Study On The Supramolecular Structure And Spectral Properties Of Epinephrine Melanin

Melanin is an interesting biological material with unique physical and chemical properties,which is related to human pigmentation,the occurrence of melanoma,and the synthesis of neuromelanin in the brain.It is also playing an increasingly important role in the application of functional biomaterials.In 2007,it was proved that proper imitation of these biological processes can be a highly resistant and viscous material suitable for deposition of thin films and multifunctional coatings.It can provide a way of entry.These materials exhibit excellent properties such as adhesion,hydrophilicity,stability,and biocompatibility,and have many applications in many fields.However,due to the insolubility of synthetic melanin made from different precursors such as 3,4-dihydroxyphenylalanine(DOPA)and dopamine(DA),it is still challenging to reveal the relationship between structure and properties.In this paper,from the perspective of supramolecular chemistry,the auto-oxidation of epinephrine(EP)under alkaline conditions was studied,and the soluble epinephrine-melanin(EPM)formed was characterized at the nanometer level.The specific research work is mainly introduced from the following three aspects.(1)The properties of supramolecular aggregates of adrenaline oxidation products have been determined based on spectroscopic studies.Studies have found changes in the ultraviolet spectrum and fluorescence spectrum during the oxidation of adrenaline.Due to the insolubility of melanin,there is currently no spectroscopic method to explore the kinetic process of its self-oxidation.In this study,the spectral changes of adrenaline oxidation products with very good solubility were used to study the oxidation and aggregation kinetics of EP in three different alkaline systems through the combination of absorption and fluorescence spectroscopy.The oxidation process of EP shows concentration and buffer dependent behavior.The use of spectroscopy to explore the oxidation process of melanoids provides new ideas in this field.(2)The morphology of adrenaline oxidation products is quite different from the previously reported dopamine melanin.In this study,a two-dimensional sheet-like morphology with a highly ordered in-plane stacking structure was observed in the melanin field for the first time.And the thickness of the nanosheets increases with the increase of EPM concentration.More importantly,contrary to the well-known monotonic absorption curve of synthetic melanin,EPM shows a characteristic and abnormal p H response absorption curve in the near ultraviolet region(UVA).The decrease in p H leads to the disappearance of absorption in the lower energy band and the reduction of aggregate size.This also confirms that the characteristic absorption peak in the near ultraviolet region is determined by the size of adrenaline aggregates.EPM has extraordinary absorption characteristics and can be used to make transparent ultraviolet-shielding chitosan biofilms and gelatin hydrogels with good antibacterial properties.(3)At the same time,using the reducibility of EPM,metal nanoparticles with good dispersibility and uniform size can be reduced,which solves the problem of easy agglomeration of gold and silver nanoparticles.And through its combination with soft substance gelatin,it can be used to explore the injectability of organisms,which has great research value for the antibacterial properties of organisms.This study confirmed the reason for the formation of the characteristic peak of EPM,and explored the factors affecting the characteristic peak.Through a series of characterizations,the two-dimensional sheet structure and p H responsiveness of EPM were discovered,and its special spectral characteristics and reducibility were used for application..In the follow-up,we will use some special properties such as the viscosity and biocompatibility of adrenaline oxidation products to deeply explore its applications in biomedicine,physics,etc.,and the molecular structure of EPM,supramolecular exciton coupling and material-oriented properties.Extensive research is highly anticipated.