**1.3 Interaction with polynucleotides and nucleic acids: non-viral vectors**

The entrance of exogenous genetic material in cells was a key stage in the development of cellular biology. The term "transfection" indicates the transfer of DNA—as a healing agent—into the nuclei of cells of higher organisms. The direct application of this technology in living organisms opened crucial possibilities, like gene therapy and DNA vaccines [25].

Synthetic molecules that can bind polynucleotide fragments (the therapeutic agent) are required to develop new non-viral vectors to transfect in cells, without stimulating an immune response.

Cationic polymers, at physiological pH, are used to condense anionic nucleic acids, through self-assembly driven by electrostatic interactions, into nano-sized complexes called "polyplexes." DNA molecules being compressed to a relatively smaller size able to enter inside the nuclei of cells, facilitating internalization, thus improving transfection efficacy [26].

**Figure 7.**

*The monomeric unit of polyesteramides: (a) PNOBDME; (b) PNOBEE. The asterisk indicates the chiral centre (12C\*) in PNOBDME and (4 C\*) in PNOBEE. Torsion angle φ, along the 11C▬12C\* bond and 3 C▬<sup>4</sup> C\* bond, respectively, is indicated.*

New polyplexes were formulated including cholesteric LC PTOBDME and/or PTOBEE and *new monomeric cationic surfactant molecules* synthesized in our lab to entrap an anionic DNA plasmid. The new polyplexes successfully transfected both in vitro and in vivo in mice, as non-viral vectors for gene therapy*.* Their structures were studied by synchrotron radiation source [22, 27, 28].

New cationic chemical formulations of multifunctional cholesteric LCs PTOBDME and PTOBEE were designed later to directly interact with negatively charged DNA. The functional groups selected to be introduced at the end of the main polyester chains were choline [▬CH2▬CH2▬N+ ▬(CH3)3] and ammonium, defined as [▬CH2▬ CH2▬CH2▬N+ H▬(CH3)2]. Two more new polymers were also formulated with amide groups (▬CONH2) chemically bonded to the end of the lateral hydrophobic chains.

**85**

**Figure 9.**

*Scheme of the synthesis of PNOBEE.*

*Cholesteric Liquid Crystal Polyesteramides: Non-Viral Vectors*

The new cationic cholesteric LC polymers so designed were synthesized as follows: PTOBDME-choline [(C34H36O8)n▬C5H13N]; PTOBEE-choline [(C26H20O8)n ▬C5H13N]; PTOBDME-ammonium [(C34H36O8)n▬C5H13N]; PTOBEE-ammonium [(C26H20O8)n▬C5H13N]; PTOBUME-amide [(C33H33O9N)n]; and PTOBEE-amide

These cationic polymers proved to be biocompatible, able to form polyplexes and capable of successfully condensing and transfecting the DNA into the nucleus cell, protecting DNA from inactivation by blood components. The complexes are sensitive to pH changes, possessing substantial buffering capacity below physiological pH. Their efficiency relies on extensive endosome swelling and rupture that

Since we are mainly interested in the design and chemical modifications of multifunctional cholesteric LC polyesters involving new properties but holding the precursor helical macromolecular structure, new cationic functionalization is held by introducing amide groups *para*-substituting the two ester groups in the central

The final formulations of the new monomers, called PNOBDME and PNOBEE, are shown in **Figure 7(a)** and **(b)**, respectively. The hydrogen and carbon atoms have been numbered as precursors PTOBDME [16, 17] and PTOBEE [11, 15], respectively. The synthetic way is based on our previous experience for the attainment of cholesteric LC polyesters and the condensation reaction reported by Sek et al. to obtain polyesteramides [32]. The intermediate acid chloride yield obtained here is lower than the precursor polyesters obtained. The synthetic way of polyesteramides PNOBDME [C34H38N2O6]n and PNOBEE (C26H22N2O6)n is given in **Figures 8** and **9**.

provides an escape mechanism for the polycation/DNA complexes [30].

benzene ring of the terephthalate unit, along the main chain [31].

*DOI: http://dx.doi.org/10.5772/intechopen.91317*

(C26H19O9N)n [29].

**Figure 8.**

*Scheme of the synthetic way to attain PNOBDME.*

*Liquid Crystals and Display Technology*

chains were choline [▬CH2▬CH2▬N+

CH2▬CH2▬N+

New polyplexes were formulated including cholesteric LC PTOBDME and/or PTOBEE and *new monomeric cationic surfactant molecules* synthesized in our lab to entrap an anionic DNA plasmid. The new polyplexes successfully transfected both in vitro and in vivo in mice, as non-viral vectors for gene therapy*.* Their structures

New cationic chemical formulations of multifunctional cholesteric LCs PTOBDME and PTOBEE were designed later to directly interact with negatively charged DNA. The functional groups selected to be introduced at the end of the main polyester

groups (▬CONH2) chemically bonded to the end of the lateral hydrophobic chains.

H▬(CH3)2]. Two more new polymers were also formulated with amide

▬(CH3)3] and ammonium, defined as [▬CH2▬

were studied by synchrotron radiation source [22, 27, 28].

**84**

**Figure 8.**

*Scheme of the synthetic way to attain PNOBDME.*

The new cationic cholesteric LC polymers so designed were synthesized as follows: PTOBDME-choline [(C34H36O8)n▬C5H13N]; PTOBEE-choline [(C26H20O8)n ▬C5H13N]; PTOBDME-ammonium [(C34H36O8)n▬C5H13N]; PTOBEE-ammonium [(C26H20O8)n▬C5H13N]; PTOBUME-amide [(C33H33O9N)n]; and PTOBEE-amide (C26H19O9N)n [29].

These cationic polymers proved to be biocompatible, able to form polyplexes and capable of successfully condensing and transfecting the DNA into the nucleus cell, protecting DNA from inactivation by blood components. The complexes are sensitive to pH changes, possessing substantial buffering capacity below physiological pH. Their efficiency relies on extensive endosome swelling and rupture that provides an escape mechanism for the polycation/DNA complexes [30].

Since we are mainly interested in the design and chemical modifications of multifunctional cholesteric LC polyesters involving new properties but holding the precursor helical macromolecular structure, new cationic functionalization is held by introducing amide groups *para*-substituting the two ester groups in the central benzene ring of the terephthalate unit, along the main chain [31].

The final formulations of the new monomers, called PNOBDME and PNOBEE, are shown in **Figure 7(a)** and **(b)**, respectively. The hydrogen and carbon atoms have been numbered as precursors PTOBDME [16, 17] and PTOBEE [11, 15], respectively.

The synthetic way is based on our previous experience for the attainment of cholesteric LC polyesters and the condensation reaction reported by Sek et al. to obtain polyesteramides [32]. The intermediate acid chloride yield obtained here is lower than the precursor polyesters obtained. The synthetic way of polyesteramides PNOBDME [C34H38N2O6]n and PNOBEE (C26H22N2O6)n is given in **Figures 8** and **9**.

**Figure 9.** *Scheme of the synthesis of PNOBEE.*

The structure of the polymers so obtained could be confirmed by 1 H, 13C, COSY and HSQC NMR [31]. The NMR shifts were assigned according to our previous notation. Their thermal stability is studied by thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis.
