Light-harvesting bio-nanomaterial using porous silicon and photosynthetic reaction center

Porous silicon microcavity (PSiMc) structures were used to immobilize the photosynthetic reaction center (RC) purified from the purple bacterium Rhodobacter sphaeroides R-26. Two different binding methods were compared by specular reflectance measurements. Structural characterization of PSiMc was performed by scanning electron microscopy and atomic force microscopy. The activity of the immobilized RC was checked by measuring the visible absorption spectra of the externally added electron donor, mammalian cytochrome c. PSi/RC complex was found to oxidize the cytochrome c after every saturating Xe flash, indicating the accessibility of specific surface binding sites on the immobilized RC, for the external electron donor. This new type of bio-nanomaterial is considered as an excellent model for new generation applications of silicon-based electronics and biological redox systems

Functional Nanohybrid Materials from Photosynthetic Reaction Center Proteins

Application of technical developments in biology and vice versa or biological samples in technology led to the development of new types of functional, so-called “biohybrid” materials. These types of materials can be created at any level of the biological organization from molecules through tissues and organs to the individuals. Macromolecules and/or molecular complexes, membranes in biology, are inherently good representatives of nanosystems since they fall in the range usually called “nano.” Nanohybrid materials provide the possibility to create functional bionanohybrid complexes which also led to new discipline called “nanobionics” in the literature and are considered as materials for the future. In this publication, the special characteristics of photosynthetic reaction center proteins, which are “nature’s solar batteries,” will be discussed in terms of their possible applications for creating functional molecular biohybrid materials

Carbon nanotubes quench singlet oxygen generated by photosynthetic reaction centers

Photosensitizers may convert molecular oxygen into reactive oxygen species (ROS) including, e.g., singlet oxygen (1O2), superoxide anion (O2-•), and hydroxyl radicals (•OH), chemicals with extremely high cyto- and potential genotoxicity. Photodynamic ROS reactions are determinative in medical photodynamic therapy (cancer treatment with externally added photosensitizers) and in reactions damaging the photosynthetic apparatus of plants (via internal pigments). The primary events of photosynthesis take place in the chlorophyll containing reaction center protein complex (RC), where the energy of light is converted into chemical potential. 1O2 is formed by both bacterial bacteriochlorophylls and plant RC triplet chlorophylls in high light and if the quenching of 1O2 is impaired. In plant physiology, reducing the formation of the ROS and thus lessening photooxidative membrane damage (including the RC protein) and increasing the efficiency of the photochemical energy conversion is of special interest. Carbon nanotubes, in artificial systems, are also known to react with singlet oxygen. To investigate the possibility of 1O2 quenching by carbon nanotubes in a biological system, we studied the effect of carbon nanotubes on 1O2 photogenerated by photosynthetic RCs purified from purple bacteria. 1,3-Diphenylisobenzofuran (DPBF), a dye responding to oxidation by 1O2 with absorption decrease at 420nm was used to measure 1O2 concentrations. 1O2 was produced either from a photosensitizer (methylene blue) or from triplet photosynthetic RCs and the antioxidant capacity of carbon nanotubes was assessed. Less 1O2 was detected by DPBF in the presence of carbon nanotubes, suggesting that these are potential quenchers of this ROS. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Real-Time Sensing of Hydrogen Peroxide by ITO/MWCNT/Horseradish Peroxidase Enzyme Electrode

The accurate and sensitive determination of H2O2 is very important in many cases because it is a product of reactions catalysed by several oxidase enzymes in living cells and it is essential in environmental and pharmaceutical analyses. The fabrication of enzyme protein activity based biosensors is a very promising way for this purpose because the function of biological molecules is very specific, sensitive, and selective. Horseradish peroxidase (HRP) is the most commonly used enzyme for H2O2 detection because it can oxidize hydrogen atoms and, for example, xenobiotics in the presence of H2O2. In order to define the limit of detection (LOD) of H2O2 we made calibrations with guaiacol and amplex red (AR), which are hydrogen donors of HRP. The accumulation of the reaction products, tetraguaiacol, and resorufin, respectively, then can be easily detected by absorption or emission (fluorescence) spectroscopy. In our experiments an enzyme electrode was fabricated from ITO (indium tin oxide), functionalized multiwalled carbon nanotubes (f-MWCNTs), and HRP. Although the enzyme activity was smaller by about two orders of magnitude when the enzyme was bound to the f-MWCNTs (ca. 10−2 M H2O2/(M HRP·sec) compared to ca. 2 M H2O2/(M HRP·sec) and 5 M H2O2/(M HRP·sec) with AR and guaiacol in buffer solution), LOD of the H2O2 decomposition was about 6 pM H2O2/sec and 10 pM H2O2/sec in the case of AR and guaiacol, respectively

Wirelessly powered drug-free and anti-infective smart bandage for chronic wound care

We present a wirelessly powered ultraviolet-C (UVC) radiation-based disinfecting bandage for sterilization and treatment in chronic wound care and management. The bandage contains embedded low-power UV light-emitting diodes (LEDs) in the 265 to 285 nm range with the light emission controlled via a microcontroller. An inductive coil is seamlessly concealed in the fabric bandage and coupled with a rectifier circuit to enable 6.78 MHz wireless power transfer (WPT). The maximum WPT efficiency of the coils is 83% in free space and 75% on the body at a coupling distance of 4.5 cm. Measurements show that the UVC LEDs are emitting radiant power of about 0.6 mW and 6.8 mW with and without fabric bandage, respectively, when wirelessly powered. The ability of the bandage to inactivate microorganisms was examined in a laboratory which shows that the system can effectively eradicate Gram-negative bacteria, Pseudoalteromonas sp. D41 strain, on surfaces in six hours. The proposed smart bandage system is low-cost, battery-free, flexible and can be easily mounted on the human body and, therefore, shows great promise for the treatment of persistent infections in chronic wound care