Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fitting
Abstract Interferometric scattering microscopy (iSCAT) enables tracking single nano-objects in three dimensions (3D). Conventional image processing methods for 3D localization in iSCAT typically rely on template matching, which involves finding the maximum cross-correlation with modeled interferomet...
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| Format: | Article |
| Language: | English |
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Nature Portfolio
2025-05-01
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| Series: | npj Nanophotonics |
| Online Access: | https://doi.org/10.1038/s44310-025-00068-3 |
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| author | Liaoliao Wei Caroline Livan Anyi Huakun Li Haitao Nie Bihan Wen Tong Ling |
| author_facet | Liaoliao Wei Caroline Livan Anyi Huakun Li Haitao Nie Bihan Wen Tong Ling |
| author_sort | Liaoliao Wei |
| collection | DOAJ |
| description | Abstract Interferometric scattering microscopy (iSCAT) enables tracking single nano-objects in three dimensions (3D). Conventional image processing methods for 3D localization in iSCAT typically rely on template matching, which involves finding the maximum cross-correlation with modeled interferometric point spread functions (iPSFs). However, this approach can be computationally intensive and hinders the processing of nano-object movements on a large scale. In this study, we introduce an efficient analytical fitting approach for retrieving the 3D positions of nano-objects in wide-field iSCAT. We derive an approximate analytic iPSF model based on the Richards-Wolf vectorial diffraction model. The simplified analytic function includes a quadratically scaling amplitude term and a linearly scaling phase term, both of which change with the nano-object’s axial position. After using the Bayesian estimation method to obtain initial parameters, we can retrieve the axial location of the nano-object through univariate least squares fitting, achieving a 60- to 200-fold increase in processing speed compared with template matching. Intriguingly, we also show that without approximation, least squares fitting can yield higher precision than cross-correlation. We validate the proposed method by measuring the movements of static and moving nanoparticles in multiple experiments. In particular, we record the movements of nanoparticles on the order of tens of nanometers accompanying the thermal expansion of a polydimethylsiloxane (PDMS) substrate. The retrieved nanoparticle displacement matches the estimated expansion from finite element modeling. By combining precise Bayesian estimation of the fixed parameters and analytical fitting in which the only variable is the nano-object’s axial position, our method enables high-throughput 3D tracking of nano-objects in a wide field of view. This approach may benefit label-free monitoring of nano-objects (such as nanoparticles, exosomes, and viruses) on a large scale. |
| format | Article |
| id | doaj-art-3419a014dc584763a6bed8216f8e052d |
| institution | DOAJ |
| issn | 2948-216X |
| language | English |
| publishDate | 2025-05-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | npj Nanophotonics |
| spelling | doaj-art-3419a014dc584763a6bed8216f8e052d2025-08-20T03:22:03ZengNature Portfolionpj Nanophotonics2948-216X2025-05-01211810.1038/s44310-025-00068-3Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fittingLiaoliao Wei0Caroline Livan Anyi1Huakun Li2Haitao Nie3Bihan Wen4Tong Ling5School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological UniversitySchool of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological UniversitySchool of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological UniversityDepartment of Electrical and Electronic Engineering, The University of Hong KongSchool of Electrical and Electronic Engineering, Nanyang Technological UniversitySchool of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological UniversityAbstract Interferometric scattering microscopy (iSCAT) enables tracking single nano-objects in three dimensions (3D). Conventional image processing methods for 3D localization in iSCAT typically rely on template matching, which involves finding the maximum cross-correlation with modeled interferometric point spread functions (iPSFs). However, this approach can be computationally intensive and hinders the processing of nano-object movements on a large scale. In this study, we introduce an efficient analytical fitting approach for retrieving the 3D positions of nano-objects in wide-field iSCAT. We derive an approximate analytic iPSF model based on the Richards-Wolf vectorial diffraction model. The simplified analytic function includes a quadratically scaling amplitude term and a linearly scaling phase term, both of which change with the nano-object’s axial position. After using the Bayesian estimation method to obtain initial parameters, we can retrieve the axial location of the nano-object through univariate least squares fitting, achieving a 60- to 200-fold increase in processing speed compared with template matching. Intriguingly, we also show that without approximation, least squares fitting can yield higher precision than cross-correlation. We validate the proposed method by measuring the movements of static and moving nanoparticles in multiple experiments. In particular, we record the movements of nanoparticles on the order of tens of nanometers accompanying the thermal expansion of a polydimethylsiloxane (PDMS) substrate. The retrieved nanoparticle displacement matches the estimated expansion from finite element modeling. By combining precise Bayesian estimation of the fixed parameters and analytical fitting in which the only variable is the nano-object’s axial position, our method enables high-throughput 3D tracking of nano-objects in a wide field of view. This approach may benefit label-free monitoring of nano-objects (such as nanoparticles, exosomes, and viruses) on a large scale.https://doi.org/10.1038/s44310-025-00068-3 |
| spellingShingle | Liaoliao Wei Caroline Livan Anyi Huakun Li Haitao Nie Bihan Wen Tong Ling Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fitting npj Nanophotonics |
| title | Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fitting |
| title_full | Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fitting |
| title_fullStr | Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fitting |
| title_full_unstemmed | Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fitting |
| title_short | Fast 3D localization of nano-objects in wide-field interferometric scattering microscopy via vectorial diffraction model-derived analytical fitting |
| title_sort | fast 3d localization of nano objects in wide field interferometric scattering microscopy via vectorial diffraction model derived analytical fitting |
| url | https://doi.org/10.1038/s44310-025-00068-3 |
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