Change search
ReferencesLink to record
Permanent link

Direct link
Cell shape identification using digital holographic microscopy
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.ORCID iD: 0000-0002-9031-4331
Umeå University, Faculty of Science and Technology, Department of Physics.
2015 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 54, no 24, 7442-7448 p.Article in journal (Refereed) Published
Abstract [en]

We present a cost-effective, simple and fast digital holographic microscopy method based upon Rayleigh-Sommerfeld back propagation for identification of the geometrical shape of a cell. The method was tested using synthetic hologram images generated by ray-tracing software and from experimental images of semi-transparent spherical beads and living red blood cells. Our results show that by only using the real part of the back-reconstructed amplitude the proposed method can provide information of the geometrical shape of the object and at the same time accurately determine the axial position of the object under study. The proposed method can be used in flow chamber assays for pathophysiological studies where fast morphological changes of cells are studied in high numbers and at different heights.

Place, publisher, year, edition, pages
Optical Society of America, 2015. Vol. 54, no 24, 7442-7448 p.
Keyword [en]
Microscopy, Digital holography, Optical tweezers or optical manipulation
National Category
Atom and Molecular Physics and Optics
URN: urn:nbn:se:umu:diva-106588DOI: 10.1364/AO.54.007442ISI: 000360190200039PubMedID: 26368783OAI: diva2:842714
Available from: 2015-07-22 Created: 2015-07-22 Last updated: 2016-05-27Bibliographically approved
In thesis
1. The mechanics of adhesion polymers and their role in bacterial attachment
Open this publication in new window or tab >>The mechanics of adhesion polymers and their role in bacterial attachment
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacterial resistance to antibiotics is increasing at a high rate in both developing and developed countries. To circumvent the problem of drug-resistant bacterial pathogens, we need to develop new effective methods, substances, and materials that can disarm and prevent them from causing infections. However, to do this we first need to find new possible targets in bacteria to approach and novel strategies to apply.Escherichia coli (E. coli) bacteria is a normal member of the intestinal microflora of humans and mammals, but frequently cause diverse intestinal and external diseases by means of virulence factors, which leads to hundreds of million sick people each year with a high mortality rate. An E. coli bacterial infection starts with adhesion to a host cell using cell surface expressed adhesion polymers, called adhesion pili. Depending on the local environment different types of pili are expressed by the bacteria. For example, bacteria found in the gastrointestinal tract commonly express different pili in comparison to those found in the urinary tract and respiratory tract. These pili, which are vital for bacterial adhesion, thereby serve as a new possible approach in the fight against bacterial infections by targeting and disabling these structures using novel chemicals. However, in order to develop such chemicals, better understanding of these pili is needed.Optical tweezers (OT) can measure and apply forces up to a few hundred pN with sub-pN force resolution and have shown to be an excellent tool for investigating mechanical properties of adhesion pili. It has been found that pili expressed by E. coli have a unique and complex force-extension response that is assumed to be important for the ability of bacteria to initiate and maintain attachment to the host cells. However, their mechanical functions and the advantage of specific mechanical functions, especially in the initial attachment process, have not yet been fully understood.In this work, a detailed description of the pili mechanics and their role during cell adhesion is presented. By using results from optical tweezers force spectroscopy experiments in combination with physical modeling and numerical simulations, we investigated how pili can act as “shock absorbers” through uncoiling and thereby lower the fluid force acting on a bacterium. Our result demonstrate that the dynamic uncoiling capability of the helical part of the adhesion pili modulate the force to fit the optimal lifetime of its adhesin (the protein that binds to the receptor on the host cell), ensuring a high survival probability of the bond.iiiSince the attachment process is in proximity of a surface we also investigated the influence of tether properties and the importance of different surface corrections and additional force components to the Stokes drag force during simulations. The investigation showed that the surface corrections to the Stokes drag force and the Basset force cannot be neglected when simulating survival probability of a bond, since that can overestimate the probability by more than an order of magnitude.Finally, a theoretical and experimental framework for two separate methods was developed. The first method can detect the presence of pili on single cells using optical tweezers. We verified the method using silica microspheres coated with a polymer brush and E. coli bacteria expressing; no pili, P pili, and type 1 pili, respectively. The second method was based on digital holography microscopy. Using the diffraction of semi-transparent object such as red blood cells, we showed that this method can reconstruct the axial position and detect morphological changes of cells.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2015. 65 p.
Pili, optical tweezers, bacterial adhesion, fimbriae, uncoiling
National Category
Other Physics Topics Biophysics
urn:nbn:se:umu:diva-109524 (URN)978-91-7601-331-1 (ISBN)
Public defence
2015-10-23, Naturvetarhuset, N420, Umeå universitet, Umeå, 13:00 (English)
Available from: 2015-10-02 Created: 2015-09-30 Last updated: 2015-10-02Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Zakrisson, JohanSchedin, StaffanAndersson, Magnus
By organisation
Department of PhysicsDepartment of Applied Physics and Electronics
In the same journal
Applied Optics
Atom and Molecular Physics and Optics

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 203 hits
ReferencesLink to record
Permanent link

Direct link