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.

Porous silicon pillar structures/photosynthetic reaction centre protein hybrid for bioelectronic applications.

Photosynthetic biomaterials have attracted considerable attention at different levels of the biological organisation, from molecules to the biosphere, due to a variety of artificial application possibilities. During photosynthesis, the first steps of the conversion of light energy into chemical energy take place in a pigment-protein complex, called reaction centre (RC). In our experiments photosynthetic reaction centre protein, purified from Rhodobacter sphaeroides R-26 purple bacteria, was bound to porous silicon pillars (PSiP) after the electropolymerisation of aniline onto the surface. This new type of biohybrid material showed remarkable photoactivity in terms of measured photocurrent under light excitation in an electrochemical cell. The photocurrent was found to increase considerably after the addition of ubiquinone (UQ-0), an e--acceptor mediator of the RC. The photoactivity of the complex was found to decrease by the addition of terbutryn, the chemical which inhibits the e--transport on the acceptor side of the RC. In addition to the generation of sizeable light-induced photocurrents, using the PSiP/RC photoactive hybrid nanocomposite material, the system was found to be sensitive towards RC inhibitors and herbicides. This highly ordered patterned 3D structure opens new solution for designing low-power (bio-)optoelectronic, biophotonic and biosensing devices.

Detection of Singlet Oxygen Formation inside Photoactive Biohybrid Composite Material.

Photosynthetic reaction center proteins (RCs) are the most efficient light energy converter systems in nature. The first steps of the primary charge separation in photosynthesis take place in these proteins. Due to their unique properties, combining RCs with nano-structures promising applications can be predicted in optoelectronic systems. In the present work RCs purified from Rhodobacter sphaeroides purple bacteria were immobilized on multiwalled carbon nanotubes (CNTs). Carboxyl-and amine-functionalised CNTs were used, so different binding procedures, physical sorption and chemical sorption as well, could be applied as immobilization techniques. Light-induced singlet oxygen production was measured in the prepared photoactive biocomposites in water-based suspension by histidine mediated chemical trapping. Carbon nanotubes were applied under different conditions in order to understand their role in the equilibration of singlet oxygen concentration in the suspension. CNTs acted as effective quenchers of ¹O2 either by physical (resonance) energy transfer or by chemical (oxidation) reaction and their efficiency showed dependence on the diffusion distance of ¹O2.

Sensing photosynthetic herbicides in an electrochemical flow cell.

Specific inhibitory reactions of herbicides with photosynthetic reaction centers bound to working electrodes were monitored in a conventional electrochemical cell and a newly designed microfluidic electrochemical flow cell. In both cases, the bacterial reaction centers were bound to a transparent conductive metal oxide, indium-tin-oxide, electrode through carbon nanotubes. In the conventional cell, photocurrent densities of up to a few µA/cm2 could be measured routinely. The photocurrent could be blocked by the photosynthetic inhibitor terbutryn (I 50 = 0.38 ± 0.14 µM) and o-phenanthroline (I 50 = 63.9 ± 12.2 µM). The microfluidic flow cell device enabled us to reduce the sample volume and to simplify the electrode arrangement. The useful area of the electrodes remained the same (ca. 2 cm2), similar to the classical electrochemical cell; however, the size of the cell was reduced considerably. The microfluidic flow control enabled us monitoring in real time the binding/unbinding of the inhibitor and cofactor molecules at the secondary quinone site.

Assessing the capacity of zero valent iron nanofluids to remediate NAPL-polluted porous media.

A variety of aqueous suspensions (nanofluids) of zero-valent nano-particles (nZVI) are prepared by wet chemistry techniques, their stability and longevity is evaluated by physic-chemical methods of characterization, and their reactivity toward the dechlorination of per-chloro-ethylene (PCE) is examined with tests in batch reactors. For assessing the mobility, longevity and reactivity of nZVI suspensions (nanofluids), under flow-through conditions, visualization multiphase flow and transport tests are performed on a glass-etched pore network. The nZVI breakthrough curves are constructed by measuring the transient variation of the iron concentration in the effluent with atomic absorption spectroscopy. The capacity of nZVI to remediate the bulk phase of PCE is quantified by detecting the mass loss rate of PCE ganglia trapped in glass-etched pore networks during the continuous injection of nZVI suspension or pure water. The nZVI injection in porous media is simulated as an advection- dispersion process by accounting for the attachment/detachment of nanoparticles on the pore-walls, and describing the kinetics of PCE dissolution and reaction by 1st order equations. Visualization experiments reveal that the gradual elimination of PCE ganglia by the injected nZVI is associated with the preferential "erosion" of the upstream interfacial regions. The step controlling the overall process kinetics might be either (i) the enhanced PCE dissolution or (ii) the direct reaction of bulk PCE with the nZVI deposited upon the ganglia interfaces. Inverse modeling of the experiments under the simplifying assumption of one active mechanism indicates that the estimated kinetic coefficients are increasing functions of the flow rate.

Structural and Functional Hierarchy in Photosynthetic Energy Conversion-from Molecules to Nanostructures.

Basic principles of structural and functional requirements of photosynthetic energy conversion in hierarchically organized machineries are reviewed. Blueprints of photosynthesis, the energetic basis of virtually all life on Earth, can serve the basis for constructing artificial light energy-converting molecular devices. In photosynthetic organisms, the conversion of light energy into chemical energy takes places in highly organized fine-tunable systems with structural and functional hierarchy. The incident photons are absorbed by light-harvesting complexes, which funnel the excitation energy into reaction centre (RC) protein complexes containing redox-active chlorophyll molecules; the primary charge separations in the RCs are followed by vectorial transport of charges (electrons and protons) in the photosynthetic membrane. RCs possess properties that make their use in solar energy-converting and integrated optoelectronic systems feasible. Therefore, there is a large interest in many laboratories and in the industry toward their use in molecular devices. RCs have been bound to different carrier matrices, with their photophysical and photochemical activities largely retained in the nano-systems and with electronic connection to conducting surfaces. We show examples of RCs bound to carbon-based materials (functionalized and non-functionalized single- and multiwalled carbon nanotubes), transitional metal oxides (ITO) and conducting polymers and porous silicon and characterize their photochemical activities. Recently, we adapted several physical and chemical methods for binding RCs to different nanomaterials. It is generally found that the P(+)(QAQB)(-) charge pair, which is formed after single saturating light excitation is stabilized after the attachment of the RCs to the nanostructures, which is followed by slow reorganization of the protein structure. Measuring the electric conductivity in a direct contact mode or in electrochemical cell indicates that there is an electronic interaction between the protein and the inorganic carrier matrices. This can be a basis of sensing element of bio-hybrid device for biosensor and/or optoelectronic applications.

Photosynthetic machineries in nano-systems.

Photosynthetic reaction centres are membrane-spanning proteins, found in several classes of autotroph organisms, where a photoinduced charge separation and stabilization takes place with a quantum efficiency close to unity. The protein remains stable and fully functional also when extracted and purified in detergents thereby biotechnological applications are possible, for example, assembling it in nano-structures or in optoelectronic systems. Several types of bionanocomposite materials have been assembled by using reaction centres and different carrier matrices for different purposes in the field of light energy conversion (e.g., photovoltaics) or biosensing (e.g., for specific detection of pesticides). In this review we will summarize the current status of knowledge, the kinds of applications available and the difficulties to be overcome in the different applications. We will also show possible research directions for the close future in this specific field.

Photosynthetic reaction centers/ITO hybrid nanostructure.

Photosynthetic reaction center proteins purified from Rhodobacter sphaeroides purple bacterium were deposited on the surface of indium tin oxide (ITO), a transparent conductive oxide, and the photochemical/-physical properties of the composite were investigated. The kinetics of the light induced absorption change indicated that the RC was active in the composite and there was an interaction between the protein cofactors and the ITO. The electrochromic response of the bacteriopheophytine absorption at 771 nm showed an increased electric field perturbation around this chromophore on the surface of ITO compared to the one measured in solution. This absorption change is associated with the charge-compensating relaxation events inside the protein. Similar life time, but smaller magnitude of this absorption change was measured on the surface of borosilicate glass. The light induced change in the conductivity of the composite as a function of the concentration showed the typical sigmoid saturation characteristics unlike if the photochemically inactive chlorophyll was layered on the ITO. In this later case the light induced change in the conductivity was oppositely proportional to the chlorophyll concentration due to the thermal dissipation of the excitation energy. The sensitivity of the measurement is very high; few picomole RC can change the light induced resistance of the composite.

Porous silicon/photosynthetic reaction center hybrid nanostructure.

The purified photosynthetic reaction center protein (RC) from Rhodobacter sphaeroides R-26 purple bacteria was bound to porous silicon microcavities (PSiMc) either through silane-glutaraldehyde (GTA) chemistry or via a noncovalent peptide cross-linker. The characteristic resonance mode in the microcavity reflectivity spectrum red shifted by several nanometers upon RC binding, indicating the protein infiltration into the porous silicon (PSi) photonic structure. Flash photolysis experiments confirmed the photochemical activity of RC after its binding to the solid substrate. The kinetic components of the intraprotein charge recombination were considerably faster (τ(fast) = 14 (±9) ms, τ(slow) = 230 (±28) ms with the RC bound through the GTA cross-linker and only τ(fast) = 27 (±3) ms through peptide coating) than in solution (τ(fast) = 120 (±3) ms, τ(slow) = 1387 (±2) ms), indicating the effect of the PSi surface on the light-induced electron transfer in the protein. The PSi/RC complex was found to oxidize the externally added electron donor, mammalian cytochrome c, and the cytochrome oxidation was blocked by the competitive RC inhibitor, terbutryne. This fact indicates that the specific surface binding sites on the PSi-bound RC are still accessible to external cofactors and an electronic interaction with redox components in the aqueous environment is possible. This new type of biophotonic material is considered to be an excellent model for new generation applications at the interface of silicon-based electronics and biological redox systems designed by nature.

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.

Insight into cellular response of plant cells confined within silica-based matrices.

The encapsulation of living plant cells into materials could offer the possibility to develop new green biochemical technologies. With the view to designing new functional materials, the physiological activity and cellular response of entrapped cells within different silica-based matrices have been assessed. A fine-tuning of the surface chemistry of the matrix has been achieved by the in situ copolymerization of an aqueous silica precursor and a biocompatible trifunctional silane bearing covalently bound neutral sugars. This method allows a facile control of chemical and physical interactions between the entrapped plant cells and the scaffold. The results show that the cell-matrix interaction has to be carefully controlled in order to avoid the mineralization of the cell wall which typically reduces the bioavailability of nutrients. Under appropriate conditions, the introduction of a trifunctional silane (ca. 10%) during the preparation of hybrid gels has shown to prolong the biological activity as well as the cellular viability of plant cells. The relations of cell behavior with some other key factors such as the porosity and the contraction of the matrix are also discussed.