Researcher:
Kaleli, Humeyra Nur

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PhD Student

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Humeyra Nur

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Kaleli

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Kaleli, Humeyra Nur

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20225

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    RuO2 supercapacitor enables flexible, safe, and efficient optoelectronic neural interface
    (Wiley-V C H Verlag Gmbh, 2022) Ulgut, Burak; N/A; N/A; N/A; N/A; Department of Electrical and Electronics Engineering; Karatüm, Onuralp; Yıldız, Erdost; Kaleli, Humeyra Nur; Şahin, Afsun; Nizamoğlu, Sedat; PhD Student; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; Graduate School of Health Sciences; School of Medicine; College of Engineering; N/A; N/A; N/A; 171267; 130295
    Optoelectronic biointerfaces offer a wireless and nongenetic neurostimulation pathway with high spatiotemporal resolution. Fabrication of low-cost and flexible optoelectronic biointerfaces that have high photogenerated charge injection densities and clinically usable cell stimulation mechanism is critical for rendering this technology useful for ubiquitous biomedical applications. Here, supercapacitor technology is combined with flexible organic optoelectronics by integrating RuO2 into a donor-acceptor photovoltaic device architecture that facilitates efficient and safe photostimulation of neurons. Remarkably, high interfacial capacitance of RuO2 resulting from reversible redox reactions leads to more than an order-of-magnitude increase in the safe stimulation mechanism of capacitive charge transfer. The RuO2-enhanced photoelectrical response activates voltage-gated sodium channels of hippocampal neurons and elicits repetitive, low-light intensity, and high-success rate firing of action potentials. Double-layer capacitance together with RuO2-induced reversible faradaic reactions provide a safe stimulation pathway, which is verified via intracellular oxidative stress measurements. All-solution-processed RuO2-based biointerfaces are flexible, biocompatible, and robust under harsh aging conditions, showing great promise for building safe and highly light-sensitive next-generation neural interfaces.
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    Ruthenium-induced corneal collagen crosslinking under visible light
    (Assoc Research Vision Ophthalmology Inc, 2022) N/A; N/A; N/A; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; N/A; Department of Chemical and Biological Engineering; Yıldız, Erdost; Gülzar, Ayesha; Kaleli, Humeyra Nur; Nazeer, Muhammad Anwaar; Zibandeh, Noushin; Malik, Anjum Naeem; Taş, Ayşe Yıldız; Lazoğlu, İsmail; Şahin, Afsun; Kızılel, Seda; PhD Student; PhD Student; PhD Student; PhD Student; Researcher; PhD Student; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; Department of Chemical and Biological Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Health Sciences; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; N/A; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; School of Medicine; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 200905; 179391; 171267; 28376
    Corneal collagen crosslinking (CXL) is a commonly used minimally invasive surgical technique to prevent the progression of corneal ectasias, such as keratoconus. Unfortunately, riboflavin/UV-A light-based CXL procedures have not been successfully applied to all patients, and result in frequent complications, such as corneal haze and endothelial damage. We propose a new method for corneal crosslinking by using a Ruthenium (Ru) based water-soluble photoinitiator and visible light (430 nm). Tris(bipyridine)ruthenium(II) ([Ru(bpy)3]2+) and sodium persulfate (SPS) mixture covalently crosslinks free tyrosine, histidine, and lysine groups under visible light (400-450 nm), which prevents UV-A light-induced cytotoxicity in an efficient and time saving collagen crosslinking procedure. In this study, we investigated the effects of the Ru/visible blue light procedure on the viability and toxicity of human corneal epithelium, limbal, and stromal cells. Then bovine corneas crosslinked with ruthenium mixture and visible light were characterized, and their biomechanical properties were compared with the customized riboflavin/UV-A crosslinking approach in the clinics. Crosslinked corneas with a ruthenium-based CXL approach showed significantly higher young's modulus compared to riboflavin/UV-A light-based method applied to corneas. In addition, crosslinked corneas with both methods were characterized to evaluate the hydrodynamic behavior, optical transparency, and enzymatic resistance. In all biomechanical, biochemical, and optical tests used here, corneas that were crosslinked with ruthenium-based approach demonstrated better results than that of corneas crosslinked with riboflavin/ UV-A. This study is promising to be translated into a non-surgical therapy for all ectatic corneal pathologies as a result of mild conditions introduced here with visible light exposure and a nontoxic ruthenium-based photoinitiator to the cornea. STATEMENT OF SIGNIFICANCE: Keratoconus, one of the most frequent corneal diseases, could be treated with riboflavin and ultraviolet light-based photo-crosslinking application to the cornea of the patients. Unfortunately, this method has irreversible side effects and cannot be applied to all keratoconus patients. In this study, we exploited the photoactivation behavior of an organoruthenium compound to achieve corneal crosslinking. Ruthenium-based organic complex under visible light demonstrated significantly better biocompatibility and superior biomechanical results than riboflavin and ultraviolet light application. This study promises to translate into a new fast, efficient non-surgical therapy option for all ectatic corneal pathologies.
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    Ruthenium-induced corneal collagen crosslinking under visible light
    (Elsevier, 2022) N/A; N/A; N/A; N/A; N/A; N/A; N/A; Department of Mechanical Engineering; N/A; Department of Chemical and Biological Engineering; Gülzar, Ayesha; Yıldız, Erdost; Kaleli, Humeyra Nur; Nazeer, Muhammad Anwaar; Zibandeh, Noushin; Malik, Anjum Naeem; Taş, Ayşe Yıldız; Lazoğlu, İsmail; Şahin, Afsun; Kızılel, Seda; PhD Student; PhD Student; PhD Student; PhD Student; Researcher; PhD Student; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Department of Mechanical Engineering; Department of Chemical and Biological Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; N/A; Graduate School of Sciences and Engineering; School of Medicine; College of Engineering; School of Medicine; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 200905; 179391; 171267; 28376
    Corneal collagen crosslinking (CXL) is a commonly used minimally invasive surgical technique to prevent the progression of corneal ectasias, such as keratoconus. Unfortunately, riboflavin/UV-A light-based CXL procedures have not been successfully applied to all patients, and result in frequent complications, such as corneal haze and endothelial damage. We propose a new method for corneal crosslinking by using a Ruthenium (Ru) based water-soluble photoinitiator and visible light (430 nm). Tris(bipyridine)ruthenium(II) ([Ru(bpy)(3)](2+)) and sodium persulfate (SPS) mixture covalently crosslinks free tyrosine, histidine, and lysine groups under visible light (400-450 nm), which prevents UV-A light-induced cytotoxicity in an efficient and time saving collagen crosslinking procedure. In this study, we investigated the effects of the Ru/visible blue light procedure on the viability and toxicity of human corneal epithelium, limbal, and stromal cells. Then bovine corneas crosslinked with ruthenium mixture and visible light were characterized, and their biomechanical properties were compared with the customized riboflavin/UV-A crosslinking approach in the clinics. Crosslinked corneas with a ruthenium-based CXL approach showed significantly higher young's modulus compared to riboflavin/UV-A light-based method applied to corneas. In addition, crosslinked corneas with both methods were characterized to evaluate the hydrodynamic behavior, optical transparency, and enzymatic resistance. In all biomechanical, biochemical, and optical tests used here, corneas that were crosslinked with ruthenium-based approach demonstrated better results than that of corneas crosslinked with riboflavin/ UV-A. This study is promising to be translated into a non-surgical therapy for all ectatic corneal pathologies as a result of mild conditions introduced here with visible light exposure and a nontoxic ruthenium-based photoinitiator to the cornea. Statement of significance Keratoconus, one of the most frequent corneal diseases, could be treated with riboflavin and ultraviolet light-based photo-crosslinking application to the cornea of the patients. Unfortunately, this method has irreversible side effects and cannot be applied to all keratoconus patients. In this study, we exploited the photoactivation behavior of an organoruthenium compound to achieve corneal crosslinking. Ruthenium-based organic complex under visible light demonstrated significantly better biocompatibility and superior biomechanical results than riboflavin and ultraviolet light application. This study promises to translate into a new fast, efficient non-surgical therapy option for all ectatic corneal pathologies. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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    PublicationOpen Access
    Tissue-like optoelectronic neural interface enabled by PEDOT:PSS hydrogel for cardiac and neural stimulation
    (Wiley, 2022) Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; N/A; Han, Mertcan; Karaz, Selcan; Eren, Güncem Özgün; Doğru-Yüksel, Itır Bakış; Yıldız, Erdost; Kaleli, Humeyra Nur; Şenses, Erkan; Şahin, Afsun; Nizamoğlu, Sedat; Master Student; Master Student; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; Graduate School of Health Sciences; College of Engineering; School of Medicine; N/A; N/A; N/A; N/A; N/A; N/A; 280298; 171267; 130295
    Optoelectronic biointerfaces have made a significant impact on modern science and technology from understanding the mechanisms of the neurotransmission to the recovery of the vision for blinds. They are based on the cell interfaces made of organic or inorganic materials such as silicon, graphene, oxides, quantum dots, and ?-conjugated polymers, which are dry and stiff unlike a cell/tissue environment. On the other side, wet and soft hydrogels have recently been started to attract significant attention for bioelectronics because of its high-level tissue-matching biomechanics and biocompatibility. However, it is challenging to obtain optimal opto-bioelectronic devices by using hydrogels requiring device, heterojunction, and hydrogel engineering. Here, an optoelectronic biointerface integrated with a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS, hydrogel that simultaneously achieves efficient, flexible, stable, biocompatible, and safe photostimulation of cells is demonstrated. Besides their interfacial tissue-like biomechanics, ?34 kPa, and high-level biocompatibility, hydrogel-integration facilitates increase in charge injection amounts sevenfolds with an improved responsivity of 156 mA W?1, stability under mechanical bending , and functional lifetime over three years. Finally, these devices enable stimulation of individual hippocampal neurons and photocontrol of beating frequency of cardiac myocytes via safe charge-balanced capacitive currents. Therefore, hydrogel-enabled optoelectronic biointerfaces hold great promise for next-generation wireless neural and cardiac implants.
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    PublicationOpen Access
    Electrical stimulation of neurons with quantum dots via near-infrared light
    (American Chemical Society (ACS), 2022) Department of Electrical and Electronics Engineering; N/A; Karatüm, Onuralp; Kaleli, Humeyra Nur; Eren, Güncem Özgün; Şahin, Afsun; Nizamoğlu, Sedat; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Sciences and Engineering; Graduate School of Health Sciences; School of Medicine; College of Engineering; N/A; N/A; N/A; 171267; 130295
    Photovoltaic biointerfaces offer wireless and battery-free bioelectronic medicine via photomodulation of neurons. Near-infrared (NIR) light enables communication with neurons inside the deep tissue and application of high photon flux within the ocular safety limit of light exposure. For that, nonsilicon biointerfaces are highly demanded for thin and flexible operation. Here, we devised a flexible quantum dot (QD)-based photovoltaic biointerface that stimulates cells within the spectral tissue transparency window by using MR light (lambda = 780 nm). Integration of an ultrathin QD layer of 25 nm into a multilayered photovoltaic architecture enables transduction of NIR light to safe capacitive ionic currents that leads to reproducible action potentials on primary hippocampal neurons with high success rates. The biointerfaces exhibit low in vitro toxicity and robust photoelectrical performance under different stability tests. Our findings show that colloidal quantum dots can be used in wireless bioelectronic medicine for brain, heart, and retina.