**1. Introduction**

In the recent decades, pharmaceutical nanotechnology has opened a new era for the research in the design and characterization of drug delivery systems (DDS) and biotechnological products. A variety of novel drug delivery systems and strategies emerged for diagnostic and therapeutic applications that explored the different structural components, fabrication methods and mechanisms of drug delivery and targeting [1]. These DDS emphasized on

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the use of multiple nanomaterials and therapeutic moieties that renovate the current pharmaceutical industry and biomedical sciences toward the better drug therapy [2]. These nanosized particles were utilized for the delivery of various molecules including different drugs, proteins, nucleic acid and other diagnostic agents. Some of these compounds may be encapsulated inside while others were adsorbed on the surface of these nanoparticles. These nanocarriers can amend the pharmacokinetics and pharmacodynamics of drug by enhancing the solubility, permeability and bioavailability in multiple ways. The availability of the encapsulated compound depends upon the nature of formulation components and the other external stimuli which enable the controlled as well as targeted delivery of these encapsulated compounds within the cellular microenvironment [3]. All these parameters ultimately achieve the higher concentration of the encapsulated drug that efficiently reaches the potential target site without affecting the normal tissues. These nanocarriers also aid to implement the concept of rational therapeutics by providing the tunable drug delivery systems based on the patient therapeutic demands.

Despite of excellent in-vitro performance, some drugs demonstrate poor in-vivo results because of low aqueous solubility, poor membrane penetrability, rapid clearance by the reticuloendothelial system, complex pathophysiological states of the disease and uncertain plasma levels leading to drug toxicity, thus, requiring such drug delivery systems that overcome these problems [4]. Latest developments in the material sciences, polymer engineering and nanotechnology have enabled multidisciplinary research to formulate and evaluate different novel drug delivery systems that claimed increased drug solubility, penetration and retention at the targeted site in the body [5].

Among the different nanoparticulate systems, nanoparticles of different composition and lipid based vesicular carriers (liposome, lipid nanocarriers, solid lipid nanoparticles and drug lipid conjugates) have been frequently employed for the medical applications. The nanoparticles may provide versatility in terms of composition. As, these include the polymeric nanocarriers, mesoporous nanoparticles, metal coated (gold, iron and silver), inorganic nanoparticles, quantum dots, carbon nanotubes, dendrimers and magnetic nanoparticles [6, 7]. Furthermore, all these systems were modified to mimic the desired therapeutic properties through different modification method and ligands such as (i) increase in the retention time and stability of the system, (ii) stimuli triggered release, (iii) targeted delivery of various agents and (iv) administration of dual modalities simultaneously [8, 9].

Liposomes and niosomes have been considered as most promising domains among the lipid vesicular carriers. Liposomes are defined as the lipid vesicles having the single or multiple layers of the lipid providing the encapsulation of different therapeutic moieties while niosomes have the same morphology but contain nonionic surfactants instead of phospholipids as major structural components. They provide the better biocompatibility profile, easy surface modification of the vesicles, versatility in the loading of hydrophobic and hydrophilic drugs and improved pharmacokinetic properties [10, 11]. However, drug leakage or fast release from the system, reproducibility, poor physical and chemical stability on storage, higher cost and scale up issues are the major drawbacks associated with the vesicular systems [12, 13].

Nanoparticles (polymeric, organic/inorganic, mesoporous silica, calcium carbonate and different metals, i.e., iron, silver and gold) established the second domain of the nanocarriers. These systems prove superiority in terms of smaller particle size, structural integrity, versatility in the polymeric materials, improved drug loading and release profile. They also provide the targeting capabilities in the case of magnetic iron oxide nanoparticles and better cellular interactions in case of organic and inorganic nanoparticles [14]. Similar to that of vesicular systems, these polymeric nanoparticles have some limitations in term of polymer toxicity, presence of toxic organic solvents, poor entrapment of hydrophilic drugs, polymer degradation and drug leakage before reaching the site of action [15].

the use of multiple nanomaterials and therapeutic moieties that renovate the current pharmaceutical industry and biomedical sciences toward the better drug therapy [2]. These nanosized particles were utilized for the delivery of various molecules including different drugs, proteins, nucleic acid and other diagnostic agents. Some of these compounds may be encapsulated inside while others were adsorbed on the surface of these nanoparticles. These nanocarriers can amend the pharmacokinetics and pharmacodynamics of drug by enhancing the solubility, permeability and bioavailability in multiple ways. The availability of the encapsulated compound depends upon the nature of formulation components and the other external stimuli which enable the controlled as well as targeted delivery of these encapsulated compounds within the cellular microenvironment [3]. All these parameters ultimately achieve the higher concentration of the encapsulated drug that efficiently reaches the potential target site without affecting the normal tissues. These nanocarriers also aid to implement the concept of rational therapeutics by providing the tunable drug delivery

Despite of excellent in-vitro performance, some drugs demonstrate poor in-vivo results because of low aqueous solubility, poor membrane penetrability, rapid clearance by the reticuloendothelial system, complex pathophysiological states of the disease and uncertain plasma levels leading to drug toxicity, thus, requiring such drug delivery systems that overcome these problems [4]. Latest developments in the material sciences, polymer engineering and nanotechnology have enabled multidisciplinary research to formulate and evaluate different novel drug delivery systems that claimed increased drug solubility, penetration and

Among the different nanoparticulate systems, nanoparticles of different composition and lipid based vesicular carriers (liposome, lipid nanocarriers, solid lipid nanoparticles and drug lipid conjugates) have been frequently employed for the medical applications. The nanoparticles may provide versatility in terms of composition. As, these include the polymeric nanocarriers, mesoporous nanoparticles, metal coated (gold, iron and silver), inorganic nanoparticles, quantum dots, carbon nanotubes, dendrimers and magnetic nanoparticles [6, 7]. Furthermore, all these systems were modified to mimic the desired therapeutic properties through different modification method and ligands such as (i) increase in the retention time and stability of the system, (ii) stimuli triggered release, (iii) targeted delivery of various agents and (iv) adminis-

Liposomes and niosomes have been considered as most promising domains among the lipid vesicular carriers. Liposomes are defined as the lipid vesicles having the single or multiple layers of the lipid providing the encapsulation of different therapeutic moieties while niosomes have the same morphology but contain nonionic surfactants instead of phospholipids as major structural components. They provide the better biocompatibility profile, easy surface modification of the vesicles, versatility in the loading of hydrophobic and hydrophilic drugs and improved pharmacokinetic properties [10, 11]. However, drug leakage or fast release from the system, reproducibility, poor physical and chemical stability on storage, higher cost and scale up issues are the major drawbacks associated with the vesicular systems [12, 13].

systems based on the patient therapeutic demands.

54 Advanced Technology for Delivering Therapeutics

retention at the targeted site in the body [5].

tration of dual modalities simultaneously [8, 9].

The problems associated with the liposomes, polymeric nanoparticles and other carrier systems can be reduced by using a novel combinatorial approach of "hybrid nanoparticles" (HNPs) that utilizes the positive attributes of two different components. These hybrid nanoparticles (HNPs) exploit the benefits of both systems (lipid and polymer/organic and inorganic materials) and the release profile of drug is based on the erosion and degradation of the core material by hydrolysis with in turn determined by water permeation into the outer shell layer and composition of the polymer. The core materials may be protected by the application of multiple layers of the shell materials and the interface of these layer acts as a site for the functionalization of the carrier system for the dual modalities of treatment and diagnosis [16].

Similarly, core shell hybrid nanoparticles using different oils, metal oxides, organic and inorganic components also provide newer system that has multilayered structure having the inner core outer shell with a suitable lipid or oil at the interface to develop a core shell hybrid structure. Recently, use of green approach offer more facile and potentially successful system with the added advantage of solvent-free nanohybrids with greater efficiency.

Such novel system consists of three different structural components as follows:


**Figure 1.** Structure of lipid-polymer hybrid nanoparticles; (a) polymer core-lipid shell hybrid, (b) 3 layers polymer-lipid hybrid nanoparticles consisting of polymeric core (1) and two lipid layers (2,3) shell, (c) 4 layers hollow core lipidpolymer hybrid, consisting of hollow core (1) covered by reverse surfactant layer (2), polymeric shell (3), and outer shells of two lipids (4). (d) organic core-inorganic shell and inorganic core-organic shell hybrid, (e) inorganic (metallic)-protein hybrid nanoflowers, and (f) graphene oxide coated mesoporous silica-inorganic hybrid nanoparticles.

In this chapter, the different types of hybrid nanocarriers have been described with particular emphasis on the brief rationale for the development of these hybrid nanocarriers along with different fabrication approaches with greater emphasize on the lipid polymer hybrid nanoparticles. A brief description factors governing the optimized response characteristics and their potential application of these hybrid nanoparticles are also presented.
