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1.
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
2.
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
3.
Influence of selected formulation variables on the preparation of enzyme-entrapped eudragit S100 microspheres 总被引:1,自引:0,他引:1
The aim of this work is to study the influence of formulation parameters in the preparation of sustained release enzyme-loaded Eudragit S100 microspheres by emulsion solvent diffusion technique. A 3(2) full factorial experiment was designed to study the effects of the amount of solvent (dichloromethane) and stabilizers (Tween 20, 40, or 80) on the drug content and microsphere size. The results of analysis of variance test for both effects indicated that the test is significant. The effect of amount of stabilizer was found to be higher on both responses (SS(Y1) = 45.60; SS(Y2) = 737.93), whereas solvent concentration comparatively produced significant effect on the size of microspheres (SS(Y1) = 0.81; SS(Y2) = 358.83). Scanning electron microscopy of microspheres with maximum drug content (2.5 mL dichloromethane and 0.1 mL Tween 80) demonstrated smooth surface spherical particles with mean diameter of 56.83 +/- 2.88 microm. The effect of formulation variables on the integrity of enzyme was confirmed by in vitro proteolytic activity. The enteric nature of microspheres was evaluated and results demonstrated ~6% to 7% release of enzyme in acidic medium. The release of enzyme from microspheres followed Higuchi kinetics. In phosphate buffer, microspheres showed an initial burst release of 20.34% +/- 2.35% in 1 hour with additional 58.79% +/- 4.32% release in the next 5 hours. Three dimensional response graphs were presented to visualize the effect of independent variables on the chosen response. Thus, Eudragit S100 microspheres can be successfully prepared for oral delivery of enzymes with desirable characters in terms of maximum loading and diffusion release pattern. 相似文献
4.
The purpose of this research was to prepare floating microspheres consisting of (1) calcium silicate as porous carrier; (2)
orlistat, an oral anti-obesity agent; and (3) Eudragit S as polymer, by solvent evaporation method and to evaluate their gastro-retentive
and controlled-release properties. The effect of various formulation and process variables on the particle morphology, micromeritic
properties, in vitro floating behavior, percentage drug entrapment, and in vitro drug release was studied. The gamma scintigraphy
of the optimized formulation was performed in albino rabbits to monitor the transit of floating microspheres in the gastrointestinal
tract. The orlistat-loaded optimized formulation was orally administered to albino rabbits, and blood samples collected were
used to determine pharmacokinetic parameters of orlistat from floating microspheres. The microspheres were found to be regular
in sphae and highly porous. Microsphere formulation CS4, containing 200 mg calcium silicate, showed the best floating ability
(88%±4% buoyancy) in simulated gastric fluid as compared with other formulations. Release pattern of orlistat in simulated
gastric fluid from all floating microspheres followed Higuchi matrix model and Peppas-Korsmeyer model. Prolonged gastric residence
time of over 6 hours was achieved in all rabbits for calcium silicate-based floating microspheres of orlistat. The enhanced
elimination half-life observed after pharmacokinetic investigations in the present study is due to the floating nature of
the designed formulations. 相似文献
5.
The objective of this research was to optimize the processing parameters for poly(D,L-lactide-coglycolide) (PLGA) microspheres
of 5-fluorouracil (5-FU) and to mathematically relate the process parameters and properties of microspheres. Microspheres
were prepared by a water-in-oil-in-water emulsion solvent evaporation technique. A 32 factorial design was employed to study the effect of the volume of the internal phase of the primary emulsion and the volume
of the external phase of the secondary emulsion on yield, particle size, and encapsulation efficiency of microspheres. An
increase in the volume of the internal phase of the primary emulsion resulted in a decrease in yield and encapsulation efficiency
and an increase in particle size of microspheres. When the volume of the external phase of the secondary emulsion was increased,
a decrease in yield, particle size, and encapsulation efficiency was observed. Microspheres with good batch-to-batch reproducibility
could be produced. Scanning electron microscopic study indicated that microspheres existed as aggregates. 相似文献
6.
In this study, ethylcellulose (EC)-based microsphere formulations were prepared without and with triethyl citrate (TEC) content
of 10% and 30% by water-in-oil emulsion-solvent evaporation technique. Diltiazem hydrochloride (DH) was chosen as a hydrophilic
model drug and used at different drug/polymer ratios in the microspheres. The aim of the work was to evaluate the influence
of plasticizer ratio on the drug release rate and physicochemical characteristics of EC-based matrix-type microspheres. The
resulting microspheres were evaluated for encapsulation efficiency, particle size and size distribution, surface morphology,
total pore volume, thermal characteristics, drug release rates, and release mechanism. Results indicated that the physicochemical
properties of microspheres were strongly affected by the drug/polymer ratio investigated and the concentration of TEC used
in the production technique. The surface morphology and pore volume of microspheres significantly varied based on the plasticizer
content in the formulation. DH release rate from EC-based matrix-type microspheres can be controlled by varying the DH to
polymer and plasticizer ratios. Glass transition temperature values tended to decrease in conjunction with increasing amounts
of TEC. Consequently, the various characteristics of the EC microspheres could be modified based on the plasticized ratio
of TEC. 相似文献
7.
The objective of this research was to optimize the formulation factors and evaluate the release profiles of ε -polycaprolactone microparticles containing rhamnolipid biosurfactant (RhBS). Microparticles were prepared by a water-in-oil-in-water emulsion solvent evaporation technique. Optimization was studied through the effects of the volumes and concentrations of the internal and external phases of the microparticles on percent yield, particle size, encapsulation efficiency, and biosurfactant loading. Manipulation of the formulation factors yielded microparticles that were statistically the same size and generally classified as small. An increase in the volume of the internal phase above 1 ml caused a general decrease in yield and encapsulation efficiency and an increase in biosurfactant loading. When the volume of the external phase increased above 50 ml, decreases in percent yield and encapsulation efficiency and increases in biosurfactant loading were observed. Formulations with the highest encapsulation efficiencies and percentage yield and the lowest biosurfactant loading efficiencies were selected for further evaluation in release studies. Release studies were conducted in 15 and 32 ppt artificial seawater and deionized water. After 30 days microparticle formulations gradually released 80% to 100% of the encapsulated RhBS in all release media, with no significant differences in release rates in the different release media. 相似文献
8.
The purpose of this investigation was to prepare and evaluate the colon-specific microspheres of 5-fluorouracil for the treatment
of colon cancer. Core microspheres of alginate were prepared by the modified emulsification method in liquid paraffin and
by cross-linking with calcium chloride. The core microspheres were coated with Eudragit S-100 by the solvent evaporation technique
to prevent drug release in the stomach and small intestine. The microspheres were characterized by shape, size, surface morphology,
size distribution, incorporation efficiency, and in vitro drug release studies. The outer surfaces of the core and coated
microspheres, which were spherical in shape, were rough and smooth, respectively. The size of the core microspheres ranged
from 22 to 55 μm, and the size of the coated microspheres ranged from 103 to 185 μm. The core microspheres sustained the drug
release for 10 hours. The release studies of coated microspheres were performed in a pH progression medium mimicking the conditions
of the gastrointestinal tract. Release was sustained for up to 20 hours in formulations with core microspheres to a Eudragit
S-100 coat ratio of 1∶7, and there were no changes in the size, shape, drug content, differential scanning calorimetry thermogram,
and in vitro drug release after storage at 40°C/75% relative humidity for 6 months. 相似文献
9.
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
10.
Temperature-sensitive diblock copolymers, poly(N-isopropylacrylamide)-b-poly(D,L-lactide) (PNIPAAm-b-PLA) with different PNIPAAm contents were synthesized and utilized to fabricate microspheres containing bovine serum albumin (BSA, as a model protein) by a water-in-oil-in-water double emulsion solvent evaporation process. XPS analysis showed that PNIPAAm was a dominant component of the microspheres surface. BSA was well entrapped within the microspheres, and more than 90% encapsulation efficiency was achieved. The in vitro degradation behavior of microspheres was investigated using SEM, NMR, FTIR, and GPC. It was found that the microspheres were erodible, and polymer degradation occurred in the PLA block. Degradation of PLA was completed after 5 months incubation in PBS (pH 7.4) at 37 degrees C. A PVA concentration of 0.2% (w/v) in the internal aqueous phase yielded the microspheres with an interconnected porous structure, resulting in fast matrix erosion and sustained BSA release. However, 0.05% PVA produced the microspheres with a multivesicular internal structure wrapped with a dense skin layer, resulting in lower erosion rate and a biphasic release pattern of BSA that was characterized with an initial burst followed by a nonrelease phase. The microspheres made from PNIPAAm-b-PLA with a higher portion of PNIPAAm provided faster BSA release. In addition, BSA release from the microspheres responded to the external temperature changes. BSA release was slower at 37 degrees C (above the LCST) than at a temperature below the LCST. The microspheres fabricated with PNIPAAm-b-PLA having a 1:5 molar ratio of PNIPAAm to PLA and 0.2% (w/v) PVA in the internal aqueous phase provided a sustained release of BSA over 3 weeks in PBS (pH 7.4) at 37 degrees C. 相似文献
11.
Psoriasis is a chronic, autoimmune skin disease affecting approximately 2% of the world's population. Clobetasol propionate
which is a superpotent topical corticosteroid is widely used for topical treatment of psoriasis. Conventional dosage forms
like creams and ointments are commonly prefered for the therapy. The purpose of this study was to develop a new topical delivery
system in order to provide the prolonged release of clobetasol propionate and to reduce systemic absorption and side effects
of the drug. Clobetasol propionate loaded-poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres were prepared by oil-in-water
emulsion–solvent evaporation technique. Particle size analysis, morphological characterization, DSC and XRD analyses and in vitro drug release studies were performed on the microparticle formulations. Emulgel formulations were prepared as an alternative
for topical delivery of clobetasol propionate. In vitro drug release studies were carried out from the emulgel formulations containing pure drug and drug-loaded microspheres. In
addition, the same studies were performed to determine the drug release from the commercial cream product of clobetasol propionate.
The release of clobetasol propionate from the emulgel formulations was significantly higher than the commercial product. In
addition, the encapsulation of clobetasol propionate in the PLGA microspheres significantly delayed the drug release from
the emulgel formulation. As a result, the decrease in the side effects of clobetasol propionate by the formulation containing
PLGA microspheres is expected. 相似文献
12.
The system poly(lactic-co-glycolic) acid/ piroxicam (PLGA/PX) was selected, as a model system, to evaluate the effectiveness of supercritical carbon dioxide (SC-CO(2)) extraction of the oily phase (ethyl acetate) from oil-in-water emulsions used in the production of polymer/drug microspheres for sustained drug release applications. The influence of process parameters like operating pressure and temperature, flow rate and contacting time between the emulsion and SC-CO(2) was studied with respect to the microsphere size, distribution and solvent residue. Different polymer concentrations in the oily phase were also tested in emulsions formulation to monitor their effects on droplets and microspheres size distribution at fixed mixing conditions. Spherical PLGA microspheres loaded with PX (10% w/w) with mean sizes ranging between 1 and 3 microm and very narrow size distributions were obtained due to the short supercritical processing time (30 min) that prevents the aggregation phenomena typically occurring during conventional solvent evaporation process. A solvent residue smaller than 40 ppm was also obtained at optimized operating conditions. DSC and SEM-EDX analyses confirmed that the produced microparticles are formed by a solid solution of PLGA and PX and that the drug is entrapped in an amorphous state into the polymeric matrix with an encapsulation efficiency in the range of 90-95%. Drug release rate studies showed very uniform drug concentration profiles, without any burst effect, confirming a good dispersion of the drug into the polymer particles. 相似文献
13.
The aim of this study was to formulate and characterize a microparticulate system of progestin-only contraceptive. Another
objective was to evaluate the effect of gamma radio-sterilization on in vitro and in vivo drug release characteristics. Levonorgestrel (LNG) microspheres were fabricated using poly(lactide-co-glycolide) (PLGA) by a novel solvent evaporation technique. The formulation was optimized for drug/polymer ratio, emulsifier
concentration, and process variables like speed of agitation and evaporation method. The drug to polymer ratio of 1:5 gave
the optimum encapsulation efficiency. Speed of agitation influenced the spherical shape of the microparticles, lower speeds
yielding less spherical particles. The speed did not have a significant influence on the drug payloads. A combination of stabilizers
viz. methyl cellulose and poly vinyl alcohol with in-water solvent evaporation technique yielded microparticles without any free
drug crystals on the surface. This aspect significantly eliminated the in vitro dissolution “burst effect”. The residual solvent content was well within the regulatory limits. The microparticles passed
the test for sterility and absence of pyrogens. In vitro dissolution conducted on the product before and after gamma radiation sterilization at 2.5 Mrad indicated no significant
difference in the drug release patterns. The drug release followed zero-order kinetics in both static and agitation conditions
of dissolution testing. The in vivo studies conducted in rabbits exhibited LNG release up to 1 month duration with drug levels maintained within the effective
therapeutic window. 相似文献
14.
Hydroxyzine HCl is used in oral formulations for the treatment of urticaria and atopic dermatitis. Dizziness, blurred vision,
and anticholinergic responses, represent the most common side effects. It has been shown that controlled release of the drug
from a delivery system to the skin could reduce the side effects while reducing percutaneous absorption. Therefore, the aim
of the present study was to produce an effective drug-loaded dosage form that is able to control the release of hydroxyzine
hydrochloride into the skin. The Microsponge Delivery System is a unique technology for the controlled release of topical
agents, and it consists of porous polymeric microspheres, typically 10–50 μm in diameter, loaded with active agents. Eudragit
RS-100 microsponges of the drug were prepared by the oil in an oil emulsion solvent diffusion method using acetone as dispersing
solvent and liquid paraffin as the continuous medium. Magnesium stearate was added to the dispersed phase to prevent flocculation
of Eudragit RS-100 microsponges. Pore inducers such as sucrose and pregelatinized starch were used to enhance the rate of
drug release. Microsponges of nearly 98% encapsulation efficiency and 60–70% porosity were produced. The pharmacodynamic effect
of the chosen preparation was tested on the shaved back of histamine-sensitized rabbits. Histopathological studies were driven
for the detection of the healing of inflamed tissues. 相似文献
15.
Christianne Mounir Zaki Rizkalla Randa latif Aziz Iman Ibrahim Soliman 《AAPS PharmSciTech》2011,12(3)
Hydroxyzine HCl is used in oral formulations for the treatment of urticaria and atopic dermatitis. Dizziness, blurred vision, and anticholinergic responses, represent the most common side effects. It has been shown that controlled release of the drug from a delivery system to the skin could reduce the side effects while reducing percutaneous absorption. Therefore, the aim of the present study was to produce an effective drug-loaded dosage form that is able to control the release of hydroxyzine hydrochloride into the skin. The Microsponge Delivery System is a unique technology for the controlled release of topical agents, and it consists of porous polymeric microspheres, typically 10–50 μm in diameter, loaded with active agents. Eudragit RS-100 microsponges of the drug were prepared by the oil in an oil emulsion solvent diffusion method using acetone as dispersing solvent and liquid paraffin as the continuous medium. Magnesium stearate was added to the dispersed phase to prevent flocculation of Eudragit RS-100 microsponges. Pore inducers such as sucrose and pregelatinized starch were used to enhance the rate of drug release. Microsponges of nearly 98% encapsulation efficiency and 60–70% porosity were produced. The pharmacodynamic effect of the chosen preparation was tested on the shaved back of histamine-sensitized rabbits. Histopathological studies were driven for the detection of the healing of inflamed tissues.KEYWORDS: hydroxyzine HCl, microsponges, oil in oil emulsion solvent diffusion, skin delivery 相似文献
16.
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
17.
Studies on Mefenamic Acid Microparticles: Formulation, In Vitro Release, and In Situ Studies in Rats
Ferhan Sevgi Aysu Yurdasiper Buket Kaynarsoy Ezgi Turunç Tamer Güneri Ayfer Yalçın 《AAPS PharmSciTech》2009,10(1):104-112
In this study, we investigated the in vitro characteristics of mefenamic acid (MA) microparticles as well as their effects on DNA damage. MA-loaded chitosan and alginate
beads were prepared by the ionotropic gelation process. Microsponges containing MA and Eudragit RS 100 were prepared by quasi-emulsion
solvent diffusion method. The microparticles were characterized in terms of particle size, surface morphology, encapsulation
efficiency, and in vitro release profiles. Most of the formulation variables manifested an influence on the physical characteristics of the microparticles
at varying degrees. We also studied the effects of MA, MA-loaded microparticles, and three different polymers on rat brain
cortex DNA damage. Our results showed that DNA damage was higher in MA-loaded Eudragit microsponges than MA-loaded biodegradable
chitosan or alginate microparticles. 相似文献
18.
K. Karthikeyan Ezhilarasan Vijayalakshmi Purna Sai Korrapati 《AAPS PharmSciTech》2014,15(5):1172-1180
In this study, we have evaluated the interactions of zein microspheres with different class of drugs (hydrophobic, hydrophilic, and amphiphilic) using in vitro and in silico analysis. Zein microspheres loaded with aceclofenac, metformin, and promethazine has been developed by solvent evaporation technique and analyzed for its compatibility. The physical characterization depicted the proper encapsulation of hydrophobic drug in the microspheres. The in vitro release study revealed the sustaining ability of the microspheres in the following order: hydrophobic > hydrophilic > amphiphilic. In silico analysis also confirmed the better binding affinity and greater interactions of hydrophobic drug with zein. The above results revealed that zein is more suitable for hydrophobic drugs in the development of sustained drug delivery systems using solvent evaporation technique. The study therefore envisages a scope for identifying the most suitable polymer for a sustained drug delivery system in accordance with the nature of the drug.KEY WORDS: hydrophilic drugs, hydrophobic drugs, in silico analysis, protein-drug interactions, solvent evaporation, zein microspheres 相似文献
19.
Kassab R Parrot-Lopez H Fessi H Menaucourt J Bonaly R Coulon J 《Bioorganic & medicinal chemistry》2002,10(6):1767-1775
In an effort to develop a new way of drug delivery, especially for polyenic antifungal molecules, we have incorporated amphotericin B (AmB) into biodegradable galactosylated poly (L-lactic acid) (L-PLA) and poly (L-lactic-co-glycolic acid) (PLGA) microspheres. These drug carriers were prepared by solvent evaporation using an oil/water (o/w) emulsion. The ratio of galactosyl spacers with different chain lengths was 1.74-2.78%. The maximal quantity of AmB encapsulated reported to 100 mg of the galactosylated microspheres was 7.14 mg for L-PLA (encapsulation rate 45% of mole) and 6.42 mg for PLGA derivatives (encapsulation rate 81% of mole). In our yeast model, drug release depended on three factors: (i) presence of galactosylated antennae, (ii) length of galactosyl antenna and (iii) nature of the polymer. More of the AmB trapped in PLGA microspheres was released than from PLA microspheres. These novel functionalised microspheres could be required for the delivering of therapeutic agents according to their recognition to specific cells. 相似文献
20.
The aim of this study was to prepare biodegradable sustained release magnetite microspheres sized between 1 to 2 μm. The microspheres with or without magnetic materials were prepared by a W/O/W double emulsion solvent evaporation technique using poly(lactide-co-glycolide) (PLGA) as the biodegradable matrix forming polymer. Effects of manufacturing and formulation variables on particle size were investigated with non-magnetic microspheres. Microsphere size could be controlled by modification of homogenization speed, PLGA concentration in the oil phase, oil phase volume, solvent composition, and polyvinyl alcohol (PVA) concentration in the outer water phase. Most influential were the agitation velocity and all parameters that influence the kinematic viscosity of oil and outer water phase, specifically the type and concentration of the oil phase. The magnetic component yielding homogeneous magnetic microspheres consisted of magnetite nanoparticles of 8 nm diameter stabilized with a polyethylene glycole/polyacrylic acid (PEG/PAA) coating and a saturation magnetization of 47.8 emu/g. Non-magnetic and magnetic microspheres had very similar size, morphology, and size distribution, as shown by scanning electron microscopy. The optimized conditions yielded microspheres with 13.7 weight% of magnetite and an average diameter of 1.37 μm. Such biodegradable magnetic microspheres seem appropriate for vascular administration followed by magnetic drug targeting. 相似文献