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1.
Saccharide-functionalized shell cross-linked (SCK) polymer micelles designed as polyvalent nanoscaffolds for selective interactions with receptors on Gram negative bacteria were constructed from mixed micelles composed of poly(acrylic acid-b-methyl acrylate) and mannosylated poly(acrylic acid-b-methyl acrylate). The mannose unit was conjugated to the hydrophilic chain terminus of the amphiphilic diblock copolymer precursor, from which the SCK nanoparticles were derived, by the growth of the diblock copolymer from a mannoside functionalized atom transfer radical polymerization (ATRP) initiator. Mixed micelle formation between the amphiphilic diblock copolymer and mannosylated amphiphilic diblock copolymer was followed by condensation-based cross-linking between the acrylic acid residues present in the periphery of the polymer micelles to afford SCK nanoparticles. SCKs presenting variable numbers of mannose functionalities were prepared from mixed micelles of controlled stoichiometric ratios of mannosylated and nonmannosylated diblock copolymers. The polymer micelles and SCKs were characterized by dynamic light scattering (DLS), electrophoretic light scattering, atomic force microscopy (AFM), transmission electron microscopy (TEM), and analytical ultracentrifugation (AU). Surface availability and bioactivity of the mannose units were evaluated by interactions of the nanostructures with the model lectin Concanavalin A via DLS studies, with red blood cells (rabbit) via agglutination inhibition assays and with bacterial cells (E. coli) via TEM imaging.  相似文献   

2.
Poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-b-PCL) block copolymers self-assemble into micelles in aqueous solution. We have examined whether these micelles can internalize into P19 cells in vitro. Fluorescently labeled PEO(45)-b-PCL(23) block copolymer was prepared by conjugating a tetramethylrhodamine molecule to the end of the hydrophobic PCL block. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) studies yielded 24 +/- 2 and 25 +/- 2 nm, respectively, for the diameters of the micelles. The studies also showed that chemical labeling did not effect the morphology or size. When the rhodamine-labeled PEO(45)-b-PCL(23) block copolymer micelles were tested in vitro, time-, concentration-, and pH-dependence of the internalization process suggested that internalization proceeded by endocytosis. The results from these studies provide the first direct evidence for the internalization of PEO(45)-b-PCL(23) micelles. Future studies will utilize multiple labeling of these micelles, allowing questions to be addressed related to the fate of internalized micelles as drug carriers, the destination of the incorporated drugs or fluorescent probes released from micelles, and the identification of the subcellular localization of the whole drug-carrier system within cells, both in vitro and in vivo.  相似文献   

3.
Well-defined amphiphilic diblock copolymers comprising thermoresponsive polymer segments of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PID) and hydrophobic polymer segments, poly(benzyl methacrylate) (PBzMA), were synthesized by controlled living radical polymerization. Terminal derivatization of PID segments to either hydroxyl or phenyl groups was achieved through reactions of coupling agents with thiol groups exposed by cleavage of terminal dithiobenzoate groups. Diblock copolymers formed core-shell type polymeric micelles with thermoresponsive outer shells. Hydrodynamic micellar diameters ranged from 12 to 31 nm, controlled by varying PID chain lengths. Differences in PID terminal groups did not affect the critical micelle concentration or micellar diameters. However, these groups demonstrated a significant influence on the micellar thermoresponses. Hydroxylated PID/PBzMA micelles exhibited a phase transition of approximately 40 degrees C, independent of PID molecular weights. Even though molecular weights and compositions of PID chains were equivalent except for terminal groups, micelles having the outermost surface phenyl groups exhibited drastically lower phase transition temperature shifts, especially for micelles with low molecular weight PID chains.  相似文献   

4.
Zeng F  Lee H  Chidiac M  Allen C 《Biomacromolecules》2005,6(4):2140-2149
Novel amphiphilic six-arm star diblock copolymers based on biocompatible and biodegradable poly(delta-valerolactone) (PVL) and methoxy poly(ethylene glycol) (MePEG) were synthesized by a two-step process. First, the hydrophobic star-shaped PVL with hydroxyl terminated functional groups was synthesized using a multifunctional alcohol, dipentaerythritol (DPE), as the initiator and fumaric acid as the catalyst. The amphiphilic six-arm star copolymer of poly(delta-valerolactone)-b-methoxy poly(ethylene glycol), (PVL-b-MePEG)(6), was then synthesized by coupling the hydroxyl terminated six-arm PVL homopolymer with alpha-methoxy-omega-chloroformate-poly(ethylene glycol) (MePEG-COCl). (1)H NMR and GPC analyses confirmed the successful synthesis of star-shaped copolymers with predicted compositions and narrow molecular weight distributions. DSC analysis revealed that the glass transition temperatures of the star PVL homopolymers with M(n) between 5000 and 49 000 are not dependent on their molecular weights, whereas the melting temperatures of both the PVL homopolymers and the amphiphilic (PVL-b-MePEG)(6) copolymers increase with an increase in the PVL molecular weight. Micelles were prepared from the (PVL-b-MePEG)(6) copolymers via the dialysis method and found to have effective mean diameters ranging from 10 to 45 nm, depending on the copolymer composition. In addition, the (PVL-b-MePEG)(6) copolymers having lower PVL content were found to form micelles with a narrow monomodal size distribution, whereas the copolymers having higher PVL content tended to form aggregates with a bimodal size distribution. The noncytotoxicity of the copolymers was also confirmed in CHO-K1 fibroblast cells using a cell viability assay, indicating that the (PVL-b-MePEG)(6) copolymers are suitable for biomedical applications such as drug delivery.  相似文献   

5.
In aqueous solution, it was found that the amphiphilic copolymer poly(ethylene glycol)-b-poly(caprolactone) (PEG(5000)-b-PCL(4100)) formed different morphologies, including long rod-like, short rod-like, or spherical aggregates, when the copolymer concentration was increased. Nearly identical morphologies were observed with the addition of increasing amounts of PEG(2000)-distearoylphosphoethanolamine (PEG(2000)-DSPE) to the copolymer. The morphologies of the aggregates in solution were confirmed by negative stain transmission electron microscopy (TEM) and cryogenic-TEM (cryo-TEM). The critical micelle concentrations of the PEG(5000)-b-PCL(4100) copolymer, PEG(2000)-DSPE and a mixture of the two materials (PEG(5000)-b-PCL 4100/PEG(2000)-DSPE) were evaluated to determine the thermodynamic stability of the aggregates. Differential scanning calorimetry was performed to gain insight into the degree of mixing of PEG(5000)-b-PCL(4100) and PEG(2000)-DSPE. Overall, combining PEG(5000)-b-PCL(4100) and PEG(2000)-DSPE produced a single population of mixed micelles with rod-like or spherical morphologies depending on the material composition and concentration.  相似文献   

6.
Rao J  Luo Z  Ge Z  Liu H  Liu S 《Biomacromolecules》2007,8(12):3871-3878
A polypeptide hybrid double hydrophilic diblock copolymer (DHBC), poly( N-isopropylacrylamide)- b-poly( l-glutamic acid) (PNIPAM- b-PLGA), was synthesized via the ring-opening polymerization of gamma-benzyl- l-glutamate N-carboxyanhydride (BLG-NCA) using monoamino-terminated PNIPAM as the macroinitiator, followed by deprotection of benzyl groups under alkaline conditions. Containing a thermoresponsive PNIPAM block and a pH-responsive PLGA block, the obtained polypeptide hybrid diblock copolymer molecularly dissolves in aqueous solution at alkaline pH and room temperature but supramolecularly self-assembles into PNIPAM-core micelles at alkaline pH and elevated temperatures and PLGA-core micelles at acidic pH and room temperature accompanied with coil-to-helix transition of the PLGA sequence. The pH- and thermoresponsive "schizophrenic" micellization behavior of PNIPAM- b-PLGA diblock copolymer has been investigated by (1)H NMR, optical transmittance, fluorescence probe measurement, transmission electron microscopy (TEM), dynamic and static laser light scattering (LLS), and circular dichroism (CD) spectroscopy. Moreover, the micellization process was investigated employing stopped-flow light scattering technique. The pH-induced micelle growth of PNIPAM- b-PLGA in aqueous solution exhibits drastically different kinetics compared to that of conventional pH-responsive DHBCs, probably due to the stabilization effects exerted by the formed alpha-helix secondary structures within the PLGA core at low pH. Exhibiting "schizophrenic" micellization, the polypeptide sequence of PNIPAM- b-PLGA can either locate within micelle cores or stabilizing coronas. The incorporation of polypeptide block into DHBCs can endow them with structural versatility, tunable spatial arrangement of chain segments within self-assembled nanostructures, and broader applications in the field of biomedicines.  相似文献   

7.
Novel sheddable micelles having hydrophilic coronas capable of being shed from biodegradable polylactide (PLA) cores by the cleavage of disulfide linkages in response to thiols were prepared by aqueous micellization of PLA-based amphiphilic block copolymers functionalized with disulfides at block junctions. These well-defined copolymers were synthesized by a combination of ring-opening polymerization and atom transfer radical polymerization in the presence of a new disulfide-functionalized double-head initiator having both terminal OH and Br groups. (1)H NMR and GPC results indicate that both polymerizations were well-controlled with molecular weight distribution as low as M(w)/M(n) < 1.2. Aqueous micellization to form core/shell micelles with disulfides at the interface of PLA cores and hydrophilic coronas and their thiol-responsive degradation were investigated. In the presence of water-soluble thiols, disulfide linkages in the micelles were cleaved and hydrophilic coronas were lost, causing PLA cores to precipitate due to the loss of colloidal stability. In a biomedical perspective, the new sheddable micelles were not cytotoxic and hence biocompatible.  相似文献   

8.
Hybrid peptidic-synthetic amphiphilic block copolymers, synthesized by living free radical polymerization (LFRP) on solid support, have been utilized as precursors for nanoscale materials possessing bio-available peptides. LFRP initiators, coupled to the peptide terminus upon the resin, facilitated the growth of homo- and block copolymers via nitroxide mediated radical polymerization (NMRP) or atom transfer radical polymerization (ATRP). Herein, the versatile solid-support synthesis of the antimicrobial peptide tritrpticin, coupling of living free radical polymerization initiators to the peptide-loaded resin, and the controlled radical polymerization of various monomers to yield amphiphilic diblock copolymers are described. Assembly of the peptidic-synthetic block copolymers into micelles and a preliminary assessment of their in vitro biological properties are detailed.  相似文献   

9.
Jiang X  Ge Z  Xu J  Liu H  Liu S 《Biomacromolecules》2007,8(10):3184-3192
A double hydrophilic ABC triblock copolymer, poly(2-(diethylamino)ethyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(N-isopropylacrylamide) (PDEA-b-PDMA-b-PNIPAM), containing the well-known pH-responsive PDEA block and thermoresponsive PNIPAM block, was synthesized by atom transfer radical polymerization via sequential monomer addition using ethyl 2-chloropropionate as the initiator. The obtained triblock copolymer exhibits interesting "schizophrenic" micellization behavior in aqueous solution, and supramolecularly self-assembles into three-layer "onion-like" PNIPAM-core micelles at acidic pH's and elevated temperatures and PDEA-core micelles with "inverted" structures at alkaline pH's and room temperature. In both cases, dynamic laser light scattering (LLS) and optical transmittance reveal the presence of near-monodisperse micelles, and the micelle formation/inversion process is fully reversible. Novel shell cross-linked (SCL) micelles with pH-responsive PDEA cores and thermoresponsive PNIPAM coronas were then facilely fabricated from the PDEA-b-PDMA-b-PNIPAM triblock copolymer by cross-linking the PDMA inner shells with 1,2-bis(2-iodoethoxy)ethane. The reversible pH-dependent swelling/shrinking of PDEA cores and thermosensitive collapse/aggregation of PNIPAM coronas of the obtained SCL micelles were investigated in detail by dynamic LLS, optical transmittance, and transmission electron microscopy. As the structurally stable SCL micelles possess pH-controllable core swellability and thermo-tunable corona permeability, the release profile of a model hydrophobic drug, dipyridamole, initially loaded within the hydrophobic PDEA core, can be dually controlled by both the solution pH and the temperature. This represents the first report of SCL micelles with multiresponsive cores and coronas, which may find practical applications in fields such as drug delivery and smart release.  相似文献   

10.
Lee H  Zeng F  Dunne M  Allen C 《Biomacromolecules》2005,6(6):3119-3128
Six amphiphilic diblock copolymers based on methoxy poly(ethylene glycol) (MePEG) and poly(delta-valerolactone) (PVL) with varying hydrophilic and hydrophobic block lengths were synthesized via a metal-free cationic polymerization method. MePEG-b-PVL copolymers were synthesized using MePEG with Mn = 2000 or Mn = 5000 as the macroinitiator. 1H NMR and GPC analyses confirmed the synthesis of diblock copolymers with relatively narrow molecular weight distributions (Mn/Mw = 1.05-1.14). DSC analysis revealed that the melting temperatures (Tm) of the copolymers (47-58 degrees C) approach the Tm of MePEG as the PVL content is decreased. MePEG-b-PVL copolymer aggregates loaded with the hydrophobic anti-cancer drug paclitaxel were found to have effective mean diameters ranging from 31 to 970 nm depending on the composition of the copolymers. A MePEG-b-PVL copolymer of a specific composition was found to form drug-loaded micelles of 31 nm in diameter with a narrow size distribution and improve the apparent aqueous solubility of paclitaxel by more than 9000-fold. The biological activity of paclitaxel formulated in the MePEG-b-PVL micelles was confirmed in human MCF-7 breast and A2780 ovarian cancer cells. Furthermore, the biocompatibility of the copolymers was established in CHO-K1 fibroblast cells using a cell viability assay. The in vitro hydrolytic and enzymatic degradation of the micelles was also evaluated over a period of one month. The present study indicates that the MePEG-b-PVL copolymers are suitable biomaterials for hydrophobic drug formulation and delivery.  相似文献   

11.
Du JZ  Chen DP  Wang YC  Xiao CS  Lu YJ  Wang J  Zhang GZ 《Biomacromolecules》2006,7(6):1898-1903
A novel biodegradable amphiphilic brush-coil block copolymer consisting of poly(epsilon-caprolactone) and PEGylated polyphosphoester was synthesized by ring opening polymerization. The composition and structure of the copolymer were characterized by 1H NMR, 13C NMR, and FT-IR, and the molecular weight and molecular weight distribution were analyzed by gel permeation chromatograph (GPC) measurements to confirm the diblock structure. These amphiphilic copolymers formed micellar structures in water, and the critical micelle concentrations (CMCs) were around 10(-3) mg/mL, which was determined using pyrene as a fluorescence probe. Transmission electron microscopy (TEM) images showed that the micelles took an approximately spherical shape with core-shell structure, which was further demonstrated by laser light scattering (LLS) technique. The degradation behavior of the polymeric micelle was also investigated in the presence of Pseudomonas lipase and characterized by GPC measurement. Such polymer micelles from brush-coil block copolymers are expected to have wide utility in the field of drug delivery.  相似文献   

12.
A series of novel amphiphilic triblock copolymers of poly(ethyl ethylene phosphate) and poly(-caprolactone) (PEEP-PCL-PEEP) with various PEEP and PCL block lengths were synthesized and characterized. These triblock copolymers formed micelles composed of a hydrophobic core of poly(-caprolactone) (PCL) and a hydrophilic shell of poly(ethyl ethylene phosphate) (PEEP) in aqueous solution. The micelle morphology was spherical, determined by transmission electron microscopy. It was found that the size and critical micelle concentration values of the micelles depended on both hydrophobic PCL block length and PEEP hydrophilic block length. The in vitro degradation characteristics of the triblock copolymers were investigated in micellar form, showing that these copolymers were completely biodegradable under enzymatic catalysis of Pseudomonas lipase and phosphodiesterase I. These triblock copolymers were used for paclitaxel (PTX) encapsulation to demonstrate the potential in drug delivery. PTX was successfully loaded into the micelles, and the in vitro release profile was found to be correlative to the polymer composition. These biodegradable triblock copolymer micelles are potential as novel carriers for hydrophobic drug delivery.  相似文献   

13.
Copolymers with different hydrophilic/lipophilic ratios (HLR) were used to optimize the compatibility between polymer as drug carrier and quercetin as lipophilic drug. Synthesis of amphiphilic triblock copolymers (TC) of poly(butylene adipate)–poly(ethylene glycol)–poly(butylene adipate) (PBA–PEG–PBA) with different PBA molecular weights is the first approach for this purpose. Polymerization and structural features of the polymers were analyzed by different characterization techniques (GPC, 1H NMR and FT-IR). Formation of hydrophobic and hydrophilic domains with different ratios in the ABA-triblock copolymers was studied by 1H NMR. The sunflower-like nanoparticles were prepared by self-assembling of the amphiphilic copolymers in the aqueous solution. The hydrophobic PBA segments formed the central solid-like core which stabilized by the hydrophilic PEG rings. The optimum HLR for these copolymers was determined on the basis of drug release time and profile, obtained from freeze-dried nanoparticle powders. The results indicated that optimum HLR for the sustained quercetin release obtained at higher molecular weight of polyesteric domains. Zeta potential measurements showed that the nanoparticle size was close related to the initial concentrations of the nanoparticle dispersions and the compositions of the triblock copolymers. Moreover, TEM pictures showed that the nanocarriers morphologies were changed by changing HLR of triblock copolymers. The PBA–PEG–PBA nanoparticles also showed good drug loading properties, suggesting that they were very suitable as delivery devices for hydrophobic drugs.  相似文献   

14.
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.  相似文献   

15.
"Stealth" nanoparticles made from polymer micelles have been widely explored as drug carriers for targeted drug delivery. High stability (i.e., low critical micelle concentration (CMC)) is required for their intravenous applications. Herein, we present a "core-surface cross-linking" concept to greatly enhance nanoparticle's stability: amphiphilic brush copolymers form core-surface cross-linked micelles (nanoparticles) (SCNs). The amphiphilic brush copolymers consisted of hydrophobic poly(epsilon-caprolactone) (PCL) and hydrophilic poly(ethylene glycol) (PEG) or poly(2-(N,N-dimethylamino)ethyl methacrylate) (PDMA) chains were synthesized by macromonomer copolymerization method and used to demonstrate this concept. The resulting SCNs were about 100 times more stable than micelles from corresponding amphiphilic block copolymers. The size and surface properties of the SCNs could be easily tailored by the copolymer's compositions.  相似文献   

16.
Liu J  Pang Y  Huang W  Huang X  Meng L  Zhu X  Zhou Y  Yan D 《Biomacromolecules》2011,12(5):1567-1577
A new type of biodegradable micelles for glutathione-mediated intracellular drug delivery was developed on the basis of an amphiphilic hyperbranched multiarm copolymer (H40-star-PLA-SS-PEP) with disulfide linkages between the hydrophobic polyester core and hydrophilic polyphosphate arms. The resulting copolymers were characterized by nuclear magnetic resonance (NMR), Fourier transformed infrared (FTIR), gel permeation chromatography (GPC), and differential scanning calorimeter (DSC) techniques. Benefiting from amphiphilic structure, H40-star-PLA-SS-PEP was able to self-assemble into micelles in aqueous solution with an average diameter of 70 nm. Moreover, the hydrophilic polyphosphate shell of these micelles could be detached under reduction-stimulus by in vitro evaluation, which resulted in a rapid drug release due to the destruction of micelle structure. The glutathione-mediated intracellular drug delivery was investigated against a Hela human cervical carcinoma cell line. Flow cytometry and confocal laser scanning microscopy (CLSM) measurements demonstrated that H40-star-PLA-SS-PEP micelles exhibited a faster drug release in glutathione monoester (GSH-OEt) pretreated Hela cells than that in the nonpretreated cells. Cytotoxicity assay of the doxorubicin-loaded (DOX-loaded) micelles indicated the higher cellular proliferation inhibition against 10 mM of GSH-OEt pretreated Hela cells than that of the nonpretreated ones. As expected, the DOX-loaded micelles showed lower inhibition against 0.1 mM of buthionine sulfoximine (BSO) pretreated Hela cells. These reduction-responsive and biodegradable micelles show a potential to improve the antitumor efficacy of hydrophobic chemotherapeutic drugs.  相似文献   

17.
Poly(ethylene glycol)-b-poly(γ-benzyl L-glutamate)s bearing the disulfide bond (PEG-SS-PBLGs), which is specifically cleavable in intracellular compartments, were prepared via a facile synthetic route as a potential carrier of camptothecin (CPT). Diblock copolymers with different lengths of PBLG were synthesized by ring-opening polymerization of benzyl glutamate N-carboxy anhydride in the presence of a PEG macroinitiator (PEG-SS-NH(2)). Owing to their amphiphilic nature, the copolymers formed spherical micelles in an aqueous condition, and their particle sizes (20-125 nm in diameter) were dependent on the block length of PBLG. Critical micelle concentrations of the copolymers were in the range 0.005-0.065 mg/mL, which decreased as the block length of PBLG increased. CPT, chosen as a model anticancer drug, was effectively encapsulated up to 12 wt % into the hydrophobic core of the micelles by the solvent casting method. It was demonstrated by the in vitro optical imaging technique that the fluorescence signal of doxorubicin, quenched in the PEG-SS-PBLG micelles, was highly recovered in the presence of glutathione (GSH), a tripeptide reducing disulfide bonds in the cytoplasm. The micelles released CPT completely within 20 h under 10 mM GSH, whereas only 40% of CPT was released from the micelles in the absence of GSH. From the in vitro cytotoxicity test, it was found that CPT-loaded PEG-SS-PBLG micelles showed higher toxicity to SCC7 cancer cells than CPT-loaded PEG-b-PBLG micelles without the disulfide bond. Microscopic observation demonstrated that the disulfide-containing micelle could effectively deliver the drug into nuclei of SCC7 cells. These results suggest that PEG-SS-PBLG diblock copolymer is a promising carrier for intracellular delivery of CPT.  相似文献   

18.
The preparation of biocompatible nanocarriers that have potential applications in the cosmetic and health industries is highly desired. The self-assembly of amphiphilic block copolymers displaying biosourced polysaccharides at the surface is one of the most promising approaches. In the continuity of our works related to the preparation of "hybrid" amphiphilic oligosaccharide-based block copolymers, we present here the design of a new generation of self-assembled nanoparticles composed entirely of oligosaccharide-based amphiphilic block co-oligomers (BCO). These systems are defined by a covalent linkage of the two saccharidic blocks through their reducing end units, resulting in a sweet "head-to-head" connection. As an example, we have prepared and studied a BCO in which the hydrophilic part is composed of a free maltoheptaosyl derivative clicked to a hydrophobic part composed of a peracetylated maltoheptaosyl derivative. This amphiphilic BCO self-assembles to form spherical micelles in water with an average diameter of 30 nm. The efficient enzymatic hydrolysis of the maltoheptaose that constitutes the shell of the micelles was followed by light scattering and colorimetric methods.  相似文献   

19.
Hu X  Liu S  Chen X  Mo G  Xie Z  Jing X 《Biomacromolecules》2008,9(2):553-560
A new biodegradable amphiphilic block copolymer, poly(ethylene glycol)-b-poly(L-lactide-co-9-phenyl-2,4,8,10-tetraoxaspiro[5,5]undecan-3-one) [PEG-b-P(LA-co-PTO)], was successfully prepared by ring-opening polymerization (ROP) of L-lactide (LA) and functionalized carbonate monomer 9-phenyl-2,4,8,10-tetraozaspiro[5,5]undecan-3-one (PTO) in the presence of monohydroxyl poly(ethylene glycol) as macroinitiator using Sn(Oct)2 as catalyst. NMR, FT-IR, and GPC studies confirmed the copolymer structure. It could self-assemble into micelles in aqueous solution with critical micelle concentration (CMC) in the magnitude of mg/L, which changed with the composition of the copolymer. After catalytic hydrogenation, copolymers with active hydroxyl groups were obtained. Adhesion and proliferation of Vero cells on the copolymer films showed that the synthesized copolymers were good biocompatible materials. In vitro degradation of the copolymer before and after deprotection was investigated in the presence of proteinase K. The free hydroxyl groups on the copolymers were capable of further modification with biotin. This new amphiphilic block copolymer has great potential for both drug encapsulation and conjugate because of its low CMC and the presence of active hydroxyl groups.  相似文献   

20.
Poly(aspartic acid)-block-polylactide diblock copolymers (PAsp-b-PLAs) having both hydrophilic and hydrophobic segments of various lengths were synthesized. These PAsp-b-PLA diblock copolymers formed polymeric micelles consisting of a hydrophobic PLA core and a hydrophilic, pH-sensitive PAsp shell in aqueous solution. The effects of the segment length of both the PLA and the PAsp portions and the pH of the solution on the shapes and sizes of the PAsp-b-PLA polymeric micelles were investigated. The results indicated a balance between the effects of electrostatic repulsion, hydrogen bonding in the PAsp shell layer, and hydrophobic interactions in the PLA core determine the sizes of the PAsp-b-PLA polymeric micelles. Moreover, the PAsp-b-PLA polymeric micelles did not possess any cytotoxic activity against L929 fibroblast cells. The obtained polymeric micelle should be useful for biodegradable biomedical materials such as drug delivery vehicle.  相似文献   

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