Preparation of Polyamide Nanocapsules of Aloe vera L. Delivery with In Vivo Studies

Aloe vera is the oldest medicinal plant ever known and the most applied medicinal plant worldwide. The purpose of this study was to prepare polyamide nanocapsules containing A. vera L. by an emulsion diffusion technique with in vivo studies. Diethyletriamine (DETA) was used as the encapsulating polymer with acetone ethyl acetate and dimethyl sulfoxide (DMSO) as the organic solvents and Tween and gelatin in water as the stabilizers. Sebacoyl chloride (SC) monomer, A. vera L. extract, and olive oil were mixed with the acetone and then water containing DETA monomer was added to the solution using a magnetic stirrer. Finally, the acetone was removed under vacuum, and nanocapsules were obtained using a freeze drier. This study showed that the size of the nanocapsule depends on a variety of factors such as the ratio of polymer to oil, the concentration of polymers, and the plant extract. The first sample is without surfactant and the size of nanocapsules in the sample is 115 nm. By adding surfactant, nanocapsules size was reduced to 96 nm. Nanocapsules containing A. vera were administered to rats and the effects were compared with a normal control group. The results showed that in the A. vera group, the effect is higher. The nanocapsules were identified by scanning electron microscopy (SEM), zeta potential sizer (ZPS), and Fourier-transform infrared spectroscopy (FT-IR).KEY WORDS: Aloe vera L., in vivo, medicinal plant, nanocapsule, polyamide nanocapsule     

Self-assembly of polylactic acid and cholesterol-modified dextran into hollow nanocapsules

A study of the direct preparation of hollow polymer nanocapsules which composed of the biocompatible and biodegradable polymers, polysaccharide and polylactic acid (PLA), was presented. By the dialysis of a DMSO solution of cholesterol-modified dextran (Chol-Dex) and poly(d,l-lactic acid) against water, hollow polymer nanocapsules with a highly stable structure and relatively narrow size distribution were obtained. The formation mechanism and the effects of various factors such as PLA molecular weight and the weight ratio of Chol-Dex to PLA on the formation of hollow polymer nanocapsules were investigated by SEM, TEM and ¹H NMR analysis. The results showed that hollow capsules were obtained when the weight ratio of Chol-Dex to PLA was between 3:1 and 1:1, and when PLA of molecular weights greater than 360 Da were used. The hollow capsules with a sandwich shell structure derived from deposition of PLA and some amphiphilic polysaccharide on the internal interface of the polysaccharide-coated aggregates, which were formed through phase separation during the initial phase of the dialysis. This novel approach to hollow polymer nanocapsule formation represents a rare example of the self-assembly of two biocompatible polymers into nanometer-scale objects with interesting structures, shapes and morphology through a simple assembly process.     

TAT Peptide-Conjugated Magnetic PLA-PEG Nanocapsules for the Targeted Delivery of Paclitaxel: <Emphasis Type="Italic">In Vitro</Emphasis> and Cell Studies

Paclitaxel (PTX) and organophilic iron oxide nanocrystals of 7 nm average size were co-encapsulated in the oily core of poly(lactide)-poly(ethyleneglycol) (PLA-PEG) nanocapsules in order to develop magnetically responsive nanocarriers of PTX. The nanocapsules were prepared by a solvent displacement technique and exhibited satisfactory drug and iron oxide loading efficiency, high colloidal stability, and sustained drug release properties. Drug release also proved responsive to an alternating magnetic field. Magnetophoresis experiments showed that the magnetic responsiveness of the nanocapsules depended on their SPION content. The PTX-loaded nanocapsules exhibited comparable to free PTX cytotoxicity against the A549 lung cancer cell line at 24 h of incubation but higher cytotoxicity than free drug at 48 h of incubation. The conjugation of a cysteine-modified TAT peptide (HCys-Tyr-Gly-Arg-Lys-Lys-Arg-Arg-Gln-Arg-Arg-Arg-NH₂) on the surface of the nanocapsules resulted to highly increased uptake of nanocapsules by cancer cells, as well as to profound improvement of their cytotoxicity against the cancer cells. The results obtained justify further investigation of the prospects of these multifunctional PLA-PEG nanocapsules as a targeted delivery system of paclitaxel.     

Mannosylated poly(ethylene oxide)-b-poly(epsilon-caprolactone) diblock copolymers: synthesis, characterization, and interaction with a bacterial lectin

A novel bioeliminable amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) (PEO-b-PCL) diblock copolymer end-capped by a mannose residue was synthesized by sequential controlled polymerization of ethylene oxide and epsilon-caprolactone, followed by the coupling of a reactive mannose derivative to the PEO chain end. The anionic polymerization of ethylene oxide was first initiated by potassium 2-dimethylaminoethanolate. The ring-opening polymerization of epsilon-caprolactone was then initiated by the omega-hydroxy end-group of PEO previously converted into an Al alkoxide. Finally, the saccharidic end-group was attached by quaternization of the tertiary amine alpha-end-group of the PEO-b-PCL with a brominated mannose derivative. The copolymer was fully characterized in terms of chemical composition and purity by high-resolution NMR spectroscopy and size exclusion chromatography. Furthermore, measurements with a pendant drop tensiometer showed that both the mannosylated copolymer and the non-mannosylated counterpart significantly decreased the dichloromethane/water interfacial tension. Moreover, these amphiphilic copolymers formed monodisperse spherical micelles in water with an average diameter of approximately 11 nm as measured by dynamic light scattering and cryo-transmission electron microscopy. The availability of mannose as a specific recognition site at the surface of the micelles was proved by isothermal titration microcalorimetry (ITC), using the BclA lectin (from Burkholderia cenocepacia), which interacts selectively with alpha-D-mannopyranoside derivatives. The thermodynamic parameters of the lectin/mannose interaction were extracted from the ITC data. These colloidal systems have great potential for drug targeting and vaccine delivery systems.     

Synthesis and characterization of poly(ethylene oxide)-block-poly(methylidene malonate 2.1.2) block copolymers bearing a mannose group at the PEO chain end

A poly(ethylene oxide)-block-poly(methylidene malonate 2.1.2) block copolymer (PEO-b-PMM 2.1.2) bearing a mannose moiety at the poly(ethylene oxide) chain end was synthesized by sequential anionic polymerization of ethylene oxide (EO) and methylidene malonate 2.1.2 (MM 2.1.2), followed by a coupling reaction between its poly(ethylene oxide) amino- or aldehyde-end group and a sugar derivative. Different coupling procedures, either in organic media or in aqueous micellar solutions, were examined in order to optimize the poly(ethylene oxide) end-glycosylation yield. The micellar size of the functionalized block copolymers was determined by dynamic light scattering.     

Mesoporous silica templated-albumin nanoparticles with high doxorubicin payload for drug delivery assessed with a 3-D tumor cell model

Human serum albumin (HSA) nanoparticles emerge as promising carriers for drug delivery. Among challenges, one important issue is the design of HSA nanoparticles with a low mean size of ca. 50?nm and having a high drug payload. The original strategy developed here is to use sacrificial mesoporous nanosilica templates having a diameter close to 30?nm to drive the protein nanocapsule formation. This new approach ensures first an efficient high drug loading (ca. 30%) of Doxorubicin (DOX) in the porous silica by functionalizing silica with an aminosiloxane layer and then allows the one-step adsorption and the physical cross-linking of HSA by modifying the silica surface with isobutyramide (IBAM) groups. After silica template removal, homogenous DOX-loaded HSA nanocapsules (30–60?nm size) with high drug loading capacity (ca. 88%) are thus formed. Such nanocapsules are shown efficient in multicellular tumor spheroid models (MCTS) of human hepatocarcinoma cells by their significant growth inhibition with respect to controls. Such a new synthesis approach paves the way toward new protein based nanocarriers for drug delivery.     

生物响应酸性磷酸酶浓度的载药聚电解质的体外控释分析

研制一种可响应酸性磷酸酶浓度变化的聚电解质胶囊,(PAH/PSS-β-甘油磷酸酯)胶囊,在分析胶囊的理化性质的基础上对其阿霉素药物包封和体外控释行为进行研究.通过层层组装的方法,制备囊壁含有酸性磷酸酶底物β-甘油磷酸酯的空壳胶囊和囊壁不含酸性磷酸酶底物的对照空壳胶囊;用电镜测定胶囊的大小和形态:用MTT方法分析胶囊的生物相容性.通过药物浓度梯度法进行胶囊的阿霉素药物包封并测定其包封率.将酸性磷酸酶标准品、分泌酸性磷酸酶的HepG2细胞株分别与载药阿霉素胶囊和载药阿霉素对照胶囊作用,观察阿霉素胶囊的药物控释情况和对肿瘤细胞生长的影响.空壳(PAH/PSS-β-甘油磷酸酯)胶囊粒径多在200-300 nm之间,胶囊浓度≤250μtg/mL时生物相容性良好,对阿霉素的包封率迭68.12%;载药胶囊组和对照组分别与酸性磷酸酶标准品作用,至48 h时分别释放出载药量的38%和15%,两者差异具有显著的统计学意义(P<0.05);载药胶囊组较载药对照组对HepG2细胞株的生长抑制作用明显增加,24 h HepG2细胞凋亡相差7.59%(13.73 Vs 6.14),有明显统计学意义(P<0.05).囊壁含有酸性磷酸酶底物的载药聚电解质胶囊,可在体外响应酸性磷酸酶浓度变化,具有药物控释性状,为临床上有酸性磷酸酶升高的良、恶性疾病的药物控释治疗提供了一种新的方法,其应用前景值得进一步探讨.     

Addition of Block Copolymers to Liposomes Prepared Using Soybean Lecithin. Effects on Formation,Stability and the Specific Localization of the Incorporated Surfactants Investigated

Abstract

Soybean lecithin disperses into water forming multilamellar liposomes, which on sonication produce vesicles of the order of 40–50nm (diameter), as determined by Photon Correlation Spectroscopy (PCS). The effect of concentration of lecithin and sonication time was systematically investigated. Vesicles were then prepared by incorporation of A – B – A block copolymers of polyethylene oxide (PEO) and polypropylene oxide(PPO), i.e.(PEO-PPO-PEO), in order to construct systems of increased steric stability. The effect of the molecular weight of the PEO and PPO chains on the vesicle size was systematically studied by using various molecules to prepare the vesicles. Initial addition of these (tri-)block copolymers causes an increase in the size of the vesicles. This increase continues until a certain concentration of block copolymer is reached, after which a decrease in size is observed. The initial increase was thought to be due to the incorporation of the block copolymer onto the vesicle bilayer. The reduction at high surfactant concentration is thought to be due to solubilization of the bilayer and the ultimate breakdown of the vesicles. Electrophoresis experiments showed a reduction in the ξ-potential of the vesicles on incorporation of the block copolymer which can be attributed to the shift of the shear plane. Various models are presented to describe this incorporation. The vesicles prepared using the block copolymers are believed to enhance the steric effects and so lead to more stable and pharmaceutically optimum systems.     

Preparation and stability of lipid-coated nanocapsules of cisplatin: anionic phospholipid specificity

Cisplatin nanocapsules represent a novel lipid formulation of the anti-cancer drug cis-diamminedichloroplatinum(II) (cisplatin), in which nanoprecipitates of cisplatin are coated by a phospholipid bilayer consisting of a 1:1 mixture of zwitterionic phosphatidylcholine (PC) and negatively charged phosphatidylserine (PS). Cisplatin nanocapsules are characterized by an unprecedented cisplatin-to-lipid ratio and exhibit increased in vitro cytotoxicity compared to the free drug [Nat. Med. 8, (2002) 81]. In the present study, the stability of the cisplatin nanocapsules was optimized by varying the lipid composition of the bilayer coat and monitoring in vitro cytotoxicity and the release of contents during incubations in water and in mouse serum. The release of cisplatin from the PC/PS (1:1) nanocapsules in water increased with increasing temperature with a t(1/2) of 6.5 h at 37 degrees C. At 4 degrees C, cisplatin was retained in the nanocapsules for well over 8 days. Replacement of PS by either phosphatidylglycerol or phosphatidic acid revealed that nanocapsules prepared of PS were more stable, which was found to be due to the ability of PS to form a stable cisplatin-PS coordination complex. Mouse serum had a strong destabilizing effect on the cisplatin nanocapsules. The PC/PS formulation lost over 80% of cisplatin within minutes after resuspension in serum. Incorporation of poly(ethylene glycol 2000) (PEG)-derivatized phosphatidylethanolamine and cholesterol in the bilayer coat extended the lifetime of the cisplatin nanocapsules in mouse serum to almost an hour. The results demonstrate that specificity in the interaction of cisplatin with anionic phospholipids is an important criterium for the formation and stability of cisplatin nanocapsules.     

α-Acetal, ω-Alkyne Poly(ethylene oxide) as a Versatile Building Block for the Synthesis of Glycoconjugated Graft-Copolymers Suited for Targeted Drug Delivery

α-Acetal, ω-alkyne poly(ethylene oxide) was synthesized as building block of glycoconjugated poly(ε-caprolactone)-graft-poly(ethylene oxide) (PCL-g-PEO) copolymers. The alkyne group is indeed instrumental for the PEGylation of a poly(α-azido-ε-caprolactone-co-ε-caprolactone) copolymer by the Huisgen's 1,3 dipolar cycloaddition, i.e., a click reaction. Moreover, deprotection of the acetal end-group of the hydrophilic PEO grafts followed by reductive amination of the accordingly formed aldehyde with an aminated sugar is a valuable strategy of glycoconjugation of the graft copolymer, whose micelles are then potential. A model molecule (fluoresceinamine) was first considered in order to optimize the experimental conditions for the reductive amination. These conditions were then extended to the decoration of the graft copolymer micelles with mannose, which is a targeting agent of dendritic cells and macrophages. The bioavailability of the sugar units at the surface of micelles was investigated by surface plasmon resonance (SPR). The same question was addressed to nanoparticles stabilized by the graft copolymer. Enzyme linked lectin assay (ELLA) confirmed the availability of mannose at the nanoparticle surface.     

Nanoencapsulation of Rose-Hip Oil Prevents Oil Oxidation and Allows Obtainment of Gel and Film Topical Formulations

The rose-hip oil holds skin regenerating properties with applications in the dermatological and cosmetic area. Its nanoencapsulation might favor the oil stability and its incorporation into hydrophilic formulations, besides increasing the contact with the skin and prolonging its effect. The aim of the present investigation was to develop suitable rose-hip-oil-loaded nanocapsules, to verify the nanocapsule effect on the UV-induced oxidation of the oil and to obtain topical formulations by the incorporation of the nanocapsules into chitosan gel and film. The rose-hip oil (500 or 600 μL), polymer (Eudragit RS100®, 100 or 200 mg), and acetone (50 or 100 mL) contents were separately varied aiming to obtain an adequate size distribution. The results led to a combination of the factors acetone and oil. The developed formulation showed average diameter of 158?±?6 nm with low polydispersity, pH of 5.8?±?0.9, zeta potential of +9.8?±?1.5 mV, rose-hip oil content of 54?±?1 μL/mL and tendency to reversible creaming. No differences were observed in the nanocapsules properties after storage. The nanoencapsulation of rose-hip oil decreased the UVA and UVC oxidation of the oil. The chitosan gel and film containing rose-hip-oil-loaded nanocapsules showed suitable properties for cutaneous use. In conclusion, it was possible to successfully obtain rose-hip-oil-loaded nanocapsules and to confirm the nanocapsules effect in protecting the oil from the UV rays. The chitosan gel and film were considered interesting alternatives for incorporating the nanoencapsulated rose-hip oil, combining the advantages of the nanoparticles to the advantages of chitosan.     

Biosafety of non-surface modified carbon nanocapsules as a potential alternative to carbon nanotubes for drug delivery purposes

Background

Carbon nanotubes (CNTs) have found wide success in circuitry, photovoltaics, and other applications. In contrast, several hurdles exist in using CNTs towards applications in drug delivery. Raw, non-modified CNTs are widely known for their toxicity. As such, many have attempted to reduce CNT toxicity for intravenous drug delivery purposes by post-process surface modification. Alternatively, a novel sphere-like carbon nanocapsule (CNC) developed by the arc-discharge method holds similar electric and thermal conductivities, as well as high strength. This study investigated the systemic toxicity and biocompatibility of different non-surface modified carbon nanomaterials in mice, including multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), carbon nanocapsules (CNCs), and C₆₀ fullerene (C₆₀). The retention of the nanomaterials and systemic effects after intravenous injections were studied.

Methodology and Principal Findings

MWCNTs, SWCNTs, CNCs, and C₆₀ were injected intravenously into FVB mice and then sacrificed for tissue section examination. Inflammatory cytokine levels were evaluated with ELISA. Mice receiving injection of MWCNTs or SWCNTs at 50 µg/g b.w. died while C₆₀ injected group survived at a 50% rate. Surprisingly, mortality rate of mice injected with CNCs was only at 10%. Tissue sections revealed that most carbon nanomaterials retained in the lung. Furthermore, serum and lung-tissue cytokine levels did not reveal any inflammatory response compared to those in mice receiving normal saline injection.

Conclusion

Carbon nanocapsules are more biocompatible than other carbon nanomaterials and are more suitable for intravenous drug delivery. These results indicate potential biomedical use of non-surface modified carbon allotrope. Additionally, functionalization of the carbon nanocapsules could further enhance dispersion and biocompatibility for intravenous injection.     

Oil-encapsulating PEO-PPO-PEO/PEG shell cross-linked nanocapsules for target-specific delivery of paclitaxel

PEO-PPO-PEO/PEG shell cross-linked nanocapsules encapsulating an oil phase in their nanoreservoir structure was developed as a target-specific carrier for a water-insoluble drug, paclitaxel. Oil-encapsulating PEO-PPO-PEO/PEG composite nanocapsules were synthesized by dissolving an oil (Lipiodol) and an amine-reactive PEO-PPO-PEO derivative in dichloromethane and subsequently dispersing in an aqueous solution containing amine-functionalized six-arm-branched poly(ethylene glycol) by ultrasonication. The resultant shell cross-linked nanocapsules had a unique core/shell architecture with an average size of 110.7 +/- 9.9 nm at 37 degrees C, as determined by dynamic light scattering and transmission electron microscopy. Paclitaxel could be effectively solubilized in the inner Lipiodol phase surrounded by a cross-linked PEO-PPO-PEO/PEG shell layer. The paclitaxel-loaded nanocapsules were further conjugated with folic acid to achieve folate receptor targeted delivery. Confocal microscopy and flow cytometric analysis revealed that folate-mediated targeting significantly enhanced the cellular uptake and apoptotic effect against folate receptor overexpressing cancer cells. The present study suggested that these novel nanomaterials encapsulating an oil reservoir could be potentially applied for cancer cell targeted delivery of various water-insoluble therapeutic and diagnostic agents.     

Synthesis and characterization of self-assembling block copolymers containing bioadhesive end groups

3,4-Dihydroxyphenyl-L-alanine (DOPA) is an unusual amino acid found in mussel adhesive proteins (MAPs) that is believed to lend adhesive characteristics to these proteins. In this paper, we describe a route for the conjugation of DOPA moieties to poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers. Hydroxyl end groups of PEO-PPO-PEO block copolymers were activated by N,N'-disuccinimidyl carbonate and then reacted with DOPA or its methyl ester with high coupling efficiencies from both aqueous and organic solvents. DOPA-modified PEO-PPO-PEO block copolymers were freely soluble in cold water, and dye partitioning and differential scanning calorimetry analysis of these solutions revealed that the copolymers aggregated into micelles at a characteristic temperature that was dependent on block copolymer composition and concentration in solution. Oscillatory rheometry demonstrated that above a block copolymer concentration of approximately 20 wt %, solutions of DOPA-modified PEO-PPO-PEO block copolymers exhibited sol-gel transitions upon heating. The gelation temperature could be tailored between approximately 23 and 46 degrees C by changing the composition, concentration, and molecular weight of the block copolymer. Rheological measurement of the bioadhesive interaction between DOPA-modified Pluronic and bovine submaxillary mucin indicated that DOPA-modified Pluronic was significantly more bioadhesive than unmodified Pluronic.     

Improved delivery of broadly neutralizing antibodies by nanocapsules suppresses SHIV infection in the CNS of infant rhesus macaques

Broadly neutralizing antibodies (bNAbs) directed to HIV-1 have shown promise at suppressing viremia in animal models. However, the use of bNAbs for the central nervous system (CNS) infection is confounded by poor penetration of the blood brain barrier (BBB). Typically, antibody concentrations in the CNS are extremely low; with levels in cerebrospinal fluid (CSF) only 0.1% of blood concentrations. Using a novel nanotechnology platform, which we term nanocapsules, we show effective transportation of the human bNAb PGT121 across the BBB in infant rhesus macaques upon systemic administration up to 1.6% of plasma concentration. We demonstrate that a single dose of PGT121 encased in nanocapsules when delivered at 48h post-infection delays early acute infection with SHIV_SF162P3 in infants, with one of four animals demonstrating viral clearance. Importantly, the nanocapsule delivery of PGT121 improves suppression of SHIV infection in the CNS relative to controls.     

An acid-labile block copolymer of PDMAEMA and PEG as potential carrier for intelligent gene delivery systems

Intelligent gene delivery systems based on physiologically triggered reversible shielding technology have evinced enormous interest due to their potential in vivo applications. In the present work, an acid-labile block copolymer consisting of poly(ethylene glycol) and poly(2-(dimethylamino)ethyl methacrylate) segments connected through a cyclic ortho ester linkage (PEG- a-PDMAEMA) was synthesized by atom transfer radical polymerization of DMAEMA using a PEG macroinitiator with an acid-cleavable end group. PEG- a-PDMAEMA condensed with plasmid DNA formed polyplex nanoparticles with an acid-triggered reversible PEG shield. The pH-dependent shielding/deshielding effect of PEG chains on the polyplex particles were evaluated by zeta potential and size measurements. At pH 7.4, polyplexes generated from PEG- a-PDMAEMA exhibited smaller particle size, lower surface charge, reduced interaction with erythrocytes, and less cytotoxicity compared to PDMAEMA-derived polyplexes. At pH 5.0, zeta potential of polyplexes formed from PEG- a-PDMAEMA increased, leveled up after 2 h of incubation and gradual aggregation occurred in the presence of bovine serum albumin (BSA). In contrast, the stably shielded polyplexes formed by DNA and an acid-stable block copolymer, PEG- b-PDMAEMA, did not change in size and zeta potential in 6 h. In vitro transfection efficiency of the acid-labile copolymer greatly increased after 6 h incubation at pH 5.0, approaching the same level of PDMAEMA, whereas there was only slight increase in efficiency for the stable copolymer, PEG- b-PDMAEMA.     

Thermogelling poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) disulfide multiblock copolymer as a thiol-sensitive degradable polymer

We report a reverse thermogelling poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) disulfide multiblock copolymer as a thiol-sensitive biodegradable polymer. The poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) aqueous solutions studied in this research underwent sol-gel-sol or sol-gel-sol-gel transition depending on the molecular weight and concentration of the polymer, whereas the corresponding disulfide multiblock copolymer aqueous solutions underwent sol-gel transition as the temperature increased in a range of 0-60 degrees C. The hydrophobic dye solubilization and dynamic light scattering of the polymer aqueous solution suggest that the poly(ethylene oxide-b-propylene oxide-b-ethylene oxide)s undergo unimer (3 nm) to micelle (12 nm) transition, whereas the disulfide multiblock copolymers undergo unimer (6 nm) to aggregated polymer (600 nm) transition as the temperature increases. The gel duration increased from 6 h (poly(ethylene oxide-b-propylene oxide-b-ethylene oxide)) to more than 12 days (the corresponding disulfide multiblock copolymer) in phosphate buffer saline, and the gel duration of the latter depended on the glutathione concentration of the medium. The model drug, paclitaxel, was released from the in-situ-formed poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) disulfide multiblock copolymer gel in a glutathione concentration-sensitive manner.     

Stable polymer bilayers for protein channel recordings at high guanidinium chloride concentrations

The use of chaotropic reagents is common in biophysical characterization of biomolecules. When the study involves transmembrane protein channels, the stability of the protein channel and supporting bilayer membrane must be considered. In this letter, we show that planar bilayers composed of poly(1,2-butadiene)-b-poly(ethylene oxide) diblock copolymer are stable and leak-free at high guanidinium chloride concentrations, in contrast to diphytanoyl phosphatidylcholine bilayers, which exhibit deleterious leakage under similar conditions. Furthermore, insertion and functional analysis of channels such as α-hemolysin and MspA are straightforward in these polymer membranes. Finally, we demonstrate that α-hemolysin channels maintain their structural integrity at 2 M guanidinium chloride concentrations using blunt DNA hairpins as molecular reporters.     

Suppressing unspecific cell uptake for targeted delivery using hydroxyethyl starch nanocapsules

Synthesizing nanocarriers with stealth properties and delivering a "payload" to the particular organ remains a big challenge but is the prime prerequisite for any in vivo application. As a nontoxic alternative to the modification by poly(ethylene glycol) PEG, we describe the synthesis of cross-linked hydroxyethyl starch (HES, M(w) 200,000 g/mol) nanocapsules with a size range of 170-300 nm, which do not show nonspecific uptake into cells. The specific uptake was shown by coupling a folic acid conjugate as a model targeting agent onto the surface of the nanocapsules, because folic acid has a high affinity to a variety of human carcinoma cell lines which overexpress the folate receptor on the cell surface. The covalent binding of the folic acid conjugate onto HES capsules was confirmed by FTIR and NMR spectroscopy. The coupling efficiency was determined using fluorescence spectroscopy. The specific cellular uptake of the HES nanocapsules after folic acid coupling into the folate-receptor presenting cells was studied by confocal laser scanning microscopy (CLSM) and flow cytometry.