Fluorescence and electron transfer of Limnospira indica functionalized biophotoelectrodes
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-08-21 |
| Journal | Photosynthesis Research |
| Authors | Nikolay V. Ryzhkov, Nora Colson, Essraa Ahmed, Paulius Pobedinskas, Ken Haenen |
| Institutions | Belgian Nuclear Research Centre, Swiss Federal Laboratories for Materials Science and Technology |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Core Technology Integration: Live Limnospira indica (cyanobacteria) were successfully integrated into biophotoelectrodes (BPECs) using Boron-Doped Diamond (BDD) as the current collector, immobilized within either Agar hydrogel or conductive PEDOT:PSS matrices.
- Enhanced Efficiency: The maximum quantum yield (Fv/Fm) of the cyanobacteria increased significantly, rising from approximately 0.3 (in mediator-free agar) to 0.45-0.49 when embedded in a conductive matrix (PEDOT:PSS or Agar + [Fe(CN)6]4- mediator).
- Conductivity Impact: Increased matrix conductivity (via PEDOT:PSS or mediator addition) facilitates extracellular electron transport (EET), leading to higher light utilization efficiency (LUE) and promoting the reopening of Photosystem II (PSII) reaction centers.
- Polarization Mitigation: The negative influence of external electrical polarization (tested at ±0.6 V vs Ag/AgCl) on photosynthetic performance diminishes as the matrix conductivity increases.
- Low-Light Performance: The light utilization coefficient (α), critical for light-limited conditions, improved from 0.20 (Agar) to 0.25 (PEDOT:PSS), confirming superior performance in conductive systems under low light.
- Monitoring Method: Pulse-Amplitude-Modulation (PAM) fluorometry was successfully integrated with chronoamperometry to provide non-invasive, real-time monitoring of the physiological state of the photosynthetic apparatus under electrical bias.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| BDD Film Thickness | 180 | nm | Deposited on fused silica substrates. |
| BDD Growth Method | MWPECVD | N/A | Microwave Plasma Enhanced Chemical Vapor Deposition. |
| BDD Growth Temperature | 730 | °C | Monitored during growth. |
| Microwave Power | 4000 | W | Used during BDD film growth. |
| Reactor Pressure | 40 | Torr | Used during BDD film growth. |
| Methane Concentration | 1 | % | In CH4/H2/B(CH3)3 plasma. |
| B/C Ratio | 20000 | ppm | Boron to Carbon ratio (using TMB). |
| Applied Potential Range | -0.6 to +0.6 | V | Versus Ag/AgCl reference electrode. |
| Max Quantum Yield (Fv/Fm) | 0.45 - 0.49 | N/A | Achieved in conductive matrices. |
| Baseline Quantum Yield (Fv/Fm) | 0.3 | N/A | Mediator-free agar hydrogel system. |
| Light Utilization Coeff. (α) | 0.25 | N/A | PEDOT:PSS system (light-limited conditions). |
| Light Utilization Coeff. (α) | 0.20 | N/A | Agar system (light-limited conditions). |
| Excitation Wavelength | 630 | nm | Used for Chl a fluorescence excitation. |
| Cell Immobilization Area | 1 | cm2 | Constrained area on BDD electrode surface. |
Key Methodologies
Section titled âKey Methodologiesâ- BDD Substrate Preparation: Fused silica substrates (40 x 10 mm) were cleaned using O2 gas discharge plasma. The plasma process involved biasing the samples negatively at 424 V under 30 sccm O2 flow at 5 mTorr pressure for 3 minutes.
- Diamond Seeding: Substrates were seeded by drop-casting a water-based colloidal suspension of ultra-dispersed detonation nano-diamond (7 nm size, 0.267 g/L), followed by spinning at 4000 rpm and flushing with deionized water.
- BDD Film Synthesis: 180 nm thick BDD films were grown using MWPECVD with CH4/H2/B(CH3)3 plasma. Gas flows were 5/395/100 sccm, resulting in 1% CH4 concentration and 20000 ppm B/C ratio. Process conditions were 4000 W power, 40 Torr pressure, and 730 °C substrate temperature.
- Cyanobacteria Cultivation: Axenic L. indica PCC 8005 cultures were grown in Zarroukâs medium at 30 °C, 100 rpm, and 0.5 mW/cm2 white light illumination.
- Immobilization Matrix Preparation: Cells were harvested and resuspended in either 0.75% melted agar (at 50 °C, optionally containing 100 mM [Fe(CN)6]4- mediator) or 0.5-1% PEDOT:PSS solution.
- Biophotoelectrode Assembly: 10 ”L of the cell suspension/matrix mixture was drop-casted onto the BDD electrode surface (1 cm2 area) and allowed to solidify (agar) or dry (PEDOT:PSS).
- Electrochemical/Fluorescence Measurement: A three-electrode setup was used (BDD/biofilm WE, Pt CE, Ag/AgCl RE) in Phosphate-Buffered Saline (PBS). A potentiostat applied constant electrical biases (0 V, +0.6 V, -0.6 V) while a MICROFIBER-PAM fluorometer simultaneously measured variable chlorophyll a fluorescence kinetics.
Commercial Applications
Section titled âCommercial Applicationsâ- Sustainable Energy Conversion (Biophotovoltaics): Utilizing the BDD/cyanobacteria system for direct conversion of solar energy into electrical power, offering a self-repairing and potentially long-term operational energy source.
- Biosensing and Bioelectronics: Developing robust, chemically inert BDD-based platforms for biosensors that monitor the physiological state (photosynthetic efficiency) of microorganisms in real-time under various environmental or electrical stimuli.
- Extraterrestrial Life Support Systems: Leveraging the radiation robustness of L. indica (as highlighted in the paper) and the stability of BDD for energy generation and oxygen production in closed-loop systems for space exploration.
- Advanced Water Treatment: Employing BDD electrodes for electrochemical processes (due to their wide potential window and chemical inertness) combined with photosynthetic organisms for enhanced, energy-efficient remediation and conversion systems.
- Conductive Polymer Composites: Application of PEDOT:PSS as a biocompatible, translucent conductive matrix for interfacing biological systems with electronics, relevant for flexible bioelectronics and medical devices.