Xianglin Luo

Synthesis of an amphiphilic block copolymer containing zwitterionic sulfobetaine as a novel pH-sensitive drug carrier

pH-sensitive drug carriers offer promise for tumor targeted drug delivery. An amphiphilic triblock copolymer, poly(e-caprolactone)-block-poly(diethylaminoethyl methacrylate)-block-poly(sulfobetaine methacrylate) (PCL–PDEA–PSBMA), was synthesized through click reaction of alkyne end-functionalized poly(sulfobetaine methacrylate) (polySBMA–alkyne) onto azide end-functionalized PCL–PDEA (PCL–PDEA–N3) and was used as a pH-sensitive drug carrier in the form of micelles. In particular, the micelles exhibited pH dependency as a result of the protonation of the PDEA block. A hydrophobic drug, curcumin, was chosen as a model drug to investigate the potential application of this triblock copolymer in drug-controlled release. The results indicated that the release rate of curcumin-loaded micelles at pH 5.0 was faster than that at pH 7.4. Furthermore, the results of the pharmacokinetics of the curcumin-loaded micelles in vivo showed that the retention time of the curcumin-loaded micelles in blood could extend and the clearance of curcumin in the micelles was delayed, compared with the curcumin solution. This new pH-sensitive triblock copolymer PCL–PDEA–PSBMA has great potential as a hydrophobic anticancer drug carrier.

pH and redox-responsive mixed micelles for enhanced intracellular drug release

In order to prepare pH and redox sensitive micelles, amphiphilic copolymers of poly (epsilon-caprolactone)-b-poly(2-(diethylamino) ethyl methacrylate) (PCL-PDEA) and disulfide-linked poly(ethyl glycol)-poly(epsilon-caprolactone) (mPEG-SS-PCL) were synthesized. The double-sensitive micelles were prepared simply by solvent-evaporating method with the mixed two copolymers. The pH sensitivity of the mixed micelles was confirmed by the change of micelle diameter/diameter distribution measured by dynamic lighting scattering (DLS) and the redox sensitivity of the mixed micelles was testified by the change of micellar morphous observed by scanning electron microscope (SEM). In vitro drug release showed that drug-loaded mixed micelles (mass ratio 5:5) could achieve above 90% of drug release under low pH and reducing condition within 10h. Moreover, the drug-loaded mixed micelles (mass ratio 5:5) showed the largest cellular toxicity compared with other drug-loaded micelles, while blank mixed micelles exhibited no toxicity. These results meant that the mixed micelles composed by the two amphiphilic copolymers can enhance intracellular drug release. It is concluded that the newly developed mixed micelles can serve as a potential drug delivery system for anticancer drugs.

Cellular internalization of doxorubicin loaded star-shaped micelles with hydrophilic zwitterionic sulfobetaine segments

Four arm star-shaped poly(ε-caprolactone)-b-poly((N,N-diethylaminoethyl methacrylate)-r-(N-(3-sulfopropyl)-N-methacryloxyethy-N,N-diethylammoniumbetaine)) (4sPCLDEAS) micelles were loaded with anticancer drug doxorubicin to track their endocytosis in Hela cancer cell line. The effects of mean diameters and surface charges of the drug loaded micelles on the cellular uptake were studied in details. The results demonstrated that the internalization of micelles was both time and energy dependent process. Endocytic pathways including clathrin-mediated endocytosis, caveolae-mediated endocytosis and macropinocytosis were all involved in the internalization; caveolae-mediated endocytosis was the main pathway for the internalization of 4sPCLDEAS micelles. The assays for cell apoptosis and growth inhibition of tumor spheroids identified that these doxorubicin loaded micelles could induce cell apoptosis and inhibit tumor spheroids growth efficiently, which was even equal to free DOX·HCl. This study provided a rational design strategy for fabricating diverse micellar drug delivery systems with high anticancer efficiency.

Enhancement of cellular uptake and antitumor efficiencies of micelles with phosphorylcholine.

Internalization of drug delivery micelles into cancer cells is a crucial step for antitumor therapeutics. Novel amphiphilic star-shaped copolymers with zwitterionic phosphorylcholine (PC) block, 6-arm star poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) (6sPCL-b-PMPC), have been developed for encapsulation of poorly water-soluble drugs and enhancement of their cellular uptake. The star-shaped copolymers were synthesized by a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The copolymers self-assembled to form spherical micelles with low critical micelle concentration (CMC). The sizes of the micelles range from 80 to 170 nm and increase 30 ≈ 80% after paclitaxel (PTX) loading. Labeled with fluorescein isothiocyanate (FITC), the micelles were confirmed by fluorescence microscopy to have been internalized efficiently by tumor cells. Direct visualization of the micelles within tumor cells by transmission electron microscopy (TEM) confirmed that the 6sPCL-b-PMPC micelles were more efficiently uptaken by tumor cells compared to PCL-b-PEG micelles. When incorporated with PTX, the 6sPCL-b-PMPC micelles show much higher cytotoxicity against Hela cells than PCL-b-PEG micelles, in response to the higher efficiency of cellular uptake.

Effect of architecture on the micellar properties of poly (ɛ-caprolactone) containing sulfobetaines.

Linear and star-shape poly(ɛ-caprolactone)-b-poly(N-(3-sulfopropyl)-N-methacryloxyethyl-N,N-diethylammoniumbetaine) (L/sPCL-b-PDEAS) with 4 and 6 arms were synthesized with the combination of Ring Opening Polymerization (ROP) and Atom Transfer Radical Polymerization (ATRP). These copolymers self-assembled into micelles via solvent evaporation method. The critical micelle concentration (CMC), determined by fluorescence spectroscopy using pyrene as a probe, was lower than 10(-3)mg/mL and decreased with increasing arm numbers. Atom force microscopy (AFM) images showed that the micelles were spherical in shape with narrow size distribution. The hydrophobic drug model carotene was efficiently loaded in the polymeric micelles. The sizes and drug loading content (DLC) of the carotene-loaded micelles increased with increasing drug content in feed. In vitro drug release experiment demonstrated that the release rate of carotene from the micelles was closely related to the arm numbers and drug loading content. Linear copolymer micelles showed the fastest release rate, 4-arm star shape copolymer micelles exhibited the lowest release rate. The micelles with higher drug loading content showed lower release rate. The release kinetics of carotene from micelles fitted the Ritger-Peppas equation.

In situ Gelation of Supramolecular Hydrogel for Anti-Tumor Drug Delivery

A supramolecular injectable hydrogel was fabricated. The hydrogel was in situ gelated by the host-guest interaction between alpha-cyclodextrins (alpha-CDs) and methylated poly(ethylene glycol) grafted poly(alpha,beta-malic acid) (mPEG-g-PMA). The hydrogel was characterized by (1)NMR, XRD, DSC, TGA and SEM. The results showed that the polyrotaxanes of alpha-CDs/mPEG-g-PMA acted as physical crosslink sites in the hydrogel. Anti-tumor drug doxorubicin hydrochloride (DOX) was loaded in the hydrogel. The release and anti-tumor effect were studied in vitro. The burst release of DOX was restrained obviously. The sustaining release time lasted more than 3 d and the cell viability decreased greatly. This hydrogel is a promising injectable hydrogel for minimally invasive therapeutic drug delivery.

Synthesis of amphiphilic copolymers containing zwitterionic sulfobetaine as pH and redox responsive drug carriers.

Amphiphilic poly(ɛ-caprolactone)-SS-poly(N,N-diethylaminoethyl methacrylate)-r-poly(N-(3-sulfopropyl)-N-methacrylate-N,N-diethylammonium-betaine) (PCL-SS-PDEASB) was designed and synthesized successfully. pH and redox dually responsive micelles were prepared based on the obtained copolymers, with zwitterionic sulfobetaines as hydrophilic shell, DEA as pH sensitive content and disulfide as redox responsive linkage. The micelle diameters were all less than 200 nm and the micelle diameter distributions were narrow. These micelles could be triggered by pH and redox condition. The drug release from the drug-loaded micelles displayed fastest under simultaneously acidic and reductive conditions. Results of in vitro cell toxicity evaluation showed that introduction of sulfobetaines could greatly decrease the toxicity of poly(ɛ-caprolactone)-SS-poly(N,N-diethylaminoethyl methacrylate) (PCL-SS-PDEA) micelles. DOX-loaded PCL-SS-PDEASB micelles showed higher efficiency to kill HeLa cells than DOX-loaded PCL-PDEASB micelles. Half inhibitory concentration (IC50) of DOX-loaded PCL-SS-PDEASB micelles decreased with the content of sulfobetaines increasing and was even closer to that of DOX·HCl. Thus, the pH and redox dually responsive biodegradable micelles generated by PCL-SS-PDEASB may be potential smart drug carriers for tumor targeted delivery.

Synthesis and evaluation of star-shaped poly(ϵ-caprolactone)-poly(2-hydroxyethyl methacrylate) as potential anticancer drug delivery carriers

Novel star-shaped poly(ϵ-caprolactone)-b-poly(2-hydroxyethyl methacrylate) (sPCL-b-PHEMA) with 3 arm and 6 arm was synthesized by a combination of ring-opening polymerization and atom transfer radical polymerization. The structure of copolymers was confirmed by nuclear magnetic resonance (1H and 13C NMR) and Fourier transform infrared spectroscopy. The thermal behavior was measured by differential scanning calorimetry. The results showed that Tc, Tm, and Xc of the sPCL-b-PHEMA were reduced along with the increase in the length of the PHEMA block. The copolymers could self-assemble into dispersed micelles with quite low (×10−4 mg/mL) critical micelle concentration. The size and morphology of the micelles were characterized by dynamic light scattering and HAADF scanning transmission electron microscopy. It was found that the micelles were around 20–70 nm with a regular spherical shape. Moreover, drug loading content and encapsulation efficiency of paclitaxel by 3sPCL-b-PHEMA micelles were much lower than the values of 6sPCL-b-PHEMA micelles. The drug release experiments demonstrated that paclitaxelrelease was two-phase release profile and relative to the structure of sPCL-b-PHEMA.The in vitro cytotoxicity of sPCL-b-PHEMA micelles was evaluated using methylthiazoletetrazolium assay. The results showed no apparent inhibition effect on the Hela cells. These preliminary studies suggest that sPCL-b-PHEMA has a possible application as anticancer drug delivery carriers.

Characteristic of core materials in polymeric micelles effect on their micellar properties studied by experimental and dpd simulation methods

Polymeric micelles are one important class of nanoparticles for anticancer drug delivery, but the impact of hydrophobic segments on drug encapsulation and release is unclear, which deters the rationalization of drug encapsulation into polymeric micelles. This paper focused on studying the correlation between the characteristics of hydrophobic segments and encapsulation of structurally different drugs (DOX and β-carotene). Poly(ϵ-caprolactone) (PCL) or poly(l-lactide) (PLLA) were used as hydrophobic segments to synthesize micelle-forming amphiphilic block copolymers with the hydrophilic methoxy-poly(ethylene glycol) (mPEG). Both blank and drug loaded micelles were spherical in shape with sizes lower than 50 nm. PCL-based micelles exhibited higher drug loading capacity than their PLLA-based counterparts. Higher encapsulation efficiency of β-carotene was achieved compared with DOX. In addition, both doxorubicin and β-carotene were released much faster from PCL-based polymeric micelles. Dissipative particle dynamics (DPD) simulation revealed that the two drugs tended to aggregate in the core of the PCL-based micelles but disperse in the core of PLLA based micelles. In vitro cytotoxicity investigation of DOX loaded micelles demonstrated that a faster drug release warranted a more efficient cancer-killing effect. This research could serve as a guideline for the rational design of polymeric micelles for drug delivery.

Uptake enhancement of curcumin encapsulated into phosphatidylcholine-shielding micelles by cancer cells

Internalization of drugs by cancer cells is a crucial factor to impact cancer treatment effect. Curcumin, having inhibitory effect on a variety of cancers, was encapsulated into micelles of six-arm star-shape poly(ε-caprolactone)-b-poly(2-methacryloyloxyethylphosphorylcholine) (6sPCL-PMPC) in order to enhance its concentration in blood and cellular uptake. Micelles and curcumin-loaded micelles were prepared by the solvent-evaporation method. Drug-loading content and drug-loading efficiency could be achieved as high as 18.9 and 98%. MTT results showed that these curcumin-loaded micelles displayed significant cell cytotoxicity, while these blank micelles were noncytotoxic. The curcumin-loaded 6sPCL-PMPC micelles showed higher efficiency to kill HeLa cells than that of curcumin-loaded PCL-PEG micelles. The cellular uptake study indicated that the curcumin encapsulated into 6sPCL-PMPC micelles was ingested more by HeLa cells than the curcumin encapsulated into PCL-PEG micelles. In conclusion, the micelles with phosphatidylcholine (PC) groups as their exterior can greatly enhance the uptake by HeLa cells and the cytotoxicity of curcumin due to excellent internalization by cancer cells.