Abstract
The discovery of peptide and protein therapeutics such as insulin and adrenocorticotrophic hormone in the twentieth century was a breakthrough in drug discovery. However, peptide and protein therapeutics due to their characteristics are predisposed to denaturation and degradation and their delivery and formulation have been a persistent challenge for the biotech and pharmaceutical industry. Their bioavailability is very low mainly due to low gastrointestinal solubility and permeability resulting from low membrane penetration, high molecular weight, proteolytic chemical and enzymatic degradation which altogether urge a compatible drug delivery system. Numerous drug delivery systems with modifiable properties have been synthesized. Solid Lipid Nanoparticles (SLNs) protect the encapsulated peptide and protein therapeutics against first-pass effect and proteolytic degradation, thus enhance drug stability, dissolution rate, absorption and bioavailability. The physicochemical properties of SLNs such as small size, high surface area and surface modification improve their mucosal adhesion, tissue-targeted distribution, controlled drug release and half-life. Besides, SLNs can be encapsulated by both hydrophilic and lipophilic drugs which also offer simplicity of preparation, large-scale manufacturing, biodegradability, biocompatibility, low toxicity, low adverse effects and various drug release profile.