A DNA/Upconversion Nanoparticle Complex Enables Controlled Co-Delivery of CRISPR-Cas9 and Photodynamic Agents for Synergistic Cancer Therapy

Photodynamic therapy (PDT) depends on the light-irradiated exciting of photosensitizer (PS) to generate reactive oxygen species (ROS), which faces challenges and limitations in hypoxia and antioxidant response of cancer cells, and limited tissue-penetration of light. Herein, a multifunctional DNA/upconversion nanoparticles (UCNPs) complex is developed which enables controlled co-delivery of CRISPR-Cas9, hemin, and protoporphyrin (PP) for synergistic PDT. An ultralong single-stranded DNA (ssDNA) is prepared via rolling circle amplification (RCA), which contains recognition sequences of single guide RNA (sgRNA) for loading Cas9 ribonucleoprotein (RNP), G-quadruplex sequences for loading hemin and PP, and linker sequences for combining UCNP. Cas9 RNP cleaves the antioxidant regulator nuclear factor E2-related factor 2 (Nrf2), improving the sensitivity of cancer cells to ROS, and enhancing the synergistic PDT effect. The G-quadruplex/hemin DNAzyme mimicks horseradish peroxidase (HRP) to catalyze the endogenous H2O2 to O2, overcoming hypoxia condition in tumors. The introduced UCNP converts NIR irradiation with deep tissue penetration to light with shorter wavelength, exciting PP to transform the abundant O2 to 1O2. The integration of gene editing and PDT allows substantial accumulation of 1O2 in cancer cells for enhanced cell apoptosis, and this synergistic PDT has shown remarkable therapeutic efficacy in a breast cancer mouse model.

Remotely Controllable Supramolecular Nanomedicine for Drug-Resistant Colorectal Cancer Therapy Caused by Fusobacterium nucleatum

Fusobacterium nucleatum (Fn) existing in the community of colorectal cancer (CRC) promotes CRC progression and causes chemotherapy resistance. Despite great efforts that have been made to overcome Fn-induced chemotherapy resistance by co-delivering antibacterial agents and chemotherapeutic drugs, increasing the drug-loading capacity and enabling controlled release of drugs remain challenging. In this study, a novel supramolecular upconversion nanoparticle (SUNP) is constructed by incorporating a positively charged polymer (PAMAM-LA-CD) with Fn inhibition capacity, a negatively charged platinum (IV) oxaliplatin prodrug (OXA-COOH), upconversion nanoparticle (UCNPs) and polyethylene glycol-azobenzene (PEG-Azo) to enhance drug-loading and enable on-demand drug release for drug-resistant CRC treatment. SUNPs exhibit high drug-loading capacity (30.8%) and good structural stability under normal physiological conditions, while disassembled upon exogenous NIR excitation and endogenous azo reductase in the CRC microenvironment to trigger drug release. In vitro and in vivo studies demonstrate that SUNPs presented good biocompatibility and robust performance to overcome chemoresistance, thereby significantly inhibiting Fn-infected cancer cell proliferation. This study leverages multiple dynamic chemical designs to integrate both advantages of drug loading and release in a single system, which provides a promising candidate for precision therapy of bacterial-related drug-resistant cancers.

Ultrasensitive Upconversion Nanoparticle Immunoassay for Human Serum Cardiac Troponin I Detection Achieved with Resonant Waveguide Grating

Selective detection of biomarkers at low concentrations in blood is crucial for the clinical diagnosis of many diseases but remains challenging. In this work, we aimed to develop an ultrasensitive immunoassay that can detect biomarkers in serum with an attomolar limit of detection (LOD). We proposed a sandwich-type heterogeneous immunosensor in a 3 × 3 well array format by integrating a resonant waveguide grating (RWG) substrate with upconversion nanoparticles (UCNPs). UCNPs were used to label a target biomarker captured by capture antibody molecules immobilized on the surface of the RWG substrate, and the RWG substrate was used to enhance the upconversion luminescence (UCL) of UCNPs through excitation resonance. The LOD of the immunosensor was greatly reduced due to the increased UCL of UCNPs and the reduction of nonspecific adsorption of detection antibody-conjugated UCNPs on the RWG substrate surface by coating the RWG substrate surface with a carboxymethyl dextran layer. The immunosensor exhibited an extremely low LOD [0.24 fg/mL (9.1 aM)] and wide detection range (1 fg/mL to 100 pg/mL) in the detection of cardiac troponin I (cTnI). The cTnI concentrations in human serum samples collected at different times during cyclophosphamide, epirubicin, and 5-fluorouracil (CEF) chemotherapy in a breast cancer patient were measured by an immunosensor, and the results showed that the CEF chemotherapy did cause cardiotoxicity in the patient. Having a higher number of wells in such an array-based biosensor, the sensor can be developed as a high-throughput diagnostic tool for clinically important biomarkers.

Remotely Activated DNA Probe System for the Detection and Imaging of Dual miRNAs

Cancers remain the leading cause of mortality worldwide. It is crucial to detect cancer at an early stage for improving survival rates. Biomarkers have precise implications for cancer progression. Here, we built a straightforward DNA probe system that could be activated by near-infrared light to detect dual miRNAs with a high specificity. This probe is built on the basis of upconversion nanoparticles, which could emit ultraviolet light and activate DNA probes adsorbed on the outer layer. The DNA probe system is remotely controlled through manipulation of the near-infrared (NIR) light, enabling simultaneous detection of dual miRNAs. The DNA nanosystem could be effectively endocytosed by cancer cells and reflect expression levels of dual miRNAs. Overall, this study demonstrates a promising remote-controlled DNA nanoplatform for the simultaneous detection of dual miRNAs, which has tremendous potential for precise cancer diagnostics and therapies.

Simultaneous Light-Triggered Release of Nitric Oxide and Carbon Monoxide from a Lipid-Coated Upconversion Nanosystem Inhibits Colon Tumor Growth

Gas therapy has gained noteworthy attention in biomedical research, with the rise of gas-releasing molecules enhancing their therapeutic potential, especially when integrated into nano-based drug delivery systems. Herein, we present a lipid-coated gas delivery system to simultaneously shuttle two gas-releasing molecules carrying nitric oxide (NO) and carbon monoxide (CO), respectively. Upconversion nanoparticles (UCNPs) are designed to generate photons at 360 nm upon 808 nm of near-infrared (NIR) irradiation. These in situ-generated UV photons trigger simultaneous NO and CO release from S-nitrosoglutathione (GSNO) and the CO-releasing molecule (CORM), respectively, which are coloaded into lipid-coated UCNP/GSNO/CORM/FA nanoparticles (LUGCF). LUGCF with a GSNO/CORM mass ratio of 2:1 is determined to be optimal in terms of synergistically instigating apoptosis in HCT116 and CT26 colon cancer cells, where both NO/CO are released and subsequent production of ROS are detected. This CO/NO combination nanoplatform exhibits a very effective inhibition of colon tumor growth in vivo at relatively low doses upon a mild 808 nm irradiation. Overall, we effectively integrated two therapeutic gas-releasing molecules in one NIR-responsive nanosystem, presenting a promising therapeutic strategy for future biomedical applications in dual-gas cancer therapy.

Optogenetic Calcium Ion Influx in Myoblasts and Myotubes by Near-Infrared Light Using Upconversion Nanoparticles

Bioactuators made of cultured skeletal muscle cells are generally driven by electrical or visible light stimuli. Among these, the technology to control skeletal muscle consisting of myoblasts genetically engineered to express photoreceptor proteins with visible light is very promising, as there is no risk of cell contamination by electrodes, and the skeletal muscle bioactuator can be operated remotely. However, due to the low biopermeability of visible light, it can only be applied to thin skeletal muscle films, making it difficult to realize high-power bioactuators consisting of thick skeletal muscle. To solve this problem, it is desirable to realize thick skeletal muscle bioactuators that can be driven by near-infrared (NIR) light, to which living tissue is highly permeable. In this study, as a promising first step, upconversion nanoparticles (UCNPs) capable of converting NIR light into blue light were bound to C2C12 myoblasts expressing the photoreceptor protein channelrhodopsin-2 (ChR2), and the myoblasts calcium ion (Ca2+) influx was remotely manipulated by NIR light exposure. UCNP-bound myoblasts and UCNP-bound differentiated myotubes were exposed to NIR light, and the intracellular Ca2+ concentrations were measured and compared to myoblasts exposed to blue light. Exposure of the UCNP-bound cells to NIR light was found to be more efficient than exposure to blue light in terms of stimulating Ca2+ influx.

A Novel and Rapid Smear Cytomorphology Detection Strategy Based on Upconversion Nanoparticles Immunolabeling Integrated with Wright's Staining for Accurate Diagnosis of Leukemia

Background

Accurate, sensitive, and rapid identification of leukemia cells in blood and bone marrow is of paramount significance for clinical diagnosis. An integrative technique combining traditional cytomorphology with immunophenotyping was proposed to improve the diagnostic efficiency in leukemia. On account of high photostability, biocompatibility, and signal-to-background ratio, upconversion nanoparticles (UCNPs) as luminescent labels have drawn substantial research scrutiny in immunolabeling.

Methods

To achieve simultaneous determination, NaYF4:Yb,Er UCNPs were coupled with CD38 antibodies to construct immunofluorescence probes that were developed to bind to diffuse large B cell lymphoma (DLBCL) cells, followed by Wright's staining that has been widely used in clinical work for morphological diagnosis. Further, the experimental conditions were optimized, such as medium, slice-making method, antibody dosage, incubation time, etc.

Results

The cell morphology and immunolabeling could be observed simultaneously, and its simple operation rendered it a possibility for clinical diagnosis. The developed immunolabeling assay could achieve DLBCL cell counting with high reproducibility and stability, and the detection limit was as low as 1.54 cell/slice (>3 σ/s). Moreover, the proposed method also realized real blood and bone marrow sample analysis, and the results were consistent with the clinical diagnosis.

Conclusion

Overall, this strategy can be carried out after simple laboratory training and has prospective biomedical applications in leukemia classification, diagnosis validation, and differential diagnostics.

Biomimetic Upconversion Nanoplatform Synergizes Photodynamic Therapy and Enhanced Radiotherapy against Tumor Metastasis

The easy recurrence and high metastasis of fatal tumors require the development of a combination therapy, which is able to overcome the drawbacks of monomodal strategies such as surgery, photodynamic therapy (PDT), and radiotherapy (RT). Taking the complementary advantages of PDT and RT, we present herein the integration of lanthanide-doped upconversion nanoparticles (UCNPs) with chlorin e6 (Ce6)-imbedded RBC membrane vesicles as a near-infrared-induced PDT agent for achieving synchronous depth PDT and RT with reduced radiation exposure. In such a nanoagent, gadolinium-doped UCNPs with strong X-ray attenuation ability act not only as a light transductor to activate the loaded photosensitizer Ce6 to allow PDT but also as a radiosensitizer to enhance RT. PDT with enhanced low-dose RT can achieve synergistic inhibition of tumor growth by producing reactive oxygen species to destroy local tumor cells and inducing strong T-cell-dependent immunogenic cell death to arrest systemic cancer metastasis. This combination of PDT and RT might be a potential appealing strategy for tumor eradication.

Dual-Photosensitizer Nanoplatform Based on Near-Infrared Excitation Orthogonal Emission Nanomaterials for Enhanced Photodynamic Therapy of Tumors

Photodynamic therapy (PDT) is considered as a promising therapeutic approach for clinical cancer treatment. However, the hypoxia of the tumor microenvironment leads to the low effect of single PDT. Here, a dual-photosensitizer nanoplatform based on near-infrared excitation orthogonal emission nanomaterials is constructed by introducing two kinds of photosensitizers into the nanosystem. Orthogonal emission upconversion nanoparticles (OE-UCNPs) were used as light conversion reagents to generate red emission under 980 nm irradiation and green emission under 808 nm irradiation. On the one hand, merocyanine 540 (MC540) is introduced as a photosensitizer (PS), which can absorb green light to generate reactive oxygen species (ROS) and trigger PDT for tumor treatment. On the other hand, another photosensitizer, chlorophyll a (Chla), which can be excited by red light, has also been introduced into the system to build a dual PDT nanotherapeutic platform. The introduction of photosensitizer Chla can synergistically increase ROS concentration to accelerate cancer cell apoptosis. Our research shows that this dual PDT nanotherapeutic platform combined with Chla has better therapeutic effects and effectively destroys cancer.

Dual Band-Edge Enhancing Overall Performance of Upconverted Near-Infrared Circularly Polarized Luminescence for Anticounterfeiting

Circularly polarized luminescence (CPL) is one of the critical chiroptical properties for chiral nanomaterials, which exhibit wide potential applications in many research fields. However, it remains a big challenge for real application, limited by their small luminescence dissymmetry factor or low emission intensity. Here, an upconverted near-infrared circularly polarized luminescence (UC-NIR-CPL) system is constructed based on the chiroptical property of chiral liquid crystals, embedding with the lanthanide-doped upconversion nanoparticles. More importantly, a strategy for improving the overall performance of UC-NIR-CPL was proposed and realized by taking advantage of the "dual-band-edge enhancement effect", wherein the g_lum value was amplified, while the NIR emission intensity showed dual enhancement and the threshold of excitation was decreased. Based on the improved overall performance of the UC-NIR-CPL, which can be used as a distinctive covert light, a kind of photonic barcode with multiple encryptions was realized. These findings will upgrade the level of information encryption through improving the overall performance of CPL-active materials.

Upconversion Nanoparticle-Based Cell Membrane-Coated cRGD Peptide Bioorthogonally Labeled Nanoplatform for Glioblastoma Treatment

Glioblastoma is hard to be eradicated partly because of the obstructive blood-brain barrier (BBB) and the dynamic autophagy activities of glioblastoma. Here, hydroxychloroquine (HDX)-loaded yolk-shell upconversion nanoparticle (UCNP)@Zn0.5Cd0.5S nanoparticle coating with the cyclic Arg-Gly-Asp (cRGD)-grafted glioblastoma cell membrane for near-infrared (NIR)-triggered treatment of glioblastoma is prepared for the first time. UCNPs@Zn0.5Cd0.5S (abbreviated as YSN, yolk-shell nanoparticle) under NIR radiation will generate reactive oxygen species for imposing cytotoxicity. HDX, the only available autophagy inhibitor in clinical studies, can enhance cytotoxicity by preventing damaged organelles from being recycled. The cRGD-decorated cell membrane allowed the HDX-loaded nanoparticles to efficiently bypass the BBB and specifically target glioblastoma cells. Exceptional treatment efficacy of the NIR-triggered chemotherapy and photodynamic therapy was achieved in U87 cells and in the mouse glioblastoma model as well. Our results provided proof-of-concept evidence that HDX@YSN@CCM@cRGD could overcome the delivery barriers and achieve targeted treatment of glioblastoma.

Catalytic Chiral Photochemistry Sensitized by Chiral Hosts-Grafted Upconverted Nanoparticles

Singlet chiral photocatalysis is highly challenging. Herein, we report fluorescence resonance energy transfer (FRET)-based chiral photocatalysis with γ-cyclodextrin (CD)-grafted lanthanide-doped upconverted nanoparticles (UCNP). The CD-modified UCNP strongly emits in the UV wavelength region upon excitation with a 980 nm laser, which selectively sensitizes the photosubstrates complexed by CD on the surface of UCNP through FRET. Therefore, enantiodifferentiating photocyclodimerization of anthracene or naphthalene derivatives sensitized by the CD-modified UCNP gives photoproducts in good enantioselectivity even in the presence of a catalytic amount of CD-modified UCNP. Moreover, the photocatalysts are readily separated and could be reused for at least six cycles without decreasing the enantioselectivity.

Plasmon-induced double-field-enhanced upconversion nanoprobes with near-infrared resonances for high-sensitivity optical bio-imaging

High-sensitivity optical imaging can be achieved through improving upconversion photoluminescence (UCPL) efficiency of localized surface plasmon resonance (LSPR)-enhanced excitation and emission. Herein, we report a type of UCPL nanoprobe, Au nanospheres assemblage@Gd₂O₃:Yb³⁺/Ln³⁺(Ln = Er, Ho, Tm), which exhibits emission enhancements from 46- to 96-fold as compared with its Au-free counterparts. The aggregation and interaction among Au nanospheres embedded inside the nanoprobe brings about three characteristic LSPR peaks in visible and near-infrared regions according to simulated and experimental absorption spectra, resulting in both excitation and emission fields simultaneously intensified all through the entire nanoprobe. We addressed a characteristic wavelength dependence on emission amplifications, which could be elucidated by a LSPR-enhanced UCPL mechanism and relevant rate equations that we addressed. The nanoprobe was verified to have a superior capability for optical bio-imaging with a negligible toxicityin vitroandin vivo. This study realizes a synchronous double-field-enhanced upconversion of optical nanoprobein situ, and may gain an insight into its mechanism underlying for LSPR-induced UCPL enhancement.

Near-Infrared Photo-controlled Permeability of a Biomimetic Polymersome with Sustained Drug Release and Efficient Tumor Therapy

Synthetic polymersomes have structure similarity to bio-vesicles and could disassemble in response to stimuli for "on-demand" release of encapsulated cargos. Though widely applied as a drug delivery carrier, the burst release mode with structure complete destruction is usually taken for most responsive polymersomes, which would shorten the effective drug reaction time and impair the therapeutic effect. Inspired by the cell organelles' communication mode via regulating membrane permeability for transportation control, we highlight here a biomimetic polymersome with sustained drug release over a specific period of time via near-infrared (NIR) pre-activation. The polymersome is prepared by the self-assembling amphiphilic diblock copolymer P(OEGMA-co-EoS)-b-PNBOC and encapsulates the hypoxia-activated prodrug AQ4N and upconversion nanoparticle (PEG-UCNP) in its hydrophilic centric cavity. Thirty minutes of NIR pre-activation triggers cross-linking of NBOC and converts the permeability of the polymersome with sustained AQ4N release until 24 h after the NIR pre-activation. The photosensitizer EoS is activated and aggravates environmental hypoxic conditions during a sustained drug release period to boost the AQ4N therapeutic effect. The combination of sustained drug release with concurrent hypoxia intensification results in a highly efficient tumor therapeutic effect both intracellularly and in vivo. This biomimetic polymersome will provide an effective and universal tumor therapeutic approach.

Steering Nanohelix and Upconverted Circularly Polarized Luminescence by Using Completely Achiral Components

Enormous attention has been paid to upconverted circularly polarized luminescence (UC-CPL). However, so far, chiral species are still needed in UC-CPL materials, either through the covalent or noncovalent bond. Here, we report a general supramolecular coassembly approach for the fabrication of UC-CPL systems from completely achiral components. We have found that an achiral C₃-symmetric molecule could form a chiral nanohelix through symmetry breaking, which could serve as a general helical platform to endow achiral guests with induced chirality and CPL activity. Two different photon upconversion systems, namely, triplet-triplet annihilation photon upconversion (TTA-UC) donor/acceptor pairs and inorganic lanthanide upconversion nanoparticles (UCNPs), are selected. When these two systems coassembled with the chiral nanohelix made from an achiral C₃-symmetric molecule, hybrid nanohelix structures formed and UC-CPL activity was induced. Through such an approach, we demonstrated that the fabrication of the UC-CPL materials does not require any chiral molecules. Moreover, we have shown that the polarization of UC-CPL can be tuned by the helicity of the nanohelix, which could be controlled through the seeded vortex. Our work provides a general approach for designing tunable UC-CPL materials from completely achiral motifs, which largely expands the research scope of the CPL materials.

Lanthanide-Doped Upconversion Nanoparticles for Super-Resolution Microscopy

Super-resolution microscopy offers a non-invasive and real-time tool for probing the subcellular structures and activities on nanometer precision. Exploring adequate luminescent probes is a great concern for acquiring higher-resolution image. Benefiting from the atomic-like transitions among real energy levels, lanthanide-doped upconversion nanoparticles are featured by unique optical properties including excellent photostability, large anti-Stokes shifts, multicolor narrowband emissions, tunable emission lifetimes, etc. The past few years have witnessed the development of upconversion nanoparticles as probes for super-resolution imaging studies. To date, the optimal resolution reached 28 nm (λ/36) for single nanoparticles and 82 nm (λ/12) for cytoskeleton structures with upconversion nanoparticles. Compared with conventional probes such as organic dyes and quantum dots, upconversion nanoparticle-related super-resolution microscopy is still in the preliminary stage, and both opportunities and challenges exist. In this perspective article, we summarized the recent advances of upconversion nanoparticles for super-resolution microscopy and projected the future directions of this emerging field. This perspective article should be enlightening for designing efficient upconversion nanoprobes for super-resolution imaging and promote the development of upconversion nanoprobes for cell biology applications.

Light-Emitting Diode Excitation for Upconversion Microscopy: A Quantitative Assessment

Lanthanide-based upconversion nanoparticles (UCNPs) generally require high power laser excitation. Here, we report wide-field upconversion microscopy at single-nanoparticle sensitivity using incoherent excitation of a 970 nm light-emitting diode (LED). We show that due to its broad emission spectrum, LED excitation is about 3 times less effective for UCNPs and generates high background compared to laser illumination. To counter this, we use time-gated luminescence detection to eliminate the residual background from the LED source, so that individual UCNPs with high sensitizer (Yb³⁺) doping and inert shell protection become clearly identified under LED excitation at 1.18 W cm^-2, as confirmed by correlated electron microscopy images. Hydrophilic UCNPs are obtained by polysaccharide coating via a facile ligand exchange protocol to demonstrate imaging of cellular uptake using LED excitation. These results suggest a viable approach to bypassing the limitations associated with high-power lasers when applying UCNPs and upconversion microscopy to life science research.

NIR Photoregulated Theranostic System Based on Hexagonal-Phase Upconverting Nanoparticles for Tumor-Targeted Photodynamic Therapy and Fluorescence Imaging

Although photodynamic therapy (PDT) is an effective, minimally invasive therapeutic modality with advantages in highly localized and specific tumor treatments, large and deep-seated cancers within the body cannot be successfully treated due to low transparency to visible light. To improve the therapeutic efficiency of tumor treatment in deep tissue and reduce the side effects in normal tissue, this study developed a near-infrared (NIR)-triggered upconversion nanoparticle (UCNP)-based photosensitizer (PS) carrier as a new theranostics system. The NaYF4:Yb/Er UCNPs were synthesized by a hydrothermal method, producing nanoparticles of a uniformly small size (≈20 nm) and crystalline morphology of the hexagonal phase. These UCNPs were modified with folic acid-conjugated biocompatible block copolymers through a bidentate dihydrolipoic acid linker. The polymer modified hexagonal phase UCNPs (FA-PEAH-UCNPs) showed an improved dispersibility in the aqueous solution and strong NIR-to-vis upconversion fluorescence. The hydrophobic PS, pheophorbide a (Pha), was then conjugated to the stable vectors. Moreover, these UCNP-based Pha carriers containing tumor targeting folic acid ligands exhibited the significantly enhanced cellular uptake efficiency as well as PDT treatment efficiency. These results suggested that this system could extend the excitation wavelength of PDT to the NIR region and effectively improve therapeutic efficiency of PSs.

Microscale Self-Assembly of Upconversion Nanoparticles Driven by Block Copolymer

Lanthanide-based upconversion nanoparticles can convert low-energy excitation to high-energy emission. The self-assembled upconversion nanoparticles with unique structures have considerable promise in sensors and optical devices due to intriguing properties. However, the assembly of isotropic nanocrystals into anisotropic structures is a fundamental challenge caused by the difficulty in controlling interparticle interactions. Herein, we report a novel approach for the preparation of the chain-like assemblies of upconversion nanoparticles at different scales from nano-scale to micro-scale. The dimension of chain-like assembly can be fine-tuned using various incubation times. Our study observed Y-junction aggregate morphology due to the flexible nature of amphiphilic block copolymer. Furthermore, the prepared nanoparticle assemblies of upconversion nanoparticles with lengths up to several micrometers can serve as novel luminescent nanostructure and offer great opportunities in the fields of optical applications.

Novel Carbon-Based Magnetic Luminescent Nanocomposites for Multimodal Imaging

Multifunctional nanocomposites can combine multiple functions into a single nanosystem and thus have attracted extensive interest in various fields. The combination of magnetic and upconversion luminescent nanoparticles into one single nanoplatform, which have a good application in biomedical fields such as bio-magnetic separation, magnetic resonance imaging (MRI), and optical imaging, is highly desirable. Here we reported multifunctional nanocomposites by using hollow carbon sphere to integrate magnetic Fe₃O₄ and upconversion nanoparticles (UCNPs) into one nanosystem. The as-prepared UCNPs/Fe₃O₄@h-C have near-infrared (NIR) luminescence under 980 nm excitation and superparamagnetism. In addition, since the carbon layer can absorb NIR light and transfer it into heat with high efficiency, the nanocomposites can realize photo thermal (PT), upconversion luminescence (UCL) and MRI tri-mode imaging. The UCNPs/Fe₃O₄@h-C might be further utilized as a potential theranostic agent, including its in-depth monitoring through luminescent imaging and MRI diagnosis, as well as its direct use in tumors as a photothermal therapy (PTT) agent.

Molecular Antenna-Sensitized Upconversion Nanoparticle for Temperature Monitored Precision Photothermal Therapy

Background

Photothermal therapy with accurate and real-time temperature detection is desired in clinic. Upconversion nanocrystals (UCNs) are candidate materials for simultaneous temperature detection and photothermal agents carrying. However, the weak luminescence and multiple laser excitations of UCNs limit their application in thermal therapy.

Materials and Methods

NaYF₄:Yb³⁺,Er³⁺,Nd³⁺, PL-PEG-NH₂, IR-806 and folic acid are selected as structural components. A nanoprobe (NP) integrated with efficient photothermal conversion and sensitive temperature detection capabilities is synthesized for precise photothermal therapy. The probes are based on near-infrared upconversion nanocrystals doped with Yb, Er and Nd ions, which can be excited by 808 nm light. IR-806 dye molecules are modified on the surface as molecular antennas to strongly absorb near-infrared photons for energy transfer and conversion.

Results

The results show that under an 808 nm laser irradiation upconversion luminescence of the nanocrystals is enhanced based on both the Nd ion absorption and the FRET energy transfer of IR-806. The luminescence ratio at 520 and 545 nm is calculated to accurately monitor the temperature of the nanoparticles. The temperature of the nanoprobes increases significantly through energy conversion of the molecular antennas. The nanoparticles are found successfully distributed to tumor cells and tumor tissue due to the modification of the biocompatible molecules on the surface. Tumor cells can be killed efficiently based on the photothermal effect of the NPs. Under the laser irradiation, temperature at mouse tumor site increases significantly, tissue necrosis and tumor cell death can be observed.

Conclusion

Precision photothermal therapy can thus be achieved by highly efficient near-infrared light absorption and accurate temperature monitoring, making it promising for tumor treatment, as well as the biological microzone temperature detection.

Facile Strategy to Synthesize Magnetic Upconversion Nanoscale Metal-Organic Framework Composites for Theranostics Application

Recently, the design of a theranostics system has involved increasing attention in the area of biomedical applications. In many cases, the intricate synthesis process of upconversion nanoparticle-based composite materials limits the use of theranostics applications. To address this challenge, a nanocomposite has been successfully fabricated by the conjugation of magnetic NaGdF₄:Yb/Er nanoparticles as an imaging agent and MIL-53(Fe) as a drug carrier through a single step. Simultaneously, folic acid is encapsulated on the surface of the nanocomposite by conjugation chemistry to achieve the targeted drug delivery applications. The synthesized nanocomposite exhibits a sufficient amount of loading ability toward the model anticancer doxorubicin and possesses pH-responsive drug release. The functionalized nanocomposite not only possesses excellent colloidal stability and good magnetic and fluorescence property but also shows superior biocompatibility, strong tumor cell growth inhibitory effect, and cancer-enhanced cellular uptake. It is expected that the synthesized nanocomposite can also serve as a platform for both T₁ and T₂ MRI contrast agents.

Time-Resolved Activation of pH Sensing and Imaging in Vivo by a Remotely Controllable DNA Nanomachine

Construction of probes or nanodevices capable of sensing pH with high spatial and temporal precision remains a challenge, despite their importance in monitoring of diverse physiological and pathological processes. Here we disclose the first remotely and noninvasively controlled DNA nanomachine that can monitor pH in live cells and animals in a temporally programmable manner. The nanomachine is designed by rational engineering of the DNA motif with a light-responsive element and further combination with an upconversion nanoparticle that works as a transducer to manipulate the nanomachine with the high precision of NIR light. The nanomachine not only allows for activated fluorescent imaging of intracellular pH, but it also can exert spatiotemporal control over its pH sensing activity in tumor-bearing mice by NIR light irradiation at a chosen time and place. This work illustrates the potential of combining DNA nanotechnology with upconversion tools to yield a precisely controlled nanomachine for temporally resolved pH sensing and imaging.

The Bioavailability, Biodistribution, and Toxic Effects of Silica-Coated Upconversion Nanoparticles in vivo

Lanthanide-doped upconversion nanoparticles can convert long wavelength excitation radiation to short wavelength emission. They have great potential in biomedical applications, such as bioimaging, biodetection, drug delivery, and theranostics. However, there is little information available on their bioavailability and biological effects after oral administration. In this study, we systematically investigated the bioavailability, biodistribution, and toxicity of silica-coated upconversion nanoparticles administrated by gavage. Our results demonstrate that these nanoparticles can permeate intestinal barrier and enter blood circulation by microstructure observation of Peyer's patch in the intestine. Comparing the bioavailability and the biodistribution of silica-coated upconversion nanoparticles with oral and intravenous administration routes, we found that the bioavailability and biodistribution are particularly dependent on the administration routes. After consecutive gavage for 14 days, the body weight, pathology, Zn and Cu level, serum biochemical analysis, oxidative stress, and inflammatory cytokines were studied to further evaluate the potential toxicity of the silica-coated upconversion nanoparticles. The results suggest that these nanoparticles do not show overt toxicity in mice even at a high dose of 100 mg/kg body weight.

Mammalian Near-Infrared Image Vision through Injectable and Self-Powered Retinal Nanoantennae

Mammals cannot see light over 700 nm in wavelength. This limitation is due to the physical thermodynamic properties of the photon-detecting opsins. However, the detection of naturally invisible near-infrared (NIR) light is a desirable ability. To break this limitation, we developed ocular injectable photoreceptor-binding upconversion nanoparticles (pbUCNPs). These nanoparticles anchored on retinal photoreceptors as miniature NIR light transducers to create NIR light image vision with negligible side effects. Based on single-photoreceptor recordings, electroretinograms, cortical recordings, and visual behavioral tests, we demonstrated that mice with these nanoantennae could not only perceive NIR light, but also see NIR light patterns. Excitingly, the injected mice were also able to differentiate sophisticated NIR shape patterns. Moreover, the NIR light pattern vision was ambient-daylight compatible and existed in parallel with native daylight vision. This new method will provide unmatched opportunities for a wide variety of emerging bio-integrated nanodevice designs and applications. VIDEO ABSTRACT.

Responsive Assembly of Upconversion Nanoparticles for pH-Activated and Near-Infrared-Triggered Photodynamic Therapy of Deep Tumors

Upconversion nanoparticle (UCNP)-mediated photodynamic therapy has shown great effectiveness in increasing the tissue-penetration depth of light to combat deep-seated tumors. However, the inevitable phototoxicity to normal tissues resulting from the lack of tumor selectivity remains as a major challenge. Here, the development of tumor-pH-sensitive photodynamic nanoagents (PPNs) comprised of self-assembled photosensitizers grafted pH-responsive polymeric ligands and UCNPs is reported. Under neutral pH conditions, photosensitizers aggregated in the PPNs are self-quenched; however, upon entry into a tumor microenvironment with lower pH, the PPNs not only exhibit enhanced tumor-cell internalization due to charge reversal but also are further disassembled into well-dispersed nanoparticles in the endo/lysosomes of tumor cells, enabling the efficient activation of photosensitizers. The results demonstrate the attractive properties of both UCNP-mediated deep-tissue penetration of light and high therapeutic selectivity in vitro and in vivo.

Upconversion Nanoparticles/Hyaluronate-Rose Bengal Conjugate Complex for Noninvasive Photochemical Tissue Bonding

The recent progress in photonic nanomaterials has contributed greatly to the development of photomedicines. However, the finite depth of light penetration is still a serious limitation, constraining their clinical applications. Here, we developed a poly(allylamine) (PAAm)-modified upconversion nanoparticle/hyaluronate-rose bengal (UCNP/PAAm/HA-RB) conjugate complex for photochemical bonding of deep tissue with near-infrared (NIR) light illumination. Compared to the conventional invasive treatment via suturing and stapling, the UCNP/PAAm/HA-RB conjugate complex could be noninvasively delivered into the deep tissue and accelerate the tissue bonding upon NIR light illumination. HA in the outer layer of the complex facilitated the penetration of RB into the collagen layer of the dermis. The NIR light triggered UCNP of NaYF₄: Yb/Er (Y:Yb:Er = 78:20:2) in the complex to illuminate visible green light under the skin tissue. The activated RB in the HA-RB conjugate by the green light induced radical formation for the cross-linking of incised collagen matrix. An in vitro light propagation test and collagen fibrillogenesis analysis, an in vivo animal tissue bonding test, and an ex vivo tensile strength test of dissected skin tissues confirmed the successful photochemical tissue bonding effect of the UCNP/PAAm/HA-RB conjugate complex.

Targeting Osteocytes to Attenuate Early Breast Cancer Bone Metastasis by Theranostic Upconversion Nanoparticles with Responsive Plumbagin Release

The early detection and thus treatment of breast cancer bone metastasis remain a big challenge clinically. As the most abundant cells within bone tissue, osteocytes have been found to manipulate the activity of early cancer bone metastasis by its crosstalk with cancer cells and osteoclasts. However, conventional bone-targeting nanomedicine has limited bone-lesion specificity and ignores the vital role of osteocytes during breast cancer bone metastasis. Also, it lacks detailed insight into the therapeutic mechanisms, which hinders the following translational practice. Previously, we have shown that a combination of zoledronic acid (ZA) and plumbagin (PL) synergistically alleviates cancer-induced bone destruction. Herein, we further develop a pH-responsive bone-targeting drug delivery system, i.e., the ZA-anchored bimodal mesoporous slica covered gadolinium(III) upconversion nanoparticles loaded with PL, to detect and treat bone metastasis sensitively and specifically at an early stage. This multifunctional nanosystem can target osteocytes to release PL as controlled by pH, decreasing osteocytic RANKL expression synergistically through the structural simulation of adenosine phosphate, which competitively inhibits the phosphorylation of osteocytic protein kinase-a, cAMP-response element binding protein, extracellular regulated protein kinase, and c-Jun N-terminal kinase. More importantly, by establishing a breast cancer bone metastasis mice model via intracardiac injection, we show that tumoriogenesis and osteoclastogenesis can both be attenuated significantly. We thereby realize the effective theranostics of tiny bone metastasis in breast cancer bone metastasis. Our work highlights the significance of theranostic nanomedicine and osteocyte-targeting therapy in the treatment of early bone metastasis, which could be applied in achieving efficient theranostic effects for other bone diseases.

Household Fluorescent Lateral Flow Strip Platform for Sensitive and Quantitative Prognosis of Heart Failure Using Dual-Color Upconversion Nanoparticles

Heart failure (HF) is the end-stage of cardiovascular diseases, which is associated with a high mortality rate and high readmission rate. Household early diagnosis and real-time prognosis of HF at bedside are of significant importance. Here, we developed a highly sensitive and quantitative household prognosis platform (termed as UC-LFS platform), integrating a smartphone-based reader with multiplexed upconversion fluorescent lateral flow strip (LFS). Dual-color core-shell upconversion nanoparticles (UCNPs) were synthesized as probes for simultaneously quantifying two target antigens associated with HF, i.e., brain natriuretic peptide (BNP) and suppression of tumorigenicity 2 (ST2). With the fluorescent LFS, we achieved the specific detection of BNP and ST2 antigens in spiked samples with detection limits of 5 pg/mL and 1 ng/mL, respectively, both of which are of one order lower than their clinical cutoff. Subsequently, a smartphone-based portable reader and an analysis app were developed, which could rapidly quantify the result and share prognosis results with doctors. To confirm the usage of UC-LFS platform for clinical samples, we detected 38 clinical serum samples using the platform and successfully detected the minimal concentration of 29.92 ng/mL for ST2 and 17.46 pg/mL for BNP in these clinical samples. Comparing the detection results from FDA approved clinical methods, we obtained a good linear correlation, indicating the practical reliability and stability of our developed UC-LFS platform. Therefore, the developed UC-LFS platform is demonstrated to be highly sensitive and specific for sample-to-answer prognosis of HF, which holds great potential for risk assessment and health monitoring of post-treatment patients at home.

Molecular Imaging of Vulnerable Atherosclerotic Plaques in Vivo with Osteopontin-Specific Upconversion Nanoprobes

Owing to the high mortality rate of cardiovascular diseases, developing novel noninvasive diagnostic methods becomes urgent and mandatory. It is well-known that the rupture of vulnerable plaques directly leads to deadly consequences. However, differentiating vulnerable plaques from stable plaques remains challenging in the clinic. In the current study, osteopontin (OPN), a secreted biomarker associated with macrophages and foamy macrophages, was selected as a target for identifying the vulnerable plaques. A dual modality imaging probe was constructed by covalently attaching an OPN antibody to NaGdF₄:Yb,Er@NaGdF₄ upconversion nanoparticles. Upon intravenous injection of the resulting probes, upconversion optical imaging was performed to visualize the plaques induced by altering the shear stress in carotid arteries of a mouse model. The imaging studies revealed that the signals of vulnerable and stable plagues induced by lowered shear stress and oscillatory shear stress, respectively, presented significantly different signal intensities, implying that the current probe and imaging strategy are potentially useful for a precise diagnosis of atherosclerosis plaques.

Erythrocyte Membrane-Coated Upconversion Nanoparticles with Minimal Protein Adsorption for Enhanced Tumor Imaging

Upconversion nanoparticles (UCNPs) with superior optical and chemical features have been broadly employed for in vivo cancer imaging. Generally, UCNPs are surface modified with ligands for cancer active targeting. However, nanoparticles in biological fluids are known to form a long-lived "protein corona", which covers the targeting ligands on nanoparticle surface and dramatically reduces the nanoparticle targeting capabilities. Here, for the first time, we demonstrated that by coating UCNPs with red blood cell (RBC) membranes, the resulting cell membrane-capped nanoparticles (RBC-UCNPs) adsorbed virtually no proteins when exposed to human plasma. We further observed in various scenarios that the cancer targeting ability of folic acid (FA)-functionalized nanoparticles (FA-RBC-UCNPs) was rescued by the cell membrane coating. Next, the FA-RBC-UCNPs were successfully utilized for enhanced in vivo tumor imaging. Finally, blood parameters and histology analysis suggested that no significant systematic toxicity was induced by the injection of biomimetic nanoparticles. Our method provides a new angle on the design of targeted nanoparticles for biomedical applications.

Plasmon-Enhanced Photodynamic Cancer Therapy by Upconversion Nanoparticles Conjugated with Au Nanorods

Photodynamic therapy (PDT) based on photosensitizers (PSs) constructed with nanomaterials has been widely applied to treat cancer. This therapy is characterized by an improved PS accumulation in tumor regions. However, challenges, such as short penetration depth of light and low extinction coefficient of PSs, limit PDT applications. In this study, a nanocomposite consisting of NaYF₄:Yb/Er upconversion nanoparticles (UCPs) conjugated with gold nanorods (Au NRs) was developed to improve the therapeutic efficiency of PDT. Methylene blue (MB) was embedded in a silica shell for plasmon-enhanced PDT. UCPs served as a light converter from near-infrared (NIR) to visible light to excite MB to generate reactive oxygen species (ROS). Au NRs could effectively enhance upconversion efficiency and ROS content through a localized surface plasmon resonance (SPR) effect. Silica shell thickness was adjusted to investigate the optimized MB loading amount, ROS production capability, and efficient distance for plasmon-enhanced ROS production. The mechanism of plasmon-enhanced PDT was verified by enhancing UC luminescence intensity through the plasmonic field and by increasing the light-harvesting capability and absorption cross section of the system. This process improved the ROS generation by comparing the exchange of Au NRs to Au nanoparticles with different SPR bands. NIR-triggered nanocomposites of UCP@SiO₂:MB-NRs were significantly confirmed by improving ROS generation and further modifying folic acid (FA) to develop an active component targeting OECM-1 oral cancer cells. Consequently, UCP@SiO₂:MB-NRs-FA could highly produce ROS and undergo efficient PDT in vitro and in vivo. The mechanism of PDT treatment by UCP@SiO₂:MB-NRs-FA was evaluated via the cell apoptosis pathway. The proposed process is a promising strategy to enhance ROS production through plasmonic field enhancement and thus achieve high PDT therapeutic efficacy.

Optogenetic Immunomodulation: Shedding Light on Antitumor Immunity

Microbial opsin-based optogenetic tools have been transformative for neuroscience. To extend optogenetic approaches to the immune system to remotely control immune responses with superior spatiotemporal precision, pioneering tools have recently been crafted to modulate lymphocyte trafficking, inflammasome activation, dendritic cell (DC) maturation, and antitumor immunity through the photoactivation of engineered chemokine receptors and calcium release-activated calcium channels. We highlight herein some conceptual design strategies for installing light sensitivities into the immune signaling network and, in parallel, we propose potential solutions for in vivo optogenetic applications in living organisms with near-infrared light-responsive upconversion nanomaterials. Moreover, to move beyond proof-of-concept into translational applications, we discuss future prospects for integrating personalized immunoengineering with optogenetics to overcome critical hurdles in cancer immunotherapy.

Upconversion Nanoparticle-Based Förster Resonance Energy Transfer for Detecting DNA Methylation

Aberrant methylation of a crucial CpG island is the main mechanism for the inactivation of CDKN2A in the early stages of carcinogenesis. Therefore, the detection of DNA methylation with high sensitivity and specificity is important, and various detection methods have been developed. Recently, upconversion nanoparticles (UCNPs) have been found to display a high signal-to-noise ratio and no photobleaching, making them useful for diagnostic applications. In this pilot study, we applied UCNPs to the detection of CDKN2A methylation and evaluated the feasibility of this system for use in molecular diagnostics. DNA PCR was performed using biotinylated primers, and the PCR amplicon was then intercalated with SYTOX Orange dye, followed by incubation with streptavidin-conjugated UCNPs. Fluorescence detection of the Förster resonance energy transfer (FRET) of the UCNPs (MS-UC-FRET) was then performed, and the results were compared to those from real-time PCR (RQ-PCR) and pyrosequencing. Detection by MS-UC-FRET was more sensitive than that by either RQ-PCR or pyrosequencing. Our results confirmed the success of our MS-UC-FRET system for detecting DNA methylation and demonstrated the potential application of this system in molecular diagnostics.

Bacteria-Mediated Hypoxia-Specific Delivery of Nanoparticles for Tumors Imaging and Therapy

The hypoxia region in a solid tumor has been recognized as a complex microenvironment revealing very low oxygen concentration and deficient nutrients. The hypoxic environment reduces the susceptibility of the cancer cells to anticancer drugs, low response of free radicals, and less proliferation of cancer cells in the center of the solid tumors. However, the reduced oxygen surroundings provide an appreciable habitat for anaerobic bacteria to colonize. Here, we present the bacteria-mediated targeting hypoxia to offer the expandable spectra for diagnosis and therapy in cancer diseases. Two delivery approaches involving a cargo-carrying method and an antibody-directed method were designed to deliver upconversion nanorods for imaging and Au nanorods for photothermal ablation upon near-infrared light excitation for two forms of the anaerobic Bifidobacterium breve and Clostridium difficile. The antibody-directed strategy shows the most effective treatment giving stronger imaging and longer retention period and effective therapy to completely remove tumors.

A Paper-Based Sandwich Format Hybridization Assay for Unlabeled Nucleic Acid Detection Using Upconversion Nanoparticles as Energy Donors in Luminescence Resonance Energy Transfer

Bioassays based on cellulose paper substrates are gaining increasing popularity for the development of field portable and low-cost diagnostic applications. Herein, we report a paper-based nucleic acid hybridization assay using immobilized upconversion nanoparticles (UCNPs) as donors in luminescence resonance energy transfer (LRET). UCNPs with intense green emission served as donors with Cy3 dye as the acceptor. The avidin functionalized UCNPs were immobilized on cellulose paper and subsequently bioconjugated to biotinylated oligonucleotide probes. Introduction of unlabeled oligonucleotide targets resulted in a formation of probe-target duplexes. A subsequent hybridization of Cy3 labeled reporter with the remaining single stranded portion of target brought the Cy3 dye in close proximity to the UCNPs to trigger a LRET-sensitized emission from the acceptor dye. The hybridization assays provided a limit of detection (LOD) of 146.0 fmol and exhibited selectivity for one base pair mismatch discrimination. The assay was functional even in undiluted serum samples. This work embodies important progress in developing DNA hybridization assays on paper. Detection of unlabeled targets is achieved using UCNPs as LRET donors, with minimization of background signal from paper substrates owing to the implementation of low energy near-infrared (NIR) excitation.

Compact, Programmable, and Stable Biofunctionalized Upconversion Nanoparticles Prepared through Peptide-Mediated Phase Transfer for High-Sensitive Protease Sensing and in Vivo Apoptosis Imaging

Protease represents an important class of biomarkers for disease diagnostics and drug screening. Conventional fluorescence-based probes for in vivo protease imaging suffer from short excitation wavelengths and poor photostability. Upconversion nanoparticles (UCNPs) hold great promise for biosensing and bioimaging because of their deep-tissue excitability, robust photostability, and minimal imaging background. However, producing highly stable and compact biofunctionalized UCNP probes with optimal bioresponsivity for in vivo imaging of protease activities still remains challenging and has not been previously demonstrated. Herein, we report facile preparation of highly compact and stable biofunctionalized UCNPs through peptide-mediated phase transfer for high-sensitive detection of protease in vitro and in vivo. We demonstrate that the polyhistidine-containing chimeric peptides could displace oleic acid molecules capped on UCNPs synthesized in organic solvents and, thereby, directly transfer UCNPs from the chloroform phase to the water phase. The resulting UCNPs possess high stability, programmable surface properties, and a compact coating layer with minimized thickness for efficient luminescence resonance energy transfer (LRET). On the basis of this strategy, we prepared LRET-based UCNP probes with optimal bioresponsivity for in vitro high-sensitive detection of trypsin and in vivo imaging of apoptosis for chemotherapy efficacy evaluation. The reported strategy could be extended to construct a variety of peptide-functionalized UCNPs for various biomedical applications.

Real-Time Monitoring of ATP-Responsive Drug Release Using Mesoporous-Silica-Coated Multicolor Upconversion Nanoparticles

Stimuli-responsive drug delivery vehicles have garnered immense interest in recent years due to unparalleled progress made in material science and nanomedicine. However, the development of stimuli-responsive devices with integrated real-time monitoring capabilities is still in its nascent stage because of the limitations of imaging modalities. In this paper, we describe the development of a polypeptide-wrapped mesoporous-silica-coated multicolor upconversion nanoparticle (UCNP@MSN) as an adenosine triphosphate (ATP)-responsive drug delivery system (DDS) for long-term tracking and real-time monitoring of drug release. Our UCNP@MSN with multiple emission peaks in UV-NIR wavelength range was functionalized with zinc-dipicolylamine analogue (TDPA-Zn(2+)) on its exterior surface and loaded with small-molecule drugs like chemotherapeutics in interior mesopores. The drugs remained entrapped within the UCNP-MSNs when the nanoparticles were wrapped with a compact branched polypeptide, poly(Asp-Lys)-b-Asp, because of multivalent interactions between Asp moieties present in the polypeptide and the TDPA-Zn(2+) complex present on the surface of UCNP-MSNs. This led to luminescence resonance energy transfer (LRET) from the UCNPs to the entrapped drugs, which typically have absorption in UV-visible range, ultimately resulting in quenching of UCNP emission in UV-visible range while retaining their strong NIR emission. Addition of ATP led to a competitive displacement of the surface bound polypeptide by ATP due to its higher affinity to TDPA-Zn(2+), which led to the release of the entrapped drugs and subsequent elimination of LRET. Monitoring of such ATP-triggered ratiometric changes in LRET allowed us to monitor the release of the entrapped drugs in real-time. Given these results, we envision that our proposed UCNP@MSN-polypeptide hybrid nanoparticle has great potential for stimuli-responsive drug delivery as well as for monitoring biochemical changes taking place in live cancer and stem cells.

Facile preparation of doxorubicin-loaded upconversion@polydopamine nanoplatforms for simultaneous in vivo multimodality imaging and chemophotothermal synergistic therapy

The development of biosafe nanoplatforms with diagnostic and therapeutic multifunction is extremely demanded for designing cancer theranostic medicines. Here, a facile methodology is developed to construct a multifunctional nanotheranostic that gathers five functions, upconversion luminescence (UCL) imaging, T1-weighted magnetic resonance imaging (MRI), X-ray computed tomography (CT) imaging, photothermal therapy (PTT), and chemotherapy, into one single nanoprobe (named as UCNP@PDA5-PEG-DOX). For generating the UCNP@PDA5-PEG-DOX, a near-infrared light (NIR)-absorbing polydopamine (PDA) shell is directly coated on oleic-acid-capped β-NaGdF4:Yb(3+),Er(3+)@β-NaGdF4 upconverting nanoparticle (UCNP) core for the first time to form monodisperse, ultrastable, and noncytotoxic core-shell-structured nanosphere via water-in-oil microemulsion approach. When combined with 808 nm NIR laser irradiation, the UCNP@PDA5-PEG-DOX shows great synergistic interaction between PTT and the enhanced chemotherapy, resulting in completely eradicated mouse-bearing SW620 tumor without regrowth. In addition, leakage study, hemolysis assay, histology analysis, and blood biochemistry assay unambiguously reveal that the UCNP@PDA5-PEG has inappreciable cytotoxicity and negligible organ toxicity. The results provide explicit strategy for fabricating multifunctional nanoplatforms from the integration of UCNP with NIR-absorbing polymers, important for developing multi-mode nanoprobes for biomedical applications.

Upconversion nanoparticles conjugated with curcumin as a photosensitizer to inhibit methicillin-resistant Staphylococcus aureus in lung under near infrared light

Curcumin has phototoxic effects on bacteria under <450 nm irradiation, but it is unstable in vivo and cannot exert effects on deep tissues. Near infrared light (NIR) is harmless to the body and has stronger penetration than visible light. In order to improve the effects of curcumin, upconversion nanoparticles conjugated with curcumin (UCNPs-curcumin) are designed to upconvert NIR to the excitation wavelength of curcumin. UCNPs-curcumin were synthesized using polyethyleneimine to combine curcumin and UCNPs, based on typical composition of lanthanide nitrates Re(NO)₃ (Y:Yb:Er=78%:20%:2%) linked by ethylenediaminetetraacetic acid in sodium fluoride (NaF) matrix, to upconvert NIR to 432 nm light. The product was characterized by size distribution, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Growth inhibition of methicillin-resistant Staphylococcus aureus (MRSA) was not only measured in vitro but also investigated on MRSA-induced pneumonia in mice. The results showed that curcumin was covered by UCNPs to form stable nanoparticles whose average size was 179.5 nm and zeta potential was −33.7 mV in normal saline. The UCNPs-curcumin produced singlet oxygen, which reaches a stable level after 30 minutes of irradiation, and took effect on MRSA through bacterial cytoplasm leakage. They alleviated MRSA-induced pneumonia and reduced bacterial counts in lungs with 980 nm irradiation (0.5 W/cm²) on chests of mice. It is confirmed that the UCNPs-curcumin in lungs are activated under NIR irradiation and strengthen their antibacterial effects on MRSA. This research provides a new type of NIR photosensitizer, which plays an important role in phototoxic effects of curcumin in deep tissues under NIR.

The intersection of CMOS microsystems and upconversion nanoparticles for luminescence bioimaging and bioassays

Organic fluorophores and quantum dots are ubiquitous as contrast agents for bio-imaging and as labels in bioassays to enable the detection of biological targets and processes. Upconversion nanoparticles (UCNPs) offer a different set of opportunities as labels in bioassays and for bioimaging. UCNPs are excited at near-infrared (NIR) wavelengths where biological molecules are optically transparent, and their luminesce in the visible and ultraviolet (UV) wavelength range is suitable for detection using complementary metal-oxide-semiconductor (CMOS) technology. These nanoparticles provide multiple sharp emission bands, long lifetimes, tunable emission, high photostability, and low cytotoxicity, which render them particularly useful for bio-imaging applications and multiplexed bioassays. This paper surveys several key concepts surrounding upconversion nanoparticles and the systems that detect and process the corresponding luminescence signals. The principle of photon upconversion, tuning of emission wavelengths, UCNP bioassays, and UCNP time-resolved techniques are described. Electronic readout systems for signal detection and processing suitable for UCNP luminescence using CMOS technology are discussed. This includes recent progress in miniaturized detectors, integrated spectral sensing, and high-precision time-domain circuits. Emphasis is placed on the physical attributes of UCNPs that map strongly to the technical features that CMOS devices excel in delivering, exploring the interoperability between the two technologies.

Vascular targeting to the SST2 receptor improves the therapeutic response to near-IR two-photon activated PDT for deep-tissue cancer treatment

BACKGROUND

Broader clinical acceptance of photodynamic therapy is currently hindered by (a) poor depth efficacy, and (b) predisposition towards establishment of an angiogenic environment during the treatment. Improved depth efficacy is being sought by exploiting the NIR tissue transparency window and by photo-activation using two-photon absorption (2PA). Here, we use two-photon activation of PDT sensitizers, untargeted and targeted to SST2 receptors or EGF receptors, to achieve deep tissue treatment.

METHODS

Human tumor lines, positive or negative for SST2r expression were used, as well as murine 3LL cells and bovine aortic endothelial cells. Expression of SST2 receptors on cancer cells and tumor vasculature was evaluated in vitro and frozen xenograft sections. PDT effects on tumor blood flow were followed using in vivo scanning after intravenous injection of FITC conjugated dextran 150K. Dependence of the PDT efficacy on the laser pulse duration was evaluated. Effectiveness of targeting to vascular SST2 receptors was compared to that of EGF receptors, or no targeting.

RESULTS

Tumor vasculature stained for SST2 receptors even in tumors from SST2 receptor negative cell lines, and SST2r targeted PDT led to tumor vascular shutdown. Stretching the pulse from ~120fs to ~3ps led to loss of the PDT efficacy especially at greater depth. PDT targeted to SST2 receptors was much more effective than untargeted PDT or PDT targeted to EGF receptors.

GENERAL SIGNIFICANCE

The use of octreotate to target SST2 receptors expressed on tumor vessels is an excellent approach to PDT with few recurrences and some long term cures.

Recent advances in nanoparticle-based Förster resonance energy transfer for biosensing, molecular imaging and drug release profiling

Förster resonance energy transfer (FRET) may be regarded as a "smart" technology in the design of fluorescence probes for biological sensing and imaging. Recently, a variety of nanoparticles that include quantum dots, gold nanoparticles, polymer, mesoporous silica nanoparticles and upconversion nanoparticles have been employed to modulate FRET. Researchers have developed a number of "visible" and "activatable" FRET probes sensitive to specific changes in the biological environment that are especially attractive from the biomedical point of view. This article reviews recent progress in bringing these nanoparticle-modulated energy transfer schemes to fruition for applications in biosensing, molecular imaging and drug delivery.