Purification of PCR products is generally not necessary. You can use unpurified PCR products directly, as long as the total volume of PCR products in the Gibson Assembly reaction is 20% or less. If greater amounts of PCR products are used, a column cleanup kit is sufficient. It is advantageous to gel-purify the target DNA fragment if the PCR product is contaminated by either non-specific amplification products, primer-dimers or large quantities of unused PCR primers.
