Investigation of polymeric excipients for dutasteride solid dispersion and its physicochemical characterization

김남아,최두형,임준열,김기현,임대곤,이은희,박은석,정성훈 대한약학회 2014 Archives of Pharmacal Research Vol.37 No.2

To investigate the effects of polymeric excipientsfor dutasteride solid dispersion, experimental approachestogether with physical interactions at molecular levelwere evaluated. The drug and various polymers (anionic,amphiphilic, and hydrophilic) were mixed physically intodifferent ratios and their thermodynamic and physicalproperties were analyzed by differential scanning calorimetryand Fourier transform-infrared spectroscopy,respectively. The enhanced equilibrium solubility of dutasteridewas also investigated. Dutasteride is non-ionicand showed low solubility in the tested pH ranges (lowerthan the detection limit of 20 ng/mL). Kollidon MAE100P, an anionic polymer, showed enhanced dutasteridesolubility in aqueous solution followed by hydrophilicKollidon SR and the amphiphilic polymer, Soluplus. Melting point (Tm) of dutasteride was 249.7 C and wasdecreased to 229.84 C when mixed evenly with KollidonMAE 100P. However, the melting point was not detected ata ratio of 1:4 since it fully dissolved or dispersed in the polymer. Glass transition temperature (Tg) of differentcompositions exhibited strong interaction of polymer anddrug. The result was supported by spectra evidence thatKollidon MAE 100P forms hydrogen bonds with dutasteridepresenting strong physical interaction with theprimary amine group of dutasteride. This study supports aconvenient method that together with microscopic observationcan perform polymer selection and characterizesolid dispersions.

Evaluation of protein formulation and its viscosity with DSC, DLS, and microviscometer

김남아,정성훈,임대곤,임준열,김기현,심우선,강내규 한국약제학회 2014 Journal of Pharmaceutical Investigation Vol.44 No.4

The viscosity of highly concentrated proteinsolutions was evaluated using lysozyme as model protein. Viscosity profiles of lysozyme were examined with theeffect of buffer and pH-value at various concentrations. The viscosity of lysozyme dissolved in water increasedcontinuously with the concentration as the slope of shearstress against shear rate increased with the concentration. In addition, the viscosity of lysozyme was higher in histidinebuffer than in acetate buffer at selected pH ranges. The effect of various excipient concentrations was alsoinvestigated in means of unfolding transition temperature(Tm), viscosity, hydrodynamic size and zeta potential byusing differential scanning calorimetry (DSC), microviscometerand dynamic light scattering (DLS). The selectedexcipients except surfactants increased the viscosity ofprotein solution with their concentration. Carbohydratesincreased the viscosity relatively higher than amino acidsand also they increased the conformational stability (Tm) byenhancing the protein molecule more in compact form. Also amino acids increased the viscosity but decreased theconformational stability since they seemed to be only dispersedin the solution avoiding protein–protein interactions,resulting in a decrease of zeta potential. Consequently, the applied methods—DSC, DLS and microviscometerdemonstrated the potential to develop ahighly concentrated protein formulation to decrease thehigh viscosity effect with acceptable conformationalstability.

Optimization of Protein Solution by a Novel Experimental Design Method using Thermodynamic Properties

김남아,정성훈,In Bok An,이상열,박은석 대한약학회 2012 Archives of Pharmacal Research Vol.35 No.9

In this study, the structural stability of hen egg white lysozyme in solution at various pH levels and in different types of buffers, including acetate, phosphate, histidine, and Tris, was investigated by means of differential scanning calorimetry (DSC). Reasonable pH values were selected from the buffer ranges and were analyzed statistically through design of experiment (DoE). Four factors were used to characterize the thermograms: calorimetric enthalpy (ΔH), temperature at maximum heat flux (Tm), van’t Hoff enthalpy (ΔHV), and apparent activation energy of protein solution (Eapp). It was possible to calculate Eapp through mathematical elaboration from the Lumry-Eyring model by changing the scan rate. The transition temperature of protein solution, Tm, increased when the scan rate was faster. When comparing the Tm, ΔHV, ΔH, and Eapp of lysozyme in various pH ranges and buffers with different priorities, lysozyme in acetate buffer at pH 4.767 (scenario 9) to pH 4.969 (scenario 11) exhibited the highest thermodynamic stability. Through this experiment, we found a significant difference in the thermal stability of lysozyme in various pH ranges and buffers and also a new approach to investigate the physical stability of protein by DoE.

Process cycle development of freeze drying for therapeutic proteins with stability evaluation

임준열,김남아,임대곤,김기현,최두형,정성훈 한국약제학회 2016 Journal of Pharmaceutical Investigation Vol.46 No.6

Many therapeutic proteins have been launched in market or gone into development stages for their high therapeutic efficacy. The proteins can be developed mainly as liquid or solid dosage forms; pre-filled syringes or freeze-dried. Regardless of the dosage forms, they have several stability issues due to the intrinsic properties of the proteins, which can have adverse effects on their efficacy such as loss of bioactivity and immunogenicity. In order to achieve enough stability of proteins, a solid-state dosage form, freeze-dried, has been preferred as providing a better shelf-life. Freeze drying process has become an important method to manufacture, store, and distribute the protein drug products. Despite its advantages, the freeze drying process still has challenges of stability issues and requires optimization. This review provides a basic concept of the freeze drying process while highlighting several stability issues encountered during the development of freeze drying cycle for protein formulations. Furthermore, various excipients used to stabilize freeze-dried protein formulations are also introduced.

Effects of thermal and mechanical stress on the physical stability of human growth hormone and epidermal growth factor

임준열,김남아,임대곤,김기현,정성훈 대한약학회 2015 Archives of Pharmacal Research Vol.38 No.8

Thermal and mechanical stress conditions were applied to two model proteins, human growth hormone (hGH) and epidermal growth factor (EGF), to evaluate protein stability during the manufacturing process, focusing on protein secondary structure and aggregation. The samples were analyzed with differential scanning calorimetry (DSC), circular dichroism (CD), and size-exclusion chromatography (SEC). The monomer and aggregation contents were obtained by SEC and the proteins’ secondary structure on exposure to thermal stress was evaluated by CD. DSC showed that the transition temperature (Tm) of hGH and EGF was 74.43 and 79.11 C, respectively. The accelerated thermal stress temperature was set at 70 C. The monomer content of hGH decreased from 97.8 to 82.3 % in response to thermal stress. However, the monomer content of EGF decreased significantly from 33.73 to 5.61 %. The hGH and EGF showed an increase in a-helix content and a decrease in b-sheet (antiparallel and parallel b-sheet). Moreover, the contents changed significantly during the first 1 h and then changed slightly for the remaining time. On the other hand, shaking stress showed that hGH was highly affected compared to EGF. The hGH monomer steadily decreased and only the half the monomer content remained at 3 h. It is suspected that the shaking stress induced hGH adsorption to the gas–liquid interface, which may facilitate protein denaturation. The results indicate that protective excipients might be necessary for inevitable stress conditions during the developmental process. The stability of each protein differed with respect to specific stress conditions. Therefore, an arrayof complementary analytical methods might be required to evaluate the protein stability.

Bioequivalence of tacrolimus formulations with different dynamic solubility and in-vitro dissolution profiles

권민창,염대일,김남아,최두형,박준상,왕훈식,유선동,정성훈 대한약학회 2015 Archives of Pharmacal Research Vol.38 No.1

This study was to evaluate the pharmacokineticsand bioequivalence of two tacrolimus formulationswhich had different in vitro drug release profiles. Dynamicsolubility, in vitro dissolution profiles of the two formulations,and their influence on pharmacokinetics wereexamined. The male volunteers were randomly assigned toreceive a single 1-mg capsule of the test or reference formulationand pharmacokinetic parameters were determinedusing a noncompartmental method. The two formulationsreleased [85 % of tacrolimus in water within 30 min,which passed the criterion of evaluating the test formulation. However, the test formulation produced a faster initialrelease rate and plateaued in about 15 min, while the referenceshowed almost zero order initial release profiles. The AUC0-? values were 145.92 (reference) and140.49 ng h/mL (test). The mean Cmax was 15.70 (reference)and 16.08 ng/mL (test) with Tmax values of 1.63 and1.60 h, respectively. The t1/2 for the reference and testformulations was 29.12 and 27.85 h, respectively. Relativebioavailability was calculated to be 96.28 %. The pointestimates for the mean ratio of the test to reference for theAUC0-t and Cmax were 0.969 and 1.026, respectively,satisfying the criterion for bioequivalence. The resultssuggest that the test formulation is pharmacokineticallyequivalent to the reference in terms of both rate and extentof absorption. Even though the in vitro dissolution profilesof the formulations might not be equivalent, the pharmacokineticsindicated bioequivalence. Therefore, whendeveloping poorly soluble drugs, it might be beneficial topay attention to the dynamic solubility as well as dissolution profiles.

Crystal Structure of DsbA from Corynebacterium diphtheriae and Its Functional Implications for CueP in Gram-Positive Bacteria

엄시현,김진식,송새미,김남아,정성훈,하남출 한국분자세포생물학회 2015 Molecules and cells Vol.38 No.8

In Gram-negative bacteria in the periplasmic space, the dimeric thioredoxin-fold protein DsbC isomerizes and reduces incorrect disulfide bonds of unfolded proteins, while the monomeric thioredoxin-fold protein DsbA introduces disulfide bonds in folding proteins. In the Gram-negative bacteria Salmonella enterica serovar Typhimurium, the reduced form of CueP scavenges the production of hydroxyl radicals in the copper-mediated Fenton reaction, and DsbC is responsible for keeping CueP in the reduced, active form. Some DsbA proteins fulfill the functions of DsbCs, which are not present in Gram-positive bacteria. In this study, we identified a DsbA homologous protein (CdDsbA) in the Corynebacterium diphtheriae genome and determined its crystal structure in the reduced condition at 1.5 Å resolution. CdDsbA consists of a monomeric thioredoxin-like fold with an inserted helical domain and unique N-terminal extended region. We confirmed that CdDsbA has disulfide bond isomerase/reductase activity, and we present evidence that the N-terminal extended region is not required for this activity and folding of the core DsbA-like domain. Furthermore, we found that CdDsbA could reduce CueP from C. diphtheriae.

SNS 환경에서의 잊혀질 권리 구현 방안에 대한 고찰

신철호 ( Cheol Ho Sin ),김남아 ( Nam A Kim ),고병우 ( Byeong Woo Go ),김성민 ( Kim Seong Min ),이재동 ( Jae Dong Lee ),박종혁 ( Jong Hyuk Park ) 한국정보처리학회 2013 한국정보처리학회 학술대회논문집 Vol.20 No.2

오늘날 전세계의 사람이 이용하는 SNS 상에 존재하는 보안 위협은 정보주체의 개인정보를 유출하고 스팸, 피싱 등의 2 차 피해를 야기하는 등 치명적인 결과를 초래한다. 본 논문에서는 잊혀질 권리와 SNS의 개념을 파악하고 SNS 상에 존재하는 보안 위협에 대해 논의하며 보안 위협을 해소하고 SNS 환경에서의 잊혀질 권리를 실현할 수 있는 UPP, Dual Watermarking Scheme, FaceCloak 등 기술적 방안을 제시한다.