesting low toxicity of o-SWCNT-PEG. These characteristics of o-SWCNT-PEG would make it useful as an angiographic imaging probe in the NIR-II wavelength range.

Fasting-dependent Vascular Permeability Enhancement in Brown Adipose Tissues Evidenced by Using Carbon Nanotubes as Fluorescent Probes

Brown adipose tissue (BAT), which is composed of thermogenic brown adipocytes (BA) and non-parenchymal components including vasculatures and extracellular matrix, contribute to the maintenance of body temperature. BAT distribution is detected by positron emission tomography-computed tomography (PET/CT) using 18F-fluorodeoxy glucose (18F-FDG) or single-photon-emission computed tomography-computed tomography (SPECT/CT) using [123/125I]-beta-methyl-p-iodophenyl-pentadecanoic acid. Although sympathetic nerve activity and thermogenic capacity of BA is downregulated under fasting conditions in mice, fasting-dependent structural changes and fluid kinetics of BAT remain unknown. Here we show that the fasting induces fine and reversible structural changes in the non-parenchymal region in murine BAT with widened intercellular spaces and deformed collagen bands as revealed by electron microscopy. Interestingly, a newly introduced near infrared fluorescent probe of single-walled carbon nanotubes (CNTs) coated with phospholipid polyethylene glycol (PLPEG) easily demonstrated enhanced vascular permeability in BAT by the fasting. PLPEG-CNTs extravasated and remained in intercellular spaces or further redistributed in parenchymal cells in fasted mice, which is a previously unknown phenomenon. Thus, PLPEG-CNTs provide a powerful tool to trace fluid kinetics in sub-tissue levels.

Green synthesis of highly dispersed ytterbium and thulium co-doped sodium yttrium fluoride microphosphors for in situ light upconversion from near-infrared to blue in animals

We report a simple, low cost and environmentally friendly method to prepare NaYF4:Yb3+, Tm3+ upconversion microphosphors (UCMPs) by thermal decomposition of rare earth-trifluoroacetate precursors using paraffin as the high boiling non-coordinating solvent. The UCMPs exhibited cubic phase with defined shape and bright upconversion luminescence. After coating with amphiphilic polymers of phospholipid-polyethylene glycol, the NaYF4:Yb3+, Tm3+ UCMPs were highly dispersed in aqueous solutions and exhibited low cytotoxicity. Furthermore, we explored the use of the micro-injected micro-sized NaYF4:Yb3+, Tm3+ particles for converting of near infrared into blue light in mice brain. The in vivo macroscopic upconversion luminescence imaging results showed that UCMPs located at 1mm depth in the brain could be clearly distinguished. Microscopic upconversion luminescence imaging of the brain sections in vitro revealed that the UCMPs embedded at the particular location in brain tissues of mice were stable without significant diffusion in two weeks.

Evaluation of multiwalled carbon nanotube cytotoxicity in cultures of human brain microvascular endothelial cells grown on plastic or basement membrane

There is a growing interest in the use of multiwalled carbon nanotubes (MWCNTs) to treat diseases of the brain. Little is known about the effects of MWCNTs on human brain microvascular endothelial cells (HBMECs), which make up the blood vessels in the brain. In our studies, we evaluate the cytotoxicity of MWCNTs and acid oxidized MWNCTs, with or without a phospholipid-polyethylene glycol coating. We determined the cytotoxic effects of MWCNTs on both tissue-mimicking cultures of HBMECs grown on basement membrane and on monolayer cultures of HBMECs grown on plastic. We also evaluated the effects of MWCNT exposure on the capacity of HBMECs to form rings after plating on basement membrane, a commonly used assay to evaluate angiogenesis. We show that tissue-mimicking cultures of HBMECs are less sensitive to all types of MWCNTs than monolayer cultures of HBMECs. Furthermore, we found that MWCNTs have little impact on the capacity of HBMECs to form rings. Our results indicate that relative cytotoxicity of MWCNTs is significantly affected by the type of cell culture model used for testing, and supports further research into the use of tissue-mimicking endothelial cell culture models to help bridge the gap between in vitro and in vivo toxicology.

Biocompatible custom ceria nanoparticles against reactive oxygen species resolve acute inflammatory reaction after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating subtype of stroke with a high mortality rate, for which there currently is no effective treatment. A perihematomal edema caused by an intense inflammatory reaction is more deleterious than the hematoma itself and can result in neurological deterioration and death. Ceria nanoparticles (CeNPs) are potent free radical scavengers with potential for biomedical applications. As oxidative stress plays a major role in post-ICH inflammation, we hypothesized that CeNPs might protect against ICH. To test this hypothesis, core CeNPs were synthesized using a modified reverse micelle method and covered with phospholipid-polyethylene glycol (PEG) to achieve biocompatibility. We investigated whether our custom-made biocompatible CeNPs have protective effects against ICH. The CeNPs reduced oxidative stress, hemin-induced cytotoxicity, and inflammation in vitro. In a rodent ICH model, intravenously administered CeNPs were mainly distributed in the hemorrhagic hemisphere, suggesting that they could diffuse through the damaged blood–brain barrier. Moreover, CeNPs attenuated microglia/macrophage recruitment around the hemorrhagic lesion and inflammatory protein expression. Finally, CeNP treatment reduced the brain edema by 68.4% as compared to the control. These results reveal the great potential of CeNPs as a novel therapeutic agent for patients with ICH.

Nanoemitters and innate immunity: the role of surfactants and bio-coronas in myeloperoxidase-catalyzed oxidation of pristine single-walled carbon nanotubes.

Single-walled carbon nanotubes (SWCNTs) are experimentally utilized in in vivo imaging and photothermal cancer therapy owing to their unique physicochemical and electronic properties. For these applications, pristine carbon nanotubes are often modified by polymer surfactant coatings to improve their biocompatibility, adding more complexity to their recognition and biodegradation by immuno-competent cells. Here, we investigate the oxidative degradation of SWCNTs catalyzed by neutrophil myeloperoxidase (MPO) using bandgap near-infrared (NIR) photoluminescence and Raman spectroscopy. Our results show diameter-dependence at the initial stages of the oxidative degradation of sodium cholate-, DNA-, and albumin-coated SWCNTs, but not phosphatidylserine-coated SWCNTs. Moreover, sodium deoxycholate- and phospholipid-polyethylene glycol coated SWCNTs were not oxidized under the same reaction conditions, indicating that a surfactant can greatly impact the biodegradability of a nanomaterial. Our data also revealed that possible binding between MPO and surfactant coated-SWCNTs was unfavorable, suggesting that oxidation is likely caused by a hypochlorite generated through halogenation cycles of free MPO, and not MPO bound to the surface of SWCNTs. The identification of SWCNT diameters and coatings that retain NIR fluorescence during the interactions with the components of an innate immune system is important for their applications in in vivo imaging.

Targeted placental delivery of insulin-like growth factor-II increases fetal weight in P0 mice

Targeted placental delivery of insulin-like growth factor-II increases fetal weight in P0 mice

Preparation and functionalization of boron nitride containing carbon nanohorns for boron neutron capture therapy

Boron neutron capture therapy requires boron carriers that can deliver abundant boron to tumors. To obtain such a carrier, we have prepared boron nitride (BN) containing carbon nanohorn aggregate (CNH) by heating CNHs with ammonia borane at 800°C. The obtained BN-CNH had a C:B:N mole ratio of 5:2:2, as estimated from X-ray photoemission spectroscopy. The nanohorn tubule walls had graphene–BN double layers or BN–graphene–BN triple layers. The graphite-like sheets constituting the CNHs together with the nanohorn tubules also had BN layers on their surfaces. BN release from BN-CNH was small in cell culture medium, and about 70–80% of the BNs remained on the CNHs. For selective accumulation in tumor cells, the BN-CNH was coated with phospholipid polyethylene glycol having folate (BN-CNH/PLPEG-FA). In primary cell culture experiments, human tumor KB cells overexpressing FA receptors ingested more BN-CNH/PLPEG-FA than those without FA, while normal human FHs 173We cells did not show preferential uptake due to FA. The quantity of boron per cell exceeded the criteria required for boron neutron capture therapy by more than 100times in the cell experiments. These results suggest that BN-CNH is potentially a good carrier for boron neutron capture therapy.

Size-tunable and monodisperse Tm³⁺/Gd³⁺-doped hexagonal NaYbF₄ nanoparticles with engineered efficient near infrared-to-near infrared upconversion for in vivo imaging.

Hexagonal NaYbF4:Tm3+ upconversion nanoparticles hold promise for use in high contrast near-infrared-to-near-infrared (NIR-to-NIR) in vitro and in vivo bioimaging. However, significant hurdles remain in their preparation and control of their morphology and size, as well as in enhancement of their upconversion efficiency. Here, we describe a systematic approach to produce highly controlled hexagonal NaYbF4:Tm3+ nanoparticles with superior upconversion. We found that doping appropriate concentrations of trivalent gadolinium (Gd3+) can convert NaYbF4:Tm3+ 0.5% nanoparticles with cubic phase and irregular shape into highly monodisperse NaYbF4:Tm3+ 0.5% nanoplates or nanospheres in a pure hexagonal-phase and of tunable size. The intensity and the lifetime of the upconverted NIR luminescence at 800 nm exhibit a direct dependence on the size distribution of the resulting nanoparticles, being ascribed to the varied surface-to-volume ratios determined by the different nanoparticle size. Epitaxial growth of a thin NaYF4 shell layer of ∼2 nm on the ∼22 nm core of hexagonal NaYbF4:Gd3+ 30%/Tm3+ 0.5% nanoparticles resulted in a dramatic 350 fold NIR upconversion efficiency enhancement, because of effective suppression of surface-related quenching mechanisms. In vivo NIR-to-NIR upconversion imaging was demonstrated using a dispersion of phospholipid-polyethylene glycol (DSPE-PEG)-coated core/shell nanoparticles in phosphate buffered saline.

Ultrafast fluorescence imaging in vivo with conjugated polymer fluorophores in the second near-infrared window.

In vivo fluorescence imaging in the second near-infrared window (1.0-1.7 μm) can afford deep tissue penetration and high spatial resolution, owing to the reduced scattering of long-wavelength photons. Here we synthesize a series of low-bandgap donor/acceptor copolymers with tunable emission wavelengths of 1,050-1,350 nm in this window. Non-covalent functionalization with phospholipid-polyethylene glycol results in water-soluble and biocompatible polymeric nanoparticles, allowing for live cell molecular imaging at >1,000 nm with polymer fluorophores for the first time. Importantly, the high quantum yield of the polymer allows for in vivo, deep-tissue and ultrafast imaging of mouse arterial blood flow with an unprecedented frame rate of >25 frames per second. The high time-resolution results in spatially and time resolved imaging of the blood flow pattern in cardiogram waveform over a single cardiac cycle (~200 ms) of a mouse, which has not been observed with fluorescence imaging in this window before.