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.

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.

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.

Enzymatically Transformable Polymersome-Based Nanotherapeutics to Eliminate Minimal Relapsable Cancer.

Prevention of metastatic and local-regional recurrence of cancer after surgery remains difficult. Targeting postsurgical premetastatic niche and microresiduals presents an excellent prospective opportunity but is often challenged by poor therapeutic delivery into minimal residual tumors. Here, an enzymatically transformable polymer-based nanotherapeutic approach is presented that exploits matrix metalloproteinase (MMP) overactivation in tumor-associated tissues to guide the codelivery of colchicine (microtubule-disrupting and anti-inflammatory agent) and marimastat (MMP inhibitor). The dePEGylation of polymersomes catalyzed by MMPs not only exposes the guanidine moiety to improve tissue/cell-targeting/retention to increase bioavailability, but also differentially releases marimastat and colchicine to engage their extracellular (MMPs) and intracellular (microtubules) targets of action, respectively. In primary tumors/overt metastases, the vasculature-specific targeting of nanotherapeutics can function synchronously with the enhanced permeability and retention effect to deter malignant progression of metastatic breast cancer. After the surgical removal of large primary tumors, nanotherapeutic agents are localized in the premetastatic niche and at the site of the postsurgical wound, disrupting the premetastatic microenvironment and eliminating microresiduals, which radically reduces metastatic and local-regional recurrence. The findings suggest that nanotherapeutics can safely widen the therapeutic window to resuscitate colchicine and MMP inhibitors for other inflammatory disorders.

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.

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.

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.

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.

Effect of Mixing Ratio of Oppositely Charged Block Copolymers on Polyion Complex Micelles for In Vivo Application.

Self-assembled supramolecular structures based on polyion complex (PIC) formation between oppositely charged polymers are attracting much attention for developing drug delivery systems able to endure harsh in vivo environments. As controlling polymer complexation provides an opportunity for engineering the assemblies, an improved understanding of the PIC formation will allow constructing assemblies with enhanced structural and functional capabilities. Here, we focused on the influence of the mixing charge ratio between block aniomers and catiomers on the physicochemical characteristics and in vivo biological performance of the resulting PIC micelles (PIC/m). Our results showed that by changing the mixing charge ratio, the structural state of the core was altered despite the sizes of PIC/m remaining almost the same. These structural variations greatly affected the stability of the PIC/m in the bloodstream after intravenous injection and determined their biodistribution.

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.

Transient stealth coating of liver sinusoidal wall by anchoring two-armed PEG for retargeting nanomedicines.

A major critical issue in systemically administered nanomedicines is nonspecific clearance by the liver sinusoidal endothelium, causing a substantial decrease in the delivery efficiency of nanomedicines into the target tissues. Here, we addressed this issue by in situ stealth coating of liver sinusoids using linear or two-armed poly(ethylene glycol) (PEG)-conjugated oligo(l-lysine) (OligoLys). PEG-OligoLys selectively attached to liver sinusoids for PEG coating, leaving the endothelium of other tissues uncoated and, thus, accessible to the nanomedicines. Furthermore, OligoLys having a two-armed PEG configuration was ultimately cleared from sinusoidal walls to the bile, while OligoLys with linear PEG persisted in the sinusoidal walls, possibly causing prolonged disturbance of liver physiological functions. Such transient and selective stealth coating of liver sinusoids by two-arm-PEG-OligoLys was effective in preventing the sinusoidal clearance of nonviral and viral gene vectors, representatives of synthetic and nature-derived nanomedicines, respectively, thereby boosting their gene transfection efficiency in the target tissues.

Dual-Sensitive Nanomicelles Enhancing Systemic Delivery of Therapeutically Active Antibodies Specifically into the Brain.

Delivering therapeutic antibodies into the brain across the blood-brain barrier at a therapeutic level is a promising while challenging approach in the treatment of neurological disorders. Here, we present a polymeric nanomicelle (PM) system capable of delivering therapeutically effective levels of 3D6 antibody fragments (3D6-Fab) into the brain parenchyma for inhibiting Aß aggregation. PM assembly was achieved by charge-converting 3D6-Fab through pH-sensitive citraconylation to allow complexation with reductive-sensitive cationic polymers. Brain targeting was achieved by functionalizing the PM surface with glucose molecules to allow interaction with recycling glucose transporter (Glut)-1 proteins. Consequently, 41-fold enhanced 3D6-Fab accumulation in the brain was achieved by using the PM system compared to free 3D6-Fab. Furthermore, therapeutic benefits were obtained by successfully inhibiting Aß1-42 aggregation in Alzheimer's disease mice systemically treated with 3D6-Fab-loaded glucosylated PM. Hence, this nanocarrier system represents a promising method for effectively delivering functional antibody agents into the brain and treating neurological diseases.

A chemically unmodified agonistic DNA with growth factor functionality for in vivo therapeutic application.

Although growth factors have great therapeutic potential because of their regenerative functions, they often have intrinsic drawbacks, such as low thermal stability and high production cost. Oligonucleotides have recently emerged as promising chemical entities for designing synthetic alternatives to growth factors. However, their applications in vivo have been recognized as a challenge because of their susceptibility to nucleases and limited distribution to a target tissue. Here, we present the first example of oligonucleotide-based growth factor mimetics that exerts therapeutic effects at a target tissue after systemic injection. The aptamer was designed to dimerize a growth factor receptor for its activation and mitigated the progression of Fas-induced fulminant hepatitis in a mouse model. This unprecedented functionality of the aptamer can be reasonably explained by its high nuclease stability and migration to the liver parenchyma. These mechanistic analyses provided insights for the successful application of aptamer-based receptor agonists.

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.

Dexamethasone Increases Cisplatin-Loaded Nanocarrier Delivery and Efficacy in Metastatic Breast Cancer by Normalizing the Tumor Microenvironment.

Dexamethasone is a glucocorticoid steroid with anti-inflammatory properties used to treat many diseases, including cancer, in which it helps manage various side effects of chemo-, radio-, and immunotherapies. Here, we investigate the tumor microenvironment (TME)-normalizing effects of dexamethasone in metastatic murine breast cancer (BC). Dexamethasone normalizes vessels and the extracellular matrix, thereby reducing interstitial fluid pressure, tissue stiffness, and solid stress. In turn, the penetration of 13 and 32 nm dextrans, which represent nanocarriers (NCs), is increased. A mechanistic model of fluid and macromolecule transport in tumors predicts that dexamethasone increases NC penetration by increasing interstitial hydraulic conductivity without significantly reducing the effective pore diameter of the vessel wall. Also, dexamethasone increases the tumor accumulation and efficacy of ∼30 nm polymeric micelles containing cisplatin (CDDP/m) against murine models of primary BC and spontaneous BC lung metastasis, which also feature a TME with abnormal mechanical properties. These results suggest that pretreatment with dexamethasone before NC administration could increase efficacy against primary tumors and metastases.

In vivo rendezvous of small nucleic acid drugs with charge-matched block catiomers to target cancers.

Stabilisation of fragile oligonucleotides, typically small interfering RNA (siRNA), is one of the most critical issues for oligonucleotide therapeutics. Many previous studies encapsulated oligonucleotides into ~100-nm nanoparticles. However, such nanoparticles inevitably accumulate in liver and spleen. Further, some intractable cancers, e.g., tumours in pancreas and brain, have inherent barrier characteristics preventing the penetration of such nanoparticles into tumour microenvironments. Herein, we report an alternative approach to cancer-targeted oligonucleotide delivery using a Y-shaped block catiomer (YBC) with precisely regulated chain length. Notably, the number of positive charges in YBC is adjusted to match that of negative charges in each oligonucleotide strand (i.e., 20). The YBC rendezvouses with a single oligonucleotide in the bloodstream to generate a dynamic ion-pair, termed unit polyion complex (uPIC). Owing to both significant longevity in the bloodstream and appreciably small size (~18 nm), the uPIC efficiently delivers oligonucleotides into pancreatic tumour and brain tumour models, exerting significant antitumour activity.

Glucose transporter 1-mediated vascular translocation of nanomedicines enhances accumulation and efficacy in solid tumors.

Nanomedicine modification with ligands directed to receptors on tumor blood vessels has the potential for selectively enhancing nanomedicine accumulation in malignant tissues by overcoming the vascular barrier of tumors. Nevertheless, the development of broadly applicable ligand approaches capable of promoting the transvascular transport of nanomedicines in a wide spectrum of tumors has been elusive so far. By considering the indispensable and persistent glycolytic fueling of tumors, we developed glucose-installed polymeric micelles loading cisplatin (Gluc-CDDP/m) targeting the glucose transporter 1 (GLUT1), which is overexpressed in most tumors and present on vascular endothelial cells, toward improving the delivery efficiency and therapeutic efficacy. The design of the glucose ligands on Gluc-CDDP/m was engineered to control the conjugation via the carbon 6 of the glucose moieties, as well as the ligand density on the poly (ethylene glycol) (PEG) shell of the micelles. The series of micelles was then studied in vitro and in vivo against GLUT1-high human squamous cell carcinoma of the head and neck OSC-19 cells and GLUT1-low human glioblastoma-astrocytoma U87MG cells. Our results showed that precisely tuning the micelles to have glucose ligands on 25% of their PEG chains increased the efficacy against the tumors by significantly enhancing the tumor accumulation, even in GLUT1-low U87MG tumors. The enhancement of the intratumoral levels of these micelles was hindered by concomitant administration of glucose, or the GLUT1 inhibitor STF-31, confirming a GLUT1/glucose-mediated increment of the accumulation. Intravital confocal laser scanning microscopy imaging of tumor tissues further demonstrated the rapid extravasation and penetration of Gluc-CDDP/m in OSC-19 tumors compared to non-targeted CDDP/m. These findings indicate GLUT1-targeting as a promising approach for overcoming the vascular barrier and boosting the delivery of nanomedicine in tumors.