ORCID Profile
0000-0002-9930-1676
Current Organisation
University of Technology Sydney
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Medical Biotechnology | Medical Biotechnology Diagnostics (incl. Biosensors) | Analytical Biochemistry | Nanobiotechnology |
Expanding Knowledge in the Medical and Health Sciences | Expanding Knowledge in Technology
Publisher: Springer Science and Business Media LLC
Date: 05-04-2017
Publisher: American Chemical Society (ACS)
Date: 09-01-2017
DOI: 10.1021/ACS.ANALCHEM.6B03223
Abstract: Measurement of changes of pH at various intracellular compartments has potential to solve questions concerning the processing of endocytosed material, regulation of the acidification process, and also acidification of vesicles destined for exocytosis. To monitor these events, the nanosized optical pH probes need to provide ratiometric signals in the optically transparent biological window, target to all relevant intracellular compartments, and to facilitate imaging at subcellular resolution without interference from the biological matrix. To meet these criteria we sensitize the surface conjugated pH sensitive indicator via an upconversion process utilizing an energy transfer from the nanoparticle to the indicator. Live cells were imaged with a scanning confocal microscope equipped with a low-energy 980 nm laser excitation, which facilitated high resolution and penetration depth into the specimen, and low phototoxicity needed for long-term imaging. Our upconversion nanoparticle resonance energy transfer based sensor with polyethylenimine-coating provides high colloidal stability, enhanced cellular uptake, and distribution across cellular compartments. This distribution was modulated with membrane integrity perturbing treatment that resulted into total loss of lysosomal compartments and a dramatic pH shift of endosomal compartments. These nanoprobes are well suited for detection of pH changes in in vitro models with high biological background fluorescence and in in vivo applications, e.g., for the bioimaging of small animal models.
Publisher: Public Library of Science (PLoS)
Date: 13-12-2017
Publisher: Public Library of Science (PLoS)
Date: 27-11-2017
Publisher: American Chemical Society (ACS)
Date: 20-03-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B901299K
Abstract: Upconverting phosphors (UCPs) are lanthanide-doped sub-micrometer-sized particles, which produce multiple narrow and well-separated anti-Stokes emission bands at visible wavelengths under infrared excitation (980 nm). The advantageous features of UCPs were utilized to construct a dual-parameter, homogeneous sandwich hybridization assay based on a UCP donor and lanthanide resonance energy transfer (LRET). UCPs with two emission bands (540 nm and 653 nm) were exploited together with two appropriate fluorophores as acceptors. The energy transfer excited emissions of the acceptors were measured at 600 nm and 740 nm without any significant interference from each other. The autofluorescence limitation associated with conventional fluorescence was totally avoided as the measurements were carried out at shorter wavelength relative to the excitation. In the sandwich hybridization assay two different single-stranded target-oligonucleotide sequences were detected simultaneously and quantitatively with a dynamic range from 0.03 to 0.4 pmol (corresponding 0.35-5.4 nM). The UCPs enable multiplexed homogeneous LRET-based assay requiring only a single excitation wavelength, which simplifies the detection and extends the applicability of upconversion in bioanalytical measurements.
Publisher: Elsevier BV
Date: 2016
Abstract: Many quantitative and semiquantitative lateral flow (LF) assays have been introduced for clinical analytes such as biomarkers for cancer or acute myocardial infarction (AMI). Various detection technologies involving quantitative analyzing devices have been reported to have sufficient analytical sensitivity and quantification capability for clinical point-of-care tests. Fluorescence-based detection technologies such as quantum dots, Eu(III) nanoparticles, and photon-upconverting nanoparticles (UCNPs) have been introduced as promising solutions for point-of-care devices because of their high detectability by optical sensors. Lateral flow assays can be used for various s le types, e.g., urine, saliva, cerebrospinal fluid, and blood. This study focuses on the properties of serum and plasma because of their relevance in cancer and AMI diagnostics. The limit of detection was compared in LF assays having Eu(III) nanoparticles or UCNPs as reporters and the antibody configurations for two different analytes (prostate-specific antigen and cardiac troponin I (cTnI)). The results indicate a significant effect of anticoagulants in venipuncture tubes. The s les in K3EDTA tubes resulted in significant interference by decreased reporter particle mobility, and thus the limit of detection was up to eightfold less sensitive compared to serum s les. Despite the matrix interference in the cTnI assay with UCNP reporters, limits of detection of 41 ng/L with serum and 66 ng/L with the Li-heparin s le were obtained.
Publisher: American Chemical Society (ACS)
Date: 05-02-2019
Abstract: Dysprosium(III) ions are the third most luminescent lanthanide(III) ions. Dy(III) is used as dopant in optical fibers and as shift reagent in NMR imaging and is the element at the forefront of research in single-molecule magnets. Nonetheless, the excited state manifold of the dysprosium(III) ion is not fully mapped and the nature of the emitting state has not been unequivocally assigned. In the work reported here, the photophysical properties of dysprosium(III) triflate dissolved in H
Publisher: Wiley
Date: 18-07-2018
Abstract: Lanthanide(III) ions bind to the glycocalyx of Chinese Hamster Ovary (CHO) cells and give rise to a unique luminescent fingerprint. Following direct excitation of terbium(III) and europium(III) ions in the visible part of the spectrum, we are able to collect emission spectra pixel-by-pixel in images of CHO cells. Following data analysis that removes the background signal, the fine structure of the europium(III) luminescence indicate that the lanthanide(III) ions are bound to a single structure of the CHO cell glycocalyx. This was deduced from the fact that the structure-sensitive emission spectrum of europium is unchanged throughout the investigated s les.
Publisher: Wiley
Date: 18-09-2017
Publisher: Wiley
Date: 07-06-2018
Publisher: Wiley
Date: 14-08-2018
Publisher: Wiley
Date: 17-02-2017
Abstract: The luminescence intensity ratio (LIR) of the green emissions of the near-infrared excited NaYF
Publisher: IOP Publishing
Date: 21-09-2018
Abstract: Upon direct excitation with green light (522 nm), Er
Publisher: American Chemical Society (ACS)
Date: 16-01-2019
Abstract: Counterfeit consumer products, electronic components, and medicines generate heavy economic losses, pose a massive security risk, and endanger human lives on a daily basis. Combatting counterfeits requires incorporation of uncopiable or unclonable features in each and every product. By exploiting the inherent randomness of stochastic processes, an optical authentication system based on physical unclonable functions (PUFs) was developed. The system relies on placing unique tags-PUF-tags-on the in idual products. The tags can be created using commercial printing and coating technologies using several combinations of carrier materials and taggant materials. The authentication system was found to be independent of how contrast was generated, and ex les of PUF-tags based on scattering, absorption, and luminescence were made. A version of the authentication using the combination of scattering-based PUF-tags and a smartphone-based reader was validated on a s le size of 9720 unique codes. With zero false positives in 29 154 matches, an encoding capacity of 2.5 × 10
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4NR00461B
Abstract: Ratiometric referenced luminescent pH nanosensors based on an upconversion resonance energy transfer (UC-RET) process enable imaging applications with NIR excitation.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-01-2018
Abstract: Random patterns of lanthanide(III) ion–doped zeolites were used to create a t er-proof optical authentication system.
Publisher: Springer Science and Business Media LLC
Date: 09-08-2013
Publisher: Elsevier BV
Date: 05-2012
DOI: 10.1016/J.ACA.2012.03.010
Abstract: Caspase proteases are key mediators in apoptosis and thus of great interest in pharmaceutical industry. Enzyme-activity assays are commonly employed in the screening of protease inhibitors that are potential drug candidates. Conventional homogeneous fluorescence-based assays are susceptible to autofluorescence originating from biological material. This background autofluorescence can be eliminated by using upconverting phosphors (UCPs) that emit visible light upon excitation at near-infrared. In the assay energy was transferred from a UCP-donor to a conventional fluorophore acceptor that resided at one end of a caspase-3-specific substrate peptide. Attached to the other end was a quencher molecule that was used to attenuate the acceptor emission through intramolecular energy transfer in an intact peptide. In non-inhibitory conditions the enzyme reaction separated the fluorophore from the quencher and the emission of the fluorophore was recovered. The method was applied for the detection and characterization of a known caspase-3 inhibitor Z-DEVD-FMK, and the assay gave IC(50) values of approximately 13 nM for this inhibitor. We have demonstrated the applicability of UCPs on a fluorescence-quenching-based homogeneous enzyme-activity assay for the detection of caspase-3 inhibitors. The use of near-infrared excitable UCPs enables inexpensive instrumentation and total elimination of autofluorescence, while the use of an internally quenched substrate molecule diminishes the background resulting from radiatively excited acceptor molecules. The reduction of autofluorescence and radiative background result in high signal-to-background ratios (ratios of approximately 100 were obtained). By further utilizing assay miniaturization and signal enhancement in a white microtitration plate, a significant reduction in the reagent consumption can be achieved rendering the assay applicable for high-throughput screening.
Publisher: Springer Science and Business Media LLC
Date: 02-02-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5NR02100F
Abstract: We have studied the mechanisms of water-based quenching of the upconversion photoluminescence of upconverting nanophosphors (UCNPs) via luminescence decay measurements for a better understanding of the non-radiative deactivation pathways responsible for the relatively low upconversion luminescence efficiency in aqueous solutions. This included both upconversion luminescence measurements and the direct excitation of emissive energy states of Er(3+) and Yb(3+) dopants in NaYF4:Yb(3+),Er(3+) UCNPs by measuring the decays at 550 and 655 nm upon 380 nm excitation and at 980 nm upon 930 nm excitation, respectively. The luminescence intensities and decays were measured from both bare and silanized NaYF4:Yb(3+),Er(3+) and NaYF4:Yb(3+),Tm(3+) UCNPs in H2O and D2O. The measurements revealed up to 99.9% quenching of the upconversion photoluminescence intensity of both Er(3+) and Tm(3+) doped bare nanophosphors by water. Instead of the multiphonon relaxation of excited energy levels of the activators, the main mechanism of quenching was found to be the multiphonon deactivation of the Yb(3+) sensitizer ion caused by OH-vibrations on the surface of the nanophosphor. Due to the nonlinear nature of upconversion, the quenching of Yb(3+) has a higher order effect on the upconversion emission intensity with the efficient Yb-Yb energy migration in the ∼35 nm nanocrystals making the whole nanophosphor volume susceptible to surface quenching effects. The study underlines the need of efficient surface passivation for the use of UCNPs as labels in bioanalytical applications performed in aqueous solutions.
Publisher: American Chemical Society (ACS)
Date: 14-01-2015
DOI: 10.1021/AC503691M
Abstract: Red blood cell folate is measured for folate deficiency diagnosis, because it reflects the long-term folate level in tissues, whereas serum folate only represents the dietary intake. Direct homogeneous assay from whole blood would be ideal but conventional fluorescence techniques in blood suffer from high background and strong absorption of light at ultraviolet and visible wavelengths. In this study, a new photon upconversion-based homogeneous assay for whole blood folate is introduced based on resonance energy transfer from upconverting nanophosphor donor coated with folate binding protein to a near-infrared fluorescent acceptor dye conjugated to folate analogue. The sensitized acceptor emission is measured at 740 nm upon 980 nm excitation. Thus, optically transparent wavelengths are utilized for both donor excitation and sensitized acceptor emission to minimize the s le absorption, and anti-Stokes detection completely eliminates the Stokes-shifted autofluorescence. The IC50 value of the assay was 6.0 nM and the limit of detection (LOD) was 1 nM. The measurable concentration range was 2 orders of magnitude between 1.0-100 nM, corresponding to 40-4000 nM folate in the whole blood s le. Recoveries of added folic acid were 112%-114%. A good correlation was found when compared to a competitive heterogeneous assay based on the DELFIA-technology. The introduced assay provides a simple and fast method for whole blood folate measurement.
Start Date: 2022
End Date: 2022
Amount: $383,982.00
Funder: Australian Research Council
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