Poly(vinyl alcohol) nanoparticles prepared by freezing-thawing process for protein/peptide drug delivery

Poly(vinyl alcohol) (PVA) hydrogel nanoparticles have been prepared by using a water-in-oil emulsion technology plus cyclic freezing-thawing process. The PVA hydrogel nanoparticles prepared by this method are suitable for protein/peptide drug delivery since formation of the hydrogel does not require crosslinking agents or other adjuvants and does not involve any residual monomer. Particularly, there is no emulsifier involved in this new method. Bovine serum albumin (BSA), as a model protein drug, is incorporated into the PVA hydrogel nanoparticles. The PVA hydrogel nanoparticles possess a skewed or log-normal size distribution. The average diameter of the PVA hydrogel nanoparticles is 675.5+/-42.7 nm. Protein drug loading efficiency in the PVA hydrogel nanoparticles is 96.2+/-3.8%. The PVA hydrogel nanoparticles swell in an aqueous solution and the swelling degree increases with the increase of temperature. In vitro release studies show that the BSA release from the nanoparticles can be prolonged to 30 h. The BSA release follows a diffusion-controlled mechanism. The number of freezing-thawing cycle and release temperature both influence BSA release rate considerably. Less freezing-thawing cycle or higher release temperature leads to faster drug release. The BSA is stable during preparation of the PVA hydrogel nanoparticles.     

Rare Earth Stearates as Thermal Stabilizers for Rigid Poly（vinyl chloride）

Poly(vinylchloride)(PVC)isoneofthefirstthermoplasticsdevelopedandhassomeenormoustechnicalandeconomicimportance.However,itspoorthermalstabilitystillremainsoneofitsmainproblems.ThermaldegradationofPVCoccursbyanautocatalyticdehydrochlorinatingreactionwiththe…     

Poly (lactic-glycolic) acid copolymer encapsulation of recombinant adenovirus reduces immunogenicity in vivo

Adenovirus-mediated gene transfer has application to the treatment of diseases of the central nervous system. We demonstrate that a limitation to its use in vivo is an inability to redose to the brain. We show that one factor inhibiting re-dosing is the development of neutralizing anti-adenoviral antibodies. Encapsulation of recombinant adenovirus vectors in poly(lactic/glycolic acid) (PLGA) copolymer enables infection in vitro, in the presence of neutralizing antibodies and results in the release of viable virus for over 100 h. Importantly, encapsulated adenovirus also shows diminished immunogenicity in vivo. Mice immunized with encapsulated recombinant adenoviral vectors show a greater than 45-fold reduction in anti-adenovirus titers relative to non-encapsulated vectors. An extended release formulation of adenovirus that reduces viral immunogenicity and sequesters the viral particle form antibody exposure may improve in vivo efficacy.     

Poly (DL-lactide-co-glycolide) microspheres as carriers for peptide vaccines

Peptides carrying an immunodominant T-helper cell epitope delineated from the rabies virus nucleoprotein either alone or in combination with a linear B-cell epitope from the same protein were incorporated into three different formulations of poly(DL-lactide-co-glycolide) (PLG) which were distinct in their composition, and consequently in their peptide release rates. In vitro peptides incorporated into any of the PLG formulations stimulated a peptide-specific T-cell line. Upon subcutaneous immunization of mice, the PLG formulation that showed the fastest peptide release rate induced the best immune response. This immune response was in magnitude comparable or even superior to that induced by peptide emulsified in complete Freund's adjuvant.     

Tumor accumulation of poly(vinyl alcohol) of different sizes after intravenous injection

The body distribution and tumor accumulation of polymers were evaluated using poly(vinyl alcohol) (PVA) which has the simplest chemical structure among water-soluble polymers, similar to poly(ethylene glycol). To study the effect of polymer size on the tumor accumulation, we used not only water-soluble PVA with different molecular weights but also PVA microgels prepared through gamma-irradiation of aqueous PVA solutions. The PVA specimens in the aqueous solution were intravenously injected to mice carrying a tumor mass at their footpad. Both types of PVA (water-soluble and microgel) of larger size were retained in the blood circulation for longer time periods and excreted more slowly from the kidney than those of smaller size. The plasma half-life period of PVA became longer with increasing size both for the water-soluble and microgel PVA, indicating that the body fate of PVA is governed only by the size. Both the water-soluble PVA and PVA microgels were accumulated in tumor tissue to a significantly greater extent than in normal tissue. The size dependence of the plasma half-life period and tumor accumulation was similar between the water-soluble PVA and the PVA microgels and the tumor accumulation became maximum around the size of 60 nm both for water-soluble and microgel PVA. A pharmacokinetical study demonstrated that the tumor uptake rate index of PVA decreased with the increase in PVA size. On the other hand, the greater the size, the larger the value of the area under the blood concentration-time curve (AUC). In addition, the PVA around 60 nm in diameter showed the smallest liver clearance. It was concluded that the balance between the uptake rate and the AUC as well as the liver clearance resulted in the maximum accumulation of PVA with the size of 60 nm.     

Evaluation of poly(vinyl alcohol)-gel spheres containing chitosan as dosage form to control gastrointestinal transit time of drugs

Two types of poly(vinyl alcohol)-gel spheres were prepared with chitosan (CS/PVA-GS) and without chitosan (PVA-GS), and comparative studies were performed using these gel spheres (GSs). No change in particle size was observed by the addition of chitosan: nearly 45% of both particles were in the 5-10 microm range. In an in vivo gastrointestinal transit test, CS/PVA-GS prolonged the small-intestinal transit time more than PVA-GS. In an in vitro intestinal perfusion study, the mean transit time of these GSs was markedly reduced by pretreatment of the intestinal surface with a mucolytic agent, N-acetyl-L-cysteine, suggesting that the mucous layer on the intestinal surface plays an important role in controlling the transit rate of these GSs. The oral administration of aminophylline (theophylline) and ampicillin as model drugs incorporated in PVA-GS and CS/PVA-GS was examined in rats. While theophylline absorption from PVA-GS was not affected by the addition of chitosan, the improvement of ampicillin absorption by PVA-GS was enhanced by the chitosan combination.     

Synthesis of a self-gelatinizable grafting copolymer of poly(vinyl alcohol) for construction of an amperometric peroxidase electrode

PURPOSE: To describe the clinical presentation and course of Whipple disease in an adult. METHODS: A 34-year-old man with phthisis bulbi in the right eye secondary to uveitis-induced neovascular glaucoma presented with severe acute posterior uveitis in the left eye. He underwent esophagogastroduodenoscopy and jejunal biopsy for evaluation of anemia. The posterior uveitis was treated with a subtenon injection of triamcinolone. RESULT: The diagnosis of Whipple disease was confirmed by polymerase chain reaction analysis of the jejunal biopsy that demonstrated Tropheryma whippelii rDNA. CONCLUSION: Although Whipple disease is typically evident with malabsorption, it can also present as uveitis without prominent gastrointestinal symptoms.     

Metal lanolin fatty acid as novel thermal stabilizers for rigid poly（vinyl chloride）

The synergistic stabilization effect of different metal lanolin fatty acids as natural-based thermal stabilizers for poly(vinyl chloride) (PVC) including calcium lanolin fatty acid (Calan2),zinc lanolin fatty acid (Znlan2) and lanthanum lanolin fatty acid (Lalan3) were studied through Congo red testing,color measurements,FTIR analyses and thermal behavior in this paper. The results showed that Lalan3/Calan2/Znlan2 stabilizers exhibited more excellent thermal stabilization efficiency to PVC than Calan2/Znlan2 thermal stabilizers,and the optimal mass ratio of Lalan3/Calan2/Znlan2 was 8:9:3. At last,the effect of degradation mechanism on PVC and synergistic stabilization was also investigated by FTIR analyses and thermal behavior.     

Safety assessment of polylactide (PLA) for use as a food-contact polymer

This report constitutes a safety assessment of polylactide (PLA), a polymer of lactic acid intended for use in fabricating various food-contact articles. Migration studies were conducted on samples of the polymer following guidelines issued by the Food and Drug Administration. Potential migrants from PLA include lactic acid, lactide (the monomer), and lactoyllactic acid (the linear dimer of lactic acid). The studies were designed to model reasonable 'worst' case extraction situations when the polymer is used (a) in houseware articles for short and intermediate time periods at various temperatures and (b) in food-packaging materials. The limited migration observed during the trials represents no significant risk since migrating species are expected to convert to lactic acid, a safe food substance. It is concluded that PLA is safe and 'Generally Recognized As Safe' for its intended uses as a polymer for fabricating articles that will hold and/or package food.     

聚L-乳酸(PLLA)的热稳定性

聚L-乳酸（PLIA）是具有良好生物相容性和生物降解性的半结晶聚合物，其热稳定性较差，在加工中的热处理会造成材料严重降解，使其相对分子质量显著下降，机械性能明显降低。该文作者通过试验、分析，研究了加热时间和加热温度对提纯与未提纯PLLA降解的影响，并结合降解机理对其原因进行探讨。结果表明，当温度升高到180℃以上时，在aomin内PLLA的相对分子质量即减小一半；提纯后的PLLA模压最佳加热温度为185℃。     

Poly (A)-rich ribonucleoprotein complexes from HeLa cell messenger RNA

Polyribosomal messenger RNA from HeLa cells contain 3'-OH-terminal polyadenylate sequences approximately 133 nucleotides in length (weight average). When analyzed at the ribonucleoprotein level of organization these poly(A)-rich sequences are found to contain tightly bound proteins. These proteins remain associated with the poly(A)-rich RNA during affinity chromatography of RNase A and T1-digested polyribosomes on poly(U)-Sepharose in 0.5 M NaCl, and co-elute from the column with the RNA at 50% formamide. Controls establish that the co-purification of the proteins with poly(A) on poly(U)-Sepharose requires the molecular integrity of the poly(A). Polyacrylamide gel electrophoresis resolves the poly(A)-specific proteins into two components of 74,000 and 62,000 molecular weight. The larger protein is the same size as that previously reported to be associated with poly(A)-rich sequences in HeLa heterogeneous nuclear RNA (Kish, V.M., and Pederson, T. (1975), J. Mol. Biol. 95, 227-238). It is concluded that both HeLa nuclear and polyribosomal poly(A) sequences have a protein (62,000 molecular weight) associated with poly(A) appears to be confined only to messenger RNA.     

Hydroxyapatite fiber reinforced poly(alpha-hydroxy ester) foams for bone regeneration

A process has been developed to manufacture biodegradable composite foams of poly(DL-lactic-co-glycolic acid) (PLGA) and hydroxyapatite short fibers for use in bone regeneration. The processing technique allows the manufacture of three-dimensional foam scaffolds and involves the formation of a composite material consisting of a porogen material (either gelatin microspheres or salt particles) and hydroxyapatite short fibers embedded in a PLGA matrix. After the porogen is leached out, an open-cell composite foam remains which has a pore size and morphology defined by the porogen. By changing the weight fraction of the leachable component it was possible to produce composite foams with controlled porosities ranging from 0.47 +/- 0.02 to 0.85 +/- 0.01 (n = 3). Up to a polymer:fiber ratio of 7:6, short hydroxyapatite fibers served to reinforce low-porosity PLGA foams manufactured using gelatin microspheres as a porogen. Foams with a compressive yield strength up to 2.82 +/- 0.63 MPa (n = 3) and a porosity of 0.47 +/- 0.02 (n = 3) were manufactured using a polymer:fiber weight ratio of 7:6. In contrast, high-porosity composite foams (up to 0.81 +/- 0.02, n = 3) suitable for cell seeding were not reinforced by the introduction of increasing quantities of hydroxyapatite short fibers. We were therefore able to manufacture high-porosity foams which may be seeded with cells but which have minimal compressive yield strength, or low porosity foams with enhanced osteoconductivity and compressive yield strength.     

Poly(ADP-ribose) synthetase activation mediates mitochondrial injury during oxidant-induced cell death

Reactive oxidant species are important mediators of tissue injury in shock, inflammation, and reperfusion injury. The actions of a number of these oxidants (e.g., hydroxyl radical and peroxynitrite, a reactive oxidant produced by the reaction of nitric oxide and superoxide) are mediated in part by the activation of the nuclear nick sensor enzyme, poly(ADP)-ribose synthetase (PARS), with consequent cellular energy depletion. Here we investigated whether PARS activation contributes to the mitochondrial alterations in cells exposed to oxidants. Authentic peroxynitrite (20 microM), the peroxynitrite-generating compound 3-morpholinosidnonimine, the combination of pyrogallol and S-nitroso-N-acetyl-D,L-penicillamine, as well as hydrogen peroxide induced a time- and dose-dependent decrease in mitochondrial transmembrane potential (delta psi(m)) in thymocytes, as determined by flow cytometry using the mitochondrial potential sensitive dyes DiOC6(3) and JC-1. A time- and dose-dependent increase in secondary reactive oxygen intermediate production and loss of cardiolipin, an indicator of mitochondrial membrane damage, were also observed, as measured by flow cytometry using the fluorescent dyes dihydroethidine and nonyl-acridine orange, respectively. Inhibition of PARS by 3-aminobenzamide or 5-iodo-6-amino-1,2-benzopyrone attenuated peroxynitrite-induced delta psi(m) reduction, secondary reactive oxygen intermediate generation, cardiolipin degradation, and intracellular calcium mobilization. Furthermore, thymocytes from PARS-deficient animals were protected against the peroxynitrite- and hydrogen peroxide-induced functional and ultrastructural mitochondrial alterations. In conclusion, mitochondrial perturbations during oxidant-mediated cytotoxicity are, to a significant degree, related to PARS activation rather than to direct effects of the oxidants on the mitochondria.     

Purification and characterization of an esterase involved in poly(vinyl alcohol) degradation by Pseudomonas vesicularis PD

An esterase catalyzing the hydrolysis of acetyl ester moieties in poly(vinyl alcohol) was purified 400-fold to electrophoretic homogeneity from the cytoplasmic fraction of Pseudomonas vesicularis PD, which was capable of assimilating poly(vinyl alcohol) as the sole carbon and energy source. The purified enzyme was a homodimeric protein with a molecular mass of 80 kDa and the isoelectric point was 6.8. The pH and temperature optima of the enzyme were 8.0 and 45 degrees C. The enzyme catalyzed the hydrolysis of side chains of poly(vinyl alcohol), short-chain p-nitrophenyl esters, 2-naphthyl acetate, and phenyl acetate, and was slightly active toward aliphatic esters. The enzyme was also active toward the enzymatic degradation products, acetoxy hydroxy fatty acids, of poly(vinyl alcohol). The K(m) and Vmax of poly(vinyl alcohol) (degree of polymerization, 500; saponification degree, 86.5-89.0 mol%) and p-nitrophenyl acetate were 0.381% (10.6 mM as acetyl content in the polymer) and 2.56 microM, and 6.52 and 12.6 mumol/min/mg, respectively. The enzyme was strongly inhibited by phenylmethylsulfonyl fluoride and diisopropyl fluorophosphate at a concentration of 5 mM, which indicated that the enzyme was a serine esterase. The pathway for the metabolism of poly(vinyl alcohol) is also discussed.     

用NaHCO3/Na2CO3粒子作致孔剂制备聚合物多孔支架

研究了一种新的制作多孔可生物降解聚合物支架的方法，该方法用碳酸氢钠／碳酸钠（NaHCO3／NazCO3）粒子作造孔剂，跟盐酸反应进行发泡。支架的孔隙率随着造孔剂与聚合物的质量比增加而增大，孔的尺寸随着造孔剂尺寸的增大而增大，通过控制造孔剂粒子的尺寸和用量，可以很容易地控制聚合物支架的孔结构。支架孔隙率高达94．8％，大孔的尺寸范围为100-400μm，并具有均匀的互相连通的开放的孔墙结构，有利于细胞和组织的生长。用该方法制作的支架比传统的盐沥滤法制作的支架，孔隙更多，分布均匀，大孔更多，孔墙结构互相连通、开放。     

Acetylsalicylic acid loaded poly(vinyl alcohol) hemodialysis membranes: effect of drug release on blood compatibility and permeability

Membranes developed from poly(vinyl alcohol) (PVA) have superior permeability because of the highly hydrophilic character of PVA. However, its blood compatibility needs to be further improved. For this we have developed acetylsalicylic acid (ASA, aspirin) loaded PVA membranes. It seems that the slow release of aspirin from the membrane provides a surface concentration of aspirin sufficient for partially inhibiting platelet adhesion. PVA membrane with 531 micrograms cm-2 of ASA loaded, may be selected for hemodialysis applications. This may help to reduce the amount of heparin infused during hemodialysis, thereby reducing the side-effects associated with the systemic administration of heparin.     

Self-assembly as a route to one-dimensional lanthanum(III) salicylaldimine coordination polymer

The self-assembled formation of a one-dimensional lanthanum salicylaldimine coordination polymer was proved by the X-ray diffraction analysis of new lanthanum(III) nitrate complex containing N,N'-bis(salicylidene)-1,5-pentanediamine ligand (H₂L). It was obtained in situ in a one-step, metal-templated condensation of salicylaldehyde with 1,5-pentanediamine (cadaverine, biogenic polyamine) and characterized by microanalysis and spectroscopic (IR, ESI-MS, UV-Vis, and ¹H NMR) data. The [La(NO₃)₃(μ-H₂L)₂]∞ complex displayed 10-coordinate distorted bicapped dodecahedron geometry with unusual coordination pattern of undeprotonated salicylaldimines which acted as μ-bridging ditopic ligands using exclusively the oxygens as donor atoms with the nitrogen atoms not being involved in the coordination environment.     

Poly(ethylene glycol) fluorescent linkers

The first examples of PEG linkers containing the highly fluorescent dansyl group have been synthesized. Quantum yields of these PEG fluorescent linkers (PFL) were determined and utilized in calculating the PEG number of various protein conjugates. The method was also shown to be applicable to lower molecular weight drugs as exemplified by taxol.     

Poly(ADP-ribose) polymerase and aging

The activation of oncogenes and the inactivation of tumour suppressor genes play a critical role in laryngeal tumorigenesis. Recent investigations revealed that 8p, 9p and 17q arms of human chromosomes harbour tumour suppressor genes (TSGs) such as p16 and BRCA1 with an important role in the multistage carcinogenesis of the larynx. In order to investigate the implication of these novel TSGs in the development of laryngeal neoplasia we performed a loss of heterozygosity (LOH) analysis using a bank of 15 polymorphic microsatellite markers (4 at 8p21, 7 at 9p21 arm and 4 at 17q arm surrounding the BRCA1 region) in a series of 32 cytological specimens (19 squamous cell carcinoma, 13 benign lesions of the larynx). Both benign and malignant specimens exhibited genetic alterations with at least one microsatellite marker. Fifteen (47%) out of the 32 specimens exhibited LOH at 8p21, 25/32 (78%) showed LOH at 9p21 and 18/32 (56%) displayed LOH at 17q21. Genetic alterations were detected in both benign and malignant lesions for all the loci tested suggesting an important role of these regions in the development of laryngeal neoplasia. This is the first report of detection of microsatellite alterations not only in solid tumours of the larynx but in laryngeal cytological specimens, suggesting that microsatellite analysis may be a useful tool in the primary diagnosis of the disease.