Preparation,Modification And Properties Of Polydopamine Submicrospheres And Their Composites

In recent years,new treatments have been investigated,such as photothermal therapy（PTT）using near-infrared heat conversion and applying it to cancer treatment.PTT is a new kind of non-invasive treatment using visible light or near-infrared light.This treatment method uses photothermal reagents to absorb a large amount of light energy and generate heat at the tumor site to achieve rapid heating and a new non-invasive diagnosis and treatment technology to kill the cancer cells.With the help of laser positioning,it can achieve targeted elimination of malignant tumors without causing systemic effects.Polydopamine（PDA）is a kind of photothermal agent with good photothermal performance.It can absorb light energy and efficiently convert it into heat energy,so that the local tumor temperature can be above 45℃,and then kill cancer cells.This characteristic makes PDA have good application in photothermal therapy.Moreover,compared with other inorganic photothermal reagents,the preparation method of polydopamine is simpler and easier to operate.As long as there is air and alkaline conditions,the oxidation and self-polymerization reaction of dopamine hydrochloride can be carried out.PDA has strong adhesion,can adhere to the surface of a variety of materials,for other materials to modify,and PDA surface also has a large number of-OH groups,can react with other metal ions,such as the formation of rare earth coordination polymer with Gd³⁺.Because of these properties,PDA,a photothermal reagent,can be well modified to increase other performance,such as drug delivery,biological imaging and reducing the cytotoxicity of substances.Therefore,in this paper,PDA was used as ligand to synthesize a series of photothermal reagents with biological imaging function.It provides a new method and idea for the preparation of reagents for the integration of diagnosis and treatment in cancer treatment.（1）Controllable preparation and study of polydopamine（PDA）microspheresUsing dopamine hydrochloride as raw material,diethanolamine as base source,ultra-pure water and ethanol as solvents,PDA microspheres with different sizes were prepared by adjusting the ratio of ultra-pure water to ethanol.The size of PDA microspheres obtained is relatively uniform and the dispersion is good.Then,the structure and properties of the PDA microspheres were characterized by SEM,TEM and infrared imager.Meanwhile,the dispersion and cytotoxicity of the materials were investigated.The experimental results show that the PDA microspheres prepared by diethanolamine have good photothermal properties,biocompatibility and low cytotoxicity without producing irritating gas.This study can provide a new idea and reference for the preparation of PDA with organic alkaline material.（2）Preparation and properties of polydopamine microspheres（PDA-Gd）coordinated with gadoliniumUsing the abundant-OH on the surface of PDA submicrospheres,the prepared PDA ultramicrospheres reacted with the rare earth ion Gd³⁺with MRI properties in the environment of anhydrous ethanol to prepare the coordination PDA ultramicrospheres with Gd³⁺.This kind of submicrospheres has a strong near-infrared absorption property in terms of light energy absorption,which enables it to act as a photothermal agent.PDA-Gd has high drug loading rate and encapsulation rate,and has good drug loading ability,which endows it can be used as drug carrier.The photoacoustic signal and T1 magnetic resonance signal of the submicrospheres are strong,so that PDA-Gd can also be used as a contrast agent for dual imaging,and realize dual imaging PTT while killing cancer cells.The results of this study can provide a new idea and reference for PDA in PTT,drug loading and biological imaging.（3）Preparation and properties of gold nanoflower（Au@PDA-Gd）composite with polydopamine coordination with gadoliniumThrough the PDA in any material surface can be polymerized,the surface of the gold nanoflower coated with a layer of PDA,and then the use of PDA surface-OH,effective coordination of Gd³⁺,finally get Au@PDA-Gd composite photothermal agent.The material has good photothermal performance,drug loading performance,and in vitro imaging performance.In the future,the composite material may have a huge prospect of medical application as a photothermal conversion reagent and triple imaging contrast agent.At the same time,this study can provide new ideas and references for PDA in PTT,drug loading and biological imaging.