Preparation And Properties Of N-terminal Grafted Collagen

Because of its biocompatibility,collagen is frequently employed in biomedical applications.The superior physicochemical qualities of collagen can be integrated with its biological activity by polymer graft modification to create innovative biomedical materials that mix collagen and polymer features.Traditional grafting modification procedures,on the other hand,use random grafting sites,resulting in a combination of heterogeneous products made up of positional isomers.It is critical to choose specific collagen locations for accurate graft modification in order to generate structurally specified graft-modified collagen.Because the N-terminal region of collagen is important for co-translational transport and post-translational modification(PTM),targeting the N-terminal amino group of collagen for graft modification and then investigating the mechanism of N-terminal modification on the physicochemical properties of collagen is of great scientific significance.Natural grass carp skin collagen(ASC)was employed as the raw material in this thesis,along with telopeptides isolated in the laboratory,using active aminos from closed collagen surfaces→End peptides are cleaved by enzymes to create new amino groups→N-terminal amino graft modification strategies,As a model,environmentally responsive polymers were used,the N-terminal amino group of collagen was modified precisely for grafting,the structure and characteristics of the N-terminal precision graft-modified collagen that resulted were next investigated.The goal was to figure out how N-terminal responsive polymer grafting changed the properties of modified collagen.The following are the key studies:(1)The qualities of succinylated collagen prepared with N-terminal grafted poly-N-isopropylacrylamide(PNIPAAm)(SPSC-PNIPAAm): The temperature-sensitive polymer PNIPAAm was employed for accurate grafting of collagen N-terminal after succinylation of collagen with enzymatic cleavage of telopeptides.TNBS colorimetry,gel permeation chromatography(GPC),and turbidity experiments showed that PNIPAAm was successfully grafted onto the N-terminal amino group of collagen with a molecular weight of 4257 Da;circular dichroism(CD wavelength scan)revealed that the grafting process had no effect on collagen’s triple helix structure;The modified collagen exhibited significant temperature-sensitive phase transition behavior,as demonstrated by turbidimetric and rheological experiments;circular dichroism(CD temperature scan)revealed that N-terminal grafting of PNIPAAm improved the thermal stability of succinylated collagen triple.Water solubility tests revealed that succinylation and N-terminal grafting of PNIPAAm considerably increased the collagen’s water solubility and water dissolving rate;CCK8 cell tests revealed that SPSC-PNIPAAm was still cytocompatible.(2)Preparation and characteristics of succinylated collagen(SPSC-PAA)with polyacrylic acid(PAA)N-terminal grafting: The N-terminal collagen was carefully grafted with the p H-responsive polymer polypropylene PAA after succinylation and enzymatic cleavage of end peptides.Turbidimetric and rheological investigations confirmed the p H responsiveness of SPSC-PAA;CD temperature scanning and differential scanning calorimetry(DSC)experiments indicated the mechanism of electrostatic interaction on collagen triple helix structure and stability:The degree of ionization of carboxyl groups might change the spatial resistance of the collagen triple helix structure,modifying its heat stability.The degree of ionization of carboxyl groups can change the heat stability of the collagen triple helix structure by affecting its spatial resistance.(3)Short-,medium-,and long-chain PNIPAAm and PAA were grafted at the N-terminal end of succinylated collagen to construct N-terminal modified collagen sample populations,and the effect of grafted polymer chain length on the physicochemical properties of the modified collagen was investigated.When the molecular weight of PNIPAAm was increased in the N-terminal grafted PNIPAAm-modified collagen sample group,turbidity experiments revealed that the modified collagen’s LCST decreased and the gelation rate accelerated;CD temperature scans revealed that the modified collagen triple helix’s thermal stability increased.After increasing the molecular weight of PAA in the N-terminal grafted PAA-modified collagen sample group,turbidity experiments revealed that the modified collagen’s critical phase transition p H decreased;CD temperature scan and DSC revealed that the modified collagen’s triple helix thermal stability was improved at p H=4.The number of specific functional groups(isopropyl and carboxyl groups)on the polymer can affect the physicochemical properties of the modified collagen,and the molecular weight of the polymer can be changed to achieve the goal of modulating the properties of the modified collagen,when combined with the experimental results of the two sample groups.This research focuses on the mechanism of N-terminal grafting modification on changed collagen characteristics,which offers a novel approach to precise collagen modification.