Physicochemical aspects of zwitterionic core-shell tecto dendrimers characterized by a thorough NMR investigation

ABSTRACT Core-shell tecto dendrimers (CSTDs) are a class of superstructured dendrimeric nanoconstructs with similar structural characteristics and biomedical performances to the high-generation dendrimers that can be decorated with zwitterions to be availed of good antifouling properties for different biomedical applications. Characterization of the CSTD-based dendrimeric derivatives remains to be a great challenge. Here, we attempted to utilize nuclear magnetic resonance (NMR) technologies to investigate the structure and hydrodynamic size of CSTDs functionalized with zwitterionic carboxybetaine acrylamide (CBAA) and confirmed their antifouling property through protein resistance assay. In this study, we initially prepared CSTDs by supramolecular assembly of beta-cyclodextrin (β-CD)-modified generation 5 (G5) poly(amidoamine) (PAMAM) dendrimers as cores and adamantane (Ad)-decorated G3 PAMAM dendrimers as shells, and then partially modified the CSTD terminal amines with CBAA. The dendrimeric products were thoroughly characterized. Our results show that the obtained CSTDs display strong correlation signals between the Ad and β-CD protons in the two-dimensional NMR spectrum, indicating the strong host-guest interaction existing between G3-Ad and G5-CD in the structure of CSTDs. Diffusion NMR measurements reveal that the hydrodynamic diameter of CSTDs is smaller after partial CBAA surface modification, possibly due to the tightened molecular volume after zwitterionic modification. Lastly, the CBAA-modified CSTDs were demonstrated to have good antifouling property through protein resistance assay. Our findings provide a new strategy to study the framework of the developed CSTDs and CBAA-modified CSTDs, facilitating their further design and surface modification for various biomedical applications.