Facile Generation of Heterotelechelic Poly(2-Oxazoline)s Towards Accelerated Exploration of Poly(2-Oxazoline)-Based Nanomedicine.

Controlling the end-groups of biocompatible polymers is crucial for enabling polymer-based therapeutics and nanomedicine. Typically, end-group diversification is a challenging and time-consuming endeavor, especially for polymers prepared via ionic polymerization mechanisms with limited functional group tolerance. In this study, we present a facile end-group diversification approach for poly(2-oxazoline)s (POx), enabling quick and reliable production of heterotelechelic polymers to facilitate POxylation. The approach relies on the careful tuning of reaction parameters to establish differential reactivity of a pentafluorobenzyl initiator fragment and the living oxazolinium chain-end, allowing the selective introduction of N-, S-, O-nucleophiles via the termination of the polymerization, and a consecutive nucleophilic para-fluoro substitution. The value of this approach for the accelerated development of nanomedicine is demonstrated through the synthesis of well-defined lipid-polymer conjugates and POx-polypeptide block-copolymers, which are well-suited for drug and gene delivery. Furthermore, we investigated the application of a lipid-POx conjugate for the formulation and delivery of mRNA-loaded lipid nanoparticles for immunization against the SARS-COV-2 virus, underscoring the value of POx as a biocompatible polymer platform.

Targeting nanoparticles to the brain by exploiting the blood-brain barrier impermeability to selectively label the brain endothelium.

Current strategies to direct therapy-loaded nanoparticles to the brain rely on functionalizing nanoparticles with ligands which bind target proteins associated with the blood-brain barrier (BBB). However, such strategies have significant brain-specificity limitations, as target proteins are not exclusively expressed at the brain microvasculature. Therefore, novel strategies which exploit alternative characteristics of the BBB are required to overcome nonspecific nanoparticle targeting to the periphery, thereby increasing drug efficacy and reducing detrimental peripheral side effects. Here, we present a simple, yet counterintuitive, brain-targeting strategy which exploits the higher impermeability of the BBB to selectively label the brain endothelium. This is achieved by harnessing the lower endocytic rate of brain endothelial cells (a key feature of the high BBB impermeability) to promote selective retention of free, unconjugated protein-binding ligands on the surface of brain endothelial cells compared to peripheral endothelial cells. Nanoparticles capable of efficiently binding to the displayed ligands (i.e., labeled endothelium) are consequently targeted specifically to the brain microvasculature with minimal "off-target" accumulation in peripheral organs. This approach therefore revolutionizes brain-targeting strategies by implementing a two-step targeting method which exploits the physiology of the BBB to generate the required brain specificity for nanoparticle delivery, paving the way to overcome targeting limitations and achieve clinical translation of neurological therapies. In addition, this work demonstrates that protein targets for brain delivery may be identified based not on differential tissue expression, but on differential endocytic rates between the brain and periphery.

Dynamic Stabilization of Unit Polyion Complexes Incorporating Small Interfering RNA by Fine-Tuning of Cationic Block Length in Two-Branched Poly(ethylene glycol)-b-poly(l-lysine).

To stabilize small interfering RNA (siRNA) in the bloodstream for systemic RNAi therapeutics, we previously fabricated ultrasmall siRNA nanocarriers that were sub-20 nm in hydrodynamic diameter, named as unit polyion complexes (uPICs), using two-branched poly(ethylene glycol)-b-poly(l-lysine) (bPEG-PLys). The blood retention time of uPICs is dramatically increased in the presence of free bPEG-PLys, suggesting dynamic stabilization of uPICs by free bPEG-PLys based on their equilibrium. Herein, we examined how the degree of polymerization of PLys (DPPLys) affected the dynamic stability of uPICs in the bloodstream during prolonged circulation. We prepared a series of bPEG-PLys with DPPLys values of 10, 13, 20, 40, and 80 for the uPIC formation and siRNA with 40 negative charges. These bPEG-PLys were then evaluated in physicochemical characterization and pharmacokinetic analyses. Structural analyses revealed that the uPIC size and association numbers were mainly determined by the molecular weights of PEG and DPPLys, respectively. Under bPEG-PLys-rich conditions, the hydrodynamic diameters of uPICs were 15-20 nm, which were comparable to that of the bPEG block (i.e., ∼18 nm). Importantly, DPPLys significantly affected the association constant of bPEG-PLys to siRNA (Ka) and blood retention of free bPEG-PLys. A smaller DPPLys resulted in a lower Ka and a longer blood retention time of free bPEG-PLys. Thus, DPPLys can control the dynamic stability of uPICs, i.e., the balance between Ka and blood concentration of free bPEG-PLys. Ultimately, the bPEG-PLys with DPPLys values of 14 and 19 prolonged the blood circulation of siRNA-loaded uPICs with relatively small amounts of free bPEG-PLys. This study revealed that the uPIC formation between siRNA and bPEG-PLys can be controlled by their charges, which may be helpful for designing PIC-based delivery systems.

Systemic Brain Delivery of Antisense Oligonucleotides across the Blood-Brain Barrier with a Glucose-Coated Polymeric Nanocarrier.

Current antisense oligonucleotide (ASO) therapies for the treatment of central nervous system (CNS) disorders are performed through invasive administration, thereby placing a major burden on patients. To alleviate this burden, we herein report systemic ASO delivery to the brain by crossing the blood-brain barrier using glycemic control as an external trigger. Glucose-coated polymeric nanocarriers, which can be bound by glucose transporter-1 expressed on the brain capillary endothelial cells, are designed for stable encapsulation of ASOs, with a particle size of about 45 nm and an adequate glucose-ligand density. The optimized nanocarrier efficiently accumulates in the brain tissue 1 h after intravenous administration and exhibits significant knockdown of a target long non-coding RNA in various brain regions, including the cerebral cortex and hippocampus. These results demonstrate that the glucose-modified polymeric nanocarriers enable noninvasive ASO administration to the brain for the treatment of CNS disorders.

Robust Polyion Complex Vesicles (PICsomes) under Physiological Conditions Reinforced by Multiple Hydrogen Bond Formation Derived by Guanidinium Groups.

Polyion complex vesicles (PICsomes) formed from a self-assembly of an oppositely charged pair of block- and homo-polyelectrolytes have shown exceptional features for functional loading of bioactive agents. Nevertheless, the stability of PICsomes is often jeopardized in a physiological environment, and only PICsomes having chemically cross-linked membranes have endured in harsh in vivo conditions, such as in the bloodstream. Herein, we developed versatile PICsomes aimed to last in in vivo settings by stabilizing their membrane through a combination of ionic and hydrogen bonding, which is widely found in natural proteins as a salt bridge, by controlled introduction of guanidinium groups in the polycation fraction toward concurrent polyion complexation and hydrogen bonding. The guanidinylated PICsomes were successfully assembled under physiological salt conditions, with precise control of their morphology by tuning the guanidinium content, and the ratio of anionic and cationic components. Guanidinylated PICsomes with 100 nm diameter, which are relevant to nanocarrier development, were stable in high urea concentration, at physiological temperature, and under serum incubation, persisting in blood circulation in vivo.

Tuned Density of Anti-Tissue Factor Antibody Fragment onto siRNA-Loaded Polyion Complex Micelles for Optimizing Targetability into Pancreatic Cancer Cells.

Antibody fragment (Fab')-installed polyion complex (PIC) micelles were constructed to improve targetability of small interfering RNA (siRNA) delivery to pancreatic cancer cells. To this end, we synthesized a block copolymer of azide-functionalized poly(ethylene glycol) and poly(l-lysine) and prepared PIC micelles with siRNA. Then, a dibenzylcyclooctyne (DBCO)-modified antihuman tissue factor (TF) Fab' was conjugated to azido groups on the micellar surface. A fluorescence correlation spectroscopic analysis revealed that 1, 2, or 3 molecule(s) of Fab'(s) were installed onto one micellar nanoparticle according to the feeding ratio of Fab' (or DBCO) to micelle (or azide). The resulting micelles exhibited ∼40 nm in hydrodynamic diameter, similar to that of the parent micelles before Fab' conjugation. Flow cytometric analysis showed that three molecules of Fab'-installed PIC micelles (3(Fab')-micelles) had the highest binding affinity to cultured pancreatic cancer BxPC3 cells, which are known to overexpress TF on their surface. The 3(Fab')-micelles also exhibited the most efficient gene silencing activity against polo-like kinase 1 mRNA in the cultured cancer cells. Furthermore, the 3(Fab')-micelles exhibited high penetrability and the highest cellular internalization amounts in BxPC3 spheroids compared with one or two molecule(s) of Fab'-installed PIC micelles. These results demonstrate the potential of anti-TF Fab'-installed PIC micelles for active targeting of stroma-rich pancreatic tumors.

Molecularly Imprinted Nanogels Acquire Stealth In†Situ by Cloaking Themselves with Native Dysopsonic Proteins.

Protein corona formation was regulated on the surface in vivo by molecular imprinting to enable polymeric nanogels to acquire stealth upon intravenous administration. Albumin, the most abundant protein in blood, was selected as a distinct protein component of protein corona for preparing molecularly imprinted nanogels (MIP-NGs) to form an albumin-rich protein corona. Intravital fluorescence resonance energy transfer imaging of rhodamine-labeled albumin and fluorescein-conjugated MIP-NGs showed that albumin was captured by MIP-NGs immediately after injection, forming an albumin-rich protein corona. MIP-NGs circulated in the blood longer than those of non-albumin-imprinted nanogels, with almost no retention in liver tissue. MIP-NGs also passively accumulated in tumor tissue. These data suggest that this strategy, based on regulation of the protein corona in vivo, may significantly influence the development of drug nanocarriers for cancer therapy.

Therapeutic Vesicular Nanoreactors with Tumor-Specific Activation and Self-Destruction for Synergistic Tumor Ablation.

Polymeric nanoreactors (NRs) have distinct advantages to improve chemical reaction efficiency, but the in vivo applications are limited by lack of tissue-specificity. Herein, novel glucose oxidase (GOD)-loaded therapeutic vesicular NRs (theraNR) are constructed based on a diblock copolymer containing poly(ethylene glycol) (PEG) and copolymerized phenylboronic ester or piperidine-functionalized methacrylate (P(PBEM-co-PEM)). Upon systemic injection, theraNR are inactive in normal tissues. At a tumor site, theraNR are specifically activated by the tumor acidity via improved permeability of the membranes. Hydrogen peroxide (H2 O2 ) production by the catalysis of GOD in theraNR increases tumor oxidative stress significantly. Meanwhile, high levels of H2 O2 induce self-destruction of theraNR releasing quinone methide (QM) to deplete glutathione and suppress the antioxidant ability of cancer cells. Finally, theraNR efficiently kill cancer cells and ablate tumors via the synergistic effect.

Systemically Injectable Enzyme-Loaded Polyion Complex Vesicles as In Vivo Nanoreactors Functioning in Tumors.

The design and construction of nanoreactors are important for biomedical applications of enzymes, but lipid- and polymeric-vesicle-based nanoreactors have some practical limitations. We have succeeded in preparing enzyme-loaded polyion complex vesicles (PICsomes) through a facile protein-loading method. The preservation of enzyme activity was confirmed even after cross-linking of the PICsomes. The cross-linked ß-galactosidase-loaded PICsomes (ß-gal@PICsomes) selectively accumulated in the tumor tissue of mice. Moreover, a model prodrug, HMDER-ßGal, was successfully converted into a highly fluorescent product, HMDER, at the tumor site, even 4 days after administration of the ß-gal@PICsomes. Intravital confocal microscopy showed continuous production of HMDER and its distribution throughout the tumor tissues. Thus, enzyme-loaded PICsomes are useful for prodrug activation at the tumor site and could be a versatile platform for enzyme delivery in enzyme prodrug therapy.

Density-tunable conjugation of cyclic RGD ligands with polyion complex vesicles for the neovascular imaging of orthotopic glioblastomas.

Introduction of ligands into 100 nm scaled hollow capsules has great potential for diagnostic and therapeutic applications in drug delivery systems. Polyethylene glycol-conjugated (PEGylated) polyion complex vesicles (PICsomes) are promising hollow nano-capsules that can survive for long periods in the blood circulation and can be used to deliver water-soluble macromolecules to target tissues. In this study, cyclic RGD (cRGD) peptide, which is specifically recognized by αVß3 and αvß5 integrins that are expressed at high levels in the neovascular system, was conjugated onto the distal end of PEG strands on PICsomes for active neovascular targeting. Density-tunable cRGD-conjugation was achieved using PICsomes with definite fraction of end-functionalized PEG, to substitute 20, 40, and 100% of PEG distal end of the PICsomes to cRGD moieties. Compared with control-PICsomes without cRGD, cRGD-PICsomes exhibited increased uptake into human umbilical vein endothelial cells. Intravital confocal laser scanning microscopy revealed that the 40%-cRGD-PICsomes accumulated mainly in the tumor neovasculature and remained in the perivascular region even after 24 h. Furthermore, we prepared superparamagnetic iron oxide (SPIO)-loaded cRGD-PICsomes for magnetic resonance imaging (MRI) and successfully visualized the neovasculature in an orthotopic glioblastoma model, which suggests that SPIO-loaded cRGD-PICsomes might be useful as a MRI contrast reagent for imaging of the tumor microenvironment, including neovascular regions that overexpress αVß3 integrins.

Aggregation behavior of cationic nanohydrogel particles in human blood serum.

For systemic siRNA delivery applications, well-defined drug carriers are required that guarantee stability for both carrier and cargo. Among various concepts progressing in market or final development, cationic nanohydrogel particles may serve as novel transport media especially designed for siRNA-in vivo experiments. In this work, the interaction of nanohydrogel particles with proteins and serum components was studied via dynamic light scattering in human blood serum as novel screening method prior to applications in vivo. The formation of larger aggregates mostly caused by charge interaction with albumin could be suppressed by nanogel loading with siRNA affording a neutral zeta potential for the complex. Preliminary in vivo studies confirmed the results inside the light-scattering cuvette. Although both carrier and cargo may have limited stability on their own under physiological relevant conditions, they can form safe and stable complexes at a charge neutralized ratio and thus making them applicable to systemic siRNA delivery.

Stealth and pseudo-stealth nanocarriers.

The stealth effect plays a central role on capacitating nanomaterials for drug delivery applications through improving the pharmacokinetics such as blood circulation, biodistribution, and tissue targeting. Here based on a practical analysis of stealth efficiency and a theoretical discussion of relevant factors, we provide an integrated material and biological perspective in terms of engineering stealth nanomaterials. The analysis surprisingly shows that more than 85% of the reported stealth nanomaterials encounter a rapid drop of blood concentration to half of the administered dose within 1 h post administration although a relatively long ß-phase is observed. A term, pseudo-stealth effect, is used to delineate this common pharmacokinetics behavior of nanomaterials, that is, dose-dependent nonlinear pharmacokinetics because of saturating or depressing bio-clearance of reticuloendothelial system (RES). We further propose structural holism can be a watershed to improve the stealth effect; that is, the whole surface structure and geometry play important roles, rather than solely relying on a single factor such as maximizing repulsion force through polymer-based steric stabilization (e.g., PEGylation) or inhibiting immune attack through a bio-inspired component. Consequently, engineering delicate structural hierarchies to minimize attractive binding sites, that is, minimal charges/dipole and hydrophobic domain, becomes crucial. In parallel, the pragmatic implementation of the pseudo-stealth effect and dynamic modulation of the stealth effect are discussed for future development.

Nanomedicine targeting brain lipid metabolism as a feasible approach for controlling the energy balance.

Targeting brain lipid metabolism is a promising strategy to regulate the energy balance and fight metabolic diseases such as obesity. The development of stable platforms for selective delivery of drugs, particularly to the hypothalamus, is a challenge but a possible solution for these metabolic diseases. Attenuating fatty acid oxidation in the hypothalamus via CPT1A inhibition leads to satiety, but this target is difficult to reach in vivo with the current drugs. We propose using an advanced crosslinked polymeric micelle-type nanomedicine that can stably load the CPT1A inhibitor C75-CoA for in vivo control of the energy balance. Central administration of the nanomedicine induced a rapid attenuation of food intake and body weight in mice via regulation of appetite-related neuropeptides and neuronal activation of specific hypothalamic regions driving changes in the liver and adipose tissue. This nanomedicine targeting brain lipid metabolism was successful in the modulation of food intake and peripheral metabolism in mice.

Size-tunable PEG-grafted copolymers as a polymeric nanoruler for passive targeting muscle tissues.

Muscle-targeted drug delivery is a major challenge in nanomedicine. The extravasation of nanomedicines (or nanoparticles) from the bloodstream into muscle tissues is hindered by the continuous endothelium, the so-called blood-muscle barrier. This study aimed to evaluate the optimal size of macromolecular drugs for extravasation (or passive targeting) into muscle tissues. We constructed a size-tunable polymeric delivery platform as a polymeric nanoruler by grafting poly(ethylene glycol)s (PEGs) onto the poly(aspartic acid) (PAsp) backbone. A series of PEG-grafted copolymers (gPEGs) with a narrow size distribution between 11 and 32 nm in hydrodynamic diameter (DH) were prepared by changing the molecular weight of the PEGs. Biodistribution analyses revealed that accumulation amounts of gPEGs in the muscle tissues of normal mice tended to decrease above their size of ~15 nm (or ~11 nm for the heart). The gPEGs accumulated in the skeletal muscles of Duchenne muscular dystrophy model mice (mdx mice) at a 2-3-fold higher level than in the skeletal muscles of normal mice. At the same time, there was a reduced accumulation of gPEGs in the spleen and liver. Intravital confocal laser scanning microscopy and immunohistochemical analysis showed extravasation and locally enhanced accumulation of gPEGs in the skeletal muscle of mdx mice. This study outlined the pivotal role of macromolecular drug size in muscle-targeted drug delivery and demonstrated the enhanced permeability of 11-32 nm-sized macromolecular drugs in mdx mice.

Novel redox nanomedicine improves gene expression of polyion complex vector.

Gene therapy has generated worldwide attention as a new medical technology. While non-viral gene vectors are promising candidates as gene carriers, they have several issues such as toxicity and low transfection efficiency. We have hypothesized that the generation of reactive oxygen species (ROS) affects gene expression in polyplex supported gene delivery systems. The effect of ROS on the gene expression of polyplex was evaluated using a nitroxide radical-containing nanoparticle (RNP) as an ROS scavenger. When polyethyleneimine (PEI)/pGL3 or PEI alone was added to the HeLa cells, ROS levels increased significantly. In contrast, when (PEI)/pGL3 or PEI was added with RNP, the ROS levels were suppressed. The luciferase expression was increased by the treatment with RNP in a dose-dependent manner and the cellular uptake of pDNA was also increased. Inflammatory cytokines play an important role in ROS generation in vivo. In particular, tumor necrosis factor (TNF)-α caused intracellular ROS generation in HeLa cells and decreased gene expression. RNP treatment suppressed ROS production even in the presence of TNF-α and increased gene expression. This anti-inflammatory property of RNP suggests that it may be used as an effective adjuvant for non-viral gene delivery systems.

Structural tuning of oligonucleotides for enhanced blood circulation properties of unit polyion complexes prepared from two-branched poly(ethylene glycol)-block-poly(l-lysine).

Downsizing nanocarriers is a promising strategy for systemically targeting fibrotic cancers, such as pancreatic cancer, owing to enhanced tissue permeability. We recently developed a small oligonucleotide nanocarrier called a unit polyion complex (uPIC) using a single oligonucleotide molecule and one or two molecule(s) of two-branched poly(ethylene glycol)-b-poly(l-lysine) (bPEG-PLys). The uPIC is a dynamic polyion-pair equilibrated with free bPEG-PLys, and thus, is highly stabilized in the presence of excess amounts of free bPEG-PLys in the bloodstream. However, the dynamic polyion-pairing behavior of uPICs needs to be further investigated for longevity in the bloodstream, especially under lower amounts of free bPEG-PLys. Herein, the polyion-pairing behavior of uPICs was investigated by highlighting oligonucleotide stability and negative charge number. To this end, small interfering RNA (siRNA) and antisense oligonucleotides (ASO) were chemically modified to acquire nuclease resistance, and the ASO was hybridized with complementary RNA (cRNA) to form a hetero-duplex oligonucleotide (HDO) with twice the negative charges. While all oligonucleotides similarly formed sub-20 nm-sized uPICs from a single oligonucleotide molecule, the association number of bPEG-PLys (ANbPEG-PLys) in uPICs varied based on the negative charge number of oligonucleotides (N-), that is, ANbPEG-PLys = ~2 at N- = ~40 (i.e., siRNA and HDO) and ANbPEG-PLys = ~1 at N- = 20 (i.e., ASO), presumably because of the balanced charge neutralization between the oligonucleotide and bPEG-PLys with a positive charge number (N+) of ~20. Ultimately, the uPICs prepared from the chemically modified oligonucleotide with higher negative charges showed considerably longer blood retention than those from the control oligonucleotides without chemical modifications or with lower negative charges. The difference in the blood circulation properties of uPICs was more pronounced under lower amounts of free bPEG-PLys. These results demonstrate that the chemical modification and higher negative charge in oligonucleotides facilitated the polyion-pairing between the oligonucleotide and bPEG-PLys under harsh biological conditions, facilitating enhanced blood circulation of uPICs.

Efficacy of pH-Sensitive Nanomedicines in Tumors with Different c-MYC Expression Depends on the Intratumoral Activation Profile.

Effective inhibition of the protein derived from cellular myelocytomatosis oncogene (c-Myc) is one of the most sought-after goals in cancer therapy. While several c-Myc inhibitors have demonstrated therapeutic potential, inhibiting c-Myc has proven challenging, since c-Myc is essential for normal tissues and tumors may present heterogeneous c-Myc levels demanding contrasting therapeutic strategies. Herein, we developed tumor-targeted nanomedicines capable of treating both tumors with high and low c-Myc levels by adjusting their ability to spatiotemporally control drug action. These nanomedicines loaded homologues of the bromodomain and extraterminal (BET) motif inhibitor JQ1 as epigenetic c-Myc inhibitors through pH-cleavable bonds engineered for fast or slow drug release at intratumoral pH. In tumors with high c-Myc expression, the fast-releasing (FR) nanomedicines suppressed tumor growth more effectively than the slow-releasing (SR) ones, whereas, in the low c-Myc tumors, the efficacy of the nanomedicines was the opposite. By studying the tumor distribution and intratumoral activation of the nanomedicines, we found that, despite SR nanomedicines achieved higher accumulation than the FR counterparts in both c-Myc high and low tumors, the antitumor activity profiles corresponded with the availability of activated drugs inside the tumors. These results indicate the potential of engineered nanomedicines for c-Myc inhibition and spur the idea of precision pH-sensitive nanomedicine based on cancer biomarker levels.

Co-encapsulation of Cas9 mRNA and guide RNA in polyplex micelles enables genome editing in mouse brain.

Genome editing using CRISPR/Cas9 has attracted considerable attention for the treatment of genetic disorders and viral infections. Co-delivery of Cas9 mRNA and single guide (sg)RNA is a promising strategy to efficiently edit the genome of various cell types, including non-dividing cells, with minimal safety concerns. However, co-delivery of two RNA species with significantly different sizes, such as Cas9 mRNA (4.5 kb) and sgRNA (0.1 kb), is still challenging, especially in vivo. Here, we addressed this issue by using a PEGylated polyplex micelle (PM) condensing the RNA in its core. PM loading sgRNA alone released sgRNA at minimal dilution in buffer, while PM loading Cas9 mRNA alone was stable even at higher dilutions. Interestingly, co-encapsulating sgRNA with Cas9 mRNA in a single PM prevented sgRNA release upon dilution, which led to the enhanced tolerability of sgRNA against enzymatic degradation. Subsequently, PM with co-encapsulated RNA widely induced genome editing in parenchymal cells in the mouse brain, including neurons, astrocytes, and microglia, following intraparenchymal injection, at higher efficiency than that by co-delivery of PMs loaded with either Cas9 mRNA or sgRNA separately. To the best of our knowledge, this is the first report demonstrating the utility of RNA-based delivery of CRISPR/Cas9 in inducing genome editing in the brain parenchymal cells. Furthermore, the efficiency of genome editing using PMs was higher than using a non-PEGylated polyplex, due to the enhanced diffusion of PMs in the brain tissue. The results reported herein demonstrate the potential of using PMs to co-encapsulate Cas9 mRNA and sgRNA for in vivo genome editing.

Manipulating dynamic tumor vessel permeability to enhance polymeric micelle accumulation.

Selectively delivering anticancer drugs to solid tumors while avoiding their accumulation in healthy tissues is a major goal in polymeric micelle research. We have recently discovered that the extravasation and permeation of polymeric micelles occur in a dynamic manner characterized by vascular bursts followed by a brief and vigorous outward flow of fluid (called "nano-eruptions"). Nano-eruptions allow delivery of polymeric micelle-associated drugs, though delivery can be heterogeneous both among tumors and within an individual tumor, leading to suboptimal intratumoral distribution. Manipulation of nano-eruptions is expected to improve the efficiency of drug delivery systems (DDSs). By using compounds that affect the intratumoral environment, i.e. a TGF-ß inhibitor and chloroquine, the possibility of manipulating nano-eruptions to improve delivery efficiency was investigated. Both compounds were tested in a mouse xenograft model of GFP-labeled pancreatic tumor cells by tracing nano-eruption events and extravasation of size-modulated polymeric micelles in real-time through intravital confocal laser scanning microscopy. The TGF-ß inhibitor increased the number of dynamic vents, extended duration time, and generated dynamic vents with a wide range of sizes. Chloroquine did not affect the frequency of nano-eruptions, but it increased tumor vessel diameter, maximum nano-eruption area, and maximum radial increase. Both the TGF-ß inhibitor and chloroquine augmented nano-eruptions to diffuse polymeric micelles through tumor stroma, and these medications had a greater effect on the polymeric micelles with larger size, i.e. 70-nm, than on the smaller polymeric micelles having a 30-nm diameter. The results indicate that TGF-ß inhibition and chloroquine refashion the intratumoral distribution of DDSs by different mechanisms.

Supramolecularly enabled pH- triggered drug action at tumor microenvironment potentiates nanomedicine efficacy against glioblastoma.

The crucial balance of stability in blood-circulation and tumor-specific delivery has been suggested as one of the challenges for effective bench-to-bedside translation of nanomedicines (NMs). Herein, we developed a supramolecularly enabled tumor-extracellular (Tex) pH-triggered NM that can maintain the micellar structure with the entrapped-drug during systemic circulation and progressively release drug in the tumor by rightly sensing heterogeneous tumor-pH. Desacetylvinblastine hydrazide (DAVBNH), a derivative of potent anticancer drug vinblastine, was conjugated to an aliphatic ketone-functionalized poly(ethylene glycol)-b-poly(amino acid) copolymer and the hydrolytic stability of the derived hydrazone bond was efficiently tailored by exploiting the compartmentalized structure of polymer micelle. We confirmed an effective and safe therapeutic application of Tex pH-sensitive DAVBNH-loaded micelle (Tex-micelle) in orthotopic glioblastoma (GBM) models, extending median survival to 1.4 times in GBM xenograft and 2.6 times in GBM syngeneic model, compared to that of the free DAVBNH. The work presented here offers novel chemical insights into the molecular design of smart NMs correctly sensing Tex-pH via programmed functionalities. The practical engineering strategy based on a clinically relevant NM platform, and the encouraging therapeutic application of Tex-micelle in GBM, one of the most lethal human cancers, thus suggests the potential clinical translation of this system against other types of common cancers, including GBM.