• Journal of Microbiology and Biotechnology
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• 제24권10호
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• pp.1354-1367
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• 2014

In the present work, we describe a simple, cheap, and unexplored method for "green" synthesis of silver nanoparticles using cell extracts of the cyanobacterium Anabaena doliolum. An attempt was also made to test the antimicrobial and antitumor activities of the synthesized nanoparticles. Analytical techniques, namely UV-vis spectroscopy, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and TEM-selected area electron diffraction, were used to elucidate the formation and characterization of silver-cyanobacterial nanoparticles (Ag-CNPs). Results showed that the original color of the cell extract changed from reddish blue to dark brown after addition of silver nitrate solution (1 mM) within 1 h, suggesting the synthesis of Ag-CNPs. That the formation Ag-CNPs indeed occurred was also evident from the spectroscopic analysis of the reaction mixture, wherein a prominent peak at 420 nm was noted. TEM images revealed well-dispersed, spherical Ag-CNPs with a particle size in the range of 10-50 nm. The X-ray diffraction spectrum suggested a crystalline nature of the Ag-CNPs. FTIR analysis indicated the utilization of a hydroxyl (-OH) group in the formation of Ag-CNPs. Ag-CNPs exhibited strong antibacterial activity against three multidrug-resistant bacteria. Additionally, Ag-CNPs strongly affected the survival of Dalton's lymphoma and human carcinoma colo205 cells at a very low concentration. The Ag-CNPs-induced loss of survival of both cell types may be due to the induction of reactive oxygen species generation and DNA fragmentation, resulting in apoptosis. Properties exhibited by the Ag-CNP suggest that it may be used as a potential antibacterial and antitumor agent.

• 한국통신학회논문지
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• 제31권1C호
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• pp.36-45
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• 2006

본 논문에서는 효과적인 3차원 영상 디스플레이를 위한 다시점 영상왜곡 보정처리 시스템 구현을 제안한다. 본 논문에서 제안한 보정처리 시스템은 기존의 스테레오 방식에서 확장된 4시점으로 카메라를 구성하여 영상을 획득하고 다시점 영상 간에 발생할 수 있는 렌즈의 왜곡, 카메라 오차 및 크기, 카메라 간 밝기 및 색상, 영상 간 밝기 균일도 등의 영상의 보정 신호처리에 대한 방법을 제시한다. 본 논문에서 제안된 시스템에서는 카메라 간 밝기 및 색상 보상은 각 영상의 특징점과 대응점을 찾아 영상 전체에 대한 대응점을 추출하여 색 변환을 통해 영상을 보정하였고 밝기 및 균일도 처리는 각 영상의 밝기차이 맵을 생성하여 보상하였다. 또한 렌즈의 구면수차로 인한 왜곡은 각 영상의 패턴을 검출한 후 렌즈 왜곡을 보정하고 카메라의 오차 및 크기 보상을 통해 다시점 3차원 디스플레이시 발생되는 왜곡현상을 해결하여 보다 효과적인 3차원 입체 디스플레이가 가능하도록 하였다.

• 한국세라믹학회지
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• 제30권6호
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• pp.433-440
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• 1993

The bioactivity of glasses in the CaO-SiO2 system and CaO-P2O5-SiO2 system with less than 10mol% of P2O5 was investigated by in vitro test in simulated body flood(SBF). The formation of Ca.P film and hydroxyapatite on the surface of glasses after in vitro test was analysed by X-ray photoelectron spectoscopy (XPS), fourier transform infrared reflection spectroscopy (FT-IRRS), energy dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) observation. In the early stage of Ca.P film formation after in vitro test for CaO-SiO2 and CaO-P2O5-SiO2 glasses, the rate of Ca.P film formation on the surface of the glasses was dependent of structural parameter (Y) evaluated from the glass composition. First, in the case of the glasses having Y value below 2, Ca.P film and SiO2-rich layer were formed simultaneously, and there were no differences of the rate of Ca.P film formation in terms of the Y values. Second, in the case of the glasses having Y value above 2, the SiO2-rich layer was formed, and then Ca.P.Si mixed layer was formed in the silica gel structure of the SiO2-rich layer, and finally the Ca.P film on the surface of SiO2-rich layer. The rate of Ca.P film formation delayed as the Y values increased. The rate of hydroxyapatite formation of glasses (the rate of transformation from Ca.P film to hydroxyapatite) seems to be propotional to the rate of Ca.P film formation and Y value. The rate of hydroxyapatite formation of glasses belonging to the second group was delayed as structural parameter increased, and the hydroxyapatite crystal showed spherical growth in the early reaction stage, and then showed silkworm-like linear growth as the reaction time increased.

• 한국세라믹학회지
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• 제54권1호
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• pp.49-54
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• 2017

In this study, based on hydrolysis and condensation via $St{\ddot{o}}ber$ process of sol-gel method, synthesis of mono-dispersed silica nanoparticles was carried out with hydrophilic solvent. This operation was expected to be a more simplified process than that with organic solvent. Based on the sol-gel method, which involves simply controlling the particle size, the particle size of the synthesized silica specimens were ranged from 30 to 300 nm by controlling the composition of tetraethylorthosilicate (TEOS), DI water and ammonia solution, and by varying the stirring speeds while maintaining a fixed amount of ethanol. Increasing the content of DI water and decreasing the content of ammonia caused the particle size to decrease, while controlling the stirring speed at a high level of RPMs enabled a decrease of the particle size. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were utilized to investigate the success factors for synthesizing process; Field emission scanning electron microscopy (FE-SEM) was used to study the effects of the size and morphology of the synthesized particles. To analyze the dispersion properties, zeta potential and particle size distribution (PSD) analyses were utilized.

• 한국결정성장학회지
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• 제12권3호
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• pp.126-132
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• 2002

$ZrOCl_2{\cdot}8H_2O$ 수용액과 KOH 수용액의 반응으로부터 얻은 침전물을 $100^{\circ}C$에서 24 시간 동안 숙성시켜 정방정상 지르코니아를 제조한 후 수열합성 조건을 변화시킴으로써 비등방성 형상의 나노 결정형 지르코니아 분말을 합성하였다. 수열합성 시 반응온도와 반응시간이 증가할수록 정방정상인 구형 입자는 감소하고 상대적으로 단사정상 spindle-like 입자와 막대상 입자가 증가하였다. NaOH 용액의 농도가 증가함에 따라 입성장과 함께 정방정상에서 단사정상으로의 상전이가 촉진되었으며, 저온에서 반응시간이 짧은 경우 합성한 분말들은 반응초기에 응집된 입자들이 NaOH 용액에 부분적으로 용해되면서 응집입자 및 결정입자 크기가 감소되어 비표면적이 증가하였다가 반응시간이 길어지고 반응온도가 높아짐에 따라 입성장에 의하여 점차 비표면적이 감소하였다.

• 한국응용과학기술학회지
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• 제29권1호
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• pp.95-101
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• 2012

완전 생분해성 고분자 블렌드필름을 제조하기 위하여 치환도가 다른 두 셀룰로오스 아세테이트(CA)에 5 - 50%의 저분자량 폴리락타이드(PLA)를 블렌딩하였다. 이 때 사용된 각각의 고분자는 10% 메탄올/메틸렌클로라이드 혼합용제에 녹여서 점도가 같은 조건의 농도로 제조하였다. 각 조성의 블렌드필름의 표면 모폴로지와 열적 성질, 기계적 성질을 조사하였다. 화학적 구조는 적외선 분광법으로 확인하였으며, 전자현미경을 통한 표면 분석 결과 5% 이하의 폴리락타이드를 함유한 블렌드필름은 상분리가 거의 일어나지 않았으며 20% 이상이 함유된 경우 상분리가 매우 심각하였다. 또한 블렌드필름의 인장강도는 셀룰로오스 아세테이트의 함량이 늘어날수록 TAC/PLA의 경우 $820kg_f/cm^2$ 및 DAC/PLA의 경우 $600kg_f/cm^2$까지 향상시킬 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제28권6호
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• pp.917-930
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• 2018

Intracellular synthesis of silver/silver chloride nanoparticles (Ag/AgCl-NPs) using Meyerozyma guilliermondii KX008616 is reported under aerobic and anaerobic conditions for the first time. The biogenic synthesis of Ag-NP types has been proposed as an easy and cost-effective alternative for various biomedical applications. The interaction of nanoparticles with ethanol production was mentioned. The purified biogenic Ag/AgCl-nanoparticles were characterized by different spectroscopic and microscopic approaches. The purified nanoparticles exhibited a surface plasmon resonance band at 419 and 415 nm, confirming the formation of Ag/AgCl-NPs under aerobic and anaerobic conditions, respectively. The planes of the cubic crystalline phase of the Ag/AgCl-NPs were confirmed by X-ray diffraction. Fourier-transform infrared spectra showed the interactions between the yeast cell constituents and silver ions to form the biogenic Ag/AgCl-NPs. The intracellular Ag/AgCl-NPs synthesized under aerobic condition were homogenous and spherical in shape, with an approximate particle size of 2.5-30nm as denoted by the transmission electron microscopy (TEM). The reaction mixture was optimized by varying reaction parameters, including temperature and pH. Analysis of ultrathin sections of yeast cells by TEM indicated that the biogenic nanoparticles were formed as clusters, known as nanoaggregates, in the cytoplasm or in the inner and outer regions of the cell wall. The study recommends using the biomass of yeast that is used in industrial or fermentation purposes to produce Ag/AgCl-NPs as associated by-products to maximize benefit and to reduce the production cost.

• Journal of Pharmaceutical Investigation
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• 제38권2호
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• pp.119-126
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• 2008

Solid dispersions of poorly water-soluble drug, sibutramine, were prepared with hydrophilic polymer, poly-N-vinylpyrrolidone (PVP), hydroxypropylmethylcellulose (HPMC) and organic acid, citric acid, to improve the solubility of drug. Physicochemical variation and shape of microsphere were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and Fourier-transform infrared spectroscopy (FT-IR). Microspheres containing additives showed more spherical shape than non additive microspheres. In vitro release behavior of microspheres presented at simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 6.8). The solid dispersion form transformed the drug into an amorphous state and dramatically improved its dissolution rate. These data suggest that the solid dispersion technique is an effective approach for developing the appetite depressant drug products and various pharmaceutical excipients are able to control the release behaviors.

• Korean Chemical Engineering Research
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• 제59권4호
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• pp.493-502
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• 2021

We prepared and investigated a biosynthesized nanoparticulate system with high adsorption and release capacity of letrozole. Silver nanoparticles (AgNPs) were biosynthesized using olive leaf extract. Cysteine was capped AgNPs to increase the adsorption capacity and suitable interaction between nanoparticles and drug. Morphology and size of nanoparticles were confirmed using transmission electron microscopy (TEM). Nanoparticles were spherical with an average diameter of less than 100 nm. Cysteine capping was successfully confirmed by Fourier transform infrared resonance (FTIR) spectroscopy and elemental analysis (CHN). Also, the factors of letrozole adsorption were optimized and the linear and non-linear forms of isotherms and kinetics were studied. Confirmation of the adsorption data of letrozole by cysteine capped nanoparticles in the Langmuir isotherm model indicated the homogeneous binding site of modified nanoparticles surface. Furthermore, the adsorption rate was kinetically adjusted to the pseudo-second-order model, and a high adsorption rate was observed, indicating that cysteine coated nanoparticles are a promising adsorbent for letrozole delivery. Finally, the kinetic release profile of letrozole loaded modified nanoparticles in simulated gastric and intestinal buffers was studied. Nearly 40% of letrozole was released in simulated gastric fluid with pH 1.2, in 30 min and the rest of it (60%) was released in simulated intestinal fluid with pH 7.4 in 10 h. These results indicate the efficiency of the cysteine capped AgNPs for adsorption and release of drug letrozole for breast cancer therapy.

• Biomaterials and Biomechanics in Bioengineering
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• 제4권1호
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• pp.21-32
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• 2019

Eggshell is a waste material after the usage of egg. In this work, biowaste chicken eggshells were used for preparing carbonated hydroxyapatite (HA) nanoparticles of high purity through aqueous precipitation method at room temperature. The eggshell-derived HA will be a cost-effective bioceramics for biomedical applications and an effective material-recycling technology. Additionally, mulberry leaf extract was used as a template to regulate the morphology, size and crystallinity of HA, and the effects of pH value were also examined. Characterization of the samples was performed by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Scanning electron microscopy (SEM) was used to determine the size, shape and morphology of HA. The results indicate that only one phase of HA were synthesized in the both absence and presence of mulberry leaf extract at pH of 7 and above, while DCPD or DCPA/DCPD phase was observed at pH 4 condition. The crystallite sizes of the HA samples obviously decreased when adding mulberry leaf extract as a template, while they decreased gradually as the solution pH levels increased. With increasing pH level from 7 to 14, the rod-like HA nanoparticles gradually changed to spherical shape at pH 14. Note that, the obtained product is Mg and Sr containing A- and B-type carbonate HA at alkaline pH and it can be a potential material for biomedical applications.