Most of commercial plasmid miniprep kits rely on the spin column with silica membrane. The plasmid DNAs purified can be used for routine molecular biology applications such as DNA subcloning, PCR, in vitro transcription, DNA sequencing, and DNA transfection into mammalian cells. Protocols of plasmid miniprep using spin columns:

– QIAprep Spin Miniprep Kit High-Yield Protocol
– PureYield Plasmid Miniprep System Protocols
– PureLink Quick Plasmid Miniprep Kit Protocol
– GenElute Plasmid Miniprep Kit Protocol

Many other companies including Syd Labs also manufacture silica membrane spin column-based plasmid miniprep kits. The principle behind and procedure are similar. To save more money, one can make a plasmid miniprep kit by buying spin columns for plasmid miniprep alone and making solutions with the buffer recipe for plasmid miniprep using spin columns.