Mechanisms of pH-Sensitivity and Cellular Internalization of PEOz-b-PLA Micelles with Varied Hydrophilic/Hydrophobic Ratios and Intracellular Trafficking Routes and Fate of the Copolymer

Preparation, characterisation, and pharmacodynamic study of myricetin pH-sensitive liposomes

AIMS

Myricetin (MYR) was incorporated into pH-sensitive liposomes in order to improve its bioavailability and anti-hyperuricemic activity.

METHODS

The MYR pH-sensitive liposomes (MYR liposomes) were prepared using thin film dispersion method, and assessed by particle size (PS), polydispersed index (PDI), zeta potential (ZP), encapsulation efficiency, drug loading, and in vitro release rate. Pharmacokinetics and anti-hyperuricemic activities were also evaluated.

RESULTS

The PS, PDI, ZP, encapsulation efficiency, and drug loading of MYR liposomes were 184.34 ± 1.05 nm, 0.215 ± 0.005, -38.46 ± 0.30 mV, 83.42 ± 1.07%w/w, and 6.20 ± 0.31%w/w, respectively. The release rate of MYR liposomes was higher than free MYR, wherein the cumulative value responded to pH. Besides, the Cmax of MYR liposomes was 4.92 ± 0.20 μg/mL. The level of uric acid in the M-L-H group (200 mg/kg) was reduced by 54.74%w/v in comparison with the model group.

CONCLUSION

MYR liposomes exhibited pH sensitivity and could potentially enhance the oral bioavailability and anti-hyperuricemic efficacy of MYR.

Targeted pH- and redox-responsive AuS/micelles with low CMC for highly efficient sonodynamic therapy of metastatic breast cancer

The efficacy of injectable micellar carriers is hindered due to the disassembly of micelles into free surfactants in the body, resulting in their dilution below the critical micelle concentration (CMC). Copolymer micelles were developed to address this issue, containing a superhydrophilic zwitterionic block and a superhydrophobic block with a disulfide bond, which exhibited a CMC lower than conventional micellar carriers. Cleavable copolymers composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) zwitterion and polycaprolactone CHLZW as the shell, with gold nanoparticles as their core, were studied to deliver doxorubicin to tumor cells while reducing the side effect of the free cytotoxic agent. The research focused on the impact of gold nanoparticles present in targeted TMT-micelles core on stability and in vivo bioavailability and sonotoxicity of the nanoparticles, as well as their synergistic effect on targeted chemotherapy. The nanomicelles prepared in this study demonstrated excellent biocompatibility and responsiveness to stimuli. PCL-SS-MPC nanomicelles displayed drug release in response to GSH and pH, resulting in high DOX release at GSH 10 mM and pH 5. Our findings, supported by MTT, flow cytometry, and confocal laser scanning microscopy, demonstrated that AuS-PM-TMTM-DOX micelles effectively induced apoptosis and enhanced cellular uptake in MCF7 and MDA-MB231 cell lines. The cytotoxic effects of AuS-PM-DOX/US on cancer cells were approximately 38 % higher compared to AuS-PM-DOX samples at a concentration of IC50 0.68 nM. This increase in cellular toxicity was primarily attributed to the promotion of apoptosis. The introduction of disulfide linkages in AuSNPs resulted in increased ROS production when exposed to ultrasound stimulation, due to a reduction in GSH levels. Compared to other commercially available nanosensitizers such as titanium dioxide, exposure of AuS-PM to ultrasound radiation (1.0 W/cm, 2 min) significantly enhanced cavitation effects and resulted in 3 to 5 times higher ROS production. Furthermore, laboratory experiments using human breast cancer cells (MDA-MB-231, MCF7) demonstrated that the toxicity of AuS-PM in response to ultrasound waves is dose-dependent. The findings of this study suggest that this formulated nanocarrier holds great potential as a viable treatment option for breast cancer. It can induce apoptosis in cancer cells, reduce tumor size, and display notable therapeutic efficacy.

A pH-responsive cetuximab-conjugated DMAKO-20 nano-delivery system for overcoming K-ras mutations and drug resistance in colorectal carcinoma

Cetuximab (Cet) and oxaliplatin (OXA) are used as first-line drugs for patients with colorectal carcinoma (CRC). In fact, the heterogeneity of CRC, mainly caused by K-ras mutations and drug resistance, undermines the effectiveness of drugs. Recently, a hydrophobic prodrug, (1E,4E)-6-((S)-1-(isopentyloxy)-4-methylpent-3-en-1-yl)-5,8-dimethoxynaphthalene-1,4‑dione dioxime (DMAKO-20), has been shown to undergo tumor-specific CYP1B1-catalyzed bioactivation. This process results in the production of nitric oxide and active naphthoquinone mono-oximes, which exhibit specific antitumor activity against drug-resistant CRC. In this study, a Cet-conjugated bioresponsive DMAKO-20/PCL-PEOz-targeted nanocodelivery system (DMAKO@PCL-PEOz-Cet) was constructed to address the issue of DMAKO-20 dissolution and achieve multitargeted delivery of the cargoes to different subtypes of CRC cells to overcome K-ras mutations and drug resistance in CRC. The experimental results demonstrated that DMAKO@PCL-PEOz-Cet efficiently delivered DMAKO-20 to both K-ras mutant and wild-type CRC cells by targeting the epidermal growth factor receptor (EGFR). It exhibited a higher anticancer effect than OXA in K-ras mutant cells and drug-resistant cells. Additionally, it was observed that DMAKO@PCL-PEOz-Cet reduced the expression of glutathione peroxidase 4 (GPX4) in CRC cells and significantly inhibited the growth of heterogeneous HCT-116 subcutaneous tumors and patient-derived tumor xenografts (PDX) model tumors. This work provides a new strategy for the development of safe and effective approaches for treating CRC. STATEMENT OF SIGNIFICANCE: (1) Significance: This work reports a new approach for the treatment of colorectal carcinoma (CRC) using the bioresponsible Cet-conjugated PCL-PEOz/DMAKO-20 nanodelivery system (DMAKO@PCL-PEOz-Cet) prepared with Cet and PCL-PEOz for the targeted transfer of DMAKO-20, which is an anticancer multitarget drug that can even prevent drug resistance, to wild-type and K-ras mutant CRC cells. DMAKO@PCL-PEOz-Cet, in the form of nanocrystal micelles, maintained stability in peripheral blood and efficiently transported DMAKO-20 to various subtypes of colorectal carcinoma cells, overcoming the challenges posed by K-ras mutations and drug resistance. The system's secure and effective delivery capabilities have also been confirmed in organoid and PDX models. (2) This is the first report demonstrating that this approach simultaneously overcomes the K-ras mutation and drug resistance of CRC.

Intra-articular nanoparticles based therapies for osteoarthritis and rheumatoid arthritis management

Osteoarthritis (OA) and rheumatoid arthritis (RA) are chronic and progressive inflammatory joint diseases that affect a large population worldwide. Intra-articular administration of various therapeutics is applied to alleviate pain, prevent further progression, and promote cartilage regeneration and bone remodeling in both OA and RA. However, the effectiveness of intra-articular injection with traditional drugs is uncertain and controversial due to issues such as rapid drug clearance and the barrier afforded by the dense structure of cartilage. Nanoparticles can improve the efficacy of intra-articular injection by facilitating controlled drug release, prolonged retention time, and enhanced penetration into joint tissue. This review systematically summarizes nanoparticle-based therapies for OA and RA management. Firstly, we explore the interaction between nanoparticles and joints, including articular fluids and cells. This is followed by a comprehensive analysis of current nanoparticles designed for OA/RA, divided into two categories based on therapeutic mechanisms: direct therapeutic nanoparticles and nanoparticles-based drug delivery systems. We highlight nanoparticle design for tissue/cell targeting and controlled drug release before discussing challenges of nanoparticle-based therapies for efficient OA and RA treatment and their future clinical translation. We anticipate that rationally designed local injection of nanoparticles will be more effective, convenient, and safer than the current therapeutic approach.

Ginsenoside Rg3 liposomes regulate tumor microenvironment for the treatment of triple negative breast cancer

OBJECTIVE

To improve the solubility and targeting of Ginsenoside Rg3 (G-Rg3), in the current study, we constructed a novel targeting functional material folic acid -poly(2-ethyl-2-oxazoline)-cholesteryl methyl carbonate (FA-PEOz-CHMC, FPC) modified G-Rg3 liposomes (FPC-Rg3-L).

METHODS

FPC was synthesized by using folic acid (FA) as a targeted head coupling with acid-activated poly(2-ethyl-2-oxazoline)-cholesteryl methyl carbonate. The inhibitory effects of the G-Rg3 preparations on mouse breast cancer cells (4T1) were investigated by CCK-8 assay. Paraffin sections of female BALB/c mice viscera were taken for hematoxylin-eosin (H&E) staining after continuous tail vein injection of G-Rg3 preparations. BALB/c mice bearing triple-negative breast cancer (TNBC) were used as animal models to investigate the inhibition of G-Rg3 preparations on tumor growth and improving quality of life. Transforming growth factor-β1 (TGF-β1) and α-smooth muscular actin (α-SMA) were used to investigate the expression of two fibrosis factors in tumor tissues by western blotting.

RESULTS

Compared with G-Rg3 solution (Rg3-S) and Rg3-L, FPC-Rg3-L had a significant inhibitory effect on 4T1 cells (p < .01), and the half maximal inhibitory concentration (IC₅₀) of FPC-Rg3-L was significantly lower (p < .01). The H&E results showed that the injection of FPC-Rg3-L and Rg3-S did not cause damage to the organs of mice. Compared with the control group, tumor growth was significantly inhibited in mice treated with FPC-Rg3-L and G-Rg3 solutions (p < .01).

CONCLUSIONS

This study presents a new and safe treatment for TNBC, reduces the toxic and side effects of the drug, and provides a reference for the efficient use of Chinese herbal medicine components.

Irradiation accelerates SARS-CoV-2 infection by enhancing sphingolipid metabolism

Cancer patients who receive radiotherapy have a high risk of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection, but the concrete reason remains unclear. Herein, we investigated the influence of irradiation on the vulnerability of cancer cells to SARS-CoV-2 using S pseudovirions and probed the underlying mechanism via RNA-seq and other molecular biology techniques. Owing to the enhancement of sphingolipid metabolism, irradiation accelerated pseudovirion infection. Mechanistically, irradiation induced the expression of acid sphingomyelinase (ASM), which catalyses the hydrolysis of sphingomyelin to ceramide, contributing to lipid raft formation and promoting SARS-CoV-2 invasion. Inhibition of lipid raft formation with methyl-β-cyclodextrin (MβCD) or the tyrosine kinase inhibitor genistein and ASM suppression through small interfering RNA or amitriptyline (AMT) treatment abolished the enhancing effect of irradiation on viral infection. Animal experiments supported the finding that irradiation promoted SARS-CoV-2 S pseudovirion infection in A549 cell tumour-bearing BALB/c nude mice, whereas AMT treatment dramatically decreased viral infection. This study discloses the role of sphingolipid metabolism in irradiation-induced SARS-CoV-2 infection, thus providing a potential target for clinical intervention to protect patients receiving radiotherapy from COVID-19.

"Swiss Army Knife" black phosphorus-based nanodelivery platform for synergistic antiparkinsonian therapy via remodeling the brain microenvironment

The combination of excessive reactive oxygen species (ROS) levels, neuroinflammation, and pathogenic protein aggregation disrupt the homeostasis of brain microenvironment, creating conditions conducive to the progression of Parkinson's disease (PD). Restoring homeostasis by remodeling the brain microenvironment could reverse this complex pathological progression. However, treatment strategies that can induce this effect are currently unavailable. Herein, we developed a "Swiss Army Knife" nanodelivery platform consisting of matrine (MT) and polyethylene glycol-modified black phosphorus nanosheets (BP) that enables PD treatment by restoring brain microenvironment homeostasis. Under NIR irradiation, the photothermal effect induced by BP allowed the nanomedicine to cross the blood-brain barrier (BBB) and entered the brain parenchyma. In PD brains, the biological effects of BP and MT resulted in the removal of excess ROS, effective reduction of neuroinflammation, decreased aggregation of pathogenic proteins, and improved neurotransmitter delivery, eventually restoring dopamine levels in the striatum. This study demonstrated the effective capacity of a BP-based nanodelivery platform to enter the brain parenchyma and trigger multiple neuropathological changes in PD brains. The platform serves as a safe and effective anti-PD nanomedicine with immense clinical potential.

An Acid Response IR780-Based Targeted Nanoparticle for Intraoperative Near-Infrared Fluorescence Imaging of Ovarian Cancer

INTRODUCTION

Complete resection of all visible disease (R0 resection) is critical for the treatment of ovarian cancer patients, and accurate real-time guidance provided by intraoperative near-infrared (NIR) fluorescence images is beneficial for achieving complete resection of all visible disease.

METHODS

Based on the optical properties of IR780 and the characteristics of the acidic tumor microenvironment, we develop a new smart nanoparticle (eg, FA-IR780&PFOB-SNPs) by using the pH response nano framework (FA-PEG-PLGA-PEOz) and adjusting the amount of IR780. The FA-IR780&PFOB-SNPs was characterized for morphology, microstructure, particle size, pH-response, drug-loading efficiency and biological safety. The ultraclear fluorescence Navigation Endoscopy System was applied to evaluate the tumor recognition of FA-IR780&PFOB-SNPs in vivo.

RESULTS

The structure of FA-IR780&PFOB-SNPs was stable in a neutral environment, and the near-infrared (NIR) fluorescence was turned off, while the structure of FA-IR780&PFOB-SNPs was degraded in the acidic tumour microenvironment, and the NIR fluorescence was turned on. Through the ovarian subcutaneous xenograft tumour and ovarian intraperitoneal xenograft tumour models, it was confirmed that FA-IR780&PFOB-SNPs could clearly display the boundaries of abdominal micron-sized tumours through near-infrared fluorescence imaging, with a TBR greater than 5.

CONCLUSION

The FA-IR780&PFOB-SNPs have the potential to provide to ovarian cancer intraoperative near infrared fluorescence navigation during precision tumour resection to achieve R0 and improve the prognosis of ovarian cancer patients.

αvβ3 integrin-specific exosomes engineered with cyclopeptide for targeted delivery of triptolide against malignant melanoma

Background

Melanoma is the most malignant skin tumor and is difficult to cure with the alternative treatments of chemotherapy, biotherapy, and immunotherapy. Our previous study showed that triptolide (TP) exhibited powerful tumoricidal activity against melanoma. However, the clinical potential of TP is plagued by its poor aqueous solubility, short half-life, and biotoxicity. Therefore, developing an ideal vehicle to efficiently load TP and achieving targeted delivery to melanoma is a prospective approach for making full use of its antitumor efficacy.

Results

We applied exosome (Exo) derived from human umbilical cord mesenchymal stromal cells (hUCMSCs) and engineered them exogenously with a cyclic peptide, arginine-glycine-aspartate (cRGD), to encapsulate TP to establish a bionic-targeted drug delivery system (cRGD-Exo/TP), achieving synergism and toxicity reduction. The average size of cRGD-Exo/TP was 157.34 ± 6.21 nm, with a high drug loading of 10.76 ± 1.21%. The in vitro antitumor results showed that the designed Exo delivery platform could be effectively taken up by targeted cells and performed significantly in antiproliferation, anti-invasion, and proapoptotic activities in A375 cells via the caspase cascade and mitochondrial pathways and cell cycle alteration. Furthermore, the biodistribution and pharmacokinetics results demonstrated that cRGD-Exo/TP possessed superior tumor targetability and prolonged the half-life of TP. Notably, cRGD-Exo/TP significantly inhibited tumor growth and extended survival time with negligible systemic toxicity in tumor-bearing mice.

Conclusion

The results indicated that the functionalized Exo platform provides a promising strategy for targeted therapy of malignant melanoma.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01597-1.

Naturally Equipped Urinary Exosomes Coated Poly (2−ethyl−2−oxazoline)−Poly (D, L−lactide) Nanocarriers for the Pre−Clinical Translation of Breast Cancer

Recently, biomimetic nanoparticles for tumor−targeted therapy have attracted intensifying interest. Although exosomes are an excellent biomimetic material, numerous challenges are still hindering its clinical applications, such as low yield, insufficient targeting efficiency, and high cost. In this work, urinary exosomes (UEs) with high expression of CD9 and CD47 were extracted from breast cancer patients by a non−invasive method. Here, a nanotechnology approach is reported for tumor homologous targeting via CD9 and phagocytosis escape via CD47 through UE−coated poly (2−ethyl−2−oxazoline)−poly (D, L−lactide) (PEOz−PLA) nanoparticles (UEPP NPs). The cytotoxic agent doxorubicin (DOX)−loaded UEPP (UEPP−D) NPs with an initial particle size of 61.5 nm showed a burst release under acidic condition mimicking the tumor microenvironment. In vitro experiments revealed that UEPP−D NPs exhibited significantly improved cellular uptake, cytotoxicity, and apoptosis in MCF−7 cell lines as compared to DOX−loaded PEOz−PLA nanoparticles (PP−D NPs) and free DOX. More importantly, anti−phagocytosis and pharmacokinetic studies confirmed that UEPP−D NPs had superior immune escape ability and significantly prolonged the drug’s bloodstream circulation in vivo. Finally, UEPP−D NPs showed a markedly higher antitumor efficacy and lower side−toxicity in MCF−7 tumor bearing nude mice model. Thus, this versatile nano−system with immune escape, homologous targeting, and rapid response release characteristics could be a promising tool for breast cancer treatment.

Recent Progress in Bio-Responsive Drug Delivery Systems for Tumor Therapy

Spatially- and/or temporally-controlled drug release has always been the pursuit of drug delivery systems (DDSs) to achieve the ideal therapeutic effect. The abnormal pathophysiological characteristics of the tumor microenvironment, including acidosis, overexpression of special enzymes, hypoxia, and high levels of ROS, GSH, and ATP, offer the possibility for the design of stimulus-responsive DDSs for controlled drug release to realize more efficient drug delivery and anti-tumor activity. With the help of these stimulus signals, responsive DDSs can realize controlled drug release more precisely within the local tumor site and decrease the injected dose and systemic toxicity. This review first describes the major pathophysiological characteristics of the tumor microenvironment, and highlights the recent cutting-edge advances in DDSs responding to the tumor pathophysiological environment for cancer therapy. Finally, the challenges and future directions of bio-responsive DDSs are discussed.

Stromal Barrier-Dismantled Nanodrill-Like and Cancer Cell-Targeted pH-Responsive Polymeric Micelles for Further Enhancing the Anticancer Efficacy of Doxorubicin

Cancer-associated fibroblasts (CAFs) were believed to establish a tight physical barrier and a dense scaffold for tumor cells to make them maintain immunosuppression and drug resistance, strongly hindering nanoparticles to penetrate into the core of tumor tissues and limiting the performance of tumor cell-targeted nanoparticles. Here, we fabricated the substrate Z-Gly-Pro of fibroblast activation protein α (FAPα) and folic acid-codecorated pH-responsive polymeric micelles (dual ligand-modified PEOz-PLA polymeric micelles, DL-PP-PMs) that possessed nanodrill and tumor cell-targeted functions based on Z-Gly-pro-conjugated poly(2-ethyl-2-oxazoline)-poly(D,l-lactide) (ZGP-PEOz-PLA), folic acid (FA)-conjugated PEOz-PLA (FA-PEOz-PLA), and PEOz-PLA for cancer therapy. The micelles with about 40 nm particle size and a narrow distribution exhibited favorable pH-activated endo/lysosome escape induced by their pH responsibility. In addition, the enhancement of in vitro cellular uptake and cytotoxicity to folate receptors or FAPα-positive cells for doxorubicin (DOX)/DL-PP-PMs compared with DOX/PP-PMs evidenced the dual target ability of DOX/DL-PP-PMs, which was further supported by in vivo biodistribution results. As expected, in the human oral epidermal carcinoma (KB) cells xenograft nude mice model, the remarkable enhancement of antitumor efficacy for DOX/DL-PP-PMs with low toxicity was observed compared with DOX/FA-PP-PMs and DOX/ZGP-PP-PMs. The possible mechanism was elucidated to be the dismantling of the stromal barrier by nanodrill-like DOX/DL-PP-PMs via the deletion of CAFs evidenced by the downregulation of α-SMA and inhibition of their functions proved by the decrease in the microvascular density labeled with CD31 and the reduction in the extracellular matrix detected by the collagen content, thereby promoting tumor penetration and enhancing their uptake by tumor cells. The present research offered an alternative approach integrating anticancer and antifibrosis effects in one delivery system to enhance the delivery efficiency and therapeutic efficacy of anticancer drugs.

Charge-reversal biodegradable MSNs for tumor synergetic chemo/photothermal and visualized therapy

Given the difficulties of biodegradation of mesoporous silica nanoparticles (NPs), enrichment and penetration of tumor sites, and real-time monitoring of the treatment process, we developed a kind of mannose-doping doxorubicin-loading mesoporous silica nanoparticle (MSN-Man-DOX) and coated by polydopamine-Gd³⁺ (PDAGd) metal-phenolic networks, as well as modified by poly (2-Ethyl-2-Oxazoline) (PEOz), constructing a novel nanomedicine MSN-Man-DOX@PDA-Gd-PEOz. Its pH-responsive charge reversal, photothermal, biodegradation, drug release, and magnetic resonance imaging (MRI) properties were evaluated in vitro. Cellular uptake, tumor penetration, lysosomal escape properties, as well as cell safety and toxicity of the nanoplatform were investigated through cell experiments. Finally, the MRI, organ distribution, photothermal condition, and comprehensive anti-tumor therapy in vivo were evaluated comprehensively through animal experiments. Research results showed that MSN-Man-DOX@PDA-Gd-PEOz had outstanding tumor enrichment and penetration abilities, which can produce excellent treatment effects through the synergistic effect of chemotherapy and photothermal therapy (PTT) with the function of magnetic resonance imaging contrast agent for disease monitoring. Besides, after finishing the therapeutic effect MSN-Man-DOX@PDA-Gd-PEOz can be biodegraded, so it had a good prospect of clinical application.

Advances in amphiphilic polylactide/vinyl polymer based nano-assemblies for drug delivery

Micelles from self-assembled amphiphilic copolymers are highly attractive in drug delivery, due to their small size and hydrophilic stealth corona allowing prolonged lifetimes in the bloodstream and thus improved drug bioavailability. Polylactide (PLA)-based amphiphilic copolymer micelles are key candidates in this field, owing to the well-established biodegradability and biocompatibility of PLA. While PLA-b-poly(ethylene glycol) (PEG) block copolymer micelles can be seen as the "gold standard" in drug delivery research so far, the progresses in controlled radical polymerizations (Atom Transfer Radical Polymerization, Reversible Addition-Fragmentation Transfer and Nitroxide Mediated Polymerization) have offered new opportunities in the design of advanced amphiphilic copolymers for drug delivery due to their flexibility in many regards: (i) they can be easily combined with ring-opening polymerization (ROP) of lactide, with a diversity in types of architectures (e.g., block, graft, star), (ii) they allow (co)polymerization of a wide range of vinyl monomers, possibly circumventing PEG limitations, (iii) functionalization (with biomolecules or stimuli-cleavable moieties) is versatile due to end-group fidelity and copolymerization ability with reactive/functional comonomers. In this review, we report on the advances in the past decade of such amphiphilic PLA/vinyl polymer based nano-carriers, regarding key properties such as stealth character, cell targeting and stimuli-responsiveness.

Tumor-Acidity Responsive Polymeric Nanoparticles for Targeting Delivery of Angiogenesis Inhibitor for Enhanced Antitumor Efficacy With Decreased Toxicity

Various nanocarriers with tumor targeting ability and improved pharmacokinetic property have been extensively utilized to reduce the toxicity of existing clinical chemotherapeutics. Herein, we showed that by encapsulating angiogenesis inhibitor anlotinib into polymeric nanoparticles, we could significantly decrease its in vivo toxicity. The introduction of pH-responsiveness into the nanocarrier further enhanced its anti-tumor activity. Systemic administration of the anlotinib-loaded nanocarrier into mice bearing A549 and 4T1 subcutaneous tumor received a higher tumor growth suppression and metastasis inhibition without detectable side effects. This strategy offers a promising option to improve the patient compliance of anlotinib.

LRP1-mediated pH-sensitive polymersomes facilitate combination therapy of glioblastoma in vitro and in vivo

BACKGROUND

Glioblastoma (GBM) is the most invasive primary intracranial tumor, and its effective treatment is one of the most daunting challenges in oncology. The blood-brain barrier (BBB) is the main obstacle that prevents the delivery of potentially active therapeutic compounds. In this study, a new type of pH-sensitive polymersomes has been designed for glioblastoma therapy to achieve a combination of radiotherapy and chemotherapy for U87-MG human glioblastoma xenografts in nude mice and significantly increased survival time.

RESULTS

The Au-DOX@PO-ANG has a good ability to cross the blood-brain barrier and target tumors. This delivery system has pH-sensitivity and the ability to respond to the tumor microenvironment. Gold nanoparticles and doxorubicin are designed as a complex drug. This type of complex drug improve the radiotherapy (RT) effect of glioblastoma. The mice treated with Au-DOX@PO-ANG NPs have a significant reduction in tumor volume.

CONCLUSION

In summary, a new pH-sensitive drug delivery system was fabricated for the treatment of glioblastoma. The new BBB-traversing drug delivery system potentially represents a novel approach to improve the effects of the treatment of intracranial tumors and provides hope for glioblastoma treatment.

Stimuli-Responsive Micelles with Detachable Poly(2-ethyl-2-oxazoline) Shell Based on Amphiphilic Polyurethane for Improved Intracellular Delivery of Doxorubicin

Polyurethanes (PUs) have various biomedical applications including controlled drug delivery. However, the incompletely release of drug at tumor sites limits the efficiency of these drug loaded polyurethane micelles. Here we report a novel polymer poly(2-ethyl-2-oxazoline)-SS-polyurethane-SS-poly(2-ethyl-2-oxazoline) triblock polyurethane (PEtOz-PU(PTMCSS)-PEtOz). The hydrophilic pH-responsive poly(2-ethyl-2-oxazoline) was used as an end-block to introduce pH responsiveness, and the hydrophobic PU middle-block was easily synthesized by the reaction of poly (trimethylene carbonate) diol containing disulfide bonds (PTMC-SS-PTMC diol) and bis (2-isocyanatoethyl) disulfide (CDI). PEtOz-PU(PTMCSS)-PEtOz could self-assemble to form micelles (176 nm). The drug release profile of PEtOz-PU(PTMCSS)-PEtOz micelles loaded with Doxorubicin (DOX) was studied in the presence of acetate buffer (10 mM, pH 5.0) and 10 mM dithiothreitol (DTT). The results showed that under this environment, DOX-loaded polyurethane micelles could release DOX faster and more thoroughly, about 97% of the DOX was released from the DOX-loaded PEtOz-PU(PTMCSS)-PEtOz micelle. In addition, fluorescent microscopy and cell viability assays validated that the DOX-loaded polyurethane micelle strongly inhibits the growth of C6 cells, suggesting their potential as a new nanomedicine against cancer.

MMP-13 enzyme and pH responsive theranostic nanoplatform for osteoarthritis

Stimulus-responsive therapy permits precise control of therapeutic effect only at lesion of interest, which determines it a promising method for diagnosis and imaging-guided precision therapy. The acid environment and overexpressed matrix metalloproteinases-13 (MMP-13) are typical markers in osteoarthritis (OA), which enables the development of stimulus-responsive drug delivery system with high specificity for OA. We herein demonstrate a nano-micelle based stimuli-responsive theranostic strategy with reporting and drug release controlled by acidic pH and MMP-13 for OA therapy. Such nanoplatform is incorporated with a motif specifically targeting on cartilage, a motif responsive to matrix metalloproteinases-13 to specifically report OA condition and biodynamics of nano-micelles, an anti-inflammatory drug (e.g., psoralidin (PSO)) from traditional Chinese medicine, and a biocompatible polymeric skeleton for sustainable drug release in response to the acidic OA condition. The high effectiveness of this targeted precision therapy is demonstrated comprehensively by both in vitro and vivo evidences.

Further Enhancement in Intestinal Absorption of Paclitaxel by Using Transferrin-Modified Paclitaxel Nanocrystals

The intestinal epithelium is considered to be a major obstacle to the gastrointestinal administration for water-insoluble drugs. To enhance the intestinal absorption of paclitaxel by improving its solubility and overcoming the intestinal epithelium barrier, transferrin-modified paclitaxel nanocrystals were prepared based on the specific transferrin receptor expressed on the apical membrane of the intestinal epithelium and examined to exhibit a mean size of around 178 nm, a rod-like morphology, a sustained release property, and an enhanced in vitro antitumor effect. The in situ intestinal perfusion study proved that the intestinal absorption of transferrin-modified paclitaxel nanocrystals was remarkably enhanced compared with that of Taxol and unmodified paclitaxel nanocrystals, which was further evidenced by the result of pharmacokinetic study. Their transcytosis pathway and intracellular trafficking track were disclosed using Caco-2 cell monolayers. The transcytosis of transferrin-modified paclitaxel nanocrystals and unmodified paclitaxel nanocrystals was principally mediated by clathrin and lipid rafts. The colocalization of both paclitaxel nanocrystals with the organelles observed under confocal microscopy suggested that the late endosomes, lysosomes, ER, and Golgi apparatus played a part in the transcellular transport of both paclitaxel nanocrystals during their transcytosis. Therefore, the designed transferrin-modified drug nanocrystals might have a great potential in the enhancement of intestinal absorption of water-insoluble drugs.

Co-delivery of gemcitabine prodrug along with anti NF-κB siRNA by tri-layer micelles can increase cytotoxicity, uptake and accumulation of the system in the cancers

Combination treatment based on gene and chemotherapy is a promising strategy for effective cancer treatment due to the limited therapeutic efficacy of anticancer drugs. Dual functional polymeric micelles (PMs) have been emerged as potent nanocarriers for combinational cancer therapy. In the present study, the potential of tri-layer PMs loaded with anti-nuclear factor-κB (NF-κB) siRNA and 4-(N)-stearoyl gemcitabine (GemC18) has been investigated for cancer treatment. PMs with different core hydrophobicity were prepared by using poly(ε-caprolactone), polyethyleneimine and polyethylene glycol (PCL-PEI-PEG) copolymers and evaluated. The results revealed that GemC18-loaded PMs were significantly more cytotoxic than free drug on breast and pancreatic cancer cells. However, the cytotoxicity of drug loaded micelles was decreased by increasing the micellar core hydrophobicity because of decreasing drug release rate. Moreover, siRNA loaded PMs could considerably inhibit NF-κB expression. PMs loaded with both GemC18 and siRNA exhibited higher capability to induce apoptosis and inhibit migration of both cells. PMs with the most hydrophobic core indicated higher tumor accumulation efficiency via in-vivo imaging study. In conclusion, the prepared PMs hold a promise as an attractive dual functional delivery system for an effective cancer therapy.

Efficient Oral Delivery of Poorly Water-Soluble Drugs Using Carnitine/Organic Cation Transporter 2-Mediated Polymeric Micelles

The intestine epithelium is considered to be the most critical obstacle for nanoparticles for oral delivery of water-insoluble and poorly absorbed drugs. Based on the specific transporters located on the apical membrane of the intestinal epithelium, the carnitine-conjugated polymeric micelles targeting to the carnitine/organic cation transporter 2 (OCTN2) were developed by combining carnitine-conjugated poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) with monomethoxy poly(ethylene-glycol)-poly(d,l-lactide). The carnitine-conjugated micelles with favorable stability in gastrointestinal fluid were validated to remarkably increase the cellular internalization and transcellular transport, while these were not the cases in the presence of free carnitine. These were further confirmed by more distribution of the micelles within epithelial cells, on the apical and basolateral side of the epithelium in mice. Additionally, identification of the carnitine-conjugated micelles by OCTN2 was detected to facilitate cellular uptake of the micelles via fluorescence immunoassay. Both clathrin and caveolae/lipid rafts pathways mediated endocytosis and transcellular transport of the carnitine-conjugated micelles, implying the enrichment of endocytic and transcellular transport pathway compared with that of carnitine-unconjugated micelles. Further, the intracellular trafficking process of the carnitine-conjugated micelles was tracked under confocal laser scanning microscopy, which involved in intracellular compartments such as late endosomes, lysosomes, endoplasmic reticulum, and Golgi apparatus as well. In conclusion, the current study provided an efficient strategy to facilitate the oral absorption of water-insoluble and poorly absorbed agents using intestinal transporter-mediated polymeric micelles.

pH-Responsive Artesunate Polymer Prodrugs with Enhanced Ablation Effect on Rodent Xenograft Colon Cancer

Purpose

In this study, pH-sensitive poly(2-ethyl-2-oxazoline)-poly(lactic acid)-poly(β-amino ester) (PEOz-PLA-PBAE) triblock copolymers were synthesized and were conjugated with an antimalaria drug artesunate (ART), for inhibition of a colon cancer xenograft model.

Methods

The as-prepared polymer prodrugs are tended to self-assemble into polymeric micelles in aqueous milieu, with PEOz segment as hydrophilic shell and PLA-PBAE segment as hydrophobic core.

Results

The pH sensitivity of the as-prepared copolymers was confirmed by acid-base titration with pKb values around 6.5. The drug-conjugated polymer micelles showed high stability for at least 96 h in PBS and 37°C, respectively. The as-prepared copolymer prodrugs showed high drug loading content, with 9.57%±1.24% of drug loading for PEOz-PLA-PBAE-ART4. The conjugated ART could be released in a sustained and pH-dependent manner, with 92% of released drug at pH 6.0 and 57% of drug released at pH 7.4, respectively. In addition, in vitro experiments showed higher inhibitory effect of the prodrugs on rodent CT-26 cells than that of free ART. Animal studies also demonstrated the enhanced inhibitory efficacy of PEOz-PLA-PBAE-ART2 micelles on the growth of rodent xenograft tumor.

Conclusion

The pH-responsive artesunate polymer prodrugs are promising candidates for colon cancer adjuvant therapy.

Drug Delivery with Polymeric Nanocarriers-Cellular Uptake Mechanisms

Nanocarrier-based systems hold a promise to become "Dr. Ehrlich's Magic Bullet" capable of delivering drugs, proteins and genetic materials intact to a specific location in an organism down to subcellular level. The key question, however, how a nanocarrier is internalized by cells and how its intracellular trafficking and the fate in the cell can be controlled remains yet to be answered. In this review we survey drug delivery systems based on various polymeric nanocarriers, their uptake mechanisms, as well as the experimental techniques and common pathway inhibitors applied for internalization studies. While energy-dependent endocytosis is observed as the main uptake pathway, the integrity of a drug-loaded nanocarrier upon its internalization appears to be a seldomly addressed problem that can drastically affect the uptake kinetics and toxicity of the system in vitro and in vivo.

Multi pH-sensitive polymer–drug conjugate mixed micelles for efficient co-delivery of doxorubicin and curcumin to synergistically suppress tumor metastasis

Multi pH-responsive polymer-drug conjugate mixed micelles were fabricated to co-deliver doxorubicin and curcumin for synergistic suppression tumor metastasis via inhibiting the invasion, migration, intravasation and extravasation of tumor cells.

Intestinal oligopeptide transporter PepT1-targeted polymeric micelles for further enhancing the oral absorption of water-insoluble agents

The intestinal epithelium is the main barrier for nanocarriers to orally deliver poorly water-soluble and absorbed agents. To further improve the transmembrane transport efficiency of polymeric micelles, intestinal oligopeptide transporter PepT1-targeted polymeric micelles were fabricated by Gly-Sar-conjugated poly(ethylene glycol)-poly(d,l-lactic acid). The functionalized polymeric micelles with about 40 nm diameter, uniform spherical morphology and favorable cytocompatibility with Caco-2 cells were demonstrated to distinctly enhance the cellular uptake and transmembrane transport of the loaded agents. The results of intestinal absorption strongly evidenced the higher accumulation of the micelles inside the epithelial cells, at the apical and basolateral sides of the epithelium within the villi in mice. Furthermore, the interaction of Gly-Sar decorated polymeric micelles with PepT1 was explored to promote the internalization of the micelles through fluorescence immunoassay, and the PepT1 level on the membrane of Caco-2 cells treated with the micelles appeared to change in a distinctly time-dependent manner. Both clathrin- and caveolae-mediated pathways were involved in the transcellular transport for undecorated polymeric micelles, while the transcellular transport pathway for Gly-Sar decorated ones was changed to be mainly mediated by clathrin and lipid rafts. The colocalization of Gly-Sar decorated micelles with the organelles observed by confocal laser scanning microscopy indicated that late endosomes, lysosomes, endoplasmic reticulum and Golgi apparatus appeared to participate in the intracellular trafficking progression of the micelles. These results suggested that PepT1-targeted polymeric micelles might have a strong potential to greatly promote the oral absorption of poorly water-soluble and absorbed agents.

Biodegradable Magnesium-Incorporated Poly(l-lactic acid) Microspheres for Manipulation of Drug Release and Alleviation of Inflammatory Response

Poly(l-lactic acid) (PLLA) and magnesium (Mg) are widely concerned biodegradable materials, but during in vivo implantation, the former produces acidic degradation byproducts and can easily induce inflammation in surrounding tissues, whereas the latter is fast corroded and generates alkaline products. The purpose of this study is to develop Mg/PLLA composite microspheres as a novel delivery system, in which Mg particles are used to regulate the drug release profile and suppress PLLA-induced inflammatory response. Morphological observation shows that multiple Mg particles are dispersed both on the surface and in the interior of composite microspheres. In vitro release study indicates that by varying the Mg contents or its particle sizes, the internal connectivity of composite microspheres is changed during hydrolytic degradation, and drug delivery can be facilely manipulated with tunable release patterns. In vivo release study further confirms the feasibility of Mg/PLLA microspheres for tailoring drug release in a physiological environment. The animal experiment reveals that Mg particles can alleviate macrophage infiltration and inflammatory cytokine expression. These results demonstrate the availability of using biodegradable Mg particles to manipulate drug release as well as alleviate PLLA-induced inflammation. The present Mg/PLLA composite microspheres have potential applications in controlled delivery of various therapeutic agents, especially some growth factors, for bone regeneration.

pH-Responsive Dual Drug-Loaded Nanocarriers Based on Poly (2-Ethyl-2-Oxazoline) Modified Black Phosphorus Nanosheets for Cancer Chemo/Photothermal Therapy

Synergistic cancer therapy, such as those combining chemotherapeutic and photothermal methods, has stronger treatment effect than that of individual ones. However, it is challenging to efficiently deliver nanocarriers into tumor cells to elevate intracellular drug concentration. Herein, we developed an effective pH-responsive and dual drug co-delivery platform for combined chemo/photothermal therapy. An anticancer drug doxorubicin (DOX) was first loaded onto the surface of black phosphorus (BP). With poly(2-ethyl-2-oxazoline) (PEOz) ligand conjugated onto the polydopamine (PDA) coated BP nanosheets, targeted long circulation and cellular uptake in vivo was significantly improved. With another anticancer drug bortezomib (BTZ) loaded onto the surface of the nanocapsule, the platform can co-deliver two different drugs. The surface charge of the nanocapsule was reversed from negative to positive at the tumor extracellular pH (∼6.8), ionizing the tertiary amide groups along the PEOz chain, thus facilitating the cell internalization of the nanocarrier. The cytotoxicity therapeutic effect of this nanoplatform was further augmented under near-infrared laser irradiation. As such, our DOX-loaded BP@PDA-PEOz-BTZ platform is very promising to synergistic cancer therapy.

Improved intestinal absorption of paclitaxel by mixed micelles self-assembled from vitamin E succinate-based amphiphilic polymers and their transcellular transport mechanism and intracellular trafficking routes

To ensure that antitumor drugs can be effectively transported across intestinal barrier and then quickly released in tumor cells, mixed polymeric micelles (Mix-PMs) were designed and fabricated by combining poly(2-ethyl-2-oxazoline)-vitamin E succinate (PEOz-VES) with TPGS1000 for enhancing intestinal absorption of paclitaxel. PEOz-VES exhibited an extremely low critical micelle concentration and negligible cytotoxicity. The Mix-PMs were characterized to have about 20 nm in diameter, uniform spherical morphology, high drug-loading content and sustained drug release profile with a retained pH-sensitivity. The results of the transport through Caco-2 cell monolayers and intestinal absorption revealed that Mix-PMs displayed higher transcellular transport efficiency compared with PEOz-VES micelles and Taxol^®. The possible mechanism of transcellular transport for Mix-PMs was elucidated to be mainly through clathrin- and caveolae/lipid rafts-mediated transcytosis. Confocal laser scanning micrographs revealed that late endosomes, lysosomes, endoplasmic reticulum, Golgi apparatus, and mitochondria were all involved in intracellular trafficking of Mix-PMs. The proteins involved in transcytosis of Mix-PMs and finally excreted were unraveled for the first time by the analysis of proteins in the basolateral media according to the proteomics method. Consequently, the fabricated mixed polymeric micelles may have great potential in enhancing intestinal absorption and accelerating drug release in tumor cells.

Synergistically Enhanced Antimetastasis Effects by Honokiol-Loaded pH-Sensitive Polymer-Doxorubicin Conjugate Micelles

In an effort to prevent metastasis of breast tumor cells- at the same time of inhibiting tumor growth with less toxic side effects, honokiol (HNK) was encapsulated into pH-sensitive polymeric micelles based on the conjugate of poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) (PEOz-PLA) with doxorubicin (DOX), denoted as PEOz-PLA-imi-DOX. PEOz-PLA-imi-DOX was successfully synthesized by connecting DOX to the hydrophobic end of PEOz-PLA via acid-cleavable benzoic imine linker. HNK-loaded conjugate micelles (HNK/PP-DOX-PM) with a size of 21 nm and homogeneous spherical shape exhibited high drug-loading capacity. PEOz-PLA-imi-DOX and HNK/PP-DOX-PM displayed faster release of DOX at pH 5.0 than at pH 7.4. As anticipated, PEOz-PLA-imi-DOX maintained cytotoxicity of DOX against MDA-MB-231 cells. The synergistically enhanced in vitro antitumor effect of HNK/PP-DOX-PM was confirmed by their synergetic inhibition of MDA-MB-231 cell growth. Furthermore, the efficient prevention of tumor metastasis by HNK/PP-DOX-PM was testified by in vitro anti-invasion, wound healing and antimigration assessment in MDA-MB-231 cells, and in vivo bioluminescence imaging in nude mice. The suppression of growth and metastasis of tumor cells by HNK/PP-DOX-PM was attributed to the synergistic effect of pH-triggered drug release and HNK-aroused inhibition of matrix metalloproteinases and epithelial-mesenchymal transition, respectively. In addition, HNK/PP-DOX-PM exhibited superior biosafety than physically encapsulated dual-drug micelles. Consequently, the fabricated HNK/PP-DOX-PM may have great potential for safe and effective suppression of tumor growth and metastasis.

Intestinal Mucin Induces More Endocytosis but Less Transcytosis of Nanoparticles across Enterocytes by Triggering Nanoclustering and Strengthening the Retrograde Pathway

Mucus, which is secreted by the goblet cells of enterocytes, constitutes the first obstacle encountered for the intestinal absorption of nanomedicines. For decades, mucus has simply been regarded as a physical barrier that hinders the permeation and absorption of drugs, because of its high viscosity and reticular structure, whereas the interaction of mucus ingredients with nanomedicines is usually neglected. It is unclear whether glycoproteins, as the main components of mucus, interact with nanomedicines. We also do not know how the potential interaction affects the subsequent transportation of nanomedicines through the intestinal epithelium. In this study, mucin as the key element of mucus was investigated to characterize the interaction of nanomedicines with mucus. PEG-modified gold nanoparticles (PGNPs) were fabricated as model nanoparticles. Mucin was found to adhere to the nanoparticle surface to form a corona structure and induce the clustering of PGNPs by joining particles together, demonstrating the interaction between mucin and PGNPs. In addition, two intestinal epithelia, Caco-2 (non- mucus secretion) and HT-29 (high mucus secretion), were compared to evaluate the influence of mucin on the cellular interaction of PGNPs. Amazingly, mucin altered the trafficking characteristic of PGNPs in intestinal epithelium. Both in vitro and in vivo investigations demonstrated more nanoparticles being internalized by cells due to the mucin coverage. However, mucin induced a significant reduction in the transcytosis of PGNPs across epithelial monolayers. The mechanism exploration further revealed that the "more endocytosis but less transcytosis (MELT)" effect was mainly attributed to the strengthened retrograde pathway in which more PGNPs were transported to Golgi apparatus and exocytosed back to the apical but not the basolateral side of the epithelial monolayers. The "MELT" effect endowed mucin with duality in the nanoparticle transportation. Therefore, the rational regulation based on the "MELT" effect will provide new insight into overcoming the mucus obstacle as a barrier and enhancing the oral absorption rate of nanomedicines.

The mechanism difference between CO2 and pH stimuli for a dual responsive wormlike micellar system

To indicate the difference between pH and CO₂ stimuli mechanisms, a dual responsive system is constructed with the aid of N-[3-(dimethylamino)propyl]docosanamide (NDPD) and sodium salicylate (NaSal), which is responsive to pH and CO₂.

Concurrently suppressing multidrug resistance and metastasis of breast cancer by co-delivery of paclitaxel and honokiol with pH-sensitive polymeric micelles

To concurrently suppress multidrug resistance (MDR) and metastasis of breast cancer cells, paclitaxel (PTX) and honokiol (HNK) were coencapsulated into pH-sensitive polymeric micelles based on poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) (PEOz-PLA). The physicochemical properties of dual drug-loaded PEOz-PLA micelles were characterized in size, drug loading and in vitro release. The efficiency of MDR reversal for the micelles was testified by synergetic enhancement of cytotoxicity and uptake by MCF-7/ADR cells. The flow cytometry and fluorescence polarization measurement results reinforced the conclusion that down-regulation of P-gp expression and increase of plasma membrane fluidity appeared to be possible mechanisms of MDR reversal by dual drug-loaded PEOz-PLA micelles. Further, the efficient inhibition of tumor metastasis by dual drug-loaded PEOz-PLA micelles was demonstrated by in vitro anti-invasion and anti-migration assessment in MDA-MB-231 cells and in vivo bioluminescence imaging in nude mice. The suppression of MDR and metastasis by the micelles was assigned to synergistic effects of pH-triggered drug release and HNK/PEOz-PLA-aroused P-gp inhibition, and pH-triggered drug release and PTX/HNK-aroused MMPs inhibition, respectively. In conclusion, our findings strengthen the usefulness of co-delivery of PTX and HNK by pH-responsive polymeric micelles for suppression of tumor MDR and metastasis.

STATEMENT OF SIGNIFICANCE

Multidrug resistance (MDR) and metastasis are considered to be two of the major barriers for successful chemotherapy. The combination of a chemotherapeutic drug with a modulator has emerged as a promising strategy for efficiently treating MDR cancer and preventing tumor metastasis. Herein, a dual drug (paclitaxel and honokiol)-loaded pH-sensitive polymeric micelle system based on PEOz-PLA was successfully fabricated to ensure that tumor MDR and metastasis could be concurrently suppressed, therefore achieving distinguishing endo/lysosomal pH from physiological pH by accelerating drug release and then enhancing the cytotoxicity of paclitaxel to drug-resistant tumor cells MCF-7/ADR by increasing cellular uptake of paclitaxel, preventing in vitro invasion and migration for MDA-MB-231 cells and in vivo metastasis in nude mice. Further, the mechanism of MDR reversal by dual drug-loaded PEOz-PLA micelles was elucidated to be down-regulation of P-gp expression and increase of plasma membrane fluidity of MCF-7/ADR cells. The present findings strengthen the usefulness of co-delivery of PTX and HNK by pH-responsive polymeric micelles for suppression of tumor MDR and metastasis.