Synthesis, characterisation and drug release properties of microspheres of polystyrene with aliphatic polyester side-chains.

A series of graft copolymers consisting of polystyrene backbone with biocompatible side chains based on (co)polymers of l-lactic acid and glycolic acid were synthesised by combination two controlled polymerisations, namely, nitroxide mediated radical polymerisation (NMRP) and ring opening polymerisation (ROP) with "Click" chemistry. The main goal of this work was to design new biodegradable microspheres using obtained graft copolymers for long-term sustained release of imatinib mesylate (IMM) as a model drug. The IMM loaded microspheres of the graft copolymers, polystyrene-g-poly(lactide-co-glycolide) (PS-g-PLLGA), polystyrene-g-poly(lactic acid) (PS-g-PLLA) and poly(lactic-coglycolic acid) (PLLGA) were then prepared by a modified water-in-oil-in-water (w1/o/w2) double emulsion/solvent evaporation technique. The optimised microspheres were characterised by particle size, encapsulation efficiency, and surface morphology also; their degradation and release properties were studied in vitro. The degradation studies of three different types of microspheres showed that the PS backbone of the graft copolymers slows down the degradation rate compared to PLLGA.

Controlled release of imatinib mesylate from PLGA microspheres inhibit craniopharyngioma mediated angiogenesis.

Poly(lactic-co-glycolic acid) microspheres loaded with imatinib mesylate has been developed as a new therapeutic strategy to prevent craniopharyngioma recurrence. Microspheres composed of different lactic/glycolic acid ratios, molecular weights and drug compositions were synthesized and loaded with imatinib mesylate by modified double-emulsion/solvent evaporation technique and subsequently characterized by particle-size distribution, scanning electron microscopy, encapsulation efficiency and in vitro drug release. Inhibitory potential of imatinib containing microspheres on tumor neovascularization was investigated on craniopharyngioma tumor samples by rat cornea angiogenesis assay. Results showed that microspheres in different LA:GA ratios [LA:GA 50:50 (G50), 75:25 (G25), 85:15 (G15)] considerably reduced neovascularization induced by recurrent tumor samples in an in vivo angiogenesis assay (P < 0.01). Our data indicate that local delivery of imatinib mesylate to the post-surgical tumoral cavity using biodegradable microspheres may be a promising biologically selective approach to prevent the recurrence of craniopharyngiomas, via inhibition of neovascularization.

Preparation and in vitro characterization of vascular endothelial growth factor (VEGF)-loaded poly(D,L-lactic-co-glycolic acid) microspheres using a double emulsion/solvent evaporation technique.

Biodegradable Poly(lactic-co-glycolic acid; PLGA), microspheres encapsulating the angiogenic protein recombinant human vascular endothelial growth factor (rhVEGF) were formed to achieve VEGF release in a sustained manner. These microspheres are a promising delivery system which can be used for therapeutic angiogenesis. The PLGA microspheres incorporating two different initial loading amounts of rhVEGF have been prepared by a modified water-in-oil-in-water (w/o/w) double emulsion/solvent evaporation technique. The microspheres have been characterized by particle size distribution, environmental scanning electron microscopy (ESEM), light microscopy, encapsulation efficiency and their degradation was studied in vitro. The rhVEGF released from microspheres was quantified by the competitive enzyme-linked immunosorbent assay (ELISA) and human umbilical vein endothelial cell (HUVEC) proliferation assay was used to assess biological activity of the released VEGF. The microspheres were spherical with diameters of 10-60 µm and the encapsulation efficiency was between 46% and 60%. The release kinetics of rhVEGF was studied for two different amounts: 5 µg VEGF (V5) and 50 µg VEGF (V50) per 500 mg starting polymer. The total protein (VEGF:BSA) release increased up to 4 weeks for two rhVEGF concentrations. The ELISA results showed that the burst release for V5 and V50 microspheres were 4 and 27 ng/mL, respectively. For V5, the microspheres showed an initial burst release, followed by a higher steady-state release until 14 days. VEGF release increased up to 2 weeks for V50 microsphere. HUVEC proliferation assay showed that endothelial cells responded to bioactive VEGF by proliferating and migrating.

Synthesis and characterization of poly(L-lactic acid-co-ethylene oxide-co-aspartic acid) and its interaction with cells.

Multiblock terpolymer of poly(L-lactic acid)/poly(ethylene oxide)/poly(L-aspartic acid), (PLLA/PEO/PAsp) was synthesized by ring opening polymerization of beta -benzyl L-aspartate N-carboxyanhydride, Asp(OBzl)-NCA with alpha-omega -hydroxy terminated triblock PLLA/PEO/PLLA copolymer. The resulting multiblock terpolymer was characterized by several techniques including Fourier transform infrared spectroscopy and differential scanning calorimetry.(1)H nuclear magnetic resonance spectra indicated the molar ratio of PLLA/PEO/PAsp (OBzl) to be 86/10/4. Thermal gravimetric analysis and environmental scanning electron microscopy data showed that PLLA/PEO/PAsp had crystalline and brittle structure. In order to improve its mechanical and physical properties, the terpolymer was blended with high molecular weight poly(L-lactic-co-glycolic acid) copolymer, PLGA(85/15) (M(w): 95000 gmol(-1)) in 25/75 and 50/50 mole ratios. The hydrolytical degradation properties of these polymers were studied. Degradation experiments were performed during a 48-day period in pH:7.4 phosphate-buffered saline (PBS) at 37 degrees C. The observed molecular weight losses were 91% and 67% for the 25/75 and 50/50 mixtures, respectively. In vitro attachment and growth of L929 mouse fibroblasts on these biopolymers were also investigated. Cell growth experiments indicated that the copolymer blend allowed the attachment and growth of cells.

Isolation and culture of adult and fetal rabbit bladder smooth muscle cells and their interaction with biopolymers.

PURPOSE: The aim of this study was to test the feasibility of isolation and culture of adult and fetal rabbit bladder smooth muscle cells (SMCs) and comparison of their interactions with different types of biodegradable biopolymers in cell culture. METHODS: Bladder SMCs isolated from adult and fetus rabbits were identified by immunostaining for smooth muscle alpha-actin and myosin. Growth kinetics of SMCs were estimated using population doubling time (PDT) and thymidine labeling index (TLI). Poly (D, L-lactide-co-glycolide; PLGA) copolymers were synthesized at 85:15 and 75:25 monomer ratios. The porous scaffolds prepared from these polymers were seeded with SMCs. The study compared the effectiveness of adsorbing fibronectin and fetal calf serum (FCS) on these biopolymers. The cells grown on these polymers were quantified using a neutral red uptake assay. RESULTS: Over 90% of the 2 cell populations stained positive for SMC marker proteins. Fetal SMCs were seen to emerge from the tissue after 3 to 4 days, whereas adult SMCs were seen after 5 to 6 days. However, estimated PDT of fetal and adult SMCs was 85.2 and 54.5 hours, respectively, and TLI of adult SMCs was also higher than with fetal SMCs. Proliferation on 75:25 PLGA was better than for 85:15 and for both biopolymers; adsorption of FCS significantly affected cell attachment relative to fibronectin. CONCLUSIONS: Although fetal SMCs were shown to emerge from explants early after seeding onto dishes, doubling time and S-phase fraction of adult bladder SMCs were markedly higher than of fetal derived cells. Adsorption of serum proteins significantly enhances the attachment of both fetal and adult SMCs to biopolymers.

Synthesis and characterization of glycolide, L-lactide, and PDMS-based terpolymers as a support for cell cultures.

Poly(lactic acid)/poly(glycolic acid)/poly(dimethylsiloxane) (PLGA/TEGOMER) terpolymers have been synthesized by the ring-opening polymerization of L-lactide and glycolide with alpha,omega-amine-terminated poly(dimethylsiloxane) prepolymer, using stannous octoate as a catalyst. The resulting terpolymers were characterized by various analytical techniques including size exclusion chromatography, 1H-nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy, and differential scanning calorimetry. The data showed that the terpolymers presented an amorphous structure. The glass transition temperature decreased with increasing TEGOMER unit content. For in vitro degradation studies, porous films were fabricated using a solvent-casting, particulate leaching technique. Degradation of the PLGA/TEGOMER terpolymer was studied in phosphate-buffered saline at pH 7.4 and 37 degrees C. The degradation was followed by intrinsic viscosity, mass loss, and molecular weight measurements, and 1H-NMR spectroscopy. The mass loss after 55 days was 76% for the PLGA/TEGOMER (71/24/5) sample. Cell growth experiments using Swiss 3T3 fibroblasts demonstrated that PLGA/TEGOMER terpolymer matrices allow the attachment and growth of cells.