## 1 Introduction  
A successful drug carrier system should have optimal drug loading and release properties, a long shelf life, and exert a much higher therapeutic efficacy as well as lower side effects. Drug delivery systems are also able to solve several drug problems, including overcoming multi-drug-resistance phenomenon, penetrating cellular barriers that may limit the intended target site, and improving in vivo efficacy of the hydrophilic and lipophilic drugs [1; 2; 3]. Therefore, nanotechnology could modulate both drug pharmacokinetics and biodistribution, decreasing potential side effects. In this context, liposomes are the versatile delivery systems formed by the colloidal association of amphiphilic lipid substances which are suitable for delivering both hydrophilic and hydrophobic drugs. Recently, an eco-friendly technology with supercritical fluids for the preparation of nanostructured liposomes was reported as a green alternative in the scale-up because conventional processes require large amounts of organic solvents [4]. Liposome-based formulations also represent a good success for dye delivery, as reported for example in the case of indocyanine green, an FDA-approved fluorescent dye, utilized in various biomedical applications such as drug delivery, imaging, and diagnosis [5]. Liposomes are also advantageous for encapsulating inorganic structures [6; 7]. Recently, the use of herbal medicines has increased due to their therapeutic effects and fewer adverse effects as compared to modern medicines. However, many herbal extracts show poor in-vivo activity due to their low solubility, resulting in poor absorption and hence poor bioavailability. Furthermore, there is a great possibility that many compounds of the extract will be destroyed partially or entirely after oral administration. Other components might be metabolized by the liver before reaching the blood circulation. Novel drug delivery systems represent a valid tool for enhancing bioavailability of herbal drugs. The novel formulations are reported to have remarkable advantages over conventional formulations of plant actives and extracts which include increase of solubility, bioavailability, protection from toxicity, enhancement of pharmacological activity and intracellular uptake, modification of pharmacokinetics and bio-distribution, improved tissue macrophages distribution, sustained delivery and protection from physical and chemical degradation. Furthermore, plant extracts present critical issues due to the wide variety of the compounds contained therein. There are numerous examples of application of the drug delivery systems in this field related to isolated products or herbal extracts [8; 9; 10; 11; 12; 13]. In particular, oral absorption of lipophilic extract can be significantly improved using lipid-based non-particulate drug delivery systems, which avoid the dissolution step. Lipid-based nanocarriers, such as micro- and nanoemulsions, solid-lipid nanoparticles, and nanostructured lipid carriers, represent successful examples of nanoformulations applied to overcome the limitations of natural compounds [14; 15; 16]. They can ameliorate solubility, stability, permeation and bioavailability. Lipid-based drug delivery systems are composed by lipids that are also absorption enhancers [17; 18] and can be developed in small particle sizes ranging from micro- to nanometers [19; 20] to increase the absorption in the hydrophilic environment of the gastrointestinal tract. Among lipid-based delivery systems, nanostructured lipid carriers (NLCs) offer many advantages, such as long-term stability, increased bioavailability of encapsulated active ingredient, possibility to obtain a controlled or targeted release, versatility in encapsulating both lipophilic and hydrophilic drugs, and high efficiency of encapsulation [21].