Nanoscale Diblock Copolymer Micelles: Characterizations and Estimation of the Effective Diffusion Coefficients of Biomolecules Release through Cylindrical Diffusion Model

Biomolecules have been widely investigated as potential therapeutics for various diseases. However their use is limited due to rapid degradation and poor cellular uptake in vitro and in vivo. To address this issue, we synthesized a new nano-carrier system comprising of cholic acid-polyethylenimine (CA-PEI) copolymer micelles, via carbodiimide-mediated coupling for the efficient delivery of small interfering ribonucleic acid (siRNA) and bovine serum albumin (BSA) as model protein. The mean particle size of siRNA- or BSA-loaded CA-PEI micelles ranged from 100–150 nm, with zeta potentials of +3-+11 mV, respectively. Atomic force, transmission electron and field emission scanning electron microscopy demonstrated that the micelles exhibited excellent spherical morphology. No significant morphology or size changes were observed in the CA-PEI micelles after siRNA and BSA loading. CA-PEI micelles exhibited sustained release profile, the effective diffusion coefficients were successfully estimated using a mathematically-derived cylindrical diffusion model and the release data of siRNA and BSA closely fitted into this model. High siRNA and BSA binding and loading efficiencies (95% and 70%, respectively) were observed for CA-PEI micelles. Stability studies demonstrated that siRNA and BSA integrity was maintained after loading and release. The CA-PEI micelles were non cytotoxic to V79 and DLD-1 cells, as shown by alamarBlue and LIVE/DEAD cell viability assays. RT-PCR study revealed that siRNA-loaded CA-PEI micelles suppressed the mRNA for ABCB1 gene. These results revealed the promising potential of CA-PEI micelles as a stable, safe, and versatile nano-carrier for siRNA and the model protein delivery.     

Micelles of cerebroside sulphate

The critical micelle concentration of cerebroside sulphate in water is 0-01 mM: it increases with increasing concentrations of buffer to 0-07 mM in 0-1 M sodium acetate and formate buffers, pH 5-6 and 4-5 respectively. The partial specific volume of the micelles is about 0-94. The behaviour of the micelles in the ultracentrifuge and on Sephadex G-200 shows them to be grossly heterogeneous with respect to size. In 0-1 M buffer s20,w is about 26 S; in water or 0-01 M buffer smaller micelles with an s20,w of about 6 S are also present. In 0-01 M formate, pH 4-5, the smallest species detectable by equilibrium ultracentrifugation had a micellar weight of about 180,000 corresponding to an aggregation number of about 180. Much larger aggregates were also present. It is suggested that the smallest micelles are the substrate for sulphatase A when this is acting as a cerebroside sulphatase in buffers of low ionic strength.     

Calcium Oscillations

Calcium signaling results from a complex interplay between activation and inactivation of intracellular and extracellular calcium permeable channels. This complexity is obvious from the pattern of calcium signals observed with modest, physiological concentrations of calcium-mobilizing agonists, which typically present as sequential regenerative discharges of stored calcium, a process referred to as calcium oscillations. In this review, we discuss recent advances in understanding the underlying mechanism of calcium oscillations through the power of mathematical modeling. We also summarize recent findings on the role of calcium entry through store-operated channels in sustaining calcium oscillations and in the mechanism by which calcium oscillations couple to downstream effectors.Calcium ions participate in a multiplicity of physiological and pathological functions. Among the most intensely studied, and the major focus of this article, is the role of Ca²⁺ as a cellular signal. Elevations in cytoplasmic Ca²⁺ mediate a plethora of cellular responses, ranging from extremely rapid events (muscle contraction, neurosecretion), to slower more subtle responses (cell division, differentiation, apoptosis). In contrast to most cellular signals, it is a relatively simple matter to observe changes in cytoplasmic Ca²⁺ in real time in living cells. As a result, the truly complex nature of Ca²⁺ signaling pathways has been revealed. The challenge is to understand what regulates these signals and what the biological significance of their complexity is.In the majority of laboratory experiments examining effects of various stimulants on Ca²⁺ signaling, supramaximal concentrations of activating agonists are employed resulting in rapid, robust, and often sustained increases in cytoplasmic Ca²⁺. It has long been appreciated that these signals result from a coordinated release of intracellular stores and increased Ca²⁺ influx across the plasma membrane (Bohr, 1973; Putney et al. 1981). The intracellular release of Ca²⁺ most commonly results from the Ca²⁺ releasing action of the phospholipase C-derived second messenger, inositol 1,4,5-trisphosphate (InsP₃) (Streb et al. 1983), whereas the entry of Ca²⁺ is because of the activation of store-operated channels in the plasma membrane (Putney 1986). However, it is becoming increasingly clear that these large sustained elevations seldom occur with physiological levels of stimulants. Rather the more common pattern of Ca²⁺ signaling, in both excitable and nonexcitable cells is a pattern of periodic discharges and/or entry of Ca²⁺. In excitable cells, such as the heart for example, these may be comprised of, or initiated by regenerative all-or-none plasma membrane channel activation, the Ca²⁺ action potential (Tsien et al. 1986) with amplification by intracellular Ca²⁺ release (Fabiato 1983). In nonexcitable cells, these spikes of cytoplasmic Ca²⁺ arise from regenerative discharge of stored Ca²⁺, a process generally termed Ca²⁺ oscillations (Prince and Berridge 1973; Woods et al. 1986). Like Ca²⁺ action potentials, these all-or-none discharges of Ca²⁺ represent a form of excitable behavior of the intracellular Ca²⁺ release signaling mechanism. However, because it is not possible to easily monitor and control the transmembrane chemical and biophysical parameters, as is the case for excitable plasma membrane behavior, it has been more difficult to fully understand the basic mechanisms by which these Ca²⁺ oscillations arise. Thus, although the question has been exhaustively studied for well over twenty years, there is still uncertainty and controversy over the underlying processes that give rise to Ca²⁺ oscillations. A number of reviews have discussed these issues at some length (Berridge and Galione 1988; Rink and Jacob 1989; Berridge 1990; Petersen and Wakui 1990; Berridge 1991; Cuthbertson and Cobbold 1991; Meyer and Stryer 1991; Hellman et al. 1992; Tepikin and Petersen 1992; Thomas et al. 1992; Dupont and Goldbeter 1993; Keizer 1993; Sneyd et al. 1994; Li et al. 1995; Thomas et al. 1996; Shuttleworth 1999; Lewis 2003; Dupont et al. 2007). In the current treatment, we have chosen to focus on two important aspects of Ca²⁺ oscillations. First, we review the available evidence for various computational models of Ca²⁺ oscillations that employ a quantitative approach to validate or repudiate specific mechanisms. Second, we consider the interrelationship between Ca²⁺ oscillations and plasma membrane Ca²⁺ influx mechanisms, with the view that we may learn more of the physiological function that these intracellular discharges of Ca²⁺ provide.     

反胶束萃取胰蛋白酶的研究

本文以含有反胶束的有机溶剂作为萃取剂,进行了将胰蛋白酶从水相传入有机相,再从有机相传入另一水相的研究。结果表明：影响萃取率的主要因素为水相ｐＨ值、离子强度和种类,以及反胶束溶液中表面活性剂浓度等;在适宜的条件下,酶的单级萃取和反萃取率都很高,显示了良好的工业应用前景。     

Oscillations and hippocampal-prefrontal synchrony

The hippocampus and medial prefrontal cortex subserve spatial working memory in rodents. Recent evidence has demonstrated functional interactions between these brain regions in the form of sychronization of oscillatory activity during behavior. The nature of this synchrony and its relationship to behavioral performance suggests an important role in the function of the hippocampal-prefrontal circuit.     

Oscillations in energy metabolism

Organisation of mitochondrial metabolism is a quintessential example of a complex dissipative system which can display dynamic instabilities. Several findings have indicated that the conditions inducing instabilities are within the physiological range and that mild perturbations could elicit oscillations. Different mathematical models have been put forth in order to explain the genesis of oscillations in energy metabolism. One model considers mitochondria as an organised network of oscillators and indicates that communication between mitochondria involves mitochondrial reactive oxygen species (ROS) production acting as synchronisers of the energy status of the whole population of mitochondria. An alternative model proposes that extramitochondrial pH variations could lead to mitochondrial oscillations. Oscillatory phenomena in energy metabolism have also been investigated in vivo on the basis of ³¹P magnetic resonance spectroscopy (MRS) measurements of phosphocreatine post-exercise recovery in human and animal skeletal muscle. The corresponding results provide experimental evidences about the role exerted by cytosolic pH on oscillations. Finally a new simple non-linear mathematical model describing the overall chemical reaction of phosphocreatine recovery predicting oscillatory recovery pattern under certain experimental conditions is presented and discussed in the light of the experimental results reported so far.     

Oscillations following periodic reinforcement

Three experiments examined behavior in extinction following periodic reinforcement. During the first phase of Experiment 1, four groups of pigeons were exposed to fixed interval (FI 16 s or FI 48 s) or variable interval (VI 16 s or VI 48 s) reinforcement schedules. Next, during the second phase, each session started with reinforcement trials and ended with an extinction segment. Experiment 2 was similar except that the extinction segment was considerably longer. Experiment 3 replaced the FI schedules with a peak procedure, with FI trials interspersed with non-food peak interval (PI) trials that were four times longer. One group of pigeons was exposed to FI 20 s PI 80 s trials, and another to FI 40 s PI 160 s trials. Results showed that, during the extinction segment, most pigeons trained with FI schedules, but not with VI schedules, displayed pause-peck oscillations with a period close to, but slightly greater than the FI parameter. These oscillations did not start immediately after the onset of extinction. Comparing the oscillations from Experiments 1 and 2 suggested that the alternation of reconditioning and re-extinction increases the reliability and earlier onset of the oscillations. In Experiment 3 the pigeons exhibited well-defined pause-peck cycles since the onset of extinction. These cycles had periods close to twice the value of the FI and lasted for long intervals of time. We discuss some hypotheses concerning the processes underlying behavioral oscillations following periodic reinforcement.     

脂肪酶在反相胶囊中的催化行为的研究

系统研究了脂肪酶在ＡＯＴ／水／异辛烷反应相胶囊中的催化行为。在一定条件下,反相胶囊中的酶反应的仍符合Ｍｉｃｈａｅｌｉｓ－Ｍｅｎｔｅｎ动力学原理,研究了含水量,底物浓度,ｐＨ,温度,溶剂的种类和表面活性剂浓度等对酶反应的影响。结果表明,酶活力与Ｒ值（水与表面活性剂的摩尔比值）有关。获得最大酶活力的条件是Ｒ＝１１,ｐＨ７．０,温度３２．５℃,橄榄油浓度为４０％。     

Polymeric Micelles for Multi-Drug Delivery in Cancer

Drug combinations are common in cancer treatment and are rapidly evolving, moving beyond chemotherapy combinations to combinations of signal transduction inhibitors. For the delivery of drug combinations, i.e., multi-drug delivery, major considerations are synergy, dose regimen (concurrent versus sequential), pharmacokinetics, toxicity, and safety. In this contribution, we review recent research on polymeric micelles for multi-drug delivery in cancer. In concurrent drug delivery, polymeric micelles deliver multi-poorly water-soluble anticancer agents, satisfying strict requirements in solubility, stability, and safety. In sequential drug delivery, polymeric micelles participate in pretreatment strategies that “prime” solid tumors and enhance the penetration of secondarily administered anticancer agent or nanocarrier. The improved delivery of multiple poorly water-soluble anticancer agents by polymeric micelles via concurrent or sequential regimens offers novel and interesting strategies for drug combinations in cancer treatment.KEY WORDS: controlled release, drug combination, drug delivery, drug solubilization, polymeric micelles     

载紫杉醇共聚物胶束的合成与表征

目的：制备一种包封率、载药量高的紫杉醇载体材料。方法：开环聚合法一步合成了两种两亲性共聚物PTL1和PTL2,以核磁和凝胶渗透色谱进行了产物的表征,以固体分散一超声法制备紫杉醇胶束,考察了胶束的载药量、包封率。结果：核磁和凝胶渗透色谱的结果显示得到了目标产物,所制备得到的载紫杉醇胶束包封率可以达到90％以上,载药量为9．5％以上。结论：实验结果表明我们所合成的PTL1和PTL2是好的紫杉醇栽体材料。     

反胶束萃取血红蛋白的研究

研究了ＣＴＡＢ－正辛醇－正庚烷交束溶液萃取牛血红蛋白（ｐＨｂ）时、ｐＨ值、表面活性剂浓度、助表面活性剂浓度、离子种类和离子强度、溶剂比以及蛋白质浓度等因素对萃取效果的影响,并以蛋白质分子与表面活性剂分子间的相互作用以及反胶束大空间阻碍作用上进行了解释。研究表明,水相ＰＨ值在１０．５￣１２．５之间,ＫＣ１浓度为０．１ｍｏｌ／ｌ,反胶束溶液中表面活性剂浓度为０．０２ｍｏｌ／ｌ,正辛醇与正庚烷之比为０．     

Oscillations of the collisionless sheath

An Eulerian-Vlasov code is used to study the properties of a collisionless sheath with grazing incidence of the magnetic field. In the case where the ion gyroradius is large compared to the Debye length, the electrons, frozen by the magnetic field lines, have to move rapidly along the magnetic field B in their attempt to follow the ions gyrating perpendicular to B. Below a critical angle, the electrons moving parallel to B can no longer follow the gyrating ions and low-frequency oscillations appear in the system. Published in Russian in Fizika Plazmy, 2008, Vol. 34, No. 9, pp. 812–815. The text was submitted by the authors in English.     

Oscillations in Yeast Observed Electrically

It has previously been demonstrated that oscillations occur in actively growing yeast cultures. These oscillations occur because yeast cells synchronize their glycolytic pathway following a saturation period. Periodic changes in the levels of intermediate metabolites in glycolysis as well as changes in pH ofthe media have been measured, that demonstrate this phenomenon. Here we observe that the conductivity of the media also changes periodically when yeast cells are cultured under similar conditions. As conductivity is easily measured, this provides a simple, more quantitative method to study these changes than those currently used. An electrical biosensor referred to as ECIS (electrical cell surface impedance sensing) was used to study the small conductivity changes (in the order of 0.1%). No significant differences in the observed periods were found in the two yeast strains or the commercially purchased yeast extract studied.     

Oscillations in Yeast Observed Electrically

It has previously been demonstrated that oscillations occur in actively growing yeast cultures. These oscillations occur because yeast cells synchronize their glycolytic pathway following a saturation period. Periodic changes in the levels of intermediate metabolites in glycolysis as well as changes in pH ofthe media have been measured, that demonstrate this phenomenon. Here we observe that the conductivity of the media also changes periodically when yeast cells are cultured under similar conditions. As conductivity is easily measured, this provides a simple, more quantitative method to study these changes than those currently used. An electrical biosensor referred to as ECIS (electrical cell surface impedance sensing) was used to study the small conductivity changes (in the order of 0.1%). No significant differences in the observed periods were found in the two yeast strains or the commercially purchased yeast extract studied.     

Bloch Oscillations: Inverse Problem

We use a neural network approach to explore the inverse problem of Bloch oscillations in a monoatomic linear chain: given a signal describing the path of oscillations of electrons as a function of time, we determine the strength of the applied field along the direction of motion or, equivalently, the lattice spacing. We find that the proposed approach has more than 80% of accuracy classifying the studied physical parameters.     

Oscillations in erythrocyte membrane preparations

The ratio of weakly and strongly immobilized populations of membrane-bound maleimide spin label, the excimer to monomer fluorescence ratio of membrane-embedded pyrene, and acetylcholinesterase activity, were evaluated in bovine erythrocyte membrane preparations incubated at 37 degrees C. Oscillations were evident in the values obtained, and the periods of these oscillations were in the range of 1.3 to 1.6 h.     

美在洛克路

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