| The efficient delivery of therapeutic genes into target cells or tissues is a critical goal in gene therapy. Polyethylenimine (PEI) has been widely proven to effectively transfer genes both in vitro and in vivo for various diseases. Studies have reported that PEI's efficiency as a gene delivery vehicle depends on its molecular weight and structure. However, commercial PEI has not been thoroughly characterized. Therefore the goal of this research is to develop methods to analyze commercial PEI, both linear and branched, through the use of electrospray ionization mass spectrometry (ESI-MS), size exclusion chromatography (SEC), and a combination of these two techniques.; The method development involved the measurement of molecular weight distribution (MWD), the analysis of ion attachment, the determination of end groups, and the assessment of the degree of branching.; The preliminary analysis of molecular weight distribution by ESI-MS showed that the MWD of each sample was found to be very similar. PEI analyzed by electrospray shows preferential ion attachments to most molecules. An ESI study with mono and divalent cations suggests the lithium cations appear to be the optimum candidate for cationization of ESI technique.; The universal calibration concept was applied to analysis of molecular weight distribution by SEC. The result demonstrated the polymer structure played a dominant role in this study.; Coupling ESI-MS with SEC technique enables the separation and characterization of complex polymer community. This study demonstrated the existence of two types of PEI molecules (non-cyclic and cyclic molecules). The end groups for these two types of PEI oligomers were obtained, respectively.; To assess branching, imine derivatives of the PEI were prepared by reacting 7.5 equivalents of benzaldehyde and 4-fluorobenzaldehyde with PEI, respectively. ESI-MS spectra of the imine derivatives were compared and discussed.; Analysis of PEI by ESI, SEC, and the combination of both techniques can provide valuable data, but the data is limited. For analysis of large PEI molecules, such as PEI-1800 or higher, the MALDI-TOF-MS technique may be needed to overcome the detection limit of ESI-MS technique. |
