Browsing by Subject "Biosensing"

Now showing 1 - 9 of 9

Open Access
Advances in biomimetic systems for molecular recognition and biosensing
(MDPI Multidisciplinary Digital Publishing Institute, 2020-05) Saylan, Y.; Erdem, Özgecan; İnci, Fatih; Denizli, A.
Understanding the fundamentals of natural design, structure, and function has pushed the limits of current knowledge and has enabled us to transfer knowledge from the bench to the market as a product. In particular, biomimicry—one of the crucial strategies in this respect—has allowed researchers to tackle major challenges in the disciplines of engineering, biology, physics, materials science, and medicine. It has an enormous impact on these fields with pivotal applications, which are not limited to the applications of biocompatible tooth implants, programmable drug delivery systems, biocompatible tissue scaffolds, organ-on-a-chip systems, wearable platforms, molecularly imprinted polymers (MIPs), and smart biosensors. Among them, MIPs provide a versatile strategy to imitate the procedure of molecular recognition precisely, creating structural fingerprint replicas of molecules for biorecognition studies. Owing to their affordability, easy-to-fabricate/use features, stability, specificity, and multiplexing capabilities, host-guest recognition systems have largely benefitted from the MIP strategy. This review article is structured with four major points: (i) determining the requirement of biomimetic systems and denoting multiple examples in this manner; (ii) introducing the molecular imprinting method and reviewing recent literature to elaborate the power and impact of MIPs on a variety of scientific and industrial fields; (iii) exemplifying the MIP-integrated systems, i.e., chromatographic systems, lab-on-a-chip systems, and sensor systems; and (iv) closing remarks.
Open Access
Conjugated polymer nanoparticles
(2010) Tuncel, D.; Demir, Hilmi Volkan
Conjugated polymer nanoparticles are highly versatile nano-structured materials that can potentially find applications in various areas such as optoelectronics, photonics, bio-imaging, bio-sensing and nanomedicine. Their straightforward synthesis in desired sizes and properties, biocompatibility and non-toxicity make these materials highly attractive for the aforementioned applications. This feature article reviews the recent developments in the synthesis, characterization, properties and application of these exciting nanostructured materials.
Open Access
High-figure-of-merit biosensing and enhanced excitonic absorption in an mos2-integrated dielectric metasurface
(MDPI, 2023-02-01) Hajian, H.; Rukhlenko, I. D.; Bradley, A. L.; Özbay, Ekmel
Among the transitional metal dichalcogenides (TMDCs), molybdenum disulfide (MoS2) is considered an outstanding candidate for biosensing applications due to its high absorptivity and amenability to ionic current measurements. Dielectric metasurfaces have also emerged as a powerful platform for novel optical biosensing due to their low optical losses and strong near-field enhancements. Once functionalized with TMDCs, dielectric metasurfaces can also provide strong photon–exciton interactions. Here, we theoretically integrated a single layer of MoS2 into a CMOS-compatible asymmetric dielectric metasurface composed of TiO2 meta-atoms with a broken in-plane inversion symmetry on an SiO2 substrate. We numerically show that the designed MoS2-integrated metasurface can function as a high-figure-of-merit ((Formula presented.)) van der Waals-based biosensor due to the support of quasi-bound states in the continuum. Moreover, owing to the critical coupling of the magnetic dipole resonances of the metasurface and the A exciton of the single layer of MoS2, one can achieve a (Formula presented.) enhanced excitonic absorption by this two-port system. Therefore, the proposed design can function as an effective biosensor and is also practical for enhanced excitonic absorption and emission applications. © 2023 by the authors.
Open Access
High-throughput, high-resolution interferometric light microscopy of biological nanoparticles
(American Chemical Society, 2020-01) Yurdakul, C.; Avcı, O.; Matlock, A.; Devaux, A. J.; Quintero, M. V.; Özbay, Ekmel; Davey, R. A.; Connor, J. H.; Karl, W. C.; Tian, L.; Ünlü, M. Selim
Label-free, visible light microscopy is an indispensable tool for studying biological nanoparticles (BNPs). However, conventional imaging techniques have two major challenges: (i) weak contrast due to low-refractive-index difference with the surrounding medium and exceptionally small size and (ii) limited spatial resolution. Advances in interferometric microscopy have overcome the weak contrast limitation and enabled direct detection of BNPs, yet lateral resolution remains as a challenge in studying BNP morphology. Here, we introduce a wide-field interferometric microscopy technique augmented by computational imaging to demonstrate a 2-fold lateral resolution improvement over a large field-of-view (>100 × 100 μm2 ), enabling simultaneous imaging of more than 104 BNPs at a resolution of ∼150 nm without any labels or sample preparation. We present a rigorous vectorial-optics-based forward model establishing the relationship between the intensity images captured under partially coherent asymmetric illumination and the complex permittivity distribution of nanoparticles. We demonstrate high-throughput morphological visualization of a diverse population of Ebola virus-like particles and a structurally distinct Ebola vaccine candidate. Our approach offers a low-cost and robust label-free imaging platform for high-throughput and high-resolution characterization of a broad size range of BNPs.
Open Access
In situ synthesis of biomolecule encapsulated gold-cross-linked poly(ethylene glycol) nanocomposite as biosensing platform: A model study
(Elsevier BV, 2010) Odaci, D.; Kahveci, M.U.; Sahkulubey, E.L.; Ozdemir, C.; Uyar, Tamer; Timur, S.; Yagci Y.
In situ synthesis of poly(ethylene glycol) (PEG) hydrogels containing gold nanoparticles(AuNPs) and glucose oxidase (GOx) enzyme by photo-induced electron transfer process was reported here and applied in electrochemical glucose biosensing as the model system. Newly designed bionanocomposite matrix by simple one-step fabrication offered a good contact between the active site of the enzyme and AuNPs inside the network that caused the promotion in the electron transfer properties that was evidenced by cyclic voltammetryas well as higher amperometric biosensing responses in comparing with response signals obtained from the matrix without AuNPs. As well as some parameters important in the optimization studies such as optimum pH, enzyme loading and AuNP amount, the analytical characteristics of the biosensor (AuNP/GOx) were examined by the monitoring of chronoamperometric response due to the oxygen consumption through the enzymatic reaction at − 0.7 V under optimized conditions at sodium acetate buffer (50 mM, pH 4.0) and the linear graph was obtained in the range of 0.1–1.0 mM glucose. The detection limit (LOD) of the biosensor was calculated as 0.06 mM by using the signal to noise ratio of 3. Moreover, the presence of AuNPs was visualized by TEM. Finally, the biosensor was applied for glucose analysis for some beverages and obtained data were compared with HPLC as the reference method to test the possible matrix effect due to the nature of the samples.
Open Access
Investigation of dual-narrowband plasmonic perfect absorbers at visible frequencies for biosensing
(2019-12) Ali, Farhan
Since the introduction of first plasmonic perfect absorber (PA) in early 2008 by Landy et al., numerous studies have demonstrated their superior optical performance in frequencies ranging from terahertz to visible region of electromagnetic spectrum. In the literature broadband PAs are studied in more detail compared to narrowband PAs as their large absorption bandwidths make them a prime candidate for energy harvesting applications or security and defense. Recently scientists have shown a great interest in designing narrowband PAs by controlling the optical losses of the plasmonic materials as the narrowband resonances with a high quality-factor is particularly important for label-free biosensing. However, given the lossy optical properties of metals, this task has been challenging and requires delicate investigation and parameter control in contrast to broadband perfect absorbers. In this research, we numerically studied and experimentally fabricated a narrow-band plasmonic perfect absorber based on a metal-insulator-metal con- figuration. We analyzed the origin of perfect absorption for our proposed system and investigated the parameters that effect the optical properties. The purposed plasmonic structure comes up with a dual narrow-band absorption peaks at visible and near-infrared region of electromagnetic spectrum with near unity absorption e ciency. The physical origin of these absorption peaks is shown to be the excitation of propagating and localized surface plasmon resonances at certain individual frequencies, that leads to impedance matching and critical coupling when certain conditions are satisfied. Finally, we analyzed the sensing capabilities of PA by embedding nanostructure into different background refractive index, resulting in sensitivity of 500 nm/RIU, making such a platform suitable for biosensing and spectroscopic applications. This work analyzes the perfect absorption phenomena in visible frequencies in detail and will be a go to guide for researchers in the perfect absorber community.
Open Access
SILVER nano-cylinders designed by EBL used as label free LSPR nano-biosensors
(SPIE, 2011) Cinel, Neval A.; Bütün, Serkan; Özbay, Ekmel
Localized Surface Plasmon Resonance (LSPR) is based on the electromagnetic-field enhancement of metallic nano-particles. It is observed at the metal-dielectric interface and the resonance wavelength can be tuned by the size, shape, and periodicity of the metallic nanoparticles and the surrounding dielectric environment. This makes LSPR a powerful candidate in bio-sensing. In the present work, the size and period dependency of the LSPR wavelength was studied through simulations and fabrications. The surface functionalization, that transforms the surface into a sensing platform was done and verified. Finally, the concentration dependency of the LSPR shifts was observed. All the measurements were done by a transmission set-up. The study is at an early stage, however results are promising. The detection of specific bacteria species can be made possible with such a detection method. © 2011 SPIE.
Open Access
Tunable fano‐resonant metasurfaces on a disposable plastic‐template for multimodal and multiplex biosensing
(Wiley-VCH Verlag, 2020) Ahmed, R.; Özen, M. Ö.; Karaaslan, M. G.; Prator, C. A.; Thanh, C.; Kumar, S.; Torres, L.; Iyer, N.; Munter, S.; Southern, S.; Henrich, T. J.; İnci, Fatih; Demirci, U.
Metasurfaces are engineered nanostructured interfaces that extend the photonic behavior of natural materials, and they spur many breakthroughs in multiple fields, including quantum optics, optoelectronics, and biosensing. Recent advances in metasurface nanofabrication enable precise manipulation of light–matter interactions at subwavelength scales. However, current fabrication methods are costly and time‐consuming and have a small active area with low reproducibility due to limitations in lithography, where sensing nanosized rare biotargets requires a wide active surface area for efficient binding and detection. Here, a plastic‐templated tunable metasurface with a large active area and periodic metal–dielectric layers to excite plasmonic Fano resonance transitions providing multimodal and multiplex sensing of small biotargets, such as proteins and viruses, is introduced. The tunable Fano resonance feature of the metasurface is enabled via chemical etching steps to manage nanoperiodicity of the plastic template decorated with plasmonic layers and surrounding dielectric medium. This metasurface integrated with microfluidics further enhances the light–matter interactions over a wide sensing area, extending data collection from 3D to 4D by tracking real‐time biomolecular binding events. Overall, this work resolves cost‐ and complexity‐related large‐scale fabrication challenges and improves multilayer sensitivity of detection in biosensing applications.
Open Access
Ultra high quality factor microtoroidal optical resonators in label - free biosensing applications with high sensitivity and selectivity
(2016-11) Tören, Pelin
Whispering - Gallery - Mode type microresonators provide great opportunities for label - free biosensing, allowing detections down to single - molecule levels. Microtoroids as optical resonators are quite sensitive and preferable biosensors due to their high quality factors. However, their surface design should be carefully considered for a selective biodetection. For this purpose, studies on WGM type biosensing for DNA, RNA and protein detections using various surface modifications are herein summarized. Over and above, this thesis mainly focuses on the microfabrication and surface modification of the microtoroids for various selective biosensing purposes such as antigen detection in complex media or detecting single base pair DNA alterations in buffer. With this regard, the developed microtoroid surface modification for dual characteristics (anti - fouling property and bioconjugability) is described in detail. The dual surface approach, used for selective Interleukin - 2 and Exotoxin - A detections in complex media, is applied to the microtoroids. Biosensing in complex media is a challeging task to perform unless the calibration approach is used. To overcome this challenge the suggested surface modification approach for nano - molar level detections is explained in detail. Besides, a novel surface modification approach for a selective single - stranded DNA detection based on discriminating single base pairs is portrayed as well.