Development, Practice, and Perspectives for DNA Enzyme Systems
Kevin MacVittie1 , Petra Kraus2*
1Department of Chemistry & Biomolecular Sciences, Clarkson University, Potsdam, NY 13699
2Department of Biology, Clarkson University, Potsdam, NY 13699
*Corresponding Author, E-mail: firstname.lastname@example.org
DNAzymes are still fairly recent man-made additions to the growing spectrum of synthetic molecules dramatically advancing the field of biomolecular science. These catalytically active nucleic acids have great potential in personalized medicine and as internal biosensors owing to their low immunogenicity, as well as in bio-computing, because of their robust nature and large data storage capacity. Their future potential is evident in areas that range from the development of biofuel cells to power implanted electronics, like pacemakers, where they could exceed capabilities and circumvent obstacles of existing protein-based catalysis.
DNAzyme, biosensor, bio-computing, catalytic nucleic acid, biofuel cell
Since their synthesis in 1994  DNA-based enzymes have evolved into an exciting area of biochemistry, molecular biotechnology and bio-computing. The catalytic activity of short stranded nucleic acids was first discovered over thirty years ago when naturally occurring ribonucleic acid (RNA) molecules were discovered to act as catalysts in reactions such as phosphodiester bond hydrolysis, thus named ribozymes . Translation of RNA into protein is accomplished by a ribozyme in the active center of cellular ribosomes . Most RNAs are relatively unstable molecules, as their intended use only requires short lifespans in vivo, while their transcriptional origin, the deoxyribonucleic acid (DNA) is far more robust, rendering DNA a more suitable molecule for most approaches .
As known to date, nature has not generated catalytically active DNA in vivo to the extent it has with RNA-based ribozymes , yet Mankind succeeded in developing catalytically active short stranded oligonucleotides termed deoxyribozymes or DNAzymes synthetically . While DNAzymes are currently not utilized in commercial applications, the fundamental research behind their capabilities is abundant [1,2,4-6]. The primary use for DNAzymes lies in the manipulation of nucleic acids, whether it be their cleavage  or ligation ; however, more atypical uses have been found, including the reaction of metal ions with porphyrin rings . Much like traditional protein enzymes, DNAzymes exhibit a high level of selectivity and specificity. This is intrinsically a result of their construction from nucleic acids: small molecules notorious for their exceptionally elevated specificity and selectivity to their given conjugate base pair .
DNAzymes present advantages over traditional enzymes. DNA is well-known for its long-term stability at a wide range of temperatures and is even considered an attractive alternative for long-term data storage , whereas protein-based enzymes are typically more sensitive to fluctuations in temperature, and could undergo undesired conformational changes or denaturation. Furthermore the ability of DNA to be stored in a dry state allows for a much higher level of convenience when dealing with the transportation and distribution of DNAzyme-based technologies . Following this logic, DNAzymes have been immobilized on electronic transducers  and nanoparticles  for use in detection systems, for bio-computing architectures and for their use as molecular switches in signal amplification .
The lack of naturally occurring DNAzymes in vivo, requires their synthesis in vitro. However, prior to mass-production of any DNAzyme, a desirable catalytic activity and target specificity must be confirmed. Therefore, libraries with large populations of fixed-length random sequence oligonucleotides are generated and screened for their interaction with a compound of interest via Systematic Evolution of Ligands by Exponential Enrichment (SELEX) . Purified ligated compounds are typically isolated and amplified by PCR to generate a large quantity of highly specific DNAzymes . Recently it has been shown that enzyme function can be achieved by molecular in vitro evolution from a non-catalytic sequence, leading to a DNAzyme with RNA cleavage properties .
Applications of DNAzymes
DNAzymes in Cancer Treatment
Since their development, DNAzymes have been used for a variety of applications. One of their greatest potentials within the medical research community is the manipulation and silencing of RNA pathways for the inhibition of gene expression, typically for use in cancer therapy. With this in mind, a “general purpose” RNA-cleaving Mg2+ dependent DNAzyme was synthesized . This DNAzyme, called 10-23 DNA Enzyme, consists of two substrate-recognition domains of approximately eight bases separated by a 15 nucleotide catalytic domain. The domain-recognition “arms” can be tailored to any set of complimentary RNA bases, resulting in the catalyzed cleavage of mRNA. In this context, a promising use for DNAzymes could lie in targeting osteosarcoma at the source . Osteosarcoma is a debilitating cancer typically weakening the bones of adolescents and young-adults and commonly metastasizing to the lungs . Most cases of high-grade osteosarcoma are found to have increased expression of c-jun, a proto-oncogene [19,20]. The DZ13 DNAzyme catalyzed gene silencing could stimulate apoptosis of osteosarcoma cells by the down-regulation of c-jun mRNA [18,19,21,22], while having no adverse effect on cell proliferation of non-osteosarcoma cells. The first clinical trial in humans for the treatment of basal cell carcinoma (BCC) with DZ13 successfully completed Phase 1, showing decreased expression of c-jun in patients with nodular BCC, while no drug-related serious side effects were reported . These promising results could pave the way for the use of DNAzyme DZ13 as a cancer treatment drug for controlled apoptosis of cancer cells with obvious and significant implications for future cancer treatments .
DNAzymes in Bio-computing Systems
Aside from their application in cancer therapy, DNAzymes have been used extensively in the realm of bio-computing. Contrary to popular belief, a vast majority of bio-computing does not aim to compete as an alternative to modern silicon computing. Rather, bio-computation focuses on the development of architectures for interfacing existing computing motifs with living systems in biological environments. This is typically in the form of chemical and biochemical interface systems that can directly interact with biomolecules, but also communicate with digital systems through optical or electric measurements . One line of focus lies in the creation of systems capable of performing various Boolean logic operations, from relatively simple realizations such as AND and OR [25-28] to more complicated architectures including XOR, NOR, NAND, INHIB, and XNOR [29-42]. These Boolean logic motifs can then be integrated into larger autonomous “physio-diagnostic” devices, capable of real-time monitoring of living systems with built-in logic .
These bio-computing devices are often realized using enzymes, and similar biomolecules capable of direct interaction with biological systems [44-47]. Horseradish peroxidase (E.C. 220.127.116.11) is an enzyme frequently used in bio-computing owing to its ability to oxidize common redox species and to participate in colorimetric reactions . Therefore, it is logical that this would be one of the first characteristics that researchers attempted to mimic using DNAzymes. This was successfully done with the development of a guanine-rich DNAzyme, capable of complexing with a hemin molecule for the catalysis of the oxidation of common redox species, such as 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), in the presence of hydrogen peroxide [49,50]. When presented with a specifically programmed mRNA scaffold and a hemin molecule the activity of this DNAzyme was activated, allowing for the controllable oxidation of photoactive redox dyes, such as ABTS. This is essential to bio-computing, because almost all bio-computation motifs include a final step resulting in the controlled oxidation or reduction of a dye. This allows for both qualitative and quantitative results to be measured, or for the storage of information in the case of memory units .
Conclusions and Future Perspectives
With small molecule gene silencing strategies on the rise, DNAzymes have great potential as therapeutic agents. The apparent lack of off-target effects commonly seen in higher organisms for gene silencing approaches using antisense and siRNA, is possibly a result of the self-sufficient cleavage properties of DNAzymes, whereas siRNAs operate via the cell endogenous Dicer/RISC mechanism . Sequence composition induced interferon responses common to antisense RNA mediated long double-stranded RNA molecules, which cause a more global mRNA degeneration in mammals  have not been described for DNAzymes so far. Nevertheless, similar to any establishment of siRNA mediated gene knockdown, a range of molecules might need to be tested to achieve optimal target RNA cleavage and control experiments using a randomized sequence flanking the catalytic core instead of the target binding sequence are imperative. Toxic effects due to the use of cationic lipofectants as DNAzyme delivery method have been described . Since DNAzymes act through selective binding and cleavage of mRNA, this method, like all gene silencing approaches will merely achieve a knockdown of mRNA transcripts. Therefore unlike classic and conditional gene targeting by homologous recombination  DNAzymes might be limited in modeling gene function and disease, depending on the relevance of the target gene or when a complete loss-of function approach is crucial. The potential risk of DNA mediated mutagenesis due to random integration of foreign DNA fragments into the host genome is further to be considered when using DNAzymes as therapeutic agent. While DNA is generally more stable than ribonucleic acids, DNAzymes, too, are vulnerable to exonuclease-mediated degradation, and might therefore require direct delivery to a target cell. This could exclude DNAzymes from the treatment of pathophysiological conditions where bioavailability is challenging due to difficulties in DNAzyme delivery or impaired cellular uptake thereof. Similar to work with antisense oligonucleotides, ribozymes and aptamers, modifications to increase DNAzyme half-life for in vivo applications have been explored [53,55-58]. Phosphorothioate modifications to confer endonuclease resistance as commonly used in ribozymes and aptamers inflict a similar toxic and off-target effect when used in DNAzymes [59-62]. Other modifications, like terminal stem-loop hairpins of the substrate binding arms  or a 3’-3’ inverted nucleotide at the 3’terminus of the DNAzyme molecule  appear promising.
With the continued development of advanced artificial biomolecular motifs, such as DNAzymes, bio-computational and biomedical architectures, solutions previously only envisioned in science fiction writings, become more realistic. The potential for bio-catalytic species, like traditional protein enzymes, produced from highly specific and robust components, like DNA, is limitless. One obvious field that could be significantly impacted is that of biofuel cell technologies. Typically constructed from redox enzymes or nanoparticles, biofuel cells utilize their catalytic nature to extract energy from their surroundings . One of the most potentially hopeful of these circumstances is the implantation in animals and humans, where glucose and oxygen are typically used as “fuel”. The goal is for this harvested energy to be used to power implanted electronics, such as pacemakers . One of the greatest limitations facing modern implantable biofuel cells is the long-term stability of the enzymes immobilized on their surface. If DNAzymes were developed that were capable of the bio-catalytic redox catalysis of glucose and oxygen, the most common sources of fuel for implantable biofuel cells , future biofuel cell electrodes could be developed with the ability to outlast even the most robust protein-based enzyme electrodes.
Future applications for DNAzymes in cancer treatment are apparent, and steps have been taken towards their realization. Continued research and interest in this field could result in a highly specific and effective DNAzyme-based anti-tumor cell treatment. Given the high specificity of DNAzymes, treatments could be tailored to specific mutations of a cancer cell; for example by targeting specific nucleotide sequences that result in cancerous characteristics and therefore distinguish the cancer cell from healthy neighbors. Additionally, being composed of bare DNA, DNAzymes inherently represent a minimal risk of unintended toxicity, unlike current chemotherapy compounds. This being said, any technology involving the direct interaction with a host cell’s nucleic acids must be carefully tested and regulated to ensure its safety by minimizing off-target effects. No cancer treatment would be beneficial to any patient if the induction of apoptosis would not be tumor cell-specific.
DNAzymes show promising potential in many other areas aside from the ones mentioned above. Whenever targeting at a molecular level is required, DNAzymes might be of use, for example in targeting RNAs encoding viral structures causative of human immunodeficiency virus infection (HIV) , dengue fever , “bird flu” (H1N1 and related strains) , severe acute respiratory syndrome (SARS)  and more recent threats to society like the middle east respiratory syndrome (MERS) or Ebola. DNAzymes could provide a novel option in such areas desperate for urgent solutions.
Treatment with DNAzyme DZ1 targeting the late membrane protein 1 (LPM1) of the Epstein Barr virus, an oncogenic factor thought as major contibutor in nasopharyngeal carcinoma (NPC) showed increased radiosensitivity and decreased angiogenesis in LPM1-induced NPC . Another clinical trial to test the efficacy and safety of the DNAzyme SB010 in allergen-induced asthmatic responses aiming at silencing GATA3 was also recently completed  , while trials for a topical application of SB011 to treat mild to moderate atopic dermatitis as well as intrarectally applied SB012 to treat active ulcerative colitis are currently recruiting (www.ClinicalTrials.gov). Technological advances allow for further fine tuning of the activity of DNAzymes by using a L-ribose (L-RNA) sugar backbone instead of the naturally occurring D-ribose (D-RNA) [71,72]. This has the potential to overcome current obstacles for broader implications of DNAzymes in bioanalytical, therapeutic or diagnostic applications hampered by RNAse-mediated substrate degradation in complex biological samples . In combination with a low immunogenicity of DNAzymes and high precision at a nucleic acid base level, DNAzymes have the potential to excel in personalized medicine just as much as in biofuel cell technologies. Future combined efforts of biomolecular, biochemical and bioinformatic sciences improving DNAzymes and identifying more possible targets and applications will also impact on the evolving field of Synthetic Biology [6,73] (see Figure 1).
Figure 1: Multidisciplinary efforts make way for current and future applications for DNA Enzyme Systems in the medical and biotechnological fields. (DNAzyme schematic adapted from )
This review was inspired by course BY586, a trans-disciplinary upper level course on Molecular Biotechnology at Clarkson University.
- Breaker RR, Joyce GF (1994). A DNA enzyme that cleaves RNA. Chem Biol 1: 223-229.
- Kruger K, Grabowski PJ, Zaug AJ, Sands J, Gottschling DE, Cech TR (1982). Self-splicing RNA: autoexcision and autocyclization of the ribosomal RNA intervening sequence of Tetrahymena. Cell 31: 147-157.
- Palade GE (1955). A small particulate component of the cytoplasm. J Biophys Biochem Cytol 1: 59-68.
- Cuenoud B, Szostak JW (1995). A DNA metalloenzyme with DNA ligase activity. Nature 375: 611-614.
- Hu R, Liu T, Zhang XB, Yang Y, Chen T, Wu C, Liu Y, Zhu G, Huan SY, Fu T, Tan W (2015). DLISA: A DNAzyme-based ELISA for protein enzyme-free immunoassay of multiple analytes. Anal Chem.
- Breaker RR, Joyce GF (2014). The expanding view of RNA and DNA function. Chem Biol 21: 1059-1065.
- Li Y, Sen D (1996). A catalytic DNA for porphyrin metallation. Nat Struct Biol 3: 743-747.
- Ellington AD, Szostak JW (1990). In vitro selection of RNA molecules that bind specific ligands. Nature 346: 818-822.
- Goldman N, Bertone P, Chen S, Dessimoz C, LeProust EM, Sipos B, Birney E (2013). Towards practical, high-capacity, low-maintenance information storage in synthesized DNA. Nature 494: 77-80.
- Tribioli C, Lufkin T (2006). Long-term room temperature storage of high-quality embryonic stem cell genomic DNA extracted with a simple and rapid procedure. J Biomol Tech 17: 249-251.
- Willner I, Zayats M (2007). Electronic aptamer-based sensors. Angew Chem Int Ed Engl 46: 6408-6418.
- Lu Y, Liu J (2006). Functional DNA nanotechnology: emerging applications of DNAzymes and aptamers. Curr Opin Biotechnol 17: 580-588.
- Bone SM, Lima NE, Todd AV (2015). DNAzyme switches for molecular computation and signal amplification. Biosens Bioelectron 70: 330-337.
- Tuerk C, Gold L (1990). Systematic evolution of ligands by exponential enrichment: RNA ligands to bacteriophage T4 DNA polymerase. Science 249: 505-510.
- Gysbers R, Tram K, Gu J, Li Y (2015). Evolution of an Enzyme from a Noncatalytic Nucleic Acid Sequence. Sci Rep 5: 11405.
- Santoro SW, Joyce GF (1997). A general purpose RNA-cleaving DNA enzyme. Proc Natl Acad Sci U S A 94: 4262-4266.
- Dass CR, Khachigian LM, Choong PF (2008). c-Jun Is critical for the progression of osteosarcoma: proof in an orthotopic spontaneously metastasizing model. Mol Cancer Res 6: 1289-1292.
- Longhi A, Errani C, De Paolis M, Mercuri M, Bacci G (2006). Primary bone osteosarcoma in the pediatric age: state of the art. Cancer Treat Rev 32: 423-436.
- Franchi A, Calzolari A, Zampi G (1998). Immunohistochemical detection of c-fos and c-jun expression in osseous and cartilaginous tumours of the skeleton. Virchows Arch 432: 515-519.
- Papachristou DJ, Batistatou A, Sykiotis GP, Varakis I, Papavassiliou AG (2003). Activation of the JNK-AP-1 signal transduction pathway is associated with pathogenesis and progression of human osteosarcomas. Bone 32: 364-371.
- Zhang G, Dass CR, Sumithran E, Di Girolamo N, Sun LQ, Khachigian LM (2004). Effect of deoxyribozymes targeting c-Jun on solid tumor growth and angiogenesis in rodents. J Natl Cancer Inst 96: 683-696.
- Fahmy RG, Waldman A, Zhang G, Mitchell A, Tedla N, Cai H, Geczy CR, Chesterman CN, Perry M, Khachigian LM (2006). Suppression of vascular permeability and inflammation by targeting of the transcription factor c-Jun. Nat Biotechnol 24: 856-863.
- Cho EA, Moloney FJ, Cai H, Au-Yeung A, China C, Scolyer RA, Yosufi B, Raftery MJ, Deng JZ, Morton SW, Hammond PT, Arkenau HT, Damian DL, Francis DJ, Chesterman CN, Barnetson RS, Halliday GM, Khachigian LM (2013). Safety and tolerability of an intratumorally injected DNAzyme, Dz13, in patients with nodular basal-cell carcinoma: a phase 1 first-in-human trial (DISCOVER). Lancet 381: 1835-1843.
- Poghossian A, Katz E, Schoning MJ (2015). Enzyme logic AND-Reset and OR-Reset gates based on a field-effect electronic transducer modified with multi-enzyme membrane. Chem Commun (Camb) 51: 6564-6567.
- Guo XF, Zhang DQ, Zhu DB (2004). Logic control of the fluorescence of a new dyad, spiropyran-perylene diimide-spiropyran, with light, ferric ion, and proton: Construction of a new three-input "AND" logic gate. Advanced Materials 16: 125-+.
- De Silva APG, H.Q.N.; McCoy, C.P. (1997). J Am Chem Soc 119: 7891-7892. .
- De Silva APG, H.Q.N.; McCoy, C.P. (1993). Nature 364: 42-44.
- De Silva APG, H.Q.N.; Maguire, G.E.M. (1994). J Chem Soc, Chem Commun 1213-1214.
- de Silva AP, McClenaghan ND (2002). Simultaneously multiply-configurable or superposed molecular logic systems composed of ICT (internal charge transfer) chromophores and fluorophores integrated with one- or two-ion receptors. Chemistry 8: 4935-4945.
- Credi A, Balzani V, Langford SJ, Stoddart JF (1997). Logic operations at the molecular level. An XOR gate based on a molecular machine. Journal of the American Chemical Society 119: 2679-2681.
- Wang Z, Zheng G, Lu P (2005). 9-(cycloheptatrienylidene)-fluorene derivative: remarkable ratiometric pH sensor and computing switch with NOR logic gate. Org Lett 7: 3669-3672.
- Turfan B, Akkaya EU (2002). Modulation of boradiazaindacene emission by cation-mediated oxidative PET. Org Lett 4: 2857-2859.
- Straight SD, Liddell PA, Terazono Y, Moore TA, Moore AL, Gust D (2007). All-photonic molecular XOR and NOR logic gates based on photochemical control of fluorescence in a fulgimide-porphyrin-dithienylethene triad. Advanced Functional Materials 17: 777-785.
- De Silva APD, I.M.; Gunaratne, H.Q.N.; Gunnlaugsson, T.; Maxwell, P.R.S.; Rice, T.E. (1999). J Am Chem Soc 121: 1393-1394.
- Zong GQ, Xian L, Lu GX (2007). L-Arginine bearing an anthrylmethyl group: fluorescent molecular NAND logic gate with H+ and ATP as inputs. Tetrahedron Letters 48: 3891-3894.
- Baytekin HT, Akkaya EU (2000). A molecular NAND gate based on Watson-Crick base pairing. Org Lett 2: 1725-1727.
- Li L, Yu MX, Li FY, Yi T, Huang CH (2007). INHIBIT logic gate based on spiropyran sensitized semiconductor electrode. Colloids and Surfaces a-Physicochemical and Engineering Aspects 304: 49-53.
- Gunnlaugsson T, Mac Donaill DA, Parker D (2001). Lanthanide macrocyclic quinolyl conjugates as luminescent molecular-level devices. J Am Chem Soc 123: 12866-12876.
- Gunnlaugsson T, Mac Donail DA, Parker D (2000). Luminescent molecular logic gates: the two-input inhibit (INH) function. Chemical Communications: 93-94.
- de Sousa M, de Castro B, Abad S, Miranda MA, Pischel U (2006). A molecular tool kit for the variable design of logic operations (NOR, INH, EnNOR). Chemical Communications: 2051-2053.
- Qian J, Qian X, Xu Y, Zhang S (2008). Multiple molecular logic functions and molecular calculations facilitated by surfactant's versatility. Chem Commun (Camb): 4141-4143.
- Luxami V, Kumar S (2008). Molecular half-subtractor based on 3,3 '- bis(1H-benzimidazolyl-2-yl)[1,1 ']-binaphthalenyl-2,2 '-diol. New Journal of Chemistry 32: 2074-2079.
- Katz E, MacVittie K (2013). Implanted biofuel cells operating in vivo – methods, applications and perspectives – feature article. Energy & Environmental Science 6: 2791.
- Bocharova V, Zavalov O, MacVittie K, Arugula MA, Guz NV, Dokukin ME, Halamek J, Sokolov I, Privman V, Katz E (2012). A biochemical logic approach to biomarker-activated drug release. Journal of Materials Chemistry 22: 19709-19717.
- MacVittie K, Halamek J, Katz E (2012). Enzyme-based D-flip-flop memory system. Chem Commun (Camb) 48: 11742-11744.
- MacVittie K, Halamek J, Katz E (2012). Enzyme-Based T-Flip-Flop Memory System. International Journal of Unconventional Computing 8: 383-389.
- Pita M, Strack G, MacVittie K, Zhou J, Katz E (2009). Set-Reset Flip-Flop Memory Based on Enzyme Reactions: Toward Memory Systems Controlled by Biochemical Pathways. Journal of Physical Chemistry B 113: 16071-16076.
- MacVittie K, Katz E (2014). Biochemical flip-flop memory systems: essential additions to autonomous biocomputing and biosensing systems. International Journal of General Systems 43: 722-739.
- Witting PK, Travascio P, Sen D, Mauk AG (2001). A DNA oligonucleotide-hemin complex cleaves t-butyl hydroperoxide through a homolytic mechanism. Inorg Chem 40: 5017-5023.
- Travascio P, Witting PK, Mauk AG, Sen D (2001). The peroxidase activity of a hemin--DNA oligonucleotide complex: free radical damage to specific guanine bases of the DNA. J Am Chem Soc 123: 1337-1348.
- Leuschner PJ, Ameres SL, Kueng S, Martinez J (2006). Cleavage of the siRNA passenger strand during RISC assembly in human cells. EMBO Rep 7: 314-320.
- Sen GC (2001). Viruses and interferons. Annu Rev Microbiol 55: 255-281.
- Cairns MJ, Saravolac EG, Sun LQ (2002). Catalytic DNA: a novel tool for gene suppression. Curr Drug Targets 3: 269-279.
- Kraus P, Sivakamasundari V, Xing X, Lufkin T (2014). Generating mouse lines for lineage tracing and knockout studies. Methods Mol Biol 1194: 37-62.
- Dass CR, Saravolac EG, Li Y, Sun LQ (2002). Cellular uptake, distribution, and stability of 10-23 deoxyribozymes. Antisense Nucleic Acid Drug Dev 12: 289-299.
- Lu ZX, Ye M, Yan GR, Li Q, Tang M, Lee LM, Sun LQ, Cao Y (2005). Effect of EBV LMP1 targeted DNAzymes on cell proliferation and apoptosis. Cancer Gene Ther 12: 647-654.
- Bhindi R, Fahmy RG, Lowe HC, Chesterman CN, Dass CR, Cairns MJ, Saravolac EG, Sun LQ, Khachigian LM (2007). Brothers in arms: DNA enzymes, short interfering RNA, and the emerging wave of small-molecule nucleic acid-based gene-silencing strategies. Am J Pathol 171: 1079-1088.
- Fahmy RG, Khachigian LM (2004). Locked nucleic acid modified DNA enzymes targeting early growth response-1 inhibit human vascular smooth muscle cell growth. Nucleic Acids Res 32: 2281-2285.
- Wahlestedt C, Salmi P, Good L, Kela J, Johnsson T, Hokfelt T, Broberger C, Porreca F, Lai J, Ren K, Ossipov M, Koshkin A, Jakobsen N, Skouv J, Oerum H, Jacobsen MH, Wengel J (2000). Potent and nontoxic antisense oligonucleotides containing locked nucleic acids. Proc Natl Acad Sci U S A 97: 5633-5638.
- Fluiter K, ten Asbroek AL, de Wissel MB, Jakobs ME, Wissenbach M, Olsson H, Olsen O, Oerum H, Baas F (2003). In vivo tumor growth inhibition and biodistribution studies of locked nucleic acid (LNA) antisense oligonucleotides. Nucleic Acids Res 31: 953-962.
- Guvakova MA, Yakubov LA, Vlodavsky I, Tonkinson JL, Stein CA (1995). Phosphorothioate oligodeoxynucleotides bind to basic fibroblast growth factor, inhibit its binding to cell surface receptors, and remove it from low affinity binding sites on extracellular matrix. J Biol Chem 270: 2620-2627.
- Rockwell P, O'Connor WJ, King K, Goldstein NI, Zhang LM, Stein CA (1997). Cell-surface perturbations of the epidermal growth factor and vascular endothelial growth factor receptors by phosphorothioate oligodeoxynucleotides. Proc Natl Acad Sci U S A 94: 6523-6528.
- Abdelgany A, Wood M, Beeson D (2007). Hairpin DNAzymes: a new tool for efficient cellular gene silencing. J Gene Med 9: 727-738.
- Southcott M, MacVittie K, Halamek J, Halamkova L, Jemison WD, Lobel R, Katz E (2013). A pacemaker powered by an implantable biofuel cell operating under conditions mimicking the human blood circulatory system--battery not included. Phys Chem Chem Phys 15: 6278-6283.
- Singh N, Ranjan A, Sur S, Chandra R, Tandon V (2012). Inhibition of HIV-1 Integrase gene expression by 10-23 DNAzyme. J Biosci 37: 493-502.
- Baum L, Olson KE, Chan PK, Lam WY (2014). DNAzymes for treatment of dengue fever. Hong Kong Med J 20 Suppl 4: 42-43.
- Evdokimov AA, Mazurkova NA, Malygin EG, Zarytova VF, Levina AS, Repkova MN, Zagrebelnyi SN, Netesova NA (2013). [Design of deoxyribozymes for inhibition of influenza A virus]. Mol Biol (Mosk) 47: 83-93.
- Fukushima A, Fukuda N, Lai Y, Ueno T, Moriyama M, Taguchi F, Iguchi A, Shimizu K, Kuroda K (2009). Development of a chimeric DNA-RNA hammerhead ribozyme targeting SARS virus. Intervirology 52: 92-99.
- Yang L, Liu L, Xu Z, Liao W, Feng D, Dong X, Xu S, Xiao L, Lu J, Luo X, Tang M, Bode AM, Dong Z, Sun L, Cao Y (2015). EBV-LMP1 targeted DNAzyme enhances radiosensitivity by inhibiting tumor angiogenesis via the JNKs/HIF-1 pathway in nasopharyngeal carcinoma. Oncotarget 6: 5804-5817.
- Krug N, Hohlfeld JM, Kirsten AM, Kornmann O, Beeh KM, Kappeler D, Korn S, Ignatenko S, Timmer W, Rogon C, Zeitvogel J, Zhang N, Bille J, Homburg U, Turowska A, Bachert C, Werfel T, Buhl R, Renz J, Garn H, Renz H (2015). Allergen-induced asthmatic responses modified by a GATA3-specific DNAzyme. N Engl J Med 372: 1987-1995.
- Wyszko E, Mueller F, Gabryelska M, Bondzio A, Popenda M, Barciszewski J, Erdmann VA (2014). Spiegelzymes(R) mirror-image hammerhead ribozymes and mirror-image DNAzymes, an alternative to siRNAs and microRNAs to cleave mRNAs in vivo? PLoS One 9: e86673.
- Tram K, Xia J, Gysbers R, Li Y (2015). An Efficient Catalytic DNA that Cleaves L-RNA. PLoS One 10: e0126402.
- Hollenstein M (2012). Nucleoside triphosphates--building blocks for the modification of nucleic acids. Molecules 17: 13569-13591.
- Barar J, Omidi Y (2012). Translational Approaches towards Cancer Gene Therapy: Hurdles and Hopes. Bioimpacts 2: 127-143.