The effect of PLGA-PEG-PLGA modification on the sol-gel transition and degradation properties

Hybrid Hydrogel Networks by Photocrosslinking of Thermoresponsive α,ω‐Itaconyl‐PLGA‐PEG‐PLGA Micelles in Water: Influence of the Lithium Phenyl‐2,4,6‐Trimethylbenzoylphosphinate Photoinitinator

“…The obtained spectrum corresponds well with previously described syntheses. [12,17,18] Number-average molecular weight n M and molar composition of macromonomer sample were determined from integrals of characteristic proton intensities of PEG (OCH 2 CH 2 O) at δ = 3.55-3.75 ppm (multiplet, 4H) (1), lactic acid (O(CH 3 )CHO) in a range between δ = 5.1-5.35 ppm (multiplet, 1H) (3), and (OC(CH 3 )CHO) protons at δ = 1.5-1.75 ppm (multiplet, 3H) (4) and glycolic acid (OCH 2 O) at δ = 4.6-4.9 ppm (multiplet, 2H) (5). The amount of end-capped ITA was determined from integrals of characteristic proton intensities of itaconic acid backbone (OCH 2 (C = O)) at δ = 3.40-3.44 ppm (singlet, 2H) (6) and itaconic acid double bonds (OC(CH 2 )CCH 2 COOH) at δ = 6.35-6.5 ppm (singlet, 1H) (7a) and at δ = 5.7-5.8 ppm (singlet, 1H) (7b).…”

“…Moreover, we improved bulk mixture stirring enabling higher degree of modification of our copolymer giving aforementioned 89 mol% in comparison to previously published 63 mol%. [18] Since the functionalization with itaconic anhydride was shown to affect the properties of copolymer, such as thermoresponsive behavior and hydrolytic stability, [17] we assumed that the behavior of our copolymer can be slightly different in comparison with previously described systems with lower degree of modification.…”

“…The temperature-driven gelation of α,ω-itaconyl-PLGA-PEG-PLGA or related copolymers is affected by various parameters, such as molar mass of the copolymer, the ratio of PLGA to PEG, the ratio of d,l-lactide to glycolide (LA/GA), or the degree of substitution of ITA. [16,17,23] It should be emphasized that this characterization of thermoresponsive behavior of the copolymer was performed under the standard conditions, where the copolymer solutions were kept on ice prior the measurements and heated with the rate of 0.5 °C per minute (for more details, see Experimental Section: Rheological measurements). This is a commonly accepted procedure for the characterization of thermogelling polymers.…”

“…Prepared gels were stable longer than 22 days, comparing to the physical thermogel of the same α,ω-itaconyl-PLGA-PEG-PLGA macromonomer with similar concentration (16 wt%), which has not exceeded 11 days either in pH 4.3 or 7.4. [17] For the comparison, swelling ratio of hybrid hydrogel in physiological solution at 37 °C was monitored during 20 days to assess hydrolytic stability of the hybrid hydrogel samples ( Figure S8, Supporting Information). For this study, a new batch of the copolymer was used.…”

“…[16] Functionalization with itaconic acid affected both the hydrolytical degradation and thermoresponsive properties of resulting copolymer. [17] The functionalization also leads to acceleration of degradation rate of the non-crosslinked copolymers at pH 7.4. The potential of covalent crosslinking for hydrogel preparation from α,ω-itaconyl-PLGA-PEG-PLGA macromonomer was tested.…”