Immobilization of Functional Light Antenna Structures Derived from the Filamentous Green Bacterium Chloroflexus aurantiacus

Abstract

The integration of highly efficient, natural photosynthetic light antenna structures into engineered systems while their biophotonic capabilities are maintained has been an elusive goal in the design of biohybrid photonic devices. In this study, we report a novel technique to covalently immobilize nanoscaled bacterial light antenna structures known as chlorosomes from Chloroflexus aurantiacus on both conductive and nonconductive glass while their energy transducing functionality was maintained. Chlorosomes without their reaction centers (RCs) were covalently immobilized on 3-aminoproyltriethoxysilane (APTES) treated surfaces using a glutaraldehyde linker. AFM techniques verified that the chlorosomes maintained their native ellipsoidal ultrastructure upon immobilization. Results from absorbance and fluorescence spectral analysis (where the Stokes shift to 808/810 nm was observed upon 470 nm blue light excitation) in conjunction with confocal microscopy confirm that the functional integrity of immobilized chlorosomes was also preserved. In addition, experiments with electrochemical impedance spectroscopy (EIS) suggested that the presence of chlorosomes in the electrical double layer of the electrode enhanced the electron transfer capacity of the electrochemical cell. Further, chronoamperometric studies suggested that the reduced form of the Bchl- c pigments found within the chlorosome modulate the conduction properties of the electrochemical cell, where the oxidized form of Bchl- c pigments impeded any current transduction at a bias of 0.4 V within the electrochemical cell. The results therefore demonstrate that the intact chlorosomes can be successfully immobilized while their biophotonic transduction capabilities are preserved through the immobilization process. These findings indicate that it is feasible to design biophotonic devices incorporating fully functional light antenna structures, which may offer significant performance enhancements to current silicon-based photonic devices for diverse technological applications ranging from CCD devices used in retinal implants to terrestrial and space fuel cell applications.

Electrospray-assisted characterization and deposition of chlorosomes to fabricate a biomimetic light-harvesting device

“…4,12,13 The second peak most probably represents chlorosome agglomerates and impurities of cell fragments left over from the isolation procedure. The chlorosomes are known to have an aspect ratio (b) of approximately 3.0, 4,12,14 and thus D m represents a diameter equivalent to a spherical particle with the same electrical mobility as the chlorosomes. Nevertheless, because the b of the chlorosomes is relatively low and the electric field in the DMA was less than 1000 V cm À1 the chlorosomes, which are ellipsoidal particles, were thought to be randomly oriented in the DMA.…”

“…The dimensions of the chlorosomes obtained with the electrospray-assisted and DLS techniques, without the implementation of microscopy images, are in very good agreement with previous literature reports. 4,6,13,14,16 Both methods, which complement other techniques, can be coupled in the size characterization of nonspherical biological particles. Furthermore, the average number of elementary charges carried by electrosprayed spherical particles is known to scale with the square of the particle size, 17 which is proportional to the particle surface area.…”

“…18 The difficulty in linking the BChl c oligomers to the surface of the semiconductor material demonstrates that the electrospray of whole chlorosomes represents a potential approach to avoid both the formation of large amount of monomeric BChl c during deposition and the additional steps for surfactant removal. 14,19…”

Reactive amine surfaces for biosensor applications, prepared by plasma-enhanced chemical vapour modification of polyolefin materials

“…In this context, 3-(aminopropyl) triethoxysilane (APTES), commonly used for liquid-phase deposition of amine functional groups (Moon 1997, Qian 1999, Gu and Cheng 2008, Simon 2002, Sridharan 2008) is expected to present all the requirements needed. Previous investigations of chemical vapour deposition (CVD) on silicon substrate at elevated temperatures highlighted its suitability (Arroyo-Hernandez 2006).…”

Biofuel cells Based on the Immobilization of Photosynthetically Active Bioentities

“…The high-energy electrons produced in the photosystems could be potentially transferred to electrodes through suitable endogenous or exogenous electron transfer mediators to generate a photocurrent. To realize such electrochemical devices, some studies have been performed to investigate the potential of protein complexes, [28,29] thylakoid membranes, [30] chloroplasts, [31] and even photosynthetic living cells [32] to generate electrical power. For instance, photosynthetically active biofuel cells have been initially constructed by coupling hydrogen produced by photosynthetic microorganisms with a metal electrocatalyst.…”