The impact of N-terminal modification of PAA with different chain lengths on the structure, thermal stability and pH sensitivity of succinylated collagen

Abstract The limitations of native collagen, such as thermal stability and solubility in physiological environments, can be improved by applying bioconjugation and synthetic chemistry techniques. However, the exquisite control of the modification site of collagen remains a challenge. In this work, pH-responsive poly(acrylic acid) (PAA) with different chain lengths was attached to the N-terminal α-amino groups of succinylated collagen using a site-specific modification strategy. Additionally, the structure, thermal stability, and pH sensitivity of succinylated collagen were explored. The modification rate of amino groups in the succinylated collagen-PAA bioconjugate (SPSC-PAA) was evaluated by the 2,4,6-trinitrobenzene sulfonic acid assay. The impact of N-terminal modification of PAA and its chain length on the thermal stability of collagen was explored by CD and DSC. These techniques revealed that the thermal stability of SPSC-Col is pH-responsive and closely related to the chain length of grafted PAA. The pH sensitivity of SPSC-PAA was further explored by rheology and turbidity. Subsquently, the critical pH and isoelectric point of SPSC-PAAs were also examined by turbidity and isoelectric point titration, respectively. This work provides a new insight into the N-terminal modification of collagen on its properties. Graphical abstract