Temperature-Sensitive Sol-Gel Transition Behavior of Biodegradable Four-Arm Star-Shaped PEG-PLGA Block Copolymer Aqueous Solution

Abstract

Biodegradable four-arm star-shaped poly(ethylene glycol-b-DL-lactic acid-co-glycolic acid) block copolymers (4arm PEG-PLGA) were synthesized by ring-opening polymerization of DL-lactide and glycolide using 4arm PEG as an initiator and Sn(oct) 2 as a catalyst. In aqueous solution, they showed reversible sol to gel to sol transition behavior while increasing the temperature from 0 C to 40 C. The larger the molecular weight or the stronger the relative hydrophobicity of the hydrophobic PLGA block, the smaller the critical gel concentration (CGC). 4arm PEG-PLGA formed gels at lower CGC (13 wt %) than the inverse 4arm PLGA-PEG (24 wt %) due to the differences in their molecular structures.KEY WORDS: Hydrogels / Star Polymers / Sol-gel Transition / Biodegradable / Temperature-sensitive polymers of which aqueous solutions undergo sol-gel transition in response to temperature changes are especially attractive in drug delivery applications as an in situ gel-forming device. These polymers might be mixed with therapeutic agents such as drugs, cells or proteins in the sol state and injected using a syringe into the body to form a depot system.

Novel Structural Changes during Temperature‐Induced Self‐Assembling and Gelation of PLGA‐PEG‐PLGA Triblock Copolymer in Aqueous Solutions

“…This suggests that the moieties are initially slightly compressed upon a temperature raise. This type of behavior has been reported for PLGA‐PEG‐PLGA copolymers . After passing CP, η* rises with increasing temperature and this is attributed to loose intermicellar structures or aggregates; this conjecture is supported by the turbidity results discussed above.…”

Injectable Drug Delivery System Based on In Situ Self‐Assembly of Liquid Star Polyethylene Glycol–Poly(lactic‐co‐glycolic acid)

“…Five starPEG–PLGA copolymers with varying molecular weights ( Table 1 ) were synthesized by the ring‐opening polymerization method using starPEG 2 kDa as an initiator and stannous octoate as catalyst in a bulk reaction ( Figure 2 A). [ 15,17 ] The obtained copolymers were identified and analyzed by H 1 ‐NMR, presenting a molar ratio of 1:3 between glycolice acid and lactic acid units (Figure 2B). Average molecular weights, analyzed by gel permeation chromatography (GPC) (Figure 2C), ranged between 2087 Da for starPEG and 13 905 Da for starPEG–PLGA12 000, displaying a good fit between the feeding ratio and the obtained M w .…”

Design of an Interpenetrating Polymeric Network Hydrogel Made of Calcium-Alginate from a Thermos-Sensitive Pluronic Template as a Thermal-Ionic Reversible Wound Dressing

“…The reversible characteristics of this dual-network hydrogel and the combination of calcium alginate and thermally crosslinked PF127 are critical factors for wound management. The sol–gel transition behavior is accompanied by a change in viscosity, which is the tendency of the fluid to resist flow [ 50 , 51 ]. Hence, the reversible property of the IPN hydrogel, which is strongly dependent on the applied temperature, is described by viscoelasticity.…”