A novel approach for increasing transformation efficiency in E. coli DH5α cells using silver nanoparticles.

The present study is the first report on the application of silver nanoparticles for efficient bacterial transformation. EC50 value of 100 nm silver nanoparticles against E. coli DH5α cells was recorded as 4.49 mg L-1 in toxicity assay. Competency induction in E. coli DH5α cells by treatment with 100 nm silver nanoparticles at a concentration of 1 mg L-1 for 60 min and transformation using three plasmid vectors of different sizes, viz. pUC18, pBR322 and pCAMBIA resulted in tenfold increase in the bacterial transformation efficiency, i.e. 8.3 × 104, 8.0 × 104 and 7.9 × 104 cfu ng-1 of DNA, respectively, even without heat shock compared to the conventional chemical method using 0.1 M calcium chloride (2.3 × 103 cfu ng-1 of DNA).