Schematic of the formation for the attachment of CS/GS via electrostatic interactions with QD-INS. At pH 7, QD-INS has a negative ζ -potential (Extended Data Fig. 1 ) concentrated at the C terminus of the α and β chains. CS/GS has a positive ζ -potential (Extended Data Fig. 1 ) and interacts via hydrogen bonding between the primary amines of CS/GS and B21, 25–27 and 30 amino acids. Conjugation of insulin with QD demonstrates similar FTIR spectra to insulin alone; coating with CS/GS modified the FTIR spectra to appear as a CS/GS alone (Extended Data Fig. 2a ).
