Biomedical Engineering Reference
In-Depth Information
especially after the irst assembly of the genome was completed in 2000, many
researchers have been focusing their efforts on the identiication of crucial
genomic sequences able to provide new avenues for advances in medicine and
biotechnology. More precisely, gene therapy has become extremely popular
because of the possibility to replace defective genes with functional ones to
treat a disease, especially hereditary illnesses. To that purpose, and because
all viruses bind to their hosts and introduce their genetic material as part of
their replication cycle, doctors and molecular biologists have tried to replace
such genetic material inside the viruses with information that enables the
production of more copies of the lacking gene or protein. In other words, they
used viruses as vehicles to transfer useful genetic information inside the host.
Similarly, RNA catalysts have been used as mediators for a variety of organic
reactions and inorganic-particle growth.
1-5
Moreover, small interfering RNAs
evoke a natural defense mechanism called RNA interference, shutting off
viral infection through tagging viral RNA. However, despite these incredible
discoveries, several problems have prevented the spreading of gene therapy
using viral vectors, including dificulties in the targeting, undesired effects
and disruption of other vital genes already in the genome. Therefore, recent
advances in vector technology have suggested the use of vehicles alternative to
viral vectors: for example, the combination of positively charged carriers (e.g.,
liposomes, lipids and nanoparticles) with negatively charged DNA sequences
has been extensively studied to achieve an eficient gene transfection without
the use of viral genes. Recently, it has been suggested that carbon nanotubes
(CNTs) play an important role in the complexation and delivery of gene-
encoding nucleic acids; their use as gene delivery vectors seems promising
because they are readily produced, are stable for long-term storage and
have shown suspendibility in aqueous solutions with low toxicity
in vitro
.
6,7
Additionally, they can be functionalised with several cationic groups to tailor
the delivery. Even with these positive aspects, their combination with nucleic
acids has been more focused on the dispersion of CNTs
(Section 5.2)
and on
the construction of sensors, nanocircuits and nanocomposites
(Section 5.3)
rather than on real gene or cancer therapy
(Section 5.4).
In the following paragraphs we have reported the most relevant
publications concerning the use of CNT-nucleic acid complexes for the tubes'
dispersibility, sensing, gene delivery and cancer therapy.
5.2 INTERACTION OF CNTS WITH NUCLEIC ACIDS
5.2.1 CNTs and DNA
5.2.1.1
DNA favours dispersion and separaon of CNTs
DNA molecule contains three constituents, namely phosphate acid groups,
basic groups and sugar units. The basic groups are adenine, guanine, cytosine
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