Stimuli-Responsive Nanomedicine Toward Tumor Microenvironment Modulation And Anti-Tumor Therapy

Malignant tumors(cancers),as a global public health problem,are seriously threatening human health.In the clinic,the main cancer treatments include surgery,chemotherapy,and radiotherapy.Recently,with the further understanding of tumors,more treatments have been developed for tumor therapy.Among them,biological therapy,including immunotherapy,gene therapy,molecular-targeted therapy,stem cell therapy,and antibody therapy,is considered to be the fourth method for tumor treatment.Although biological therapy is promising and possesses great possibility in combating cancers,there are still numerous issues that need to be addressed.In the past few decades,nanotechnology has been widely used in biomedicine,making new hope and opportunities.By regulating the properties of nanocarriers,it is effective to achieve target delivery of small molecule drugs,increase drug utilization,extend blood circulation time,improve drug metabolism,and reduce side effects of chemotherapeutics.With the development of nanotechnology,increasingly more nanomedicines have entered clinical trials,and many of them have presented therapeutic effects.However,the clinical application of nanomedicine is still hindered by many factors.Such as the safety of nanocarriers,the instability of nanomedicines,non-specific drug release,insufficient drug accumulation toward tumor sites,and inadequate intratumoral penetration.In addition,the tumor microenvironment(TME),the "soil" of tumor growth,is characterized by complexity,diversity,heterogeneity,and dynamics,which affects the anti-tumor efficacy of nanomedicines.In recent years,comprehensive and personalized treatments are receiving considerable attention.Modulation of nano-properties and TME are two important methods to realize comprehensive and personalized treatment.The thesis focuses on TME modulation and combination therapy for anti-tumor therapy.Firstly,the cancer-associated fibroblast(CAF)-depletion and light-triggered size/charge convertible nanoclusters(NCs)was designed to enhance the hierarchical intratumoral penetration and improve the synergistic anti-tumor efficiency of photodynamic therapy and chemotherapy.Furthermore,the reactive oxygen species(ROS)-responsive size/charge convertible NCs were applied with the combination with tumor-targeting and-penetrating peptide for programmed intratumoral penetration.Then,a platelet-based nucleic acid/antibody sequential delivery system was engineered toward tumor immunosuppressive microenvironment modulation and cascading tumor immunotherapy.The main research topics of the thesis are summarized as follows:In Chapter 1,the tumor and the current tumor treatments,including tumor chemotherapy,photodynamic therapy,gene therapy,and immunotherapy,were outlined and described.Then,the TME,anti-tumor nanomedicine,and drug delivery systems were briefly reviewed.Also,the living cell-based drug delivery systems were sketched.In Chapter 2,the TME-adjustable and light-triggered size/charge-convertible nanoclusters(NCs)were designed to hierarchically promote the intratumoral penetration of chemotherapeutics and enhance the anti-tumor efficacy.A cancer-associated fibroblast(CAF)-targeting peptide(FAP-?,fibroblast associated protein ?)-modified,ROS-responsive,and main chain degradable triblock copolymer was engineered to envelope small-sized/positive-charged dendrimers that were conjugated with Ce6 and encapsulated with DOX(DCD)to form light-induced self-adaptive nanoclusters(NCs).NCs after light-triggered degradation significantly increased their penetration depth in 3D cell spheroids in vitro(>90 ?m).After systemic administration,the large-sized/negative-charged NCs(?50 nm,-1.5±1.4 mV)efficiently targeted CAF and generated lethal levels of 1O2 upon light irradiation,which depleted CAF and concomitantly dissociated the NCs to liberate the small-sized/positive charged DCD(?5 nm,+15.4±1.6 mV).The attenuated tumor stroma after CAF depletion and the small size/positive charge of DCD could efficiently promote the penetration of DCD into the deeper layers of the tumor.Finally,the released DOX from DCD together with the 1O2 produced by DCD upon light irradiation synergistically eradicated the tumor cells embedded deep in the solid tumors.This study expands the application of photodynamic therapy,provides a reference for the light-induced controlled drug release,and enriches the application of programmed tumor penetration.In Chapter 3,the combination of tumor-targeting and-penetrating peptide iRGD and light-triggered self-adaptive NCs was engineered to hierarchically improve the intratumoral penetration and enhance the anti-tumor efficacy.The light-assisted,ROS-responsive,and degradable size/charge convertible self-adaptive NCs in Chapter 2 was used to regulate the properties of nanomedicines and combined with iRGD to hierarchically promote intratumoral penetration.Co-administration of iRGD and NCs effectively increased the penetration depth in A549 3D cell spheroids in vitro(>90?m).After systemic administration,iRGD notably enhanced the accumulation of NCs,the permeability of NCs within tumor vasculature,and tumor penetration.Upon far-red light(660 nm)irradiation of tumors at a low optical density(10 mW/cm2),the generated 102 could disintegrate the NCs and release the DCD with positive surface charge and ultra-small size(?5 nm),which synergized with iRGD to enable deep intratumoral penetration.Consequently,chemotherapy and photodynamic therapy synergistically eradicate tumor cells and improve tumor suppression.This study provides an effective way to achieve spatiotemporal control and promote intratumoral penetration of nanomedicines and programmed anti-tumor therapy.In Chapter 4,platelet(PLT)-based nucleic acid/antibody sequential delivery system was designed for cascading anti-tumor immunotherapy.PLT(?2-4 ?m in diameter)enveloped polypeptide/siRNA polyplexes(PP)(<100 nm)by its open canalicular system and "backpack" phenylboronic acid decorated and reduction-responsive anti-PD-L1 nanoparticles(?50 nm)using its surface sialic acid which was highly expressed by the PLT.The loading efficiency of PLT(2×108/mL)for nucleic acid PP(20 ?g/mL)and antibody nanoparticles(200 ?g/mL)was higher than 80%.Moreover,the PLT/PP could effectively knockdown Rab27a in B16F10 cells(gene knockdown efficiency,?70%),and thus inhibit the exosomes secretion(inhibition rate,?80%).After systemic administration,PLT could firstly accumulate in the tumor site,inhibit the secretion of tumor exosomes via RNAi,relieve the systemic immune suppression,promote the proliferation of effective T cells at lymph node,and increase the migration of the effective T cells to tumor;then,the increasing effective T cells within tumor degrade the reduction-responsive antibody nanoparticles through the rich sulfhydryl groups on the surface to promote the release of the anti-PD-L1;finally,relieve the immune suppression of infiltrating T cells achieving the cascading anti-tumor immunotherapy.This work could expand the living cell-based drug delivery systems,realize sequential delivery,develop immune checkpoint blockade(ICB)combination therapy,and provide sequential modulation and cascading immunotherapy.In Chapter 5,a summary of this thesis and prospects were provided.In summary,firstly a strategy for TME modulation and hierarchical delivery of stimuli-responsive nanomedicine was proposed in this thesis.Then,the effects of the concurrent modification of TME and nano-properties toward intratumoral penetration were studied.Also,a combination treatment of TME modulation and ICB via the cascading anti-tumor immunotherapy was investigated.Therefore,this thesis could provide new strategies for TME regulation to promote intratumoral penetration of nanomedicine,supply novel paradigm for gene or antibody delivery based on living cells,and expand programmed and cascading anti-tumor immunotherapy.