Abstract:
A method of using a DNA structure includes forming a DNA structure including a plurality of spaces; attaching a DNA building block to the spaces; contacting the DNA building block with a clinical specimen; and separating the DNA building block from the DNA structure. After the DNA building block is separated from the DNA structure, the method may further include attaching a new DNA building block to the spaces. The DNA building block includes a first DNA strand attached to the spaces; and a second DNA strand attached to the first DNA strand.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2013-0096882, filed on Aug. 14, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates DNA structures, and in particular, to methods of re-using DNA structures. 
         [0004]    2. Description of the Related Art 
         [0005]    DNA has a double helix structure, each helix consisting of chemical structure units referred to as nucleotides which is comprised of a base, a ugar (deoxyribose), and at least one phosphate group. There are four nucleobases: adenine (A), cytosine (C), guanine (G), and thymine (T). The sequence of nucleobases, that is, the base sequence, determines genetic information which directs the functions of a living thing. Protein and generic information may vary with the base sequence. 
         [0006]    Recently, a human genome project for encoding the base sequence of the entire human genome has been completed, which has led to a substantial development in the diagnosis and treatment of intractable diseases by using genes. Accordingly, an era of, so called, customized or personalized medicine has opened. 
         [0007]    A molecular biological gene examination using DNA may be employed to identify the existence and amount of a particular gene in a specimen such as a clinical sample. Thus, a disease may be rapidly and accurately diagnosed. 
         [0008]    Examples of the molecular biological gene examination methods are a polymerase chain reaction (PCR), blotting, and hybridization. Recently, DNA chips are getting attention. 
         [0009]    Such gene examination methods are carried out using various detection kits, which are, in general, disposable. 
       SUMMARY 
       [0010]    Provided are methods of using a DNA structure, the methods decreasing resource consumption and diagnosis costs. 
         [0011]    Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
         [0012]    According to an examplary embodiment, a method of using a DNA structure includes: forming a DNA structure including a plurality of spaces; attaching a DNA building block to the spaces; contacting the DNA building block with a clinical specimen; and separating the DNA building block from the DNA structure. 
         [0013]    The method may further include, after the DNA building block is separated, attaching a new DNA building block to the spaces. 
         [0014]    The DNA building block may include: a first DNA strand attached to the spaces; and a second DNA strand attached to the first DNA strand. 
         [0015]    The separating of the DNA building block from the DNA structure may include annealing the DNA structure with the DNA building block attached thereto. 
         [0016]    The forming of the DNA structure may include: placing a substrate in a 1×TAE/Mg 2+  buffer [Tris-Acetate-EDTA (40 mM Tris, 1 mM EDTA (pH 8.0), 12.5 mM Mg(Ac) 2 )]. 
         [0017]    The second DNA strand may include a material that has a base complementary to a material included in a clinical specimen. The material that has a base complementary to a material included in a clinical specimen may be biotin or an SH functional group. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
           [0019]      FIGS. 1 to 4  shows front views illustrating a method of using a DNA structure according to an embodiment; and 
           [0020]      FIG. 5  shows an example of the DNA structure illustrated in  FIGS. 1 to 4  used together with a different stack structure on a substrate. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. 
         [0022]    Hereinafter, a method of using a DNA structure according to embodiments will be described in detail by referring to the attached drawings. In the drawings, thicknesses of illustrated layers or regions are exaggerated for clarity. 
         [0023]    A two-dimensional periodic lattice formed of coplanar repeating units, each of which is composed of at least two antiparallel nucleic acid multi-crossover molecules and a three-dimensional periodic lattice which may be formed as an extension of the two-dimensional period lattice into a third dimension, such as by interconnecting adjacent two-dimensional lattices by joining together antiparallel nucleic acid multi-crossover molecules in adjacent planes are disclosed in, for example U.S. Pat. No. 6,255,469 to Seeman. The content of U.S. Pat. No. 6,255,469 is incorporated herein by reference. 
         [0024]      FIG. 1  illustrates a DNA structure  30  used for a method of using a DNA structure according to an exemplary embodiment. 
         [0025]    Referring to  FIG. 1 , the DNA structure  30  includes a DNA frame  32  consisting of at least two DNA multi-crossover molecules; and a plurality of spaces  34 , wherein the spaces  34  exist in the DNA frame  32 . The spaces  34  may be periodically arranged in a Y-axis direction at constant intervals. Space groups  34   a,    34   b,  and  34   c,  each consisting of spaces  34  arranged in the Y-axis direction, are arranged in an X-axis direction at certain intervals. The number of the spaces  34  along the X-axis and Y-axis directions may be greater than the number illustrated in  FIG. 1 . That is, the DNA structure  30  is not limited to the structure illustrated in  FIG. 1 , and the total size or the number of the spaces  34  may increase or decrease according to purpose. 
         [0026]    The DNA structure  30  is formed on a substrate (not shown in  FIG. 1 ) by placing the substrate in a 1×TAE/Mg 2+  buffer [Tris-Acetate-EDTA (40 mM Tris, 1 mM EDTA (pH 8.0), 12.5 mM Mg(Ac) 2 )] aqueous solution for a certain period of time by employing a known method disclosed in, for example U.S. Pat. No. 6,255,469. The substrate may be, for example, a silicon substrate. 
         [0027]    Then, as illustrated in  FIG. 2 , a first DNA strand  36  may be attached to each of the spaces  34  of the DNA frame  32 . When the DNA structure  30  is formed, ends of each of the spaces  34  may each include a sticky-end including five or more bases. The bases of the sticky-end may be complementary to those of the first DNA strand  36  in consideration of an attachment of the first DNA strand  36 . Accordingly, only the first DNA strand  36  that has bases complementary to the bases of the sticky-end may be attached to each of the spaces  34  of the DNA frame  32  The first DNA strand  36  is attached to each of the spaces  34  of the DNA structure  30  as follows. The DNA structure  30  is added to an aqueous solution including the first DNA strand  36 , and then, the resultant solution is annealed at, for example, about 40° C. 
         [0028]    Following the attachment of the first DNA strand  36 , a second DNA strand  40  is attached to each side of the first DNA strand  36 . The first and second DNA strands  36  and  40  may be designed such that bases of the first DNA strands  36  and bases of the second DNA strands  40  are complementary to each other to attach the first and second DNA strands  36  and  40 . The second DNA strand  40  may be attached to the first DNA strand  36  as follows. The DNA structure  30  with the first DNA strand  36  attached thereto is added to an aqueous solution including the second DNA strand  40 , and then, heated to a certain temperature. 
         [0029]    The second DNA strand  40  may be designed to have a sticky-end including a base complementary to a target nucleic acid contained in a sample to be tested. Also, the second DNA strand  40  may be coupled to a biotin-streptavidine label. The biotin-streptavidin may be coupled to gold nanoparticles. The second DNA strand  40  may include a SH functional group to which gold nanoparticles or biotin-streptavidine-gold nanoparticles are attached. As such, only a target nucleic acid that has a base complementary to the second DNA strand  40  may be attached to the second DNA strand  40 . Accordingly, by bringing the DNA structure  30  with the second DNA strand  40  attached thereto in contact with a sample such as a biological sample or a clinical specimen, it may be possible to identify that the sample includes a target sequence that is a base complementary to the second DNA strand  40 . When the clinical specimen includes a material that has a base complementary to the second DNA strand  40 , as illustrated in  FIG. 3 , a material  50  that has a base complementary to the second DNA strand  40  is attached to the second DNA strand  40 . 
         [0030]    Thereafter, when the material  50  is attached to the second DNA strand  40 , the DNA structure  30  is annealed at a predetermined temperature. The annealing temperature may be any temperature at which the complementary bond of base pairs of the sticky-end of each of the spaces  34  and the first DNA strand  36  is broken. An annealing temperature and time appropriate for cutting a base pair are well known. The annealing temperature may be adjustable according to external environmental factors of the DNA structure  30 . 
         [0031]    Due to the annealing, the first DNA strand  36  is separated from the spaces  34 , and ultimately, the first and second DNA strands  36  and  40  are separated from the DNA frame  32 . Thus, as illustrated in  FIG. 4 , the remaining DNA structure  30  has the spaces  34  from which the first and second DNA strands  36  and  40  are separated. The DNA structure  30  of  FIG. 4  may also be re-used as described in connection with  FIGS. 2 and 3 . The first and second DNA strands  36  and  40  are also referred to as DNA building blocks. First and second DNA strands  36  and  40  attached to respective repeating unit (or DNA frame) of the DNA structure may be the same or different. 
         [0032]    According to an examplary embodiment, when the DNA structure  30  is used as explained in connection with  FIGS. 1 to 4 , although not illustrated, the DNA structure  30  may be attached to a substrate. The substrate may be a silicon substrate, and may include a transistor to be connected to the DNA structure  30 . 
         [0033]    The DNA structure  30  may not be directly disposed on a substrate  70 , and as illustrated in  FIG. 5 , may be disposed on a stack structure  72  disposed on the substrate  70 . The stack structure  72  may be a DNA layer with no spaces therein. 
         [0034]    As described above, a method of using a DNA structure according to the one or more of the above example embodiments may be appropriate for a multiple re-use of the DNA structure. Accordingly, consumption of resources and costs for forming the DNA structure may decrease. 
         [0035]    Also, in the case of a disposable kit used in the related art, as the number of diagnosis increases, more examination kits are needed. However, when a method of using a DNA structure according to example embodiments is used, a multiple use of a single DNA structure is possible. Accordingly, it is possible to reduce articles to prepare for diagnosis. 
         [0036]    It should be understood that the exemplary embodiments described therein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.