• Macromolecular Research
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• v.16 no.1
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• pp.45-50
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• 2008

This study examined the swelling behavior and in vitro release of a model drug, tetracycline-HCl, from alginate and alginate-polyaspartate (Alg-PASP) composite gel beads. The alginate and Alg-PASP composite beads were prepared using an ionic crosslinking method with aqueous $Ca^{2+}$. Their microporous morphology was observed by scanning electron microscopy. The swelling ratio of the beads in different media varied according to their composition, cross-linking density ($Ca^{2+}$ concentration), and pH of the aqueous medium. The in vitro release experiment of the tetracycline-HCl encapsulated beads in different media suggests that the release of the drug is governed mainly by the swelling properties of the polymer network. The presence of PASP was found to significantly influence the swelling properties and drug release profile.

• Journal of Pharmaceutical Investigation
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• v.39 no.5
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• pp.333-337
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• 2009

We aimed to optimize the formulation of porcine placental extract (PPE)-loaded liposomes for intramuscular administration and to investigate the effect of surface charges on the muscular retention in mice. PPE-loaded liposomes were formulated to have neutral, anionic, or cationic surface charges. The in vitro release profiles were studied by spectrofluorometry. In vivo distribution patterns at mice were studied using molecular imaging technology. Among the three types of liposomes, 1,2-dioleoyl-3-trimethylammonium-propane and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-based cationic liposomes showed the most prolonged in vitro release profile. Consistent with the in vitro results, the in vivo distribution study revealed that the cationic liposomes were retained at the site of administration for the longest period. Our results suggest the potential of cationic PPE-loaded liposomes for sustained release of the components after intramuscular administration.

• Archives of Pharmacal Research
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• v.15 no.4
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• pp.283-288
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• 1992

This work was performed to investigate the effects of brazilin in vitro on mitrogen-induced proliferation, ConA-induced TCGF release and responsiveness to recombinant-induced proliferation, ConA-induced TCGF release and responsiveness to recombinant IL-2 using splenocytes from C57BL/6 female mice. Brazilin (29-80 ng/ml) caused a noticeable increase in TCGF production of splenocytes, but did not affect responsivness to recombinant IL-2, the expression of ConA-induced high affinity IL-2 receptor and mitogen-induced proliferation of splenocytes.

• Macromolecular Research
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• v.8 no.2
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• pp.80-88
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• 2000

Biodegradable microspheres were prepared with poly(L-lactide-co-glycolide) (PLGA, 75 : 25 by mole ratio) by an oil/oil solvent evaporation method for the sustained release of anti-AIDS virus agent, AZT The microspheres of relatively narrow size distribution (7.6$\pm$ 3.8 ㎛) were obtained by controlling the fabrication conditions. The shape of microspheres prepared was smooth and spherical. The efficiency of AZT loading into the PLGA microsphere was over 93% compared to that below 15% for microspheres by a conventional water/oil/water method. The effects of Preparation conditions on the morphology and in vitro AZT release pattern were investigated. in vitro release studies showed that different release pattern and release rates could be achieved by simply modifying factors in the fabrication conditions such as the type and amount of surfactant, initial amount of loaded drug, the temperature of solvent evaporation, and so on. PLCA microspheres prepared by 5% of initial drug loading, 1.0% (w/w) of surfactant concentration, and 25$\^{C}$ of solvent evaporation temperature were free from initial burst effect and a near-zero order sustained release was observed. Possible mechanisms of the near-zero order sustained release for our system have been proposed.

• Archives of Pharmacal Research
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• v.15 no.2
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• pp.162-168
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• 1992

Release characteristics of five different types of hydrophilic albumin microspheres (HAM) containing different ratios of methotrexate-albumin (MTX-HSA) conjugates to free MTX: 1 : 0 (HAMC), 3 :1 (HAMC 3F), 1 :1 (HAMCF), 1:3 (HAMCF3) and 0 : 1 (HAMF) were investigated in the absence or presence of protease using dissolution tester. In all the HAMs studied except HAMC, the MTX was released bi-exponentially in the absence of protease; an initial fast release period up to approximately 6h, and thereafter the release rate was very much slower. The fast release of MTX from the HAMs (such as HAMC3F, HAMCF, HAMCF3 and HAMF) at the initial phase in probably due to the release of "physically associated" MTX from the core of the HAMs. The initial rate constants were 7.2, 8.7, 8.5 and 5.9 times greater than the second rate constants for HAMF, HAMCF3, HAMCF and HAMC3F, respectively. MTX release from HAMC was very slow and mono-phasic. It was at most 2.2% of the total entrapped amount by 24 h. The protease accelerated the release of MTX from the HAMs. The percentages of MTX released from HAMs up to 24 h were 100, 89.0, 75.0, 66.0 and 61.0% for HAMF, HAMCF3, HAMCF, HAMC3F and HAMC, respectively in the presence of protease and the corresponding values in the absence of protease were 30.2 19.0, 10.0, 6.5 and 2.2%, respectively. In vitro release of MTX in the presence of protease varied according to the ratios of MTX-HSA conjugates to MTX; the data set from HAMF, HAMCF3 and HAMCF fits better to monophasic first-order profile more adequately than to zero-order profile, that of HAMC3 monophasic first-order, and that of HAMC to bi-phasic zero-order. Above results suggested that zero-order release rate can be achieved by adjusting the ratio of MTX-HSA conjugates to MTX in the preparation of HAMs such as HAMC3F.as HAMC3F.

• Journal of Environmental Health Sciences
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• v.26 no.4
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• pp.115-121
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• 2000

To evaluate the cytotoxicity of cadmium compounds, this study was conducted to measure the in vitro magnetometry, LDH release and cellular apoptosis using alveolar macrophages of hamsters. A series of magnetometric measurements in cadmium-added groups showed a significant dose-dependent decay of the relaxation curves. The LDH release rates showed a dose-dependently increasing tendency as the dose gradually increased. The positive rates of apoptosis were significantly higher in cadmium-added groups than the control groups. Conclusively, the cytotoxicity increased in a dose dependent way as the concentration of cadmium added increased, which reflected in the decay of relaxation curve in magnetometry, and increased LDH release rate and positive rate of apoptosis.

• Journal of Pharmaceutical Investigation
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• v.18 no.4
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• pp.187-195
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• 1988

Poorly permeable $Eudragit^{\circledR}$ RS 100 polymer was used as a wall material for the microencapsulation of zipeprol dihydrochloride by a phase separation method from chloroform-cyclohexane system with 5% polyisobutylene in cyclohexane, and microcapsules obtained were evaluated in vitro by particle size analysis, scanning electron microscopy, drug release test and in vivo bioavailability test in rats. The mechanism of drug release from microcapsules appeared to fit Higuchi matrix model kinetics. The area under the first moment of plasma concentration-time curve of the microcapsules obtained was considerably increased (p<0.05) as compared with that from zipeprol dihydrochloride oral solution. Therefore, it may be suggested that $Eudragit^{\cirledR}$ RS 100 coated zipeprol dihydrochloride microcapsules can be used as a sustained release medication.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.147-153
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• 2018

PLGA microcapsule particles encapsulating BSA aqueous solutions were prepared using a water-in-oil-in-water emulsion method. The morphology, particle size, BSA encapsulating efficiency, and in-vitro release test were also studied using the microcapsule particles. In the outer aqueous phase, an emulsifier, e.g., PVA, was replaced with metal salts for surface solidification. Scanning electron microscopy (SEM) showed that the microcapsule particles had smooth surfaces and were between $1{\mu}m$ and $7{\mu}m$ in size. The microcapsule particle morphology was affected directly by the ratio between the polymer solution and inner aqueous solution, and composition of the outer aqueous solution. The factors also partially affected the BSA encapsulation efficiencies and in-vitro release rates. All the microcapsule particles showed an initial burst release through the in-vitro release test. On the other hand, the particles also showed a relatively long release period. Metal salts could be good choices to replace the emulsifier to solidify the microcapsule particle surfaces.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.295.1-295.1
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• 2003

A suitable model for the estimation of the drug release from nanoparticles has been varied and problematic, especially for the release from lipid nanoparticles containing water-insoluble drugs, due to the difficult particle collection from the release medium. Dialysis membrane has been widely used for the release test from colloidal carrier systems. The amount of drug from the carriers in normal dialysis diffusion technique was very low typically. (omitted)

• The Korean Journal of Physiology
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• v.10 no.1
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• pp.55-59
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• 1976

Most investigators have come to stress two different concepts of mechanism controlling renin release; intrarenal baroreceptor theory and the macula densa theory(Vander 1967, Thurau and Masson 1974). In the macula densa theory, the specific macula densa parameter, most commonly suggested as a possible signal, is either the osmolality or the concentration of sodium in the tubular fluid (Thurau 1964, Vander and Miller 1964, Reeves and Sommers 1965). It has been shown that sodium plays an important role in the release of renin either in vivo (Thurau 1964, Vander and Miller 1964, Thurau et al 1972) or in vitro experiments(Oelkers et al 1970, Hammerson et al 1971, Michelakis 1971). On the other hand the osmolality appears to have no effect on the release of renin in vivo (Vander 1967, Thurau and Masson 1974). However, there has been little attempt to study the effect of osmolality on in vitro renin release. We therefore undertook the present investigation to elucidate the effect of osmolality on renin release and to further test the sodium influence upon the release of renin from isolated kidney slice preparations. Isolated renal cortical slices were washed with normal Krebs-Hensenleit bicarbonate buffer solution and incubated for 30 minutes in a medium containing an appropriate concentration of sodium and osmolality. The renin released into the medium was measured by the method of radioimmunoassay(Haber et al 1969). The results obtained are as follows; 1. The release of renin from renal cortical slices was progressively inhibited as the sodium concentration in the medium increased. 2. No significant alteration in renin release was observed when osmolality of the medium was changed. These results suggest that the release of renin from the renal cortical slices is directly affected by the changes in sodium concentration in the medium, but is not influenced by the alterations in osmolality.