Publications by authors named "Ada-Ioana Bunea"

8 Publications

  • Page 1 of 1

Polarization-Dependent All-Dielectric Metasurface for Single-Shot Quantitative Phase Imaging.

Nano Lett 2021 May 22;21(9):3820-3826. Epub 2021 Apr 22.

DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Kgs. Lyngby 2800, Denmark.

Phase retrieval is a noninterferometric quantitative phase imaging technique that has become an essential tool in optical metrology and label-free microscopy. Phase retrieval techniques require multiple intensity measurements traditionally recorded by camera or sample translation, which limits their applicability mostly to static objects. In this work, we propose the use of a single polarization-dependent all-dielectric metasurface to facilitate the simultaneous recording of two images, which are utilized in phase calculation based on the transport-of-intensity equation. The metasurface acts as a multifunctional device that splits two orthogonal polarization components and adds a propagation phase shift onto one of them. As a proof-of-principle, we demonstrate the technique in the wavefront sensing of technical samples using a standard imaging setup. Our metasurface-based approach fosters a fast and compact configuration that can be integrated into commercial imaging systems.
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http://dx.doi.org/10.1021/acs.nanolett.1c00190DOI Listing
May 2021

Recent Advances in Microswimmers for Biomedical Applications.

Micromachines (Basel) 2020 Nov 27;11(12). Epub 2020 Nov 27.

National Centre for Nano Fabrication and Characterization (DTU Nanolab), Technical University of Denmark, Ørsted Plads 347, 2800 Lyngby, Denmark.

Microswimmers are a rapidly developing research area attracting enormous attention because of their many potential applications with high societal value. A particularly promising target for cleverly engineered microswimmers is the field of biomedical applications, where many interesting examples have already been reported for e.g., cargo transport and drug delivery, artificial insemination, sensing, indirect manipulation of cells and other microscopic objects, imaging, and microsurgery. Pioneered only two decades ago, research studies on the use of microswimmers in biomedical applications are currently progressing at an incredibly fast pace. Given the recent nature of the research, there are currently no clinically approved microswimmer uses, and it is likely that several years will yet pass before any clinical uses can become a reality. Nevertheless, current research is laying the foundation for clinical translation, as more and more studies explore various strategies for developing biocompatible and biodegradable microswimmers fueled by in vivofriendly means. The aim of this review is to provide a summary of the reported biomedical applications of microswimmers, with focus on the most recent advances. Finally, the main considerations and challenges for clinical translation and commercialization are discussed.
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http://dx.doi.org/10.3390/mi11121048DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760273PMC
November 2020

Membrane interactions in drug delivery: Model cell membranes and orthogonal techniques.

Adv Colloid Interface Sci 2020 Jul 11;281:102177. Epub 2020 May 11.

Center for Biopharmaceuticals and Biobarriers in Drug Delivery, Dept. of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, Copenhagen Ø DK-2100, Denmark.

To generate the desired effect in the human body, the active pharmaceutical ingredient usually needs to interact with a receptor located on the cell membrane or inside the cell. Thus, understanding membrane interactions is of great importance when it comes to the development and testing of new drug molecules or new drug delivery systems. Nowadays, there is a tremendous selection of both model cell membranes and of techniques that can be used to characterize interactions between selected model cell membranes and a drug molecule, an excipient, or a drug delivery system. Having such a wide selection of model cell membranes and techniques available makes it sometimes challenging to select the optimal combination for a specific study. Furthermore, it is difficult to compare results obtained using different model cell membranes and techniques, and not all in vitro studies translate as well to an estimation of the in vivo biological activity or understanding of mode of action. This review provides an overview of the available lipid bilayer-based model cell membranes and of the most widely employed techniques for studying membrane interactions. Finally, the need for employing complimentary characterization techniques in order to acquire more reliable and in-depth information is highlighted.
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http://dx.doi.org/10.1016/j.cis.2020.102177DOI Listing
July 2020

Leaky Optoelectrical Fiber for Optogenetic Stimulation and Electrochemical Detection of Dopamine Exocytosis from Human Dopaminergic Neurons.

Adv Sci (Weinh) 2019 Dec 16;6(24):1902011. Epub 2019 Oct 16.

Department of Biotechnology and Biomedicine (DTU Bioengineering) Technical University of Denmark Produktionstorvet Building 423, Room 122 2800 Kongens Lyngby Denmark.

In Parkinson's disease, the degeneration of dopaminergic neurons in substantia nigra leads to a decrease in the physiological levels of dopamine in striatum. The existing dopaminergic therapies effectively alleviate the symptoms, albeit they do not revert the disease progression and result in significant adverse effects. Transplanting dopaminergic neurons derived from stem cells could restore dopamine levels without additional motor complications. However, the transplanted cells disperse in vivo and it is not possible to stimulate them on demand to modulate dopamine release to prevent dyskinesia. In order to address these issues, this paper presents a multifunctional leaky optoelectrical fiber for potential neuromodulation and as a cell substrate for application in combined optogenetic stem cell therapy. Pyrolytic carbon coated optical fibers are laser ablated to pattern micro-optical windows to permit light leakage over a large area. The pyrolytic carbon acts as an excellent electrode for the electrochemical detection of dopamine. Human neural stem cells are genetically modified to express the light sensitive opsin channelrhodopsin-2 and are differentiated into dopaminergic neurons on the leaky optoelectrical fiber. Finally, light leaking from the micro-optical windows is used to stimulate the dopaminergic neurons resulting in the release of dopamine that is detected in real-time using chronoamperometry.
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http://dx.doi.org/10.1002/advs.201902011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6918109PMC
December 2019

Optical catapulting of microspheres in mucus models-toward overcoming the mucus biobarrier.

J Biomed Opt 2019 03;24(3):1-9

Technical University of Denmark, DTU Fotonik, Department of Photonics Engineering, Kongens Lyngby, Denmark.

The generalized phase contrast method is employed as an efficient "phase-only" laser beam-shaping technique in an optical setup built for catapulting microspheres through simple mucus models. The influence of the laser power and mucin concentration on the motion of the microspheres is investigated in terms of instant and average velocities on a 250-μm trajectory, corresponding to the mucus thickness in the human gastrointestinal tract. Increasing the laser power leads to higher velocities in all the tested samples, while increasing the mucin concentration leads to significant velocity decrease for similar laser input power. However, velocities of up to 95  μm  ·  s  -  1 are demonstrated in a 5% mucin simple mucus model using our catapulting system. This study contributes to understanding and overcoming the challenges of optical manipulation in mucus models. This paves the way for efficient optical manipulation of three-dimensional-printed light-controlled microtools with the ability to penetrate the mucus biobarrier for in vitro drug-delivery studies.
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http://dx.doi.org/10.1117/1.JBO.24.3.035001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6975190PMC
March 2019

Natural convection induced by an optically fabricated and actuated microtool with a thermoplasmonic disk.

Opt Lett 2018 Aug;43(16):3870-3873

Two-photon polymerization was employed for fabricating microtools amenable to optical trapping and manipulation. A disk feature was included as part of the microtools and further functionalized by electron-beam deposition. The nanostructured gold layer on the disk facilitates off-resonant plasmonic heating upon illumination with a laser beam. As a consequence, natural convection characterized by the typical toroidal shape resembling that of Rayleigh-Bénard flow can be observed. A velocity of several μm·s is measured for 2 μm microspheres dispersed in the surroundings of the microtool. To the best of our knowledge, this is the first time that thermoplasmonic-induced natural convection is experimentally demonstrated using a mobile heat source.
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http://dx.doi.org/10.1364/OL.43.003870DOI Listing
August 2018

Sensing based on the motion of enzyme-modified nanorods.

Biosens Bioelectron 2015 May 6;67:42-8. Epub 2014 Jun 6.

International Centre of Biodynamics, 1B Intrarea Portocalelor, 060101 Bucharest, Romania. Electronic address:

Asymmetric modification with an enzyme confers nanorods an enhanced diffusive motion that is dependent on the concentration of the enzyme substrate. In turn, such a motion opens the possibility of determining the concentration of the enzyme substrate by measuring the diffusion coefficient of nanorods modified with the appropriate enzyme. Nanorods, with a Pt and a polypyrrole (PPy) segment, were fabricated. The PPy segment of such nanorods was then modified with glucose oxidase (GOx), glutamate oxidase (GluOx), or xanthine oxidase (XOD). Calibration curves, linking the diffusion coefficient of the oxidase-modified nanorods to the concentration of the oxidase substrate, were subsequently built. The oxidase-modified nanorods and their calibration curves were finally used to determine substrate concentrations both in simple aqueous solutions and in complex samples such as horse serum and cell culture media. Based on the obtained results we are confident that our motion-based approach to sensing can be developed to the point where different nanorods in a mixture simultaneously report on the concentration of different compounds with good temporal and spatial resolution.
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http://dx.doi.org/10.1016/j.bios.2014.05.062DOI Listing
May 2015

Modification with hemeproteins increases the diffusive movement of nanorods in dilute hydrogen peroxide solutions.

Chem Commun (Camb) 2013 Oct;49(78):8803-5

International Centre of Biodynamics, 1B Intrarea Portocalelor, 060101 - Bucharest, Romania.

Nanorods were decorated with different hemeproteins that are able to convert hydrogen peroxide. When dispersed into hydrogen peroxide solutions, most of these nanorods are characterized by diffusion coefficients which increase with the concentration of hydrogen peroxide. Such a behaviour does not characterize unmodified nanorods.
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http://dx.doi.org/10.1039/c3cc44614jDOI Listing
October 2013