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Lee B, Kharal G, Sreenan B, Lin C, Zeng R, Fox CA, Ellison P, Ryan RO, Brett PJ, AuCoin D, Zhu X. Alkaline surface treatment and time-resolved reading of mn-doped nanocrystal signal transducer for enhanced bioassay sensitivity. J Pharm Biomed Anal 2024; 238:115840. [PMID: 37956553 PMCID: PMC10841627 DOI: 10.1016/j.jpba.2023.115840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/26/2023] [Accepted: 10/31/2023] [Indexed: 11/15/2023]
Abstract
Recently, Mn-doped semiconductor nanocrystals (NCs) with high brightness, long lifetimes, and low-energy excitation are emerging for time-resolved luminescence biosensing/imaging. Following our previous work on Mn-doped NCs, in this work we developed poly(styrene-co-maleic anhydride) (PSMA)-encapsulated Mn-doped AgZnInS/ZnS NCs as signal transducers for immunoassay of capsular polysaccharide (CPS), a surface antigen and also a biomarker of Burkholderia pseudomallei which causes a fatal disease called melioidosis. To enhance the assay sensitivity, a surface treatment for PSMA-encapsulated NCs (NC-probes) was performed to promote the presence of carboxyl groups that help conjugate more anti-CPS antibodies to the surface of NC-probes and thus enhance bioassay signals. Meanwhile, time-resolved reading on the luminescence of NC-probes was adopted to minimize the assay background autofluorescence. Both strategies essentially enhance the assay signal-to-background ratio (or equivalently the assay sensitivity) by increasing the signal and decreasing the background, respectively. Through performing and comparing immunoassays with different NC-probes (with and without surface treatment) and different signal reading methods (time-resolved reading and non-time-resolved reading), it was proven that the immunoassay adopting surface-treated NC-probes and time-resolved reading achieved a lower limit-of-detection (LOD) than the ones adopting non-surface-treated NC-probes or non-time-resolved reading. Moreover, the achieved LOD is comparable to the LOD of immunoassay using enzyme horseradish peroxidase as a signal transducer.
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Affiliation(s)
- Bryan Lee
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, USA; Biomedical Engineering Program, University of Nevada, Reno, NV, USA.
| | - Gita Kharal
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, USA; Biomedical Engineering Program, University of Nevada, Reno, NV, USA
| | - Benjamin Sreenan
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, USA; Biomedical Engineering Program, University of Nevada, Reno, NV, USA
| | - Claire Lin
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, USA
| | - Ruosheng Zeng
- School of Physical Science and Technology, Guangxi University, Nanning, China
| | - Colin A Fox
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, USA
| | - Patricia Ellison
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, USA
| | - Robert O Ryan
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, USA
| | - Paul J Brett
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, NV, USA
| | - David AuCoin
- Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, NV, USA
| | - Xiaoshan Zhu
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, USA; Biomedical Engineering Program, University of Nevada, Reno, NV, USA.
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Vijayan S, Umadevi G, Mariappan R, Kumar CS, Karthikeyan A. Effect of metal ion on optical, photoluminescence, morphological, and photocatalytic properties of ZnS nanoparticles. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023:10.1007/s11356-023-27709-4. [PMID: 37269509 DOI: 10.1007/s11356-023-27709-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 05/13/2023] [Indexed: 06/05/2023]
Abstract
The semiconducting materials of pure zinc sulfide (ZnS), 2.5 wt%, 5.0 wt%, 7.5 wt%, and 10 wt% of Ag-doped ZnS nanoparticles were prepared using the sol-gel technique. The prepared nanoparticles were analyzed by powder X-ray diffraction (PXRD), Fourier transformed infrared (FTIR), UV-visible absorption, diffuse reflectance photoluminescence (PL), high-resolution transmission electron microscope (HRTEM), and field emission scanning electron microscope (FESEM) to study the properties of pure ZnS and Ag-doped ZnS nanoparticles (NPs). The Ag-doped ZnS nanoparticles have a polycrystalline nature, which is confirmed by PXRD analysis. The functional groups were identified by the FTIR technique. The bandgap values decrease with increasing Ag concentration compared to pure ZnS NPs. The crystal size lies between 12 and 41 nm for pure ZnS and Ag-doped ZnS NPs. The presence of Zn, S, and Ag elements was confirmed by EDS analysis. Using methylene blue (MB), the photocatalytic activity of pure ZnS and Ag-doped ZnS NPs was performed. The highest degradation efficiency was observed for 7.5 wt% Ag-doped ZnS NPs.
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Affiliation(s)
- Selvaraj Vijayan
- Department of Physics, Govt. Arts College, Coimbatore, Tamilnadu, India
- Department of Physics, MGR College, Hosur, Tamilnadu, India
| | - Ganapathi Umadevi
- Department of Physics, Govt. Arts College, Coimbatore, Tamilnadu, India.
| | - Ramasamy Mariappan
- Department of Physics, Adhiyamaan College of Engineering, Hosur, Tamilnadu, India
| | | | - Anbalagan Karthikeyan
- Department of Physics, Government College of Engineering, Dharmapuri, Tamilnadu, India
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Sreenan B, Lee B, Wan L, Zeng R, Zhao J, Zhu X. Review of Mn-Doped Semiconductor Nanocrystals for Time-Resolved Luminescence Biosensing/Imaging. ACS APPLIED NANO MATERIALS 2022; 5:17413-17435. [PMID: 36874078 PMCID: PMC9980291 DOI: 10.1021/acsanm.2c04337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Colloidal semiconductor nanocrystals (NCs) have been developed for decades and are widely applied in biosensing/imaging. However, their biosensing/imaging applications are mainly based on luminescence-intensity measurement, which suffers from autofluorescence in complex biological samples and thus limits the biosensing/imaging sensitivities. It is expected for these NCs to be further developed to gain luminescence features that can overcome sample autofluorescence. On the other hand, time-resolved luminescence measurement utilizing long-lived-luminescence probes is an efficient technique to eliminate short-lived autofluorescence of samples while recording time-resolved luminescence of the probes for signal measurement after pulsed excitation from a light source. Despite time-resolved measurement being very sensitive, the optical limitations of many of the current long-lived-luminescence probes cause time-resolved measurement to be generally performed in laboratories with bulky and costly instruments. In order to apply highly sensitive time-resolved measurement for in-field or point-of-care (POC) testing, it is essential to develop probes possessing high brightness, low-energy (visible-light) excitation, and long lifetimes of up to milliseconds. Such desired optical features can significantly simplify the design criteria of time-resolved measurement instruments and facilitate the development of low-cost, compact, sensitive instruments for in-field or POC testing. Mn-doped NCs have recently been in rapid development and provide a strategy to solve the challenges faced by both colloidal semiconductor NCs and time-resolved luminescence measurement. In this review, we outline the major achievements in the development of Mn-doped binary and multinary NCs, with emphasis on their synthesis approaches and luminescence mechanisms. Specifically, we demonstrate how researchers approached these obstacles to achieve the aforementioned desired optical properties on the basis of the progressive understanding of Mn emission mechanisms. Afterward, we review representative applications of Mn-doped NCs in time-resolved luminescence biosensing/imaging and present the potential of Mn-doped NCs in advancing time-resolved luminescence biosensing/imaging for in-field or POC testing.
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Affiliation(s)
- Benjamin Sreenan
- Department of Electrical and Biomedical Engineering, University of Nevada-Reno, Reno, Nevada 89557, United States
| | - Bryan Lee
- Department of Electrical and Biomedical Engineering, University of Nevada-Reno, Reno, Nevada 89557, United States
| | - Li Wan
- Department of Physics, Wenzhou University, Wenzhou 325035, China
| | - Ruosheng Zeng
- School of Physical Science and Technology, Guangxi University, Nanning 530004, China
| | - Jialong Zhao
- School of Physical Science and Technology, Guangxi University, Nanning 530004, China
| | - Xiaoshan Zhu
- Department of Electrical and Biomedical Engineering, University of Nevada-Reno, Reno, Nevada 89557, United States
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Multifunctional probe based on modified Ag&Mn:ZnInS QDs for dual-mode fluorescence and magnetic resonance imaging of intracellular glutathione. Anal Chim Acta 2022; 1221:340172. [DOI: 10.1016/j.aca.2022.340172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 07/13/2022] [Indexed: 11/21/2022]
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Hegseth T, Lee B, AuCoin D, Zhu X. A Compact and Sensitive Time-Resolved-Optical-Reader for Bioassay Using Low-Energy Excitable and Long-Lived-Fluorescence Nanolabels. IEEE SENSORS LETTERS 2022; 6:5000304. [PMID: 35496896 PMCID: PMC9052950 DOI: 10.1109/lsens.2022.3159761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Time-resolved fluorescence measurement, a technique utilized to improve sensitivity for fluorescence detection, is becoming more accessible due to the recent development of bright nanolabels with long fluorescence lifetimes and low-energy excitation. Currently, instruments taking advantage of this technique for broader applications (in-field or point-of-care testing) are lagging behind in their development. In this work, a low-cost, compact, and sensitive time-resolved-optical-reader was developed aiming to advance such a technique for wider applications.
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Affiliation(s)
- Tristan Hegseth
- Department of Electrical and Biomedical Engineering, University of Nevada Reno, NV 98557 USA
| | - Bryan Lee
- Department of Electrical and Biomedical Engineering, University of Nevada Reno, NV 98557 USA
| | - David AuCoin
- Department of Microbiology and Immunology, University of Nevada Reno, NV 89557 USA
| | - Xiaoshan Zhu
- Department of Electrical and Biomedical Engineering, University of Nevada Reno, NV 98557 USA
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Optical Properties of Mn-Doped CuGa(In)S-ZnS Nanocrystals (NCs): Effects of Host NC and Mn Concentration. NANOMATERIALS 2022; 12:nano12060994. [PMID: 35335807 PMCID: PMC8956066 DOI: 10.3390/nano12060994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 11/17/2022]
Abstract
Time-gated fluorescence measurement (TGFM) using long-life fluorescence probes is a highly sensitive fluorescence-measurement technology due to the inherently high signal-to-background ratio. Although many probes for TGFM such as luminescent-metal-complex probes and lanthanide-doped nanoparticles are in development, they generally need sophisticated/expensive instruments for biosensing/imaging applications. Probes possessing high brightness, low-energy (visible light) excitation, and long lifetimes up to milliseconds of luminescence, are highly desired in order to simplify the optical and electronic design of time-gated instruments (e.g., adopting non-UV-grade optics or low-speed electronics), lower the instrument complexity and cost, and facilitate broader applications of TGFM. In this work, we developed Mn-doped CuGa(In)S-ZnS nanocrystals (NCs) using simple and standard synthetic steps to achieve all the desired optical features in order to investigate how the optical properties (fluorescence/absorption spectra, brightness, and lifetimes) of the Mn-doped NCs are affected by different host NCs and Mn concentrations in host NCs. With optimal synthetic conditions, a library of Mn-doped NCs was achieved that possessed high brightness (up to 47% quantum yield), low-energy excitation (by 405 nm visible light), and long lifetimes (up to 3.67 ms). Additionally, the time-domain fluorescence characteristics of optimal Mn-doped NCs were measured under pulsed 405 nm laser excitation and bandpass-filter-based emission collection. The measurement results indicate the feasibility of these optimal Mn-doped NCs in TGFM-based biosensing/imaging.
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Lee B, Hegseth T, Song Y, Zhao J, Zhu X. Mn-Doped AgZnInS/ZnS Nanocrystals (NCs): Effects of Zn Etching on the NC Optical Properties. OPTICAL MATERIALS 2022; 123:111941. [PMID: 35068693 PMCID: PMC8775054 DOI: 10.1016/j.optmat.2021.111941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Mn-doped I(II)-III-VI NCs (e.g., Mn-doped AgZnInS/ZnS NCs) possessing low-energy excitation, high brightness and long fluorescence lifetimes have been desired for time-gated fluorescence biosensing/imaging. In this type of NCs, their optical properties are significantly affected by the microscopic interactions between Mn and Mn and between Mn and host NC, the compositions of NCs, and the defects in NCs. On the other hand, it is known that Zn etching to core I(II)-III-VI NCs in NC synthesis can significantly enhance the NC brightness because Zn can exchange surface atoms (e.g., Ag and In) in NCs to minimize NC surface-defects. But for Mn-doped I(II)-III-VI NCs, Zn etching could etch out not only surface-atoms of host NCs (e.g., Ag and In) but also Mn in NCs. As a result, it could significantly affect the NC compositions and the microscopic interactions between Mn and Mn as well as between Mn and host NC, and thus the optical properties of NCs (like lifetime and absorption/emission spectra). Therefore, it is needed to investigate how Zn etching would affect the optical properties of such Mn-doped NCs. In this study, a series of Mn-doped AgZnInS NCs with different Mn doping levels were prepared through nucleation doping, and then Zn etching was applied to etch these core NCs. To identify the effects of Zn etching on NC optical properties, ZnS coating (a different ZnS shelling approach by injecting Zn precursor and S precursor alternately in synthesis) was performed on the same Mn:AgZnInS NCs, and the optical properties of NCs with these two different ZnS shelling approaches were compared. Experimental results showed that under appropriate Mn doping levels in synthesis, Zn etching instead of ZnS coating can produce low-energy excitable NCs with higher QYs and longer lifetimes, which would further facilitate the use of such NCs in time-gated fluorescence measurement. To understand the reasons for the different optical properties under different ZnS shelling approaches, the material characteristics of the prepared NCs were further measured/analyzed and the possible fluorescence mechanisms were discussed.
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Affiliation(s)
- Bryan Lee
- Department of Electrical and Biomedical Engineering,
University of Nevada Reno, NV, USA
- Biomedical Engineering Program, University of Nevada Reno,
NV, USA
| | - Tristan Hegseth
- Department of Electrical and Biomedical Engineering,
University of Nevada Reno, NV, USA
| | - Yusheng Song
- School of Physical Science and Technology, Guangxi
University, Guangxi, China
| | - Jialong Zhao
- School of Physical Science and Technology, Guangxi
University, Guangxi, China
| | - Xiaoshan Zhu
- Department of Electrical and Biomedical Engineering,
University of Nevada Reno, NV, USA
- Biomedical Engineering Program, University of Nevada Reno,
NV, USA
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Gallian B, Zaeimian MS, Hau D, AuCoin D, Zhu X. A Highly Sensitive Time-Gated Fluorescence Immunoassay Platform Using Mn-Doped AgZnInS/ZnS Nanocrystals as Signal Transducers. FRONTIERS IN PHYSICS 2021; 8:625424. [PMID: 33816457 PMCID: PMC8009851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
In this work, a time-gated immunoassay platform using low-energy excitable and fluorescence long-lived Mn:AgZnInS/ZnS nanocrystals as signal transducers was developed and applied to the detection of the capsular polysaccharide (CPS) of Burkholderia pseudomallei, a Gram-negative bacterium that is the causative agent of melioidosis. CPS is a high molecular weight antigen displayed and is shed from the outer membrane of B. pseudomallei. The immunoassay using the time-gated platform presents a limit of detection at around 23 pg/ml when CPS is spiked in human serum.
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Affiliation(s)
- Brandon Gallian
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, United States
- Biomedical Engineering Program, University of Nevada, Reno, NV, United States
| | - Masoumeh Saber Zaeimian
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, United States
- Biomedical Engineering Program, University of Nevada, Reno, NV, United States
| | - Derrick Hau
- Department of Microbiology and Immunology, School of Medicine, University of Nevada, Reno, NV, United States
| | - David AuCoin
- Department of Microbiology and Immunology, School of Medicine, University of Nevada, Reno, NV, United States
| | - Xiaoshan Zhu
- Department of Electrical and Biomedical Engineering, University of Nevada, Reno, NV, United States
- Biomedical Engineering Program, University of Nevada, Reno, NV, United States
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Sakthivel P, Kavi Rasu K, Prasanna Venkatesan GKD, Viloria A. Influence of Ag + and Mn 2+ ions on structural, optical and photoluminescence features of ZnS quantum dots. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2020; 241:118666. [PMID: 32650246 DOI: 10.1016/j.saa.2020.118666] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/21/2020] [Accepted: 06/25/2020] [Indexed: 06/11/2023]
Abstract
The current study deals with the structural, morphological, elemental, optical and photoluminescence behaviors of Ag+, Mn2+ dual doped ZnS quantum dots (QDs). The X-ray diffraction (XRD) and Transmission Electron Microscope (TEM) studies confirmed the cubic structure and size of the crystallites (~2 nm). The Scanning Electron Microscope (SEM) photographs portrayed the surface and morphological structure of prepared samples. Energy dispersive X-ray (EDX) and Fourier Transform Infrared Spectra (FTIR) ensured the presence of Zn, Ag, Mn and, S in the samples as per the anticipated stoichiometry ratio. The UV-visible spectra showed a red shift in optical absorption and band gap gets narrowed due to the incorporation of Ag+ ions. The size effect has overcome the quantum confinement effect in this case. Through photoluminescence (PL) studies, a weak UV emission and strong red wavelength emissions were received and discussed on the basis of sulfur vacancies. This red emission was dealt in terms of d-electrons transition between host and dopant ions.
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Affiliation(s)
- P Sakthivel
- Department of Physics, Faculty of Engineering, Karpagam Academy of Higher Education, Coimbatore 641 021, Tamilnadu, India.
| | - K Kavi Rasu
- Department of Physics, Faculty of Engineering, Karpagam Academy of Higher Education, Coimbatore 641 021, Tamilnadu, India
| | - G K D Prasanna Venkatesan
- Department of Electronics and Communication Engineering, Karpagam Academy of Higher Education, Coimbatore 641 021, Tamilnadu, India
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Khan MS, Shi L, Ullah H, Yang X, Zou B. Ab initio study of optoelectronic and magnetic properties of Mn-doped ZnS with and without vacancy defects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:485706. [PMID: 31483762 DOI: 10.1088/1361-648x/ab3b77] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The effect of vacancy defects on optoelectronic and magnetic properties of Mn-doped ZnS have been systematically investigated using first principle approaches. A single Mn substitution at Zn site induces a spin-polarized ground state in pure ZnS with total magnetization 5 [Formula: see text]. Our results for magnetic coupling show that the coupling between Mn spins in pure Mn doped ZnS is antiferromagnetic under the super-exchange mechanism. The existence of native defects has a great influence on the magnetic ground state of Mn-doped ZnS. In particular, a p -type defect such as Zn vacancy play a crucial role in stabilizing ferromagnetic ground state while n-type defect, such as S vacancy, has no effect on the magnetic ground state i.e. the interaction between two Mn spins with S-vacancy remain antiferromagnetic. Furthermore, optical properties such as dielectric functions, absorption coeffiecients, reflectivity and transmissitivity for Mn doped systems with and without vacancy defect were also studied, and we found that an absorption peak was obtained in the infrared region which is attributed to the defect states introduced by Zn vacancy in the system. In a S-vacancy defect system, the peaks in the near infrared and visible region are due to donor states introduced by S vacancy defect and these peaks are produced by electrons flipping from a spin up state to a spin down state. Finally, we also correlated the magnetic interactions with the d-d optical transition in pure Mn-doped ZnS and found that the d-d transitions during optical absorptions are red shifted and blue shifted in FM and AFM coupled Mn ions pair, which is in good agreement with the experimental observations. This study may help to understand the behavior of optical and magnetic properties of DMS under vacancy defects.
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Affiliation(s)
- Muhammad Sheraz Khan
- Beijing Key Lab of Nanophotonics and Ultrafine Optoelectronic Systems and School of Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
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Gallian B, Dong G, Zhu X. A compact time-gated instrument for QDs with low excitation energy and millisecond fluorescence lifetime as signal reporters, and its detection application. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:104701. [PMCID: PMC6781484 DOI: 10.1063/1.5111147] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 09/16/2019] [Indexed: 06/12/2023]
Abstract
Recently, bright quantum dots (QDs) possessing low energy for excitation and long fluorescence lifetime in milliseconds have been reported. These QDs such as Mn doped I(II)-III-VI nanocrystals are promising for highly sensitive time-gated sensing applications with a portable or small benchtop “personal” instrument because their unique optical properties not only ensure a high signal-to-background ratio in time-gated fluorescence-intensity (TGFI) measurement but also significantly simplify the TGFI measurement instrument design criteria. In this work, following up the research progress on these QDs, we developed a compact TGFI measurement instrument with high sensitivity and cost-effectiveness for these QDs (more specifically Mn:AZIS/ZnS QDs) as signal reporters. We applied the instrument for sensitive detection of copper(ii) ions in highly autofluorescent rum (alcoholic beverage) in a fluorescence quenching assay utilizing these QDs for signal transduction. The results from this work suggest that this instrument together with bright QDs with low-energy for excitation and long fluorescence lifetimes should have potential to not only convert many regular (non-time-gated) QD-based fluorescence assays to time-gated assays for higher sensitivities or lower LODs, but also facilitate the development of highly sensitive assays for in-field or point-of-care testing.
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Affiliation(s)
| | | | - Xiaoshan Zhu
- Author to whom correspondence should be addressed: . Fax: 1-775-784-6627
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