Upconversion: road to El Dorado of the fluorescence world (original) (raw)
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Upconversion nanoparticles: synthesis, surface modification and biological applications
Nanomedicine: Nanotechnology, Biology and Medicine, 2011
New generation fluorophores, also termed upconversion nanoparticles (UCNPs), have the ability to convert near infrared radiations with lower energy into visible radiations with higher energy via a non-linear optical process. Recently, these UCNPs have evolved as alternative fluorescent labels to traditional fluorophores, showing great potential for imaging and biodetection assays in both in vitro and in vivo applications. UCNPs exhibit unique luminescent properties, including high penetration depth into tissues, low background signals, large Stokes shifts, sharp emission bands, and high resistance to photo-bleaching, making UCNPs an attractive alternative source for overcoming current limitations in traditional fluorescent probes. In this review, we discuss the recent progress in the synthesis and surface modification of rare earth doped UCNPs with a specific focus on their biological applications.
Upconversion nanoparticles in biological labeling, imaging, and therapy
Analyst, 2010
Upconversion refers to non-linear optical processes that convert two or more low-energy pump photons to a higher-energy output photon. After being recognized in the mid-1960s, upconversion has attracted significant research interest for its applications in optical devices such as infrared quantum counter detectors and compact solid-state lasers. Over the past decade, upconversion has become more prominent in biological sciences as the preparation of high-quality lanthanide-doped nanoparticles has become increasingly routine. Owing to their small physical dimensions and biocompatibility, upconversion nanoparticles can be easily coupled to proteins or other biological macromolecular systems and used in a variety of assay formats ranging from bio-detection to cancer therapy. In addition, intense visible emission from these nanoparticles under near-infrared excitation, which is less harmful to biological samples and has greater sample penetration depths than conventional ultraviolet excitation, enhances their prospects as luminescent stains in bio-imaging. In this article, we review recent developments in optical biolabeling and bio-imaging involving upconversion nanoparticles, simultaneously bringing to the forefront the desirable characteristics, strengths and weaknesses of these luminescent nanomaterials.
Breakthroughs in medicine and bioimaging with up-conversion nanoparticles
International Journal of Nanomedicine, 2019
Nanomedicine is a medical application of biochemistry incorporated with materials chemistry at the scale of nanometer for the purpose of diagnosis, prevention, and treatment. New models and approaches are typically associated with nanomedicine for precise multifunctional diagnostic systems at molecular level. Hence, employing nanoparticles (NPs) has unveiled new opportunities for efficient therapies and remedy of difficult-to-cure diseases. Among all types of inorganic NPs, lanthanide-doped up-conversion nanoparticles (UCNPs) have shown excellent potential for biomedical applications, especially for multimodal bioimaging including fluorescence and electron microscopy. Association of these visualization techniques plus the capability for transporting biomaterials and drugs make them superior agents in the field of nanomedicine. Accordingly, in this review, we firstly presented a fundamental understanding of physical and optical properties of UCNPs and secondly, we illustrated some of the prominent associations with bioimaging, theranostics, cancer therapy, and optogenetics.
Upconversion fluorescent nanoparticles as a potential tool for in-depth imaging
Nanotechnology, 2011
Upconversion nanoparticles (UCNs) are nanoparticles that are excited in the near infrared (NIR) region with emission in the visible or NIR regions. This makes these particles attractive for use in biological imaging as the NIR light can penetrate the tissue better with minimal absorption/scattering. This paper discusses the study of the depth to which cells can be imaged using these nanoparticles. UCNs with NaYF 4 nanocrystals doped with Yb 3+ , Er 3+ (visible emission)/Yb 3+ , Tm 3+ (NIR emission) were synthesized and modified with silica enabling their dispersion in water and conjugation of biomolecules to their surface. The size of the sample was characterized using transmission electron microscopy and the fluorescence measured using a fluorescence spectrometer at an excitation of 980 nm. Tissue phantoms were prepared by reported methods to mimic skin/muscle tissue and it was observed that the cells could be imaged up to a depth of 3 mm using the NIR emitting UCNs. Further, the depth of detection was evaluated for UCNs targeted to gap junctions formed between cardiac cells.
Near-Infrared-Triggered Upconverting Nanoparticles for Biomedicine Applications
Biomedicines, 2021
Due to the unique properties of lanthanide-doped upconverting nanoparticles (UCNP) under near-infrared (NIR) light, the last decade has shown a sharp progress in their biomedicine applications. Advances in the techniques for polymer, dye, and bio-molecule conjugation on the surface of the nanoparticles has further expanded their dynamic opportunities for optogenetics, oncotherapy and bioimaging. In this account, considering the primary benefits such as the absence of photobleaching, photoblinking, and autofluorescence of UCNPs not only facilitate the construction of accurate, sensitive and multifunctional nanoprobes, but also improve therapeutic and diagnostic results. We introduce, with the basic knowledge of upconversion, unique properties of UCNPs and the mechanisms involved in photon upconversion and discuss how UCNPs can be implemented in biological practices. In this focused review, we categorize the applications of UCNP-based various strategies into the following domains: neuromodulation, immunotherapy, drug delivery, photodynamic and photothermal therapy, bioimaging and biosensing. Herein, we also discuss the current emerging bioapplications with cutting edge nano-/biointerfacing of UCNPs. Finally, this review provides concluding remarks on future opportunities and challenges on clinical translation of UCNPs-based nanotechnology research.
2018
Lanthanide ion doped upconversion nanoparticles (UCNPs) that can convert low-energy infrared photons into high-energy visible and ultraviolet photons, are becoming highly sought-after for advanced biomedical and biophotonics applications. Their unique luminescent properties enable UCNPs to be applied for diagnosis, including biolabeling, biosensing, bioimaging and multiple imaging modality, as well as therapeutic treatments including photothermal and photodynamic therapy, bio-reductive chemotherapy and drug delivery. For the employment of the inorganic nanomaterials into biological environment, it is critical to bridge the gap in between nanoparticles and biomolecules via surface modifications and subsequent functionalisation. This work reviews the various ways to surface modify and functionalise UCNPs so as to impart different functional molecular groups to the UCNPs surfaces for a board range of applications in biomedical areas. We discussed commonly used base functionalities, inc...
The assembly of a photoluminescent nanocomplex based on upconversion nanoparticles
2020
Over the past two decades, developments in the field of nanobiomedicine have come a long way despite the unresolved hindrances. The creation and development of effective theranostic agents based on nanomaterials are urgent needs of modern medicine. Upconversion nanoparticles (UCNP) appear to be the most promising agents for developing theranostics due to their unique optical properties. There has been extensive research on new approaches to obtain stable colloids capable of prolonged circulation in the bloodstream, particularly with bovine serum albumin (BSA). The present work contributes to solving the problem of obtaining stable agents based on UCNP by coating water-soluble UCNP-NOBF4 with a stable protein corona layer of BSA. The assembled nanocomplex is promising for usage as a diagnostic agent and is set for further investigation.
Biofunctionalization of upconversion nanoparticles for intracellular labeling and imaging
OPUS at UTS | Open Publications of UTS Scholars, 2022
Abstract: Lanthanide-doped upconversion nanoparticles (UCNPs) are emerging as the next-generation agent for intracellular fluorescent labeling and imaging. To label the subcellular structures using UCNPs, vast opportunities and immense potential lay in their surface functionalization and subsequent bioconjugations. The surface stability and reactivity of UCNPs determine their specific interactions with target molecules, and it enables control of the degree of non-specific bindings to the surroundings. The targetability of UCNPs could be optimized by molecule-specific moiety via conjugating to the grafted polymers on the surface of nanoparticles. As the surface of UCNPs is highly positively charged, due to the exposed lanthanide ions at the lattice termination sites, the nanocrystal surfaces allow the tethering of polymers with negative charges. Therefore, the design and tethering polymers is the key factor in producing functional inorganic nanoparticles with a desirable surface property. Throughout the Ph.D. study, a new understanding of the roles of polymers in functionalizing UCNPs has been achieved by systematic investigations of multiple RAFT copolymers. RAFT copolymers play a crucial role in controlling surface features and reactivities of UCNPs by manipulating physicochemical properties. The UCNP's surface coupling efficiency could be enhanced using highly reactive triblock RAFT copolymers containing methacrylic acid (MAA). Through increasing surface carboxylic acids density and by enabling an extended surface reactive site, advances in reactivity and dispersibility of UCNPs could be achieved. The surface graft copolymer composition determines the amphiphilicity, dispersibility, and stability of UCNPs. The concept of double copolymer surface grafting using stepwise co-grafting has been implemented to attain high control of surface composition. Efficient immobilization of antibodies and peptides to UCNPs enables the targeting and imaging of single biomolecules and intracellular structures. The performed intracellular labeling and imaging experiments prove that the functionalized UCNPs are suitable for detailed intracellular labeling and investigations. This thesis, therefore, contributes to developing the next-generation super-resolution probes for single-molecule tracking and live cell imaging applications. Moreover, besides visualization of structural features and dynamics of molecular-level phenomena, the functionalized nanoparticles could be implemented as a nano-theranostic tool for personalized nanomedicine.
Quantitative Imaging of Single Upconversion Nanoparticles in Biological Tissue
PLoS ONE, 2013
The unique luminescent properties of new-generation synthetic nanomaterials, upconversion nanoparticles (UCNPs), enabled high-contrast optical biomedical imaging by suppressing the crowded background of biological tissue autofluorescence and evading high tissue absorption. This raised high expectations on the UCNP utilities for intracellular and deep tissue imaging, such as whole animal imaging. At the same time, the critical nonlinear dependence of the UCNP luminescence on the excitation intensity results in dramatic signal reduction at (,1 cm) depth in biological tissue. Here, we report on the experimental and theoretical investigation of this trade-off aiming at the identification of optimal application niches of UCNPs e.g. biological liquids and subsurface tissue layers. As an example of such applications, we report on single UCNP imaging through a layer of hemolyzed blood. To extend this result towards in vivo applications, we quantified the optical properties of single UCNPs and theoretically analyzed the prospects of single-particle detectability in live scattering and absorbing bio-tissue using a human skin model. The model predicts that a single 70-nm UCNP would be detectable at skin depths up to 400 mm, unlike a hardly detectable single fluorescent (fluorescein) dye molecule. UCNP-assisted imaging in the ballistic regime thus allows for excellent applications niches, where high sensitivity is the key requirement.
Morphological evolution of upconversion nanoparticles and their biomedical signal generation
Scientific Reports, 2018
Advancements in the fabrication of upconversion nanoparticles (UCNPs) for synthetic control can enable a broad range of applications in biomedical systems. Herein, we experimentally verified the role of the hydrothermal reaction (HR) time in the synthesis of NaYF4:20%Yb3+/3%Er3+ UCNPs on their morphological evolution and phase transformation at different temperatures. Characterizations of the as-prepared UCNPs were conducted using X-ray diffraction (XRD), electron microscopy and spectroscopy, and thermogravimetric and upconversion (UC) luminescence analysis. We demonstrated that determining the optimal HR time, also referred to here as the threshold time, can produce particles with good homogeneity, hexagonal phase, and UC luminescence efficiency. Subsequently, the polymer coated UCNPs maintained their original particle size distribution and luminescence properties, and showed improved dispersibility in a variety of solvents, cellular nontoxicity, in vitro bioimaging, and biocompati...