Nano-engineered M1 Macrophage Enhances Amic Treatment Of Melanoma

Melanoma,one kind of malignant skin tumor,is the skin disease with the highest mortality rate.In 2020,there were 325,000 new melanomas worldwide,including 57,000 deaths.Finding effective therapies become the top priority for the treatment of melanoma.Photodynamic therapy（PDT）is an emerging non-invasive treatment for melanoma,which has the advantages of less trauma,high specificity,good tolerance,and sequential immune effects.The principle is that the laser irradiates the photosensitizer to an excited state,and under the interaction of the internal system,oxygen is converted to reactive oxygen species（ROS）.However,in the highly hypoxic melanoma microenvironment,photodynamic effects may exacerbate TME hypoxia or even promote melanoma development.Therefore,oxygen is the key to enhance photodynamic therapy and improve the hypoxic microenvironment of melanoma.Bovine serum albumin（BSA）was used as the main structure of nanoparticles.BSA is a water-soluble protein with good biocompatibility and abundant metal binding sites,which binds Mn²⁺and mineralization to manganese dioxide.Manganese dioxide catalyzes hydrogen peroxide（H₂O₂）to oxygen,which can be used for oxygen supply.In the acidic tumor microenvironment（TME）,manganese dioxide undergoes a catalytic reaction to convert to Mn²⁺.Mn²⁺is a paramagnetic substance that can be used as a contrast agent in magnetic resonance imaging（MRI）.Therefore,BSA-Mn O₂nanoparticles could both improve the hypoxic microenvironment of tumors and provide a substrate for photodynamic therapy,and the reaction products can be performed on MRI to facilitate therapeutic visualization.4,4-difluoro-4-Bora-3a,4a-diaza-s-indacenes（BODIPYs）are a new class of photosensitizing agents.The monoiodine-substituted BODIPYs（I-BDP）was more efficient to provide ¹O₂.Therefore,I-BDP was used as the photosensitizer binding to BSA-Mn O₂ nanoparticles,which finally synthesized BSA-Mn O₂-BDP（BMB）nanoparticles.However,as a nanoparticle with a large particle size（over 100 nm）,BMB still has some problems,such as（1）high immunogenicity and easy phagocytosis by the immune system;（2）The nanoparticles degrade before penetrating the tumor site;（3）The effect of targeting tumors is limited.Due to the heterogeneity of internal structure of tumors,the effect of targeting tumors by enhanced permeability and retention effect（EPR）alone is not reliable.Therefore,we used immune cells for drug delivery,among which M1macrophages are an ideal choice:（1）the natural phagocytosis of macrophages is easy to prepare the delivery system of macrophage-loaded nanoparticles,and macrophages have good phagocytic efficiency for nanoparticles of about 100 nm;（2）Macrophages as nanoparticle carriers can protect nanoparticles from the immune system and degradation;（3）Macrophages have the natural ability to target tumor cells and deliver nanoparticles to tumor cells by various means such as efflux and nanotubes.（4）M1 macrophages have a natural ability to kill tumor cells,which can increase the killing efficiency of tumor cells.（5）The endogenous hydrogen peroxide in M1 macrophages can form oxygen-rich"backpacks"under the catalysis of BMB nanoparticles to provide exogenous oxygen for tumors.Therefore,we designed a BMB nanoparticle delivery system（BMB@M1）using M1 macrophages as a carrier.The photosensitizer and manganese dioxide were attached to the nanoparticles by electron microscopy,X-ray diffraction and ultraviolet spectroscopy.CCK-8 and transwell experiments showed that the nanoparticles did not affect the viability of macrophages and tumor targeting ability.The results of confocal microscopy and flow cytometry showed that the macrophages carrying nanoparticles delivered drugs to tumor cells through efflux and nanotunnel.Both in vitro and in vivo experiments showed that the BMB@M1 could significantly alleviate the tumor hypoxic environment and enhance the photodynamic effect and sequential immune effect.Tumor growth was significantly inhibited after treatment.BMB@M1 targets melanoma sites,delivering drugs and providing exogenous oxygen.The released BMB nanoparticles were oxygenated in situ and provided MRI of the tumor site,facilitating subsequent immune effect and photodynamic therapy.This would be a promising treatment for melanoma.