# BMP-2 Delivery through Liposomes in Bone Regeneration
## 4 Transfection  
Gene therapy is used to transfer genetic material into specific cells to obtain the secretion of a certain protein. DNA, plasmids, siRNAs, miRNAs can be delivered into target cells using vectors which protect them and facilitate their transport through the cell wall [101; 102]. This method may be more effective than the exogenous utilization of the molecule, because it restricts the migration of the molecule and the accumulation in other organs. Transfection of DNA into cells is the ideal way to study some functions of proteins. The cells will become, by this method, protein producing factories at the site of the injury. Viruses represent a good vector, as they developed natural ways to enter the host cell and integrate in their genetic material. Adenoviruses, retroviruses, adeno-associated viruses, and lentiviruses are used as vectors the most efficiently [103; 104; 105], but they carry significant \begin{table}
\begin{tabular}{p{42.7 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Molecule** & **Liposome/Scafrolls** & **Cells** & **Entrapment Efficiency** & **Animal Intervention** & **Examination** & **Citation** \\ \hline \multirow{8}{*}{BMP-2} & HSPC & & Maleimide quantification assay & & & \\  & DSPC & & Confocal laser scanning microscopy & & & \\  & Chol & & FE-SEM (field emission SEM) & Male Wistar rats & & \\  & mPEG\({}_{200}\)-DSPE & Human adipose & Osteogenic differentiation & Subcutaneous pocket & Histology, hematoxylin-eosin & [95] \\  & Film hydration & GNCS & Cytocompatibility and proliferation & & for ectopic bone formation & & \\  & Electrophysiological PLLA & & ALP activity & & & \\  & Nanofibers with HA & & Gene expression analysis & & & \\  & covering & & RunX2, OC, GAPDH & & & \\  & & RT-PCR & & & & \\ \hline \multirow{4}{*}{rhBMP-2} & \multirow{2}{*}{Magnetic liposomes} & & Fluorescence spectrophotometry & 31 Male Sprague & Radiography once a week for 9 weeks & \\  & & & Dyramic light scattering & Dawley rats with critical size bone & Micropunctography & \\  & & & TEM & defect in the femur & Histology & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\ \hline \multirow{4}{*}{rhBMP-2} & Multilamellar & & & 30 New Zealand & & BMF-2 by ELISA & \\  & Included in gel & & & rabbits & Histology, HE light & \\  & & & & Maximally critical & \\  & & & & & & \\  & & & & & & \\  & & & & & \\ \hline \multirow{4}{*}{rhBMP-2} & \multirow{4}{*}{PEG} & \multirow{4}{*}{Human CAC12} & \multirow{4}{*}{MTT cytotoxicity} & \multirow{4}{*}{Female Sprague} & \multirow{4}{*}{[100]} \\  & BP & & Rat BMSC & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Direct liposomal administration of BMP-2. side effects and limitations, such as inflammatory and immune reactions, limit of included DNA size, or certain tumorigenic mutations [15; 106; 107; 108]. Non-viral vectors are mostly cationic polymers or cationic liposomes, which interact with the negatively charged genetic material and can be transported into the cell. Liposomal transfection is not as efficient as the viral ones [109], but it yields a series of advantages such as lack of immune response, toxic byproducts, ectopic bone formation, and accumulation in organs [67]. Liposomes are a viable solution for transfection of large genetic structures, as their capacity to carry genetic material is not limited by size [110]. The genetic sequence is first loaded into the liposome. After the construct enters the cell, the gene is released, it enters the nucleus, where it integrates into the cell's DNA. Thus, the cell produces BMP-2 (Figure 2). There are very few studies in the literature in which direct loading of BMP-2 is used; however, more studies concentrate on transfection of BMP-2 genes into cells. [PERSON] et al.