Cross-Linked Pectin Nanofibers with Enhanced Cell Adhesion.

Polysaccharides display poor cell adhesion due to the lack of cell binding domains. This severely limits their applications in regenerative medicine. This study reports novel cross-linked pectin nanofibers with dramatically enhanced cell adhesion. The nanofibers are prepared by at first oxidizing pectin with periodate to generate aldehyde groups and then cross-linking the nanofibers with adipic acid dihydrazide to covalently connect pectin macromolecular chains with adipic acid dihydrazone linkers. The linkers may act as cell binding domains. Compared with traditional Ca2+-cross-linked pectin nanofibers, the pectin nanofibers with high oxidation/cross-linking degree exhibit much enhanced cell adhesion capability. Moreover, the cross-linked pectin nanofibers exhibit excellent mechanical strength (with Young's modulus ∼10 MPa) and much enhanced body degradability (degrade completely in 3 weeks or longer time). The combination of excellent cell adhesion capability, mechanical strength, and body degradability suggests that the cross-linked pectin nanofibers are promising candidates for in vivo applications such as tissue engineering and wound healing. This cross-linking strategy may also be used to improve the cell adhesion capability of other polysaccharide materials.

Effect of cross-linking degree on selected properties of retrograded starch adipate.

The aim of this study was to determine the effects of the concentration of paste used to produce retrograded starch, and esterification degree, on selected properties of the resultant distarch adipate. Starch paste was prepared from native potato starch (1, 4, 10, 18 or 30 g/100g), frozen, defrosted and dried. Thus produced preparations of retrograded starch were cross-linked with various doses of a cross-linking agent (0.125, 0.25, 0.5, 1.0 or 2.0 ml per 100g of starch). Properties of the produced adipates depended on both the concentration of paste used to produce retrograded starch and the degree of substitution with adipic acid residues. Solubility in water and swelling power of the cross-linked preparations of retrograded starch, as well as pasting temperature and viscosity of produced pastes, all decreased along with the increasing degree of substitution with adipic acid residues.

The effect of pretreatment with substrates on the activity of immobilized pancreatic lipase.

Porcine pancreatic lipase was covalently immobilized on polyvinyl alcohol using adipoyl dichloride as a cross-linker. The effect of pre-treatment of lipase previously with various types of oils on immobilization efficiency was investigated. The increment in immobilization efficiency was observed after pre-treatment of lipases with oils. The highest immobilization efficiency obtained was 20% (v/v) for olive oil pre-treated lipase, which was 8 times higher than that of non-pretreated immobilized lipase. Immobilized lipase had better stability and had some advantages in comparison with free enzyme.

Selected properties of acetylated adipate of retrograded starch.

Native potato starch (NS) and retrograded starch (R - obtained via freezing and defrosting of a starch paste) were used to prepare starch acetates: NS-A and R-A, and then acetylated distarch adipates: NS-ADA and R-ADA. The chemically-modified preparations produced from retrograded starch (R-A; R-ADA) were characterized by a higher degree of esterification compared to the modified preparations produced under the same conditions from native potato starch (NS-A; NS-ADA). Starch resistance to amylolysis was observed to increase (to 30-40 g/100 g) as a result of starch retrogradation and acetylation. Starch cross-linking had a significant impact on the increased viscosity of the paste in the entire course of pasting characteristics and on the increased values of rheological coefficients determined from the equations describing flow curves. The produced preparation of acetylated retrograded starch cross-linked with adipic acid (R-ADA) may be deemed an RS3/4 preparation to be used as a food thickening agent.

Investigating the effects of surfactants on the size and hydrolytic stability of poly(adipic anhydride) particles.

The present study investigates the effects of surfactants (<0.01% v/v) on the size and hydrolytic stability of poly(adipic anhydride) (pAA) micro- and nanospheres fabricated using a modified phase inversion technique. Overall, surfactants increased the output yield by roughly 20%. Lecithin produced the greatest reduction in the volumetric particle size (dvol) compared to particles fabricated with no surfactant (dvol = 530 +/- 300 nm and 2.2 +/- 1.1 microm, respectively). In addition, sorbitan monooleate produced spheres with smaller numeric diameters (dnum) than the control but appeared to induce aggregation (dvol = 7.7 +/- 12.5 microm). The dnum and dvol were not dependent on the hydrophobicity of the surfactant (R2 = 0.36 and 0.03, respectively) or the apparent surface tension of the non-solvent (NS) phase (R2 = 0.44 and 0.04, respectively). In addition, quantitative DSC and FT-IR analysis confirmed that altering the particle size could also influence the hydrolytic stability of pAA.

Dehydroepiandrosterone 7-hydroxylase CYP7B: predominant expression in primate hippocampus and reduced expression in Alzheimer's disease.

Neurosteroids such as dehydroepiandrosterone (DHEA), pregnenolone and 17beta-estradiol are synthesized by cytochrome P450s from endogenous cholesterol. We previously reported a new cytochrome P450 enzyme, CYP7B, highly expressed in rat and mouse brain that metabolizes DHEA and related steroids by hydroxylation at the 7alpha position. Such 7-hydroxylation can enhance DHEA bioactivity in vivo. Here we show that the reaction is conserved across mammalian species: in addition to mouse and rat, DHEA hydroxylation activity was present in brain extracts from sheep, marmoset and human. Northern blotting using a human CYP7B complementary deoxyribonucleic acid (cDNA) probe confirmed the presence of CYP7B mRNA in marmoset and human hippocampus; CYP7B mRNA was present in marmoset cerebellum and brainstem, with lower levels in hypothalamus and cortex. In situ hybridization to human brain revealed higher levels of CYP7B mRNA in the hippocampus than in cerebellum, cortex, or other brain regions. We also measured CYP7B expression in Alzheimer's disease (AD). CYP7B mRNA was significantly decreased (approximately 50% decline; P<0.05) in dentate neurons from AD subjects compared with controls. A decline in CYP7B activity may contribute the loss of effects of DHEA with ageing and perhaps to the pathophysiology of AD.

Adipic acid increases plasma lysine but does not improve the efficiency of lysine utilization in swine.

Adipic acid, upon catabolism, results in intermediates that bear a structural similarity to lysine degradation products. The objectives of this research were to determine whether adipic acid affects lysine concentrations in plasma and to evaluate whether adipic acid improves the efficiency of lysine utilization in pigs. In Exp. 1, nursery pigs (n = 14) were fed (for a period of 7 d) either a standard nursery diet or the same diet supplemented with 1% adipic acid to assess effects on plasma amino acid concentrations (plasma collected on d 7). In Exp. 2, nursery pigs (n = 56) were fed (for a period of 15 d) either a control diet or the same diet but deficient in either lysine, threonine, or tryptophan with or without supplemental adipic acid to assess the effects of adipic acid on the efficiency of amino acid utilization. The results from Exp. 1 showed that adipic acid increased plasma lysine (by 18%) but not alpha-amino adipic acid, an intermediate in lysine degradation. Experiment 2 demonstrated that adipic acid did not increase the efficiency of utilization of lysine, threonine, or tryptophan. The lack of effects on alpha-amino adipic acid in Exp. 1 and the lack of a positive effect on the efficiency of utilization of lysine, threonine, and tryptophan suggest that adipic acid does not inhibit the mitochondrial uptake of lysine and(or) its degradation in the mitochondrion. It is concluded that feeding adipic acid increases plasma lysine but does not improve the efficiency of lysine utilization.

Specific migration testing with alternative fatty food simulants.

Many additives used in plastics materials and articles intended for food contact are expected to be assigned specific migration limits (SMLs) in a future amendment to EC Directive 90/128/EEC. In order to demonstrate compliance with these restrictions, specific migration tests will need to be performed on the finished plastics packaging using foods or the appropriate EC food simulants. Owing to the involatile and lipophilic nature of many of these additives, their analysis in the conventional fatty food simulant, olive oil, presents technical difficulties. One way of overcoming these difficulties would be to use a simple solvent alternative to olive oil as has been proposed for overall migration testing. The objective of this work is to compare specific migration data obtained using olive oil with alternative fat simulants iso-octane and 95% ethanol, to find out if similar results are obtained and identify the most appropriate alternative simulant to use for future testing. Good agreement with the olive oil migration data was obtained using 95% ethanol (equivalent exposure conditions) for both of the additives studied in polyolefins. For the polystyrene materials studied it is unlikely that the SMLs for the two additives would be exceeded, and in these cases iso-octane (1.5 h at 60 degrees C) could be used as a rapid 'alternative test'.

Migration from plasticized films into foods. 5. Identification of individual species in a polymeric plasticizer and their migration into foods.

To assess the significance of migration of polymeric plasticizers into foods, chemical characterization and quantification of individual oligomeric species is required. This paper reports the identification of seven individual oligomers isolated from a poly(butylene adipate) plasticizer. Based on mass spectrometry, NMR and chemical degradation, the oligomers were identified as a series of diol-terminated units ranging from a trimer up to an 11-monomer unit, along with a cyclic tetramer, all in the molecular weight range of 300-1100. A study of the migration of polymeric plasticizer from PVC film into olive oil indicated preferential migration of low molecular weight species. These oligomers which comprised 24% of the parent plasticizer contributed more than 90% of the plasticizer migration with the smallest oligomers migrating 90-fold more readily than the bulk of the plasticizer. From a knowledge of total polymeric plasticizer migration from PVC films under actual conditions of food-use, the abundance of individual oligomers in the foods has been estimated.