Poly(L,L-lactide) and poly(L,L-lactide-co-glycolide) microparticles by dialysis

Abstract

Formation of poly(L,L-lactide) (PLLA) and poly(D,L-lactide-co-glycolide) (PLGA) microparticles by dialysis from 1,4-dioxane, tetrahydrofuran (THF), acetonitrile, dimethyl sulfoxide (DMSO), and dimethylformamide (DMF) against water has been investigated. In some instances microparticles were obtained from a mixture of the above-mentioned polyesters and PLLA-block-polyglycidol-blockpoly(ethylene oxide) triblock copolymer containing a hydrophobic PLLA block as well as hydrophilic polyglycidol and poly(ethylene oxide) blocks, the former with functional -OH groups. The effects of the nature of polyester, solvent and concentration of triblock copolymer on particles morphology, size, size distribution, and degree of crystallinity have been determined. Dialysis of PLGA yielded particles in the form of microspheres regardless of the solvent. Diameters of these particles were in the range of 0.36 -1.77 µm and particles' diameter polydispersity ( D ) varied from 1.37 to 2.04, depending on the solvent. In the case of PLLA, microspheres were obtained only by dialysis from 1,4-dioxane solutions. Dialysis of PLLA solutions in THF, acetonitrile and DMF yielded particles in the form of microcrystals. In the case of dialysis of PLLA solutions in DMSO, the product was in form of crystalline flakes of c. 1 µm thickness. Microspheres composed of PLGA were amorphous. The degree of crystallinity of microparticles from PLLA was in the range of 39% -72%.

Molar Mass and Structural Characteristics of Poly[(lactide‐co‐(aspartic acid)] Block Copolymers

“…At a reaction temperature of 60 8C, the degree of polymerization of the lactide block is higher at higher L,L-lactide/PBA-NH 2 :SnOct 2 (monomer/macroinitiator) molar ratios in the feed and also increases with longer reaction time. The ring opening polymerization of L,L-lactide does not go to completion since equilibrium between growing species and unreacted L,L-lactide monomer is established, which prevents further growth of the poly(L,L-lactide) block.…”

“…By changing the Asp(OBz)-NCA/amine (monomer/ initiator) molar ratio in the feed we synthesized PBA-NH 2 homopolymers of different molar masses and low polydispersity indices (M n : 2800 and 5700 g mol , respectively) was put in a three necked glass flask equipped with a mechanical stirrer and contact thermometer, and dissolved in 10 mL of dry THF/1,4-dioxane mixture (1:1 ¼ v/v) during stirring at room temperature. After the PBA-NH 2 homopolymer had dissolved, a solution with a corresponding amount of L,L-lactide (1.083-0.271 g; 7.528-1.914 mmol) in THF and 0.05 mL of a 0.75 M solution of Sn(Oct) 2 were added. The reaction mixture was heated to the predetermined temperature (55, 60, 65, or 75 8C) and stirred for 6 h. The product was precipitated in cold hexane and washed several times with methanol to remove Sn(Oct) 2 and unreacted L,L-lactide monomer.…”

“…After the PBA-NH 2 homopolymer had dissolved, a solution with a corresponding amount of L,L-lactide (1.083-0.271 g; 7.528-1.914 mmol) in THF and 0.05 mL of a 0.75 M solution of Sn(Oct) 2 were added. The reaction mixture was heated to the predetermined temperature (55, 60, 65, or 75 8C) and stirred for 6 h. The product was precipitated in cold hexane and washed several times with methanol to remove Sn(Oct) 2 and unreacted L,L-lactide monomer. The product was then filtered and dried at room temperature in a vacuum oven.…”

“…[1][2][3][4][5][6][7][8][9][10] However, the application scope of poly(lactide) is limited since it is very hydrophobic polymer with no functional groups. In addition, the hydrolytic degradation rate of poly(lactide) for applications for drug delivery purposes is too slow due to its high crystallinity, which results in poorer soft tissue compatibility.…”

Biodegradable Polyesters for Tissue Engineering

“…Spherical particles and particles with irregular shape were obtained by dialysis against water of polymer solutions in water miscible organic solvents (acetonitrile, 1,4-dioxane, dimethylformamide, dimethylsulfoxide or tetrahydrofuran). [69] Shape of particles did depend on chemical structure of polyesters and on solvent from which the dialysis was carried on. Dialysis from 1,4-dioxane yielded spherical particles regardless of polyester that was used.…”