Glycosylated polyacrylate nanoparticles by emulsion polymerization

A selection of glycosylated polyacrylate nanoparticles has been prepared by radical-initiated emulsion polymerization in aqueous media. Using ethyl acrylate as a co-monomer, carbohydrate acrylates were incorporated into the poly(ethyl acrylate) framework to give stable emulsions of glyconanoparticles with an average particle size of around 40 nm. Using this technique a variety of glyconanoparticles were prepared from 3-O-acryloyl-1,2:5,6-di-O-isopropylidene-alpha-D-glucofuranose, 1-O-acryloyl-2,3:5,6-di-O-isopropylidene-alpha-D-mannofuranose, 6-O-acryloyl-1,2:3,4-di-O-isopropylidene-alpha-D-galactopyranose, 2-N-acryloyl-1,3,4,6-tetra-O-acetyl-beta-D-glucosamine, 5-O-acryloyl-2,3-isopropylidene-1-methoxy-beta-D-ribofuranose and 4-N-acetyl-5'-O-acryloyl-2',3'-O-isopropylidene cytidine. Scanning electron microscopy, dynamic light scattering and proton NMR analysis of the emulsions indicated essentially 100% incorporation of the carbohydrate acrylate monomer into the polymer with the exception of O-benzyl- and O-benzoyl-protected carbohydrate acrylates, which gave incomplete incorporation. Formation of larger glyconanoparticles of ~80nm with (unprotected) 3-O-acryloyl-D-glucose and 5-O-acryloyl-1-methoxy-beta-D-ribofuranose revealed the influence of free hydroxyl groups in the monomer on the particle size during polymerization, a feature which is also apparently dependent on the amount of carbohydrate in the matrix. This methodology allows for a new, simple route to the synthesis of polymeric glyconanoparticles with potential applications in targeted drug delivery and materials development.     

Attenuating the size and molecular carrier capabilities of polyacrylate nanoparticles by a hydrophobic fluorine effect

This study investigates the effect of introducing alkyl chain fluorination on the properties of polyacrylate nanoparticles prepared in aqueous solution by emulsion polymerization. For this, 2,2,3,3,4,4,4-heptafluorobutyl acrylate (1) and methyl trifluoroacrylate (2) were tested as monomers as a means to prepare fluorinated polyacrylate nanoparticles to evaluate how side chain fluorination may affect nanoparticle size and drug carrier properties. Our results show that as fluorine content within the polyacrylate matrix increases, the size of the nanoparticle systematically diminishes, from 45nm (for nanoparticles containing no fluoroacrylate) to ～7nm (for nanoparticles constructed solely of fluoroacrylate). We also observe that as fluoroacrylate content and hydrophobicity increases, the nanoparticles decrease their ability to incorporate lipophilic molecules during the process of emulsification. These findings have meaningful implications in the implementation of fluorinated nanoparticles in molecular delivery.     

A convenient method to prepare emulsified polyacrylate nanoparticles from powders [corrected] for drug delivery applications

We describe a method to obtain purified, polyacrylate nanoparticles in a homogeneous powdered form that can be readily reconstituted in aqueous media for in vivo applications. Polyacrylate-based nanoparticles can be easily prepared by emulsion polymerization using a 7:3 mixture of butyl acrylate and styrene in water containing sodium dodecyl sulfate as a surfactant and potassium persulfate as a water-soluble radical initiator. The resulting emulsions contain nanoparticles measuring 40-50 nm in diameter with uniform morphology, and can be purified by centrifugation and dialysis to remove larger coagulants as well as residual surfactant and monomers associated with toxicity. These purified emulsions can be lyophilized in the presence of maltose (a non-toxic cryoprotectant) to provide a homogeneous dried powder, which can be reconstituted as an emulsion by addition of an aqueous diluent. Dynamic light scattering and microbiological experiments were carried out on the reconstituted nanoparticles. This procedure allows for ready preparation of nanoparticle emulsions for drug delivery applications.     

Antibiotic-conjugated polyacrylate nanoparticles: new opportunities for development of anti-MRSA agents

This report describes the preparation of polyacrylate nanoparticles in which an N-thiolated beta-lactam antibiotic is covalently conjugated onto the polymer framework. These nanoparticles are formed in water by emulsion polymerization of an acrylated antibiotic pre-dissolved in a liquid acrylate monomer (or mixture of co-monomers) in the presence of sodium dodecyl sulfate as a surfactant and potassium persulfate as a radical initiator. Dynamic light scattering analysis and electron microscopy images of these emulsions show that the nanoparticles are approximately 40 nm in diameter. The emulsions have potent in vitro antibacterial properties against methicillin-resistant Staphylococcus aureus and have improved bioactivity relative to the non-polymerized form of the antibiotic. A unique feature of this methodology is the ability to incorporate water-insoluble drugs directly into the nanoparticle framework without the need for post-synthetic modification. Additionally, the antibiotic properties of the nanoparticles can be modulated by changing the length or location of the acrylate linker on the drug monomer.     

DBU assisted expeditious synthesis of glycosyl dienes via glycosylated beta-hydroxy esters

DBU catalyzed condensation of 3-O-benzyl(methyl)-5,6-dideoxy-1,2-O-isopropylidene-beta-L-threo-hept-4-enofuranuronates with different aldehydes produces the corresponding 3-O-benzyl(methyl)-6-carbethoxy-5,6-dideoxy-1,2-O-isopropylidene-7-phenyl-beta-L-threo-hept-4-enofuranoses. The latter on treatment with methanesulfonyl chloride followed by DBU catalyzed E2 reaction of the methanesulfonyloxy intermediates gave the respective 3-O-benzyl(methyl)-6-carbethoxy-5,6,7-trideoxy-1,2-O-isopropylidene-7-phenyl-beta-L-threo-hept-4,6-dienofuranose in moderate to good yields.     

Penicillin-bound polyacrylate nanoparticles: restoring the activity of beta-lactam antibiotics against MRSA

This report describes the preparation of antibacterially active emulsified polyacrylate nanoparticles in which a penicillin antibiotic is covalently conjugated onto the polymeric framework. These nanoparticles were prepared in water by emulsion polymerization of an acrylated penicillin analogue pre-dissolved in a 7:3 (w:w) mixture of butyl acrylate and styrene in the presence of sodium dodecyl sulfate (surfactant) and potassium persulfate (radical initiator). Dynamic light scattering analysis and atomic force microscopy images show that the emulsions contain nanoparticles of approximately 40 nm in diameter. The nanoparticles have equipotent in vitro antibacterial properties against methicillin-susceptible and methicillin-resistant forms of Staphylococcus aureus and indefinite stability toward beta-lactamase.     

Preparation of 1,2-O-isopropylidene derivatives of alpha-D-galactoseptanose, beta-L-altroseptanose, and 3-O-methyl-alpha-D-guloseptanose

Displacement of the tosyloxy group in 5-O-benzyl-1,2-O-isopropylidene-4-O-(p-toluenesulfonyl)-alpha-D-glucoseptanose has yielded derivatives of 1,2-O-isopropylidene-alpha-D-galactoseptanose. Acid catalysed acetonation then gave 1,2:3,4-di-O-isopropylidene-alpha-D-galactoseptanose or 1,2;4,5-di-O-isopropylidene-alpha-D-galactoseptanose using lower acid concentrations. Reduction of the ketone derived from 1,2:3,4-O-isopropylidene-alpha-D-septanose gave 1,2;3,4-di-O-isopropylidene-beta-L-altroseptanose. Reaction of 3,4-anhydro-5-O-benzyl-1,2-O-isopropylidene-alpha-D-galactoseptanose with sodium methoxide gave 5-O-benzyl-1,2-O-isopropylidene-4-O-methyl-alpha-D-glucoseptanose and 5-O-benzyl-1,2-O-isopropylidene-3-O-methyl-alpha-D-guloseptanose. Solution-state conformations of these compounds have been deduced from their 1H NMR spectra.     

A new generation of polymer nanoparticles for drug delivery.

One of the main interests of using polymer nanoparticles as drug carrier systems is to control the delivery of the drugs including their biodistribution. During the last decade, it was clearly demonstrated that surface properties of nanoparticles were the key factor which determined the in vivo fate of such a carrier. Thus, the purpose of this work was to develop a new method which allows the easy fabrication of nanoparticles with versatile surface properties using polysaccharides. This preparation was based on the use of a redox radical polymerization reaction applied for the first time to the emulsion polymerization of alkylcyanoacrylates in aqueous continuous media. The dispersion of nanoparticles was very stable. The nanoparticle surfaces were coated with polysaccharides and their characteristics can be modulated by the type and the molecular weight of the polysaccharides used during the synthesis. Interestingly the biological properties of the polysaccharide immobilized on the nanoparticle surface can be preserved opening very interesting perspectives for such nanoparticles. This method also offers a new strategy for the design of modular biomimetic nanoparticles as drug carrier systems with multiple functions. One of the applications considered in this work was to use these nanoparticles coupled with haemoglobin as an oxygen carrier.     

Biocatalytic route to sugar-PEG-based polymers for drug delivery applications

Sugar-PEG-based polymers were synthesized by enzymatic copolymerization of 4-C-hydroxymethyl-1,2-O-isopropylidene-β-L-threo-pentofuranose/4-C-hydroxymethyl-1,2-O-benzylidene-β-L-threo-pentofuranose/4-C-hydroxymethyl-1,2-O-isopropylidene-3-O-pentyl-β-L-threo-pentofuranose with PEG-600 dimethyl ester using Novozyme-435 (Candida antarctica lipase immobilized on polyacrylate). Carbohydrate monomers were obtained by the multistep synthesis starting from diacetone-D-glucose and PEG-600 dimethyl ester, which was in turn obtained by the esterification of the commercially available PEG-600 diacid. Aggregation studies on the copolymers revealed that in aqueous solution those polymers bearing the hydrophobic pentyl/benzylidene moiety spontaneously self-assembled into supramolecular aggregates. The critical aggregation concentration (CAC) of polymers was determined by surface tension measurements, and the precise size of the aggregates was obtained by dynamic light scattering. The polymeric aggregates were further explored for their drug encapsulation properties in buffered aqueous solution of pH 7.4 (37 °C) using nile red as a hydrophobic model compound by means of UV/vis and fluorescence spectroscopy. There was no significant encapsulation in polymer synthesized from 4-C-hydroxymethyl-1,2-O-isopropylidene-β-L-threo-pentofuranose because this sugar monomer does not contain a big hydrophobic moiety as the pentyl or the benzylidene moiety. Nile red release study was performed at pH 5.0 and 7.4 using fluorescence spectroscopy. The release of nile red from the polymer bearing benzylidene moiety and pentyl moiety was observed with a half life of 3.4 and 2.0 h, respectively at pH 5.0, whereas no release was found at pH 7.4.     

Synthesis of 7-Deoxy-d-glycero-d-gluco-heptose (SF-666A)

The synthesis of 7-deoxy-d-glycero-d-gluco-heptose (1) from 3,5-O-benzylidene-1,2-O-isopropylidene-α-d-glucofuranose (2) is described. Oxidation of compound (2) afforded 3,5-O-benzylidene-1,2-O-isopropylidene-α-d-gluco-hexodialdo-1,4-furanose (3), which was then treated with methylmagnesium iodide to give 3,5-O-benzylidene-1,2-O-isopropylidene-7-deoxy-α-d-glycero-d-gluco-heptose (4) and its l-glycero-d-gluco isomer (5). Hydrolysis of (4) produced compound (1), which was identical with natural SF-666 A, a fermentation product of Streptomyces setonensis nov. sp.     

An efficient synthesis of 3-fluoro-5-thio-xylofuranosyl nucleosides of thymine, uracil, and 5-fluorouracil as potential antitumor or/and antiviral agents

1,2:5,6-Di-O-isopropylidene-alpha-D-glucofuranose by the sequence of mild oxidation, reduction, fluorination, periodate oxidation, borohydride reduction, and sulfonylation gave 3-deoxy-3-fluoro-1,2-O-isopropylidene-5-O-p-toluenesulfonyl-alpha-D-xylofuranose (5). Tosylate 5 was converted to thioacetate derivative 6, which after acetolysis gave 1,2-di-O-acetyl-5-S-acetyl-3-deoxy-3-fluoro-5-thio-D-xylofuranose (7). Condensation of 7 with silylated thymine, uracil, and 5-fluorouracil afforded nucleosides 1-(5-S-acetyl-3-deoxy-3-fluoro-5-thio-beta-D-xylofuranosyl) thymine (8), 1-(5-S-acetyl-3-deoxy-3-fluoro-5-thio-beta-D-xylofuranosyl) uracil (9), and 1-(5-S-acetyl-3-deoxy-3-fluoro-5-thio-beta-D-xylofuranosyl) 5-fluorouracil (10). Compounds 8, 9, and 10 are biologically active against rotavirus infection and the growth of tumor cells.     

Diffusion of beta-lactam antibiotics through oligomeric or monomeric porin channels of some gram-negative bacteria

The penetration of anionic beta-lactam antibiotics through porins was evaluated as a mechanism of drug resistance. The major proteins with porin activity were purified from the outer membranes of six bacteria. Three of the six porins were oligomeric porins. The molecular weights of their monomers were 37 kDa from Photobacterium damsela, 42 kDa from Serratia liquefaciens, and 36 kDa from E. coli B. The other three porins were heat-modifiable monomeric porins with molecular weights of 43 kDa from Porphyromonas asaccharolytica and Acinetobacter baumannii, and 37 kDa from Escherichia coli K12.Comparison of the six porin proteins revealed that, independent of their aggregation state, their amino acid content is similar but not identical. All have double the amount of negatively charged amino acids compared with positively charged amino acids. They have a similar polarity and polarity index. Two of the six tested bacteria do not produce beta-lactamase. These two bacteria were sensitive to the different beta-lactams tested. The other four bacteria were resistant to all or to several beta-lactams.A modified liposome swelling method was used for determining the rate of penetration of charged beta-lactam antibiotics. Zwitterionic beta-lactams were found to penetrate into liposomes at a rate that more or less fits their molecular weight, whether the porins are monomeric or oligomeric. The penetration rates of negatively charged beta-lactams are different for oligomeric and monomeric porins. Negatively charged beta-lactams penetrate through oligomeric porins better than estimated by their molecular weight, whereas monomeric porins are less penetrable to negatively charged beta-lactams than estimated by their molecular weight. The contribution of all types of porins to the susceptibility of bacteria to beta-lactam antibiotics (zwitterionic or negatively charged) is apparently doubtful. The porins may decrease or increase bacterial penetration rates to beta-lactams, and only the existence of a potential beta-lactamase that can destroy the penetrating drug will cause resistance.     

Synthesis of a cyanoethylidene derivative of 3,6-anhydro-d-galactose and its application as glycosyl donor

Starting from 1,2,4-tri-O-acetyl-3,6-anhydro-alpha-d-galactopyranose, 4-O-acetyl-3,6-anhydro-1,2-O-(1-cyanoethylidene)-alpha-d-galactopyranose (7) was synthesized by treatment with cyanotrimethylsilane. Additionally, 3,4-di-O-acetyl-1,2-O-(1-cyanoethylidene)-6-O-tosyl-alpha-d-galactopyranose was prepared from the corresponding bromide and both cyanoethylidene derivatives were used as donors in glycosylation reactions. The coupling with benzyl 2,4,6-tri-O-acetyl-3-O-trityl-beta-d-galactopyranoside provided exclusively the beta-linked disaccharides in approximately 30% yield. The more reactive methyl 2,3-O-isopropylidene-4-O-trityl-alpha-l-rhamnopyranoside gave with donors 3 and 7 the corresponding disaccharides in nearly 60% yield. Furthermore, the synthesis of 3,6-anhydro-4-O-trityl-1,2-O-[1-(endo-cyano)ethylidene]-alpha-d-galactopyranose, which can be used as a monomer for polycondensation reaction is described.     

Action of acid on 6-thio-hexose derivatives. Synthesis of 1,6-epithio-hexofuranoses

Reaction of 5,6-anhydro-1,2-O-isopropylidene-3-O-methanesulfonyl-3-L-idofuranose+ ++ with thioacetic acid in pyridine gave 6-S-acetyl-1,2-O-isopropylidene-3-O-methanesulfonyl-6-thio-3-L-idofur anose, which was deacetylated and the resultant thiol was converted into 1,2-O:5,6-O,S-diisopropylidene-3-O-methanesulfonyl-3-L-idofuran ose. Alkaline cleavage of the mesyl group gave 1,2-O: 5,6-O,S-diisopropylidene-3-L-idofuranose, which on treatment with hot dilute hydrochloric acid gave, after acetylation, 2,3,5-tri-O-acetyl-1,6-dideoxy-1,6-epithio-alpha-L-idofuranose+ ++ and not the expected idopyranose isomer. 1,2:3,5-Di-O-isopropylidene-6-O-toluene-p-sulfonyl-alpha-D-glucofuranose was converted into 6-S-acetyl-1,2:3,5-di-O-isopropylidene-6-thio-alpha-D-glucofuranose; conversion into the 6-thiol and isomerisation in acidified acetone gave 1,2-O:5,6-O,S-diisopropylidene-6-thio-alpha-D-glucofuranose. Acid treatment of this diacetal, or the isomeric 1,2:3,5-di-O-isopropylidene-6-thio-alpha-D-glucofuranose, followed by acetylation gave 2,3,5-tri-O-acetyl-1,6-dideoxy-1,6-epithio-beta-D-glucofuranose. Similar treatment of 1,2:3,4-di-O-isopropylidene-6-thio-alpha-D-galactopyranose gave 2,3,5-tri-O-acetyl-1,6-dideoxy-1,6-epithio-alpha-D-galactofuranose .     

Tumor-specific hybrid polyhydroxybutyrate nanoparticle: surface modification of nanoparticle by enzymatically synthesized functional block copolymer

A new approach to functionalize the surface of hydrophobic nanocarrier through enzymatic polymerization was demonstrated. The effective coupling between the hydrophobic surface of PHB nanoparticle and PHB chain grown from the enzyme fused with a specific ligand provided a simple way of functionalizing nanoparticles with active protein layers in aqueous environment. PHB nanoparticles loaded with model drug molecule, Nile red, were prepared through oil-in-water emulsion solvent evaporation method and the surface of nanoparticles were functionalized with tumor-specific ligand, RGD4C, fused with PHA synthase that drove the coupling reaction. The functionalized PHB nanoparticles showed a specific affinity to MDA-MB 231 breast cancer cells indicating that the tumor-specific ligand, RGD4C, was effectively displayed on the surface of PHB nanoparticles through enzymatic modification and confers targeting capability on the drug carrier.     

Hydrophobic silver nanoparticles trapped in lipid bilayers: Size distribution,bilayer phase behavior,and optical properties

Background  

Lipid-based dispersion of nanoparticles provides a biologically inspired route to designing therapeutic agents and a means of reducing nanoparticle toxicity. Little is currently known on how the presence of nanoparticles influences lipid vesicle stability and bilayer phase behavior. In this work, the formation of aqueous lipid/nanoparticle assemblies (LNAs) consisting of hydrophobic silver-decanethiol particles (5.7 ± 1.8 nm) embedded within 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers is demonstrated as a function of the DPPC/Ag nanoparticle (AgNP) ratio. The effect of nanoparticle loading on the size distribution, bilayer phase behavior, and bilayer fluidity is determined. Concomitantly, the effect of bilayer incorporation on the optical properties of the AgNPs is also examined.     

Engineering tumor-targeted gadolinium hexanedione nanoparticles for potential application in neutron capture therapy

Microemulsions (oil-in-water) have been employed as templates to engineer nanoparticles containing high concentrations of gadolinium for potential application in neutron capture therapy of tumors. Gadolinium hexanedione (GdH), synthesized by complexation of Gd(3+) with 2,4-hexanedione, was used as the nanoparticle matrix alone or in combination with either emulsifying wax or PEG-400 monostearate. Solid nanoparticles (<125 nm size) were obtained by simple cooling of the microemulsions prepared at 60 degrees C to room temperature in one vessel. The feasibility of tumor targeting via folate receptors was studied. A folate ligand was synthesized by chemically linking folic acid to distearoylphosphatidylethanolamine (DSPE) via a poly(ethylene glycol) (PEG; MW 3350) spacer. To obtain folate-coated nanoparticles, the folate ligand (0.75% w/w to 15% w/w) was added to either the microemulsion templates at 60 degrees C or nanoparticle suspensions at 25 degrees C. Efficiencies of folate ligand attachment/adsorption to nanoparticle formulations were monitored by gel permeation chromatography. Cell uptake studies were carried out in KB cells (human nasopharyngeal epidermal carcinoma cell line), known to overexpress folate receptors. The uptake of folate-coated nanoparticles was about 10-fold higher than uncoated nanoparticles after 30 min at 37 degrees C. The uptake of folate-coated nanoparticles at 4 degrees C was 20-fold lower than the uptake at 37 degrees C and comparable to the uptake of uncoated nanoparticles at 37 degrees C. Folate-mediated endocytosis was further verified by the inhibition of folate-coated nanoparticles uptake by free folic acid. It was observed that folate-coated nanoparticles uptake decreased to approximately 2% of its initial value with the coincubation of 0.001 mM of free folic acid. The results suggested that these tumor-targeted nanoparticles containing high concentrations of Gd may have potential for neutron capture therapy.     

临床分离的革兰阴性细菌的耐药谱及耐药机制的研究

目的 了解前临床上分离G^－细菌的药敏状况和耐药机制及提供合理使用抗生素的依据。方法 主要使用MICROSCAN WALKAWAY／－40全自动微生物分析仪对1999年3月－2000年3月全院住院病人的尿、痰、腹水、脓液、创面、前列腺液、血液等培养呈阳性的标本进行细菌鉴定和药敏试验,结果共检出G^-菌1152株包括27个菌属80个菌种,觉细菌是大肠埃希菌（16.1％）、铜绿假单胞菌（6.5％）、肺炎克雷伯菌（5.3％）等。G^-杆菌（除不动杆菌外）对第三代头孢霉素敏感率已降到（3.0%-76.1%)、对亚胺培南（80.7%-92%)、头孢哌酮／舒巴坦（58.8％－100％）、阿米卡星（41.4%-93.2%)、环丙沙星（30.5％－67.3％）较敏感;对第三代头孢霉素产生超广谱β－内酰胺酶（ESBLs）,肺炎克雷伯菌高达35.0%-36.9%,大肠5埃希菌达21.8％－23％。对常用β-内酰胺类抗生素产诱导酶（IB）,铜绿假单胸菌高达51％－60.9％,弗劳地枸橼酸菌达4.5％－63.6％,阴沟肠杆菌达8.7%-35.3％。结论 目前G^－杆菌对β-内酰胺类抗生素药的主要机制是产生ESBLs和IB0G^-杆菌引起的感染首选亚胺培南单用或第三代浆孢霉素复合制剂（头孢哌酮／舒巴坦）联合阿米卡星或氟喹酮类,第三代头孢霉素除非药敏提示否则不宜选用。     

Synthetic studies to improve the deuterium labelling in nucleosides for facilitating structural studies of large RNAs by high-field NMR spectroscopy

Synthetic studies to prepare ribonucleosides deuterated at C2' and the application of the developed procedures for the synthesis of 2H5-ribonucleosides from 1,2-O-isopropylidene-3-O-benzyl-ribofuranose-3,4,5,5'-2H4 have been reported.     

Replacement of the essential penicillin-binding protein 5 by high-molecular mass PBPs may explain vancomycin-β-lactam synergy in low-level vancomycin-resistant Enterococcus faecium D366

The mechanism of synergy between vancomycin and penicillin, as well as other beta-lactam antibiotics, was examined in a penicillin-resistant E. faecium (D366) expressing an inducible low-level resistance to vancomycin. It was demonstrated that penicillin per se was not able to reduce the inducible expression of the 39.5-kDa protein (VANB) or the carboxypeptidase activity which are involved in the mechanism of vancomycin resistance of this strain. Assays of competition between 3H-benzylpenicillin and diverse beta-lactam antibiotics suggested as the most likely explanation of the synergy that, once vancomycin resistance has been induced, the high-molecular mass penicillin-binding proteins (PBPs), and possibly PBP1 in particular, which have a high affinity for beta-lactam antibiotics, take over the role of the low-affinity PBP5 which is, in the non-induced strain, responsible for beta-lactam resistance.