Implantable biofuel cells have been suggested as sustainable micropower sources operating in living organisms, but such bioelectronic systems are still exotic and very challenging to design. Very few examples of abiotic and enzyme-based biofuel cells operating in animals in vivo have been reported. Implantation of biocatalytic electrodes and extraction of electrical power from small living creatures is even more difficult and has not been achieved to date. Here we report on the first implanted biofuel cell continuously operating in a snail and producing electrical power over a long period of time using physiologically produced glucose as a fuel. The "electrified" snail, being a biotechnological living "device", was able to regenerate glucose consumed by biocatalytic electrodes, upon appropriate feeding and relaxing, and then produce a new "portion" of electrical energy. The snail with the implanted biofuel cell will be able to operate in a natural environment, producing sustainable electrical micropower for activating various bioelectronic devices.

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We develop an approach aimed at optimizing the parameters of a network of biochemical logic gates for reduction of the "analog" noise buildup. Experiments for three coupled enzymatic AND gates are reported, illustrating our procedure. Specifically, starch, one of the controlled network inputs, is converted to maltose by beta-amylase. With the use of phosphate (another controlled input), maltose phosphorylase then produces glucose. Finally, nicotinamide adenine dinucleotide (NAD(+)), the third controlled input, is reduced under the action of glucose dehydrogenase to yield the optically detected signal. Network functioning is analyzed by varying selective inputs and fitting standardized few-parameters "response-surface" functions assumed for each gate. This allows a certain probe of the individual gate quality, but primarily yields information on the relative contribution of the gates to noise amplification. The derived information is then used to modify our experimental system to put it in a regime of a less noisy operation.

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Novel biocompatible hybrid-material composed of iron-ion-cross-linked alginate with embedded protein molecules has been designed for the signal-triggered drug release. Electrochemically controlled oxidation of Fe(2+) ions in the presence of soluble natural alginate polymer and drug-mimicking protein (bovine serum albumin, BSA) results in the formation of an alginate-based thin-film cross-linked by Fe(3+) ions at the electrode interface with the entrapped protein. The electrochemically generated composite thin-film was characterized by electrochemistry and atomic force microscopy (AFM). Preliminary experiments demonstrated that the electrochemically controlled deposition of the protein-containing thin-film can be performed at microscale using scanning electrochemical microscopy (SECM) as the deposition tool producing polymer-patterned spots potentially containing various entrapped drugs. Application of reductive potentials on the modified electrode produced Fe(2+) cations which do not keep complexation with alginate, thus resulting in the electrochemically triggered thin-film dissolution and the protein release. Different experimental parameters, such as the film-deposition time, concentrations of compounds and applied potentials, were varied in order to demonstrate that the electrodepositon and electrodissolution of the alginate composite film can be tuned to the optimum performance. A statistical modeling technique was applied to find optimal conditions for the formation of the composite thin-film for the maximal encapsulation and release of the drug-mimicking protein at the lowest possible potential.