# Targeted Lipid-Based Drug Delivery Systems for Lung Cancer Therapy
## 3 Drug Delivery Systems
### Nanostructured Lipid Carriers (NLCs)  
To overcome the disadvantages of SLNs (i.e., to form a rigid crystalline or a perfect ordered core), NLCs (Figure 1f) were introduced by [PERSON] et al. [83]. To create NLCs, liquid lipid was added to the preparation of the SLNs in addition to the already-used materials, i.e., solid lipid and surfactant. The lipid droplets were partially crystallised and had a less-ordered crystalline structure (or amorphous structure) [84]. Flexibility was increased and therefore higher drug loading was achieved when compared to SLNs [85]. For these reasons, a better stability for the encapsulated drug was accomplished [86]. On the contrary, the NLCs may become sensitiers and become irritants due to the surfactant presence; therefore, their concentration and selection during NLC preparation is significant for the cell type that the NLCs are intended to target [61]. The use of solid lipids in the preparation of NLCs previously led to larger-sized particles, but due to continuous increase in liquid lipid content the particle size decreased due to a decrease in viscosity and an increase in molecular mobility. Therefore, the amount of lipid content is important in NLC formulation [87]. Some model drugs like doxorubicin [37], sunitinib [88] and paclitaxel [89] have been incorporated in NLCs for lung cancer therapy (Table 1). NLCs can be delivered through the oral [90], pulmonary [87], intravenous [91] and percutaneous [92] routes.  
Regarding pharmacokinetics studies, intraperitoneal delivery of curcumin-loaded NLCs has displayed a significantly higher Cmax and AUC, showing that the NLCs have improved the relative bioavailability of curcumin when entrapped within the delivery system [93].  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Drug Delivery System** & **Drug** & **Particle Size (nm)** & **PDI** & **EE** & **Cytotoxicity** & **Ref.** \\  & & & & **(\%)** & & \\ \hline Microemulsions & Etoposide & 44.3 & - & 94.3 & The ICS0 of etoposide-loaded & [45] \\  & & & & microemulsion was 1.49 \(\mu\)g/mL against & 5.03 \(\mu\)g/mL of the plain etoposide on & \\  & Gemcitabine & - & - & - & The cytotoxicity study revealed a low & [43] \\  & & & & antiproliferative effect of plain drug & \\  & & & & against A549 lung cancer cells compared & \\  & & & & to drug-loaded water in & \\  & & & & & oil microemulsion. & \\  & & & & & The microemulsion improved the & [46] \\  & & & & & antitumour effect of the drug against & \\  & & & & & & A549 lung cancer cells. & \\ \hline Liposomes & Paclitaxel & 5350 & 3.32 & 95.45 & The paclitaxel-loaded liposomes exhibited & [33] \\  & & & & & lower cell viability of 58\(\mu\) against & \\  & & & & & MRCS-V2 transformed human lung & \\  & & & & & fibroblast cells. & \\  & & & & & The ICS0 of the siRNA/doctoral-loaded & [54] \\  & & & & & liposomes was lower compared to the free & \\  & & & & & docetaxel against A549 and H226 lung & \\  & & & & & cancer cells. & \\  & & & & & cancer cells. & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\ \end{tabular}
\begin{tabular}{c}  \\ \end{tabular}
\end{table}
Table 1: Representing lipid-based formulations used for lung cancer therapy, their size, polydispersity index (PDI), entrapment efficiency (EE) and cytotoxicity results.