Chen, Y., Duong, H.T.T., Wen, S., Mi, C., Zhou, Y., Shimoni, O., Valenzuela, S.M. & Jin, D. 2018, 'Exonuclease III-Assisted Upconversion Resonance Energy Transfer in a Wash-Free Suspension DNA Assay.', Analytical Chemistry, vol. 90, no. 1, pp. 663-668.View/Download from: UTS OPUS or Publisher's site
Sensitivity is the key in optical detection of low-abundant analytes, such as circulating RNA or DNA. The enzyme Exonuclease III (Exo III) is a useful tool in this regard; its ability to recycle target DNA molecules results in markedly improved detection sensitivity. Lower limits of detection may be further achieved if the detection background of autofluorescence can be removed. Here we report an ultrasensitive and specific method to quantify trace amounts of DNA analytes in a wash-free suspension assay. In the presence of target DNA, the Exo III recycles the target DNA by selectively digesting the dye-tagged sequence-matched probe DNA strand only, so that the amount of free dye removed from the probe DNA is proportional to the number of target DNAs. Remaining intact probe DNAs are then bound onto upconversion nanoparticles (energy donor), which allows for upconversion luminescence resonance energy transfer (LRET) that can be used to quantify the difference between the free dye and tagged dye (energy acceptor). This scheme simply avoids both autofluorescence under infrared excitation and many tedious washing steps, as the free dye molecules are physically located away from the nanoparticle surface, and as such they remain "dark" in suspension. Compared to alternative approaches requiring enzyme-assisted amplification on the nanoparticle surface, introduction of probe DNAs onto nanoparticles only after DNA hybridization and signal amplification steps effectively avoids steric hindrance. Via this approach, we have achieved a detection limit of 15 pM in LRET assays of human immunodeficiency viral DNA.
Duong, H.T.T., Chen, Y., Tawfik, S.A., Wen, S., Parviz, M., Shimoni, O. & Ab, D.J. 2018, 'Systematic investigation of functional ligands for colloidal stable upconversion nanoparticles†', RSC Advances, vol. 8, no. 9, pp. 4842-4849.View/Download from: Publisher's site
© The Royal Society of Chemistry 2018. Despite intense efforts on surface functionalization to generate hydrophilic upconversion nanoparticles (UCNPs), long-term colloidal stability in physiological buffers remains a major concern. Here we quantitatively investigate the competitive adsorption of phosphate, carboxylic acid and sulphonic acid onto the surface of UCNPs and study their binding strength to identify the best conjugation strategy. To achieve this, we designed and synthesized three di-block copolymers composed of poly(ethylene glycol) methyl ether acrylate and a polymer block bearing phosphate, carboxylic or sulphonic acid anchoring groups prepared by an advanced polymerization technique, Reversible Addition Fragmentation Chain Transfer (RAFT). Analytical tools provide the evidence that phosphate ligands completely replaced all the oleic acid capping molecules on the surface of the UCNPs compared with incomplete ligand exchange by carboxylic and sulphonic acid groups. Meanwhile, simulated quantitative adsorption energy measurements confirmed that among the three functional groups, the calculated adsorption strength for phosphate anchoring ligands is higher which is in good agreement with experimental results regarding the best colloidal stability, especially in phosphate buffer solution. This finding suggests that polymers with multiple anchoring negatively charged phosphate moieties provide excellent colloidal stability for lanthanide ion-doped luminescent nanoparticles for various potential applications.
He, H., Howard, C.B., Chen, Y., Wen, S., Lin, G., Zhou, J., Thurecht, K.J. & Jin, D. 2018, 'Bispecific Antibody-Functionalized Upconversion Nanoprobe.', Analytical chemistry, vol. 90, no. 5, pp. 3024-3029.View/Download from: UTS OPUS or Publisher's site
Upconversion nanoparticles (UCNPs) are new optical probes for biological applications. For specific biomolecular recognition to be realized for diagnosis and imaging, the key lies in developing a stable and easy-to-use bioconjugation method for antibody modification. Current methods are not yet satisfactory regarding conjugation time, stability, and binding efficiency. Here, we report a facile and high-yield approach based on a bispecific antibody (BsAb) free of chemical reaction steps. One end of the BsAb is designed to recognize methoxy polyethylene glycol-coated UCNPs, and the other end of the BsAb is designed to recognize the cancer antigen biomarker. Through simple vortexing, BsAb-UCNP nanoprobes form within 30 min and show higher (up to 54%) association to the target than that of the traditional UCNP nanoprobes in the ELISA-like assay. We further demonstrate its successful binding to the cancer cells with high efficiency and specificity for background-free fluorescence imaging under near-infrared excitation. This method suggests a general approach broadly suitable for functionalizing a range of nanoparticles to specifically target biomolecules.
Ren, W., Wen, S., Tawfik, S.A., Su, Q.P., Lin, G., Ju, L.A., Ford, M.J., Ghodke, H., van Oijen, A.M. & Jin, D. 2018, 'Anisotropic functionalization of upconversion nanoparticles.', Chemical science, vol. 9, no. 18, pp. 4352-4358.View/Download from: UTS OPUS or Publisher's site
Despite significant advances toward accurate tuning of the size and shape of colloidal nanoparticles, the precise control of the surface chemistry thereof remains a grand challenge. It is desirable to conjugate functional bio-molecules onto the selected facets of nanoparticles owing to the versatile capabilities rendered by the molecules. We report here facet-selective conjugation of DNA molecules onto upconversion nanoparticles via ligand competition reaction. Different binding strengths of phosphodiester bonds and phosphate groups on DNA and the surfactant molecules allow one to create heterogeneous bio-chemistry surface for upconversion nanoparticles. The tailored surface properties lead to the formation of distinct self-assembly structures. Our findings provide insight into the interactions between biomolecules and nanoparticles, unveiling the potential of using nanoparticles as fundamental building blocks for creating self-assembled nano-architectures.
Wang, F., Wen, S., He, H., Wang, B., Zhou, Z., Shimoni, O. & Jin, D. 2018, 'Microscopic inspection and tracking of single upconversion nanoparticles in living cells', Light: Science and Applications, vol. 7, no. 4.View/Download from: Publisher's site
© 2018 The Author(s). Nanoparticles have become new tools for cell biology imaging, sub-cellular sensing, super-resolution imaging, and drug delivery. Long-term 3D tracking of nanoparticles and their intracellular motions have advanced the understanding of endocytosis and exocytosis as well as of active transport processes. The sophisticated operation of correlative optical-electron microscopy and scientific-grade cameras is often used to study intercellular processes. Nonetheless, most of these studies are still limited by the insufficient sensitivity for separating a single nanoparticle from a cluster of nanoparticles or their aggregates8. Here we report that our eyes can track a single fluorescent nanoparticle that emits over 4000 photons per 100 milliseconds under a simple microscope setup. By tracking a single nanoparticle with high temporal, spectral and spatial resolution, we show the measurement of the local viscosity of the intracellular environment. Moreover, beyond the colour domain and 3D position, we introduce excitation power density as the fifth dimension for our eyes to simultaneously discriminate multiple sets of single nanoparticles.
Zhou, J., Wen, S., Liao, J., Clarke, C., Tawfik, S.A., Ren, W., Mi, C., Wang, F. & Jin, D. 2018, 'Activation of the surface dark-layer to enhance upconversion in a thermal field', Nature Photonics, vol. 12, no. 3, pp. 154-158.View/Download from: Publisher's site
© 2018 The Author(s). Thermal quenching, in which light emission experiences a loss with increasing temperature, broadly limits luminescent efficiency at higher temperature in optical materials, such as lighting phosphors 1-3 and fluorescent probes 4-6 . Thermal quenching is commonly caused by the increased activity of phonons that leverages the non-radiative relaxation pathways. Here, we report a kind of heat-favourable phonons existing at the surface of lanthanide-doped upconversion nanomaterials to combat thermal quenching. It favours energy transfer from sensitizers to activators to pump up the intermediate excited-state upconversion process. We identify that the oxygen moiety chelating Yb 3+ ions, [YbO], is the key underpinning this enhancement. We demonstrate an approximately 2,000-fold enhancement in blue emission for 9.7 nm Yb 3+ -Tm 3+ co-doped nanoparticles at 453 K. This strategy not only provides a powerful solution to illuminate the dark layer of ultra-small upconversion nanoparticles, but also suggests a new pathway to build high-efficiency upconversion systems.
Liu, Y., Lu, Y., Yang, X., Zheng, X., Wen, S., Wang, F., Vidal, X., Zhao, J., Liu, D., Zhou, Z., Ma, C., Zhou, J., Piper, J.A., Xi, P. & Jin, D. 2017, 'Amplified stimulated emission in upconversion nanoparticles for super-resolution nanoscopy', Nature, vol. 543, no. 7644, pp. 229-233.View/Download from: UTS OPUS or Publisher's site
Lanthanide-doped glasses and crystals are attractive for laser applications because the metastable energy levels of the trivalent lanthanide ions facilitate the establishment of population inversion and amplified stimulated emission at relatively low pump power1,2,3. At the nanometre scale, lanthanide-doped upconversion nanoparticles (UCNPs) can now be made with precisely controlled phase, dimension and doping level4,5. When excited in the near-infrared, these UCNPs emit stable, bright visible luminescence at a variety of selectable wavelengths6,7,8,9, with single-nanoparticle sensitivity10,11,12,13, which makes them suitable for advanced luminescence microscopy applications. Here we show that UCNPs doped with high concentrations of thulium ions (Tm3+), excited at a wavelength of 980nanometres, can readily establish a population inversion on their intermediate metastable 3H4 level: the reduced inter-emitter distance at high Tm3+ doping concentration leads to intense cross-relaxation, inducing a photon-avalanche-like effect that rapidly populates the metastable 3H4 level, resulting in population inversion relative to the 3H6 ground level within a single nanoparticle. As a result, illumination by a laser at 808nanometres, matching the upconversion band of the 3H43H6 transition, can trigger amplified stimulated emission to discharge the 3H4 intermediate level, so that the upconversion pathway to generate blue luminescence can be optically inhibited. We harness these properties to realize low-power super-resolution stimulated emission depletion (STED) microscopy and achieve nanometre-scale optical resolution (nanoscopy), imaging single UCNPs; the resolution is 28nanometres, that is, 1/36th of the wavelength. These engineered nanocrystals offer saturation intensity two orders of magnitude lower than those of fluorescent probes currently employed in stimulated emission depletion microscopy, suggesting a new way of alleviating the square-root law that typically li...
Wang, L., Ren, L., Mitchell, D., Casillas-Garcia, G., Ren, W., Ma, C., Xu, X.X., Wen, S., Wang, F., Zhou, J., Xu, X., Hao, W., Dou, S.X. & Du, Y. 2017, 'Enhanced energy transfer in heterogeneous nanocrystals for near infrared upconversion photocurrent generation.', Nanoscale, vol. 9, no. 47, pp. 18661-18667.View/Download from: UTS OPUS or Publisher's site
The key to produce inorganic heterogeneous nanostructures, and to integrate multiple functionalities, is to enhance or at least retain the functionalities of different components of materials. However, this ideal scenario is often deteriorated at the interface of the heterogeneous nanostructures due to lattice mismatches, resulting in downgraded performance in most hybrid nanomaterials. Here, we report that there is a narrow window in controlling temperature in a Lewis acid-base reaction process to facilitate epitaxial alignment during the synthesis of hybrid nanomaterials. We demonstrate a perfectly fused NaYF4:Yb,Tm@ZnO heterogeneous nanostructure, in which the semiconductor ZnO shell can be epitaxially grown onto lanthanide-doped upconversion nanoparticles. By achieving a matched crystal lattice, the interface defects and crystalline grain boundaries are minimized to enable more efficient energy transfer from the upconversion nanoparticles to the semiconductor, resulting in both enhanced upconversion luminescence intensity and superior photoelectrochemical properties. This strategy provides an outstanding approach to endow lanthanide-doped upconversion nanoparticles with versatile properties.
Cong, Y., Shi, B., Lu, Y., Wen, S., Chung, R. & Jin, D. 2016, 'One-step Conjugation of Glycyrrhetinic Acid to Cationic Polymers for High-performance Gene Delivery to Cultured Liver Cell.', Scientific Reports, vol. 6, pp. 1-11.View/Download from: UTS OPUS or Publisher's site
Gene therapies represent a promising therapeutic route for liver cancers, but major challenges remain in the design of safe and efficient gene-targeting delivery systems. For example, cationic polymers show good transfection efficiency as gene carriers, but are hindered by cytotoxicity and non-specific targeting. Here we report a versatile method of one-step conjugation of glycyrrhetinic acid (GA) to reduce cytotoxicity and improve the cultured liver cell -targeting capability of cationic polymers. We have explored a series of cationic polymer derivatives by coupling different ratios of GA to polypropylenimine (PPI) dendrimer. These new gene carriers (GA-PPI dendrimer) were systematically characterized by UV-vis,(1)H NMR titration, electron microscopy, zeta potential, dynamic light-scattering, gel electrophoresis, confocal microscopy and flow cytometry. We demonstrate that GA-PPI dendrimers can efficiently load and protect pDNA, via formation of nanostructured GA-PPI/pDNA polyplexes. With optimal GA substitution degree (6.31%), GA-PPI dendrimers deliver higher liver cell transfection efficiency (43.5% vs 22.3%) and lower cytotoxicity (94.3% vs 62.5%, cell viability) than the commercial bench-mark DNA carrier bPEI (25 kDa) with cultured liver model cells (HepG2). There results suggest that our new GA-PPI dendrimer are a promising candidate gene carrier for targeted liver cancer therapy.
Liu, D., Xu, X., Du, Y., Qin, X., Zhang, Y., Ma, C., Wen, S., Ren, W., Goldys, E.M., Piper, J.A., Dou, S., Liu, X. & Jin, D. 2016, 'Three-dimensional controlled growth of monodisperse sub-50 nm heterogeneous nanocrystals', Nature Communications, vol. 7, pp. 1-8.View/Download from: UTS OPUS or Publisher's site
The ultimate frontier in nanomaterials engineering is to realize their composition control with atomic scale precision to enable fabrication of nanoparticles with desirable size, shape and surface properties. Such control becomes even more useful when growing hybrid nanocrystals designed to integrate multiple functionalities. Here we report achieving such degree of control in a family of rare-earth-doped nanomaterials. We experimentally verify the co-existence and different roles of oleate anions (OA) and molecules (OAH) in the crystal formation. We identify that the control over the ratio of OA to OAH can be used to directionally inhibit, promote or etch the crystallographic facets of the nanoparticles. This control enables selective grafting of shells with complex morphologies grown over nanocrystal cores, thus allowing the fabrication of a diverse library of monodisperse sub-50nm nanoparticles. With such programmable additive and subtractive engineering a variety of three-dimensional shapes can be implemented using a bottom–up scalable approach.
Ma, C., Xu, X., Wang, F., Zhou, Z., Wen, S., Liu, D., Fang, J., Lang, C.I. & Jin, D. 2016, 'Probing the Interior Crystal Quality in the Development of More Efficient and Smaller Upconversion Nanoparticles', Journal of Physical Chemistry Letters, vol. 7, pp. 3252-3258.View/Download from: UTS OPUS or Publisher's site
Optical biomedical imaging using luminescent nanoparticles as contrast agents prefers small size, as they can be used at high dosages and efficiently cleared from body. Reducing nanoparticle size is critical for the stability and specificity for the fluorescence nanoparticles probes for in vitro diagnostics and subcellular imaging. The development of smaller and brighter upconversion nanoparticles (UCNPs) is accordingly a goal for complex imaging in bioenvironments. At present, however, small UCNPs are reported to exhibit less emission intensity due to increased surface deactivation and decreased number of dopants. Here we show that smaller and more efficient UCNPs can be made by improving the interior crystal quality via controlling heating rate during synthesis. We further developed a unique quantitative method for optical characterizations on the single UCNPs with varied sizes and the corresponding shell passivated UCNPs, confirming that the internal crystal quality dominates the relative emission efficiency of the UCNPs.
Wen, S., Li, D., Liu, D., Xu, X., Du, Y., Mitchell, D.R.G., Shi, B., Shi, X. & Jin, D. 2016, 'Seed mediated one-pot growth of versatile heterogeneous upconversion nanocrystals for multimodal bioimaging', Proceedings of SPIE - The International Society for Optical Engineering, International Society for Optical Engineering, SPIE Digital Library, Adelaide, South Australia, Australia.View/Download from: UTS OPUS or Publisher's site
© 2016 SPIE.The rapid development of a variety of molecular contrast agents makes the multimodality bioimaging highly attractive towards higher resolution, more sensitive, informative diagnosis. The key lies in the development of facile material synthesis that allows the integration of multiple contrast agents, ideally in a way that each of the components should be logically assembled to maximize their performances. Here, we report the one-pot programmable growth of multifunctional heterogeneous nanocrystal with tunable size, shape, composition, and properties. We demonstrated a facile one-pot hot-injection method to enable the highly selectively controlled growth of different sodium lanthanide fluoride nanomaterials in either longitudinal or transversal directions with atomic scale precision. This technique allows the upconversion luminescence signal, MRI signal and x-ray signal logically integrated and optimized within one single versatile nanoplatform for multimode bioimaging. These findings suggest that the facile strategy developed here have the promising to get the desired heterogeneous nanocrystals as an all-in-one contrast agent for integrated and self-correlative multimodal bioimaging.