A Thermosensitive Poly(organophosphazene) Gel

Abstract

Thermosensitive poly(organophosphazenes) bearing α-amino-ω-methoxy-PEG (AMPEG) and hydrophobic l-isoleucine ethyl ester (IleOEt) as side groups have been synthesized, and their reversible sol−gel properties were investigated by means of 31P NMR spectroscopy and viscometer. In an aqueous solution, the poly(organophosphazenes) exhibited four-phase transitions with temperature gradually increasing: a transparent sol, a transparent gel, a opaque gel, and a turbid sol. The gelation properties of the polymer were affected by several factors such as the composition of substituents, the chain length of AMPEG, and the concentration of the polymer solutions. The more hydrophilic composition of the polymers offers the higher gelation temperature. The gelation of the polymer is presumed to be attributed to the hydrophobic interaction between the side-chain fragments (−CH(CH3)CH2CH3) of IleOEt which act as the physical junction in the polymer aqueous solution.

Injectable Biodegradable Hydrogels

“…[49][50][51] Aqueous solutions (10 wt.-%) of polyphosphazenes with MPEG350 and IleOEt exhibited a sol-to-gel transition as a function of temperature. [49] The maximal viscosity was 30 Pa Á s at 37 8C. The gelation properties were adjusted by varying the composition of the substituents, MPEG molecular weight, and concentration.…”

“…Such gels also showed higher gel strength compared with former gels. [49] Intermolecular association of hydrophobic oligopeptides was responsible for thermally induced gelation of the copolymer. The solgel transition and gel strength of polyphosphazenes were also modulated by the blending of hard and soft polymers.…”

Temperature‐Induced Hydrogels Through Self‐Assembly of Cholesterol‐Substituted Star PEG‐b‐PLLA Copolymers: An Injectable Scaffold for Tissue Engineering

“…G 0 values of temperature-responsive biodegradable polymers at 37 8C typically range from 100 to 1000 Pa, despite high polymer concentrations (above 20 wt%). [34][35][36][37] Accordingly, the significantly higher mechanical strength of the CP1-Chol2 hydrogel is advantageous for application as an injectable scaffold for tissue engineering.…”

“…Moreover, such a thermo-gelling biodegradable polymer would readily trap water-soluble pharmaceuticals or bioactive agents, such as proteins, and exhibit sustained release after injection at a target site. To date, PEG-block-poly(L-lactide)-block-PEG (PEG-PLLA-PEG) triblock copolymer, [34] PEG-block-poly(lactide-co-glicolide)-block-PEG (PEG-PLGA-PEG) triblock copolymer and PLGA-g-PEG graft copolymers, [35] tri-and multiblock copolymers of PEG and poly(caprolactone) (PCL), [36] and polyphosphazene [37] have been reported to show sol-gel transitions and are potential injectable polymers that would be degraded under physiological conditions after in-vivo implantation. However, the mechanical strength of hydrogels previously prepared from these block copolymers solution is insufficient.…”

Metabolic limitations of the use of nucleoside analogs in cancer therapy may be overcome by application of nanoparticles as drug carriers: A review

“…These polymers had biodegradable and thermosensitive properties that improved 5-FU release kinetics and reduced both drug-and carrier-related toxicity. Thermosensitive polymers of this type exist in solution at low temperatures, whereas at higher temperatures (body temperature), they crosslink during the gelation process [Lee et al, 1999[Lee et al, , 2002. Hydrogels, when loaded with active components, can potentially be injected into the specific tissue where they can function as a local, slowly degradable drug depot.…”