Photocontrolled Charge Reversal Nanoparticles Enhance Chemotherapy-Photodynamic Combination Therapy For Tumors

Multimodal combination therapy has become an effective strategy in clinical practice.It has been proved that photodynamic therapy(PDT)can be combined with chemotherapy to improve the efficacy of tumor treatment and overcome drug resistance due to its characteristics of minimally invasive,controllable,high efficiency,strong specificity,and little drug tolerance.However,chemotherapeutic drugs and photosensitizers have different pharmacokinetics and biological organ distribution in vivo,and both of their free forms have shorter half-life in vivo and lower selectivity to tumor cells.Therefore,how to deliver them to tumor tissue specifically,efficiently,and synchronously to achieve the best therapeutic effect is the key point to realize their clinical application.To sum up,in this paper,we designed a kind of nanoparticle(NP)with a shell core structure that can control the change of its surface charge through laser irradiation in vitro by taking advantage of the characteristics of cisplatin(IV)prodrug and photosensitizer.This special nanostructure can maintain negative charge in blood circulation.However,after reaching the tumor site and being irradiated by 650 nm laser,this NPs can be transformed into positive charge through the “peeling reaction” to enhance the tumor permeability of NPs and the efficiency of its internalization by tumor cells,and finally achieving the purpose of enhanced tumor therapy.The main findings are as follows:1.Firstly,we synthesized an amphiphilic tetravalent cisplatin prodrug,ML-Pt,which has a hydrophobic long fat chain at one end and a morpholine group acting as the “proton sponge” at the other end.Then photosensitizer porphin e6(Ce6)was loaded into the hydrophobic core of ML-Pt through hydrophobicity force to obtain micelle like structure PC-Pt/Ce6 NP.To further optimize its properties,the polymer with reactive oxygen species(ROS)responsive fracture characteristic poly-CHTA-co-PDSE-PEG was synthesized,by loading which on the surface of PC-Pt/Ce6 NP,NC-Pt/Ce6 NP with negative charge is obtained.The transmission electron microscope(TEM)images and dynamic light scattering(DLS)detection revealed that the NC-Pt/Ce6 NP is a kind of spherical structures about 100 nm.Subsequently,The DPBF experiment and electron paramagnetic resonance(ESR)detection were used to verify the ROS generation efficiency of NC-Pt/Ce6 NP in vitro and the feasibility of this charge-flipping strategy.2.Secondly,at the cellular level,we observed that NC-Pt/Ce6 NP can produce a strong level of ROS intracellular via confocal microscopy and flow cytometry.We also verified that this charge reversal design has a better promoting effect on the internalization of NC-Pt/Ce6 NP by tumor cells and its deep penetration effect on 3D cell spheres.In addition,we found that NC-Pt/Ce6 NP has strong toxicity to tumor cells via cell counting kit-8(CCK8)detection and cell apoptosis experiments.3.Subsequently,at the animal level,we verified the therapeutic effect of NC-Pt/Ce6 NP on LLC tumor-bearing mice and its safety in vivo.Then,through tumor inhibition experiments,after treatment with NC-Pt/Ce6 NP + L(NC-Pt/Ce6 NP with light treatment group),we found that the tumor inhibition effect can reach more than 60%.We also verified the deep penetration effect of NC-Pt/Ce6 NP in tumor and its enhanced internalization by tumor cells via tumor sections and flow cytometry experiments.In summary,we have developed a kind of smart drug delivery systems(SDDSs)that can change its surface charge by external light irradiation,which can not only improve the tumor selectivity and permeability of NPs in tumor tissues,but also could combine PDT with chemotherapy to obtain better tumor treatment effect.