Photothermal Effects Of NaYF₄:Yb,Er@Pei@Pah@Fe₃O₄ Nanoprobes In The Treatment Of Melanoma

Melanoma represents the most aggressive and the deadliest form of dermatologic cancers.Prognosis of patients with metastatic melanoma is very poor,with only 14%of patients surviving for five years.Current therapeutic options include surgical resection,chemotherapy,photodynamic therapy,immunotherapy,targeted therapy and others.However,efficiency of these treatments commonly decreases due to the development of diverse resistance mechanisms,necessitating continued search for novel therapeutic strategies with higher efficacy.In recent years,tremendous advancement in nanotechnology research has provided a variety of multifunctional nanomaterials with unique optical properties,which enables ablation of tumor cells by imaging-guided photothermal therapy?PTT?.PPT is minimally-invasive and has become a promising cancer treatment modality.It induces local hyperthermia by photothermal coupling agents that convert the highly transmissive near-infrared?NIR?light to heat.Since cancer cells are intolerable to elevated temperature,PTT selectively eradicates them and spares healthy cells intact.Thus,PTT causes few side effects that commonly occur when using conventional therapies.One particular type of such nanomaterials that has provoked widespread interest is lanthanide(Ln³⁺)-doped nanoparticle?e.g.NaYF₄:Yb,Er?integrated with a superparamagnetic shell?e.g.Fe₃O₄?.Compared to many other hyperthermic agents,Fe₃O₄ nanoparticles shows a much higher versatility and biosafety.Markedly,the as-formed NaYF₄:Yb,Er@Fe₃O₄ nanocore allows for Infrared thermal imaging/upconversion luminescence?UCL?/MRI multimodality imaging,which ensures both real-time imaging with high spatial resolution and accurate diagnosis with deep tissue penetration.Although the Ln³⁺-doped magnetic Fe₃O₄ nanoparticles usually possess high specific surface area,low toxicity and good biocompatibility,further surface modifications are usually essential for better clinical applications.Many studies reported the use of polyethylene glycol?PEG?as an attractive conjugation material.However,the presence of PEG on nanoparticle surface reduces cellular uptake,a drawback that can be overcome by replacing with polyelectrolytes?PEs?.In fact,PEs have been widely accepted to coat gold nanorods to increase the latter's long-term stability,hydrophilicity,drug delivery capacity and photothermal activity.Majority of nanoprobes with surface modifications efficiently accumulate at tumor sites due to the enhanced permeability and retention?EPR?effects of solid tumors.Therefore,modification of NaYF₄:Yb,Er@Fe₃O₄ nanocore with PE layers integrates multimodal imaging functions,such as infrared thermal imaging,UCL imaging and MRI imaging,with effective PTT against cancer cells.However,studies on PEs-coated NaYF₄:Yb,Er@Fe₃O₄ magnetic nanocomposites and their theranostic values are lacking..Objective:To synthesize the NaYF₄:Yb,Er@PEI@PAH@Fe₃O₄ nanoprobes and to study their photothermal effects for the treatment of malignant melanoma..Methods:Morphological characteristics of the synthesized nanoprobes were examined by scanning electron microscopy?SEM?.Their biocompati-bility and biodistribution profiles were assessed through blood routine/biochemistry tests and the inductively coupled plasma/optical emission spectrometry?ICP-OES?based analysis of tissue metal elements.Their photothermal conversion efficiency and their potential as contrast agents for upconversion luminescence/MRI dual-modal imaging were tested.Efficacy in photothermal therapy,which was achieved by combining nanoprobes with near infrared?NIR?irradiation,was evaluated in both A375 cell line and BALB/c mice models.The underlying mechanisms were interrogated by molecular approaches including MTT assay,flow cytometry,semi-quantitative PCR,western blot and immunohistochemistry.Results:1.Our synthesized NaYF₄:Yb,Er@PEI@PAH@Fe₃O₄ nanoprobes exhibited a uniform cubic morphology with diameter of 50 nm.Subcutaneous administration led to no severe,long-lasting adverse effects,possibly due to complete removal of these nanomaterials within one month.2.Our nanoprobes possessed superior photothermal conversion efficiency and strong contrasting effects during ITI/UCL/MRI multimodality imaging,corroborating their applications in imaging-guided photothermal therapy.3.Combinatorial treatment of these nanoprobes with NIR irradiation induced profound apoptosis/necrosis in A375 cells.Similarly,the same treatment modality led to strong therapeutic effects in BALB/c mice implanted with A375 tumor xenografts.4.Mechanistic studies suggested an involvement of heat shock protein 70?HSP70?in mediating the observed antitumor effects of our nanoprobes.Conclusion:Our study describes a convenient method to synthesize a new type of superparamagnetic upconversion nanoprobes,which possess high biocompatibility and can be used in imaging-guided photothermal therapy for the treatment of malignant melanoma.Importantly,our findings will promote clinical applications of NaYF₄:Yb,Er@PEI@PAH@Fe₃O₄ as novel theranostic agents in treating melanoma and many other tumors.