Fig. 1.

Illustration of the procedure of selecting cancer cell-targeting peptide from a major coat displayed phage library. (a) A phage library where each phage clone displays a unique peptide sequence on the major coat. (b) Some phages bind or internalize into target cells while some do not after the phage library is added. (c) Unbound phages are washed away, and cell-targeting phages are still in the flask. (d) Cell-surface-bound phage is recovered by elution buffer which breaks up the cell and phage binding, then cell-internalized phage is recovered by lysing the cells. (E) The eluted/lysed phages are amplified by infecting E. coli and then purified by PEG/NaCl. (f) After 3–5 rounds of selection, the eluate and lysate are separately titered to form individual phage clones. (g) The insert-coding region of phage genome is amplified by PCR and sequenced. (h) Scheme of a single phage particle, which shows that 5 copies each of pIII and pVI are at one distal end and 5 copies each of pVII and pIX are at the other end of phage, whereas ~4,000 copies of pVIII form a protein coat wrapping single-strand DNA