Highly sensitive chemiluminescence immunoassay on chitosan membrane modified paper platform using TiO2 nanoparticles/multiwalled carbon nanotubes as label

A highly sensitive chemiluminescence (CL) immunoassay was incorporated into a low‐cost microfluidic paper‐based analytical device (μ‐PAD) to fabricate a facile paper‐based CL immunodevice (denoted as μ‐PCLI). This μ‐PCLI was constructed by covalently immobilizing capture antibody on a chitosan membrane modified μ‐PADs, which was developed by simple wax printing methodology. TiO₂ nanoparticles coated multiwalled carbon nanotubes (TiO₂/MWCNTs) were synthesized as an amplification catalyst tag to label signal antibody (Ab₂). After sandwich‐type immunoreactions, the TiO₂/MWCNTs were captured on the surface of μ‐PADs to catalyze the luminol‐p‐iodophenol‐H₂O₂ CL system, which produced an enhanced CL emission. Using prostate‐specific antigen as a model analyte, the approach provided a good linear response range from 0.001 to 20 ng/mL with a low detection limit of 0.8 pg/mL under optimal conditions. This μ‐PCLI showed good reproducibility, selectivity and stability. The assay results of prostate‐specific antigen in clinical serum samples were in good agreement with that obtained by commercially used electrochemiluminescence methods at the Cancer Research Center of Shandong Tumor Hospital (Jinan, Shandong Province, China). This μ‐PCLI could be very useful to realize highly sensitive, qualitative point‐of‐care testing in developing or developed countries. Copyright © 2013 John Wiley & Sons, Ltd.     

锰过氧化物酶的耦合固定化及其性质研究

分别采用海藻酸钠、明胶和壳聚糖为载体,并以戊二醛为交联剂,通过包埋-交联和吸附-交联两种耦合固定化方法制备固定化锰过氧化物酶。探讨了酶的不同固定化条件和固定化酶的部分性能。与游离酶相比,制备的3种固定化酶最适反应pH分别由7.0降低到5.0、5.0和3.0,最适反应温度分别由35℃升高到75℃、55℃和75℃。3种固定化酶的耐热性都显著提高,其中用壳聚糖制成的固定化酶在pH 2.2～11的宽范围内表现出很好的酸碱耐受性。30℃连续测定6～9次酶活力,重复使用的3种固定化酶显示出良好的稳定性。将固定化酶应用在偶氮染料的脱色中,用明胶制成的固定化酶在静置和摇床条件下,以及用海藻酸钠制成的固定化酶在摇床条件下,均表现出与游离酶相近的脱色能力,并且在重复进行的摇床实验中,脱色能力未降低,反应前后的酶活力均没有损失。     

Effect of chitosan on hyphal growth and spore germination of plant pathogenic and biocontrol fungi

Aims: To investigate the toxic effect of chitosan on important root pathogenic and biocontrol fungi (nematophagous, entomopathogenic and mycoparasitic). Methods and Results: We have used standard bioassays to investigate the effect of chitosan on colony growth and developed bioassays to test spore germination. The results showed that the root pathogenic and mycoparasitic fungi tested were more sensitive to chitosan than nematophagous and entomopathogenic fungi. Chitosanases (and perhaps related enzymes) are involved in the resistance to chitosan. Two fungi, one sensitive to chitosan, Fusarium oxysporum f. sp. radicis‐lycopersici, and one less sensitive, Pochonia chlamydosporia, were selected for ultrastructural investigations. Transmission electron microscopy revealed differences in the ultrastructural alterations caused by chitosan in the spores of the plant pathogenic fungus and in those of the nematophagous fungus. Confocal laser microscopy showed that Rhodamine‐labelled chitosan enters rapidly into conidia of both fungi, in an energy‐dependent process. Conclusions: Nematophagous and entomopathogenic fungi are rather resistant to the toxic effect of chitosan. Resistance of nematophagous and entomopathogenic fungi to chitosan could be associated with their high extracellular chitosanolytic activity. Furthermore, ultrastructural damage is much more severe in the chitosan sensitive fungus. Significance and impact of the study: The results of this paper suggest that biocontrol fungi tested could be combined with chitosan for biological control of plant pathogens and pests.     

甘油三酯介质中制备壳聚糖纳米粒工艺研究

用乳化溶剂扩散法结合离子沉淀交联法从甘油三酯介质中制备壳聚糖纳米粒,用L9(34)正交设计优选纳米粒制备的处方工艺条件,用显微镜测定纳米粒的粒径,用透射电镜观察纳米粒的形态。结果:正交设计确定纳米粒制备的最优处方工艺条件为:搅拌速度150 r.min-1,壳聚糖质量分数0.10%,壳聚糖分子量9.1万,甘油三酯与壳聚糖酸溶液体积之比200:1,制备的纳米粒平均粒径为(150±50)nm。甘油三酯介质中制备壳聚糖纳米粒工艺简便,制剂具有广泛应用前景。     

Differences in the infectivity of Babesia incubated in plasma and serum and the role of glucose in prolonging viability

Babesia rodhaini was less infective to mice after incubation in rat serum than in rat plasma. This was explained by lower levels of glucose in serum than in plasma. Both serum and plasma were found to become metabolically depleted of glucose following prolonged contact with clotted and unclotted blood cells, respectively. When glucose concentrations in depleted samples were restored to those in freshly separated samples, infectivities of parasites were similar. This was shown for both B. rodhaini and B. argentina. Products of blood cell metabolism, produced when separation of plasma or serum was delayed for 24 h, were not shown to have any detrimental effects on the parasites. Average glucose values for plasma from rats and cattle were 153 mg/100 ml and 63 mg/100 ml, respectively, whereas serum and plasma remaining in contact with blood cells contained as little as 2 mg glucose/100 ml. Lactate values were correspondingly low in plasma and high in serum. Fibrinogen and platelets, factors involved in clotting, did not affect infectivity of B. rodhaini or B. argentina. The relevance of these findings to living babesial vaccines in which plasma- and serum-based diluents may be used is discussed.     

Central lactate metabolism suppresses food intake via the hypothalamic AMP kinase/malonyl-CoA signaling pathway

Previous studies showed that centrally administered glucose and fructose exert different effects on food intake - glucose decreasing and fructose increasing food intake. Because of the uncertainty of whether fructose can cross the blood-brain-barrier, the question is raised; can dietary fructose directly enter the CNS? Evidence is presented that fructose administered by intraperitoneal (ip) injection to mice is rapidly (<10 min) converted to lactate in the hypothalamus. Thus, fructose can cross the blood-brain-barrier to enter the CNS/hypothalamus for conversion to lactate without prior (slower) conversion to glucose in the liver. Fructose-derived hypothalamic lactate is not, however, responsible for the orexigenic effect of fructose. Ip lactate administered at a level equivalent to that of fructose generates a higher level of hypothalamic lactate, which rapidly triggers dephosphorylation/inactivation of AMP-kinase. Thereby, ACC — a substrate of AMP-kinase that catalyzes malonyl-CoA formation — is dephosphorylated and activated. Consistent with these findings, ip or centrally (icv) administered lactate rapidly increases (<10 min) hypothalamic malonyl-CoA. Increasing hypothalamic malonyl-CoA suppresses the expression of the orexigenic and increases the expression of the anorexigenic neuropeptides, which decrease food intake. All downstream effects of hypothalamic lactate are blocked by icv administered oxamate, a potent inhibitor of lactate dehydrogenase, thus verifying the central action of lactate.     

The psychoactive substance of cannabis Δ9-tetrahydrocannabinol (THC) negatively regulates CFTR in airway cells

Background

Marijuana consumption is on the rise in the US but the health benefits of cannabis smoking are controversial and the impact of cannabis components on lung homeostasis is not well-understood. Lung function requires a fine regulation of the ion channel CFTR, which is responsible for fluid homeostasis and mucocilliary clearance. The goal of this study was to assess the effect that exposure to Δ9-tetrahydrocannabinol (THC), the psychoactive substance present in marijuana, has on CFTR expression and function.

Sodium bicarbonate‐gelled chitosan beads as mechanically stable carriers for the covalent immobilization of enzymes

The poor mechanical stability of chitosan has long impeded its industrial utilization as an immobilization carrier. In this study, the mechanical properties of chitosan beads were greatly improved through utilizing the slow rate of the sodium bicarbonate‐induced chitosan gelation and combining it with the chemical cross‐linking action of glutaraldehyde (GA). The GA‐treated sodium bicarbonate‐gelled chitosan beads exhibited much better mechanical properties and up to 2.45‐fold higher observed activity of the immobilized enzyme (β‐D‐galactosidase (β‐gal)) when compared to the GA‐treated sodium tripolyphosphate (TPP)‐gelled chitosan beads. The differences between the sodium bicarbonate‐gelled and the TPP‐gelled chitosan beads were proven visually and also via scanning electron microscopy, elemental analysis, and differential scanning calorimetry. Moreover, the optimum pH, the optimum temperature, the apparent K_m, and the apparent V_max of the β‐gals immobilized onto the two aforementioned types of chitosan beads were determined and compared. A reusability study was also performed. This study proved the superiority of the sodium bicarbonate‐gelled chitosan beads as they retained 72.22 ± 4.57% of their initial observed activity during the 13^th reusability cycle whereas the TPP‐gelled beads lost their activity during the first four reusability cycles, owing to their fragmentation. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:347–361, 2018     

Isolation and Characterization of a Free Gibberellin and Glucosyl Esters of Gibberellins in Mature Seeds of Phaseolus vulgaris

Treatment of N⁶,N⁶,5′-O-tribenzoyl-2′,3′-O-isopropylidenetubercidin (VI) with aqueous acetic acid afforded N⁶,5′-O-dibenzoyltubercidin (V), which was mesylated to yield the dimesylate X. On treatment of X with sodium iodide and zinc dust, the 2′,3′-unsaturated derivatives of tubercidin XI and XIII were obtained.

N⁶,5′-O-Dibenzoyltubercidin 2′,3′-thionocarbonate (XIV), prepared from V by treatment with Corey-Winter reagent, was converted to the 1-methyl-2′,3′-unsaturated derivative XV in refluxing trimethyl phosphite.