Gas-tight Syringe Research Articles

A Comparison of the Transplant Efficiency between Intraportal and Intrasplenic Procedures in Hepatocyte Transplantation

Background In hepatocyte transplantation, intraportal injection is regarded as the current standard procedure worldwide. However, there have been some reports that an intrasplenic approach is more efficient in terms of the engraftment and function of hepatocytes. Of particular interest, in pancreatic islet transplantation, which shares many aspects with hepatocyte transplantation, an intrasplenic method was recently proven to be superior to the intraportal method regarding islet engraftment. Therefore, in the present study, we compared the transplant efficiency between intraportal and intrasplenic approaches in hepatocyte transplantation. Methods Rat hepatocytes were isolated using a modified two-step collagenase perfusion technique and then purified by Percoll density gradient centrifugation. Hepatocytes (1.0 × 107) with a viability exceeding 90% were directly injected into the portal vein (n=8) or spleen pulp (n=8) of analbuminemic rats using a gastight syringe for 60 seconds. Blood samples were taken pre-transplantation and at weeks 2, 4, 6, 8, 10, 12, and 16 after transplantation. The serum albumin levels were quantified using a rat albumin enzyme-linked immunosorbent assay kit. Results The serum albumin levels of the intrasplenic group (pre-transplantation: 7.55±0.65 μg/ml, Week 2: 55.00±21.02 μg/ml, Week 4: 79.88±32.62 μg/ml, Week 6: 105.96±54.46 μg/ml, Week 8: 114.73±58.34 μg/ml, Week 10: 116.11±56.33 μg/ml, Week 12: 122.76±60.85 μg/ml, and Week 16: 133.96±66.03 μg/ml, respectively) were significantly lower than those of the intraportal group (pre-transplantation: 8.26±0.79 μg/ml, Week 2: 100.43±38.48 μg/ml, Week 4: 159.24±58.04 μg/ml, Week 6: 181.31±68.61 μg/ml, Week 8: 185.66±71.44 μg/ml, Week 10: 188.96±74.46 μg/ml, Week 12: 190.73±73.91 μg/ml and Week 16: 191.70±78.06 μg/ml, respectively, P<0.0001). Conclusions The present study clearly showed that the intraportal injection procedure is more efficient than the intrasplenic procedure for performing hepatocyte transplantation.

Nitric Oxide Reactivity of a Cu(II) Complex of an Imidazole-Based Ligand: Aromatic C-Nitrosation Followed by the Formation of N-Nitrosohydroxylaminato Complex

A binuclear Cu(II) complex, 1, [Cu2(L-)2(OAc)](OAc) of imidazole-based ligand LH {LH = 2-(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)phenol} was synthesized and characterized spectroscopically and structurally. Addition of an equivalent amount of nitric oxide (NO) by a gastight syringe to the acetonitrile:methanol (5:1, v/v) solution of complex 1 at room temperature resulted in the reduction of Cu(II) center to Cu(I) with concomitant C-nitrosation of the ligand. Spectroscopic characterization of the resulting Cu(I) complex (1a) of the C-nitrosylated ligand, L' {L' = 2-(bis(2-ethyl-5-methyl-1H-imidazol-4-yl)methyl)-4-nitroso-phenol} has been done. The Cu(I) complex, 1a, further reacted with NO to result in the corresponding N-nitrosohydroxylaminato complex, 2, [Cu2(L-ONNO)2](OAc)2 through the formation of a Cu(I)-nitrosyl intermediate. A small fraction of the nitrosyl intermediate decomposed to the corresponding Cu(II) complex 3, [Cu(L')2], and N2O in a parallel reaction.

Development and characterization of an oro-nasal inhalation plethysmography mask exposure system

ABSTRACTAn oro-nasal inhalation plethysmography mask exposure system (ONIPMES) was developed to challenge nonhuman primates and rabbits with biological agents while determining real-time respiratory parameters. The system included novel challenge plethysmography and sample collection masks that delivered aerosol directly to the breathing zone of the animals and to the sample collection probes. Challenge plethysmography masks were fitted with a differential pressure transducer that interfaced with a signal amplifier and computer software to quantify respiratory tidal volume, frequency, and minute volume. Challenge plethysmography masks were calibrated and verified with certified registered gas-tight syringes. Accuracy was determined from simultaneous comparison tests between the challenge plethysmography mask and head-out plethysmographs using live animals. For cynomolgus macaques, the mean differences in tidal volume, frequency, and minute volume were 4.20 ± 0.872 mL, 3.50 ± 3.15 breaths per minute (bpm),...

Micropore extrusion-induced alignment transition from perpendicular to parallel of cylindrical domains in block copolymers.

The orientation transition from perpendicular to parallel alignment of PEO cylindrical domains of PEO-b-PMA(Az) films has been demonstrated by extruding the block copolymer (BCP) solutions through a micropore of a plastic gastight syringe. The parallelized orientation of PEO domains induced by this micropore extrusion can be recovered to perpendicular alignment via ultrasonication of the extruded BCP solutions and subsequent annealing. A plausible mechanism is proposed in this study. The BCP films can be used as templates to prepare nanowire arrays with controlled layers, which has enormous potential application in the field of integrated circuits.

Opening of the blood-brain barrier through focused ultrasound in combination with drugs to treat glioma

Objective To evaluate the effectiveness of treating glioma in combination with drugs multiply by comparing the size of tumor and the survival time of different groups in rat glioma after targeted blood-brain barrier (BBB) disruption by MRI-guided focused ultrasound. Methods The stereotaxis instruments and the 10 μl gas-tight syringes were used to inject gliosarcoma cells into the targeted area of the brain in 50 male Sprague-Dawley rats. The glioma-bearing rat model was established. Each rat received either: (1) no treatment (control; n=8); (2) single liposomal doxorubicin (DOX; n=10); (3) multiple DOX (n=10); (4) single Avastin (AVS) and DOX (n=10); (5) multiple AVS and DOX (n=10). The SonoVue microbubble ultrasonic contrast agent and DOX or AVS were injected into the tail vein respectively on day 12 after implantation. The tumor size was measured by MRI on pre-treatment, immediacy and once a week of post-treatment after targeted BBB disruption by focused ultrasound, and the life span in rat glioma was recorded. Results The mediam survival of different groups in rat glioma(The range of the life span 13-90 d): no treatment (7 d); single DOX (12 d); multiple DOX (15 d); single AVS+ DOX (22 d), multiple AVS+ DOX (30 d). There was significant difference of the groups on mediam survival comparison (P<0.01). The tumor growth pattern after post-treatment of different groups in rat glioma except control: single DOX was noticeable fast and multiple AVS+ DOX was visibly delayed comparable to other groups, and finally the tumor size of multiple AVS+ DOX even became small. Conclusions The microbubble blasting enhances the local tissue permeability and promotes the drug delivery of chemotherapy and anti-angiogenesis locally in glioma-bearing rats by MRI-guided focused ultrasound. Especially, the combination with drugs multiply has a synergism efficacy that may enhance the effectiveness of chemotherapy, reduce tumor growth, and even become small of the tumor size, and increase survival time significantly after BBB disruption. Key words: High-intensity focused ultrasound; Blood brain barrier; Liposome; Microbubbles; Glioma

Test on the Reliability of Gastight Syringes as Transfer/Storage Media for Gaseous VOC Analysis: The Extent of VOC Sorption between the Inner Needle and a Glass Wall Surface

A gastight syringe (GTS) is commonly used as a medium for transfer or storage of gaseous standards (or samples) in the analysis of volatile organic compounds (VOCs). In this study, the sorptive loss patterns of 21 VOCs were examined, using GTS as the transfer medium. The results of the test were evaluated with respect to a number of key variables including concentration, sampling volume, and physicochemical properties (molecular weight and boiling point). The VOCs with relatively high volatility (Group 1: aldehyde, ketone, ester, alcohol, and aromatic hydrocarbons (n = 12)) showed low sorptive losses with a mean (±SD) of 2.56 ± 2.87%, regardless of differences in the aforementioned key variables (p-value by t-test before and after using GTS = mean 0.15 ± 0.13). Conversely, the sorptive losses of seven semi-VOCs (Group 2: carboxyl and cresol (n = 9)) were significantly high, ranging from 18.0 ± 4.10% (propionic acid) to 65.4 ± 10.9% (n-heptanonic acid). In addition, we also measured the sorptive losses on the syringe needle (mean sorptive loss of Group 2 = 5.94 ± 5.63%). A linear regression analysis showed that the sorptive losses for Group 2 increased as molecular weight (or boiling point) increased, exhibiting a highly significant correlation (R(2) value (0.804 ± 0.084) and mean p-value (0.002 ± 0.003).

Use of a gas-tight syringe sampling method for the determination of tobacco-specific nitrosamines in E-cigarette aerosols by liquid chromatography-tandem mass spectrometry

We report here a sampling method using a gas-tight syringe (GTS) in the determination of tobacco-specific nitrosamines (TSNAs) in aerosols from electronic cigarettes.

Opening of the blood-brain barrier through focused ultrasound in combination of drugs to treat glioma

Objective To evaluate the effectiveness of treating glioma in combination of two kinds of drugs by comparing the size of tumors and the survival time of different groups in rat glioma after targeted blood-brain barrier （BBB） disruption by focused ultrasound under MRI-guide. Methods The stereotaxis instruments and the 10 μl gas-tight syringes were used to inject gliosarcoma cells into the targeted area of the brain in 40 male Sprague-Dawley rats. The glioma-bearing rats models were established. Rats were divided into 4 groups to receive different treatment： （1） no treatment （control, n = 8）, （2） IV Avastin （Avastin only, n = 10）, （3） IV liposomal doxorubicin （DOX only, n = 10）, （4） IV Avastin and liposomal doxorubicin （Avastin ＋ DOX, n = 10）.The SonoVue mierobubbles and DOX or Avastin were injected into the tail vein respectively on the 12th day after implantation. The tumor size was measured by MRI on immediacy,once a week after targeted BBB disruption by focused ultrasound,and the life span in rat glioma was recorded. Results The average survival time of different groups in rat glioma was as follows： no treatment（17 ± 4）d,Avastin（20 ± 4）d,DOX（25 ± 5）d,DOX ± Avastin（40± 5）d.The tumor size after post- treatment of different groups in rat glioma was as follows： no treatment（5.70 ± 4.30） mm, Avastin（4.30 ± 2.50） mm, DOX （4.12± 3.10） mm, DOX ＋ Avastin （2.20±1.30） mm. There was significant increased in average survival time and decreased in tumor size after a combination treatment DOX ＋ Avastin compared with other groups（ P 〈0.01）.Conclusions The microbubble blasting by MRI-guided focused ultrasound enhances the local tissue permeability and promotes the drug delivery of chemotherapy and anti-angiogenesis locally in glioma-hearing rats.Especially, the combination of two kinds of drugs has a synergism efficacy that may reduce tumor growth and increase survival time significantly after BBB disruption. Key words: Ultrasound, high-intensity focused ; Blood-brain barrier ; Glioma ; Microbubbles ; Liposome

Competitive kinetics study of sulfide oxidation by chlorine using sulfite as reference compound

To design and optimize hydrogen sulfide scrubbers working with chlorine, the knowledge of the kinetics of the hydrogen sulfide oxidation is necessary. In this work, the kinetics of the hydrogen sulfide oxidation by sodium hypochlorite was experimentally investigated using a reactor without headspace (100mL gas-tight syringe) and the competitive kinetics method. The sulfite ion was selected as the reference compound. First, the apparent stoichiometries of sulfite anion and hydrogen sulfide chlorinations were determined performing single-compound experiments. Then, the kinetics of the hydrogen sulfide chlorination was studied in the pH range 6–12 performing simultaneous sulfite and sulfide chlorinations. The results demonstrated that sulfide and sulfite oxidation kinetic rates have the same order of magnitude, which validates the choice of the sulfite anion as the reference compound. Kinetic simulations emphasized that the kinetic rates of the oxidation of both compounds were limited by acid–base reactions. The sulfide oxidation in the pH range 6–12 is mainly due to the hydrosulfide (HS−) oxidation by the hypochlorous acid (ClOH) with an associated kinetic constant of 1.2×109Lmol−1s−1 at 25°C.

Analytical strategies based on multiple headspace extraction for the quantitative analysis of aroma components in mushrooms.

Headspace (HS) and headspace solid phase microextraction (HS-SPME) analysis by gas chromatography-mass spectrometry (GC/MS) have been found to be suitable methods for the analysis of volatile organic compounds. The objectives of this paper are to study the possibilities of multiple headspace extraction (MHE) for the quantitative determination of volatile compounds in mushroom samples and to compare the results obtained using three different sample treatment techniques. For this purpose, HS with two different injection techniques (pressure-loop system and gas-tight syringe autosampling system) and HS-SPME have been studied. Three processes were optimized for the analysis of 20 volatile compounds by experimental design technique based on Central Composite Design (CCD) and Full Factorial Design depending on the used methodology. Once the designs were finished, a trade off among optimum conditions for each compound analyzed was reached. At optimum conditions, appropriate extraction time and sample amount for the three techniques used were established. Finally, the methods were validated in terms of linearity, detection and quantitation limits and repeatability. The most suitable method was then applied to the quantitative analysis of seven mushroom samples. A detailed comparison of the analytical performance characteristics of HS and HS-SPME as sample treatment techniques for final GC/MS determination is given. In addition, MHE has been proved to be an adequate technique to avoid matrix effects in complex samples quantitation. Its applicability to the determination of volatile mushroom components, along with its limitations, is discussed in this work.

기체질량분석기를 이용한 유정란 부화과정의 호흡량 분석

유정란의 부화과정 동안 소모되는 산소와 배출되는 이산화탄소의 양을 기체질량분석기를 사용하여 측정하였다. 20 일에 걸친 유정란과 무정란의 인공부화 과정 동안 기체 시료를 채취하기 위해 밀폐된 구조의 시료 챔버를 제작하였다. 2~4 일 간격으로 시료 챔버 안에 유정란을 1 시간 동안 방치한 후, 실린지를 이용해 밀폐된 시료 챔버로부터 2 mL의 기체 시료를 채취한 후 기체질량분석기를 사용하여 분석하였다. 인공부화를 시작한 후 약 10 일 후부터 닭 배아의 산소 소모량과 이산화탄소 배출량이 급격히 증가하였다. 20 일 후에는 시간당 23 mL의 산소를 소모하고 16 mL의 이산화탄소를 배출하였다. 전체 부화 기간 동안 산소의 농도는 4.3 mol% 감소하였고 이산화탄소의 농도는 3.1 mole% 증가하여 소모된 산소의 몰수와 배출된 이산화탄소의 몰수가 같지 않았다. 한편, 동일한 기간 동안 질소의 농도는 약 1.3 mol% 증가하였으며 그 증가된 농도는 소모된 산소와 배출된 이산화탄소의 농도변화량의 차이와 비슷한 값을 보였다. 따라서 질소의 몰분율 증가는 소모된 산소와 배출된 이산화탄소 간의 몰분율 차이에 의한 것임을 알 수 있었다. 본 연구에서는 기체의 조성 변화량을 정확히 측정하여 유정란의 부화과정 중 호흡현상을 설명할 수 있었다. Oxygen(<TEX>$O_2$</TEX>) consumption and carbon dioxide(<TEX>$CO_2$</TEX>) excretion of a fertile chicken egg during incubation were measured by a gas mass spectrometer. A closed sample chamber was developed to collect gas samples during the 20 days of artificial incubation of both a fertile and an infertile egg. After leaving an egg in the sample chamber for an hour, using a gas-tight syringe, samples of 2 mL of gas were collected from the closed sample chamber and analyzed using a gas mass spectrometer in 2~4 day intervals. The <TEX>$O_2$</TEX> consumption and <TEX>$CO_2$</TEX> excretion of chicken embryos increased rapidly after 10 days from the starting point of incubation. After 20 days, 23 mL of <TEX>$O_2$</TEX> was consumed and 16 mL of <TEX>$CO_2$</TEX> was excreted per hour. Throughout the whole period of incubation, concentration of <TEX>$O_2$</TEX> decreased 4.3 mol% and <TEX>$CO_2$</TEX> increased only 3.1 mole%, i.e., the mole of consumed <TEX>$O_2$</TEX> and the mole of excreted <TEX>$CO_2$</TEX> were not the same. On the other hand, during the same period, concentration of <TEX>$N_2$</TEX> increased about 1.3 mol% and the increased mole fraction of <TEX>$N_2$</TEX> was comparable with the difference (1.2 mol%) between the mole fraction of consumed <TEX>$O_2$</TEX> and excreted <TEX>$CO_2$</TEX>. Therefore, we can attribute the increase of <TEX>$N_2$</TEX> mole% to the difference of mole fraction between consumed <TEX>$O_2$</TEX> and excreted <TEX>$CO_2$</TEX>. In this study, through the analysis of gas, we could explain the respiration of a fertile chicken egg during incubation.

SIMULTANEOUS DETERMINATION OF VITAMIN A AND E IN INFANT MILK FORMULAS USING SEMI-MICRO LIQUID–LIQUID EXTRACTION FOLLOWED BY HPLC-UV

An efficient and inexpensive semi-micro liquid–liquid extraction method has been developed for simultaneous clean-up and extraction of vitamin A and vitamin E in infant milk formula samples. After saponification of milk samples, extraction procedure was done in a 5-mL volumetric flask. 4.5 mL of saponified sample solution was added to the volumetric flask, and then 300 µL of organic solvent was added slowly to the surface of the saponified solution in the neck of the flask by a gas tight micro syringe. The mixture was agitated during the extraction time. After the extraction time a prescribed amount of organic phase was withdrawn, evaporated and reconstituted with methanol and finally was injected into the HPLC system for analysis. The proposed method provided good reproducibility (3.9–5.1%), good linearity (0.006–80 µg mL−1 for vitamin A and 0.1–400 µg mL−1for vitamin E), low detection limits (0.003 µg mL−1 for vitamin A and 0.08 µg mL−1 for vitamin E), and was a simple, low cost, efficient, and easy handling technique for determination of vitamin A and E according to the results obtained. Furthermore, using monolithic column has the advantage of decreasing the total time of analysis.

Rapid offline isotopic characterisation of hydrocarbon gases generated by micro-scale sealed vessel pyrolysis

The method of offline coupling of micro-scale sealed vessel pyrolysis (MSSV-Py) and gas chromatography–isotopic ratio mass spectrometry (GC–IRMS) was developed using a purpose built gas sampling device. The sampling device allows multiple GC and GC–IRMS injections to quantify the molecular composition and isotopic evolution of hydrocarbon gases (n-C1 to n-C5) generated by artificial maturation of sedimentary organic matter. Individual MSSV tubes were introduced into the gas sampling device, which was then evacuated to remove air and filled with helium at atmospheric pressure. The tube was crushed using a plunger after which the device was heated at 120°C for 1min to thermally mobilise and equilibrate the generated gas products. Aliquots of the gas phase were sampled using a gas tight syringe and analysed via GC–FID and GC–IRMS. Hydrocarbon gas yields using this technique have been calculated and compared with those obtained previously by online MSSV pyrolysis of the same samples under the same conditions. The major objective of this study was to investigate the potential isotopic fractionation of generated gaseous hydrocarbons within the gas sampling device as a function of time and temperature. For this purpose several tests using a standard gas mixture have been performed on the GC–IRMS. The analyses showed no isotopic fractionation of C1–5 hydrocarbons within 1h, minor δ13C enrichment after 5h, and significant enrichment after 22h for all the compounds at a temperature of 120°C.

Equilibrium distribution sampling device for preparation of calibration mixtures for gas chromatography-mass spectrometry

A simple approach for preparing standard mixtures of volatile and semi-volatile organic compounds is reported. When placed in a closed container, standard mixture components partition between a polymeric material such as poly(dimethylsiloxane) (PDMS) and headspace to provide constant vapor concentrations. The granular form of heat-conditioned PDMS provides rapid equilibration with the headspace vapor and serves as a standard reservoir. Solid phase micro extraction (SPME) or gas-tight syringe can be used to deliver sample from the headspace to the analytical instrument. Quantitative calibration can be achieved with either active temperature control or by using a previously constructed look-up table. The effects of PDMS form and temperature on equilibrium distribution, initial equilibrium time, and re-equilibrium time after sampling were investigated. With respect to long term use and stability, analytes introduced onto 2.0 g of PDMS in a 7.4 mL vial were sampled more than 114 times during a test period of 43 days, giving chromatographic peak area %RSD values below 4.5% for all compounds. This device was designed to be solventless, quantitative, reproducible, environmentally friendly, and robust for routine evaluation and calibration of gas chromatography-mass spectrometry (GC-MS) systems.

Novel Activation of Voltage-gated K+ Channels by Sevoflurane

Halogenated inhaled anesthetics modulate voltage-gated ion channels by unknown mechanisms. Biophysical analyses revealed novel activation of K(v) channels by the inhaled anesthetic sevoflurane. K(v) channel activation by sevoflurane results from the positive allosteric modulation of activation gating. The unique activation of K(v) channels by sevoflurane demonstrates novel anesthetic specificity and offers new insights into allosteric modulation of channel gating. Voltage-gated ion channels are modulated by halogenated inhaled general anesthetics, but the underlying molecular mechanisms are not understood. Alkanols and halogenated inhaled anesthetics such as halothane and isoflurane inhibit the archetypical voltage-gated Kv3 channel homolog K-Shaw2 by stabilizing the resting/closed states. By contrast, sevoflurane, a more heavily fluorinated ether commonly used in general anesthesia, specifically activates K-Shaw2 currents at relevant concentrations (0.05-1 mM) in a rapid and reversible manner. The concentration dependence of this modulation is consistent with the presence of high and low affinity interactions (K(D) = 0.06 and 4 mM, respectively). Sevoflurane (<1 mM) induces a negative shift in the conductance-voltage relation and increases the maximum conductance. Furthermore, suggesting possible roles in general anesthesia, mammalian Kv1.2 and Kv1.5 channels display similar changes. Quantitative description of the observations by an economical allosteric model indicates that sevoflurane binding favors activation gating and eliminates an unstable inactivated state outside the activation pathway. This study casts light on the mechanism of the novel sevoflurane-dependent activation of Kv channels, which helps explain how closely related inhaled anesthetics achieve specific actions and suggests strategies to develop novel Kv channel activators.

Determination of ammonium in aqueous samples using new headspace dynamic in-syringe liquid-phase microextraction with in situ derivitazation coupled with liquid chromatography–fluorescence detection

A new simultaneous derivatization and extraction method for the preconcentration of ammonia using new one-step headspace dynamic in-syringe liquid-phase microextraction with in situ derivatization was developed for the trace determination of ammonium in aqueous samples by liquid chromatography with fluorescence detection (LC–FLD). The acceptor phase (as derivatization reagent) containing o-phthaldehyde and sodium sulfite was held within a syringe barrel and immersed in the headspace of sample container. The gaseous ammonia from the alkalized aqueous sample formed a stable isoindole derivative with the acceptor phase inside the syringe barrel through the reciprocated movements of plunger. After derivatization-cum-extraction, the acceptor phase was directly injected into LC–FLD for analysis. Parameters affecting the ammonia evolution and the extraction/derivatization efficiency such as sample matrix, pH, temperature, sampling time, and the composition of derivatization reagent, reaction temperature, and frequency of reciprocated plunger, were studied thoroughly. Results indicated that the maximum extraction efficiency was obtained by using 100μL derivatization reagent in a 1-mL gastight syringe under 8 reciprocated movements of plunger per min to extract ammonia evolved from a 20mL alkalized aqueous solution at 70°C (preheated 4min) with 380rpm stirring for 8min. The detection was linear in the concentration range of 0.625–10μM with the correlation coefficient of 0.9967 and detection limit of 0.33μM (5.6ngmL−1) based on SN−1=3. The method was applied successfully to determine ammonium in real water samples without any prior cleanup of the samples, and has been proved to be a simple, sensitive, efficient and cost-effective procedure for trace ammonium determination in aqueous samples.

Constant Pressure-controlled Extrusion Method for the Preparation of Nano-sized Lipid Vesicles

Liposomes are artificially prepared vesicles consisting of natural and synthetic phospholipids that are widely used as a cell membrane mimicking platform to study protein-protein and protein-lipid interactions, monitor drug delivery, and encapsulation. Phospholipids naturally create curved lipid bilayers, distinguishing itself from a micelle. Liposomes are traditionally classified by size and number of bilayers, i.e. large unilamellar vesicles (LUVs), small unilamellar vesicles (SUVs) and multilamellar vesicles (MLVs). In particular, the preparation of homogeneous liposomes of various sizes is important for studying membrane curvature that plays a vital role in cell signaling, endo- and exocytosis, membrane fusion, and protein trafficking. Several groups analyze how proteins are used to modulate processes that involve membrane curvature and thus prepare liposomes of diameters <100 - 400 nm to study their behavior on cell functions. Others focus on liposome-drug encapsulation, studying liposomes as vehicles to carry and deliver a drug of interest. Drug encapsulation can be achieved as reported during liposome formation. Our extrusion step should not affect the encapsulated drug for two reasons, i.e. (1) drug encapsulation should be achieved prior to this step and liposomes should retain their natural biophysical stability, securely carrying the drug in the aqueous core. These research goals further suggest the need for an optimized method to design stable sub-micron lipid vesicles. Nonetheless, the current liposome preparation technologies (sonication, freeze-and-thaw, sedimentation) do not allow preparation of liposomes with highly curved surface (i.e. diameter <100 nm) with high consistency and efficiency, which limits the biophysical studies of an emerging field of membrane curvature sensing. Herein, we present a robust preparation method for a variety of biologically relevant liposomes. Manual extrusion using gas-tight syringes and polycarbonate membranes, is a common practice but heterogeneity is often observed when using pore sizes <100 nm due to due to variability of manual pressure applied. We employed a constant pressure-controlled extrusion apparatus to prepare synthetic liposomes whose diameters range between 30 and 400 nm. Dynamic light scattering (DLS), electron microscopy and nanoparticle tracking analysis (NTA) were used to quantify the liposome sizes as described in our protocol, with commercial polystyrene (PS) beads used as a calibration standard. A near linear correlation was observed between the employed pore sizes and the experimentally determined liposomes, indicating high fidelity of our pressure-controlled liposome preparation method. Further, we have shown that this lipid vesicle preparation method is generally applicable, independent of various liposome sizes. Lastly, we have also demonstrated in a time course study that these prepared liposomes were stable for up to 16 hours. A representative nano-sized liposome preparation protocol is demonstrated below.

Fundamentals and applications of needle trap devices: A critical review

The needle trap device (NTD) is an extraction trap that contains a sorbent inside a small needle, through which fluid can be actively drawn into and out of by a gas-tight syringe or pump, or analytes can be introduced passively to the trap by diffusion. The needle trap (NT) is a potentially solventless sampling technique/sample preparation and introduction device. Both fluid-borne analytes and particles can be trapped inside the needle and then adsorbed analytes are desorbed in an inlet of analytical instrument and introduced for identification and quantification. The fluid may be either gaseous or liquid. The objectives of this critical review are to summarize the theory of the sampling process for both active and passive time-average extraction modes in addition to outlining the evolution of the technology and main applications.

Macro to nano: a simple method for transporting cultured cells from milliliter scale to nanoliter scale

Microfluidic devices are well-suited for the study of metabolism and paracrine and autocrine signaling because they allow steady or intermittent perfusion of biological cells at cell densities that approach those in living tissue. They also enable the study of small populations of rare cells. However, it can be difficult to introduce the cells into a microfluidic device to achieve and control such densities without damaging or clumping the cells. We describe simple procedures that address the problem of efficient introduction of cells and cell culture media into microfluidic devices using small bore polyetheretherketone (PEEK) tubing and Hamilton gastight syringes. Suspension or adherent cells grown in cell culture flasks are centrifuged and extracted directly from the centrifuge pellet into the end of the PEEK tubing by aspiration. The tube end is then coupled to prepunched channels in the polydimethylsiloxane microfluidic device by friction fitting. Controlled depression of the syringe plunger expels the cells into the microfluidic device only seconds following aspiration. The gastight syringes and PEEK tubing with PEEK fittings provide a non-compliant source of pressure and suction with a rapid response time that is well suited for short-term intramicrofluidic cellular studies. The benefits of this method are its simplicity, modest expense, the short preparation time required for loading appropriate numbers of cells and the applicability of the technique to small quantities of rare or expensive cells. This should in turn lead to new applications of microfluidic devices to biology and medicine.

Water Splitting by Visible Light: A Nanophotocathode for Hydrogen Production

Efficient production of solar fuels is an imperative for meeting future fossil-fuel-free energy demands. Hydrogen that is derived from the splitting of water by solar energy is clearly attractive as a clean energy vector, and there have been many attempts to construct viable molecular and biomolecular devices for photohydrogen production. A common approach in the construction of such devices is the utilization of tris(bipyridine)ruthenium, zinc porphyrin, or related molecular materials as photosensitizers in conjunction with a tethered or free electrocatalyst or enzymic system. Apart from cost, such systems suffer from having limited lifetimes, which may be attributed at least in part to the intrinsic reactivity of the organic N-donor ligands in the radical anion form of the photoexcited state and photodegradation pathways.