Quantitative Study On Self-assembly Efficiency Of Self-assembled Peptide Nanomaterials In Vivo Based On MRI

Self-assembled nanomaterials consist of basic structural units based on interactions between non-covalent bonds,which can spontaneously arrange into ordered nanostructures with certain functions or morphologies.Self-assembly process can be found everywhere in nature,such as DNA with double helix structure formed by nucleotide self-assembly and protein with complex structure formed by polypeptide self-assembly.Inspired by this,the assembly of nanomaterials has become a research hotspot in recent years,which has promoted the development of the nano-field.In vivo self-assembly refers to the self-assembly in cells,tissues or living organisms by introducing exogenous molecules into specific physiological and pathological environment to construct controllable high-level ordered structures.This strategy has the advantages of active or passive targeting to specific lesion sites and recognition of induced self-assembly.As a new targeting mechanism,it can show efficient enrichment and retention in specific sites,that is,assembly induced retention effect(air),and it has the advantages of high penetration like small molecules in tumor sites and similar pharmacokinetics of small molecules with low systemic toxicity in other organs except tumor.These advantages indicate that the in vivo self-assembly strategy of regulating the morphology and properties of basic structural units in complex biological environment,so as to realize the function of bioactive components in specific lesions,has great development prospects in biomedical applications.However,the current research based on in vivo self-assembly system only stays on the qualitative basis,and there is no systematic quantitative method to accurately measure the assembly efficiency of our designed molecules in vivo.However,the monitoring of the dynamic assembly process and the measurement of the assembly efficiency of the lesion site are conducive to further understanding and interpretation of the air effect,and provide a new idea for the development of high efficient and low toxic biomaterials.Therefore,the measurement of self-assembly efficiency in vivo is challenging,but it has significant scientific significance.In view of this,in this work,we developed a self-assembly system with targeting,tailoring and assembly properties to measure the assembly efficiency of molecules in vivo in real time and quantitatively.Using magnetic resonance imaging(MRI)technology to get more accurate real situation of the tissue to be tested,in order to achieve the purpose of quantitative detection of assembly and monomer,so as to realize the research of self-assembly efficiency in vivo.We first verified the self-assembly behavior of metallochlorophyll derivatives at the solution level.The critical micelle concentration(CMC)showed that the molecules were sheared to form self-assembled nanofibers with a width of 19.3 nm by transmission electron microscopy(TEM).Then,the optical properties of the molecule before and after assembly were verified by characterizing the optical properties of the molecule at the solution level.Next,we measured the relaxation rates of the assembled and monomer molecules at the solution level.The experimental results show that the relaxation rates of the assembled and monomer molecules have significant changes.r₁=1.58 m M^-1s^-1,r₂=6.18 m M^-1s^-1for monomer,r₁=3.03 m M^-1s^-1,r₂=79.06 m M^-1s^-1for assembly,which enables the signal separation between monomer and assembly.Then the enzyme-specific cleavage function of the molecule was verified by assembly induced fluorescence quenching at the cell level,and the results showed that the molecule could be effectively cleaved.The results showed that with the increase of incubation time,the self-assembly efficiency of molecules had an obvious upward trend,and reached the maximum of 71.3%at 8 h,and then decreased.The possible reason for this phenomenon is that molecules are degraded or metabolized out of cells.Finally,we verified the method of calculating the assembly efficiency at the animal level,and the results showed that the assembly efficiency of this molecule reached 55.6%in tumor bearing mice.In this paper,the assembly efficiency of in vivo self-assembly system was quantitatively measured by MRI strategy for the first time,and the signal separation of monomer and assembly in complex environment was successfully realized by MRI strategy.This method not only solves the problem that the fluorescence signal is restricted by various factors in vivo,but also solves the limitation that photoacoustic imaging technology can only measure the assembly efficiency semi quantitatively.This is of great significance for the design of molecules and the construction of precise self-assembly system in vivo,and provides new ideas for the development of new efficient and low toxicity biomaterials.