**2. Polymeric gene delivery vector**

The important property in polymeric vector is that the polymer should be non-toxic (biocompatible), biodegradable (hence have less toxicity) and also help to release the DNA from the complex into the cytoplasm. In polymeric vector, the polymer must be condensate with the genetic material. Condensate between the cationic polymer and genetic materials can be done through electrostatic interactions. By modifying the surface of NP, NP-DNA complexes can be formed by electrostatic binding between the positive charges of the NPs and the negative charges of the DNA. Only when the medium is aqueous and hydrophilic, the polymeric vector will be mobile, because the vector needs hydrophobic and hydrophilic components and be stabilized in an aqueous solution by forming micelles [13].

## **2.1. Polymer properties in polymeric gene delivery**

Polymers have permanent cationic charges on its surface and are not preferred due to its strong condensate property with DNA, which will not release DNA into the cell. Hence, ionizable cationic polymers with pK values between 5 and 7 are preferred in the polymeric vector delivery which is shown in **Figure 1**.

Other important factors to be considered for the polymer in the polymeric gene-delivery vector are its molecular weight, molecular structure and composition of the polymer. Increase in the polymer's molecular weight also increases its toxicity. Polymers of different molecular structures such as linear, branched, stars and dendrimers have an impact on the transfer genes into cells [14–18].

## **2.2. Preparation of polymeric gene vector**

Polymeric vectors are prepared by mixing plasmid DNA with a cationic polymer. During condensation between plasmid DNA and polycation, plasmid DNA undergoes a conformational change from a hydrodynamic size of 200–300 nm to particles of less than 100 nm. Plasmid DNA has a highly organized chemical structure [19–22]. A condensation between plasmid DNA and polycation is shown in **Figure 2**.

**Figure 1.** Gene delivery process of polymeric nanoparticle.

have well-defined structure and fine-tunable degradation kinetic and mechanical properties compared to the natural polymers. Recently, biodegradable nanoparticles have a major role in the field of health sciences especially for treating various diseases through drugs, vaccines and genes [1–7]. Nanoparticle in gene-delivery system has been utilized for treating various diseases such as cancer and haemophilia. The major challenge in the gene delivery is delivering the genetic materials such as DNA, plasmids, RNA and siRNA into the target/special cells to replace the damaged genes or expression inhibition of undesired genes or expression and production of required proteins. In gene delivery, the genetic material is either encapsulated inside the nanoparticle or conjugated to the nanoparticle. The nature, source and their physico-chemical properties of the polymers play an important role in the formation of

desired properties of nanoparticles and to achieve a better therapeutic effect [8–12].

The important property in polymeric vector is that the polymer should be non-toxic (biocompatible), biodegradable (hence have less toxicity) and also help to release the DNA from the complex into the cytoplasm. In polymeric vector, the polymer must be condensate with the genetic material. Condensate between the cationic polymer and genetic materials can be done through electrostatic interactions. By modifying the surface of NP, NP-DNA complexes can be formed by electrostatic binding between the positive charges of the NPs and the negative charges of the DNA. Only when the medium is aqueous and hydrophilic, the polymeric vector will be mobile, because the vector needs hydrophobic and hydrophilic components and be

Polymers have permanent cationic charges on its surface and are not preferred due to its strong condensate property with DNA, which will not release DNA into the cell. Hence, ionizable cationic polymers with pK values between 5 and 7 are preferred in the polymeric vector

Other important factors to be considered for the polymer in the polymeric gene-delivery vector are its molecular weight, molecular structure and composition of the polymer. Increase in the polymer's molecular weight also increases its toxicity. Polymers of different molecular structures such as linear, branched, stars and dendrimers have an impact on the transfer

Polymeric vectors are prepared by mixing plasmid DNA with a cationic polymer. During condensation between plasmid DNA and polycation, plasmid DNA undergoes a conformational change from a hydrodynamic size of 200–300 nm to particles of less than 100 nm. Plasmid DNA has a highly organized chemical structure [19–22]. A condensation between

**2. Polymeric gene delivery vector**

138 Advanced Technology for Delivering Therapeutics

stabilized in an aqueous solution by forming micelles [13].

**2.1. Polymer properties in polymeric gene delivery**

delivery which is shown in **Figure 1**.

**2.2. Preparation of polymeric gene vector**

plasmid DNA and polycation is shown in **Figure 2**.

genes into cells [14–18].

**Figure 2.** Condensation between plasmid DNA and polycation.

The order of mixing and vortex speed of mixing plays an important role in the size of the DNA nanoparticles. DNA can be condensate, either by evaporation under vacuum or by freeze drying. The freeze/thaw cycle can influence the particle size of DNA nanoparticles.

The charge ratio of DNA nanoparticles is the calculated ratio of amines on the polymer relative to the phosphates on DNA at a given stoichiometry of polymer to DNA. When a cationic polymer binds to plasmid DNA, sodium ions are displaced and the electronegative charge is partially satisfied. DNA condensates are normally prepared at near-neutral pH in low ionic strength buffer [23, 24].
