Shell Cross-linked Micelles Research Articles

Low Fouling Molecular Selective Channels through Self-assembly of Cross-linked Block Copolymer Micelles for Selective Separation of Dye and Salt.

We report the solvent-evaporation and ionic cross-linking mediated self-assembly of the shell cross-linked micelles of the amphiphilic triblock copolymer containing middle poly(methyl methacrylate) block (hydrophobic) and poly(2-dimethylamino)ethyl methacrylate end blocks (hydrophilic) on the membrane substrate to create molecular selective channels. The formation of selective channels on the substrate is attributed to the local increase of micelle concentration upon solvent evaporation, which leads to the core-core hydrophobic interaction. The post-ionic cross-linking of the shell part further reduces the intermicelle distance, thereby creating interstices for selective separation. The TUF-1:1 membrane prepared by the self-assembly of the cross-linked micelles (triblock copolymer:halide-terminated PEG-based = 1:1 w w-1) and by the post-ionic cross-linking shows molecular weight cutoff of 3000 g mol-1 and pure water permeance of 52 L m-2 h-1 bar-1. The membrane shows 99.5-99.9% rejection of Congo red and Direct red-80 in the presence or absence of salts and Na2SO4 to dye separation factor of about 900. The added functionality (PEG) in the micelle structure provides good fouling-resistant properties toward dye and bovine serum albumin. This work provides the membrane formation mechanism and the advantages of the membrane for fractionation and resource recovery applications.

Substrate Channeling in Compartmentalized Nanoreactors.

Thermo- and photoresponsive nanoreactors based on shell cross-linked micelles (SCMs) for the rhodium-catalyzed asymmetric transfer hydrogenation (ATH) of ketones have been developed from poly(2-oxazoline) triblock terpolymers. The nanoreactors incorporate thermoresponsive poly(2-isopropyl-2-oxazoline) as the hydrophilic corona and are covalently cross-linked with a photoswitchable spiropyran molecule. UV irradiation or changes in temperature trigger morphology switching of the polymer-based nanoreactors that alters the hydrophobicity in separate layers of the SCMs, resulting in dynamic substrate selectivity of the ATH in water. Control experiments and kinetic studies show that the thermoresponsive outer layer induces the gated behavior for more hydrophobic substrates, whereas the photoresponsive cross-linking layer induces the gated behavior for less hydrophobic substrates. The nanoreactors mimic the multichannels in Nature, transporting substrates and reagents into the catalytic core which can be controlled through external triggers such as temperature and light wavelengths. Additionally, the nanoreactors can be easily recovered and reused with continued high activity and selectivities.

Shell-crosslinked micelles with neighborhood effect and pH/GSH sensitivity for co-loading of protein and polyphenol drugs

Herein, tri-block copolymer polyethyleneimine-poly(2-(diisopropylamino)ethyl methacrylate)-poly(3-acrylamido phenylboronic acid (PEI42-PDPA50-PAPBA15) and di-block copolymer PEI42-PAPBA15 were synthesized and used to prepare micelles for constructing a double-drug delivery system. Firstly, polyphenol drugs were coupled to PAPBA block of copolymer by ester bonds, which were verified to be enhanced by the neighborhood effect of tertiary amines on PDPA. And, a mixed micelle composed of PEI42-PDPA50-PAPBA15 and PEI42-PAPBA15 (denoted as Mixed-micelle) was prepared for comparing the drug release behavior with those micelles composed of single copolymer. Afterwards, a shell-crosslinked Mixed-micelle (denoted as Mixed-micelleGEL) was obtained through crosslinking PEI layer using a disulfide bond-contained crosslinker. The gel shell effectively improved the stability of the micelles and realized co-loading of protein and polyphenol drugs into independent space. The Mixed-micelleGEL had a good "bilayer blocking" effect on drug leakage. Their single- and double- drug releases under pH/GSH stimulus were studied. Furtherly, cell experiments explored the functions of Mixed-micelleGEL, such as the biocompatibility, the tumor targeting and intracellular transport of biomacromolecular drugs. In short, the drug delivery system prepared here showed excellent independently partitioned encapsulation and intracellular transport of two drugs including small molecule and biological macromolecule drugs.

Superparamagnetic Nanocrystals Clustered Using Poly(ethylene glycol)-Crosslinked Amphiphilic Copolymers for the Diagnosis of Liver Cancer.

Superparamagnetic iron oxide (SPIO) nanocrystals have been extensively studied as theranostic nanoparticles to increase transverse (T2) relaxivity and enhance contrast in magnetic resonance imaging (MRI). To improve the blood circulation time and enhance the diagnostic sensitivity of MRI contrast agents, we developed an amphiphilic copolymer, PCPZL, to effectively encapsulate SPIO nanocrystals. PCPZL was synthesized by crosslinking a polyethylene glycol (PEG)-based homobifunctional linker with a hydrophobic star-like poly(ε-benzyloxycarbonyl-L-lysine) segment. Consequently, it could self-assemble into shell-crosslinked micelles with enhanced colloidal stability in bloodstream circulation. Notably, PCPZL could effectively load SPIO nanocrystals with a high loading capacity of 66.0 ± 0.9%, forming SPIO nanoclusters with a diameter of approximately 100 nm, a high cluster density, and an impressive T2 relaxivity value 5.5 times higher than that of Resovist®. In vivo MRI measurements highlighted the rapid accumulation and contrast effects of SPIO-loaded PCPZL micelles in the livers of both healthy mice and nude mice with an orthotopic hepatocellular carcinoma tumor model. Moreover, the magnetic micelles remarkably enhanced the relative MRI signal difference between the tumor and normal liver tissues. Overall, our findings demonstrate that PCPZL significantly improves the stability and magnetic properties of SPIO nanocrystals, making SPIO-loaded PCPZL micelles promising MRI contrast agents for diagnosing liver diseases and cancers.

Photoresponsive Azobenzene-Functionalized Shell Cross-Linked Micelles for Selective Asymmetric Transfer Hydrogenation.

We describe the substrate-selective asymmetric transfer hydrogenation of aromatic ketones using rhodium complexes immobilized on a photoresponsive nanoreactor. The nanoreactor switches its morphology upon light irradiation in a wavelength-selective manner. Kinetic studies show that the gated behavior in the cross-linking layer is key to discriminating among substrates and reagents during catalysis. Under ultraviolet light irradiation, the nanoreactor displays substrate selectivity, converting smaller ketone substrates faster to the corresponding secondary alcohols.

Near-Infrared Light-Responsive Shell-Crosslinked Micelles of Poly(d,l-lactide)-b-poly((furfuryl methacrylate)-co-(N-acryloylmorpholine)) Prepared by Diels-Alder Reaction for the Triggered Release of Doxorubicin.

In the present study, we developed near-infrared (NIR)-responsive shell-crosslinked (SCL) micelles using the Diels–Alder (DA) click reaction between an amphiphilic copolymer poly(d,l-lactide)20-b-poly((furfuryl methacrylate)10-co-(N-acryloylmorpholine)78) (PLA20-b-P(FMA10-co-NAM78)) and a diselenide-containing crosslinker, bis(maleimidoethyl) 3,3′-diselanediyldipropionoate (BMEDSeDP). The PLA20-b-P(FMA10-co-NAM78) copolymer was synthesized by RAFT polymerization of FMA and NAM using a PLA20-macro-chain transfer agent (PLA20-CTA). The DA reaction between BMEDSeDP and the furfuryl moieties in the copolymeric micelles in water resulted in the formation of SCL micelles. The SCL micelles were analyzed by 1H-NMR, FE-SEM, and DLS. An anticancer drug, doxorubicin (DOX), and an NIR sensitizer, indocyanine green (ICG), were effectively incorporated into the SCL micelles during the crosslinking reaction. The DOX/ICG-loaded SCL micelles showed pH- and NIR-responsive drug release, where burst release was observed under NIR laser irradiation. The in vitro cytotoxicity analysis demonstrated that the SCL was not cytotoxic against normal HFF-1 cells, while DOX/ICG-loaded SCL micelles exhibited significant antitumor activity toward HeLa cells. Thus, the SCL micelles of PLA20-b-P(FMA10-co-NAM78) can be used as a potential delivery vehicle for the controlled drug release in cancer therapy.

Cross‐Linked Polymeric Micelles as Catalytic Nanoreactors

AbstractCross‐linked micelles have emerged as promising catalyst supports over the past two decades due to their improved structural stability, chemical diversity in multiple domains, and catalyst recovery compared to their uncross‐linked analogues. We highlight the different physicochemical properties that arise by cross‐linking the shell or core‐domain and the subsequent impact on catalysis. Both, shell cross‐linked micelles (SCMs) and core cross‐linked micelles (CCMs) were initially designed to include one catalytic entity. Later on, SCMs were used to compartmentalize catalysts for non‐orthogonal tandem catalysis while CCMs were investigated as phase transfer agents in biphasic catalysis. Current challenges in this field and new design trends for advanced micellar nanoreactors are discussed.

Compartmentalized Nanoreactors for One-Pot Redox-Driven Transformations

This contribution introduces poly(2-oxazoline)-based shell cross-linked micelles (SCMs) as nanoreactors to realize one-pot redox-driven deracemizations of secondary alcohols in aqueous media. TEMPO and Rh-TsDPEN moieties are spatially positioned into the hydrophilic corona and the hydrophobic micelle core, respectively. TEMPO catalyzes the oxidation of racemic secondary alcohols into ketones, while Rh-TsDPEN catalyzes the asymmetric transfer hydrogenation (ATH) of these ketones to afford enantioenriched secondary alcohols. Both catalysts, the Rh-TsDPEN complex and TEMPO, are incompatible with each other and the SCMs are designed to provide indispensable catalyst site isolation. Kinetic studies show that the SCMs enhance the reactivity of the immobilized catalysts, in comparison to those for the unsupported analogues under the same reaction conditions. Our nanoreactors can perform deracemizations on a broad range of secondary alcohol substrates and are reusable in a continuous manner while maintaining high...

The synthesis and co-micellization of PCL-P(HEMA/HEMA-LA) and PCL-P(HEMA/HEMA-FA) as shell cross-linked drug carriers with target/redox properties

In order to obtain target/redox shell cross-linked micelles (TCM), copolymers poly(ε-caprolactone)-poly(2-hydroxyethyl methacrylate/methacrylate-alpha lipoic acid) and poly(ε-caprolactone)-poly(2-hydroxyethyl methacrylate/methacrylate-folate, PCL-P(HEMA/HEMA-LA) and PCL-P(HEMA/HEMA-FA) were designed and synthesized. The copolymers PCL-P(HEMA/HEMA-LA) could form reduction-sensitive cross-linked micelles (CM) by using a catalytic amount of DTT. The micelles maintained high stability against dilution but were destroyed in 10 mM dithiothreitol (DTT). The drug loaded content (DLC) of CM was 8.9%, which was almost twice as much as non-cross-linked micelle (NCM). In vitro drug release at pH 7.4 showed that the cumulative release rate of CM in 36 h was less than 30%, while it was about 50% for NCM. When PCL-P(HEMA/HEMA-LA) and PCL-P(HEMA/HEMA-FA) (FA 1%, 3% and 5%) formed target/redox micelles, IC50 of TCM with FA 3% was the lowest (1.4 µg/mL) to Hela cells with excessive expression folate receptors. The cell uptake of TCM by Hela cells is higher than target non-cross-linked micelles (TNCM), while there was not much difference between both micelles uptaken by A549 cells, which are lack of folate receptors. Therefore, the drug carriers of TCM have potential to be explored as shell cross-linked target/redox drug carriers to the cancer cells on the surface with excessive folate receptors.

Reduction-responsive shell cross-linked micelles derived from amphiphilic triblock copolymer as anticancer drug delivery carrier

Stimuli-responsive crosslinked micelles are attractive carriers for in vivo delivery of water-insoluble therapeutic drugs due to their excellent stability during the blood circulation and high therapeutic effect resulting from the intelligent break-up of the crosslinked structure triggered by intracellular conditions as well as the subsequent fast drug release. Herein, novel amphiphilic triblock copolymer poly(l-lactide)-b-poly(allyl glycidyl ether/propanedithiol)-b-poly(ethylene glycol) (PLLA-b-P(AGE-SH)-b-PEG) was designed and synthesized by combining two successive ring-opening polymerizations and subsequent “thio-ene” reaction. Due to their unique amphiphilic architecture, copolymer PLLA-b-P(AGE-SH)-b-PEG could self-assemble into core-shell micelles, and the stimuli-responsive crosslinked micelles (SCMs) were obtained by crosslinking the P(AGE-SH) segments in the micellar shell under redox condition. The SCMs exhibited good stability against extensive dilution and slow sustained drug release in a simulated normal physiologycal environment, but fast release in the presence of GSH. As revealed by the cytotoxicity assay, the micelles from the copolymer PLLA-b-P(AGE-SH)-b-PEG showed excellent biocompatibility against HEK293T cells. Due to these combined good properties, the stimuli-responsive crosslinked micelles from PLLA-b-P(AGE-SH)-b-PEG are proposed to be an ideal carrier for the in vivo delivery of water-insoluble therapeutics.

Shell Cross-Linked Micelles as Nanoreactors for Enantioselective Three-Step Tandem Catalysis.

Functionalized amphiphilic poly(2-oxazoline)-based triblock copolymers that assemble into shell cross-linked micelles (SCMs) are described. These micelles permit the site isolation of three incompatible catalysts through compartmentalization, thereby enabling three-step non-orthogonal tandem processes in one pot. In particular, the acid-catalyzed ketal hydrolysis to prochiral ketones proceeded in the hydrophilic corona, followed by the Rh-catalyzed asymmetric transfer hydrogenation to enantio-enriched alcohols in the cross-linked shell, and nucleophilic base-catalyzed acylation in the hydrophobic core. The catalysts are positioned in close proximity on a single micelle support to take advantage of the intramicellar substrate diffusion, yet they are sufficiently spaced apart from each other in physically distinct microenvironments. These compartmentalized micelles are substrate selective and, on a basic level, mimic compartmentalized catalytic architectures found in nature.

One-Pot Synthesis of pH/Redox Responsive Polymeric Prodrug and Fabrication of Shell Cross-Linked Prodrug Micelles for Antitumor Drug Transportation.

Shell cross-linked (SCL) polymeric prodrug micelles have the advantages of good blood circulation stability and high drug content. Herein, we report on a new kind of pH/redox responsive dynamic covalent SCL micelle, which was fabricated by self-assembly of a multifunctional polymeric prodrug. At first, a macroinitiator PBYP- ss- iBuBr was prepared via ring-opening polymerization (ROP), wherein PBYP represents poly[2-(but-3-yn-1-yloxy)-2-oxo-1,3,2-dioxaphospholane]. Subsequently, PBYP- hyd-DOX- ss-P(DMAEMA- co-FBEMA) prodrug was synthesized by a one-pot method with a combination of atom transfer radical polymerization (ATRP) and a Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction using a doxorubicin (DOX) derivative containing an azide group to react with the alkynyl group of the side chain in the PBYP block, while DMAEMA and FBEMA are the abbriviations of N, N-(2-dimethylamino)ethyl methacrylate and 2-(4-formylbenzoyloxy)ethyl methacrylate, respectively. The chemical structures of the polymer precursors and the prodrugs have been fully characterized. The SCL prodrug micelles were obtained by self-assembly of the prodrug and adding cross-linker dithiol bis(propanoic dihydrazide) (DTP). Compared with the shell un-cross-linked prodrug micelles, the SCL prodrug micelles can enhance the stability and prevent the drug from leaking in the body during blood circulation. The average size and morphology of the SCL prodrug micelles were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. The SCL micelles can be dissociated under a moderately acidic and/or reductive microenvironment, that is, endosomal/lysosomal pH medium or high GSH level in the tumorous cytosol. The results of DOX release also confirmed that the SCL prodrug micelles possessed pH/reduction responsive properties. Cytotoxicity and cellular uptake analyses further revealed that the SCL prodrug micelles could be rapidly internalized into tumor cells through endocytosis and efficiently release DOX into the HeLa and HepG2 cells, which could efficiently inhibit the cell proliferation. This study provides a fast and precise synthesis method for preparing multifunctional polymer prodrugs, which hold great potential for optimal antitumor therapy.

“pH-triggered” drug release using shell cross-linked micelles from aqueous RAFT-synthesized PAPMA-b-PNIPAM copolymers

A new polymer namely poly (N-(3-aminopropyl) methacrylamide)-b-poly(N-isopropylacrylamide) (PAPMA-b-PNIPAM) was made for pH-triggered drug delivery by means of aqueous reversible addition-fragmentation chain transfer (RAFT) polymerization. PAPMA-b-PNIPAM was hydrophilic at 25 °C, and micelles were formed at 39 °C. The PAPMA chain was crosslinked with terephthaldicarboxaldehyde at pH = 9.0 and shell cross-linking (SCL) micelles were prepared. The sizes of the SCL micelles were 45~65 nm which can be reversible dissociated under acidic conditions. The formation of temperature-responsive SCL micelles and their cleavage behaviours were characterized.

Synthesis of temperature, pH, light and dual-redox quintuple-stimuli-responsive shell-crosslinked polymeric nanoparticles for controlled release

Herein, we prepared a novel quintuple-stimuli-responsive shell-crosslinked (SCL) nanocontainer in respond to temperature, pH, light, and oxidation or reduction species. The well-defined amphiphilic diblock copolymer poly(2-methacryloyloxyethyl ferrocenecarboxylate)-(5-propargylether-2-nitrobenzyl bromoisobutyrate)-poly(dimethylaminoethyl methacrylate) (PMAEFc-ONB-PDMAEMA) was synthesized via atom transfer radical polymerization (ATRP) and click chemistry. The diblock copolymer self-assembled into spherical micelles with a uniform size in aqueous media as non-crosslinked (NCL) micelles, and then the micelles were crosslinked by N,N′-bis(bromoacetyl) cystamine (BBAC) through quaternization reaction between the nitrogen of DMAEMA and the bromine of BBAC to receive the SCL micelles which shrunk at higher temperature, swelled at acidic pH or a low concentration of hydrogen peroxide (H2O2), decrosslinked by a small amount of DL-dithiothreitol (DTT), and were disrupted with DTT and UV light. The multi-stimuli-sensitive properties of the SCL micelles were characterized in detail by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence spectra, and UV–Vis spectra. Owing to the protective effect of the crosslinked network, light response behaviors of the NCL and SCL micelles were different. In contrast to the single stimulus, the combined stimuli could trigger and regulate the release of hydrophobic drug model more effectively and precisely from the SCL micelles. The obtained multi-stimuli-responsive nanocontainers may lead to a new generation of controlled release in the fields of nanotechnology and biotechnology.

Fabrication of biocleavable shell cross-linked hybrid micelles for controlled drug release using a reducible silica monomer.

We report in this communication the first preparation of triblock copolymer-based biocleavable shell cross-linked (SCL) hybrid micelles using a reducible silica monomer that integrates a polymerizable methacrylate structure and in situ cross-linkers of silica precursors via a disulfide bond. The monomer developed herein offers a highly straightforward and robust strategy toward bioreducible silica-based hybrid nanoparticles for controlled drug release.

Doxorubicin Loading Capacity of Shell Cross-Linked Micelles with pH-Responsive Core as Anticancer Drug Delivery Nanocarriers

Detailed studies were performed to probe the effects of the cross-linking layer microstructure of pH-responsive shell cross-linked (SCL) micelles on the loading capacity of doxorubicin (DOX). Well-defined poly [(ethylene glycol)-block-2-(dimethylamino) ethyl methacrylate-block-2-(diethylamino) methacrylate] (PEG-b-P(DMA- co-QDMA)-b-PDEA) copolymer with “clickable” moieties in the middle block by the quaternization with propargyl bromide dissolved molecularly in acidic solution; micellization occurred at alkaline solution to form three-layer “onionlike” micelles constituting PDEA cores, P(DMA-co-QDMA) inner shells, and PEG coronas. Two types of cross-linker bearing azide group: 1,6-bisazidehexane and bis-(azidoethyl) disulfide were utilized to prepare the SCL micelles with different cross-linking layer microstructure via click chemistry at basic aqueous media. The results showed that two types of SCL micelles possessed excellent stability. In neutral solution, these SCL micelles still maintained structural integrity, and the average hydrodynamic diameter of SCL micelles 1 and SCL micelles 2 increased to 80 nm and 90 nm, respectively. In the acidic solution, due to the complete protonated of the PDEA core, the sizes of the two types of SCL micelles increased to 95 nm and 110 nm, respectively, which were favorable for the diffusion of the encapsulated drug in the core. Moreover, the cross-linking degree had no effect on the size of SCL micelles. The loading efficiency and loading content of the SCL micelles were significantly better than those of the uncross-linked micelles, and loading capacity did not vary with degree of cross-linking. However, the SCL micelles 1 demonstrated better loading capacity. This study could be a guidance for the future research on the effects of the cross-linking layer microstructure on controlled doxorubicin release.

Platinum covalent shell cross-linked micelles designed to deliver doxorubicin for synergistic combination cancer therapy.

The preparation of polymer therapeutics capable of controlled release of multiple chemotherapeutic drugs has remained a tough problem in synergistic combination cancer therapy. Herein, a novel dual-drug co-delivery system carrying doxorubicin (DOX) and platinum(IV) (Pt[IV]) was developed. An amphiphilic diblock copolymer, PCL-b-P(OEGMA-co-AzPMA), was synthesized and used as a nanoscale drug carrier in which DOX and Pt(IV) could be packaged together. The copolymers were shell cross-linked by Pt(IV) prodrug via a click reaction. Studies on the in vitro drug release and cellular uptake of the dual-drug co-delivery system showed that the micelles were effectively taken up by the cells and simultaneously released drugs in the cells. Futhermore, the co-delivery polymer nanoparticles caused much higher cell death in HeLa and A357 tumor cells than either the free drugs or single-drug-loaded micelles at the same dosage, exhibiting a synergistic combination of DOX and Pt(IV). The results obtained with the shell cross-linked micelles based on an anticancer drug used as a cross-linking linkage suggested a promising application of the micelles for multidrug delivery in combination cancer therapy.

Stimuli-responsive shell cross-linked micelles from amphiphilic four-arm star copolymers as potential nanocarriers for “pH/redox-triggered” anticancer drug release

A novel amphiphilic four-arm star copolymer [poly(ε-caprolactone)-b-poly(poly(ethylene glycol) methyl ether methacrylate-co-p-(2-methacryloxyethoxy) benzaldehyde)]4 [4-AS-PCL-P(PEGMA-co-MAEBA)] was designed and synthesized by a combination of ring-opening polymerization (ROP) and continuous activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Stimuli-responsive cross-linked micelles (SCMs) were prepared by crosslinking the shell structure of the self-assembled micelles from star copolymers. The SCMs could be de-cross-linked under low pH and redox conditions. After loading with the anticancer drug camptothecin (CPT), the SCMs displayed a good stability against extensive dilution and a slow sustained drug release at pH 7.4 with 15% in 24 h, while a fast release (54%) was observed at pH 5.0 and 10 mM DTT. Confocal microscopy studies and MTT assays revealed that the CPT-loaded SCMs showed a good uptake property and a high cytotoxicity against HepG2 tumor cells. The pH/redox dual stimuli-responsive cross-linked micelles are proposed to be a highly promising platform for the intracellular delivery of insoluble chemotherapeutics for cancer therapy.

A shell-crosslinked polymeric micelle system for pH/redox dual stimuli-triggered DOX on-demand release and enhanced antitumor activity

Based on targeted amphiphilic block copolymer N-acetyl glucosamine-poly (styrene-alt-maleic anhydride)58-b-polystyrene130 (NAG-P(St-alt-MA)58-b-PSt130), a pH/redox dual-triggered shell-crosslinked polymeric micelle system was constructed. The shell-crosslinked micelles (CLM) were prepared by post-crosslinking method to regulate drug release kinetics using cystamine as linkers between carboxy groups of the shell. Compared with non-crosslinked micelles (NCLM), CLM showed spherical shapes with little increased mean diameter of 102.40±0.54nm, low polydispersity index (PDI) of 0.19±0.36, enlarged zeta potential value from −41.46±0.99 to −9.31±0.50mV, indicating the successful modification of disulfide bonds in shell. In vitro drug release study clearly exhibited a pH and redox dual-sensitive drug release profile with significantly accelerated drug release under pH 5.0 and 10mM GSH conditions (46.84% in 96h) without burst release. Both CLM and NCLM showed quite different release profiles between physiological (pH 7.4) and tumoral microenvironment (pH 5.0), effectively avoiding the premature drug leakage and realizing on-demand drug release. The MTT assay implied that CLM presented a time- and concentration-dependent manner to inhibit proliferation of A549 and MCF-7 cells and much lower IC50 values in comparison with that of NCLM after 72h incubation. Both FCM and CLSM results showed that CLM displayed much higher cellular uptake efficiency and anti-tumor activities than NCLM and free DOX. CLM and NCLM could be internalized by energy-dependent endocytosis mechanism due to similar surface properties. Overall, this dual-stimuli triggered micelle system provided a promising tumor-responsive platform for cancer therapy.

Formulation of Acid-Sensitive Micelles for Delivery of Cabazitaxel into Prostate Cancer Cells.

We report the synthesis of an amphiphilic triblock copolymer composed of a hydrophilic poly(ethylene glycol) (PEG) block, a central poly(acrylic acid) (PAA) block, and a hydrophobic poly(methyl methacrylate) (PMMA) block using atom transfer radical polymerization technique. We examined the self-assembly of PEG-b-PAA-b-PMMA copolymers in aqueous solutions forming nanosized micelles and their ability to encapsulate hydrophobic guest molecules such as Nile Red (NR) dye and cabazitaxel (CTX, an anticancer drug). We used 2,2β'-(propane-2,2-diylbis(oxy))-diethanamine to react with the carboxylic acid groups of the central PAA block forming acid-labile, shell cross-linked micelles (SCLM). We investigated the loading efficiency and release of different guest molecules from non-cross-linked micelles (NSCLM) and shell cross-linked micelles (SCLM) prepared by reacting 50% (SCLM-50) and 100% (SCLM-100) of the carboxylic acid groups in the PAA in physiologic (pH 7.4) and acidic (pH 5.0) buffer solutions as a function of time. We examined the uptake of NR-loaded NSCLM, SCLM-50, and SCLM-100 micelles into PC-3 and C4-2B prostate cancer cells and the effect of different micelle compositions on membrane fluidity of both cell lines. We also investigated the effect of CTX-loaded NSCLM, SCLM-50, and SCLM-100 micelles on the viability of PC-3 and C4-2B cancer cells compared to free CTX as a function of drug concentration. Results show that PEG-b-PAA-b-PMMA polymers form micelles at concentrations ≥11 μg/mL with an average size of 40-50 nm. CTX was encapsulated in PEG-b-PAA-b-PMMA micelles with 55% loading efficiency in NSCLM. In vitro release studies showed that 30% and 85% of the loaded CTX was released from SCLM-50 micelles in physiologic (pH 7.4) and acidic (pH 5.0) buffer solutions over 30 h, confirming micelles' sensitivity to solution pH. Results show uptake of NSCLM and SCLM into prostate cancer cells delivering their chemotherapeutic cargo, which triggered efficient cancer cell death. PEG-b-PAA-b-PMMA micelles were not hemolytic and did not cause platelet aggregation, which indicate their biocompatibility.