Membrane Permeability and Responsiveness Drive Performance: Linking Structural Features with the Antitumor Effectiveness of Doxorubicin-Loaded Stimuli-Triggered Polymersomes.

The permeability and responsiveness of polymer membranes are absolutely relevant in the design of polymersomes for cargo delivery. Accordingly, we herein correlate the structural features, permeability, and responsiveness of doxorubicin-loaded (DOX-loaded) nonresponsive and stimuli-responsive polymersomes with their in vitro and in vivo antitumor performance. Polymer vesicles were produced using amphiphilic block copolymers containing a hydrophilic poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) segment linked to poly[N-(4-isopropylphenylacetamide)ethyl methacrylate] (PPPhA, nonresponsive block), poly[4-(4,4,5,5-tetra-methyl-1,3,2-dioxaborolan-2-yl)benzyl methacrylate] [PbAPE, reactive oxygen species (ROS)-responsive block], or poly[2-(diisopropylamino)ethyl methacrylate] (PDPA, pH-responsive block). The PDPA-based polymersomes demonstrated outstanding biological performance with antitumor activity notably enhanced compared to their counterparts. We attribute this behavior to a fast-triggered DOX release in acidic tumor environments as induced by pH-responsive polymersome disassembly at pH < 6.8. Possibly, an insufficient ROS concentration in the selected tumor model attenuates the rate of ROS-responsive vesicle degradation, whereas the nonresponsive nature of the PPPhA block remarkably impacts the performance of such potential nanomedicines.

Role of Membrane Features on the Permeability Behavior of Polymersomes and the Potential Impacts on Drug Encapsulation and Release.

Self-assembled bilayer structures such as those produced from amphiphilic block copolymers (polymersomes) are potentially useful in a wide array of applications including the production of artificial cells and organelles, nanoreactors, and delivery systems. These constructs are of important fundamental interest, and they are also frequently considered toward advances in bionanotechnology and nanomedicine. In this framework, membrane permeability is perhaps the most important property of such functional materials. Having in mind these considerations, we herein report the manufacturing of intrinsically permeable polymersomes produced using block copolymers comprising poly[2-(diisopropylamino)-ethyl methacrylate] (PDPA) as the hydrophobic segment. Although being water insoluble at pH 7.4, its pKa(PDPA) ∼ 6.8 leads to the presence of a fraction of protonated amino groups close to the physiological pH, thus conducting the formation of relatively swollen hydrophobic segments. Rhodamine B-loaded vesicles demonstrated that this feature confers inherent permeability to the polymeric membrane, which can still be modulated to some extent by the solution pH. Indeed, even at higher pH values where the PDPA chains are fully deprotonated, the experiments demonstrate that the membranes remain permeable. While membrane permeability can be, for instance, regulated by introducing membrane proteins and DNA nanopores, examples of membrane-forming polymers with intrinsic permeability have been seldom reported so far, and the possibility to regulate the flow of chemicals in these compartments by tuning block copolymer features and ambient conditions is of due relevance. The permeable nature of PDPA membranes possibly applies to a wide array of small molecules, and these findings can in principle be translocated to a variety of disparate bio-related applications.

Reactive Oxygen Species (ROS)-Responsive Polymersomes with Site-Specific Chemotherapeutic Delivery into Tumors via Spacer Design Chemistry.

The lack of cellular and tissue specificities in conventional chemotherapies along with the generation of a complex tumor microenvironment (TME) limits the dosage of active agents that reaches tumor sites, thereby resulting in ineffective responses and side effects. Therefore, the development of selective TME-responsive nanomedicines is of due relevance toward successful chemotherapies, albeit challenging. In this framework, we have synthesized novel, ready-to-use ROS-responsive amphiphilic block copolymers (BCs) with two different spacer chemistry designs to connect a hydrophobic boronic ester-based ROS sensor to the polymer backbone. Hydrodynamic flow focusing nanoprecipitation microfluidics (MF) was used in the preparation of well-defined ROS-responsive PSs; these were further characterized by a combination of techniques [1H NMR, dynamic light scattering (DLS), static light scattering (SLS), transmission electron microscopy (TEM), and cryogenic TEM (cryo-TEM)]. The reaction with hydrogen peroxide releases an amphiphilic phenol or a hydrophilic carboxylic acid, which affects polymersome (PS) stability and cargo release. Therefore, the importance of the spacer chemistry in BC deprotection and PS stability and cargo release is herein highlighted. We have also evaluated the impact of spacer chemistry on the PS-specific release of the chemotherapeutic drug doxorubicin (DOX) into tumors in vitro and in vivo. We demonstrate that by spacer chemistry design one can enhance the efficacy of DOX treatments (decrease in tumor growth and prolonged animal survival) in mice bearing EL4 T cell lymphoma. Side effects (weight loss and cardiotoxicity) were also reduced compared to free DOX administration, highlighting the potential of the well-defined ROS-responsive PSs as TME-selective nanomedicines. The PSs could also find applications in other environments with high ROS levels, such as chronic inflammations, aging, diabetes, cardiovascular diseases, and obesity.

Microfluidic-Assisted Engineering of Quasi-Monodisperse pH-Responsive Polymersomes toward Advanced Platforms for the Intracellular Delivery of Hydrophilic Therapeutics.

The extracellular and subcellular compartments are characterized by specific pH levels that can be modified by pathophysiological states. This scenario encourages the use of environmentally responsive nanomedicines for the treatment of damaged cells. We have engineered doxorubicin (DOX)-loaded pH-responsive polymersomes using poly([ N-(2-hydroxypropyl)]methacrylamide)- b-poly[2-(diisopropylamino)ethyl methacrylate] block copolymers (PHPMA m- b-PDPA n). We demonstrate that, by taking advantage of the microfluidic technology, quasi-monodisperse assemblies can be created. This feature is of due relevance because highly uniform nanoparticles commonly exhibit more consistent biodistribution and cellular uptake. We also report that the size of the polymer vesicles can be tuned by playing with the inherent mechanical parameters of the microfluidic protocol. This new knowledge can be used to engineer size-specific nanomedicines for enhanced tumor accumulation if the manufacturing is performed with previous knowledge of tumor characteristics (particularly the degree of vascularity and porosity). The pH-dependent DOX release was further investigated evidencing the ability of polymersome to sustain encapsulated hydrophilic molecules when circulating in physiological environment (pH 7.4). This suggests nonrelevant drug leakage during systemic circulation. On the other hand, polymersome disassembly in slightly acid environments takes place enabling fast DOX release, thereby making the colloidal carriers highly cytotoxic. These features encourage the use of such advanced pH-responsive platforms to target damaged cells while preserving healthy environments during systemic circulation.

Effect of polymer concentration on the morphology of the PHPMAA-g-PLA graft copolymer nanoparticles produced by microfluidics nanoprecipitation.

Successful generation of micelles, vesicles, and/or worms with controllable sizes was achieved through the self-assembly process of the poly[N-(2-hydroxypropyl)]methacrylamide-g-polylactide (PHPMAA-g-PLA) graft copolymer within a microfluidic channel. A product diagram was created to illustrate various morphologies associated with different polymer concentrations, all while maintaining a constant flow velocity ratio between water and the polymer solution.

Tuning the morphology of block copolymer-based pH-triggered nanoplatforms as driven by changes in molecular weight and protocol of manufacturing.

The ability to tune size and morphology of self-assemblies is particularly relevant in the development of delivery systems. By tailoring such structural parameters, one can provide larger cargo spaces or produce nanocarriers that can be loaded by hydrophilic and hydrophobic molecules starting ideally from the same polymer building unit. We herein demonstrate that the morphology of block copolymer-based pH-triggered nanoplatforms produced from poly(2-methyl-2-oxazoline)m-b-poly[2-(diisopropylamino)-ethyl methacrylate]n (PMeOxm-b-PDPAn) is remarkably influenced by the overall molecular weight of the block copolymer, and by the selected method used to produce the self-assemblies. Polymeric vesicles were produced by nanoprecipitation using a block copolymer of relatively low molecular weight (Mn âˆ¼ 10 kg.mol-1). Very exciting though, despite the high hydrophobic weight ratio (wPDPA > 0.70), this method conducted to the formation of core-shell nanoparticles when block copolymers of higher molecular weight were used, thus suggesting that the fast (few seconds) self-assembly procedure is controlled by kinetics rather than thermodynamics. We further demonstrated the formation of vesicular structures using longer chains via the solvent-switch approach when the "switching" to the bad solvent is performed in a time scale of a few hours (approximately 3 hs). We accordingly demonstrate that using fairly simple methods one can easily tailor the morphology of such block copolymer self-assemblies, thereby producing a variety of structurally different pH-triggered nanoplatforms via a kinetic or thermodynamically-controlled process. This is certainly attractive towards the development of nanotechnology-based cargo delivery systems.

Microwave Irradiation-Assisted Reversible Addition-Fragmentation Chain Transfer Polymerization-Induced Self-Assembly of pH-Responsive Diblock Copolymer Nanoparticles.

Herein, we present a versatile platform for the synthesis of pH-responsive poly([N-(2-hydroxypropyl)]methacrylamide)-b-poly[2-(diisopropylamino)ethyl methacrylate] diblock copolymer (PHPMA-b-PDPA) nanoparticles (NPs) obtained via microwave-assisted reversible addition-fragmentation chain transfer polymerization-induced self-assembly (MWI-PISA). The N-(2-hydroxypropyl) methacrylamide (HPMA) monomer was first polymerized to obtain a macrochain transfer agent with polymerization degrees (DPs) of 23 and 51. Subsequently, using mCTA and 2-(diisopropylamino)ethyl methacrylate (DPA) as monomers, we successfully conducted MWI-PISA emulsion polymerization in aqueous solution with a solid content of 10 wt %. The NPs were obtained with high monomer conversion and polymerization rates. The resulting diblock copolymer NPs were analyzed by dynamic light scattering (DLS) and cryogenic-transmission electron microscopy (cryo-TEM). cryo-TEM studies reveal the presence of only NPs with spherical morphology such as micelles and polymer vesicles known as polymersomes. Under the selected conditions, we were able to fine-tune the morphology from micelles to polymersomes, which may attract considerable attention in the drug-delivery field. The capability for drug encapsulation using the obtained in situ pH-responsive NPs, the polymersomes based on PHPMA23-b-PDPA100, and the micelles based on PHPMA51-b-PDPA100 was demonstrated using the hydrophobic agent and fluorescent dye as Nile red (NR). In addition, the NP disassembly in slightly acidic environments enables fast NR release.

Industrial Scale Manufacturing and Downstream Processing of PLGA-Based Nanomedicines Suitable for Fully Continuous Operation.

Despite the efficacy and potential therapeutic benefits that poly(lactic-co-glycolic acid) (PLGA) nanomedicine formulations can offer, challenges related to large-scale processing hamper their clinical and commercial development. Major hurdles for the launch of a polymeric nanocarrier product on the market are batch-to-batch variations and lack of product consistency in scale-up manufacturing. Therefore, a scalable and robust manufacturing technique that allows for the transfer of nanomedicine production from the benchtop to an industrial scale is highly desirable. Downstream processes for purification, concentration, and storage of the nanomedicine formulations are equally indispensable. Here, we develop an inline sonication process for the production of polymeric PLGA nanomedicines at the industrial scale. The process and formulation parameters are optimized to obtain PLGA nanoparticles with a mean diameter of 150 ± 50 nm and a small polydispersity index (PDI < 0.2). Downstream processes based on tangential flow filtration (TFF) technology and lyophilization for the washing, concentration, and storage of formulations are also established and discussed. Using the developed manufacturing and downstream processing technologies, production of two PLGA nanoformulations encasing ritonavir and celecoxib was achieved at 84 g/h rate. As a measure of actual drug content, encapsulation efficiencies of 49.5 ± 3.2% and 80.3 ± 0.9% were achieved for ritonavir and celecoxib, respectively. When operated in-series, inline sonication and TFF can be adapted for fully continuous, industrial-scale processing of PLGA-based nanomedicines.

Translating the Manufacture of Immunotherapeutic PLGA Nanoparticles from Lab to Industrial Scale: Process Transfer and In Vitro Testing.

Poly(lactic-co-glycolic acid) (PLGA) nanoparticle-based drug delivery systems are known to offer a plethora of potential therapeutic benefits. However, challenges related to large-scale manufacturing, such as the difficulty of reproducing complex formulations and high manufacturing costs, hinder their clinical and commercial development. In this context, a reliable manufacturing technique suitable for the scale-up production of nanoformulations without altering efficacy and safety profiles is highly needed. In this paper, we develop an inline sonication process and adapt it to the industrial scale production of immunomodulating PLGA nanovaccines developed using a batch sonication method at the laboratory scale. The investigated formulations contain three distinct synthetic peptides derived from the carcinogenic antigen New York Esophageal Squamous Cell Carcinoma-1 (NY-ESO-1) together with an invariant natural killer T-cell (iNKT) activator, threitolceramide-6 (IMM60). Process parameters were optimized to obtain polymeric nanovaccine formulations with a mean diameter of 150 ± 50 nm and a polydispersity index <0.2. Formulation characteristics, including encapsulation efficiencies, release profiles and in vitro functional and toxicological profiles, are assessed and statistically compared for each formulation. Overall, scale-up formulations obtained by inline sonication method could replicate the colloidal and functional properties of the nanovaccines developed using batch sonication at the laboratory scale. Both types of formulations induced specific T-cell and iNKT cell responses in vitro without any toxicity, highlighting the suitability of the inline sonication method for the continuous scale-up of nanomedicine formulations in terms of efficacy and safety.

pH-responsive polymersome-mediated delivery of doxorubicin into tumor sites enhances the therapeutic efficacy and reduces cardiotoxic effects.

The delivery of therapeutics into sites of action by using cargo-delivery platforms potentially minimizes their premature degradation and fast clearance from the bloodstream. Additionally, drug-loaded stimuli-responsive supramolecular assemblies can be produced to respond to the inherent features of tumor microenvironments, such as extracellular acidosis. We report in this framework the use of pH-responsive polymersomes (PSs) manufactured using poly([N-(2-hydroxypropyl)] methacrylamide)35-b-poly[2-(diisopropylamino)ethyl methacrylate]75 as the building unit (PHPMA35-b-PDPA75). The self-assemblies were produced with desired size towards long circulation time and tumor accumulation (hydrodynamic diameter - DH ~ 100 nm), and they could be successfully loaded with 10% w/w DOX (doxorubicin), while maintaining colloidal stability. The DOX loaded amount is presumably mainly burst-released at the acidic microenvironment of tumors thanks to the pH-switchable property of PDPA (pKa ~ 6.8), while reduced drug leakage has been monitored in pH 7.4. Compared to the administration of free DOX, the drug-loaded supramolecular structures greatly enhanced the therapeutic efficacy with effective growth inhibition of EL4 lymphoma tumor model and 100% survival rate in female C57BL/6 black mice over 40 days. The approach also led to reduced cardiotoxic effect. These features highlight the potential application of such nanotechnology-based treatment in a variety of cancer therapies where low local pH is commonly found, and emphasize PHPMA-based nanomedicines as an alternative to PEGylated formulations.

Paclitaxel-loaded biodegradable ROS-sensitive nanoparticles for cancer therapy.

BACKGROUND: Reactive oxygen species (ROS), such as hydrogen peroxide and superoxide, trigger biodegradation of polymer-based nanoparticles (NPs) bearing pinacol-type boronic ester groups. These NPs may selectively release their cargo, in this case paclitaxel (PTX), at the high levels of ROS present in the intracellular environment of inflamed tissues and most tumors. PURPOSE: The main objective was to determine anti-tumor efficacy of PTX-loaded ROS-sensitive NPs and to examine whether macrophage infiltration had any impact on treatment efficacy. METHODS: NPs were synthesized and their characteristics in the presence of H2O2 were demonstrated. Both confocal microscopy as well as flow cytometry approaches were used to determine degradation of ROS-sensitive NPs. HeLa cells were cultured in vitro and used to establish tumor xenografts in nude mice. In vivo experiments were performed to understand toxicity, biodistribution and anti-tumor efficacy of the NPs. Moreover, we performed immunohistochemistry on tumor sections to study infiltration of M1 and M2 subsets of macrophages. RESULTS: We demonstrated that PTX delivered in NPs containing a ROS-sensitive polymer exhibits a better anti-tumor efficacy than PTX in NPs containing ROS-non-sensitive polymer, free PTX or Abraxane® (nab-PTX). The biodistribution revealed that ROS-sensitive NPs exhibit retention in liver, spleen and lungs, suggesting a potential to target cancer metastasizing to these organs. Finally, we demonstrated a correlation between infiltrated macrophage subsets and treatment efficacy, possibly contributing to the efficient anti-tumor effects. CONCLUSION: Treatment with ROS-sensitive NPs containing PTX gave an improved therapeutic effect in HeLa xenografts than their counterpart, free PTX or nab-PTX. Our data revealed a correlation between macrophage infiltration and efficiency of the different antitumor treatments, as the most effective NPs resulted in the highest infiltration of the anti-tumorigenic M1 macrophages.