Polymeric Micelle Drug Carriers Research Articles

Cationic Dextran Stearate (Dex-St-GTMAC): Synthesis and Evaluation as Polymeric Micelles for Indomethacin Corneal Penetration.

Background Indomethacin as a non-steroidal anti-inflammatory drug (NSAID) is commonly used to treat some ocular inflammatory disorders. Unfortunately, indomethacin is a drug that is poorly soluble in water; therefore, it has low efficacy. An attractive approach is the targeted delivery of indomethacin to the cornea using cationic dextran stearate as a polymeric micelle drug carrier. Methods A dextran stearate-glycidyl trimethylammonium chloride (Dex-St-GTMAC) copolymer was prepared through the reaction of GTMAC, stearoyl chloride, and dextran. Then, Dex-St-GTMAC was characterized by Fourier transform infrared (FT-IR) spectroscopy and 1H NMR spectroscopy. Dex-St-GTMAC forms micelles in the presence of indomethacin. The prepared polymeric micelles were characterized for size, ζ-potential, drug loading, particle morphology, critical micelle concentration, and encapsulation efficiency. To study the irritation potential of the indomethacin-loaded Dex-St-GTMAC, Het-Cam and Draize tests have been performed. Prepared cationic micelles were subjected to the in vitro drug release and ex vivotrans-corneal permeation test. Results The dialysis method was used for the preparation of indomethacin-loaded micelles (10, 20, and 30%). Measurement of the particle size showed a mean diameter of 122.1 and 150.9 nm for the drug-loaded micelles. Scanning electron microscopy (SEM) images showed that the morphology of the particles is spherical. 10% formulation was chosen as the best formulation due to more surface charge and reasonable drug loading. ζ-potential measurement for the 10% drug-containing micelles showed a value of +39.1 mV. Drug loading efficiency and the encapsulation efficiency for 10% drug-containing micelles were 6.36 and 63.61%, respectively. The results of the Het-Cam and Draize tests indicated that the indomethacin-loaded Dex-St-GTMAC formulation had no toxicity to eye tissues. Based on our results, the prepared micelles (indomethacin-loaded Dex-St-GTMAC) exhibited a sustained drug release pattern compared to the control group. Indomethacin penetration from the micelles to the excised bovine cornea was 1.75-fold greater than the control (indomethacin 0.1% in phosphate-buffered saline (PBS)). Conclusions Data from the ζ-potential, SEM, drug loading capacity, and in vitro drug release studies indicated that cationic dextran stearate polymeric micelles are an appropriate carrier for the efficient penetration of indomethacin into cornea tissues.

Galactosamine-Conjugating Zwitterionic Block Copolymer for Reduction-Responsive Release and Active Targeted Delivery of Doxorubicin to Hepatic Carcinoma Cells

Nanocarriers with integrated advantage, such as excellent stealth property, active targeting function, and rapid intracellular drug release, are significant for cancer treatment. Herein, a biodegradable zwitterionic triblock copolymer containing disulfide-linked poly-ε-caprolactone and polycarboxybetaine methacrylate (PCB-SS-PCL-SS-PCB) was first synthesized and then partly modified with galactosamine (GAL) for constructing polymeric micelle drug carrier with multifunctionality. Polymeric micelles showed ultralow protein absorption in serum and obvious reduction-responsiveness in the presence of glutathione, provided by the zwitterionic polymer shell and the disulfide bond, respectively. Furthermore, active targeting of the carrier to hepatic carcinoma cells was achieved via GAL ligands on PCB shells due to their specific binding to asialoglycoprotein receptors on the cell surface. As expected, in vivo competition studies demonstrated that doxorubicin- (DOX-) loaded GAL-modified micelles have better anticancer effect in hepatic tumor-bearing mice than free DOX and nontargetable micelles. As a result, this novel multifunctional carrier provides a valuable strategy to design promising anticancer drug delivery systems for liver cancer treatment.

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.

Therapeutic efficacy of a polymeric micellar doxorubicin infused by convection-enhanced delivery against intracranial 9L brain tumor models

Convection-enhanced delivery (CED) with various drug carrier systems has recently emerged as a novel chemotherapeutic method to overcome the problems of current chemotherapies against brain tumors. Polymeric micelle systems have exhibited dramatically higher in vivo antitumor activity in systemic administration. This study investigated the effectiveness of CED with polymeric micellar doxorubicin (DOX) in a 9L syngeneic rat model. Distribution, toxicity, and efficacy of free, liposomal, and micellar DOX infused by CED were evaluated. Micellar DOX achieved much wider distribution in brain tumor tissue and surrounding normal brain tissue than free DOX. Tissue toxicity increased at higher doses, but rats treated with micellar DOX showed no abnormal neurological symptoms at any dose tested (0.1-1.0 mg/ml). Micellar DOX infused by CED resulted in prolonged median survival (36 days) compared with free DOX (19.6 days; p = 0.0173) and liposomal DOX (16.6 days; p = 0.0007) at the same dose (0.2 mg/ml). This study indicates the potential of CED with the polymeric micelle drug carrier system for the treatment of brain tumors.

Preparation and in vivo imaging of PEG-poly(L-lysine)-based polymeric micelle MRI contrast agents

A polymeric micelle drug carrier system was applied to the targeting of an MRI (magnetic resonance imaging) contrast agent. A block copolymer, PEG- b-poly(L-lysine), was used for conjugation of gadolinium ions through chelating moieties, DOTA. The DOTA moieties were successfully conjugated to all primary amine groups of the lysine residues. The obtained block copolymer, PEG- b-poly(L-lysine-DOTA), formed a polymeric micelle. The polymeric micelle structure was maintained even after partial gadolinium chelation (∼ 40%) to the DOTA moieties. The prepared polymeric micelle MRI contrast agent was injected into a mouse tail vein at a dose of 0.05 mmol Gd/kg. The polymeric micelle-based MRI contrast agent exhibited stable blood circulation. A considerable amount (6.1 ± 0.3% of ID/g of the polymeric micelle) was found to accumulate at solid tumors 24 h after intravenous injection by means of the EPR effect. An MRI analysis revealed that the signal intensity of the tumor was enhanced 2.0-fold by the use of this contrast agent.

What are determining factors for stable drug incorporation into polymeric micelle carriers? Consideration on physical and chemical characters of the micelle inner core

Partially benzyl-esterified poly(ethylene glycol)- b-poly(aspartic acid) (PEG-P(Asp(Bzl))) having different hydrophobic inner-core structure were synthesized and analyzed. We obtained two types of the block copolymers for formation of polymeric micelle drug carriers; one had an amide-bond ratio of 1:3 (α/β) in the poly(aspartic acid) residues through alkaline hydrolysis, and the other one had 100% of the α-amide through acid hydrolysis. Subsequently, we prepared partially benzyl-esterified block copolymers with an esterification degree of 40 to 100% in the aspartic acid residue. Regarding camptothecin (CPT) incorporation into polymeric micelles, we evaluated effects that block copolymers’ inner hydrophobic block structures have on CPT behavior. Regarding CPT-incorporation stability, PEG-P(α,β-Asp(Bzl) block copolymers with the α and β-amides were found to exhibit higher CPT-incorporation stability. Using fluorescent probes, we evaluated the properties of inner-core blocks such as hydrophobicity and mobility/rigidity, and the findings implied that stable CPT incorporation could be obtained by an adequate balance between the micelle inner core's hydrophobicity and the micelle inner core's rigidity or between the micelle inner core's hydrophobicity and steric configuration of the hydrophobic block chain.

In Vivo Antitumor Activity of the Folate-Conjugated pH-Sensitive Polymeric Micelle Selectively Releasing Adriamycin in the Intracellular Acidic Compartments

Cancer treatment efficacy and safety of the environmentally sensitive polymeric micelle drug carriers were significantly increased by optimizing the number of ligands on their surface. These micelles were designed to target the cancerous tumors through the interaction between folate and its receptors that overexpress on the cancer cell membrane while achieving pH-controlled drug release in the intracellular acidic compartments such as endosomes and lysosomes. In order to elucidate the effects of folate on cytotoxicity, biodistribution, anticancer activity, and pharmacological properties, folate concentration on the surface of the micelles was controlled by precise synthesis of two different amphiphilic block copolymers that self-assemble into spherical micelles, folate-poly(ethylene glycol)-poly(aspartate-hydrazone-adriamycin) with gamma-carboxylic acid activated folate and methoxy-poly(ethylene glycol)-poly(aspartate-hydrazone-adriamycin) without folate. It is of significance that, although folate conjugation induced an extremely small change in tumor accumulation of the micelles, folate-conjugated micelles showed lower in vivo toxicity and higher antitumor activity over a broad range of the dosage from 7.50 to 26.21 mg/kg, which was 5-fold broader than free drugs.

Intelligent thermoresponsive polymeric micelles for targeted drug delivery

Nano-order sized supramolecular assemblies called polymeric micelles possess two-separated phase structure; a hydrated hydrophilic outer shell provides their highly structural stabilities in aqueous media and a hydrophobic inner core acts as a drug loading container. First anticancer polymeric micelle carrier systems showed a selective accumulation at solid tumor tissues and a subsequent in vivo anticancer activity. Recently, stimuli-responsive polymeric micelles have been designed as the next generation of micelle systems for application in selective drug release at target sites by physical and/or chemical signals. We suggested a concept using thermoresponsive polymeric micelle drug carriers in conjunction with local heating systems for multi-targeting therapeutic systems to achieve effective cancer chemotherapy with fewer side effects. The present review article mainly focuses on strategy and molecular design of thermoresponsive polymeric micelles and discusses their potential for an intelligent targeted drug carrier system with some examples containing anti-cancer drugs.

Multifunctional polymeric micelles with folate-mediated cancer cell targeting and pH-triggered drug releasing properties for active intracellular drug delivery

A new type of multifunctional polymeric micelle drug carrier for active intracellular drug delivery was prepared and characterized in this study. The micelle is a nano-supramolecular assembly with a spherical core-shell structure, and its surface and core were modified with piloting molecules for cancer cells and pH-sensitive drug binding linkers for controlled drug release, respectively. In order to prepare such micelles, self-assembling amphiphilic block copolymers, folate-poly(ethylene glycol)-poly(aspartate hydrazone adriamycin) [Fol-PEG-P(Asp-Hyd-ADR)], were specially designed and synthesized by installing a molecular promoter to enhance intracellular transport, folate (Fol), at the end of the shell-forming PEG chain and conjugating the anticancer drug, adriamycin (ADR), to the side chain of the core-forming PAsp segment through an acid-sensitive hydrazone bond. Because folate-binding proteins (FBP) are selectively overexpressed on the cancer cell membranes, the folate-bound micelles (FMA) can be guided to the cancer cells in the body, and after the micelles enter the cells, hydrazone bonds are cleaved by the intracellular acidic environment (pH 5-6) so that the drug release profile of the micelles is controlled pH-dependently. In this regard, FBP-binding selectivity of the prepared FMA was evaluated by surface plasmon resonance (SPR) measurements. The tetrazolium dye method (MTT assay) using human pharyngeal cancer cells (KB cell) revealed that FMA significantly improved cell growth inhibitory activity in spite of a short exposure time due to the selective and strong interaction between folate molecules and their receptors. Subsequent flow cytometric analysis showed that cellular uptake of FMA significantly increased. Consequently, these findings would provide one of the most effective approaches for cancer treatment using intracellular environment-targeting supramolecular drug carriers.

Preparation and Biological Characterization of Polymeric Micelle Drug Carriers with Intracellular pH-Triggered Drug Release Property: Tumor Permeability, Controlled Subcellular Drug Distribution, and Enhanced in Vivo Antitumor Efficacy

A novel intracellular pH-sensitive polymeric micelle drug carrier that controls the systemic, local, and subcellular distributions of pharmacologically active drugs has been developed in this study. The micelles were prepared from self-assembling amphiphilic block copolymers, poly(ethylene glycol)-poly(aspartate hydrazone adriamycin), in which the anticancer drug, adriamycin, was conjugated to the hydrophobic segments through acid-sensitive hydrazone linkers. By this polymer design, the micelles can stably preserve drugs under physiological conditions (pH 7.4) and selectively release them by sensing the intracellular pH decrease in endosomes and lysosomes (pH 5-6). In vitro and in vivo studies show that the micelles have the characteristic properties, such as an intracellular pH-triggered drug release capability, tumor-infiltrating permeability, and effective antitumor activity with extremely low toxicity. The acquired experimental data clearly elucidate that the optimization of both the functional and structural features of polymeric micelles provides a promising formulation not only for the development of intracellular environment-sensitive supramolecular devices for cancer therapeutic applications but also for the future treatment of intractable cancers with limited vasculature.

Polymeric micelle drug carrier systems: PEG-PAsp(Dox) and second generation of micellar drugs.

Polymeric micelles are one of the most refined and promising modalities of macromolecular drug delivery systems , and show unique disposition characteristics in the body suitable for the drug targeting (e.g., prolonged blood circulation and significant tumor accumulation as described in earlier chapter) . Like the other promising modalities (i.e., watersoluble polymers and long-circulating liposomes), the polymeric micelle carrier systems might possess several advantages such as (1) the applicability to a variety of therapeutic agents (e.g., hydrophobic compounds, metal complexes and charged macromolecules such as polypeptides and nucleic acids), (2) unnecessariness of chemical structure

Reduction of the side effects of an antitumor agent, KRN5500, by incorporation of the drug into polymeric micelles.

For intravenous (i.v.) injection of a water‐insoluble antitumor drug, KRN5500, we have successfully incorporated KRN5500 into polymeric micelles. In the present study, in vitro and in vivo antitumor activity against several human tumor cell lines and toxicity in mice of polymeric micelles incorporating KRN5500 (KRN/m) were evaluated in comparison with those of the prototype KRN5500. KRN/m was found to express similar antitumor activity to KRN5500 in the in vitro and in vivo systems. However, the vascular damage and liver focal necrosis observed with KRN5500 i.v. injection were not seen when KRN/m was administered i.v. Therefore, we expect that KRN/m will be superior to KRN5500 for clinical use and that the methodology of polymeric micelle drug carrier systems can be applied to other water‐insoluble drugs.