Core-crosslinked Polymeric Micelles Research Articles

Versatile Click Linker Enabling Native Peptide Release from Nanocarriers upon Redox Trigger.

Nanocarriers have shown their ability to extend the circulation time of drugs, enhance tumor uptake, and tune drug release. Therapeutic peptides are a class of drug compounds in which nanocarrier-mediated delivery can potentially improve their therapeutic index. To this end, there is an urgent need for orthogonal covalent linker chemistry facilitating the straightforward on-the-resin peptide generation, nanocarrier conjugation, as well as the triggered release of the peptide in its native state. Here, we present a copper-free clickable ring-strained alkyne linker conjugated to the N-terminus of oncolytic peptide LTX-315 via standard solid-phase peptide synthesis (SPPS). The linker contains (1) a recently developed seven-membered ring-strained alkyne, 3,3,6,6-tetramethylthiacycloheptyne sulfoximine (TMTHSI), (2) a disulfide bond, which is sensitive to the reducing cytosolic and tumor environment, and (3) a thiobenzyl carbamate spacer enabling release of the native peptide upon cleavage of the disulfide via 1,6-elimination. We demonstrate convenient "clicking" of the hydrophilic linker-peptide conjugate to preformed pegylated core-cross-linked polymeric micelles (CCPMs) of 50 nm containing azides in the hydrophobic core under aqueous conditions at room temperature resulting in a loading capacity of 8 mass % of peptide to polymer (56% loading efficiency). This entrapment of hydrophilic cargo into/to a cross-linked hydrophobic core is a new and counterintuitive approach for this class of nanocarriers. The release of LTX-315 from the CCPMs was investigated in vitro and rapid release upon exposure to glutathione (within minutes) followed by slower 1,6-elimination (within an hour) resulted in the formation of the native peptide. Finally, cytotoxicity of LTX CCPMs as well as uptake of sulfocyanine 5-loaded CCPMs was investigated by cell culture, demonstrating successful tumor cell killing at concentrations similar to that of the free peptide treatment.

Mechanistic Study on the Degradation of Hydrolysable Core-Crosslinked Polymeric Micelles.

Core-crosslinked polymeric micelles (CCPMs) are an attractive class of nanocarriers for drug delivery. Two crosslinking approaches to form CCPMs exist: either via a low-molecular-weight crosslinking agent to connect homogeneous polymer chains with reactive handles or via cross-reactive handles on polymers to link them to each other (complementary polymers). Previously, CCPMs based on methoxy poly(ethylene glycol)-b-poly[N-(2-hydroxypropyl) methacrylamide-lactate] (mPEG-b-PHPMAmLacn) modified with thioesters were crosslinked via native chemical ligation (NCL, a reaction between a cysteine residue and thioester resulting in an amide bond) using a bifunctional cysteine containing crosslinker. These CCPMs are degradable under physiological conditions due to hydrolysis of the ester groups present in the crosslinks. The rapid onset of degradation observed previously, as measured by the light scattering intensity, questions the effectiveness of crosslinking via a bifunctional agent. Particularly due to the possibility of intrachain crosslinks that can occur using such a small crosslinker, we investigated the degradation mechanism of CCPMs generated via both approaches using various analytical techniques. CCPMs based on complementary polymers degraded slower at pH 7.4 and 37 °C than CCPMs with a crosslinker (the half-life of the light scattering intensity was approximately 170 h versus 80 h, respectively). Through comparative analysis of the degradation profiles of the two different CCPMs, we conclude that partially ineffective intrachain crosslinks are likely formed using the small crosslinker, which contributed to more rapid CCPM degradation. Overall, this study shows that the type of crosslinking approach can significantly affect degradation kinetics, and this should be taken into consideration when developing new degradable CCPM platforms.

Tuning the Cross-Linking Density and Cross-Linker in Core Cross-Linked Polymeric Micelles and Its Effects on the Particle Stability in Human Blood Plasma and Mice.

Core cross-linked polymeric micelles (CCPMs) are designed to improve the therapeutic profile of hydrophobic drugs, reduce or completely avoid protein corona formation, and offer prolonged circulation times, a prerequisite for passive or active targeting. In this study, we tuned the CCPM stability by using bifunctional or trifunctional cross-linkers and varying the cross-linkable polymer block length. For CCPMs, amphiphilic thiol-reactive polypept(o)ides of polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine) [pSar-b-pCys(SO2Et)] were employed. While the pCys(SO2Et) chain lengths varied from Xn = 17 to 30, bivalent (derivatives of dihydrolipoic acid) and trivalent (sarcosine/cysteine pentapeptide) cross-linkers have been applied. Asymmetrical flow field-flow fraction (AF4) displayed the absence of aggregates in human plasma, yet for non-cross-linked PM and CCPMs cross-linked with dihydrolipoic acid at [pCys(SO2Et)]17, increasing the cross-linking density or the pCys(SO2Et) chain lengths led to stable CCPMs. Interestingly, circulation time and biodistribution in mice of non-cross-linked and bivalently cross-linked CCPMs are comparable, while the trivalent peptide cross-linkers enhance the circulation half-life from 11 to 19 h.

Well-Defined Shell-Sheddable Core-Crosslinked Micelles with pH and Oxidation Dual-Response for On-Demand Drug Delivery.

Micellar-nanocarrier-based drug delivery systems possessing characteristics such as an excellent circulation stability, inhibited premature release and on-demand site-specific release are urgently needed for enhanced therapeutic efficacy. Therefore, a novel kind of shell-sheddable core-crosslinked polymeric micelles with pH and oxidation dual-triggered on-demand drug release behavior was facilely constructed. The multifunctional micelles were self-assembled from a carefully designed amphiphilic triblock PEGylated polyurethane (PEG-acetal-PUBr-acetal-PEG) employing an acid-labile acetal linker at the hydrophilic-hydrophobic interface and pendant reactive bromo-containing polyurethane (PU) as the hydrophobic block, followed by a post-crosslinking via oxidation-cleavable diselenide linkages. These well-defined micelles exhibited an enhanced structural stability against dilution, achieved through the incorporation of diselenide crosslinkers. As expected, they were found to possess dual pH- and oxidation-responsive dissociation behaviors when exposure to acid pH (~5.0) and 50 mM H2O2 conditions, as evidenced using dynamic light-scattering (DLS) and atomic force microscopy (AFM) analyses. An in vitro drug release investigation showed that the drug indomethacin (IND) could be efficiently encapsulated in the micelles, which demonstrated an inhibited premature release compared to the non-crosslinked ones. It is noteworthy that the resulting micelles could efficiently release entrapped drugs at a fast rate in response to either pH or oxidation stimuli. Moreover, the release could be significantly accelerated in the presence of both acid pH and oxidation conditions, relative to a single stimulus, owing to the synergetic degradation of micelles through pH-induced dePEGylation and oxidation-triggered decrosslinking processes. The proposed shell-sheddable core-crosslinked micelles with a pH and oxidation dual-response could be potential candidates as drug carriers for on-demand drug delivery.

Complex Structures Made Simple - Continuous Flow Production of Core Cross-Linked Polymeric Micelles for Paclitaxel Pro-Drug-Delivery.

Translating innovative nanomaterials to medical products requires efficient manufacturing techniques that enable large-scale high-throughput synthesis with high reproducibility. Drug carriers in medicine embrace a complex subset of tasks calling for multifunctionality. Here, the synthesisof pro-drug-loaded core cross-linked polymeric micelles (CCPMs) in a continuous flow processis reported, which combines the commonly separated steps of micelle formation, core cross-linking, functionalization, and purification into a single process. Redox-responsive CCPMs are formed from thiol-reactive polypept(o)ides of polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine) and functional cross-linkers based on dihydrolipoic acid hydrazide for pH-dependent release of paclitaxel. The precisely controlled microfluidic process allows the production of spherical micelles (Dh = 35nm) with low polydispersity values (PDI < 0.1) while avoiding toxic organic solvents and additives with unfavorable safety profiles. Self-assembly and cross-linking via slit interdigital micromixers produces 350-700mg of CCPMs/h per single system, while purification by online tangential flow filtration successfully removes impurities (unimer ≤ 0.5%). The formed paclitaxel-loaded CCPMs possess the desired pH-responsive release profile, display stable drug encapsulation, an improved toxicity profile compared to Abraxane (a trademark of Bristol-Myers Squibb), and therapeutic efficiency in the B16F1-xenotransplanted zebrafish model. The combination of reactive polymers, functional cross-linkers, and microfluidics enables the continuous-flow synthesis of therapeutically active CCPMs in a single process.

A New Class of Tunable Acid-Sensitive Linkers for Native Drug Release Based on the Trityl Protecting Group.

Core-cross-linked polymeric micelles (CCPMs) are a promising nanoparticle platform due to favorable properties such as their long circulation and tumor disposition exploiting the enhanced permeability and retention (EPR) effect. Sustained release of covalently linked drugs from the hydrophobic core of the CCPM can be achieved by a biodegradable linker that connects the drug and the core. This study investigates the suitability of trityl-based linkers for the design of acid-triggered native active pharmaceutical ingredient (API) release from CCPMs. Trityl linker derivatives with different substituent patterns were synthesized and conjugated to model API compounds such as DMXAA-amine, doxorubicin, and gemcitabine, and their release kinetics were studied. Hereafter, API release from CCPMs based on mPEG-b-pHPMAmLac block copolymers was investigated. Variation of the trityl substitution pattern showed tunability of the API release rate from the trityl-based linker with t1/2 varying from <1.0 to 5.0 h at pH 5.0 and t1/2 from 6.5 to >24 h at pH 7.4, all at 37 °C. A clear difference in release kinetics was found between gemcitabine and doxorubicin, with gemcitabine showing no detectable release for 72 h at pH 5.0 and doxorubicin showing a t1/2 of less than 1 h. Based on these findings, we show that the reaction mechanism of trityl deprotection plays an important role in the API release kinetics. The first step in this mechanism, which is protonation of the trityl-bound amine, is pKa-dependent, which explains the difference in release rate. In conclusion, acid-sensitive and tunable trityl linkers are highly promising for the design of linker–API conjugates and for their use in CCPMs.

Profiling target engagement and cellular uptake of cRGD-decorated clinical-stage core-crosslinked polymeric micelles

Polymeric micelles are increasingly explored for tumor-targeted drug delivery. CriPec® technology enables the generation of core‐crosslinked polymeric micelles (CCPMs) based on thermosensitive (mPEG-b-pHPMAmLacn) block copolymers, with high drug loading capacity, tailorable size, and controlled drug release kinetics. In this study, we decorated clinical-stage CCPM with the αvβ3 integrin-targeted cyclic arginine-glycine-aspartic acid (cRGD) peptide, which is one of the most well-known active targeting ligands evaluated preclinically and clinically. Using a panel of cell lines with different expression levels of the αvβ3 integrin receptor and exploring both static and dynamic incubation conditions, we studied the benefit of decorating CCPM with different densities of cRGD. We show that incubation time and temperature, as well as the expression levels of αvβ3 integrin by target cells, positively influence cRGD-CCPM uptake, as demonstated by immunofluorescence staining and fluorescence microscopy. We demonstrate that even very low decoration densities (i.e., 1 mol % cRGD) result in increased engagement and uptake by target cells as compared to peptide-free control CCPM, and that high cRGD decoration densities do not result in a proportional increase in internalization. In this context, it should be kept in mind that a more extensive presence of targeting ligands on the surface of nanomedicines may affect their pharmacokinetic and biodistribution profile. Thus, we suggest a relatively low cRGD decoration density as most suitable for in vivo application.Graphical

Stability-tunable core-crosslinked polymeric micelles based on an imidazole-bearing block polymer for pH-responsive drug delivery

Polymeric micelles from block copolymers have gained increasing attention in cancer drug delivery. However, the fabrication of polymeric micelles that are stable in biological fluids and unstable at tumor sites remains a principal challenge. To achieve the tunable stability for the polymeric micelles, Zn coordination-induced core-crosslinked polymeric micelles have been proposed and confirmed. Herein, a block copolymer bearing imidazole pendants is synthesized which is capable of self-assembling into polymeric micelles in water. After core-crosslinking, it can be found that the critical micelle concentration (CMC) of the core-crosslinked polymeric micelles is significantly lower than that of non-crosslinked polymeric micelles. Particularly, the drug-loaded core-crosslinked polymeric micelles are fragile and easily affected by the slightly acidic environments, which makes it possible to turn the polymeric micelles back to hydrophilic polymers and therefore disassemble micelles to unload cargoes. The drug-loaded core-crosslinked polymeric micelles display adequate toxicity as a result of their low IC50 value of 3.713 ± 0.166 μg/mL. Collectively, Zn coordination-induced core-crosslinked polymeric micelles offer a design idea for practicable drug delivery system in cancer therapy.

Acoustic Cluster Therapy (ACT®) enhances accumulation of polymeric micelles in the murine brain

The restrictive nature of the blood-brain barrier (BBB) prevents efficient treatment of many brain diseases. Focused ultrasound in combination with microbubbles has shown to safely and transiently increase BBB permeability. Here, the potential of Acoustic Cluster Therapy (ACT®), a microbubble platform specifically engineered for theranostic purposes, to increase the permeability of the BBB and improve accumulation of IRDye® 800CW-PEG and core-crosslinked polymeric micelles (CCPM) in the murine brain, was studied. Contrast enhanced magnetic resonance imaging (MRI) showed increased BBB permeability in all animals after ACT®. Near infrared fluorescence (NIRF) images of excised brains 1 h post ACT® revealed an increased accumulation of the IRDye® 800CW-PEG (5.2-fold) and CCPM (3.7-fold) in ACT®-treated brains compared to control brains, which was retained up to 24 h post ACT®. Confocal laser scanning microscopy (CLSM) showed improved extravasation and penetration of CCPM into the brain parenchyma after ACT®. Histological examination of brain sections showed no treatment related tissue damage. This study demonstrated that ACT® increases the permeability of the BBB and enhances accumulation of macromolecules and clinically relevant nanoparticles to the brain, taking a principal step in enabling improved treatment of various brain diseases.

Core Cross-Linked Polymeric Micelles for Specific Iron Delivery: Inducing Sterile Inflammation in Macrophages.

Iron is an essential co-factor for cellular processes. In the immune system, it can activate macrophages and represents a potential therapeutic for various diseases. To specifically deliver iron to macrophages, iron oxide nanoparticles are embedded in polymeric micelles of reactive polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine). Upon surface functionalization via dihydrolipoic acid, iron oxide cores act as crosslinker themselves and undergo chemoselective disulfide bond formation with the surrounding poly(S-ethylsulfonyl-l-cysteine) block, yielding glutathione-responsive core cross-linked polymeric micelles (CCPMs). When applied to primary murine and human macrophages, these nanoparticles display preferential uptake, sustained intracellular iron release, and induce a strong inflammatory response. This response is also demonstrated in vivo when nanoparticles are intratracheally administered to wild-type C57Bl/6N mice. Most importantly, the controlled release concept to deliver iron oxide in redox-responsive CCPMs induces significantly stronger macrophage activation than any other iron source at identical iron levels (e.g., Feraheme), directing to a new class of immune therapeutics.

Lyophilization stabilizes clinical-stage core-crosslinked polymeric micelles to overcome cold chain supply challenges.

CriPec technology enables the generation of drug-entrapped biodegradable core-crosslinked polymeric micelles (CCPM) with high drug loading capacity, tailorable size, and drug release kinetics. Docetaxel (DTX)-entrapped CCPM, also referred to as CPC634, have demonstrated favorable pharmacokinetics, tolerability, and enhanced tumor uptake in patients. Clinical efficacy evaluation is ongoing. CPC634 is currently stored (shelf life>5years) and shipped as a frozen aqueous dispersion at temperatures below -60°C, in order to prevent premature release of DTX and hydrolysis of the core-crosslinks. Consequently, like other aqueous nanomedicine formulations, CPC634 relies on cold chain supply, which is unfavorable for commercialization. Lyophilization can help to bypass this issue. Freeze-drying methodology for CCPM was developed by employing CPC634 as a model formulation, and sucrose and trehalose as cryoprotectants. We studied the residual moisture content and reconstitution behavior of the CPC634 freeze-dried cake, as well as the size, polydispersity index, morphology, drug retention, and release kinetics of reconstituted CPC634. Subsequently, the freeze-drying methodology was validated in an industrial setting, yielding a CPC634 freeze-dried cake with a moisture content of less than 0.1wt%. It was found that trehalose-cryoprotected CPC634 could be rapidly reconstituted in less than 5min at room temperature. Critical quality attributes such as size, morphology, drug retention, and release kinetics of trehalose-cryoprotected freeze-dried CPC634 upon reconstitution were identical to those of non-freeze-dried CPC634. Our findings provide proof-of-concept for the lyophilization of drug-containing CCPM and our methodology is readily translatable to large-scale manufacturing for future commercialization.

Optical imaging of the whole-body to cellular biodistribution of clinical-stage PEG-b-pHPMA-based core-crosslinked polymeric micelles

Core-crosslinked polymeric micelles (CCPM) based on PEG-b-pHPMA-lactate are clinically evaluated for the treatment of cancer. We macroscopically and microscopically investigated the biodistribution and target site accumulation of CCPM. To this end, fluorophore-labeled CCPM were intravenously injected in mice bearing 4T1 triple-negative breast cancer (TNBC) tumors, and their localization at the whole-body, tissue and cellular level was analyzed using multimodal and multiscale optical imaging. At the organism level, we performed non-invasive 3D micro-computed tomography-fluorescence tomography (μCT-FLT) and 2D fluorescence reflectance imaging (FRI). At the tissue and cellular level, we performed extensive immunohistochemistry, focusing primarily on cancer, endothelial and phagocytic immune cells. The CCPM achieved highly efficient tumor targeting in the 4T1 TNBC mouse model (18.6 %ID/g), with values twice as high as those in liver and spleen (9.1 and 8.9 %ID/g, respectively). Microscopic analysis of tissue slices revealed that at 48 h post injection, 67% of intratumoral CCPM were localized extracellularly. Phenotypic analyses on the remaining 33% of intracellularly accumulated CCPM showed that predominantly F4/80+ phagocytes had taken up the nanocarrier formulation. Similar uptake patterns were observed for liver and spleen. The propensity of CCPM to primarily accumulate in the extracellular space in tumors suggests that the anticancer efficacy of the formulation mainly results from sustained release of the chemotherapeutic payload in the tumor microenvironment. In addition, their high uptake by phagocytic immune cells encourages potential use for immunomodulatory anticancer therapy. Altogether, the beneficial biodistribution, efficient tumor targeting and prominent engagement of PEG-b-pHPMA-lactate-based CCPM with key cell populations underline the clinical versatility of this clinical-stage nanocarrier formulation.

Abstract 122: Targeting forward and reverse EphB4/EFNB2 signaling by a peptide with dual functions

Although chloroquine administration in vivo following haemorrhage in mice decreases tumour necrosis factor-alpha (TNF-alpha) release by macrophage (M phi), the mechanism remains unknown. To study this, peritoneal M phi (pM phi) from unmanipulated, sham-operated and post-haemorrhage mice were isolated, treated with 0.13 mg/ml chloroquine for 2 hr, and then stimulated with lipopolysaccharide (LPS) for 48 hr. Pretreatment of pM phi from various groups of mice with chloroquine resulted in 75-90% inhibition of TNF-alpha release, determined by bioassay. Total RNA was isolated from pM phi and murine M phi-derived cell lines (P388D1 and RAW 264.7), stimulated with LPS for 0.5 or 1 hr, respectively, and Northern blot analysis for TNF-alpha mRNA performed. Chloroquine inhibited TNF-alpha mRNA expression without interfering with mRNA stability, suggesting that this agent reduces M phi TNF-alpha release by disrupting TNF-alpha gene transcription.

Abstract AP21: A NOVEL TARGET FOR OVERCOMING ADAPTIVE RESISTANCE TO ANTI-ANGIOGENIC THERAPY IN OVARIAN CANCER

Abstract Anti-angiogenic therapy such as anti-VEGF antibody (AVA) has been being increasingly applied in patients with ovarian cancer, while vast majority developed adaptive resistance, highlighting the need for new therapies. We have screened a cohort of patients with high-grade serous cancer (HGSC) using cDNA-genomic array and immunohistochemistry. Our results indicated that p130cas [Crk-associated substrate], a central node in FAK/Src-mediated angiogenesis, was significantly upregulated in tumor-associated vascular endothelium, and the clinical analysis showed that HGSC patients with increased vascular p130cas have significantly shorter disease-progression survival than those with lower vascular p130cas levels. Our cell-based studies showed that AVA treatment in endothelial cells led to internalization of a 100-kD fragment of VEGFR2, which was released by caspase-10 cleavage from membrane-tethered VGFR2. This 100-kD form of VEGFR2 bound with TNKS1BP1 (a tankyrase-1-binding protein involved in p53-mediated cell cycle arrest) and internalized into LC3-tagged autophagosomes or translocated into nucleus to initiate cell death. Furthermore, the gene ablation of p130cas with CRISPR/CAS9 in endothelial cells that were originally resistant to AVA therapy re-sensitized them to AVA treatment. Our in vivo studies on targeting vascular p130cas with host-specific siRNA showed a robust inhibition of tumor growth and progression in orthotopic HGSC tumors through initiating autophagy-associated cell death in tumor-associated endothelial cells. To functionally characterize role of vascular p130cas in angiogenesis, we established the p130casflox/flox-Tie2Cre genomic-engineered mice (GEM) model. Using the ID8 syngeneic model, we found that depletion of vascular p130cas diminished resistance to AVA therapy and compromised angiogenesis by inducing elevated VEGFR2/TNKS1BP1 in autophagosomes and nucleus of tumor-associated endothelial cells, which were followed by cell death. To further explore the therapeutic potential of blocking tumor-associated vascular p130cas as a novel anti-angiogenic strategy, we have constituted a cell-permeable, peptide-nanoparticle complex using a p130cas antagonist encapsulated with biodegradable, long-circulating, core-crosslinked polymeric micelles (CCPM). This CCPM-p130cas antagonist contains a mutated Src-binding domain and is linked with Arg-Gly-Asp (RGD) peptide, which specifically targets angiogenic endothelial cells. We also performed the cell-based studies to show that this CCPM-p130cas antagonist is able to bind to the FAK and Src complex with high affinity and effectively block FAK/Src mediated angiogenic property in endothelial cells. Ongoing studies are focused on investigating the therapeutic efficacy and mechanism of actions for RGD-CCPM-p130cas antagonist as a novel anti-angiogenic therapy to overcome adaptive resistance occurred in patients with HGSC. In summary, our studies provided new knowledge regarding the pivotal role of vascular p130cas in tumor-associated endothelial vasculature, and the critical pre-clinical evidences for applying the RGD-CCPM-p130cas antagonist as a novel therapeutic for treatment of ovarian cancer. Citation Format: Yunfei Wen, Alpa M Nick, G Lopez-Berestein, Gary E Gallick, Robert L Coleman Robert , Mien-Chie Hung, and Anil K Sood. A NOVEL TARGET FOR OVERCOMING ADAPTIVE RESISTANCE TO ANTI-ANGIOGENIC THERAPY IN OVARIAN CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr AP21.

Systematic investigation to the effects of near-infrared light exposure on polymeric micelles of poly(ethylene glycol)-block-poly(styrene-alt-maleic anhydride) loaded with indocyanine green

The use of diselenide core cross-linked polymeric micelles assisted with indocyanine green (ICG) as a near-infrared (NIR)-responsive drug delivery system was known to be promising in terms of well-controlled release as well as biocompatibility. However, we must note that the effect of NIR exposure is not simply promoting cleavage of Se–Se bonds. In this work, we report a systematic investigation to the effect of NIR light exposure on the polymeric micelles of poly(ethylene glycol)-block-poly(styrene-alt-maleic anhydride) loaded with ICG. Diselenide core-cross-linked micelles and non-cross-linked micelles were prepared for the investigation. The results showed that the reactive oxygen species (ROS) produced from ICG not only reacted with diselenide bonds but also attacked poly(ethylene glycol) chains, resulting in the polymer degradation. The polymer degradation appeared to be continuous even for 36 h after NIR exposure was stopped, as evidenced in DLS, GPC, and TEM measurements. This study provides insight into essential parameters which should be considered in designing ROS-responsive drug delivery systems based on polymeric micelles.

Preparation and characterization of glutathione-responsive polymeric micelles functionalized with core cross-linked disulfide linkage for curcumin delivery

Conventional self-assembled polymeric micelles typically lose their loaded drugs after systemic administration. To resolve this issue, the aim of the present study was to develop a novel polymer, methoxy-poly (ethylene glycol)-block-poly (d, l-lactic acid) grafted with four lipoic acids (mPEG-PLA-(LA)4), to prepare curcumin-loaded core cross-linked polymeric micelles (CCM). Nitrogen and alkalescent buffer (pH 8.5) were beneficial for cross-linking, and the cross-linking was nearly complete within 30 min. The micelle preparation parameters were optimized through both a single-factor experiment and orthogonality test. The choice of cryoprotector had the most important effect on micelle solution reconstruction and almost challenged our perceptions about cryoprotector. In addition the drug loading capacity greatly affected the stability of micelles. Moreover, a method for determining the cross-linking density was established, and the result of gel permeation chromatography indirectly demonstrated that dozens of polymers had successfully formed CCM. The CCM significantly enhanced stability under non-reductive conditions and could be reversibly broken in a reductive environment. Curcumin-loaded CCM also showed glutathione-response cytotoxicity to cancer cells. Overall, this fundamental study suggests CCM as a potential carrier for achieving improved controlled drug delivery.

A network of porous carbon/ZnCo2O4 nanotubes derived from shell-hybridized worm-like micelles for lithium storage

In this work, hybrid carbon/ZnxCo3−xO4 (ZCO) nanotube (HCNT) networks have been efficiently prepared, using highly pure, uniform and long core-crosslinked polymeric worm-like micelles (PWs) with a small diameter and a 3D interacting shell as the 1D template.

A new method for the determination of total and released docetaxel from docetaxel-entrapped core-crosslinked polymeric micelles (CriPec®) by LC–MS/MS and its clinical application in plasma and tissues in patients with various tumours

A sensitive, high-performance liquid chromatographic method was developed and validated, for determination of docetaxel from docetaxel-entrapped core-crosslinked polymeric micelles (CriPec®) in human potassium EDTA plasma and released docetaxel to support the clinical development of Cripec® docetaxel. CriPec® docetaxel is a novel formulation of docetaxel – covalently conjugated via a linker agent in a nanoparticle. The analytical characterization of CriPec® docetaxel comprises determination of both released and total docetaxel, the first being the already deconjugated docetaxel, whereas total is representative of all docetaxel (deconjugated as well as CriPec® nanoparticle conjugated material). Total docetaxel was determined by incubation of human plasma with 0.5 M ammonium acetate buffer pH 7.4 for 3-days at 37 °C. Hereafter, a liquid-liquid extraction with 1-chlorobutane was performed using paclitaxel as internal standard. Released docetaxel from CriPec® docetaxel nanoparticles was determined in human plasma stabilized with 5 M ammonium acetate, pH 5.0. Hereafter, a liquid-liquid extraction with 1-chlorobutane was performed using docetaxel-d5 in acetonitrile as internal standard. Released docetaxel and its internal standard were eluted. The validated ranges for total docetaxel were 2,000–100,000 ng/mL for the high concentrations and 2–500 ng/mL for the low concentrations and 0.250–100 ng/mL for released docetaxel.In conclusion the newly developed assay met the required standards for validation and was applied successfully to support pharmacokinetic analysis in both serum and tissue in patients treated with Cripec®.

High systemic availability of core-crosslinked polymeric micelles after subcutaneous administration

Covalent entrapment of drug molecules within core-crosslinked polymeric micelles (CCPM) represents an attractive approach to improve their therapeutic index. As an alternative to the most commonly employed intravenous (i.v.) route, subcutaneous (s.c.) administration offers the possibility of self-administration and thereby may reduce healthcare costs. The aim of this work was to assess the pharmacokinetic profile and systemic availability of drug-containing CCPM following s.c. injection. We here derivatised dexamethasone (DMS) with three different linkers, which enabled covalent attachment of this drug to the core of CCPM. The obtained DMS-containing CCPM exhibited varying drug release kinetics in vitro. Remarkably, a single dose of DMS-containing CCPM resulted in high systemic availability of about 30% following s.c. injection into the flank of healthy mice, as evidenced by an AUC between 26–37% relative to the AUC attained following i.v. injection. Although different linkers resulted in moderate variations in pharmacokinetic parameters, the overall pharmacokinetic profiles of these i.v. or s.c. administered nanomedicines were not substantially different. Next to DMS, we covalently attached paclitaxel (PTX) to the core of CCPM. Similarly, a single s.c. dose of PTX-containing CCPM resulted in high systemic availability of about 40% compared to i.v. injection and PTX (entrapped plus released) was detected in the blood for at least 3days. Importantly, the systemic availability of s.c. administered drug-containing CCPM is substantially higher than that of other nanoformulations as reported in the literature (e.g. 3% in rodents). These results demonstrate that s.c. administration is a promising route to attain high systemic availability of CCPM, enabling a potentially more patient-friendly and cost-effective treatment approach than the i.v. route.

Redox-responsive core cross-linked micelles of poly(ethylene oxide)-b-poly(glycidyl methacrylate) by click chemistry

ABSTRACTRedox-responsive core cross-linked polymeric micelles were prepared by using azide-alkyne click chemistry. Poly(ethylene oxide)-b-poly(glycidyl methacrylate) (PEO-b-PGMA) copolymers were prepared by the atom transfer radical polymerization, and the PGMA parts were subsequently functionalized with azido groups. The micelles of azido-functional PEO5k-b-PGMA1.1k-N3 were cross-linked using dipropargyl 3,3′-dithiodipropionate as a disulfide-containing cross-linking agent. The block copolymers and polymeric micelles were characterized by using GPC, FT-IR, 1H NMR, TEM, and DLS analyses. The nanoparticle micelles showed much improved structural stability under physiological condition, while they were rapidly dissociated in the 1,4-dithio-D,L-threitol reducing environment.