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Ekman M, Salminen T, Raiko K, Soukka T, Gidwani K, Martiskainen I. Spectrally separated dual-label upconversion luminescence lateral flow assay for cancer-specific STn-glycosylation in CA125 and CA15-3. Anal Bioanal Chem 2024; 416:3251-3260. [PMID: 38584178 DOI: 10.1007/s00216-024-05275-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 03/06/2024] [Accepted: 03/26/2024] [Indexed: 04/09/2024]
Abstract
Multiplexed lateral flow assays (LFAs) offer efficient on-site testing by simultaneously detecting multiple biomarkers from a single sample, reducing costs. In cancer diagnostics, where biomarkers can lack specificity, multiparameter detection provides more information at the point-of-care. Our research focuses on epithelial ovarian cancer (EOC), where STn-glycosylated forms of CA125 and CA15-3 antigens can better discriminate cancer from benign conditions. We have developed a dual-label LFA that detects both CA125-STn and CA15-3-STn within a single anti-STn antibody test line. This utilizes spectral separation of green (540 nm) and blue (450 nm) emitting erbium (NaYF4:Yb3+, Er3+)- and thulium (NaYF4: Yb3+, Tm3+)-doped upconverting nanoparticle (UCNP) reporters conjugated with antibodies against the protein epitopes in CA125 or CA15-3. This technology allows the simultaneous detection of different antigen variants from a single test line. The developed proof-of-concept dual-label LFA was able to distinguish between the ascites fluid samples from diagnosed ovarian cancer patients (n = 10) and liver cirrhosis ascites fluid samples (n = 3) used as a negative control. The analytical sensitivity of CA125-STn for the dual-label LFA was 1.8 U/ml in buffer and 3.6 U/ml in ascites fluid matrix. Here we demonstrate a novel approach of spectrally separated measurement of STn-glycosylated forms of two different cancer-associated protein biomarkers by using UCNP reporter technology.
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Affiliation(s)
- Miikka Ekman
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Turku, Finland
| | - Teppo Salminen
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Turku, Finland
| | - Kirsti Raiko
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Turku, Finland
| | - Tero Soukka
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Turku, Finland
| | - Kamlesh Gidwani
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Turku, Finland
| | - Iida Martiskainen
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Turku, Finland.
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Raiko K, Nääjärvi O, Ekman M, Koskela S, Soukka T, Martiskainen I, Salminen T. Improved sensitivity and automation of a multi-step upconversion lateral flow immunoassay using a 3D-printed actuation mechanism. Anal Bioanal Chem 2024; 416:1517-1525. [PMID: 38280018 PMCID: PMC10861389 DOI: 10.1007/s00216-024-05156-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Revised: 12/04/2023] [Accepted: 01/09/2024] [Indexed: 01/29/2024]
Abstract
The development of sensitive point-of-care (POC) assay platforms is of interest for reducing the cost and time of diagnostics. Lateral flow assays (LFAs) are the gold standard for POC systems, but their sensitivity as such is inadequate, for example, in the case of cardiac diagnostics. The performance can be improved by incorporating different steps, such as pre-incubation to prolong the interaction time between sample and reporter for immunocomplex formation, and washing steps for background reduction. However, for POC assays, manual steps by the assay conductor are not desired. In this research, upconverting nanoparticles (UCNPs) were coated with poly(acrylic acid) (PAA) and conjugated to anti-cTnI antibodies, yielding non-clustering particles with low non-specific binding. The performance of cTnI-LFA in the PAA-anti-cTnI-UCNPs was compared to the same UCNPs with a commercial carboxyl surface. A kitchen-timer mechanism was embedded in a 3D-printed housing to produce a low-cost actuator facilitating a timed pre-incubation step for reporter and sample, and a washing step, to enable a multi-step cTnI-LFA with minimized manual labour. PAA-UCNPs showed improved mobility on nitrocellulose compared to those with a commercial surface. The mechanical actuator system was shown to improve sensitivity compared to a labour-intensive multi-step dipstick method, despite pre-incubation occurring during shaking and heating in the dipstick method. The limit of detection decreased from 7.6 to 1.5 ng/L cTnI in human plasma. The presented actuator can be easily modified for sensitivity improvement in the LFA for different analytes via pre-incubation and washing steps.
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Affiliation(s)
- Kirsti Raiko
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland.
| | - Oskari Nääjärvi
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Miikka Ekman
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Sonja Koskela
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Tero Soukka
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Iida Martiskainen
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Teppo Salminen
- Biotechnology Unit, Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
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Kuusinen S, Ekman M, Raiko K, Hannula H, Lyytikäinen A, Lahtinen S, Soukka T. Complement C1q in plasma induces nonspecific binding of poly(acrylic acid)-coated upconverting nanoparticle antibody conjugates. Anal Bioanal Chem 2022; 414:3741-3749. [PMID: 35332370 PMCID: PMC9035425 DOI: 10.1007/s00216-022-04021-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/09/2022] [Accepted: 03/14/2022] [Indexed: 11/11/2022]
Abstract
Upconverting nanoparticles are attractive reporters for immunoassays, because their high specific activity and lack of autofluorescence background enable their detection at extremely low concentrations. However, the sensitivity achieved with heterogeneous sandwich immunoassays using nanoparticle reporters is generally limited by the nonspecific binding of nanoparticle antibody conjugates to solid supports. In this study, we characterized plasma components associated with elevated nonspecific binding of poly(acrylic acid)-coated upconverting nanoparticles in heterogeneous two-step sandwich immunoassays. Plasma was consecutively fractionated using various chromatographic methods by selecting after each step the fractions producing the highest nonspecific binding of upconverting nanoparticle conjugates in an immunoassay for cardiac troponin I. Finally, the proteins in the fractions associated with highest amount of nonspecific binding were separated by gel electrophoresis and identified with mass spectrometry. The results indicated that complement component C1q was present in the fractions associated with the highest signal from nonspecific binding. The interference was not limited to only poly(acrylic acid)-coated nanoparticles or certain antibody combination, but occurred more generally. The interference was removed by increasing the ionic strength of the assay buffer in the sample incubation step or by adding a negatively charged blocker to bind on positively charged C1q, suggesting that the interaction is mostly electrostatic. Hence, we assume that the interference is likely to affect various negatively charged nanoparticles. The identification of complement component C1q as the major interfering protein allows for more rational design of countermeasures in future immunoassay development utilizing nanoparticle reporters.
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Affiliation(s)
- Saara Kuusinen
- Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland.
| | - Miikka Ekman
- Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Kirsti Raiko
- Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Heidi Hannula
- Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Annika Lyytikäinen
- Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Satu Lahtinen
- Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
| | - Tero Soukka
- Department of Life Technologies, Faculty of Technology, University of Turku, Kiinamyllynkatu 10, 20520, Turku, Finland
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Brandmeier JC, Raiko K, Farka Z, Peltomaa R, Mickert MJ, Hlaváček A, Skládal P, Soukka T, Gorris HH. Effect of Particle Size and Surface Chemistry of Photon-Upconversion Nanoparticles on Analog and Digital Immunoassays for Cardiac Troponin. Adv Healthc Mater 2021; 10:e2100506. [PMID: 34263562 DOI: 10.1002/adhm.202100506] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 06/22/2021] [Indexed: 12/26/2022]
Abstract
Sensitive immunoassays are required for troponin, a low-abundance cardiac biomarker in blood. In contrast to conventional (analog) assays that measure the integrated signal of thousands of molecules, digital assays are based on counting individual biomarker molecules. Photon-upconversion nanoparticles (UCNP) are an excellent nanomaterial for labeling and detecting single biomarker molecules because their unique anti-Stokes emission avoids optical interference, and single nanoparticles can be reliably distinguished from the background signal. Here, the effect of the surface architecture and size of UCNP labels on the performance of upconversion-linked immunosorbent assays (ULISA) is critically assessed. The size, brightness, and surface architecture of UCNP labels are more important for measuring low troponin concentrations in human plasma than changing from an analog to a digital detection mode. Both detection modes result approximately in the same assay sensitivity, reaching a limit of detection (LOD) of 10 pg mL-1 in plasma, which is in the range of troponin concentrations found in the blood of healthy individuals.
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Affiliation(s)
- Julian C. Brandmeier
- Institute of Analytical Chemistry, Chemo‐ and Biosensors University of Regensburg Regensburg 93053 Germany
| | - Kirsti Raiko
- Department of Life Technologies/Biotechnology University of Turku Kiinamyllynkatu 10 Turku 20520 Finland
| | - Zdeněk Farka
- Institute of Analytical Chemistry, Chemo‐ and Biosensors University of Regensburg Regensburg 93053 Germany
- Department of Biochemistry, Faculty of Science Masaryk University Kamenice 5 Brno 625 00 Czech Republic
| | - Riikka Peltomaa
- Institute of Analytical Chemistry, Chemo‐ and Biosensors University of Regensburg Regensburg 93053 Germany
- Department of Life Technologies/Biotechnology University of Turku Kiinamyllynkatu 10 Turku 20520 Finland
| | - Matthias J. Mickert
- Institute of Analytical Chemistry, Chemo‐ and Biosensors University of Regensburg Regensburg 93053 Germany
| | - Antonín Hlaváček
- Institute of Analytical Chemistry of the Czech Academy of Sciences v. v. i. Brno 602 00 Czech Republic
| | - Petr Skládal
- Department of Biochemistry, Faculty of Science Masaryk University Kamenice 5 Brno 625 00 Czech Republic
| | - Tero Soukka
- Department of Life Technologies/Biotechnology University of Turku Kiinamyllynkatu 10 Turku 20520 Finland
| | - Hans H. Gorris
- Institute of Analytical Chemistry, Chemo‐ and Biosensors University of Regensburg Regensburg 93053 Germany
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