Information Security

Information Security: Biomolecular keypad lock systems, steganography and encrypting

Biocomputing Security System: Concatenated Enzyme-Based Logic Gates Operating as a Biomolecular Keypad Lock

The computing networks composed of the enzyme-based concatenated logic gates can be used for mimicking various electronic devices. The present paper reports on a novel approach to the assembling of the biomolecular keypad lock using the enzyme-based networking system. The biochemical paths include concert operation of multi-enzyme systems biocatalyzing chain reactions. Taking out one of the biocatalytic unit effectively inhibits the whole chain of the biochemical reactions. This property was used to assemble the enzyme-based biomolecular keypad lock. We designed a model biochemical reaction chain, which included hydrolysis of sucrose to glucose, oxidation of glucose by oxygen to yield hydrogen peroxide, and then oxidation of a synthetic dye, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), by H₂O₂ resulting in the formation of a colored product ABTS_ox. These reaction steps were biocatalyzed by invertase (Inv), glucose oxidase (GOx) and microperoxidase-11 (MP-11) respectively, and they proceeded only in the presence of these enzymes. The enzymes were immobilized on glass beads (1 mm diameter) and used in the immobilized form. The most important feature of the keypad lock system is the dependence of the output signal on the correct order of the input signals. Thus, we performed the experiment when the order of the enzyme-encoded input signals was varied in 6 different combinations. Only one correct order of the input signals (ABC) resulted in the TRUE output signal “1” while all others produced the FALSE output signal “0”. The TRUE output signal “1” can be used to “open” the lock while the FALSE signal “0” can result in the “alarm” signal indicating the wrong password.

Biocatalytic reactions in the biomolecular keypad lock system.

Representation of the biomolecular keypad lock system as a network of three concatenated AND gates.

The project is mostly performed by PhD student Guinevere Strack.

G. Strack, M. Ornatska, M. Pita, E. Katz, Biocomputing security system: Concatenated enzyme-based logic gates operating as a biomolecular keypad lock. J. Am. Chem. Soc. 2008, 130, 4234-4235 (paper was highligted by ACS and Chem. & Eng. News).

	Self-Powered Biomolecular Keypad Lock Security System Based on a Biofuel Cell The enzyme-based keypad lock was integrated with a biofuel cell yielding a self-powered biomolecular information security system. The correct “password” introduced into the keypad lock resulted in the activation of the biofuel cell, while all other “wrong” permutations of the enzyme inputs preserved the “OFF” state of the biofuel cell. J. Halámek, T.K. Tam, G. Strack, V. Bocharova, M. Pita, E. Katz, Self-powered biomolecular keypad lock security system based on a biofuel cell. Chem. Commun. 2010, 46, 2405-2407. (paper was highlighted at RSC web site: http://www.rsc.org/Publishing/ChemTech/Volume/2010/04/enzymes_power.asp).
	Left: (A) The biocatalytic cascade triggered by the enzyme inputs when they are applied in the “correct” A-B-C sequence. (B) The reaction/separation setup allowing application of the enzyme inputs in different permutations (shown in the correct order A-B-C). Top: Logic network corresponding to the biochemical scheme shown at the left.
	Left: The pH-switchable biofuel cell for “reading” the output signals generated by the keypad lock system. MB_ox and MB_red are the oxidized and reduced states of methylene blue mediator. Top: The polarization functions (A) and power output (B) of the biofuel cell obtained at different pH values: a) initial pH 6.7, b) pH 4.2 generated upon A-B-C sequence of the enzyme-inputs.

Keypad Lock Security System Based on Immune-Affinity Recognition Integrated with a Switchable Biofuel Cell

The immune-based biorecognition system mimicking a keypad lock device was integrated with a switchable biofuel cell resulting in the power output change upon the correct input of the “password” encoded in the antibody-sequence.

Left: (A) The multi-component immune-recognition system assembled upon application of the antibody-signals in the correct 1,2,3 sequence. (B) The biocatalytic reaction producing the optical output signal upon oxidation of TMB in the presence of HRP bound to the multi-component immune-complex. (C) The biocatalytic reaction producing the pH changes upon formation of ammonia in the presence of urease bound to the multi-component immune-complex.

J. Halámek, T.K. Tam, S. Chinnapareddy, V. Bocharova, E. Katz, Keypad lock security system based on immune-affinity recognition integrated with a switchable biofuel cell. J. Phys. Chem. Lett. 2010, 1, 973-977.

Left: The biofuel cell with the cathode switchable by pH changes. MB_ox and MB_red are the oxidized and reduced forms of methylene blue redox mediator.

Top: Polarization curves (A) and power output (B) generated by the biofuel cell: a) in the initial active state (pH 4.2 in the cathodic compartment), b) after addition of the solution (pH ca. 6.6) generated by the correct sequence (1,2,3) of the antibody-signals finished with the urease-labeled antibody. Inset: The power output measured on the load resistance of 180 kOhm upon application of different permutations of the antibody-signals and addition of the produced solution to the cathodic compartment.

The project was mostly performed by Dr. Jan Halámek (right) and PhD student Tsz Kin Tam (Ward) (left).

Steganography and Encrypting Based on Immunochemical Systems

Steganography and encrypting were demonstrated with immuno-specific systems. IgG-proteins were used as invisible ink developed with complementary antibodies labeled with enzymes producing color spots. The information security was achieved by mixing the target protein-antigens used for the text encoding with masking proteins of similar composition but having different bioaffinity. Two different texts were simultaneously encoded by using two different encoding proteins in a mixture. Various encrypting techniques were exemplified with the immuno-systems used for the steganography. Future use of the developed approach for information protection and watermark-technology was proposed. Scaling down the encoded text to a micro-size is feasible with the use of nanotechnology.

K.-W. Kim, V. Bocharova, J. Halámek, M.-K. Oh, E. Katz, Steganography and encrypting based on immunochemical systems. Biotechnology and Bioengineering 2011, in press (DOI: 10.1002/bit.23017).

(Scheme above): )Steganography based on the immuno-specific interactions resulting in the color-development by the enzyme-labeled complementary antibody similarly to ELISA technique. A: There is no binding of the enzyme-labeled antibodies to a mixture of masking proteins. B) The enzyme-labeled antibody (HRP-labeled anti-mouse IgG) binds to the corresponding target protein-antigen (mouse anti-human IgG) in the presence of a mixture of masking proteins, thus resulting in the biocatalytic oxidation of TMB. C: Two enzyme-labeled antibodies (HRP-labeled anti-mouse IgG and AP-labeled anti-rabbit IgG) bind to the corresponding target protein-antigens (mouse anti-human IgG and rabbit anti-rat IgG) in the presence of a mixture of masking proteins, thus resulting in the biocatalytic oxidation of TMB and formation of PNP. Inset: Images show protein-modified wells corresponding to the biorecognition systems shown schematically above.

(Figure at right): Absorbance developed on spots composed of: A: mouse anti-human IgG (target protein), goat anti-cat IgG (masking protein) and donkey anti-chicken IgG (masking protein); B: only masking proteins without the target protein-antigen, after their treatment with HRP-labeled anti-mouse IgG (antibody complementary to the target protein-antigen) and further reaction with H₂O₂ and TMB. The experiment was performed on an ELISA plate.

The experiments with the steganography and encrypting systems were performed by PhD-internship student Kyung-Woo Kim.

Updated on February 21, 2011