Special Report: Bio-inspired biotechnology
Professor Donald Martin of the Université Grenoble Alpes discusses how Nature provides the inspiration behind medical biotechnology.
The multidisciplinary research team SyNaBi, working within the TIMC-IMAG laboratory at the Université 
Grenoble Alpes, France, has taken a bio-inspired approach to develop innovative biotechnologies that provide alternative energy supplies for implanted medical devices. The SyNaBi team has pioneered the successful implantation of bioelectrodes and biofuel cells that function for long periods inside a mammal.
A bio-inspired approach
An active, implanted medical device requires an electrical power source to provide a stimulatory, pumping, transmitting or amplification assistance to an organ with reduced function. Such implanted medical devices include, for example, pacemakers, cochlear implants, implanted bladder stimulators, insulin pumps, implantable wireless pressure sensors and neurostimulators. The power for such active systems is provided by lithium-based storage batteries. Although a lithium battery is currently the first choice in supplying power to electronic medical implants, one disadvantage is the limited capability to miniaturise this storage battery and still be able to provide large power levels. There is also the problem of removal and disposal for the lithium storage batteries that are implanted directly inside the heart along with the lead-less pacemaker.
The bio-inspired approach of SyNaBi has created an alternative power supply, which is a prototype biofuel cell that produces power of around 1μW/μL from molecules continuously available in the internal body fluids. For example, the power required for a pacemaker is provided by a biofuel cell of 40μL in volume, which is less than 1% of the volume of the standard lithium battery used for a pacemaker. The biofuel cell does not need to be inside blood vessels to produce that power. The breakthrough of the SyNaBi team was the development of the biotechnology to create simple yet highly efficient bio-electrodes for the biofuel cell (Fig. 1).
The bio-electrodes for this biofuel cell have functioned continuously for more than six months inside a rabbit, for more than a month inside a sheep, and have also functioned in cows and pigs. One major advantage is the capability for miniaturisation with the advantage of providing more than ten times the power-to-volume output of a lithium storage battery. This advantage is due to the biofuel cell utilising molecules supplied continuously from the internal body fluids in order to convert chemical reactions into electrical power, and without the need to store all of these needed fuel molecules (as does a lithium storage battery). The form of those bioelectrodes is not fixed, but is adaptable to a multitude of shapes and sizes to meet the needs for implantation and the required power output. The ongoing development of the SyNaBi team is now improving the bioelectrodes to produce much higher power-to-volume output, which augurs well for even greater levels of miniaturisation.
Advanced bio-inspired biotechnology
Nature is full of complex, elegant things. Inspiration from such elegant natural processes provides a path to develop new biotechnology systems that produce power, and to create new medical, diagnostic and therapeutic devices. The path is complex, but successful biomimicry of biological processes usually results in highly sensitive biotechnology devices, including for example, protein-based biosensors to better mimic the biological needs to detect bio-active molecules. From its understanding of protein-lipid interactions, the SyNaBi team has pioneered the production of power using biological membrane transport proteins incorporated in a biomimetic lipid bilayer membrane. An important universal component at the core of this type of bio-inspired biotechnology is the biomimetic lipid bilayer membrane, which is self-assembled using principles derived from natural biology.
The SyNaBi team is now able to reproduce self-assembled biological transport systems as prototypes for highly miniaturised and very powerful biofuel cells, as well as for cancer diagnostic devices. The current prototype for this biomimetic biofuel cell provides about 4W/kg of power from such a bio-inspired, self-assembled system.
The SyNaBi approaches have utilised the knowhow of biophysics, biochemistry and molecular biology in unravelling the secrets of biological self-assembly for proteins in lipid bilayer membranes. An example from that research is shown in Fig. 2. The challenge for any biomimetic membrane technology based on lipid membranes is to ensure the stability and durability of the lipid membranes. Although challenging to engineer, good stability and durability is usually achieved using lipid bilayers that are tethered to or supported by a substrate that may be non-porous (e.g. gold, silicon) or porous (e.g. polymer, gel), rather than using suspended lipid bilayers.
Bio-inspired biotechnology for cancer diagnostics
The SyNaBi team has used its skills in biomimetic nanobiotechnology to develop a biomimetic membrane that enables the UroLOC
3-dimensional lab-on-chip environment.1 This 3D environment mimics the normal organised structure in glands of mixed populations of epithelial cells supported by stromal cells. The biomimetic membrane enables the 3D cell culture lab-on-chip environment of UroLOC to collect, in real time, the nanolitre volumes of secretions directly from living cells growing in this native tissue-like environment.
UroLOC is designed to detect changes in the secretions (e.g. proteins, genes, RNAs and low-molecular-weight peptides) from epithelial cells that are potentially tumorigenic. The UroLOC device is designed to provide a functional ‘liquid biopsy’ from those living cells. The diagnostic advantage is that the secretions are already in a concentrated form, which improves the sensitivity. The UroLOC device does not require a priori knowledge of a particular biomarker to achieve this sensitive diagnostic result.2
Concluding remarks
The results from the SyNaBi team show that a bio-inspired approach to develop innovative biotechnologies has several advantages. These include an improved biocompatibility for implanted devices, an improved sensitivity for the detection of biological molecules, an improved power-to-volume efficiency for energy production, and the elegance of a bio-inspired approach for miniaturisation.
Further reading
1 Martin DK, Picollet-d’hahan N (2016). ‘Puce de co-culture cellulaire et son procède de fabrication’, 1654213 FR
2 Martin DK, Picollet-d’hahan N (2016). ‘Méthode de diagnostic de cancers urologiques’, 1654215 FR
3 Soranzo T, Martin DK, Lenormand JL, Watkins EB (2017). Coupling neutron reflectivity with cell-free protein synthesis to probe membrane protein structure in supported bilayers. Scientific Reports, 7: 3399, DOI:10.1038/s41598-017-03472-8
4 Maccarini M, Watkins EB, Stidder B, Alcaraz JP, Cornell BA, Martin DK (2016). Nanostructural determination of a lipid bilayer tethered to a gold substrate. European Physical Journal E, 39:123
5 El Ichi-Ribault S, Zebda A, Laaroussi A, Reverdy-Bruas N, Chaussy D, Belgacem MN, Cinquin P, Martin DK (2016). Laccase-based biocathodes: comparison of chitosan and nafion. Analytica Chimica Acta, 937:43-52
6 Picollet-d’hahan N, Dolega ME, Liguori L, Marquette C, Le Gac S, Gidrol X, Martin DK (2016). A 3D toolbox to enhance the physiological relevance of human tissue models. Trends in Biotechnology, 34:757-769
7 Alcaraz JP, El Ichi-Ribault S, Cortella L, Guimier-Pingault C, Zebda A, Cinquin P, Martin DK (2016). La biopile enzymatique à glucose/oxygène : Quelques nuances de Grays. Médecine/Sciences, 32:771-773
8 Liguori L, Stidder B, Alcaraz JP, Lenormand JL, Cinquin P, Martin DK (2016). Cell-free production of VDAC directly into liposomes for integration with biomimetic membrane systems. Preparative Biochemistry and Biotechnology, 46:546-551
9 El Ichi S, Zebda A, Alcaraz JP, Laaroussi, A, Boucher F, Boutonnat J, Reverdy-Bruas N, Chaussy D, Belgacem MN, Cinquin P, Martin DK (2015). Bioelectrodes modified with chitosan for long-term energy supply from the body. Energy Environmental Science. 8:1017-1026
10 El Ichi S, Zebda A, Laaroussi A, Reverdy-Bruas N, Chaussy D, Belgacem MN, Cinquin P, Martin DK (2014). Chitosan improves stability of carbon nanotube biocathods for glucose biofuel cells. Chemical Communications, 50:14535-1438
11 Zebda A, Cosnier S, Alcaraz JP, Holzinger M, Le Goff A, Gondran C, Boucher F, Giroud F, Gorgy K, Lamraoui H, Cinquin P (2013). Single glucose biofuel cells implanted in rats power electronic devices. Scientific Reports, 3:1516, DOI:10.1038/srep01516
12 Stidder B, Alcaraz JP, Liguori L, Khalef N, Bakri A, Watkins E, Cinquin P, Martin DK (2012). Biomimetic membrane system composed of a composite interpenetrating hydrogel film and lipid bilayer. Advanced Functional Materials, 20:4259-4267
13 Zebda A, Gondran C, Le Goff A, Holzinger M, Cinquin P, Cosnier S (2011). Mediatorless high-power glucose biofuel cells based on compressed carbon nanotube-enzyme electrodes. Nature Communications, 2:370, DOI:10.1038/ncomms1365
14 Cinquin P, Gondran C, Giroud F, Mazabrard S, Pellissier A, Boucher F, Alcaraz JP, Gorgy K, Lenouvel F, Mathé S, Porcu P, Cosnier S (2010). A glucose biofuel cell implanted in rats. PLoS One, 5(5);e10476, DOI:10.1371/journal.pone.0010476
15 Battle AR, Valenzuela SM, Mechler A, Nichols RJ, Praporski S, di Maio IL, Islam H, Girard-Egrot AP, Cornell BA, Prashar J, Caruso F, Martin LL, Martin DK. (2009). Novel engineered ion channel provides controllable ion permeability for polyelectrolyte microcapsules coated with a lipid membrane. Advanced Functional Materials, 19:201-208
