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Kraft FA, Lehmann S, Di Maria C, Joksch L, Fitschen-Östern S, Fuchs S, Dell'Olio F, Gerken M. Intensity-Based Camera Setup for Refractometric and Biomolecular Sensing with a Photonic Crystal Microfluidic Chip. BIOSENSORS 2023; 13:687. [PMID: 37504086 PMCID: PMC10377058 DOI: 10.3390/bios13070687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 06/21/2023] [Accepted: 06/25/2023] [Indexed: 07/29/2023]
Abstract
Label-free sensing is a promising approach for point-of-care testing devices. Among optical transducers, photonic crystal slabs (PCSs) have positioned themselves as an inexpensive yet versatile platform for label-free biosensing. A spectral resonance shift is observed upon biomolecular binding to the functionalized surface. Commonly, a PCS is read out by a spectrometer. Alternatively, the spectral shift may be translated into an intensity change by tailoring the system response. Intensity-based camera setups (IBCS) are of interest as they mitigate the need for postprocessing, enable spatial sampling, and have moderate hardware requirements. However, they exhibit modest performance compared with spectrometric approaches. Here, we show an increase of the sensitivity and limit of detection (LOD) of an IBCS by employing a sharp-edged cut-off filter to optimize the system response. We report an increase of the LOD from (7.1 ± 1.3) × 10-4 RIU to (3.2 ± 0.7) × 10-5 RIU. We discuss the influence of the region of interest (ROI) size on the achievable LOD. We fabricated a biochip by combining a microfluidic and a PCS and demonstrated autonomous transport. We analyzed the performance via refractive index steps and the biosensing ability via diluted glutathione S-transferase (GST) antibodies (1:250). In addition, we illustrate the speed of detection and demonstrate the advantage of the additional spatial information by detecting streptavidin (2.9 µg/mL). Finally, we present the detection of immunoglobulin G (IgG) from whole blood as a possible basis for point-of-care devices.
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Affiliation(s)
- Fabio Aldo Kraft
- Integrated Systems and Photonics, Faculty of Engineering, Kiel University, 24118 Kiel, Germany
- Kiel Nano, Surface and Interface Science KiNSIS, Kiel University, 24118 Kiel, Germany
| | - Stefanie Lehmann
- Integrated Systems and Photonics, Faculty of Engineering, Kiel University, 24118 Kiel, Germany
| | - Carmela Di Maria
- Integrated Systems and Photonics, Faculty of Engineering, Kiel University, 24118 Kiel, Germany
- Department of Electrical and Information Engineering, Polytechnic University of Bari, 70126 Bari, Italy
| | - Leonie Joksch
- Integrated Systems and Photonics, Faculty of Engineering, Kiel University, 24118 Kiel, Germany
| | - Stefanie Fitschen-Östern
- Experimental Trauma Surgery, Department of Trauma Surgery and Orthopedics, University Medical Center Schleswig-Holstein, Kiel University, 24105 Kiel, Germany
| | - Sabine Fuchs
- Experimental Trauma Surgery, Department of Trauma Surgery and Orthopedics, University Medical Center Schleswig-Holstein, Kiel University, 24105 Kiel, Germany
| | - Francesco Dell'Olio
- Department of Electrical and Information Engineering, Polytechnic University of Bari, 70126 Bari, Italy
| | - Martina Gerken
- Integrated Systems and Photonics, Faculty of Engineering, Kiel University, 24118 Kiel, Germany
- Kiel Nano, Surface and Interface Science KiNSIS, Kiel University, 24118 Kiel, Germany
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Kraft FA, Baur H, Bommer M, Latz A, Fitschen-Oestern S, Fuchs S, Gerken M. Label-free multiplex sensing from buffer and immunoglobulin G sensing from whole blood with photonic crystal slabs using angle-tuning of an optical interference filter. BIOMEDICAL OPTICS EXPRESS 2023; 14:2293-2310. [PMID: 37206136 PMCID: PMC10191658 DOI: 10.1364/boe.489138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 03/31/2023] [Accepted: 04/16/2023] [Indexed: 05/21/2023]
Abstract
Direct detection of biomarkers from unpurified whole blood has been a challenge for label-free detection platforms, such as photonic crystal slabs (PCS). A wide range of measurement concepts for PCS exist, but exhibit technical limitations, which render them unsuitable for label-free biosensing with unfiltered whole blood. In this work, we single out the requirements for a label-free point-of-care setup based on PCS and present a wavelength selecting concept by angle tuning of an optical interference filter, which fulfills these requirements. We investigate the limit of detection (LOD) for bulk refractive index changes and obtain a value of 3.4 E-4 refractive index units (RIU). We demonstrate label-free multiplex detection for different types of immobilization entities, including aptamers, antigens, and simple proteins. For this multiplex setup we detect thrombin at a concentration of 6.3 µg/ml, antibodies of glutathione S-transferase (GST) diluted by a factor of 250, and streptavidin at a concentration of 33 µg/ml. In a first proof of principle experiment, we demonstrate the ability to detect immunoglobulins G (IgG) from unfiltered whole blood. These experiments are conducted directly in the hospital without temperature control of the photonic crystal transducer surface or the blood sample. We set the detected concentration levels into a medical frame of reference and point out possible applications.
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Affiliation(s)
- Fabio A. Kraft
- Integrated Systems and Photonics, Faculty of Engineering,
Kiel University, Germany
- Kiel Nano, Surface and Interface Science KiNSIS,
Kiel University, Germany
| | | | | | - Andreas Latz
- Integrated Systems and Photonics, Faculty of Engineering,
Kiel University, Germany
- Novatec Immundiagnostica GmbH, Dietzenbach, Germany
| | | | - Sabine Fuchs
- Kiel Nano, Surface and Interface Science KiNSIS,
Kiel University, Germany
- University Hospital Schleswig-Holstein, Kiel University, Germany
| | - Martina Gerken
- Integrated Systems and Photonics, Faculty of Engineering,
Kiel University, Germany
- Kiel Nano, Surface and Interface Science KiNSIS,
Kiel University, Germany
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Kraft FA, Harwardt K, Schardt J, Nowotka D, Gerken M. Suppressing the mechanochromism of flexible photonic crystals. OPTICS EXPRESS 2023; 31:6281-6295. [PMID: 36823888 DOI: 10.1364/oe.477189] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
Photonic crystal slabs (PCS) are a promising platform for optical biosensing. Yet, flexible applications based on PCS for biosensing have been limited, as the mechanical properties influence the optical ones. Here, we show the suppression of the mechanochromism effect for flexible PCS. We obtained flexible photonic crystal slabs by sputtering of a dielectric 100 nm Nb2O5 high refractive index layer onto a flexible nanostructured polydimethylsiloxane (PDMS) substrate with 370 nm grating period. The PCS exhibit a guided mode resonance at around 650 nm. We demonstrate that these flexible photonic crystal slabs show less than 0.5 nm resonance shift for 4% strain and call them stabilized PCS (sPCS). We compare this to a resonance shift of ∼21 nm for ∼4% strain of a flexible photonic crystal with a flexible nanoparticle high index layer (mechanochromatic PCS, mPCS). This high resonance shift is expected from the Bragg equations, where 4% grating period change correspond to approximately 4% change of the resonance wavelength (i.e., ∼26 nm at a resonance wavelength of 650 nm), if changes in the mode effective refractive index are neglected. In a stretch series we obtain color-to-strain dependencies of 4.79 nm/% strain for mPCS and 0.11 nm/% strain for our stabilized sPCS. We analyze the suppression of the mechanochromism with detailed microscopy results. We observe that fissures and fractures form in the rigid waveguiding layer of the sPCS upon mechanical stress. An algorithm based on Holistically-Nested Edge Detection (HED) is used for automated counting of cracks. Rigid photonic crystal cells with sizes on the order of 10 µm to 100 µm are formed that explain the stable optical properties. Even more stable optical properties with less than 0.03 nm wavelength shift per 1% strain are demonstrated for sPCS with an additional dielectric 100 nm SiO2 low index layer beneath the Nb2O5 waveguide layer decoupling the waveguide further from the flexible PDMS substrate.
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