• Advances in nano research
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• v.2 no.2
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• pp.89-98
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• 2014

A novel and simple method for the synthesis of nano-magnetite particles is disclosed. In the novel procedure, $Fe^{2+}$ is the only source of metal cation. Carboxymethylcellulose (CMC) is used as the structure directing agent. The phase analysis of the nano-particles was performed using XRD and electron diffraction techniques. Size and morphology analysis was performed using light scattering and TEM techniques. The effect of $NH_4OH$ solution (32 wt. %) at different CMC concentrations on the size distribution of the final magnetite powders is studied. An optimal base concentration exists for each CMC concentration leading to minimal agglomeration. There exists a minimum CMC concentration (0.0016 wt. %), lower than that no magnetite forms. It is shown that using the new method, it is possible to immobilize a lipase enzyme (Candida Rugosa) with immobilization efficiency larger than 98 % with a loading more than 3 times the reported value in the literature. The latter phenomenon is explained based on the agglomerate state of the nano-particles in the liquid phase.

• Advances in materials Research
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• v.6 no.2
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• pp.129-153
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• 2017

Platinum is a transition metal that is very resistant to corrosion. It is used as catalyst for converting methyl alcohol to formaldehyde, as catalytic converter in cars, for hydrocracking of heavy oils, in Fuel Cell devices etc. Moreover, Platinum compounds are important ingredient for cancer chemotherapy drugs. The nano forms of Platinum due to its unique physico-chemical properties that are not found in its bulk counterpart, has been found to be of great importance in electronics, optoelectronics, enzyme immobilization etc. The stability of Platinum nanoparticles has supported its use for the development of efficient and durable proton exchange membrane Fuel Cells. The present review concentrates on the use of Platinum conjugated with various metal or compounds, to fabricate nanocomposites, to enhance the efficiency of Platinum nanoparticles. The recent advances in the synthesis methods of different Platinum-based nanocomposites and their applications in Fuel Cell, sensors, bioimaging, light emitting diode, dye sensitized solar cell, hydrogen generation and in biosystems has also been discussed.

• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.698-706
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• 2004

$\beta$-Lactam antibiotics such as penicillin G, amoxicillin, and ampicillin were determined by a potentiometric biosensor system which exploited penicillinase immobilized on Immobilon cellulose nitrate membrane and a flat-bottomed pH electrode-as the biological component and transducer. The optimum reaction buffer for maximum sensitivity was found as 2 mM of sodium phosphate buffer (pH 7.2). The detection limit of the biosensor could be extended to 1 $\mu{M}$ of the analytes by increasing the enzyme loading for immobilization to 100 units/$m\ell$. The model samples spiked with each of the standard penicillins were measured for their biosensor responses and HPLC peak area, resulting in the relative responses of 82.1-103.5% and 79.5-106.1% for the biosensor method along with HPLC analysis, respectively. This result showed a good precision of the current biosensor method for screening the penicillin compounds.

• Journal of the Korea Safety Management & Science
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• v.1 no.1
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• pp.259-272
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• 1999

In order to enhance the selectivity, productivity and yield of methyl fructoside, which was synthesized by enzymatic glycosylation of sucrose and methanol solution, controlling of surface property of solid support using different immobilization procedures optimized microenvironment of immobilized invertase. Silanization and polyethylene imine coating methods were adopted to give a hydrophobic and hydrophilic environment of immobilized invertase. As a result, polyethyleneimine coating method gave higher loading of enzyme, effective activity, and relative activity than silanization method, because it brought on increasing the functional density of amino group and enhancing the conservation of activity by regulating of hydrophilicity. And then, hydrophilic environment was possible to restraint the assessing of methyl fructoside molecule, which was more hydrophobic than sucrose, fructose, and glucose molecule in the reaction mixture, into .the active site of immobilizedinvertase. Consequently, hydrophilic microenvironment of immobilized invertase by polyethyleneimine coating obtained higher yield and productivity with increasing conversion than silanized and native invertase. Thus, this procedure optimized the microenvironment of immobilized invertase suitable for the enzymatic synthesis of methyl fructoside.

• Proceedings of the Membrane Society of Korea Conference
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• 2005.05a
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• pp.131-135
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• 2005

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1523-1528
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• 2006

The optimization of a batch-type quartz crystal microbalance (QCM)-precipitation sensor measuring acetylcholinesterase (AChE) activity was conducted. To covalently bind AChE onto the gold electrode of a QCM surface, glutaraldehyde cross-linking to a cystamine self-assembled monolayer was tried at different cystamine concentrations. At the optimum conditions of the QCM-precipitation sensor, 0.1 M potassium phosphate buffer (pH 8.0), containing 0.01% Tween 80, was used as the reaction buffer, with the enzyme amount of 5 units for immobilization and the substrate concentration of 50 mg/ml. The current biosensor might find a future applicability to the sum parameter detection on organophosphorus and carbamate pesticides.

• Bulletin of the Korean Chemical Society
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• v.20 no.6
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• pp.672-676
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• 1999

Gas-Permeable polymeric membranes containing carboxyl groups which are suitable for enzyme immobilization were investigated in order to use them as gas electrode membranes in biosensors. Carboxylated polyurethane (CPU) was synthesized via a reaciton between 2,2-bis(hydroxymethyl)propionic acid as a chain extender and prepolymers prepared from polycarprolactone(Mn=2,000) and 4,4'-diphenylmethane diisocynate. It was difficult to prepared membranes from the pure CPU because of its high elasticity and cohesion. However, transparent free-standing membranes were easily prepared from the blend solution of CPU and carboxylated poly(vinyl chloride)(CPVC) in tetrahydrofuran. Both elasticity and cohesion of the CPU/CPVC membranes were decreased with increasing the content of CPVC. DSC experiment suggests that CPU and CPVC may be well mixed. Permeability coefficients for O₂and CO₂(Po₂and Pco₂)in the membranes increased as the proportion of CPU increased. The addition of dioxtyl phthalate(DOP), a plasticizer, significantly enhanced the Po₂and Pco₂which were 4,4 and 30 barrer, respectively, in the CPU/CPVC(80/20 wt/wt) membranes containing 20% of DOP at 25℃ and 100psi. Thus this type of membranes may have a potential for the use as gas electrode membranes in biosensors.

• International Journal of Industrial Entomology and Biomaterials
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• v.44 no.2
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• pp.29-36
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• 2022

Over the past decades, silk sericin (SS) received increasing attention in the academic and industrial fields. In nature, SS acts as a glue that holds the two strands of silk fibrils together. However, recent works suggest that SS might have a more diverse role during the silk spinning process, such as stabilizing the SF in the silk gland. On the other hand, the sericulture industry has been trying to find novel applications for SS discarded from the silk fabric manufacturing process. Recovery and refining of SS would be the first step of the recycling of SS. Using a proper solvent SS could be shaped into various forms, such as spherical beads, microparticles, fibers, and films. Moreover, the applicability of these SS materials has been investigated in various fields such as cosmetics, templates for nanomaterials, drug delivery, heavy metal adsorption, and enzyme immobilization.

• Journal of the Korean Wood Science and Technology
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• v.30 no.3
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• pp.12-17
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• 2002

The extracellular invertase (EC 3.2.1.26) (Candida utilis) preparation was obtained from the liquid medium after desalting and freeze drying. This prepared enzyme was used for the comparative purification on 4 activated matrices by liquid column affinity chromatography method. In this method there were used controlled porous glass (CPG) silanized covalently activated by keratin, silanized silica gel and silica gel covalently covered by keratin. It was found that the invertase purification process was better using both CPG matrices (silanized CPG and keratin activated CPG) than these with two silica gel supports. Also the elution coefficient of the invertase from the two CPG columns was about 93 to 94%. Two silica gel supports found to be superior in terms of purification efficiency. The invertase purification process was confirmed by PAGE electrophoresis.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1193-1196
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• 2004

We have demonstrated the use of MWCNT as a nanoscale probe to monitor the activity of enzyme kinase. To immobilize the substrate peptide using carbodiimide chemistry, plasma or strong acid treatments were used to induce carboxyl groups on the sidewall of MWCNTs. After the susbtrate peptide immobilization, increase of conductance from MWCNT devices was observed. When peptide modified MWCNTs react with enzyme kinase, conductance decreases by several orders of magnitude, and this conductance change can be explained by the phosphorylation reaction of enzyme kinase. When the sample was incubated with phosphatase to dephosphorylate the substrate peptide, nearly complete recovery of the conductance signal has been observed. 4 for 6 devices appeared the same trends. So, we can confirm that we have monitored the kinase activity on the MWCNT surface by electrical detection.