Histological study on side effects and tumor targeting of a block copolymer micelle on rats

Extracellular vesicles engineered to bind albumin demonstrate extended circulation time and lymph node accumulation in mouse models

Extracellular vesicles (EVs) have shown promise as potential therapeutics for the treatment of various diseases. However, their rapid clearance after administration could be a limitation in certain therapeutic settings. To solve this, an engineering strategy is employed to decorate albumin onto the surface of the EVs through surface display of albumin binding domains (ABDs). ABDs were either included in the extracellular loops of select EV-enriched tetraspanins (CD63, CD9 and CD81) or directly fused to the extracellular terminal of single transmembrane EV-sorting domains, such as Lamp2B. These engineered EVs exert robust binding capacity to human serum albumins (HSA) in vitro and mouse serum albumins (MSA) after injection in mice. By binding to MSA, circulating time of EVs dramatically increases after different routes of injection in different strains of mice. Moreover, these engineered EVs show considerable lymph node (LN) and solid tumour accumulation, which can be utilized when using EVs for immunomodulation, cancer- and/or immunotherapy. The increased circulation time of EVs may also be important when combined with tissue-specific targeting ligands and could provide significant benefit for their therapeutic use in a variety of disease indications.

Methoxy polyethylene glycol modification promotes adipogenesis by inducing the production of regulatory T cells in xenogeneic acellular adipose matrix

Acellular adipose matrix (AAM) has emerged as an important biomaterial for adipose tissue regeneration. Current decellularization methods damage the bioactive components of the extracellular matrix (ECM), and the residual immunogenic antigens may induce adverse immune responses. Here, we adopted a modified decellularization method which can protect more bioactive components with less immune reaction by methoxy polyethylene glycol (mPEG). Then, we determined the adipogenic mechanisms of mPEG-modified AAM after xenogeneic transplantation. AAM transplantation caused significantly lesser adipogenesis in the wild-type group than in the immune-deficient group. The mPEG-modified AAM showed significantly lower immunogenicity and higher adipogenesis than the AAM alone after xenogeneic transplantation. Furthermore, mPEG modification increased regulatory T (Treg) cell numbers in the AAM grafts, which in turn enhanced the M2/M1 macrophage ratio by secreting IL-10, IL-13, and TGF-β1. These findings suggest that mPEG modification effectively reduces the immunogenicity of xenogeneic AAM and promotes adipogenesis in the AAM grafts. Hence, mPEG-modified AAM can serve as an ideal biomaterial for xenogeneic adipose tissue engineering.

Polymeric Micelles: A Promising Pathway for Dermal Drug Delivery

Nanotechnology is an area in great development and with application in the most varied fields of science, including cosmetic and pharmaceutical industries. Because conventional formulations for topical application are not always able to effectively penetrate the physical barrier that human skin exerts against factors and compounds of the external environment, polymeric micelles appear as alternative carriers for drugs and active ingredients delivery, also allowing ingredients with lower solubility and higher lipophilicity to be delivered. In fact, the augmented bioavailability of drugs, greater efficacy even at a lower dose, and selective drug delivery in specific organelles are very interesting advantages of the polymeric micelles usage in cutaneous application. As a consequence, they show a reduction in many of the local and systemic adverse effects, which might lead to an increase in patient compliance to the therapeutics, constituting a promising alternative to conventional topical formulations.

Assessing the pharmacokinetics and toxicology of polymeric micelle conjugated therapeutics

Introduction: Analogous to nanocarriers such as nanoparticles, liposomes, nano lipoidal carriers, niosomes, and ethosomes, polymeric micelles have gained significance in the field of drug delivery. They have attracted scientists worldwide by their nanometric size, wide range of polymers available for building block synthesis, stability and potential to enhance the targeting and safety of drugs. Incorporation of drugs within the interior of polymeric micelles alters the drug pharmacokinetics, which generally results in increased efficiency.Areas covered: This review deals with the pharmacokinetics of various anti-neoplastic drugs loaded into micelles. The structure of polymeric micelles, polymers employed in their development and techniques involved will be discussed. This is followed by discussion on the pharmacokinetics of anti-cancer drugs loaded into polymeric micelles and the toxicity concerns associated.Expert opinion: Polymeric micelles are nanometeric carriers, with higher stability, polymeric flexibility and higher drug loading of poorly water-soluble drugs. These nanosystems help in increasing the bioavailability of drugs by encapsulating them within the hydrophobic core. The proper selection and design of the amphiphilic polymer for micelles is a crucial step as it decides the toxicity and the biocompatibility.

Toxicity and immunogenicity concerns related to PEGylated-micelle carrier systems: a review

Polymeric-micelle carrier systems have emerged as a novel drug-carrier system and have been actively studied for anticancer drug targeting. In contrast, toxicological and immunological concerns related to not only polymeric-micelle carrier systems, but also other nanocarrier systems, have received little attention owing to researchers' focus on therapeutic effects. However, in recent clinical contexts, biopharmaceuticals' effects on immune responses have come to light, requiring that researchers substantively explore the potential negative side effects of nanocarrier systems and of therapeutic proteins in order to develop nanocarrier systems suitable for clinical use. The present review describes current insights into both toxicological and immunological issues regarding polymeric-micelle carrier systems. The review focuses on immunogenicity issues of polymeric-micelle carrier systems possessing poly(ethylene glycol) (PEG). We conclude that PEG-related immunogenicity is deeply related to characteristics of a counterpart block of PEG-conjugates, and we propose future directions for addressing this unresolved issue.

Smart nanocarrier-based drug delivery systems for cancer therapy and toxicity studies: A review

Nonspecific distribution and uncontrollable release of drugs in conventional drug delivery systems (CDDSs) have led to the development of smart nanocarrier-based drug delivery systems, which are also known as Smart Drug Delivery Systems (SDDSs). SDDSs can deliver drugs to the target sites with reduced dosage frequency and in a spatially controlled manner to mitigate the side effects experienced in CDDSs. Chemotherapy is widely used to treat cancer, which is the second leading cause of death worldwide. Site-specific drug delivery led to a keen interest in the SDDSs as an alternative to chemotherapy. Smart nanocarriers, nanoparticles used to carry drugs, are at the focus of SDDSs. A smart drug delivery system consists of smart nanocarriers, targeting mechanisms, and stimulus techniques. This review highlights the recent development of SDDSs for a number of smart nanocarriers, including liposomes, micelles, dendrimers, meso-porous silica nanoparticles, gold nanoparticles, super paramagnetic iron-oxide nanoparticles, carbon nanotubes, and quantum dots. The nanocarriers are described in terms of their structures, classification, synthesis and degree of smartness. Even though SDDSs feature a number of advantages over chemotherapy, there are major concerns about the toxicity of smart nanocarriers; therefore, a substantial study on the toxicity and biocompatibility of the nanocarriers has been reported. Finally, the challenges and future research scope in the field of SDDSs are also presented. It is expected that this review will be widely useful for those who have been seeking new research directions in this field and for those who are about to start their studies in smart nanocarrier-based drug delivery.

Rational design of multifunctional micelles against doxorubicin-sensitive and doxorubicin-resistant MCF-7 human breast cancer cells

Even though a tremendous number of multifunctional nanocarriers have been developed to tackle heterogeneous cancer cells, little attention has been paid to elucidate how to rationally design a multifunctional nanocarrier. In this study, three individual functions (active targeting, stimuli-triggered release and endo-lysosomal escape) were evaluated in doxorubicin (DOX)-sensitive MCF-7 cells and DOX-resistant MCF-7/ADR cells by constructing four kinds of micelles with active-targeting (AT-M), passive targeting, pH-triggered release (_pHT-M) and endo-lysosomal escape (_endoE-M) function, respectively. AT-M demonstrated the strongest cytotoxicity against MCF-7 cells and the highest cellular uptake of DOX due to the folate-mediated endocytosis. However, AT-M failed to exhibit the best efficacy against MCF-7/ADR cells, while _endoE-M exhibited the strongest cytotoxicity against MCF-7/ADR cells and the highest cellular uptake of DOX due to the lowest elimination of DOX from the cells. This was attributed to the carrier-facilitated endo-lysosomal escape of DOX, which avoided exocytosis by lysosome secretion, resulting in an effective accumulation of DOX in the cytoplasm. The enhanced elimination of DOX from the MCF-7/ADR cells also accounted for the remarkable decrease in cytotoxicity against the cells of AT-M. Three micelles were further evaluated with MCF-7 cells and MCF-7/ADR-resistant cells xenografted mice model. In accordance with the in vitro results, AT-M and _endoE-M demonstrated the strongest inhibition on the MCF-7 and MCF-7/ADR xenografted tumor, respectively. Active targeting and active targeting in combination with endo-lysosomal escape have been demonstrated to be the primary function for a nanocarrier against doxorubicin-sensitive and doxorubicin-resistant MCF-7 cells, respectively. These results indicate that the rational design of multifunctional nanocarriers for cancer therapy needs to consider the heterogeneous cancer cells and the primary function needs to be integrated to achieve effective payload delivery.

Tumor-targeted docetaxel-loaded hyaluronic acid-quercetin polymeric micelles with p-gp inhibitory property for hepatic cancer therapy

Herein, a novel targeted drug delivery nanosystem based on hyaluronic acid (HA) and quercetin (QU) was designed to improve the in vivo therapeutic efficacy of DTX on HC through HA-CD44 mediated targeting and QU-based p-gp efflux inhibition.

Polymeric micelles as drug carriers: their lights and shadows

In this review, polymeric micelles as drug-targeting carriers are concisely explained. In the first introduction part, I describe a brief history of polymer micelle's research for drug targeting, and then I explain this review's focus. Since most other review articles concerning polymeric micelle carriers explain only what was achieved in the polymeric micelle's research, I describe this review by focusing on what was not done. In the second part, I take up three characteristics of polymeric micelle carriers by comparing their advantages and disadvantages, what was done and what was not done in the past studies, and what is easily achieved and what is difficult to be achieved with polymeric micelles. In the last part, I discuss three common problems of nano-sized drug carrier systems including polymeric micelles, and then I add a few comments on these problems.

177Lu-labeled HPMA copolymers utilizing cathepsin B and S cleavable linkers: synthesis, characterization and preliminary in vivo investigation in a pancreatic cancer model

INTRODUCTION

A major barrier to the advancement of therapeutic nanomedicines has been the non-target toxicity caused by the accumulation of the drug delivery systems in organs associated with the reticuloendothelial system, particularly the liver and spleen. Herein, we report the development of peptide based metabolically active linkers (MALs) that are enzymatically cleaved by cysteine cathepsin B and S, two proteases highly expressed in the liver and spleen. The overall goal of this approach is to utilize the MALs to lower the non-target retention and toxicity of radiolabeled drug delivery systems, thus resulting in higher diagnostic and radiotherapeutic efficacy.

METHODS

In this study three MALs (MAL0, MAL1 and MAL2) were investigated. MAL1 and MAL2 are composed of known substrates of cathepsin B and S, respectively, while MAL0 is a non-cleavable control. Both MAL1 and MAL2 were shown to undergo enzymatic cleavage with the appropriate cathepsin protease. Subsequent to conjugation to the HPMA copolymer and radiolabeling with (177)Lu, the peptide-polymer conjugates were renamed (177)Lu-metabolically active copolymers ((177)Lu-MACs) with the corresponding designations: (177)Lu-MAC0, (177)Lu-MAC1 and (177)Lu-MAC2.

RESULTS

In vivo evaluation of the (177)Lu-MACs was performed in an HPAC human pancreatic cancer xenograft mouse model. (177)Lu-MAC1 and (177)Lu-MAC2 demonstrated 3.1 and 2.1 fold lower liver retention, respectively, compared to control ((177)Lu-MAC0) at 72h post-injection. With regard to spleen retention, (177)Lu-MAC1 and (177)Lu-MAC2 each exhibited a nearly fourfold lower retention, relative to control, at the 72h time point. However, the tumor accumulation of the (177)Lu-MAC0 was two to three times greater than (177)Lu-MAC1 and (177)Lu-MAC2 at the same time point. The MAL approach demonstrated the capability of substantially reducing the non-target retention of the (177)Lu-labeled HPMA copolymers.

CONCLUSIONS

While further studies are needed to optimize the pharmacokinetics of the (177)Lu-MACs design, the ability of the MAL to significantly decrease non-target retention establishes the potential this avenue of research may have for the improvement of diagnostic and radiotherapeutic drug delivery systems.

Tumor accumulation and antitumor efficacy of docetaxel-loaded core-shell-corona micelles with shell-specific redox-responsive cross-links

A robust core-shell-corona micelle bearing redox-responsive shell-specific cross-links was evaluated as a carrier of docetaxel (DTX) for cancer therapy. The polymer micelles of poly(ethylene glycol)-b-poly(L-lysine)-b-poly(L-phenylalanine) (PEG-PLys-PPhe) in the aqueous phase provided the three distinct functional domains: the PEG outer corona for prolonged circulation, the PLys middle shell for disulfide cross-linking, and the PPhe inner core for DTX loading. The shell cross-linking was performed by the reaction of disulfide-containing cross-linkers with Lys moieties in the middle shells. The shell cross-linking did not change the micelle size or the spherical morphology. The shell cross-linked micelles exhibited enhanced serum stability. The DTX release from the DTX-loaded disulfide cross-linked micelles (DTX-SSCLM) was facilitated by increasing the concentration of glutathione (GSH). At an intracellular GSH level, DTX release was facilitated due to the reductive cleavage of the disulfide cross-links in the shell domains. The in vivo tissue distribution and tumor accumulation of the DTX-SSCLM that were labeled with a near-infrared fluorescence (NIRF) dye, Cy5.5, were monitored in MDA-MB231 tumor-bearing mice. Non-invasive real-time optical imaging results indicated that the DTX-SSCLM exhibited enhanced tumor specificity due to the prolonged stable circulation in blood and the enhanced permeation and retention (EPR) effect compared with the DTX-loaded non-cross-linked micelles (DTX-NCLM). The DTX-SSCLM exhibited enhanced therapeutic efficacy in tumor-bearing mice compared with free DTX and DTX-NCLM. The domain-specific shell cross-linking that is described in this work may serve as a useful guidance for enhancing the antitumor therapeutic efficacy of various polymer micelles and nano-aggregates.

Hydrotropic polymer micelles as versatile vehicles for delivery of poorly water-soluble drugs

Polymer micelles have been used widely for delivery of poorly water-soluble drugs. Such drug delivery, however, has been based primarily on hydrophobic interactions. For better drug loading and improved stability, hydrotropic polymer micelles were used. To develop a versatile polymer micelle for solubilizing various poorly soluble drugs, two different hydrotropic agents were examined. The solubilizing properties of two hydrotropic agents, N,N-diethylnicotinamide (DENA) and N,N-dimethylbenzamide (DMBA), in polymeric form were investigated for their ability to solubilize five drugs with low aqueous solubility covering a wide range of hydrophobicity and molecular structures. The hydrotropes were covalently linked to the hydrophobic block of a block copolymer that also had a hydrophilic poly(ethylene glycol) (PEG) block. The solubilizing capacity of the polymeric hydrotropes was compared with that of the non polymeric hydrotropes, as well as of two conventional (non hydrotropic) copolymer systems. The solubilizing capacity of polymeric hydrotropes reflects combined effects of the micellar solubilization by the hydrophobic micelle core and hydrotropic solubilization. Because of the highly localized configuration, hydrotropes in the polymeric form are more powerful solubilizers than in the monomeric (non-polymeric) solution. It is possible to produce 1~3 orders of magnitude increase in solubility with polymeric hydrotropes at the 1% (w/v) level. Of the two hydrotropic polymeric systems in this study, the DENA-based system is highly specific, whereas the DMBA-based system is a general solubilizer of hydrophobic drugs. An additional advantage of polymeric hydrotropes over the non-polymeric form is absence of high concentrations of free hydrotropes in the formulation. Solubilization vehicles based on polymeric hydrotropes are expected to provide a new and versatile means of preparing formulations for various poorly soluble drugs and drug candidates without using organic solvents. This advantage is accompanied with the inherent controlled release property of the hydrotropic polymer micelles, making them ideal for pharmaceutical formulations used in drug candidate screening and toxicology studies.

Polymeric micelles as a new drug carrier system and their required considerations for clinical trials

IMPORTANCE OF THE FIELD

A polymeric micelle is a macromolecular assembly composed of an inner core and an outer shell, and most typically is formed from block copolymers. In the last two decades, polymeric micelles have been actively studied as a new type of drug carrier system, in particular for drug targeting of anticancer drugs to solid tumors.

AREAS COVERED IN THIS REVIEW

In this review, polymeric micelle drug carrier systems are discussed with a focus on toxicities of the polymeric micelle carrier systems and on pharmacological activities of the block copolymers. In the first section, the importance of the above-mentioned evaluation of these properties is explained, as this importance does not seem to be well recognized compared with the importance of targeting and enhanced pharmacological activity of drugs, particularly in the basic studies. Then, designs, types and classifications of the polymeric micelle system are briefly summarized and explained, followed by a detailed discussion regarding several examples of polymeric micelle carrier systems.

WHAT THE READER WILL GAIN

Readers will gain a strategy of drug delivery with polymeric carriers as well as recent progress of the polymeric micelle carrier systems in their basic studies and clinical trials.

TAKE HOME MESSAGE

The purpose of this review is to achieve tight connections between the basic studies and clinical trials.

Polymeric micelles for parenteral delivery of sagopilone: physicochemical characterization, novel formulation approaches and their toxicity assessment in vitro as well as in vivo

PURPOSE

The block copolymers PEG(2000)-b-PLA(2200), PEG(2000)-b-PCL(2600) and PEG(5000)-b-PCL(5000) have been currently identified as optimal solubilizing agents for Sagopilone, a poorly water-soluble anticancer drug. In the present study, the stability, formulation feasibility and in vitro as well as in vivo toxicity were evaluated.

METHODS

Dispersion media, storage conditions, and dilutions were varied for stability assessment. The critical micelle concentration (CMC) was determined using a fluorescent probe technique. Lyophilizates and polymeric films were investigated as formulation options. Furthermore, the toxicity was studied in vitro and in vivo using HeLa/MaTu cells and a nude mouse model, respectively.

RESULTS

A drug-polymer ratio as low as 1:20 (w/w) was sufficient to solubilize Sagopilone effectively and to obtain stable dispersions (24h: drug content >or= 95%). Although the micelles exhibited a similar thermodynamic stability (CMC: 10(-7)-10(-6)M), PEG-b-PCL micelles were kinetically more stable than PEG(2000)-b-PLA(2200) (24h at 37 degrees C: drug content >or= 90% compared to 30%, respectively). Lyophilization of PEG-b-PCL micelles and storage stability of solid drug-loaded PEG(2000)-b-PLA(2200) films (3m, 6 degrees C: drug content of (95.6+/-1.4)%) were demonstrated for the first time. The high antiproliferative activity has been maintained in vitro (IC(50)<1 nM). Carrier-associated side effects have not been observed in vivo and the maximum tolerated dose of micellar Sagopilone was determined to be 6 mg/kg.

CONCLUSION

The results of this study indicate that polymeric micelles, especially PEG-b-PCL micelles, offer excellent potential for further preclinical and clinical cancer studies using Sagopilone.

Stimulus-responsive targeted nanomicelles for effective cancer therapy

Emerging nanotechnology has already developed various innovative nanomedicines. Nanomicelles, self-assemblies of block copolymers, are promising nanomedicines for targeted drug delivery and imaging. Stimulus-responsive targeted nanomicelles are designed to release drugs based on stimuli such as pH, temperature, redox potential, magnetism and ultrasound. This article will focus on recent advancements in the design of stimulus-responsive targeted nanomicelles loaded with anticancer drugs to fulfill the challenges associated with cancer cells (e.g., multidrug resistance) for the effective treatment of cancer. The significant toxicity issues and a possible future perspective associated with nanomicelles are also discussed here.