Rare Earth-semiconductor Composite Material For Antitumor Photodynamic/Photothermal Therapy

Photodynamic therapy(PDT)and photothermal therapy(PTT)are new anti-cancer methods that have been widely studied in recent years.Compared with traditional cancer treatment methods,the research of fiery photothermal therapy and photodynamic therapy in recent years has the advantages of small side effects,good targeting,small wounds,good effects,and lower costs.Early photochemotherapy used ultraviolet light as the light source,but ultraviolet light is easily absorbed by biological tissues,which leads to reduced efficiency of imaging and treatment;and near infrared light has deeper tissue penetration and higher imaging noise.In contrast,it is used as a stable and efficient light source in the current research of photochemotherapy.The up-converting luminescent material mainly composed of rare earth inorganic nanoparticles uses the near infrared light as the excitation light source,and emits visible light for imaging and treatment.Compared with other fluorescent dyes(quantum dots,organic dyes),rare earth up-conversion luminescent materials have the advantages of high chemical and luminescent stability,narrow emission peak,low toxicity and no autofluorescence.Due to its special energy band structure,semiconductor materials can generate singlet oxygen or release a lot of heat when they receive light of the appropriate wavelength(ultraviolet or visible light).After the rare earth up-conversion luminescent material and semiconductor material are combined,the semiconductor material with ultraviolet and visible light response can absorb the ultraviolet light and visible light emitted by the up-conversion,so that the photodynamic and photothermal treatment effects can be achieved under the irradiation of near infrared light.In addition,this composite material also has the function of biological imaging,thus achieving the integration of tumor diagnosis and treatment.This article combines several different semiconductor materials with up-conversion nanomaterials to study the photothermal/photodynamic efficiency and bioimaging effects of these composite materials.The specific research contents are as follows:A new type of PDT agent made of mesoporous rare earth-semiconductor composite materials can obtain a large amount of singlet oxygen under near-infrared(NIR)laser irradiation.Hydrothermal method is used to synthesize large-scale(120 nm)up-converted nanoparticles(NYF),and coat the surface with semiconductors with different thicknesses of mesoporous morphology.Sn O₂ and Ti O₂ used in the experiment have wide absorption bands in the ultraviolet region.Under the excitation of near-infrared laser,the ultraviolet fluorescence emitted by NYF can be used as an energy donor.After the semiconductor absorbs energy,it generates an electron-hole pair and transfers to the surface of the semiconductor to generate singlet oxygen.PDT efficiency of NYF@Sn O₂ samples was studied using DPBF detector,in vitro MTT analysis,and in vivo tumor suppression experiments,which showed that rare earth-semiconductor composites can be used as PDT reagents under NIR excitation.Degradable Fe₃O₄@m SiO₂@UCNP was used as an imaging-guided PTT/PDT agent.Fe₃O₄ nanoparticles were successfully prepared by solvothermal method,and rare earth up-conversion nanoparticles(UCNP)were supported in a porous structure by electrostatic adsorption.On the one hand,under the irradiation of 808nm laser,Fe₃O₄@m Si O₂@UCNP can not only heat up rapidly,but also generate a large amount of singlet oxygen;on the other hand,the composite material can identify tumor cells with magnetic response,and then present strong PA and up-conversion luminescence signals.In addition,Fe₃O₄@m Si O₂ can be degraded as a drug carrier.Therefore,Fe₃O₄@m Si O₂@UCNP can be used as a diagnostic probe for PTT/PDT therapy guided by magnetic targeted bimodal imaging.Typical organic/inorganic photothermal therapy agents(polypyrrole,dopamine,carbon layer,manganese dioxide and copper sulfide)are combined with up-conversion luminescence(UCL)imaging rare earth nanomaterials for PA under NIR/UCL imaging guided PTT.Through the analysis of the light and heat sources,luminous intensity and stability of several composite materials,the following conclusions are obtained:(a)The PTT effect mainly comes from near-infrared absorption,and part of it comes from UCL light conversion.(b)The visible UCL emission is mainly quenched by the near-infrared absorption of the coated PTT material,and partially quenched by visible light absorption,which indicates that the excitation may play a more important role than in the UCL emission process.(c)The biochemical stability of composites depends on the reaction temperature of the synthesis.UCNP@Mn O₂ has the ability to stimulate and respond to the slightly acidic environment of tumor cells and the highest biological stability.