摘要
Cancer is one of the most severe disease burdens in modern times, with an estimated increase in the number of patients diagnosed globally from 18.1 million in 2018 to 23.6 million in 2030. Despite a significant progress achieved by conventional therapies, they have limitations and are still far from ideal. Therefore, safe, effective andwidely-applicable treatments are urgently needed. Over the past decades, the development of novel delivery approaches based on membrane-core (MC) nanostructures for transporting chemotherapeutics, nucleic acids and immunomodulators has significantly improved anticancer efficacy and reduced side effects. In this review, the formulation strategies based on MC nanostructures for delivery of anticancer drug are described, and recent advances in the application of MC nanoformulations to overcome the delivery hurdles for clinical translation are discussed.
癌症是现代最严重的疾病负担之一，估计全球诊断出的患者人数从2018年的1810万增加到2030年的2360万。尽管传统疗法取得了重大进展，但它们仍然存在局限性，并且仍然 远非理想。 因此，迫切需要安全，有效和广泛应用的治疗方法。 在过去的几十年中，基于膜核心（MC）纳米结构的新型转运方法的开发，用于转运化学治疗剂，核酸和免疫调节剂，显着提高了抗癌功效并减少了副作用。 在这篇综述中，描述了基于MC纳米结构的抗癌药物递送策略，并讨论了MC纳米制剂在克服临床翻译中的递送障碍方面的最新进展。
1. Introduction 1.引言
Cancer is among the leading causes of mortality across the world with an estimated 9.6 million deaths in 2018, and the number of patients newly diagnosed with cancer is expected to rise to 23.6million in 2030 (www.cancer.gov). The surgical, radiotherapeutic and chemotherapeutic strategies may provide curable means for cancer at early stages, but the prognosis is still poor for patients with advanced and metastatic cancers [1]. Recent advances in the development of small molecule inhibitors, nucleic acids and immunomodulators have significantly revolutionized the field of cancer therapy, but the application of these therapies to patients is retarded by limitations such as drug resistance, non-specific delivery, and toxicity [2]. It is well established that the clinical translation of these anticancer agents is highly dependent on the success of the delivery approach.
癌症是全球主要的死亡原因之一，据估计，2018年有960万人死亡，到2030年，新诊断出癌症的患者人数有望增加到2360万（www.cancer.gov）。外科手术，放射治疗和化学疗法策略可能为早期癌症提供可治愈的手段，但是对于晚期和转移性癌症患者，预后仍然很差[1]。小分子抑制剂，核酸和免疫调节剂开发的最新进展已极大地改变了癌症治疗领域，但由于耐药性，非特异性递送和毒性等限制因素，这些疗法在患者中的应用受到了阻碍[2]。众所周知，这些抗癌药的临床翻译高度依赖于递送方法的成功。
In recent years, substantial research has been undertaken regarding the design and assessment of nanoparticle (NP)-based delivery carriers for providing safe, effective and patient-acceptable therapeutic approaches [3]. Among these, the membrane-core (MC, also known as core-shell) nanostructure becomes a promising platformfor developing cancer nanomedicine. This review describes MC formulation strategies for cancer therapy, and the barriers associated with in vivo delivery. In addition, the development ofMC NPs under the investigation for cancer nanomedicine is described, with an emphasis on those designed to promise clinical translation.
近年来，已经进行了有关基于纳米颗粒（NP）的递送载体的设计和评估的大量研究，以提供安全，有效和患者可接受的治疗方法[3]。 其中，膜核（MC，也称为核壳）纳米结构成为开发癌症纳米药物的有前途的平台。 这篇综述描述了用于癌症治疗的MC制剂策略，以及与体内递送相关的障碍。 另外，描述了在癌症纳米医学研究中的MC NP的开发，重点是那些旨在保证临床翻译的NP。
2. Membrane-Core Nanostructured Formulations
MC NPs are generally characterized as a hybrid nanostructured system comprising inner core and exterior membrane, which can facilitate the combination of materialswith distinctive physical, chemical, and biological properties (Fig. 1). This ordered assembly nanostructure is formed through chemical bonds and/or physical interactions between inner core and exterior membrane. The classes, properties and synthesis approaches of MC NPs have been substantially reviewed elsewhere [4]. The MC NPs opens up the potential for design of multifunctional NPs that arewidely recognized favorable for biomedical application as compared toNPswith single functions. Fromdrug delivery point of view, the core materials can efficiently encapsulate therapeutic cargos, and the membranematerialsmay provide benefits such as the reduction in consumption of precious materials, the overall stability and dispersibility, a controlled release of drugs inside the core, the surface modification with functional groups, and so on. The delivery formulations with MC nanostructure are summarized in Table 1, and selected recent examples are discussed below based on the material components.
2.膜核纳米结构制剂
MC NP通常被表征为包含内核和外膜的混合纳米结构系统，可以促进具有独特物理，化学和生物学特性的材料的组合（图1）。这种有序的组装纳米结构是通过内芯和外膜之间的化学键和/或物理相互作用形成的。 MC NPs的种类，性质和合成方法已在其他地方进行了综述[4]。与具有单一功能的NP相比，MC NP开启了设计广泛的多功能NP的潜力，这些多功能NP被广泛认为对生物医学应用有利。从药物输送的角度来看，核心材料可以有效地包裹治疗性货物，而膜材料可以提供诸如减少贵重材料消耗，整体稳定性和分散性，药物在核心内的受控释放，具有功能性的表面修饰等优点。小组等等。表1总结了具有MC纳米结构的输送配方，下面根据材料成分讨论了所选的最新实例。
Fig. 1. Delivery strategies designed using membrane-core (MC) nanostructures to overcome the barriers for clinical translation. (A) The formulation of MC nanoparticles (NPs) are generally described as a hybrid nanostructured system comprising organic, inorganic, and biological materials. Following the ordered assembly process, MC NPs commonly demonstrate hybrid nanostructures. Physicochemical factors such as particle size, surface charge and stability are controllable during the formulation in order to facilitate delivery of MC NPs. (B) The combination of materials with distinct properties in MC NPs facilitates the design of multifunctional delivery systems. The surface functionalization furthers the potential of MC NPs as ‘smart’ drug delivery carriers for physiological stability, stimuli-responsive activity, cell- and tissue-targeted delivery, and controlled release. (C) Due to the complexity of cancer such as the metastasis, resistance to certain drugs and genetic diversity, the use of more than one treatment modality is considered a hallmark of cancer therapy. The co-formulation of distinct therapeutic components may be achieved using MC NPs. (D) Barriers to the clinical translation such as instability in the blood circulation, low tumor distribution, immunosuppressive tumor microenvironment, nanotoxicity and manufacture control may be potentially overcome by design of “smart” MC NPs.
图1.使用膜芯（MC）纳米结构设计的递送策略克服了临床翻译的障碍。 （A）MC纳米颗粒（NPs）的配方通常描述为包含有机，无机和生物材料的混合纳米结构系统。按照有序的组装过程，MC NP通常表现出杂化纳米结构。在配制过程中，可控制诸如粒径，表面电荷和稳定性等理化因素，以利于MC NP的递送。 （B）MC NP中具有不同特性的材料的组合有助于多功能输送系统的设计。表面功能化进一步提高了MC NP作为“智能”药物传递载体的潜力，具有生理稳定性，刺激响应活性，细胞和组织靶向传递以及控制释放。 （C）由于癌症的复杂性，例如转移，对某些药物的耐药性和遗传多样性，使用多种治疗方法被认为是癌症治疗的标志。可以使用MC NP实现不同治疗成分的共同配方。 （D）通过设计“智能” MC NP可以潜在地克服临床翻译的障碍，例如血液循环不稳定，肿瘤分布低，免疫抑制性肿瘤微环境，纳米毒性和生产控制。
A. membrane-core formulation
1 materials
organic materials（e.g. lipids，polymers）
inorganic materials (e.g. Au, Fe,Si)
biomimetic carriers
2 hybrid sructures
organic/organic MC NPs
organic/Inorganic MC NPs
Inorganic/organic MC NPs
Inorganic/Inorganic MC NPs
3 Physicochemical factors
size
charge
stability
2.1. Lipids Lipid-based NPs are generally constructed by a combination of cationic, neutral and/or anionic lipids, polyethylene glycol (PEG)-conjugated lipids, and lipopolymers [41]. Liposomeswith a particle size of ~50 to 200 nmare the classic example of lipid-based NPs, and they are generally characterized as vesicleswith one lipid bilayer enclosing an aqueous space. Hydrophobic and hydrophilic drugs may be encapsulated into lipid membrane and aqueous core, respectively, formingMC nanostructures (Fig. 2A). The evolution of liposomal NPs including the formulation approaches, solubility/bioavailability of drugs, and in vitro/ in vivo delivery efficacy, has been extensively reviewed [42] [43] [44] [45]. In addition, nanoscale colloidal carriers made up of solid lipids (high melting fat matrix) namely solid lipid NPs (SLNs) have recently emerged as the new generation of lipid-based nanocarriers [46]. SLNs are usually fabricated by physiologically related lipids, which form a wax or solid core that is stabilized by surfactants (emulsifiers). Hydrophobic components can be dissolved or dispersed inside the core achieving MC nanostructures (Fig. 2B and C). SLNs provide favorable properties such as high drug loading, stability in nanometer size, and controlled/sustained release of cargos [47] [48], demonstrating great potential as a substitute of liposomes for drug delivery [49] [50] [51] [52].
2.1。脂质基于脂质的NP通常由阳离子，中性和/或阴离子脂质，聚乙二醇（PEG）缀合的脂质和脂聚合物组成[41]。约50至200 nm粒径的脂质体是基于脂质的NPs的经典实例，它们通常被表征为具有一层脂质双分子层的脂质体，该脂质双分子层包裹着水性空间。疏水和亲水药物可以分别封装在脂质膜和水核中，形成MC纳米结构（图2A）。脂质体NP的进化包括制剂方法，药物的溶解度/生物利用度以及体外/体内递送功效，已得到广泛的综述[42] [43] [44] [45]。另外，由固态脂质（高熔点脂肪基质）组成的纳米级胶体载体，即固态脂质NP（SLN），最近已作为新一代基于脂质的纳米载体出现[46]。 SLN通常由生理相关的脂质制造，这些脂质形成蜡或固体核，并通过表面活性剂（乳化剂）稳定。疏水成分可以溶解或分散在内核内部，从而获得MC纳米结构（图2B和C）。SLN具有良好的特性，例如高载药量，纳米尺寸的稳定性以及货物的受控/持续释放[47] [48]，证明其具有替代脂质体的巨大潜力[49] [50] [51] [ 52]。
In addition, cationic lipids or neutral lipids along with polycation, can condense nucleic acids via electrostatic interaction to form the MC nanostructured complex (lipopolyplex) [53]. For example, a lipidpolycation- DNA (LPD) formulation has been developed by Huang and colleagues for gene delivery. To prepare this formulation DNA was condensed by high molecular weight cationic polymers (e.g. protamine) into an anionic nanosized core, and the resultant corewas coated by cationic lipids/liposomes [e.g. 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP) and cholesterol] and 1,2-distearoyl-sn-glycero-3- phosphoethanolamine-polyethylene glycol (DSPE-PEG) conjugated with aminoethyl anisamide (AEAA, it is used for targeting sigma-1 receptors that are overexpressed on cancer cells [54]), achieving LPD with MC nanostructure (Fig. 2D and E). LPD has remarkably promoted the transfection, steric stabilization, and tumor specificity [55] [56] [57]. Recently, the transfection of plasmids encoded with small antibody-like proteins (termed traps) using LPD has demonstrated great potential for immunotherapy by remodeling the immunosuppressive tumor microenvironment (TME) [55] [56] [57]. For example, an LPD containing lipopolysaccharide (LPS) trap plasmid effectively blocked LPS inside tumors of mice with orthotopic andmetastatic colorectal cancer (CRC), which significantly mitigated tumor growth and livermetastasis [6]. This anticancer effectwas accompaniedwith the activation of immunogenic cells including CD8+ and CD4+ T cells and dendritic cells (DCs) and the reduction of immunosuppressive cells including myeloid-derived suppressor cells (MDSCs), suggesting the importance of LPS blockade to induce immunotherapeutic responses in the gut-liver immune axis (Fig. 2E).
另外，阳离子脂质或中性脂质与聚阳离子一起，可以通过静电相互作用使核酸凝聚，形成MC纳米结构复合物（lipopolyplex）[53]。例如，Huang和同事开发了脂质聚阳离子-DNA（LPD）制剂用于基因递送。为了制备该制剂，将DNA通过高分子量的阳离子聚合物（例如鱼精蛋白）缩合成阴离子纳米尺寸的核，并且将所得的核用阳离子脂质/脂质体[例如脂质体]包被。 1,2-二油酰基-3-三甲基铵丙烷（DOTAP）和胆固醇]和1,2-二硬脂酰基-sn-甘油-3-磷酸乙醇胺-聚乙二醇（DSPE-PEG）与氨乙基茴香酰胺（AEAA）共轭，用于靶向σ在癌细胞中过表达的-1受体[54]，实现了具有MC纳米结构的LPD（图2D和E）。 LPD显着促进了转染，空间稳定和肿瘤特异性[55] [56] [57]。最近，通过重塑免疫抑制性肿瘤微环境（TME）[55] [56] [57]，使用LPD转染小抗体样蛋白（称为陷阱）编码的质粒已显示出巨大的免疫治疗潜力。例如，含有脂多糖（LPS）捕获质粒的LPD可有效阻断患有原位转移性大肠癌（CRC）的小鼠肿瘤内的LPS，从而显着减轻肿瘤的生长和肝转移[6]。这种抗癌作用伴随着包括CD8 +和CD4 + T细胞和树突状细胞（DCs）在内的免疫原性细胞的活化以及包括髓样来源的抑制细胞（MDSCs）在内的免疫抑制细胞的减少，这表明LPS阻断在肠道中诱导免疫治疗反应的重要性。 -肝免疫轴（图2E）。
Fig. 2. Delivery of anticancer agents using lipid-based MC NPs. (A) Liposomal NPs containing CSF1R- and SHP2-inhibitors for enhanced cytotoxicity and phagocytosis of TAMs (Adapted from [17], copyright 2019Wiley). (B) Lipid-based NPs containing platinum derivative and Dihydroartemisinin (DHA, ROS-mediated drug) for synergistic inhibition of colorectal cancer (CRC) when combined with anti-PD-L1 antibody (Adapted from [12], copyright 2019 Nature Publishing Group). (C) Lipid-based NPs containing CSF-1R siRNA to reprogram TAMs for anticancer effects in melanoma (Adapted from [15], copyright 2017 American Chemical Society). (D) Lipid-protamine-DNA (LPD) NPs containing trap plasmids of IL-10 and CXCL12 for immunotherapeutic effects against pancreatic carcinoma (Adapted from [7], copyright 2019 American Chemical Society). (E) LPD NPs containing PD-L1 trap plasmid for synergistic cancer immunotherapy in combinationwith chemotherapy in CRC (Adapted from[6], copyright 2018Wiley). (F) Lipid‑calcium-phosphate (LCP) NPs containing relaxin plasmid to achieve antitumor efficacy in combination with PD-L1 blockage against metastasis in the liver (Adapted from [8], copyright 2019 Nature Publishing Group).
图2.使用基于脂质的MC NP递送抗癌药。 （A）含有CSF1R和SHP2抑制剂的脂质体NP，可增强TAM的细胞毒性和吞噬作用（改编自[17]，版权2019Wiley）。 （B）当与抗PD-L1抗体联合使用时，可协同抑制结直肠癌（CRC）的含铂衍生物和双氢青蒿素（DHA，ROS介导的药物）的脂质基NPs（改编自[12]，版权2019 Nature Publishing Group ）。 （C）包含CSF-1R siRNA的基于脂质的NP，用于重编程TAM，从而在黑色素瘤中发挥抗癌作用（改编自[15]，版权所有2017 American Chemical Society）。 （D）脂蛋白鱼精蛋白-DNA（LPD）NPs，其含有IL-10和CXCL12的捕获质粒，用于针对胰腺癌的免疫治疗作用（改编自[7]，版权2019美国化学学会）。 （E）包含PD-L1陷阱质粒的LPD NP，用于在CRC中协同癌症免疫治疗和化疗（改编自[6]，版权2018Wiley）。 （F）含有松弛素质粒的脂质磷酸钙（LCP）NP，结合PD-L1阻断抗肝转移达到抗肿瘤功效（改编自[8]，版权2019 Nature Publishing Group）。
It has been reported that a calcium phosphate [Ca3(PO4)2] precipitate was produced by the interaction between calcium ions of calcium chloride (CaCl2) and phosphate groups of DNA, and the resultant precipitate significantly enhanced the gene transfection in cultured cells [58]. Although Ca3(PO4)2-based transfection approaches have been used for delivery of nucleic acids, limitations such as uncontrollable precipitation growth, instability and insolubility hinder the in vivo application [59]. A lipid‑calcium-phosphate (LCP) formulation was therefore developed by Huang and colleagues to address these issues. To prepare LCP, two water-in-oil microemulsions containing CaCl2/ nucleic acids and Na2HPO4, respectively, were mixed to form Ca3 (PO4)2 amorphous precipitate in which nucleic acids are entrapped [60]. The Ca3(PO4)2-nucleic acid core was stabilized by 1,2-dioleoylsn- glycero-3-phosphate (DOPA). Subsequently, the stabilized core was coated with DOTAP, cholesterol and DSPE-PEG-AEAA to form LCP with a MC nanostructure [61]. LCP has been applied as a versatile gene delivery construct in a number of cancer mouse models [62] [63] [64]. For example, liver metastasis is often evident when activated hepatic stellate cells (aHSC) form fibrosis in the liver [65]. Recently, it has been reported that relaxin (RLN, a peptide against fibrosis) may deactivate aHSCs for fibrosis resolution in the liver [66]. Thus, LCP was developed to deliver RLN plasmid into cancer cells and aHSCs inside metastatic sites in which the RLN protein was produced (Fig. 2F). As a consequent, the stromal TME was impaired by the RLN protein, significantly suppressing metastatic progression and promoting the animal survival [8].
据报道，氯化钙（CaCl2）的钙离子与DNA磷酸基团之间的相互作用产生了磷酸钙[Ca3（PO4）2]沉淀，所得沉淀显着增强了培养细胞的基因转染[58]。 ]。尽管已经使用基于Ca3（PO4）2的转染方法来递送核酸，但局限性如无法控制的沉淀生长，不稳定性和不溶性阻碍了体内应用[59]。因此，Huang及其同事开发了一种脂质磷酸钙（LCP）制剂来解决这些问题。为了制备LCP，将分别包含CaCl2 /核酸和Na2HPO4的两种油包水微乳混合形成Ca3（PO4）2无定形沉淀物，其中截留了核酸[60]。 Ca 3（PO 4）2-核酸核心通过1，2-二油酰基-n-3-甘油甘油（DOPA）稳定。随后，用DOTAP，胆固醇和DSPE-PEG-AEAA包被稳定的核，形成具有MC纳米结构的LCP [61]。 LCP已被用作多种癌症小鼠模型的通用基因传递构建体[62] [63] [64]。例如，当活化的肝星状细胞（aHSC）在肝脏中形成纤维化时，肝转移通常很明显[65]。最近，有报道说松弛素（RLN，一种抗纤维化的肽）可能使aHSC失活，从而解决肝脏中的纤维化[66]。因此，开发了LCP以将RLN质粒递送到产生RLN蛋白的转移位点内的癌细胞和aHSC中（图2F）。因此，间质TME被RLN蛋白损害，显着抑制转移进程并促进动物存活[8]。
The encapsulation of platinum-based drugs (e.g. cisplatin, carboplatin, and oxaliplatin) into NPs is low due to the insolubility in both aqueous solutions and organic solvents. Recently, LCP-derived NPs have been developed by replacing the Ca3(PO4)2-nucleic acid core with the nanoprecipitate (which encapsulates platinum-based drugs) [67]. For example, a nanoprecipitate Pt(DACH).FnA (C26H35N9O7Pt) was formed by conjugation of [Pt(DACH)(H2O)2]2+ (the active form of oxaliplatin, OxP) and folinic acid [FnA, it can sensitize cancer cells to 5-fluorouracil (5-Fu)] [68]. The DOPA-stabilized nanoprecipitate was coated with DOTAP, cholesterol and DSPE-PEG-AEAA to form a MC NP (namely Nano-Folox). Due to the capacity of OxP to induce immunogenic cell death (ICD, it is able to induce the immune response to activate T lymphocytes for recognizing tumor-specific antigens [69]), Nano-Folox either alone or combined with 5-Fu successfully achieved chemo-immunotherapeutic effects in orthotopic and metastatic CRC mice without toxicity [68].
由于在水溶液和有机溶剂中均不溶，将铂基药物（例如，顺铂，卡铂和奥沙利铂）封装到NP中的程度很低。最近，通过用纳米沉淀物（封装了铂基药物）代替Ca3（PO4）2-核酸核心，已经开发了LCP衍生的NP [67]。例如，纳米沉淀物Pt（DACH）.FnA（C26H35N9O7Pt）是通过[Pt（DACH）（H2O）2] 2+（草酸铂的活性形式，OxP）和亚叶酸[FnA]结合形成的，它可以致癌细胞至5-氟尿嘧啶（5-Fu）] [68]。用DOTAP，胆固醇和DSPE-PEG-AEAA涂覆DOPA稳定的纳米沉淀，以形成MC NP（即Nano-Folox）。由于OxP具有诱导免疫原性细胞死亡的能力（ICD，它能够诱导免疫反应以激活T淋巴细胞以识别肿瘤特异性抗原[69]），单独或与5-Fu组合使用Nano-Folox成功实现了对原位和转移性CRC小鼠的化学免疫治疗作用无毒性[68]。
2.2. Polymers Polymeric materials used for MC NPs mainly include poly(lactic-coglycolic acid) (PLGA) [70] [71], poly(lactic acid) (or polylactide, PLA) [72] [73], Poly(β-amino ester) (PBAE) [74] [75], poly(amino acid) (PAA)/polypeptide [76] [77], polysaccharide (e.g. chitosan, alginate and hyaluronic acid) [78] [79], etc. Recent advances in polymerization approaches have significantly enabled the development of block copolymerswith precise control over the architecture of individual polymeric components and with incorporation of different functions (e.g. responsive moieties, stealth groups, and targeting ligands) [80] [81] [82]. A variety of formulation strategies based on the amphiphilic property of block copolymers, such as the oil-in-water (O/W) single emulsion process (for hydrophobic therapeutic cargos) and the water-in-oil-inwater (W/O/W) double emulsion method (for hydrophilic therapeutic cargos), have been used to formMC nanostructures [83]. Consequently, polymeric MC NPs have significantly improved solubility and bioavailability of drugs, facilitated targeted and controlled drug delivery, and mitigated toxicity and side effects (Table 1).
2.2 聚合物用于MC NP的聚合物材料主要包括聚乳酸-乙醇酸（PLGA）[70] [71]，聚乳酸（或聚乳酸，PLA）[72] [73]，聚（β-氨基酯） ）（PBAE）[74] [75]，聚氨基酸（PAA）/多肽[76] [77]，多糖（例如壳聚糖，藻酸盐和透明质酸）[78] [79]等。聚合方法极大地促进了嵌段共聚物的开发，可以精确控制单个聚合物组分的结构，并引入不同的功能（例如反应性部分，隐形基团和靶向配体）[80] [81] [82]。基于嵌段共聚物的两亲性的各种配制策略，例如水包油（O / W）单乳液工艺（用于疏水性治疗货物）和水包油型水（W / O / W）双重乳液法（用于亲水性治疗货物）已用于形成MC纳米结构[83]。因此，聚合MC NPs显着改善了药物的溶解度和生物利用度，促进了靶向和受控的药物递送，并减轻了毒性和副作用（表1）。
PLGA as a copolymer of lactic and glycolic acids (Fig. 3A and B) is one of the best-defined polymeric drug delivery carriers with respective to its biocompatible/biodegradable property, controllable release capability, and surface functionalization [84]. For example, the production of perivascular nitric oxide (NO) gradients may normalize tumor vessels, which can improve tumor response to anticancer agents [85]. However, a strategy for prolonged half-life, sustained release and targeted delivery of NO is currently lacking. Recently, a PLGA nanocarrier containing NO was developed to address these issues [86]. In this study, the dinitrosyl iron complex (DNIC, the NO donor) was encapsulated inside PLGA through the O/W single emulsion, and the surface of PLGA-DNIC core was stabilized with PEG. The resultant MC NP (termed NanoNO) could improve blood circulation by avoiding recognition of monocytes and macrophages and by preventing interaction of serum proteins. NanoNO demonstrated tumor accumulation, and subsequently provided the controlled and sustained release of NO from DNIC. Consequently, NanoNO at low-doses normalized tumor vessels and improved the efficacy of doxorubicin (DOX) in primary hepatocellular carcinoma (HCC) tumor and metastasis [86].
PLGA作为乳酸和乙醇酸的共聚物（图3A和B）是定义最明确的聚合物药物递送载体之一，其生物相容性/可生物降解性，可控释放能力和表面官能化特性[84]。例如，血管周围一氧化氮（NO）梯度的产生可以使肿瘤血管正常化，从而可以改善肿瘤对抗癌药的反应[85]。然而，目前缺乏延长NO的半衰期，持续释放和靶向递送的策略。最近，开发了一种不含NO的PLGA纳米载体来解决这些问题[86]。在这项研究中，二亚硝基铁络合物（DNIC，NO供体）通过O / W单乳液被包裹在PLGA内部，并且PLGA-DNIC核的表面被PEG稳定。所得的MC NP（称为NanoNO）可通过避免单核细胞和巨噬细胞的识别以及防止血清蛋白的相互作用来改善血液循环。 NanoNO证明了肿瘤的蓄积，随后提供了从DNIC中可控和持续释放的NO。因此，低剂量的NanoNO使肿瘤血管正常化，并提高了阿霉素（DOX）在原发性肝细胞癌（HCC）肿瘤和转移中的疗效[86]。
A PLGA NP was produced through W/O/W double emulsion to coencapsulate catalase (Cat; it is a hydrophilic enzyme that can mediate the decomposition of H2O2 to generate oxygen) inside the aqueous core and imiquimod (R837; it is a water-insoluble Toll-like receptor (TLR)-7 agonist as an immune adjuvant) into the PLGA shell [87]. The resulting co-formulation (termed PLGA-Cat/R837) could tremendously enhance radiotherapeutic efficacy via reducing the hypoxia and remodeling the immunosuppressive TME (Fig. 3A). Consequently, PLGA-Cat/ R837 induced favorable immunotherapeutic effects when combined with cytotoxic T lymphocyte-associated protein 4 (CTLA-4) blockade, resulting in significantly stronger antitumor effect in breast tumor metastasis model [87].
通过W / O / W双重乳液生产PLGA NP，以在水核心和咪喹莫特（R837；它是水不溶性的）内部共包裹过氧化氢酶（Cat；这是一种亲水性酶，可以介导H2O2的分解产生氧气）。 Toll样受体（TLR）-7激动剂作为免疫佐剂进入PLGA壳中[87]。 最终的共制剂（称为PLGA-Cat / R837）可以通过减少缺氧和重塑免疫抑制性TME来极大地增强放射治疗的功效（图3A）。 因此，当PLGA-Cat / R837与细胞毒性T淋巴细胞相关蛋白4（CTLA-4）阻断剂结合使用时，具有良好的免疫治疗效果，从而在乳腺癌转移模型中显着增强了抗肿瘤作用[87]。
An AEAA-targeted PEGylated PLGA NP (PLGA-PEG-AEAA) was produced for co-delivery of DOX and icaritin (ICT) to HCC [88]. In this study, ICT induced mitophagy and apoptosis in HCC cells, which improved DOX-mediated ICD effects. A MC nanostructure was achieved when DOX and ICT were co-encapsulated in the hydrophobic core of PLGA-PEG-AEAA via a solvent displacement process. The coformulation demonstrated pH-sensitive drug release and enhanced blood circulation and tumor accumulation of drugs. As a result, the coformulationwas able to remodel the immunosuppressive TME and trigger a robust immune response, achieving satisfactory anti-HCC effect in an orthotopic HCC mouse model [88].
制备了以AEAA为目标的聚乙二醇化PLGA NP（PLGA-PEG-AEAA），用于将DOX和icaritin（ICT）共递送至HCC [88]。 在这项研究中，ICT诱导了HCC细胞的线粒体和细胞凋亡，从而改善了DOX介导的ICD效应。 当通过溶剂置换过程将DOX和ICT共包裹在PLGA-PEG-AEAA的疏水核中时，获得了MC纳米结构。 共制剂证明了pH敏感药物的释放以及血液循环和药物肿瘤积累的增强。 结果，共制剂能够重塑免疫抑制性TME并触发强大的免疫反应，从而在原位HCC小鼠模型中获得令人满意的抗HCC效果[88]。
In addition to PLGA, a variety of polymeric materials have also been employed for design ofMC NPs (Fig. 3C, D, E and F). For example, a poly (β-amino ester)-based NP with PEGylated AEAA was produced for coencapsulation of mitoxantrone (an ICD inducer) and celastrol (a pentacyclic triterpene compound) to animals with desmoplastic melanoma mice (Fig. 3C). The nanoformulation significantly triggered immunotherapeutic responses, reprogrammed the immunosuppressive microenvironments, and promoted the animal survival [25]. In addition, a nanoemulsion was produced using D-α-tocopherol polyethylene glycol succinate (TPGS) and DSPE-PEG by the ethanol injectionmethod for co-encapsulation of quercetin and alantolactone (Fig. 3E). The nanoemulsion with two drugs at the optimal ratio was capable of activating ICD-mediated antitumor immunity and modulating the immunosuppressive TME in CRC mice [89]. This simple and safe nanoemulsion therefore demonstrates great promise for clinical application for CRC.
除PLGA外，各种聚合物材料也已用于设计MC NP（图3C，D，E和F）。例如，制备了具有聚乙二醇化EAEA的基于聚（β-氨基酯）的NP，用于将米托蒽醌（ICD诱导剂）和Celastrol（五环三萜化合物）共包封到患有增塑性黑素瘤小鼠的动物中（图3C）。纳米制剂显着触发了免疫治疗反应，对免疫抑制性微环境进行了重新编程，并促进了动物的存活[25]。另外，使用D-α-生育酚聚乙二醇琥珀酸酯（TPGS）和DSPE-PEG通过乙醇注射方法共包封槲皮素和丙二酸内酯制备了纳米乳液（图3E）。以两种最佳比例配伍的纳米乳剂能够激活ICD介导的抗肿瘤免疫力并调节CRC小鼠的免疫抑制TME [89]。因此，这种简单且安全的纳米乳剂在CRC的临床应用中显示出了广阔的前景。