In-Situ Visualization of the Enzymatic Growth of Surface-Immobilized DNA Block Copolymer Micelles by Scanning Force Microscopy

Abstract

The enzymatic growth of diblock copolymer micelles consisting of single-stranded DNA and poly(propylene oxide) (PPO) segments was studied with scanning force microscopy (SFM). DNA-b-PPO aggregates adsorbed randomly on a mica surface exhibiting a height of 4–5 nm. The size of the micelles was increased by terminal deoxynucleotidyl transferase (TdT), which catalyzes the repetitive addition of deoxyribonucleotides to the 3′-hydroxyl end of DNA. The onset of the micelle growth was controlled by the addition of 2′-deoxythymidine 5′-triphosphate (dTTP) mononucleotide to the reaction solution or by increasing the temperature to 37 °C. We determined the mean heights of the micelles from statistical analysis of SFM pictures recorded at different reaction times in-situ. The arrangements, heights, and lateral sizes of individual micelles were also followed. After 60 min a plateau in micelle height was observed (6–8 nm). In contrast, micelles that were grown in solution, i.e., in the absence of a mica surface, showed...