Abstract:
A molecular communication system includes a molecular transmitter ( 20 ) configured to transmit an information molecules ( 15 ) onto which prescribed information is encoded; a molecular receiver ( 30 ) configured to receive the information molecule, a molecule propagation channel ( 40 ) extending from the molecular transmitter to the molecular receiver, and a molecular capsule ( 10 ) configured to encapsulate the information molecules to be transmitted from the molecular transmitter to the molecular receiver, wherein the surfaces of the molecular transmitter, the molecular receiver, and the molecular capsule have lipid bilayer membrane structure, and wherein the system further includes encapsulation means for applying a first chemical substance to the molecular transmitter, or to the molecular transmitter and the molecular capsule to encapsulate the information molecules into the molecular capsule, and decapsulation means for applying a second chemical substance to the molecular capsule and the molecular receiver to take the information molecules out of the molecular capsule and take them into the molecular receiver.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to molecular communication, and more particularly, to a molecular communication system and method in which information encoded molecules are encapsulated in a molecular capsule and transmitted from a molecular transmitter to a molecular receiver. 
     2. Description of the Related Art 
     In recent years and continuing, studies and research have been made of molecular communication systems using nano-scale chemical substances (molecules) as information carriers. In a molecular communication system, information is encoded onto molecules and communication is done based on biochemical reactions caused upon reception of the information encoded molecules. See, for example, S. Hiyama, et al., “Molecular Communication,” Proceedings on NSTI Nanotechnology Conference and Trade Show 2005, vol. 3, pp. 391-394, May, 2005, as well as S. Hiyama, et al., IEICE journal, Vol. 89, No. 2, pp. 162-166, February, 2006. 
     Unlike existing communication technologies that use electromagnetic waves (electric signals or optical signals) as information carriers, molecular communication uses biochemical signals which cause slow speed communication and small energy consumption. Molecular communication has high potentiality for applications of a communication between nano-scale devices that cannot use electromagnetic waves by capability reasons or environmental reasons and an operational control of nanomachines that are not composed by electronic components and cannot be driven by electronic signals. 
     In molecular communication, a molecular transmitter generates molecules for encoding information (referred to simply as “information molecules”), encodes information onto the information molecules, and emits the information molecules to the environment. The emitted information molecules are carried to a molecular receiver through a molecule propagation channel. The molecular receiver uptakes the propagated information molecules, decodes the information, and expresses biochemical reaction. 
     Information molecules in molecular communication are likely to be denaturalized due to the interaction with resolving enzyme (or degradative enzyme) existing in the propagation environment or due to environmental factors such as temperature, pH, or light, and the encoded information may be lost during the propagation. To avoid this inconvenience, it is proposed to encapsulate the information molecules in a molecular capsule called vesicle which has the lipid bilayer membrane structure. See, for example, Y. Moritani, et al., “Molecular Communication for Health Care Applications,” Proceedings on Fourth IEEE International Conference on Pervasive Computing and Communications WORKSHOPS, pp. 549-553, March 2006. 
     This publication, however, proposes only an idea of encapsulating information molecules in a molecular capsule for propagation, and there is no method disclosed concretely for encapsulating the information molecules. Accordingly, it is desired to present how information molecules are actually encapsulated in a molecular capsule prior to transmission, and how the encapsulated information molecules are actually taken out of the molecular capsule and introduced into the molecular receiver. 
     SUMMARY OF INVENTION 
     Therefore, the embodiments of the present invention aim to provide a technique for encapsulating information molecules in a molecular capsule so as to be suitable for propagation between a molecular transmitter and a molecular receiver, and a technique for taking the information molecules out of the molecular capsule and introducing them into the molecular receiver. 
     To achieve this, in the embodiments, a first chemical substance is applied to a molecular transmitter, or to the molecular transmitter and a molecular capsule, to encapsulate one or more information molecules in the molecular capsule. A second chemical substance is applied to the molecular capsules and a molecular receiver to take the information molecules out of the molecular capsule and take them into the molecular receiver. 
     To be more precise, in one aspect of the invention, a molecular communication system includes: 
     a molecular transmitter configured to transmit an information molecule onto which prescribed information is encoded; 
     a molecular receiver configured to receive the information molecule; 
     a molecule propagation channel extending between the molecular transmitter and the molecular receiver; and 
     a molecular capsule configured to encapsulate the information molecules to be transmitted from the molecular transmitter to the molecular receiver, 
     wherein the surfaces of the molecular transmitter, the molecular receiver, and the molecular capsule have the lipid bilayer membrane structure, and 
     wherein the system further includes: 
     encapsulation means for applying a first chemical substance to the molecular transmitter, or to the molecular transmitter and the molecular capsule to encapsulate the information molecules into the molecular capsule, and 
     decapsulation means for applying a second chemical substance to the molecular capsule and the molecular receiver to take the information molecules out of the molecular capsule and take them into the molecular receiver. 
     With this molecular communication system, one or more information molecules are encapsulated in a molecular capsule on the transmission side, and the information molecules are taken out of the molecular capsule and introduced into the molecular receiver on the receiving side. 
     For example, a molecular capsule is placed near the molecular transmitter in advance and the first chemical substance is applied to the molecular transmitter and the molecular capsule by the encapsulation means to temporarily form pores in the surfaces of the molecular transmitter and the molecular capsule so as to allow the information molecules to escape from the molecular transmitter and get into the molecular capsule. 
     The first chemical substance may be a solution containing antimicrobial peptide. 
     In an alternative, the encapsulation means applies the first chemical substance to the molecular transmitter that has the information molecules inside to cause a part of the molecular transmitter to split as the molecular capsule containing a part of the information molecules inside. 
     In this case, the first chemical substance may be a solution containing lysophosphatidylcholine. 
     In still another alternative, the encapsulation means applies the first chemical substance to the molecular transmitter having the information molecules to produce the molecular capsule that encapsulates the information molecules inside of the molecular transmitter, and to allow the produced molecular capsule to be emitted to the molecular propagation channel. 
     In this case, the first chemical substance may be a phospholipid micellar solution. 
     The decapsulation means places the transmitted molecular capsule near the molecular receiver and applies the second chemical substances to the molecular capsule and the molecular receiver to temporarily form pores in the surfaces of the molecular receiver and the molecular capsule so as to allow the information molecules to escape from the molecular capsule and get into the molecular receiver. 
     In this case, the second chemical substance may be a solution containing antimicrobial peptide. 
     Alternatively, the decapsulation means applies the second chemical substance to the molecular receiver and the molecule capsule placed near the molecular receiver to fuse the molecular capsule to the molecular receiver. 
     In this case, the second chemical substance may be a solution containing lanthanum ion. 
     This system is advantageous because undesirable information loss can be avoided. Such information loss is caused by denaturalization of the information molecules due to the interaction between the transmitted information molecules and other molecules existing in the propagation environment, or by denaturalization of the information molecules due to environmental factors such as temperature or pH. In addition, because the information molecules are encapsulated, the biochemical or physical characteristics of the information molecules can be hidden from the propagation channel, and accordingly, a uniform interface can be provided. Information can be encoded not only onto a single information molecule, but also onto the concentration or the composition of a set of information molecules in the molecular capsule. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features and advantages of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: 
         FIG. 1A  and  FIG. 1B  are schematic diagrams for illustrating a molecular communication system according to an embodiment of the invention; 
         FIG. 2A  and  FIG. 2B  are schematic diagrams illustrating examples of the molecule propagation channel used in the molecular communication system shown in  FIG. 1A ; 
         FIG. 3  illustrates operational example 1 for encapsulating information molecules into a molecular capsule in the molecular communication system of  FIG. 1A ; 
         FIG. 4  illustrates operational example 2 for encapsulating information molecules into a molecular capsule in the molecular communication system of  FIG. 1A ; 
         FIG. 5  illustrates operational example 3 for encapsulating information molecules into a molecular capsule in the molecular communication system of  FIG. 1A ; 
         FIG. 6  illustrates operational example 1 for taking the information molecules out of the molecular capsule and getting them into the molecular receiver in the molecular communication system of  FIG. 1A ; 
         FIG. 7  illustrates operational example 2 for taking the information molecules out of the molecular capsule and getting them into the molecular receiver in the molecular communication system of  FIG. 1A ; 
         FIG. 8A  and  FIG. 8B  illustrate a modification of the transmission side of the molecular communication system shown in  FIG. 1A ; and 
         FIG. 9A  and  FIG. 9B  illustrate a modification of the receiving side of the molecular communication system shown in  FIG. 1A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention are now described in conjunction with the attached drawings.  FIG. 1A  and  FIG. 1B  are schematic diagrams illustrating a molecular communication system according to an embodiment of the invention. The molecular communication system  1  includes a molecular transmitter  20 , a molecular receiver  30 , a molecular capsule  10  encapsulating an information molecule  15 , and a molecule propagation channel  40  through which the molecular capsule  10  is transmitted from the molecular transmitter  20  to the molecular receiver  30 . The information molecule  15  serves as an information carrier. 
     In the molecular communication system  1 , the information molecule  15  transmitted from the molecular transmitter  20  is encapsulated into the molecular capsule  10  (indicated by the dashed arrow ( 1 )). The information molecule  15  encapsulated in the molecular capsule  10  can be produced by applying a chemical substance to the molecular transmitter  20 , or to the molecular transmitter  20  and the molecular capsule  10 , the detailed operations of which will be described below. 
     The molecular capsule  10  encapsulating the information molecule  15  is propagated to the molecular receiver  30  through the molecular propagation channel  40  (indicated by the dashed arrow ( 2 )). 
     At the molecular receiver  30 , the information molecule  15  is taken out of the molecular capsule  10  and introduced into the molecular receiver  30  (indicated by the dashed arrow ( 3 )) by applying a chemical substance to the molecular capsule  10  and the molecular receiver  30 . 
     As illustrated in  FIG. 1B , the surfaces of the molecular transmitter  20 , the molecular receiver  30 , and the molecular capsule  10  have the lipid bilayer membrane structure  51 . The lipid bilayer membrane structure  51  is composed of lipid molecules assembled each other, each lipid molecule having a hydrophilic head  52   a  and a hydrophobic tail  52   b . Accordingly, the lipid bilayer membrane structure  51  has a hydrophilic part  51   a  and a hydrophobic part  51   b . This bilayer membrane structure guarantees the encapsulation, and can prevent leakage of the information molecule  15  from the molecular capsule  10 . The environment in which the molecular transmitter  20 , the molecular receiver  30 , and the molecular capsule  10  exist is in an aqueous solution. 
     The molecular transmitter  20 , the molecular receiver  30 , and the molecular capsule  10  are, for example, liposomes composed of phosphatide (such as phosphatidylcholine). The liposome is produced by dispersing phosphatide, which becomes the major component of the membrane, in water, followed by agitation or ultrasonic treatment. The molecules used to compose the lipid bilayer membrane structure of the molecular transmitter  20 , the molecular receiver  30  and the molecular capsule  10  are not limited to phosphatides, and any suitable molecules including glycolipids may be used as long as a lipid bilayer membrane structure that can prevent leakage of the information molecule  15  is acquired. 
     The information molecular  15  is, for example, a DNA. In ordinary conditions, DNAs do not escape from the molecular transmitter  20 , the molecular receiver  30 , or the molecular capsule  10 . The information is encoded onto a specific base sequence or a specific structure (such as hairpin structure or bulge structure) of the information molecule  15 . Alternatively, the information molecule  15  may be an ion or peptide. In this case, the information code is not limited to base sequences or structures. When using ions, information can be encoded based upon types of the information molecules. When using peptides, the information can be encoded in amino acid sequences. 
     As illustrated in  FIG. 2A  and  FIG. 2B , the molecule propagation channel  40  is constructed by motor molecules  46  and rail molecules  47  arranged so as to transport the molecular capsule  10  having the information molecule  15  inside from the molecular transmitter  20  to the molecular receiver  30 . For example, kinesins can be used as the motor molecule  46 , and microtubules can be used as the rail molecule  47 . The moving direction of the kinesine (motor molecule)  46  is determined by the polarity of the microtubule  47 . 
     In the example shown in  FIG. 2A , rail molecules  47  are fixed to the substrate  41 , while in  FIG. 2B  motor molecules  46  are fixed on the substrate  41 , in a solution containing adenosine triphosphate (ATP). The moving speed of the molecular capsule  10  carried by the free (non-fixed) molecules is controllable by adjusting the ATP concentration, magnesium ion concentration, temperature, and/or the viscosity resistance of the solution. 
     The molecule propagation channel  40  is not limited to the above-described example constructed by motor molecules and rail molecules, and any suitable channel can be used as long as the molecular capsule  10  for encapsulating the information molecule  15  can be transmitted from the molecular transmitter  20  to the molecular receiver  30 . For example, the molecule propagation channel  40  may be a liquid flow channel. 
     Next, operations of the molecular communication system  1  are explained for transmitting the information molecule  15  from the molecular transmitter  20  to the molecular receiver  30 . 
       FIG. 3  through  FIG. 5  illustrate examples of encapsulation of the information molecules  15  from the molecular transmitter  20  into the molecular capsule  15 . In either example, the inside of the molecular transmitter  20  is filled with a solution  21 , and information molecules are dispersed homogeneously through diffusion. By applying a chemical substance to the molecular transmitter  20 , or to the molecular transmitter  20  and the molecular capsule  10 , the information molecule  15  encapsulated into the molecular capsule  10  can be produced at or near the molecular transmitter  20 . 
     In the example shown in  FIG. 3 , a solution  60 A containing lysophosphatidylcholine is applied to the molecular transmitter  20  to cause a portion of the molecular transmitter  20  to split from the molecular transmitter  20 . Through this process, a molecular capsule  10  having one or more information molecules  15  inside is produced and separated from the molecular transmitter  20 . In this case, the divided part of the molecular transmitter  20  becomes the molecular capsule  10  containing information molecules  15 , and therefore, the concentration of the information molecules  15  encapsulated in the molecular capsule  10  are same of that in the molecular transmitter  20 . Although only a single information molecule  15  is depicted in the molecular capsule  10  for simplification purpose, two or more information molecules  15  can be encapsulated in the molecular capsule  10 . Details of the membrane fission caused by the solution containing lysophosphatidylcholine is described in T. Tanaka, et al., “Shape Change and Vesicle Fission of Giant Unilamellar Vesicles of Lipid-Ordered Phase Membrane Induced by Lysophosphatidylcholine,” Langmuir, vol. 20, pp 9526-9534, 2004. 
     The solution  60 A containing lysophosphatidylcholine may be applied to the molecular transmitter  20  using a micropipette at constant intervals or in response to instructions. 
     In  FIG. 4 , a solution  60 B containing phospholipid micelle may be applied to the molecular transmitter  20 . In this case, a molecular capsule  10  encapsulating information molecules  15  is produced inside of the molecular transmitter  20 . The produced molecular capsule  10  is autonomously emitted outside of the molecular transmitter  20 . The information molecules  15  are encapsulated into the molecular capsule  10  when the molecular capsule  10  is produced in molecular transmitter  20  at the same concentration as in the molecular transmitter  20 . Details of the production of vesicles are described in K. Takakura, et al., “A Novel System of Self-reproducing Giant Vesicles,” Journal of the American Chemical Society, vol. 125, pp. 8134-8140, 2003. 
     In  FIG. 5 , a molecular capsule  10  is placed near the molecular transmitter  20  in advance, and a solution  60 C containing antimicrobial peptide is applied to the molecular transmitter  20  and the molecular capsule  10 . In this case, pores  20   a  and  10   a  are formed in the surface of the molecular transmitter  20  and the molecular capsule  10 , respectively, and the information molecules  15  leaked out of the molecular transmitter  20  are encapsulated into the molecular capsule  10 . 
     The applied antimicrobial peptide solution  60 C spreads in the environment and the concentration of the antimicrobial peptide decreases as time passes. Consequently, the pores  20   a  and  10   a  formed in the surface of the molecular transmitter  20  and the molecular capsule  10  are naturally closed after a certain time. Leakage of the information molecules  15  from the molecular transmitter  20  occurs naturally according to the concentration gradient; however, encapsulation of the information molecules  15  in the molecular capsule  10  occurs stochastically through diffusion. Accordingly, the concentration of the information molecules  15  encapsulated in the molecular capsule  10  may vary depending on the distance between the molecular transmitter  20  and the molecular capsule  10  or the concentration of the antimicrobial peptide solution  60 C. Details of the formation of pores in a membrane are described in Y. Tamba, et al., “Single Giant Unilamellar Vesicle Method Reveals Effect of Antimicrobial Peptide Magainin 2 on Membrane Permeability,” Biochemistry, vol. 44, pp. 15823-15833, 2005. 
     In this manner, by applying a chemical substance to the molecular transmitter  20 , or to the molecular transmitter  20  and the molecular capsule  10 , information molecules  15  encapsulated into the molecular capsule  10 . The sequences of separation of information molecules from the molecular transmitter  20  and encapsulation of the information molecules are not limited in this order, and either one may be performed first as long as the information molecules transmitted from the molecular transmitter  20  are encapsulated into the molecular capsule  10 . 
     Then, the molecular capsule  10  encapsulating the information molecules  15  propagates through the molecule propagation channel  40  to the molecular receiver  30 . 
     At the molecular receiver  30 , the information molecules  15  can be taken out of the molecular capsule  10  and introduced into the molecular receiver  30  by applying a chemical substance to the molecular receiver  30  and the molecular capsule  10 .  FIG. 6  and  FIG. 7  illustrate examples of the reception process of the information molecule  15 . 
     In  FIG. 6 , a solution  60 D containing lanthanum ion is applied to the molecular capsule  10  and the molecular receiver  30  to cause the molecular capsule  10  to fuse to the molecular receiver  30 . Through the fusion, the information molecule  15  is taken out of the molecular capsule  10  and introduced into the molecular receiver  30 . Because the molecular capsule  10  becomes a part of the molecular receiver  30 , all the information molecules encapsulated in the molecular capsule  10  are taken into the molecular receiver  30 . Details of membrane fusion are described in T. Tanaka, et al., “Membrane Fusion of Giant Unilamellar Vesicles of Neutral Phospholipid Membrane Induced by La 3+ ,” Langmuir, vol. 20, pp. 5160-5164, 2004. 
     In  FIG. 7 , a solution  60 C containing antimicrobial peptide is applied to the molecular capsule  10  and the molecular receiver  30 . By the application of solution  60 C, pores  10   a  and  30   a  are formed in the molecular capsule  10  and the molecular receiver  30 , respectively. The information molecules  15  escape from the molecular capsule  10  through the pore  10   a , and are introduced into the molecular receiver  30  through the pore  30   a . As in the encapsulation shown in  FIG. 5 , the solution  60 C containing antimicrobial peptide spreads in the environment and the concentration of the antimicrobial peptide decreases as time passes; consequently, the pores  10   a  and  30   a  formed in the molecular capsule  10  and the molecular receiver  30  close naturally as time passes. The leakage of the information molecules  15  from the molecular capsule  10  through the pore  10   a  occurs naturally according to the concentration gradient, and the introduction of the information molecules  15  into the molecular receiver  30  through the pore  30   a  occurs stochastically through diffusion. This means that the concentration of the information molecules  15  taken into the molecular receiver  30  may vary depending on the distance between the molecular capsule  10  and the molecular receiver  30 , or the concentration of the solution  60 C containing antimicrobial peptide. 
     In this manner, under the application of a chemical substance to the molecular capsule  10  and the molecular receiver  30 , the information molecules  15  can be taken out of the molecular capsule  10  and introduced into the molecular receiver  30 . 
     By performing the encapsulation and decapsulation at the molecular transmitter and the molecular receiver, respectively, a molecular communication system for transmitting the information molecules  15  from the molecular transmitter  20  to the molecular receiver  30  using a molecular capsule  10  can be realized. 
     Next, a modification of the embodiment is described in conjunction with  FIGS. 8A ,  8 B,  9 A and  9 B. When transporting information molecules  15  encapsulated in the molecular capsule  10  through the molecule propagation channel  40  constructed by motor molecules  46  and rail molecules  47 , the specific binding phenomenon between single-stranded nucleotides may be used to bind the molecular capsule  10  to the gliding microtubule (rail molecule)  47 . 
     A method for loading a non-encapsulated information molecules on a microtubule using a specific double-stranding reaction (hybridization) between single-stranded nucleotides and for unloading the non-encapsulated information molecule from the microtubule at a prescribed location using specific dehybridization and hybridization between single-stranded nucleotides is described in S. Hiyama, et al., “A Design of an Autonomous Molecule Loading/Transporting/Unloading System Using DNA Hybridization and Biomolecular Linear Motors,” Proceedings on European Nano Systems 2005, pp. 75-80, December 2005. 
     As illustrated in  FIG. 8A , a microtubule  47  is moving on kinesins  46  fixed to a substrate  41  used as a part of the molecule propagation channel  40 . Although only a few kinesins  46  corresponding to the current position of the microtubule  47  are depicted in the figure for simplification purpose, kinesins  46  are fixed to the entire range of the molecule propagation channel  40  along a groove extending from the molecular transmitter  20  to the molecular receiver  30 . A short single-stranded nucleotide  45  is attached to the microtubule  47 . The short single-stranded nucleotide  45  is designed so as to be complementary with respect to a part of the long single-stranded nucleotide  25  bound to the molecular capsule  10 . 
     As illustrated in  FIG. 8B , the short single-stranded nucleotide  45  attached to the microtubule  47  which moves along the propagation path, and the long single-stranded nucleotide  25  attached to the molecular capsule  10  which are transmitted from the molecular transmitter  20  are bound to each other using a specific double stranding reaction (hybridization). Then, the molecular capsule  10  is towed by the microtubule (rail molecule)  47  to the molecular receiver  30  (not shown in  FIG. 8B ). 
     If lysophosphatidylcholine solution  60 A is used as the chemical substance for encapsulating the information molecule  15  existing in the molecular transmitter  20  into the molecular capsule  10  as illustrated in  FIG. 3 , it is necessary for the molecular capsule  10  to be split from the molecular transmitter  20  with a single-stranded nucleotide  25 . Accordingly, single-stranded nucleotides  25  are attached to the outer surface of the molecular transmitter  20  in advance. When membrane fission occurs to produce the molecular capsule  10  under the application of lysophosphatidylcholine, the molecular capsule  10  with a single-stranded nucleotide  25  and containing the information molecule  15  inside can be emitted from the molecular transmitter  20 . 
     If solution  60 B containing phospholipid micelle is used as the chemical substance for encapsulating the information molecules  15  existing in the molecular transmitter  20  into the molecular capsule  10  as illustrated in  FIG. 4 , it is necessary for the molecular capsule  10  to be emitted from the molecular transmitter  20  with a single-stranded nucleotide  25 . Accordingly, single-stranded nucleotides  25  are dispersed in the molecular transmitter  20  in advance. When a molecular capsule  10  encapsulating an information molecule  15  is produced and emitted from the molecular transmitter  20  under the application of the solution  60 B, a single-stranded nucleotide  25  may be attached to the surface of the molecular capsule  10 . Consequently, the molecular capsule  10  with a single-stranded nucleotide  25  is emitted from the molecular transmitter  20 , as illustrated in  FIG. 8A . 
     If solution  60 C containing antimicrobial peptide is used as the chemical substance for encapsulating the information molecules  15  existing in the molecular transmitter  20  into the molecular capsule  10  as illustrated in  FIG. 5 , it is necessary for the molecular capsule  10  placed in advance near the molecular transmitter  20  with a single-stranded nucleotide  25 . Accordingly, a single-stranded nucleotide  25  is attached to the molecular capsule  10  in advance. In this case, the molecular capsule  10  into which the information molecule  15  is introduced through an pore is loaded on and carried by the microtubule  47  as illustrated  FIG. 8B . 
     On the other hand, at the molecular receiver  30 , the molecular capsule  10  has to be unloaded from the microtubule  47 . Accordingly, long single-stranded nucleotides  35  which are complementary with respect to the single-stranded nucleotide  25  attached to the molecular capsule  10  are attached to the outer surface of the molecular receiver  30 , as illustrated in  FIG. 9A . It is more stable for the single-stranded nucleotide  25  attached to the molecular capsule  10  in its energy state to hybridize with the complementary single-stranded nucleotide  35  attached to the molecular receiver  30 , rather than to hybridize with the short single-stranded nucleotide  45  attached to the microtubule  47 . Consequently, when the microtubule  47  transporting the molecular capsule  10  comes closer to the molecular receiver  30 , the double strand between the single-stranded nucleotide  25  of the molecular capsule  10  and the short single-stranded nucleotide  45  attached to the microtubule  47  is undone (dehybridization), and a new double strand is formed between the complementary single-stranded nucleotide  35  attached to the molecular receiver  30  and the single-stranded nucleotide  25  attached to the molecular capsule  10 , as illustrated in  FIG. 9B . 
     If solution  60 D containing lanthanum ion is used as the chemical substance for taking the information molecules  15  into the molecular receiver  30  through fusion of the molecular capsule  10 , as illustrated in  FIG. 6 , it is necessary to cut off the double-stranded nucleotides between the single-stranded nucleotide  25  attached to the molecular capsule  10  and the complementary single-stranded nucleotide  35  attached to the outer surface of the molecular receiver  30  to facilitate the fusion. Accordingly, a solution containing a restriction enzyme capable of cutting off the specific double-stranded nucleotides is applied after hybridization has occurred between the single-stranded nucleotide  25  and  35 . The solution containing restriction enzyme may be applied before the solution  60 D containing lanthanum ion is applied, or alternatively, the restriction enzyme may be mixed into the solution  60 D containing lanthanum ion in advance and the mixed solution may be applied to the molecular capsule  10  and the molecular receiver  30 . 
     If solution  60 C containing antimicrobial peptide is used as the chemical substance for decapsulating the information molecules  15  from the molecular capsule  10  and introducing it into the molecular receiver  30  through the pores  10   a  and  30   a , as illustrated in  FIG. 7 , the hybridized double strand does not affect the receiving process of information molecule  15 . Consequently, the cut off process of double-stranded nucleotides described above is not required. 
     In the examples described above, although the complementary single-stranded nucleotides are attached to the surface of the molecular receiver  30 , they may be fixed to the substrate surface near the molecular receiver  30 . In this case, the single-stranded nucleotide  25  attached to the molecular capsule  10 , which have propagated to the vicinity of the molecular receiver  30 , is hybridized with one of the complementary single-stranded nucleotides  35  fixed to the substrate. Then, after or simultaneously with application of the solution containing restriction enzyme to the hybridized double-stranded nucleotides, the solution  60 D containing lanthanum ion is applied to cause the molecular capsule  10  to fuse into the molecular receiver  30 . Alternatively, the solution  60 C containing antimicrobial peptide may be applied to the molecule capsule  10  unloaded to the substrate and the molecular receiver  30  to form the pores  10   a  and  30   a , respectively, for allowing the information molecule  15  to escape from the molecular capsule  10  and get into the molecular receiver  30 . 
     As has been described, a molecular communication system in which information molecules existing in the molecular transmitter are encapsulated into a molecular capsule, propagate to the molecular receiver, and are introduced into the molecular receiver is realized. This molecular communication system is advantageous because undesirable information loss caused by denaturalization of the information molecules due to the interaction with other molecules existing in the propagation environment or due to environmental factors such as temperature or pH can be avoided. As a result, the reliability in information communication can be improved. This molecular communication system can be applied to a communication between nano-scale devices that cannot use electromagnetic waves by capability or environmental reasons unlike in the conventional communication systems, as well as to an operational control of nanomachines that are not composed by electronic devices or equipments and cannot be driven by electronic signals. 
     Because the molecular communication system is driven and operated by chemical or biochemical energy, and information is encoded in nano-scale molecules, high-density information transmission can be achieved with less energy consumption compared with the conventional communication systems. 
     Unlike the conventional communication systems, biochemical reaction or status occurring at the transmitter represented by the biochemical molecules or the concentration of biochemical molecules can be transmitted as it is to the receiver under protection by the molecular capsule. Thus, a novel communication system based on biochemical reactions can be provided. 
     This international application claims the benefit of the priority date of Japanese Patent Application No. 2006-126699 filed on Apr. 28, 2006, and the entire content of which application is incorporated herein by reference.