• YAKHAK HOEJI
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• v.45 no.6
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• pp.623-633
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• 2001

Various bupivacaine-loaded microspheres were prepared using poly(d,1-lactide) (PLA) and poly(d,1-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. The effects of process conditions such as drug loading, polymer type and solvent type on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency and yield of PLGA micro- spheres were higher than those of PLA microspheres. The prepared microspheres had an average particle size below 5${\mu}{\textrm}{m}$. The particle size range of microspheres was 1.65~2.24${\mu}{\textrm}{m}$. As a result of SEM, the particle size of PLA microspheres was smaller than that of PLGA microspheres. In morphology studies, microspheres showed a spherical shape and smooth surface in all process conditions. In thermal analysis, bupivacaine-loaded microspheres showed no peaks originating from bupivacaine. This suggested that bupivacaine base was molecular-dispersed in the polymer matrix of microspheres. The release pattern of the drug from microspheres was evaluated for 96 hours. The initial burst release of bupivacaine base decreased with increasing the molecular weight of PLGA, and the drug from microspheres released slowly. In conclusion, bupivacaine-loaded microspheres were successfully prepared from poly(d,1-lactide) and poly (d,1- lactic-co-glycolide) polymers with different molecular weights allowing control of the release rate.

• Polymer(Korea)
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• v.29 no.1
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• pp.69-73
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• 2005

To overcome the main disadvantages of non-viral gene delivery systems such as repeated administration due to the low transfection efficiency, poly(D,L-lactide-co-glycolide) was applied to encapsulate pDNA in its microsphere formulation. Free pDNA or various ratios (w/w) of chitosan/pDNA complexes was used for encapsulation, with the resulting encapsulation efficiency of 44%, 5%, and 8% for free pDNA, 0.7:1 and 1:1 ratios, respectively. Scanning electron micrographs of poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres encapsulating pDNA or chitosan-condensed pDNA revealed a smooth spherical shape immediately after microsphere preparation and a collapsed porous shape in 41 days due to the degradation of PLGA. In vitro release profile showed that the 0.7:1 (w/w) ratio formulation exerted 47% release in 26 days, whereas free pDNA or 1:1 (w/w) ratio formulation did only 15% or 32%, respectively.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.36-43
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• 2020

A biliant stent was fabricated using a magnesium alloy wire, a biodegradable metal. In order to control the fast decomposition and corrosion of magnesium alloys in vivo, magnesium alloy wires were coated with biodegradable polymers such as polycaprolactone (PCL), poly(propylene carbonate) (PPC), poly (L-lactic acid) (PLLA), and poly (D, L-lactide-co-glycolide) (PLGA). In the case of PPC, which is a surface erosion polymer, there is no crack or peeling compared to other polymers (PCL, PLLA, and PLGA) that exhibit bulk erosion behavior. Also, the effect of biodegradable polymer coating on the axial force, which is the mechanical property of magnesium alloy stents, was investigated. Stents coated with most biodegradable polymers (PCL, PLLA, PLGA) increased axial forces compared to the uncoated stent, reducing the flexibility of the stent. However, the stent coated with PPC showed the axial force similar to uncoated stent, which did not reduce the flexibility. From the above results, PPC is considered to be the most efficient biodegradable polymer.

• YAKHAK HOEJI
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• v.44 no.6
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• pp.511-520
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• 2000

Various bupivacaine-loaded microspheres were prepared from poly (d,l-lactide) (PLA) or poly (d,l-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. PLA and PLGA microspheres were prepared by w/o/w and w/o/o multiple emulsion solvent evaporation, respectively. The effects of process conditions such as emulsification speed, emulsifier type, emulsifier concentration and internal/external phase ratio on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency was higher in the microspheres prepared by w/o/o multiple emulsion than that by w/o/w multiple emulsion method, because the solubility of bupivacaine HCI was decreased in oil phase compared with water phase. The prepared microspheres had an average diameter between 1 and $2\;{\mu}M$ in all conditions of two methods. In morphology studies the PLA microspheres showed an irregular shape and smooth surface, but PLGA microspheres had a spherical shape and smooth surface. The release pattern of the drug from microspheres was evaluated on the basis of the burst effect and the extent of the release after 24h. The in vitro release of bupivacaine HCl from microspheres showed a large initial burst release and $60{\sim}80%$ release within one day in all conditions of two methods. The extents of the burst release against PLA and PLGA microspheres were $30{\sim}50%$ and $50{\sim}80%$ within 20min, respectively. This burst release seems to be due to the smaller size of microspheres and the solubility of drug in water.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2342-2348
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• 2014

Poly(lactic-co-glycolic acid) (PLGA) were grafted to both ends of Pluronic$^{(R)}$ F68 ($(EO)_{75}(PO)_{30}(EO)_{75}$) triblock copolymer to produce poly{(lactic acid)$_m$-co-(glycolic acid)$_n$}-b-poly(ethylene oxide)$_{75}$-b-poly(propylene oxide)$_{30}$-b-poly(ethylene oxide)$_{75}$-b-poly{(lactic acid)$_m$-co-(glycolic acid)$_n$} (PLGA-F68-PLGA) pentablock copolymers. Molecular weights of PLGA blocks were controlled and five kinds of pentablock copolymers with different PLGA block lengths were synthesized using in-situ ring-opening polymerization of D,L-lactide and glycolide with tin(II) 2-ethylhexanoate ($Sn(Oct)_2$) catalyst. PLGA-F68-PLGA pentablock copolymers were characterized by $^1H$- and $^{13}C$-NMR, GPC, and TGA. The numbers (2m, 2n) of repeating units for lactic acid and glycolic acid inside PLGA segments were obtained as (48, 17), (90, 23), (125, 40), (180, 59), and (246, 64), with $^1H$-NMR measurement. From NMR data, the resultant molecular weights were determined in the range of 12,700-29,700, which were similar to those obtained from GPC. Polydispersity index was increased in the range of 1.32-1.91 as the content of PLGA blocks increased. TG and DTG thermograms showed discrete degradation traces for PLGA and F68 blocks, which indicate the weight fractions of PLGA blocks in pentablock copolymers can be calculated by TG profile and it is possible to remove PLGA block selectively. Hydrodynamic radius and radius of gyration of pentablock copolymer micelle were obtained in the range of 46-68 nm and 31-49 nm, respectively, in very dilute (i.e. 0.005 wt %) aqueous solution of THF:$H_2O$ = 10:90 by volume at $25^{\circ}C$.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.9
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• pp.3753-3758
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• 2015

Background: Polymeric nanoparticles are attractive materials that have been widely used in medicine for drug delivery, with therapeutic applications. In our study, polymeric nanoparticles and the anticancer drug, chrysin, were encapsulated into poly (D, L-lactic-co-glycolic acid) poly (ethylene glycol) (PLGA-PEG) nanoparticles for local treatment. Materials and Methods: PLGA: PEG triblock copolymers were synthesized by ring-opening polymerization of D, L-lactide and glycolide as an initiator. The bulk properties of these copolymers were characterized using 1H nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. In addition, the resulting particles were characterized by scanning electron microscopy. Results: The chrysin encapsulation efficiency achieved for polymeric nanoparticles was 70% control of release kinetics. The cytotoxicity of different concentration of pure chrysin and chrysin loaded in PLGA-PEG ($5-640{\mu}M$) on T47-D breast cancer cell line was analyzed by MTT-assay. Conclusions: There is potential for use of these nanoparticles for biomedical applications. Future work should include in vivo investigation of the targeting capability and effectiveness of these nanoparticles in the treatment of breast cancer.