The Laser Physics Letters (2011 impact factor, 9.97) has published a joint study by researchers of LNBE and the Laboratory for Research in Nanosciences of the University of Reims on nano–bio hybrid materials with controlled resonance energy transfer

The paper entitled Nano-Biophotonic Hybrid Materials with Controlled FRET Efficiency Engineered from Quantum Dots and Bacteriorhodopsin was written by Dr. Sukhanova, the head of the Nanomedicine Group and Prof. Nabiev, Leading Scientist of LNBE in collaboration with their French colleagues (Nicolas Bouchonville, Anthony Le Cigne, Alyona Sukhanova, Michael Molinari and Igor Nabiev. Laser Physics Letters, 2013, 10, 085901). The study deals with a promising line of nanobiotechnological research and developments, namely, the use of photosensitive biomolecules as components of various devices, such as photoreceivers, transceivers, optical switches, molecular engines, and electronic switches.

The protein bacteriorhodopsin (bR) is one of biomolecules most often used in designing such devices, mainly due to its high thermo-, chemo-, and photostability. In nature, large amounts of bR are contained in membranes of the archaeon (a microorganism more primitive than a bacterium) Halobacterium salinarum, where bR uses solar energy to generate a membrane potential. This very capacity for generating an electrical potential is employed in bioinspired devices.

However, solar energy is not used very efficiently under natural conditions: the entire ultraviolet spectral region is "lost" because the high-energy UV photons would have destroyed proteins and other membrane components if not for special protective mechanisms preventing UV light absorption.

In order to utilize light energy more efficiently, a hybrid material has been fabricated that contains bR in its natural microenvironment (H. salinarum membranes) and semiconductor nanocrystals or so-called quantum dots. First, these nanocrystals absorb light in a wide spectral range and then emit it through luminescence in a much narrower range (and at longer wavelengths, too, as is customary for luminescence), with the emission wavelength directly determined by the crystal size. Second, the nanosrystals can transfer energy over short distances without luminescing (this effect is called Förster resonance energy transfer or FRET). This energy can be transferred to bR, thereby tremendously increasing the efficiency of light energy utilization.

The authors have found how the intensity of the energy transfer from nanocrystals to bR can be precisely "tuned" by varying, first, the emission spectrum of the nanocrystals and, second, the distance between the donors and acceptors of energy (the nanocrystals and bR molecules) in the hybrid material. This is the applied "output" of the study.

There is also an important theoretical aspect. The point is, the efficiency of energy transfer has proved to be much higher than the existing theory of FRET predicts. Additional fundamental research is required to find out why this is so; this, however, by no means prevents immediate use of the phenomenon itself in practical biophotonics.

© 2012 Laboratory of Nano-BioEngineering