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1.
The purpose of this study was to develop and evaluate a dialysisin vitro release technique for peptide-containing poly(d, 1-lactide-coglycolide) (PLGA) microspheres (ms) that would correlate within vitro data. Using a luteinizing hormone- releasing hormone analogue (LHRH), Orntide acetate, solubility and stability were determined
in 0.1 M phosphate buffer (PB), pH 7.4, and in 0.1 M acetate buffer (AB), pH 4.0, with highperformance liquid chromotography
(HPLC), and peptide permeability through a dialysis membrane (molecular weight cut-off 300,000) was determined. Orntide ms
were prepared by a dispersion/solvent extraction/evaporation method and characterized for drug content (HPLC), particle size
distribution (laser diffraction method), and surface morphology (scanning electron microscopy).In vitro release was studied in PB using a conventional extraction method and with a new dialysis method in AB. Gravimetric analyses
of polymer mass loss and matrix hydration, and peptide adsorption to blank PLGA ms (50∶50, Mw 28 022) were carried out in PB and AB upon incubation at 37°C. Serum Orntide and testosterone levels in rats after administration
of Orntide ms were determined by radioimmunoassay. Orntide acetate solubility was influenced by pH; approximately 2.3 mg/mL
dissolved in PB and >18 mg/mL in AB. Stability was pH- and temperature-dependent. The peptide was very stable at pH 4.0, 4°C,
but degraded rapidly at pH 7.4,37°C. Peptide permeability through the dialysis membrane was accelerated by agitation and>95%
equilibrium was reached within 48 hours. The overall release rate was higher with the dialysis method. Mass loss of the Orntide
ms was faster in AB (50% loss in 3 weeks: 95% in 35 days) than in PB (65% in 35 days). In contrast, hydration after 35 days
was 4-fold higher in PB. The nonspecific adsorption to blank ms was greater in PB (128 μ g Orntide/10 mg PLGA) compared with
AB (<5 μ g Orntide/10 mg PLGA). Administration of 30-day Orntide PLGA ms to rats resulted in an initial serum Orntide level
of 21 ng/mL after 6 hours and a Cmax of 87 ng/mL after 6 days. Testesterone levels were suppressed immediately after ms administration (3 mg Orntide/Kg) from
5.2 ng/mL to 0.3 ng/mL (after 24 hours) and remained suppressed for 38 days. Orntide acetate solubility and degradation kinetics
were markedly influenced by pH of the buffer systems and mass loss; matrix hydration, as well as the nonspecific adsorption
to blank ms, was pH-dependent. Thein vitro release profile obtained with the dialysis method in AB correlated well with thein vivo data, therepy providing a more reliable prediction ofin vivo performance. 相似文献
2.
The purpose of this research was to study the chemical reactivity of a somatostatin analogue octreotide acetate, formulated
in microspheres with polymers of varying molecular weight and co-monomer ratio under in vitro testing conditions. Poly(D,L-lactide-co-glycolide)
(PLGA) and poly(D,L-lactide) (PLA) microspheres were prepared by a solvent extraction/evaporation method. The microspheres
were characterized for drug load, impurity content, and particle size. Further, the microspheres were subjected to in vitro
release testing in acetate buffer (pH 4.0) and phosphate buffered saline (PBS) (pH 7.2). In acetate buffer, 3 microsphere
batches composed of low molecular weight PLGA 50∶50, PLGA 85∶15, and PLA polymers (≤10 kDa) showed 100% release with minimal
impurity formation (<10%). The high molecular weight PLGA 50∶50 microspheres (28 kDa) displayed only 70% cumulative release
in acetate buffer with significant impurity formation (∼24%). In PBS (pH 7.4), on the other hand, only 50% release was observed
with the same low molecular weight batches (PLGA 50∶50, PLGA 85∶15, and PLA) with higher percentages of hydrophobic impurity
formation (ie, 40%, 26%, and 10%, respectively). In addition, in PBS, the high molecular weight PLGA 50∶50 microspheres showed
only 20% drug release with ∼60% mean impurity content. The chemically modified peptide impurities inside microspheres were
structurally confirmed through Fourier transform-mass spectrometry (FT-MS) and liquid chromatography/mass spectrometry (LC-MS/MS)
analyses after extraction procedures. The adduct compounds were identified as covalently modified conjugates of octreotide
with lactic and glycolic acid monomers within polymeric microspheres. The data suggest that due to steric hindrance factors,
polymers with greater lactide content were less amenable to the formation of adduct impurities compared with PLGA 50∶50 copolymers. 相似文献
3.
The aim of this study was the development of a veterinary dosage form constituted by injectable biodegradable microspheres
designed for the subcutaneous release of carboplatin, a chemotherapeutic drug. Poly(D,L-lactide) (PDLLA) microspheres were
prepared by an emulsification/spray-drying method, using the drug-to-polymer weight ratios 1∶9 and 1∶5; blank microspheres
(1% w/v) were prepared as a comparison. Microparticles were characterized in terms of morphology, encapsulation efficiency,
and in vitro drug release behavior. In vivo tests were conducted on rats by subcutaneous injection of microsphere aqueous
suspensions. Levels of carboplatin were evaluated both in the skin and in serum. The microparticles obtained had a spherical
shape; particle size ranged from 5 to 7 μm, dependent on drug loading. Microspheres were able to control the in vitro release
of the drug: approximately 90% to 100% of the carboplatin was released over 30 days. In vivo results showed that the microspheres
were able to release high drug amounts locally, and sustained serum levels of drug were also achieved. Based on these results,
carboplatin-loaded PDLLA microspheres may be useful for local delivery of the antineoplastic drug to the tumor, avoiding tumor
recurrence in small animals, and may decrease the formation of distant metastases.
Published: September 20, 2005 相似文献
4.
Khaled A. Khaled Hatem A. Sarhan Mohamed Abbas Ibrahim Azza H. Ali Youssef W. Naguib 《AAPS PharmSciTech》2010,11(2):859-869
This study aimed at preparation of a sustained-release steroidal treatment for chronic inflammatory conditions, such as rheumatoid
arthritis. To achieve such a goal, biodegradable poly-lactide-co-glycolide prednisolone-loaded microspheres were prepared
using o/w emulsion solvent evaporation method. Formulation parameters were adjusted so as to optimize the microsphere characteristics.
The prepared microspheres exhibited smooth and intact surfaces, with average size range not exceeding 65 μm. The encapsulation
efficiency percent of most microsphere formulations fell within the range of 25–68%. Drug release from these microspheres
took place over 4 weeks, with near-to-zero-order patterns. Two successful formulations were chosen for the treatment of unilateral
arthritis, induced in mice using Freund's complete adjuvant (FCA). Inflammatory signs of adjuvant arthritis included severe
swelling of the FCA-injected limbs, in addition to many histopathological lesions. These included inflammatory cell infiltration,
synovial hyperplasia, cartilage, and bone erosion. Parenteral administration of the selected formulae dramatically reduced
the swelling of the FCA-injected limbs. In addition, histological examination revealed that the microsphere treatment protocol
efficiently protected cartilages and bones of mice, injected with FCA initial and booster doses, from erosion. These results
could not be achieved by a single prednisolone dose of 5 mg/kg. 相似文献
5.
This research compared the binding and release of recombinant human bone morphogenetic protein 2 (rhBMP-2) with a series of
hydrophobic and hydrophilic poly-lactide-co-glycolide (PLGA) copolymers. Porous microspheres were produced via a double emulsion
process. Binding and incorporation of protein were achieved by soaking microspheres in buffered protein solutions, filtering,
and comparing protein concentration remaining to nonmicrosphere-containing samples. Protein release was determined by soaking
bound microspheres in a physiological buffer and measuring protein concentration (by reversed-phase high-performance liquid
chromatography) in solution over time. Normalized for specific surface area and paired by polymer molecular weight. microspheres
made from hydrophilic 50∶50 or 75∶25 PLGA bound significantly more protein than microspheres made from the corresponding hydrophobic
PLGA. Increased binding capacity correlated with higher polymer acid values. With certain polymers, rhBMP-2 adsorption was
decreased or inhibited at high protein concentration, but protein loading could be enhanced by increasing the protein solution:PLGA
(volume:mass) ratio or by repetitive soaking. Microspheres of various PLGAs released unbound protein in 3 days, whereas the
subsequent bound protein release corresponded to mass loss. RhBMP-2 binding to PLGA was controlled by the acid value, protein
concentration, and adsorption technique. The protein released in 2 phases: the first occurred over 3 days regardless of PLGA
used and emanated from unbound, incorporated protein, while the second was controlled by mass loss and therefore was dependent
on the polymer molecular weight. Overall, control of rhBMP-2 delivery is achievable by selection of PLGA microsphere carriers.
Published: October, 7, 2001. 相似文献
6.
The purpose of this research was to prepare spray-dried mucoadhesive microspheres for nasal delivery. Microspheres composed
of hydroxypropyl methylcellulose (H), chitosan (CS), carbopol 934P (CP) and various combinations of these mucoadhesive polymers,
and maltodextrin (M), colloidal silicon dioxide (A), and propylene glycol (P) as filler and shaper, were prepared by spray-drying
technique. Using propranolol HCl as a model drug, microspheres were prepared at loadings exceedings 80% and yields between
24% and 74%. Bulky, free flowing microspheres that had median particle size between 15 and 23 μm were obtained. Their zeta
potential was according to the charge of polymer. Adhesion time of mucoadhesive microspheres on isolated pig intestine was
ranked, CS>CP: H>CP>H, while the rank order of swelling was CP>CS>H. Increasing the amount of CP in CP∶H formulations increased
the percentage of swelling. Infrared (IR) spectra showed no interaction between excipients used except CS with acetic acid.
The release of drug from CP and CP∶H microspheres was slower than the release from H and CS microspheres, correlated to their
viscosity and swelling. Long lag time from the CP microspheres could be shortened when combined with H. The permeation of
drug through nasal cell monolayer corresponded to their release profiles. These microspheres affected the integrity of tight
junctions, relative to their swelling and charge of polymer. Cell viability was not affected except from CS microspheres,
but recovery could be obtained. In conclusion, spray-dried microspheres of H, CS, CP, and CP∶H could be prepared to deliver
drug through nasal cell monolayer via the opening of tight junction without cell damaging.
Published: February 10, 2006 相似文献
7.
This paper describes the formulation of a biodegradable microparticulate drug delivery system containing clodronate, a bisphosphonate
intended for the treatment of bone diseases. Microspheres were prepared with several poly(D,L-lactide-co-glycolide) (PLGA)
copolymers of various molecular weights and molar compositions and 1 poly(D,L-lactide) (PDLLA) homopolymer by a water-in-oil-in-water
(w/o/w) double emulsion solvent evaporation procedure. Critical process parameters and formulation variables (ie, addition
of stabilizing agents) were evaluated for their effect on drug encapsulation efficiency and clodronate release rate from microparticles
Well-formed clodronate-loaded microspheres were obtained for all polymers by selecting suitable process parameters (inner
water/oil volume ratio 1∶16, temperature-raising rate in the solvent evaporation step 1°C/min, 2% wt/vol NaCl in the external
aqueous phase). Good yields were obtained in all batches of clodronate microspheres (above 60%); drug encapsulation efficiencies
ranged between 49% and 75% depending on the polymer used. Clodronate release from all copolymer microspheres was completed
in about 48 hours, while those from PDLLA microspheres required about 20 days. The change of microsphere composition by adding
a surfactant such as Span 20 or a viscosing agent such as carboxymethylcellulose extended the long-term release up to 3 months.
Clodronate was successfully entrapped in PLGA and PDLLA microspheres, and drug release could be modulated from 48 hours up
to 3 months by suitable selection of polymer, composition, additives, and manufacturing conditions.
Published: July 11, 2001. 相似文献
8.
The objectives of this study were to evaluate the physical structure and the release mechanisms of theophylline microspheres
made of Eudragit S 100 polymer as an enteric polymer, combined with a nonerodible polymer, Eudragit RL 100. In the preparation
process, polymer combinations (1:1) were dissolved in an organic solvent mixture composed of acetone and methanol at a specific
ratio containing a theoretical drug loading of approximately 15%. Two microsphere formulations (LS1 and LS2) were prepared
at two different total polymer concentrations (10% in LS1 and 12.7% in LS2). Dissolution studies were carried out using US
Pharmacopeia Dissolution Apparatus II in an acidic medium for 8 h and in an acidic medium (2 h) followed by a slightly basic-buffered
medium for 10 h. Both LS1 and LS2 microsphere formulations produced particles that were spherical in shape and had very narrow
size distributions with one size fraction comprising 70–80% of the yield. Scanning electron microscopy and quantitative Fourier
transform infrared were used for microsphere physical structure evaluation. Except for the absence of drug crystals, photomicrographs
of both LS microspheres after dissolution in pH 1.2 and 7.2 buffer solutions were similar to those before dissolution. Dissolution
results indicated the ability of LS microspheres to minimize drug release during the acid stage. However, in the slightly
basic medium that followed the acidic stage, the drug release was sustained and controlled in its kinetics and data fitted
to Peppas equation indicated a case II transport suggesting that the drug release is mainly through swelling/erosion mechanism. 相似文献
9.
The objective of this work was to prepare and evaluate ketorolac tromethamine-loaded albumin microspheres using a factorial
design. Albumin microspheres were prepared by emulsion cross-linking method. Selected formulations were characterized for
their entrapment efficiency, particle size, surface morphology, and release behavior. Analysis of variance (ANOVA) for entrapment
efficiency indicated that entrapment efficiency is best fitted to a response surface linear model. From the statistical analysis
it was observed that as the drug:polymer (D∶P) ratio and volume of glutaraldehyde increased, there was a significant increase
in the encapsulation efficiency. Scanning electron microscopy of the microspheres revealed a spherical, nonporous and uniform
appearance, with a smooth surface. Based on the entrapment efficiency and physical appearance, 9 formulations were selected
for release study. The maximum particle size observed was below 40 μm. The release pattern was biphasic, characterized by
an initial burst effect followed by a slow release. All selected microspheres, except those having less polymer proportion
(D∶P ratio is 1∶1), exhibited a prolonged release for almost 24 hours. On comparingr
2 values for Higuchi and Peppas kinetic models, different batches of microspheres showed Fickian, non-Fickian, and diffusion
kinetics. The release mechanism was regulated by D∶P ratio and amount of cross-linking agent. From the experimental data obtained
with respect to particle size and extent of drug relaase, it could be concluded that the prepared microspheres are useful
for once-a-day intramuscular administration of ketorolac tromethamine.
Published: February 23, 2007 相似文献
10.
Chitosan microspheres as drug delivery system have attained importance and attracted the attention of researchers in last
few years. This study was aimed toward the elucidation of the effect of viscosity of external oil phase on the properties
of microspheres prepared by emulsification method. Chitosan microspheres were prepared utilizing oil phase of different viscosity
viz. castor oil, heavy liquid paraffin, light liquid paraffin and mixture of light paraffin, and petroleum ether (1:1 v/v ratio). Microspheres prepared in highly viscous castor oil exhibited an average size of 11.52 ± 0.57 μm with a percentage
drug entrapment of 43.12 ± 2.14. On the other hand, very small microspheres of 3.15 ± 0.04 μm and 68.87 ± 1.03% drug entrapment
were obtained when mixture of liquid paraffin and petroleum ether was utilized as oil phase. Effect of viscosity on percent
mucoadhesion, percent drug entrapment, zeta potential, percent process yield, etc. of microspheres has been observed. In vitro drug release in phosphate buffer pH 7.4 was determined for different batch of microspheres. The results revealed a difference
in the drug release pattern of the different microspheres prepared as a function of viscosity of different oil phase. Use
of low viscose oil resulted in the formulation of spherical and small size microspheres. This work was a part of our ongoing
thrust and project to develop microparticulate drug delivery system. 相似文献
11.
In this study, the use of biodegradable polymers for microencapsulation of naltrexone using solvent evaporation technique
is investigated. The use of naltrexone microspheres for the preparation of matrix devices is also studied. For this purpose,
poly(L-lactide) (PLA) microspheres containing naltrexone prepared by solvent evaporation technique were compressed at temperatures
above the Tg of the polymer. The effect of different process parameters, such as drug/polymer ratio and stirring rate during
preparation of microspheres, on the morphology, size distribution, and in vitro drug release of microspheres was studied.
As expected, stirring rate influenced particle size distribution of microspheres and hence drug release profiles. By increasing
the stirring speed from 400 to 1200 rpm, the mean diameter of microspheres decreased from 251 μm to 104 μm. The drug release
rate from smaller microspheres was faster than from larger microspheres. However, drug release from microspheres with low
drug content (20% wt/wt) was not affected by the particle size of microspheres. Increasing the drug content of microspheres
from 20% to 50% wt/wt led to significantly faster drug release from microspheres. It was also shown that drug release from
matrix devices prepared by compression of naltrexone microspheres is much slower than that of microspheres. No burst release
was observed with matrix devices. Applying higher compression force, when compressing microspheres to produce tablets, resulted
in lower drug release from matrix devices. The results suggest that by regulating different variables, desired release profiles
of naltrexone can be achieved using a PLA microparticulate system or matrix devices. 相似文献
12.
This study aimed at the preparation of a sustained-release 25-hydroxyvitamin D3 (25OHD) treatment for diabetic periodontitis, a known complication of diabetes. 25OHD-loaded polylactic acid (PLA) microspheres were prepared using oil-in-water emulsion–solvent evaporation method. The prepared microspheres exhibited intact surfaces, with average sizes ranging from 42.3 to 119.4 μm. The encapsulation efficiency ranged from 79.2% (w/w) to 88.5% (w/w), and the drug content was between 15.8% (w/w) and 17.8% (w/w). Drug release from the produced microspheres followed a near-to-zero-order release pattern and lasted over 10 weeks. In an in vitro model of diabetic periodontitis, the abnormal morphological changes and the decrease in the cell viability of bone marrow stromal cells could be effectively attenuated after the 25OHD-loaded microsphere application. Additionally, in a rat model of diabetic periodontitis, alveolar bone loss was inhibited and osteoid formation in the periodontium was promoted upon 25OHD-loaded microsphere treatment. In conclusion, 25OHD-loaded PLA microspheres may provide an effective approach for the treatment of this disease. 相似文献
13.
The objective of the present study was to develop once-daily sustained-release matrix tablets of nicorandil, a novel potassium
channel opener used in cardiovascular diseases. The tablets were prepared by the wet granulation method. Ethanolic solutions
of ethylcellulose (EC), Eudragit RL-100, Eudragit RS-100, and polyvinylpyrrolidone were used as granulating agents along with
hydrophilic matrix materials like hydroxypropyl methylcellulose (HPMC), sodium carboxymethylcellulose, and sodium alginate.
The granules were evaluated for angle of repose, bulk density, compressibility index, total porosity, and drug content. The
tablets were subjected to thickness, diameter, weight variation test, drug content, hardness, friability, and in vitro release
studies. The granules showed satisfactory flow properties, compressibility, and drug content. All the tablet formulations
showed acceptable pharmacotechnical properties and complied with in-house specifications for tested parameters. According
to the theoretical release profile calculation, a oncedaily sustained-release formulation should release 5.92 mg of nicorandil
in 1 hour, like conventional tablets, and 3.21 mg per hour up to 24 hours. The results of dissolution studies indicated that
formulation F-I (drug-to-HPMC, 1∶4; ethanol as granulating agent) could extend the drug release up to 24 hours. In the further
formulation development process, F-IX (drug-to-HPMC, 1∶4; EC 4% wt/vol as granulating agent), the most successful formulation
of the study, exhibited satisfactory drug release in the initial hours, and the total release pattern was very close to the
theoretical release profile. All the formulations (except F-IX) exhibited diffusion-dominated drug release. The mechanism
of drug release from F-IX was diffusion coupled with erosion. 相似文献
14.
The purpose of this study was to formulate topically effective controlled release ophthalmic acetazolamide liposomal formulations.
Reverse-phase evaporation and lipid film hydration methods were used for the preparation of reversephase evaporation (REVs)
and multilamellar (MLVs) acetazolamide liposomes consisting of egg phosphatidylcholine (PC) and cholesterol (CH) in the molar
ratios of (7∶2), (7∶4), (7∶6), and (7∶7) with or without stearylamine (SA) or dicetyl phosphate (DP) as positive and negative
charge inducers, respectively. The prepared liposomes were evaluated for their entrapment efficiency and in vitro release.
Multilamellar liposomes entrapped greater amounts of drug than REVs liposomes. Drug loading was increased by increasing CH
content as well as by inclusion of SA. Drug release rate showed an order of negatively charged > neutral > positively charged
liposomes, which is the reverse of the data of drug loading efficiency. Physical stability study indicated that approximately
89%, 77%, and 69% of acetazolamide was retained in positive, negative, and neutral MLVs liposomal formulations up to a period
of 3 months at 4°C. The intraocular pressure (IOP)-lowering activity of selected acetazolamide liposomal formulations was
determined and compared with that of plain liposomes and acetazolamide solution. Multilamellar acetazolamide liposomes revealed
more prolonged effect than REVs liposomes. The positively charged and neutral liposomes exhibited greater lowering in IOP
and a more prolonged effect than the negatively charged ones. The positive multilamellar liposomes composed of PC:CH:SA (7:4:1)
molar ratio showed the maximal response, which reached a value of −7.8±1.04 mmHg after 3 hours of topical administration.
Published: January 5, 2007 相似文献
15.
The purpose of this research was to investigate whether Eudragit S100 microspheres have the potential to serve as an oral
carrier for peptide drugs like insulin. Microspheres were prepared using water-in oil-in water emulsion solvent evaporation
technique with polysorbate 20 as a dispersing agent in the internal aqueous phase and polyvinyl alcohol (PVA)/polyvinyl pyrrolidone
as a stabilizer in the external aqueous phase. The use of smaller internal aqueous-phase volume (50 μL) and external aqueous-phase
volume (25 mL) containing PVA in the manufacturing process resulted in maximum encapsulation efficiency (81.8%±0.9%). PVA-stabilized
microspheres having maximum drug encapsulation released 2.5% insulin at pH 1.0 in 2 hours. In phosphate buffer (pH 7.4), microspheres
showed an initial burst release of 22% in 1 hour with an additional 28% release in the next 5 hours. The smaller the volumes
of internal and external aqueous phase, the lower the initial burst release. The release of drug from microspheres followed
Higuchi kinetics. Scanning electron microscopy of PVA-stabilized microspheres demonstrated spherical particles with smooth
surface, and laser diffractometry revealed a mena particle size of 32.51±20 μm. Oral administration of PVA stabilized microspheres
in normal albino rabbits (equivalent to 6.6 IU insulin/kg of animal weight) demonstrated a 24% reduction in blood glucose
level, with maximum plasma glucose reduction of 76±3.0% in 2 hours and effect continuing up to 6 hours. The area under the
percentage glucose reduction-time curve was 93.75%. Thus, our results indicate that Eudragit S100 microspheres on oral administration
can protect insulin from proteolytic degradation in the gastrointestinal tract and produce hypoglycemic effect. 相似文献
16.
Effects of Zinc Glycine Chelate on Oxidative Stress,Contents of Trace Elements,and Intestinal Morphology in Broilers 总被引:1,自引:0,他引:1
Wenqiang Ma Haihua Niu Jiang Feng Yong Wang Jie Feng 《Biological trace element research》2011,142(3):546-556
Three hundred and sixty healthy Ross × Ross 1-day-old broilers were used to study the effects of zinc glycine chelate (Zn-Gly)
on oxidative stress, contents of trace elements, and intestinal morphology. All broilers were randomly assigned to six treatment
groups, which replicates three times. Diets were as follows: (1) control (containing 29.3 mg zinc (Zn)/kg basic diet (0–21 days)
and 27.8 mg Zn/kg (22–42 days)); (2) basic diet plus 30 mg Zn/kg from Zn-Gly; (3) basic diet plus 60 mg Zn/kg from Zn-Gly;
(4) basic diet plus 90 mg Zn/kg from Zn-Gly; (5) basic diet plus 120 mg Zn/kg from Zn-Gly; and (6) positive control, basic
diet plus 120 mg Zn/kg from zinc sulfate (ZnSO4). The results showed that the addition of 90 or 120 mg/kg Zn-Gly led to an improvement of activity of Cu/Zn superoxide dismutase
and glutathione peroxidase and a reduction of malondialdehyde content in livers at 21 and 42 days. With 90 mg/kg Zn-Gly, the
content of sera zinc increased by 17.55% (P < 0.05) in 21-day broilers and 10.77% (P > 0.05) in 42-day broilers compared with that of the control. Adding 120 mg/kg Zn-Gly or ZnSO4 to broilers' diets greatly enhanced the content of zinc in feces at 21 days (P < 0.05) and at 42 days (P < 0.05). For 42-day chickens, increased villus height and decreased crypt depth of the jejunum could be observed in the second
growth stage of broilers fed with 90 mg/kg Zn-Gly. Also, intestinal wall thickness decreased (P < 0.05). In addition, adding 90 mg/kg Zn-Gly to the diet markedly elevated villus length of duodenum and decreased crypt
depth of ileum (P < 0.05) in 42-day broilers. 相似文献
17.
The purpose of this research was to assess the physicochemical properties of a controlled release formulation of recombinant
human growth hormone (rHGH) encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) composite microspheres. rHGH was loaded
in poly(acryloyl hydroxyethyl) starch (acHES) microparticles, and then the protein-containing microparticles were encapsulated
in the PLGA matrix by a solvent extraction/evaporation method. rHGH-loaded PLGA microspheres were also prepared using mannitol
without the starch hydrogel microparticle microspheres for comparison. The detection of secondary structure changes in protein
was investigated by using a Fourier Transfer Infrared (FTIR) technique. The composite microspheres were spherical in shape
(44.6±2.47 μm), and the PLGA-mannitol microspheres were 39.7±2.50 μm. Drug-loading efficiency varied from 93.2% to 104%. The
composite microspheres showed higher overall drug release than the PLGA/mannitol microspheres. FTIR analyses indicated good
stability and structural integrity of HGH localized in the microspheres. The PLGA-acHES composite microsphere system could
be useful for the controlled delivery of protein drugs. 相似文献
18.
O S Medvedev E R Martynova R S Akchurin V Iu Khalatov 《Biulleten' eksperimental'no? biologii i meditsiny》1987,103(1):8-10
The loss of radioactive microspheres (15 microns in diameter) from the rat myocardium was investigated during chronic experiment. Microspheres were injected to donor rats, the hearts were removed 20-30 min later and the number of microspheres trapped in the heart was determined on gamma-counter. After that the hearts were transplanted into the abdominal cavity of recipient rats using microsurgery technique. 5-24 days later the recipients were killed, the transplanted hearts were removed and radioactivity was measured again. It was shown that not more than 10% of microspheres were lost from the myocardium over a 5-24-day period, with the value of microsphere loss independent of the time period. 相似文献
19.
DNA encapsulation by an air-agitated, liquid-liquid mixer 总被引:1,自引:0,他引:1
Smooth and spherical alginate microspheres and nylon-membrane bound microcapsules were formed in an air-agitated, liquid-liquid mixer by emulsification/internal gelation and interfacial polymerization respectively. The mean diameter of the alginate microspheres ranged from 100 to 800 mum, and was controlled by process modifications. Increase in emulsifier concentration, gas flowrate, and emulsification time resulted in smaller microsphere size as did a decrease in liquid height. Increase in the dispersed phase viscosity resulted in a longer emulsification time required for approaching a minimum microsphere size. Microspheres could be formed with the proportion of dispersed phase approaching 30%. The yield of alginate microspheres was 70%, with losses attributed to incomplete recovery during washing and filtration operations. The yield of DNA encapsulation within the fraction of recovered microspheres, was 94%. The small loss was thought to occur by surface release during the washing of the microspheres. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 464-470, 1997. 相似文献
20.
An objective of the present investigation was to prepare and evaluate Eudragit-coated pectin microspheres for colon targeting
of 5-fluorouracil (FU). Pectin microspheres were prepared by emulsion dehydration method using different ratios of FU and
pectin (1:3 to 1:6), stirring speeds (500–2000 rpm) and emulsifier concentrations (0.75%–1.5% wt/vol). The yield of preparation
and the encapsulation efficiencies were high for all pectin microspheres. Microspheres prepared by using drug:polymer ratio
1:4, stirring speed 1000 rpm, and 1.25% wt/vol concentration of emulsifying agent were selected as an optimized formulation.
Eudragit-coating of pectin microspheres was performed by oil-in-oil solvent evaporation method using coat: core ratio (5:1).
Pectin microspheres and Eudragit-coated pectin microspheres were evaluated for surface morphology, particle size and size
distribution, swellability, percentage drug entrapment, and in vitro drug release in simulated gastrointestinal fluids (SGF).
The in vitro drug release study of optimized formulation was also performed in simulated colonic fluid in the presence of
2% rat cecal content. Organ distribution study in albino rats was performed to establish the targeting potential of optimized
formulation in the colon. The release profile of FU from Eudragit-coated pectin microspheres was pH dependent. In acidic medium,
the release rate was much slower; however, the drug was released quickly at pH 7.4. It is concluded from the present investigation
that Eudragit-coated pectin microspheres are promising controlled release carriers for colon-targeted delivery of FU.
Published: February 16, 2007 相似文献