A Functionalized Polydopamine Theranostic Probe For Efficient Imaging Of MiRNA-21 And In Vivo Synergetic Cancer Therapy

Background: In recent years,polydopamine(PDA)nanoparticles obtained by dopamine auto-polymerization have been extensively studied.Polydopamine(PDA)has good surface modification ability and biocompatibility.With the help of nanotechnology,combining multiple treatments into a single system for combined cancer treatment has great potential and solid progress in overcoming the limitations of monotherapy.As a new cancer biomarker,microRNA(miRNA or miR)has attracted many researchers’ attention due to its high expression level in almost cancer types and its role in controlling tumor suppressor genes.MicroRNA-21 is a typical example of oncogenic miRNA,and is involved in the occurrence and development of most tumors.Therefore,this study aims to design a functionalized polydopamine theragnostic probe for efficient imaging of miRNA-21 for early diagnosis of tumors and in vivo synergistic cancer treatment of chemotherapy and gene therapy.Materials and Methods: In this study,PDA was synthesized from dopamine hydrochloride and functionalized with polyethylene glycol(PEG)to improve their physiological stability and biocompatibility.As multifunctional nanocarriers and quencher,we used PDA-PEG nanoparticles loaded with FITC fluorescent labeled hair-pin DNA contained miR-21 binding sequence and an anticancer drug DOX(doxorubicin),designed a high biocompatibility and integration of nanoparticles drug delivery system,used in fluorescent imaging guided chemotherapy and gene therapy of synergy,integration in the diagnosis and treatment of tumor.Then we verify the diagnosis and treatment effect of PDA-PEG-DOX-hpDNA nanoprobes in vitro,cellular and in vivo,respectively.Results: We found that PDA-PEG nanoparticles showed good stability in different solutions.In vitro,PDA-PEG nanoparticles can effectively quench FITC fluorescence labeled hair-pin DNA,and can effectively restore fluorescence in the presence of exogenous miR-21,laying a foundation for tumor imaging,and can effectively load chemotherapy drugs DOX which can be responsively released in the acidic microenvironment to realize tumor diagnosis and treatment.At the cellular level,endogenous miR-21 in tumor cells such as P19,A549,7901 and 4T1 cells could effectively restore the quenched FITC fluorescence of PDA-PEG-hpDNA nanoprobe,while MCF-10a cells could not restore the fluorescence of nanoprobe.In tumor cells,PDA-PEG has no obvious toxic and side effects on the cells even at high concentrations.PDA-PEG-DOX-hpDNA nanoparticles loaded with diagnostic factors can be effectively taken up by cells,release DOX,produce cytotoxicity.and inhibit the function of miR-21 to kill cancer cells.In vivo,PDA-PEG-hpDNA nanoparticles can effectively enrich tumor sites in mice,restore the FITC fluorescence and realize tumor diagnosis.At the same time,PDA-PEG-DOX-hpDNA nanoparticles can achieve synergistic treatment with chemotherapy and gene therapy,effectively inhibit the growth of 4T1 tumors in nude mice,and achieve therapeutic effects.Conclusions: In this study,we designed and synthesized a multi-functional diagnostic and therapeutic integrated nano-probe based on polydopamine nanoparticles,denoted as PDA-PEG-DOX-hpDNA.By detecting the expression of endogenous miR-21 in tumor cells and recovering the quenched FITC fluorescence of the PDA-PEG-DOX-hpDNA nanoprobe,early diagnosis of tumors can be achieved.At the same time,by inhibiting the miR-21 to suppress tumor suppressor gene expression,cooperating with DOX mediated cytotoxicity released by pH response to achieve synergistic treatment of chemotherapy and gene therapy,thereby achieving the integration of tumor diagnosis and treatment.Therefore,we hope that this nanomedicine-loaded system will provide a new research strategy for future tumor diagnosis and treatment.