Introduction

Nucleic acids have gained recognition as promising immunomodulatory therapeutics. However, their potential is limited by several drug delivery barriers, and there is a need for technologies that enhance intracellular delivery of nucleic acid drugs. Furthermore, controlled and sustained release is a significant concern, as the kinetics and localization of immunomodulators can influence resultant immune responses. Here, we describe the design and initial evaluation of poly(lactic-co-glycolic) acid (PLGA) microparticle (MP) depots for enhanced retention and sustained release of endosomolytic nanoparticles that enable the cytosolic delivery of nucleic acids.

Methods

Endosomolytic p[DMAEMA]_10kD-bl-[PAA_0.3-co-DMAEMA_0.3-co-BMA_0.4]_25kD diblock copolymers were synthesized by reversible addition-fragmentation chain transfer polymerization. Polymers were electrostatically complexed with nucleic acids and resultant nanoparticles (NPs) were encapsulated in PLGA MPs. To modulate release kinetics, ammonium bicarbonate was added as a porogen. Release profiles were quantified in vitro and in vivovia quantification of fluorescently-labeled nucleic acid. Bioactivity of released NPs was assessed using small interfering RNA (siRNA) targeting luciferase as a representative nucleic acid cargo. MPs were incubated with luciferase-expressing 4T1 (4T1-LUC) breast cancer cells in vitro or administered intratumorally to 4T1-LUC breast tumors, and silencing via RNA interference was quantified via longitudinal luminescence imaging.

Results

Endosomolytic NPs complexed to siRNA were effectively loaded into PLGA MPs and release kinetics could be modulated in vitro and in vivovia control of MP porosity, with porous MPs exhibiting faster cargo release. In vitro, release of NPs from porous MP depots enabled sustained luciferase knockdown in 4T1 breast cancer cells over a five-day treatment period. Administered intratumorally, MPs prolonged the retention of nucleic acid within the injected tumor, resulting in enhanced and sustained silencing of luciferase relative to a single bolus administration of NPs at an equivalent dose.

Conclusion

This work highlights the potential of PLGA MP depots as a platform for local release of endosomolytic polymer NPs that enhance the cytosolic delivery of nucleic acid therapeutics.

中文翻译：

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用于内溶性纳米颗粒的控制和持续释放的微粒库。

介绍

核酸已被公认为有前景的免疫调节疗法。然而，它们的潜力受到几个药物递送障碍的限制，因此需要增强核酸药物在细胞内递送的技术。此外，受控和持续释放是一个重要问题，因为免疫调节剂的动力学和定位会影响产生的免疫反应。在这里，我们描述了聚乳酸-乙醇酸 (PLGA) 微粒 (MP) 贮库的设计和初步评估，以增强内溶性纳米粒子的保留和持续释放，从而实现核酸的细胞溶质递送。

方法

通过可逆加成-断裂链转移聚合合成了内涵体溶解p [DMAEMA] _10kD - bl -[PAA _0.3 - co -DMAEMA _0.3 - co -BMA _0.4 ] _{25kD二嵌段共聚物。}聚合物与核酸进行静电复合，并将所得纳米颗粒 (NP) 封装在 PLGA MP 中。为了调节释放动力学，添加碳酸氢铵作为致孔剂。通过体外和体内量化释放曲线定量荧光标记的核酸。使用靶向荧光素酶的小干扰 RNA (siRNA) 作为代表性核酸货物评估释放的 NPs 的生物活性。MPs在体外与表达荧光素酶的 4T1 (4T1-LUC) 乳腺癌细胞一起孵育或在瘤内对 4T1-LUC 乳腺癌细胞进行孵育，并通过纵向发光成像对通过RNA 干扰的沉默进行量化。

结果

与 siRNA 复合的内溶 NPs 被有效地加载到 PLGA MPs 中，并且可以通过控制 MP 孔隙率在体外和体内调节释放动力学，多孔 MPs 表现出更快的货物释放。在体外，从多孔 MP 库释放 NP 可以在 5 天的治疗期内持续抑制 4T1 乳腺癌细胞中的荧光素酶。在瘤内给药时，MPs 延长了核酸在注射肿瘤内的保留时间，与单次推注等效剂量的 NPs 相比，导致荧光素酶的增强和持续沉默。

结论

这项工作突出了 PLGA MP 储存库作为局部释放内体溶解聚合物 NP 的平台的潜力，从而增强了核酸治疗剂的细胞溶质递送。