**7. Conclusion**

**Figure 2.** Various shapes of gold nanoparticle.

20 Advanced Technology for Delivering Therapeutics

(610 nm), and Maple Red-Orange (620nm).

Quantum dots are tiny semiconductor crystals of luminescent nanocrystals with rich surface chemistry and unique optical properties with the size of 1–10 nm made up of compounds from group II to VI and III to V, for example, Ag, Cd, Hg, Ln, P, Pb, Se, Te, Zn, and so on. QDs have distinctive characteristics such as size-tunable light emission, improved signal brightness, resistance against photobleaching, and simultaneous excitation of multiple fluorescence

Depending on their size by laser, the quantum dots glow brightly in different colors, such as Adirondack Green (520nm), Blue (514 nm), Greenish blue (544 nm), Green (559 nm), Yellowish green (571 nm), Yellow (577 nm), Yellowish orange (581 nm), Fort Orange (600nm), Orange

QDs are nearly spherical semiconductor particles with core-shell structure. Colloidal core/shell QDs, such as CdSe/ZnS, CdSe/CdS/ZnS, CdTe/CdSe, and InP/ZnS, are commonly synthesized for biomedical applications, whereas CdSe/ZnS, CdTe/ZnS, and CdSe/CdS/ZnS have been

**Core** is made up of CdSe, which is a semiconductor material. Core is surrounded by shell which is made up of ZnS for improving its optical properties and cap encapsulates the double layer quantum dots by different materials like silica which helps in improving solubility in

Quantum dots are made up of three parts, that is, core, shell, and cap.

aqueous buffers. Structure of quantum dot is shown in **Figure 3**.

**6.3. Quantum dots**

colors.

commonly used.

Recently nanotechnology-based gene delivery is one of the most attractive therapeutic methods for treatment of various diseases. In drug delivery, size and distribution of particles are critical parameters to target specific organs and tissues. Proteins (derived from their secondary structure) are suitable materials for drug/gene carriers due to their precise molecular sizes. An ideal nanoparticle formulation for a drug or gene carrier system can achieve long circulation time, low immunogenicity, good biocompatibility, and selective targeting.

Gene delivery involves viral and non-viral vectors. Viral vectors are having low loading capacity, large-scale manufacturing, quality control cost, and safety factor such as immunogenicity and potential oncogenicity. From the stability and safety concern, non-viral vectors have more efficiently passing the gene transfection through the biological barriers compared to viral vectors. Organic, inorganic, and various hybrid materials are used for the preparation of nanoparticles. Among these, polymeric nanoparticles have great therapeutic application due to its wide range of sizes and varieties and can be used in sustained and targeted gene delivery for long periods. Biopolymers used for the preparation of nonviral vectors possess several favorable characteristics, such as high biocompatibility, low toxicity, good biodegradability, and abundant renewable sources, which can be used for efficiency delivery of drug/ gene to the target site.

Choosing a suitable design of nanoparticle structure can increase gene transfection efficiency to overcome extracellular and intracellular transfection barriers: the blood stream, the cellular membrane, endosomes, and the nuclear membrane. Nanoparticle in gene delivery depends upon the nature of the polymer charge and its chain length. Furthermore, modifications in the nanoparticle by introducing ligands onto the surface can enhance localization and retention in specific target tissue, local delivery of agents to a large volume of tissues for better clinical application. However, biopolymer-based nanoparticle will become a tool in near future for the precisely targeted delivery of drugs and genes in many therapeutic fields, but toxicological issues and degradation products of nanoparticles are need to be considered before being applied into humans.
