The solvatochromic effects of side chain substitution on the binding interaction of novel tricarbocyanine dyes with human serum albumin

► Substitution at the alkyl indolium side chain of near infrared dyes enables variation to the binding affinity towards serum albumin. ► Substitution at the indolium side chain among an ethyl to butyl group results in improved binding characteristics and an almost three-fold increase in affinity constant. ► Binding interaction of tricarbocyanine dyes with serum albumin is influenced by hydrophobicity but may also be affected by steric hindrance beyond a certain ligand size.