Caprolactonic Poloxamer Analog:  PEG-PCL-PEG

Abstract

The aqueous solution of poly(ethylene glycol)-poly(caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG) triblock copolymers (> 15. wt. %) undergoing "clear sol-gel-turbid sol" transition as the temperature increases from 20 to 60 degrees C has been developed. Light scattering and 13C NMR study suggested that the transition mechanisms are the micellar aggregation for the clear sol to gel transition (lower transition), whereas the increase in PCL molecular motion for gel to turbid sol transition (upper transition). In contrast to the previous thermogelling biodegradable polymers with a sticky paste morphology, the powder form of the PEG-PCL-PEG triblock copolymers makes it easy to handle and allows fast dissolution in water. Therefore, the lyophilization into a powder form followed by facile reconstitution was possible. This system is believed to be promising for drug delivery, cell therapy, and tissue engineering.

Injectable Biodegradable Hydrogels

“…Recently, PEG-PCL-PEG and PCL-PEG-PCL (Scheme 5) triblock copolymers have been introduced, and aqueous solutions thereof showed a clear sol-to-gel-to-turbid sol transition with an increase in temperature. [31,32] DLS and 13 C NMR studies indicated that the clear sol-to-gel transition arose from micellar aggregation, whereas the gel-to-turbid sol transition was driven by the breakage of the core-shell structure. Because of differences in structural topology, PCL-PEG-PCL had a higher G 0 (10 000 Pa) ( Figure 4) than did PEG-PCL-PEG (100 Pa) ( Figure 5).…”

Thermosensitive Self-Assembling Block Copolymers as Drug Delivery Systems

“…Terephthaloyl chloride (0.694 g, 3.3 mmol) and triethylamine (1.41 mL, 10.12 mmol) were added to the reaction mixtures and stirred at 60 °C for 24 h. The product was isolated by precipitation into diethyl ether, then the polymer was redissolved in 30 mL of methylene chloride, filtered, and precipitated by slowly adding diethyl ether. The residual solvent was removed under vacuum [95,[99][100][101]. Figure 4.…”

“…First of all, number average molecular weight and molecular weight distribution of the synthesized PEG-poly(-caprolactone) copolymers were determined using gel permeation chromatography (GPC) [96,[100][101][102].…”

“…1 H NMR measurements were performed to determine molecular structure and composition, such as the PEG/PCL block ratio [95,96,[100][101][102], while 13 C NMR has been used to observe spectral changes of PEG/PCL multiblock copolymer (20 wt % in D 2 O) as a function of temperature [95,101]. Furthermore, dynamic light scattering analyses facilitated studying the size of PEG/PCL multiblock copolymer as a function of temperature [95,101].…”

Bioreducible Micelles Self-Assembled from Poly(ethylene glycol)-Cholesteryl Conjugate As a Drug Delivery Platform

“…These micelles provide enhanced stability for lengthy drug circulation in blood owing to their low critical micelle concentration (CMC), followed by drug accumulation in solid tumors through an enhanced permeability and retention effect (EPR) [2,[4][5][6]. Among the various types of micelles, amphiphilic copolymers comprised of poly(ethylene glycol) (PEG) as the hydrophilic segments and polyesters including poly(D,L-lactic acid) (PDLLA), poly(glycolic acid) (PGA), and poly(ε-caprolactone) (PCL) as the hydrophobic segments have been extensively investigated as drug carriers due to their excellent biocompatibility and biodegradability [7][8][9][10][11][12][13]. However, the drug release inside cancer cells is often insufficient due to the highly hydrophobic and slow degrading nature of inner core-forming polyesters, which results in slow and incomplete drug release [14,15].…”