Fig. 4

a Schematic representation of the conjugation of PEGylated biotin on the surface of the PLGA nanofiber arrays for ToF–SIMS chemical imaging. b–g ToF–SIMS chemical images of PEGylated biotin-conjugated PLGA nanofibers in b–d positive ion mode for b C₁₀H₁₅O₂N₂S⁺, c PLGA, and d total ions and e–g negative ion mode for e CN⁻, f PLGA, and g total ions