Publications by authors named "Maria Leilani Torres-Mapa"

14 Publications

  • Page 1 of 1

Holographic optogenetic stimulation with calcium imaging as an all optical tool for cardiac electrophysiology.

J Biophotonics 2022 Apr 9:e202100352. Epub 2022 Apr 9.

Institute of Quantum Optics, Gottfried Wilhelm Leibniz University, Hannover, Germany.

All optical approaches to control and read out the electrical activity in a cardiac syncytium can improve our understanding of cardiac electrophysiology. Here, we demonstrate optogenetic stimulation of cardiomyocytes with high spatial precision using light foci generated with a ferroelectric spatial light modulator. Computer generated holograms binarized by bidirectional error diffusion create multiple foci with more even intensity distribution compared with thresholding approach. We evoke the electrical activity of cardiac HL1 cells expressing the channelrhodopsin-2 variant, ChR2(H134R) using single and multiple light foci and at the same time visualize the action potential using a calcium sensitive indicator called Cal-630. We show that localized regions in the cardiac monolayer can be stimulated enabling us to initiate signal propagation from a precise location. Furthermore, we demonstrate that probing the cardiac cells with multiple light foci enhances the excitability of the cardiac network. This approach opens new applications in manipulating and visualizing the electrical activity in a cardiac syncytium.
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http://dx.doi.org/10.1002/jbio.202100352DOI Listing
April 2022

3D printed microfluidic lab-on-a-chip device for fiber-based dual beam optical manipulation.

Sci Rep 2021 07 16;11(1):14584. Epub 2021 Jul 16.

Institute of Quantum Optics, Gottfried Wilhelm Leibniz University Hannover, Welfengarten 1, 30167, Hannover, Germany.

3D printing of microfluidic lab-on-a-chip devices enables rapid prototyping of robust and complex structures. In this work, we designed and fabricated a 3D printed lab-on-a-chip device for fiber-based dual beam optical manipulation. The final 3D printed chip offers three key features, such as (1) an optimized fiber channel design for precise alignment of optical fibers, (2) an optically clear window to visualize the trapping region, and (3) a sample channel which facilitates hydrodynamic focusing of samples. A square zig-zag structure incorporated in the sample channel increases the number of particles at the trapping site and focuses the cells and particles during experiments when operating the chip at low Reynolds number. To evaluate the performance of the device for optical manipulation, we implemented on-chip, fiber-based optical trapping of different-sized microscopic particles and performed trap stiffness measurements. In addition, optical stretching of MCF-7 cells was successfully accomplished for the purpose of studying the effects of a cytochalasin metabolite, pyrichalasin H, on cell elasticity. We observed distinct changes in the deformability of single cells treated with pyrichalasin H compared to untreated cells. These results demonstrate that 3D printed microfluidic lab-on-a-chip devices offer a cost-effective and customizable platform for applications in optical manipulation.
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http://dx.doi.org/10.1038/s41598-021-93205-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8285473PMC
July 2021

Probing Ligand-Receptor Interaction in Living Cells Using Force Measurements With Optical Tweezers.

Front Bioeng Biotechnol 2020 17;8:598459. Epub 2020 Nov 17.

Institute of Quantum Optics, Leibniz University Hannover, Hannover, Germany.

This work probes the binding kinetics of COOH-terminus of (c-CPE) and claudin expressing MCF-7 cells using force spectroscopy with optical tweezers. c-CPE is of high biomedical interest due to its ability to specifically bind to claudin with high affinity as well as reversibly disrupt tight junctions whilst maintaining cell viability. We observed single-step rupture events between silica particles functionalized with c-CPE and MCF-7 cells. Extensive calibration of the optical tweezers' trap stiffness and displacement of the particle from trap center extracted a probable bond rupture force of ≈ 18 pN. The probability of rupture events with c-CPE functionalized silica particles increased by 50% compared to unfunctionalized particles. Additionally, rupture events were not observed when probing cells not expressing claudin with c-CPE coated particles. Overall, this work demonstrates that optical tweezers are invaluable tools to probe ligand-receptor interactions and their potential to study dynamic molecular events in drug-binding scenarios.
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http://dx.doi.org/10.3389/fbioe.2020.598459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7705203PMC
November 2020

Fabrication of a Monolithic Lab-on-a-Chip Platform with Integrated Hydrogel Waveguides for Chemical Sensing.

Sensors (Basel) 2019 Oct 8;19(19). Epub 2019 Oct 8.

Institute of Quantum Optics, Gottfried Wilhelm Leibniz University Hannover, 30167 Hannover, Germany.

Hydrogel waveguides have found increased use for variety of applications where biocompatibility and flexibility are important. In this work, we demonstrate the use of polyethylene glycol diacrylate (PEGDA) waveguides to realize a monolithic lab-on-a-chip device. We performed a comprehensive study on the swelling and optical properties for different chain lengths and concentrations in order to realize an integrated biocompatible waveguide in a microfluidic device for chemical sensing. Waveguiding properties of PEGDA hydrogel were used to guide excitation light into a microfluidic channel to measure the fluorescence emission profile of rhodamine 6G as well as collect the fluorescence signal from the same device. Overall, this work shows the potential of hydrogel waveguides to facilitate delivery and collection of optical signals for potential use in wearable and implantable lab-on-a-chip devices.
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http://dx.doi.org/10.3390/s19194333DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6806100PMC
October 2019

Shrinkable silver diffraction grating fabricated inside a hydrogel using 522-nm femtosecond laser.

Sci Rep 2018 01 9;8(1):187. Epub 2018 Jan 9.

School of Integrated Design Engineering, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama, 223-8522, Japan.

The integration of metal microstructures and soft materials is promising for the realization of novel optical and biomedical devices owing to the flexibility and biocompatibility of the latter. Nevertheless, the fabrication of three-dimensional metal structures within a soft material is still challenging. In this study, we demonstrate the fabrication of a silver diffraction grating inside a biocompatible poly(ethylene glycol) diacrylate (PEGDA) hydrogel by using a 522-nm femtosecond laser via multi-photon photoreduction of silver ions. The optical diffraction pattern obtained with the grating showed equally spaced diffraction spots, which indicated that a regular, periodic silver grating was formed. Notably, the distance between the diffraction spots changed when the water content in the hydrogel was reduced. The grating period decreased when the hydrogel shrank owing to the loss of water, but the straight shapes of the line structures were preserved, which demonstrated the optical tunability of the fabricated structure. Our results demonstrate the potential of the femtosecond laser-based photoreduction technique for the fabrication of novel tunable optical devices as well as highly precise structures.
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http://dx.doi.org/10.1038/s41598-017-17636-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5760663PMC
January 2018

Structural damage of Bacillus subtilis biofilms using pulsed laser interaction with gold thin films.

J Biophotonics 2017 Aug 7;10(8):1043-1052. Epub 2016 Oct 7.

Institute of Quantum Optics, Gottfried Wilhelm Leibniz University Hannover, Welfengarten 1, 30167, Hannover, Germany.

There is a huge interest in developing strategies to effectively eliminate biofilms due to their negative impact in both industrial and clinical settings. In this study, structural damage was induced on two day-old B. subtilis biofilms using the interaction of 532 nm pulsed laser with gold thin films. Radiant exposure of 225 mJ/cm induced distinct changes on the surface structure and overall morphology of the matured biofilms after laser irradiation. Moreover, at the radiant exposure used, changes in the colour and viscosity of the biofilm were observed which may indicate a compromised extracellular matrix. Irradiated biofilms in the presence of gold film also showed strong propidium iodide signal which implies an increase in the number of dead bacterial cells after laser treatment. Thus, this laser-based technique is a promising approach in targeting and eradicating matured biofilms attached on surfaces such as medical implants.
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http://dx.doi.org/10.1002/jbio.201600146DOI Listing
August 2017

Gold Nanoparticle-Mediated Delivery of Molecules into Primary Human Gingival Fibroblasts Using ns-Laser Pulses: A Pilot Study.

Materials (Basel) 2016 May 20;9(5). Epub 2016 May 20.

Department of Operative Dentistry, Carolinum Dental University-Institute GmbH, J.W. Goethe University, Theodor-Stern-Kai 7, Frankfurt am Main 60590, Germany.

Interaction of gold nanoparticles (AuNPs) in the vicinity of cells' membrane with a pulsed laser (λ = 532 nm, τ = 1 ns) leads to perforation of the cell membrane, thereby allowing extracellular molecules to diffuse into the cell. The objective of this study was to develop an experimental setting to deliver molecules into primary human gingival fibroblasts (pHFIB-G) by using ns-laser pulses interacting with AuNPs (study group). To compare the parameters required for manipulation of pHFIB-G with those needed for cell lines, a canine pleomorphic adenoma cell line (ZMTH3) was used (control group). Non-laser-treated cells incubated with AuNPs and the delivery molecules served as negative control. Laser irradiation (up to 35 mJ/cm²) resulted in a significant proportion of manipulated fibroblasts (up to 85%, compared to non-irradiated cells: < 0.05), while cell viability (97%) was not reduced significantly. pHFIB-G were perforated as efficiently as ZMTH3. No significant decrease of metabolic cell activity was observed up to 72 h after laser treatment. The fibroblasts took up dextrans with molecular weights up to 500 kDa. Interaction of AuNPs and a pulsed laser beam yields a spatially selective technique for manipulation of even primary cells such as pHFIB-G in high throughput.
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http://dx.doi.org/10.3390/ma9050397DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5503001PMC
May 2016

Femtosecond laser direct writing of metal microstructure in a stretchable poly(ethylene glycol) diacrylate (PEGDA) hydrogel.

Opt Lett 2016 Apr;41(7):1392-5

The fabrication of three-dimensional (3D) metal microstructures in a synthetic polymer-based hydrogel is demonstrated by femtosecond laser-induced photoreduction. The linear-shaped silver structure of approximately 2 micrometers in diameter is fabricated inside a biocompatible poly(ethylene glycol) diacrylate (PEGDA) hydrogel. The silver structure is observed and confirmed by scanning electron microscopy (SEM) and elemental analysis using energy-dispersive X-ray spectroscopy (EDX). Shrinking and swelling of the fabricated structure is also demonstrated experimentally, which shows the potential of the present method for realizing 3D flexible electronic and optical devices, as well as for fabricating highly integrated devices at submicron scales.
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http://dx.doi.org/10.1364/OL.41.001392DOI Listing
April 2016

Optical and electron microscopy study of laser-based intracellular molecule delivery using peptide-conjugated photodispersible gold nanoparticle agglomerates.

J Nanobiotechnology 2016 Jan 8;14. Epub 2016 Jan 8.

Institute of Quantum Optics, Leibniz University Hannover, Welfengarten 1, 30167, Hannover, Germany.

Background: Cell-penetrating peptides (CPPs) can act as carriers for therapeutic molecules such as drugs and genetic constructs for medical applications. The triggered release of the molecule into the cytoplasm can be crucial to its effective delivery. Hence, we implemented and characterized laser interaction with defined gold nanoparticle agglomerates conjugated to CPPs which enables efficient endosomal rupture and intracellular release of molecules transported.

Results: Gold nanoparticles generated by pulsed laser ablation in liquid were conjugated with CPPs forming agglomerates and the intracellular release of molecules was triggered via pulsed laser irradiation (γ = 532 nm, τ pulse = 1 ns). The CPPs enhance the uptake of the agglomerates along with the cargo which can be co-incubated with the agglomerates. The interaction of incident laser light with gold nanoparticle agglomerates leads to heat deposition and field enhancement in the vicinity of the particles. This highly precise effect deagglomerates the nanoparticles and disrupts the enclosing endosomal membrane. Transmission electron microscopy images confirmed this rupture for radiant exposures of 25 mJ/cm2 and above. Successful intracellular release was shown using the fluorescent dye calcein. For a radiant exposure of 35 mJ/cm2 we found calcein delivery in 81 % of the treated cells while maintaining a high percentage of cell viability. Furthermore, cell proliferation and metabolic activity were not reduced 72 h after the treatment.

Conclusion: CPPs trigger the uptake of the gold nanoparticle agglomerates via endocytosis and co-resident molecules in the endosomes are released by applying laser irradiation, preventing their intraendosomal degradation. Due to the highly localized effect, the cell membrane integrity is not affected. Therefore, this technique can be an efficient tool for spatially and temporally confined intracellular release. The utilization of specifically designed photodispersible gold nanoparticle agglomerates (65 nm) can open novel avenues in imaging and molecule delivery. Due to the induced deagglomeration the primary, small particles (~5 nm) are more likely to be removed from the body.
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http://dx.doi.org/10.1186/s12951-015-0155-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4706709PMC
January 2016

Fast targeted gene transfection and optogenetic modification of single neurons using femtosecond laser irradiation.

Sci Rep 2013 Nov 21;3:3281. Epub 2013 Nov 21.

1] University of St Andrews, School of Biology, St Andrews, UK [2] SUPA, University of St Andrews, School of Physics & Astronomy, St Andrews, UK [3] SULSA, Scottish Universities Life Sciences Alliance.

A prevailing problem in neuroscience is the fast and targeted delivery of DNA into selected neurons. The development of an appropriate methodology would enable the transfection of multiple genes into the same cell or different genes into different neighboring cells as well as rapid cell selective functionalization of neurons. Here, we show that optimized femtosecond optical transfection fulfills these requirements. We also demonstrate successful optical transfection of channelrhodopsin-2 in single selected neurons. We extend the functionality of this technique for wider uptake by neuroscientists by using fast three-dimensional laser beam steering enabling an image-guided "point-and-transfect" user-friendly transfection of selected cells. A sub-second transfection timescale per cell makes this method more rapid by at least two orders of magnitude when compared to alternative single-cell transfection techniques. This novel technology provides the ability to carry out large-scale cell selective genetic studies on neuronal ensembles and perform rapid genetic programming of neural circuits.
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http://dx.doi.org/10.1038/srep03281DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3836031PMC
November 2013

Integrated holographic system for all-optical manipulation of developing embryos.

Biomed Opt Express 2011 Jun 16;2(6):1564-75. Epub 2011 May 16.

We demonstrate a system for the combined optical injection and trapping of developing embryos. A Ti:sapphire femtosecond laser in tandem with a spatial light modulator, is used to perform fast and accurate beam-steering and multiplexing. We show successful intracellular delivery of a range of impermeable molecules into individual blastomeres of the annelid Pomatoceros lamarckii embryo by optoinjection, even when the embryo is still enclosed in a chorion. We also demonstrate the ability of the femtosecond laser optoinjection to deliver materials into inner layers of cells in a well-developed embryo. By switching to the continuous wave mode of the Ti:sapphire laser, the same system can be employed to optically trap and orient the 60 μm sized P. lamarckii embryo whilst maintaining its viability. Hence, a complete all-optical manipulation platform is demonstrated paving the way towards single-cell genetic modification and cell lineage mapping in emerging developmental biology model species.
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http://dx.doi.org/10.1364/BOE.2.001564DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114224PMC
June 2011

Quantitative phase study of the dynamic cellular response in femtosecond laser photoporation.

Biomed Opt Express 2010 Aug 2;1(2):414-424. Epub 2010 Aug 2.

We use Digital Holographic Microscopy to study dynamic responses of live cells to femtosecond laser cellular membrane photoporation. Temporal and spatial characteristics of morphological changes as well as dry mass variation are analyzed and compared with conventional fluorescent assays for viability and photoporation efficiency. With the latter, the results provide a new insight into the efficiency and toxicity of this novel optical method of drug delivery. In addition, quantitative phase maps reveal photoporation related sub-cellular dynamics of cytoplasmic vesicles.
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http://dx.doi.org/10.1364/BOE.1.000414DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3018012PMC
August 2010

Transient transfection of mammalian cells using a violet diode laser.

J Biomed Opt 2010 Jul-Aug;15(4):041506

University of St. Andrews, Scottish University Physics Alliance (SUPA), School of Physics and Astronomy, North Haugh, St. Andrews, Scotland, United Kingdom.

We demonstrate the first use of the violet diode laser for transient mammalian cell transfection. In contrast to previous studies, which showed the generation of stable cell lines over a few weeks, we develop a methodology to transiently transfect cells with an efficiency of up to approximately 40%. Chinese hamster ovary (CHO-K1) and human embryonic kidney (HEK293) cells are exposed to a tightly focused 405-nm laser in the presence of plasmid DNA encoding for a mitochondrial targeted red fluorescent protein. We report transfection efficiencies as a function of laser power and exposure time for our system. We also show, for the first time, that a continuous wave laser source can be successfully applied to selective gene silencing experiments using small interfering RNA. This work is a major step towards an inexpensive and portable phototransfection system.
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http://dx.doi.org/10.1117/1.3430730DOI Listing
January 2011

Application of dynamic diffractive optics for enhanced femtosecond laser based cell transfection.

J Biophotonics 2010 Oct;3(10-11):696-705

SULSA, School of Biology, University of St Andrews, St Andrews KY169TS, UK.

We demonstrate the advantages of a dynamic diffractive optical element, namely a spatial light modulator (SLM) for the controlled and enhanced optoinjection and phototransfection of mammalian cells with a femtosecond light source. The SLM provides full control over the lateral and axial positioning of the beam with sub-micron precision. Fast beam translation enables time-sequenced irradiation, which is shown to enhance the optoinjection efficiency and alleviate the problem of exact beam positioning on the cell membrane. We show that irradiation in three axial positions doubles the number of viably optoinjected cells when compared with a single dose. The presented system also enables untargeted raster scan irradiation which provides a higher throughput transfection of adherent cells at the rate of 1 cell per second. Additionally, fluorescent imaging is used to demonstrate cell selective two-step gene therapy.
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http://dx.doi.org/10.1002/jbio.201000052DOI Listing
October 2010
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