Self assembled biomaterials have attracted wide attention due to their potential applications in biomedical imaging, drug delivery and disease diagnosis and treatment, and have become one of the frontier fields in recent years. In recent decades, scholars have gained inspiration from their understanding of amino terminal, natural polypeptide and protein, and constructed self-assembled polypeptide [3] The typical self-assembled polypeptide klvff, N-Fmoc-7-methyl-L-tryptophan whose sequence is derived from Alzheimer's disease-related β- Amyloid protein.

The functional modification sites of self-assembled polypeptides mainly include the amino and carboxyl groups of the main chain and the amino, carboxyl, hydroxyl and mercapto groups of the side chain, There are two main modification methods: one is direct modification, that is, direct covalent coupling of functional molecules with polypeptidesFmoc-Pen(Acm)-OH, or direct covalent coupling of molecules with polypeptides after activation of active groups The functional molecules in this method mainly include:

(1) Drug molecules, which directly modify drug CBZ-OSu molecules on polypeptides to achieve accurate drug delivery and disease treatment;

(2) Probe molecules, using the air effect of self-assembled polypeptides, achieve high-efficiency enrichment of probes at the lesion site and enhance the signal-to-noise ratio of imaging;

(3) Alkyl chain, which can adjust the hydrophilic hydrophobic balance and enhance the assembly ability;

(4) Polymer, polymer steric hindrance is large, hindering polypeptide assembly, but polymer characteristics are required in specific strategies;

(5) Sugar, sugar participates in a variety of physiological activities in the organism, and glycopeptide self-assembly can participate in physiological activities through multivalent coordination effect, enzyme shearing and other ways;

(6) Other molecules, in addition to the above types, there are many other small molecules that are valuable for polypeptide assembly We will choose the one that is more commonly used for discussion The second is indirect modification, that is, linking functional molecules with polypeptides by using linking units Some molecules have large steric hindrance, or because they do not have active groups that can efficiently connect with polypeptides, other molecules need to be introduced as connecting units

(1) drug molecular modification

Taking advantage of the recognition and treatment of small molecule drugs on the lesion area and their own hydrophilic and hydrophobic properties, covalently coupling them with self-assembled polypeptide materials can prolong drug retention, enhance drug efficacy and reduce toxic and side effects In order to connect drug molecules to polypeptides more conveniently, some functional groups of drug molecules need to be activated