Displaying publications 21 - 40 of 180 in total

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  1. An integrated lateral flow assay for effective DNA amplification and detection at the point of care
    Choi JR, Hu J, Gong Y, Feng S, Wan Abas WA, Pingguan-Murphy B, et al.
    Analyst, 2016 05 10;141(10):2930-9.
    PMID: 27010033 DOI: 10.1039/c5an02532j
    Lateral flow assays (LFAs) have been extensively explored in nucleic acid testing (NAT) for medical diagnostics, food safety analysis and environmental monitoring. However, the amount of target nucleic acid in a raw sample is usually too low to be directly detected by LFAs, necessitating the process of amplification. Even though cost-effective paper-based amplification techniques have been introduced, they have always been separately performed from LFAs, hence increasing the risk of reagent loss and cross-contaminations. To date, integrating paper-based nucleic acid amplification into colorimetric LFA in a simple, portable and cost-effective manner has not been introduced. Herein, we developed an integrated LFA with the aid of a specially designed handheld battery-powered system for effective amplification and detection of targets in resource-poor settings. Interestingly, using the integrated paper-based loop-mediated isothermal amplification (LAMP)-LFA, we successfully performed highly sensitive and specific target detection, achieving a detection limit of as low as 3 × 10(3) copies of target DNA, which is comparable to the conventional tube-based LAMP-LFA in an unintegrated format. The device may serve in conjunction with a simple paper-based sample preparation to create a fully integrated paper-based sample-to-answer diagnostic device for point-of-care testing (POCT) in the near future.
    Matched MeSH terms: Biological Assay
  2. Development of resazurin-based assay in 384-well format for high throughput whole cell screening of Trypanosoma brucei rhodesiense strain STIB 900 for the identification of potential anti-trypanosomal agents
    Lim KT, Zahari Z, Amanah A, Zainuddin Z, Adenan MI
    Exp Parasitol, 2016 Mar;162:49-56.
    PMID: 26772786 DOI: 10.1016/j.exppara.2016.01.002
    To accelerate the discovery of novel leads for the treatment of Human African Trypanosomiasis (HAT), it is necessary to have a simple, robust and cost-effective assay to identify positive hits by high throughput whole cell screening. Most of the fluorescence assay was made in black plate however in this study the HTS assay developed in 384-well format using clear plate and black plate, for comparison. The HTS assay developed is simple, sensitive, reliable and reproducible in both types of plates. Assay robustness and reproducibility were determined under the optimized conditions in 384-well plate was well tolerated in the HTS assay, including percentage of coefficient of variation (% CV) of 4.68% and 4.74% in clear and black 384-well plate, signal-to-background ratio (S/B) of 12.75 in clear 384-well plate and 12.07 in black 384-well plate, Z' factor of 0.79 and 0.82 in clear 384-well plate and black 384-well plate, respectively and final concentration of 0.30% dimethylsulfoxide (DMSO) in both types of plate. Drug sensitivity was found to be comparable to the reported anti-trypanosomal assay in 96-well format. The reproducibility and sensitivity of this assay make it compliant to automated liquid handler use in HTS applications.
    Matched MeSH terms: Biological Assay
  3. Toxicity study of the oil dispersant Corexit 9527 on Macrobrachium rosenbergii (de Man) egg hatchability by using a flow-through bioassay technique
    Law AT
    Environ Pollut, 1995;88(3):341-3.
    PMID: 15091547
    The effect of the oil-spill dispersant Corexit 9527 on egg-hatching rate of Macrobrachium rosenbergii (de Man) was studied by using an innovated flow-through bioassay technique. This bioassay method relies on the fact that M. rosenbergii fertilized eggs when detached from the mother prawn were able to hatch artificially. The flow-through system generated a stable and good water quality environment for hatching the eggs successfully. The Corexit 9527 had a pronounced effect on hatching rate of the M. rosenbergii eggs. In the control, the hatching rate of the eggs was 95.55% +/- 1.74%. However, it was reduced drastically with increasing concentrations of Corexit 9527. A 100% inhibition of egg hatchability was found when the level of Corexit 9527 was higher than 250 mg litre(-1). The EC(50) and the EC(95) values estimated by the probit method were 80.4 +/- 5.5 mg litre(-1) and 193.5 +/- 39.9 mg litre(-1) respectively (P = 0.05). The recommended safety level of Corexit 9527 for M. rosenbergii in Malaysian estuarine waters is below 40 mg litre(-1).
    Matched MeSH terms: Biological Assay
  4. Fulltext Production of chitosan oligosaccharides using β-glycosidic degrading enzyme: optimization using response surface methodology
    Yusof Nurhayati, Abdul Manaf Ali
    Malaysian Journal of Applied Sciences, 2020;5(2):30-44.
    MyJurnal
    Many researchers have focused chitosan as a source of potential bioactive material during the past few decades. However, chitosan has several drawbacks to be utilised in biological applications, including poor solubility under physiological conditions. Therefore, a new interest has recently emerged on partially hydrolysed chitosan, chitosan oligosaccharides (COS). In this study, degradation of chitosan was performed by Cellulase from Trichoderma reesei® 1.5L and Response Surface Methodology (RSM) were employed to optimize the hydrolysis temperature, pH, enzyme concentration and substrate concentration. Optimization of cellulase T. reesei® using central composite design (CCD) was to obtain optimum parameters and all the factors showed significant effects (p˂0.05). The maximum response, Celluclast® activity (1.268 U) was obtained by assaying the process at 49.79oC, pH 4.5, 3% (v/w) of enzyme concentration and 25% (w/v) concentration of chitosan for 24 hours.
    Matched MeSH terms: Biological Assay
  5. Fulltext Effect of residual toxicity of selected insecticides to the Malaysian stingless bee Heterotrigona Itama
    Noor Albannia Natasya Jabi, Hazmi Awang Damit
    Borneo Akademika, 2019;3(1):1-9.
    MyJurnal
    Heterotrigona itama is a Malaysian stingless bee species that actively reared for meliponiculture. This stingless bee is cultivated in a commercial scale for its honey production, propolis and among the greatest commercial potential as crop pollinators. However, this species has been potentially exposed to agronomic practices, among which the use of synthetic insecticides against pests.The indirect toxicity effect of the post-insecticide had affected the mortalities of H. itama especially, to the foragers. Due to that, a study has been conducted to determine the lethal concentration of 50% (LC50) and 95% (LC95) of the selected insecticides against stingless bee forager workers through residual exposure. The bioassay test was conducted to the local stingless bee H. itama at Agricultural Research Station, Tenom. Four commonly used insecticides in crop protection; Deltamethrin, Chlorpyrifos, Cypermethrin and Malathion were tested at five concentrations that diluted with 500 ml of distilled water in three replications for each insecticide. Lethal concentrations (LC50 and LC95) were obtained from probit analysis after 1-hour dry residues exposure and 24-hour mortality observation. The result shows that; all four tested insecticides were harmful to H. itama through dry residue. Deltamethrin shows the higher value of LC50 (1.256 ml) and LC95 (3.582ml) that make it less toxic to the H. itama than cypermethrin, malathion, and chlorpyrifos, however, as the concentration gets higher it becomes more toxic.
    Matched MeSH terms: Biological Assay
  6. Potent allelopathy and non-PSTs, non-spirolides toxicity of the dinoflagellate Alexandrium leei to phytoplankton, finfish and zooplankton observed from laboratory bioassays
    Shang L, Xu Y, Leaw CP, Lim PT, Wang J, Chen J, et al.
    Sci Total Environ, 2021 Aug 01;780:146484.
    PMID: 33774286 DOI: 10.1016/j.scitotenv.2021.146484
    The dinoflagellate genus Alexandrium has been well known for causing paralytic shellfish poisoning (PSP) worldwide. Several non-PSP toxin-producing species, however, have shown to exhibit fish-killing toxicity. Here, we report the allelopathic activity of Alexandrium leei from Malaysia to other algal species, and its toxicity to finfish and zooplankton, via laboratory bioassays. Thirteen microalgal species that co-cultured with Al. leei revealed large variability in the allelopathic effects of Al. leei on the test algae, with the growth inhibition rates ranging from 0 to 100%. The negative allelopathic effects of Al. leei on microalgae included loss of flagella and thus the motility, damages of chain structure, deformation in cell morphology, and eventually cell lysis. The finfish experienced 100% mortality within 24 h exposed to the live culture (2000-6710 cells·mL-1), while the rotifer and brine shrimp exhibited 96-100% and 90-100% mortalities within 48 h when exposed to 500-6000 cells·mL-1 of Al. leei. The mortality of the test animals depended on the Al. leei cell density exposed, leading to a linear relationship between mortality and cell density for the finfish, and a logarithmic relationship for the two zooplankters. When exposed to the treatments using Al. leei whole live culture, cell-free culture medium, extract of algal cells in the f/2-Si medium, extract of methanol, and the re-suspended freeze-and-thaw algal cells, the test organisms (Ak. sanguinea and rotifers) all died at the cell density of 8100 cells·mL-1 within 24 h. Toxin analyses by HILIC-ESI-TOF/MS and LC-ESI-MS/MS demonstrated that Al. leei did not produce PSP-toxins and 13-desmethyl spirolide C. Overall, our findings demonstrated potent allelopathy and toxicity of Al. leei, which do not only pose threats to the aquaculture industry, fisheries, and marine ecosystems but may also play a part role in the population dynamics and bloom formation of this species.
    Matched MeSH terms: Biological Assay
  7. Fulltext Rapid spheroid assays in a 3-dimensional cell culture chip
    Teh JL, Abdul Rahman SF, Domnic G, Satiyasilan L, Chear NJY, Singh D, et al.
    BMC Res Notes, 2021 Aug 13;14(1):310.
    PMID: 34389056 DOI: 10.1186/s13104-021-05727-0
    OBJECTIVE: The spheroid model provides a physiological platform to study cancer cell biology and drug sensitivity. Usage of bovine collagen I for spheroid assays is costly especially when experiments are conducted in 24-well plates, as high volume of bovine collagen I is needed. The aim of the study was to downsize spheroid assays to a microfluidic 3D cell culture chip and compare the growth, invasion and response to drug/compound of spheroids embedded in the 3D chip to spheroids embedded in 24-well plates.

    RESULTS: Spheroids generated from nasopharyngeal carcinoma cell line HK-1 continuously grew and invaded into collagen matrix in a 24-well plate. Similar observations were noticed with spheroids embedded in the 3D chip. Large spheroids in both 24-well plate and the 3D chip disintegrated and invaded into the collagen matrix. Preliminary drug sensitivity assays showed that the growth and invasion of spheroids were inhibited when spheroids were treated with combination of cisplatin and paynantheine at high concentrations, in a 24-well plate. Comparable findings were obtained when spheroids were treated with the same drug combination in the 3D chip. Moving forward, spheroid assays could be performed in the 3D chip in a more high-throughput manner with minimal time and cost.

    Matched MeSH terms: Biological Assay
  8. Fulltext Laboratory bioefficacy of CREEK 1.0G (temephos) against Aedes (Stegomyia) aegypti (Linnaeus) larvae
    Chen CD, Lee HL
    Trop Biomed, 2006 Dec;23(2):220-3.
    PMID: 17322825 MyJurnal
    The bioefficacy of a commercial formulation of temephos, Creek against Aedes aegypti larvae was studied in the laboratory. Earthen jars were filled with 10 L tap water each. One g of temephos (Creek) sand granule formulation was added into each earthen jar as recommended by the manufacturer. The final test concentration of Creek was 1 mg a.i./L. One earthen jar was filled with 10 L tap water and served as a test control (untreated). Thirty late 3(rd) or early 4(th) instar of lab-bred Ae. aegypti larvae were added into each earthen jar. Mortality of the larvae was recorded after 24 hours and percent mortality was calculated. Test was repeated every week. The results showed that complete larval mortality was achieved after 24 hours. The residual effect lasted 15 weeks (105 days), indicating that Creek is effective at the dosage recommended by the manufacturer which is 1 mg a.i./L.
    Matched MeSH terms: Biological Assay
  9. Protein quality of selected edible animal and plant protein sources using rat bio-assay
    Babji, A.S., Fatimah, S., Abolhassani, Y.
    International Food Research Journal, 2010;17(2):303-308.
    MyJurnal
    Protein efficiency ratio (PER) and protein digestibility are important parameters used in protein quality determination. Protein nutritive values of selected protein sources: buffalo meat, casein, soy protein isolate, and tempeh, with sodium caseinate as a reference formulation, were evaluated. Determination of proximate analysis, protein quality and protein digestibility were monitored. Procedures for evaluation of protein quality and digestibility included PER using the rat bioassay and in vivo Apparent Protein Digestibility (APD). The rats fed with buffalo meat had the highest mean increase in body weight (102.73g±8.95) while rats fed with tempeh had the lowest mean for increase in body weight (16.34g±9.11). Although the mean for body weight gained showed significant differences between all treatments (P0.05) found between casein and soy protein isolate for total food intake. For the PER value, buffalo meat had the highest value (2.99), followed by sodium caseinate (2.41), casein (1.93), soy protein isolate (1.52) and tempeh (1.10). The PER value for buffalo meat (2.99) was higher than sodium caseinate (2.41) while the rest of the treatment were comparatively lower than sodium caseinate. For the in vivo apparent protein digestibility, tempeh had the highest value (91.41%±3.76), followed by casein (91.34%±3.15), buffalo meat (90.79%±1.44), soy protein isolate (89.52%±2.96) and sodium caseinate (89.47%±2.31).
    Matched MeSH terms: Biological Assay
  10. Fulltext Medicinal plant research in Malaysia: scientific interests and advances
    Ibrahim Jantan
    Jurnal Sains Kesihatan Malaysia, 2004;2(2):27-46.
    MyJurnal
    This paper outlines the past five decades of scientific interests and advances in medicinal plant research in Malaysia. Initially the prime interest of research programmes has been on phytochemical studies leading to the discovery of biologically active compounds as chemical templates to produce new drug candidates. As the Malaysian herbal medicine market experiences an extraordinary growth, the research approaches taken have recently included activities to develop herbal medicines into quality, efficacious and safe products for human consumption. Advances in chromatographic and spectroscopic techniques have had a tremendous impact on the isolation and structure elucidation of the constituents of medicinal plants. The development of a series of bioassay methodologies and utilization of bioassay-guided isolation techniques have contributed significantly to the progress of medicinal plant research in Malaysia. Research work on some medicinal plants carried out by the local scientists will be illustrated as examples.
    Matched MeSH terms: Biological Assay
  11. Fulltext Detection of tetrodotoxin and saxitoxin in dried salted yellow puffer fish (Xenopterus naritus) eggs from Satok Market, Kuching, Sarawak
    Mohd Nor Azman, A., Wan Norhana, M.N.
    International Food Research Journal, 2013;20(5):2963-2966.
    MyJurnal
    The detection of tetrodotoxin (TTX) and saxitoxin (STX) in dried salted yellow puffer fish (Xenopterus naritus) eggs bought from Satok Market, Kuching, Sarawak was carried out by mouse bioassay method. The amount of TTX and STX detected in the samples ranged from 95.6-195.5 Mouse Unit (MU)/g and 1.72-3.58 MU/g respectively. The results indicate that the dried salted eggs samples were found to contain TTX 9-20 times above the regulatory limit for human consumption (10 MU/g). Although detected, the amount of STX in salted eggs extract was slightly below the accepted threshold limit (4 MU/g). The local public in Sarawak should be educated on the potential danger of consuming dried salted puffer fish eggs in addition to the current warnings on puffer fish.
    Matched MeSH terms: Biological Assay
  12. Fulltext Rapid ecotoxicological tests using bioassay systems - a review
    Halmi, M.I.E.
    Journal of Biochemistry, Microbiology and Biotechnology, 2016;4(1):29-37.
    MyJurnal
    The rise in pollution cases globally is expected to increase in line with industrialization.
    Monitoring activities for pollutants have been hampered by the astronomical costs of
    instrumental-based approach. This has resulted in the intense research on low cost
    biomonitoring systems using enzymes, organisms including microorganisms. Only positive
    samples are sent for instrumental analysis; dramatically cutting the cost of instrumental
    analysis. This review attempts to outline and give due recognition to several selected bioassay
    systems that have been tested for their applicability using polluted water samples as a routine
    first line-of-defense. This includes small aquatic organisms-based assays, enzymes especially
    proteases and bacterial-based systems using respiratory dye or luminescence systems as a
    method for toxicant detection.
    Matched MeSH terms: Biological Assay
  13. Fulltext Near real-time biomonitoring of copper from an industrial complex effluent discharge site using a plant protease inhibitive assay
    Halmi, M.I.E., Khayat, M.E., Rahman, M.F.A., Gunasekaran, B., Masdor, N.A.
    Bioremediation Science and Technology Research, 2016;4(1):10-13.
    MyJurnal
    In this work, a temporal monitoring work for heavy metals from an effluent discharge point in
    the Juru Industrial Estate was carried out using the protease extracted from garlic (Allium
    sativum) as the principal bioassay system. casein-Coomassie-dye binding assay method has
    utilized this purpose. The periodic sampling results for one day of a location in the Juru
    Industrial Estate showed temporal variation of copper concentration coinciding with garlic
    protease inhibition with the highest concentrations of copper occurring between 12.00 and 16.00
    hours of between 3 and 3.5 mg/L copper. The crude proteases extracted from Allium sativum
    successfully detect temporal variation of copper form this location. In conclusion, this assay
    method has the potential to be a rapid, sensitive, and economic inhibitive assay for the largescale
    biomonitoring works for the heavy metal copper from this area.
    Matched MeSH terms: Biological Assay
  14. Fulltext Assay for heavy metals using an inhibitive assay based on the acetylcholinesterase from Channa striatus
    Zulkifli, A.F., Tham, L.G., Perumal, N., Azzeme, A., Shukor, M.Y., Shaharuddin, N.A., et al.
    Bioremediation Science and Technology Research, 2017;5(1):7-11.
    MyJurnal
    Acetylcholinesterase (AChE) is usually used as an inhibitive assay for insecticides. A lesser
    known property of AChE is its inhibition by heavy metals. In this work we evaluate an AChE
    from brains of striped snakehead (Channa striatus) wastes from aquaculture industry as an
    inhibitive assay for heavy metals. We discovered that the AChE was inhibited almost completely
    by Hg2+, Ag2+ and Cu2+ during an initial screening. When tested at various concentrations, the
    heavy metals exhibited exponential decay type inhibition curves. The calculated IC50 for the
    heavy metals Hg2+, Ag2+, Pb2+, Cu2+ and Cr6+ were 0.08432, 0.1008, 0.1255, 0.0871, and 0.1771,
    respectively. The IC50 for these heavy metals are comparable and some are lower than the IC50
    values from the cholinesterases from previously studied fish. The assay can be carried out in less
    than 30 minutes at ambient temperature.
    Matched MeSH terms: Biological Assay
  15. Fulltext Assay for heavy metals using an inhibitive assay based on the acetylcholinesterase from Clarias batrachus
    Abubakar M. Umar, Tham, Lik Gin, Natarajan Perumal, Nur Adeela Yasid, Hassan Mohd Daud, Mohd Yunus Shukor
    Bioremediation Science and Technology Research, 2016;4(2):6-10.
    MyJurnal
    Acetylcholinesterase (AChE) is usually used as an inhibitive assay for insecticides. A lesserknown
    property of AChE is its inhibition by heavy metals. In this work, we evaluate an AChE
    from brains of Clarias batrachus (catfish) exposed to wastes from aquaculture industry as an
    inhibitive assay for heavy metals. We discovered that the AChE was inhibited completely by
    Hg2+, Ag2+, Pb2+, Cu2+, Cd2+, Cr6+ and Zn2+ during initial screening. When tested at various
    concentrations, the heavy metals exhibited exponential decay type inhibition curves. The
    calculated IC50 (mg/L) for the heavy metals Ag2+, Cu2+, Hg2+, Cr6+ and Cd2+ were 0.088, 0.078,
    0.071, 0.87 and 0.913, respectively. The IC50 for these heavy metals are comparable, and some
    are lower than the IC50 values from the cholinesterases from previously studied fish. The assay
    can be carried out in less than 30 minutes at ambient temperature.
    Matched MeSH terms: Biological Assay
  16. Allelopathic potential of the leaf and seed of Pueraria javanica benth. on the germination and growth of three selected weed species
    Ismail B, Syamimi Halimshah, Wan Juliana W, Nornasuha Yusof
    Sains Malaysiana, 2016;45:517-521.
    Pueraria javanica Benth. is one of the most common leguminous cover crop used in oil palm plantations of Malaysia. A study was conducted to determine the allelopathic potential of this plant, using the aqueous extract, sandwich and dish-pack methods, with the seed and leaf (of P. javanica) on three bioassay weed species namely, Eleusine indica, Cyperus iria and Chromolaena odorata. The aqueous extract experiment was conducted using 0 (control), 16.7, 33.3 and 66.7 g/L of the aqueous leaf and seed extracts while the sandwich method was carried out using 10 and 50 mg of each of the donour plant parts. Meanwhile, the dish-pack method was done using four different distances (41, 58, 82 and 92 mm) away from the donour plant. All experiments were replicated five times using the complete randomized design (CRD). The leaf extract exhibited 100% reduction on the fresh weight of E. indica and C. odorata while the seed extract exhibited 100% reduction on all parameters for E. indica and on the fresh weight of C. iria at 66.7 g/L concentration. The seed and leaf at 10 and 50 mg significantly reduced the radicle length of all the bioassay species. The dish-pack experiment also showed a reduction effect on the germination percentage and seedling growth parameters of all the bioassay species. However, the reduction effect was not totally in accordance to the distance from the donor species. More studies need to be conducted to determine the type of reduction mechanism involved in the allelopathic activity especially with respect to molecular and biochemical aspects.
    Matched MeSH terms: Biological Assay
  17. Assessment of the potential allelopathic effects of pennisetum purpureum schumach. on the germination and growth of eleusine indica (l.) gaertn.
    Ismail B, Chuah T, Tan P
    Sains Malaysiana, 2015;44:269-274.
    Pennisetum purpureum Schumach. is a weed that is currently spreading rapidly to many parts of the world particularly tropical countries. The abundance of P. purpureum in Malaysia is presently a serious problem. A study was conducted to investigate and evaluate the potential allelopathic effects of P. purpureum on Eleusine indica L. Gaertn. using the aqueous leaf extract and plant debris incorporated into the soil. Low concentrations of the P. purpureum aqueous extract (2%) and debris incorporated into the soil (25/500 g) inhibited germination and seedling growth of the bioassay species (E. indica) by >80%. The responses of the bioassay species to the aqueous extract and debris-incorporated soil were concentration dependent. The aqueous extract had higher total phenolic content compared to that from the debris incorporated soil, indicating the presence of certain phytotoxic compounds in the leaf debris and leaf extracts.
    Matched MeSH terms: Biological Assay
  18. Elastic reversible valves on centrifugal microfluidic platforms
    Aeinehvand MM, Weber L, Jiménez M, Palermo A, Bauer M, Loeffler FF, et al.
    Lab Chip, 2019 Feb 20.
    PMID: 30785443 DOI: 10.1039/c8lc00849c
    Reversible valves on centrifugal microfluidic platforms facilitate the automation of bioanalytical assays, especially of those requiring a series of steps (such as incubation) in a single reaction chamber. In this study, we present fixed elastic reversible (FER) valves and tunable elastic reversible (TER) valves that are easy to fabricate, implement and control. In the FER valve the compression of an elastic barrier/patch against a microchamber's outlet prevents the release of liquid. The valve sealing pressure was determined by adjusting the engraving depth of the valve-seat at which the elastic patch was located, this allows to set the sealing pressure during disc fabrication. In the TER valve, the patch compression value and sealing pressure is controlled by the penetration depth of a plastic screw into the valve-seat. The ER valves prevent liquid flow until the centrifugal force overcomes their sealing pressure. Moreover, at a constant spin speed, turning the screw of a TER valve reduces its sealing pressure and opens the valve. Therefore, the TER valve allows for controlling of the liquid transfer volume at various spin speeds. The FER and TER valves' behavior is mathematically described and equations for the prediction of their operation under centrifugal forces are provided. As a point-of-care (POC) application of ER valves, we have developed a microfluidic disc with a series of TER valves and peptide microarrays for automated multiplexed detection of five different proteins from a single serum sample.
    Matched MeSH terms: Biological Assay
  19. Biological and physical characterization of bacteriophage JHA against multidrug-resistant Acinetobacter baumannii
    Ajmal H, Sharif Z, Zeshan B, Zahra N, Khan M
    Pak J Pharm Sci, 2022 Sep;35(5):1327-1331.
    PMID: 36451560
    Due to the emergence of antibiotic resistance, bacteriophage therapy appears to be an ideal weapon to utilize against pathogenic bacteria. This study aimed to isolate, identify and characterize the lytic bacteriophage effective against the multidrug-resistant Acinetobacter baumannii clinical isolates. The isolated bacteriophage caused lysis by applying the double-layer agar technique on A. baumannii up to 99% in 18 hours of incubation at 37ºC. The bacterial growth reduction assay exhibited that JHA phage had high adsorption rates and could rapidly inhibit bacterial growth. The pH and thermal stability testing showed that JHA phage was stable in vast ranges of pH from 5 to 9 but its activity was highest at pH7 (1860000±1000 pfu/mL). It was stable in broad ranges of temperatures from 25ºC to 60ºC but the highest activity was found at 37ºC (1300000±30000 pfu/mL). One-step growth test results showed that it has a short latent period, strong lytic ability, high burst size and adsorption rates and was host specific. Scanning electron microscopy (SEM) of JHA phage demonstrated icosahedral heads and tailless particles. Transmission electron microscopy (TEM) revealed JHA phage belongs to Tectiviridae family. All the characteristics of JHA phage possess lytic activity against A. baumannii strains and exhibit novel candidates to use as an alternative competitor to antibiotics in controlling such infections.
    Matched MeSH terms: Biological Assay
  20. Fulltext Development of a passive liquid valve (PLV) utilizing a pressure equilibrium phenomenon on the centrifugal microfluidic platform
    Al-Faqheri W, Ibrahim F, Thio TH, Bahari N, Arof H, Rothan HA, et al.
    Sensors (Basel), 2015 Feb 25;15(3):4658-76.
    PMID: 25723143 DOI: 10.3390/s150304658
    In this paper, we propose an easy-to-implement passive liquid valve (PLV) for the microfluidic compact-disc (CD). This valve can be implemented by introducing venting chambers to control the air flow of the source and destination chambers. The PLV mechanism is based on equalizing the main forces acting on the microfluidic CD (i.e., the centrifugal and capillary forces) to control the burst frequency of the source chamber liquid. For a better understanding of the physics behind the proposed PLV, an analytical model is described. Moreover, three parameters that control the effectiveness of the proposed valve, i.e., the liquid height, liquid density, and venting chamber position with respect to the CD center, are tested experimentally. To demonstrate the ability of the proposed PLV valve, microfluidic liquid switching and liquid metering are performed. In addition, a Bradford assay is performed to measure the protein concentration and evaluated in comparison to the benchtop procedure. The result shows that the proposed valve can be implemented in any microfluidic process that requires simplicity and accuracy. Moreover, the developed valve increases the flexibility of the centrifugal CD platform for passive control of the liquid flow without the need for an external force or trigger.
    Matched MeSH terms: Biological Assay
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