Raman module

Raman spectroscopy was conducted in the solid state using a Nicolet iS 50 FTIR with a Raman module (Thermo Fisher Scientific, Waltham, MA). The samples were prepared on a 48 well metal plate with duplicate wells containing either single components (PEG, PAL, or PEI), physical mixtures of components (PEG/PEI, PEG/PAL, PEI/PAL), or complete PNAs (2P or 3P). Duplicate wells allow for one well to contain components or PNAs alone or with siRNA. For analysis of single components, 100 μL of a 10 mg/mL solution of each component and an additional 100 μL of water was added to the well. For physical mixtures of components, 100 μL of a 10 mg/ml solution of each component was added to the well combination with an additional 100 μL of another component. Then, 1 μL of a 1 mg/mL siRNA solution or 1 μL of water was added to respective wells of components or PNAs. The loaded metal plate was stored at room temperature for 30 minutes to allow samples to interact with siRNA. The plate was then transferred to dry ice and the samples were frozen. The frozen samples were then freeze dried overnight and then read on the Raman. Data was collected and deconvoluted using the Omnic Spectra Software suite (Thermo Fisher Scientific, Waltham, Mass.).