Nanoparticles. Today, a vast number of investigations have been focused on nanoparticles and their role as drug delivery vehicles. Nanoparticles were first introduced in the mid seventies by Xxxxxxxxxx and Xxxxxxx [79]. The preparation of nanoparticles was simple, the particles formed were relatively stable and easily freeze-dried; hence, biodegradable polymers were found useful and further developed for drug delivery. Polymeric nanoparticles have the advantages of protecting the protein and peptide drugs from chemical and enzymatic degradation in the GIT, increasing their stability and absorption across the intestinal epithelium as well as controlling the drug release [80-83]. A number of techniques such as polymerization, nanoprecipitation, inverse microemulsion can be used to prepare polymeric nanoparticles; however, most of these methods involve the use of organic solvents, heat and vigorous agitation which may be harmful to the peptide and protein drugs [84, 85]. More recently the ionic gelation technique is used as the most favorable method for producing peptide and protein nanoparticles. The nanoparticles prepared by this method have a suitable size and surface charge, spherical morphology as well as a low polydispersity index indicative of a homogenous size distribution. The lack of using organic solvents, sonication or harsh conditions during preparation reduces the damage to the peptide and proteins and makes this method a favorable one for the preparation of protein loaded nanoparticles [86, 87]. Chitosan nanoparticles with excellent biodegradable and biocompatible characteristics have been used extensively as drug delivery vehicles [88]. However, due to poor solubility of chitosan at pH above 6.0, its quaternized derivatives such as trimethyl chitosan, triethyl chitosan, diethylmethyl chitosan and dimethylethyl chitosan, which are soluble at the intestinal pH, have been used to prepare nanoparticles loaded with insulin [24, 28, 29, 32]. Chitosan nanoparticles loaded with insulin were prepared by mixing the positively charged polymer with the negatively charged insulin and nanoparticle formation occurred via electrostatic interaction. Studies have shown that insulin in nanoparticulate form was more likely to be delivered across the GI tract than in its free soluble form [33, 34, 89]. The particle size and surface charge are critical factors in nanoparticle absorption. Size is a determining factor for both uptake and biological fate of the particulate systems. ...
Nanoparticles. Nanoparticles for medical applications are defined as solid colloidal particles of 1 to 1000 nm in diameter (Xxxxxx and Xxxxxx, 2011). In the area of drug delivery nanoparticles are generally 50 nm or larger in size (De Jong and Borm, 2008). The active therapeutic agent is either dissolved, entrapped or encapsulated within the nanocarrier, or alternatively absorbed or attached to the surface of the matrix (Sahoo and Xxxxxxxxxxx, 2003). Depending on their structures and morphologies, nanoparticles can be further classified as matrix (nanosphere) or vesicular structures (nanocapsule). Nanospheres are matrix systems in which the therapeutic agent is physically and uniformly dispersed, whereas nanocapsules are vesicular systems in which drug is usually contained within a cavity surrounded by a solid or liquid core that is encapsulated by an outer shell. The advantages of using nanoparticles for drug delivery result from their small size that can penetrate through mucus and from their degradation if made from biodegradable materials which can allow sustained drug release within the target site over a period of time (Xxxxxx and Xxxxxxxx, 2003). A wide range of materials have been used to fabricate nanoparticles for various applications with different properties and release characteristics for the encapsulated therapeutic agent (Xxxxx et al., 2008). The materials employed to fabricate nanocarriers for drug delivery can broadly be categorised as inorganic (elements such as silica and alumina) or polymeric (naturally occurring such as gelatin and albumin, or synthetic such as poly(cyanoacrylate)) (Xxxxxxx et al., 2012). When considering their use in inhaled formulations it is imperative that the materials used do not elicit an acute inflammatory response or accumulate following chronic dosing (Xxxxxx et al., 2006). Although inorganic nanoparticles possess good stability and demonstrated successes in imaging and treatment of tumors (Xxxxx et al., 2006), they are not well biodegraded and hence raise concerns over their biopersistence and long term toxicity (Xxxxx et al., 2011). Biodegradable polymers are thought to be more attractive when considering repeat human exposure. Polymers can undergo hydrolysis upon implantation into the body, forming biologically compatible and metabolizable moieties that are eventually removed from the body. There are various potential applications of nanoparticles for delivery of therapeutic agents to the cells and tissue (Xxxxxx and Xxx...
