# Origin and Composition of Exosomes as Crucial Factors in Designing Drug Delivery Systems
## 8 Loading Drugs to Exosomes
Exosomes were also used as a device for gene editing tools delivery such as Cas9 [132]. Exosomes are either collected from the disease culture medium (bacterial vaccines) or modified with genetic engineering methods. The mode of action of these vaccines is mainly by the presentation of immunogenic surface particles. There are some reports on completed and running clinical trials including exosome-mediated drug delivery with promising outcomes [120, 133]. _Route of Administration_  
According to current studies, exosomes are mostly administrated intravenously and locate preferably in the liver. Only a few studies used another administration method, namely nasal, oral, and intraperitoneal. In these cases, exosomes are preferably located in  
Figure 3: Methods of loading drugs into exosomes. (**I**)—drug loaded exosomes released from drug exposed cells, (**II**)—drug incubation with exosomes with additional stirring, (**III**)—sonication, (**IV**)—electroporation, (**V**)—extrusion, (**VI**)—freeze-thaw cycles, (**VII**)—chemical conjugation of drug to exosome. the lungs and brain, stomach, and liver, respectively. There is a clear connection between the administration route and exosomes accumulation [88; 134; 135]. This is also confirmed in currently completed clinical studies, as reported at clinicaltrails.gov (accessed on 15 November 2022). For instance, few studies described the use of exosomal inhalations in the treatment of pulmonary diseases such as SARS-CoV-2-related ones [136]. These studies reported a very good tolerance of exosomes. Other clinically tested applications were: ointment, oral applications, intra-disc injection, and intravenous injection. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Drug/Macromolecule** & \
\begin{tabular}{c} **Loading** \\ **Efficiency and** \\ **Method** \\ \end{tabular} & **Origin** &
\begin{tabular}{c} **Targeted** \\ **Cells/Tissue** \\ \end{tabular} & **Effect** & **Ref.** \\ \hline \multirow{6}{*}{CRISPR/Cas9 plasmid} & chemical & & & & \\  & transfection of & & & & \\  & exosomes from & & & & \\  & MSC & & & & \\  & (Exo-FectTM & & & & \\  & Exosome & & & & \\  & Transfection & & & & \\  & Kit); & MSC; & & & & \\  & chemical & HEK293T cell & KPC689 & & & \\  & transfection & line & cell line & & \\  & (Lipofectamine & & & & tumor growth \\  & 2000) of cells & & & & \\  & (HEK293T) and & & & & \\  & isolation of & & & & \\  & exosomes from & & & & \\  & conditioned & & & & \\  & medium & & & & \\ \hline \multirow{6}{*}{siRNA targeting KRAS in PEI matrix;} & \textgreater{}90\%; & & & & \\  & incubation & & & & \\  & with PEI & & & & \\  & matrix; & & & & \\  & \(<\)5\%; electropo- & Bovine & Panc-1, MiaPaCa-2 & & \\  & ration; & & coll lines; in vivo & & \\  & 35\% chemical & & A549 xenograft & & \\  & transfection & & models & & \\  & with Exo-FectTM & & & & \\  & (about 35\%) & & & & \\ \hline \multirow{6}{*}{Doxorubicin; cholesterol-modified miRNA159} & \textgreater{}160.6 & & & & \\  & ng/\(\mu\)g & & & & \\  & exosomes; & & & & \\  & incubation in & & & & \\  & triethylamine & & & & \\  & solution;1.2\% & THP-1 cell line & MDA-MB-231 cell & synergistic therapeutic effects & \\  & of miRNA, & & & & on cancer cells, inhibition of \\  & & 5.3\% of & & & \\  & cholesterol- & & & & \\  & modified & & & & \\  & miRNA & & & & \\ \hline \multirow{6}{*}{5-fluorouracilacil; miR-21 inhibitor oligonucleotide} & \multirow{6}{*}{3.1\%; 0.5\%; electroporation} & \multirow{6}{*}{293T cell line} & HCT-116\({}^{\text{GFR}}\) cell & Successful co-delivery, & \\  & & & & & \\  & electroporation & & & & \\  & & & & \\  & & & & \\ \hline \multirow{6}{*}{miR-31-5p} & N/A; & & HUVEC cell line; & & Improved cells function in vitro, \\  & electroporation & & in vivo BALB/c & enhancement of angiogenesis, & \\  & & & & & \\  & & & & & \\  & & & & & \\  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._