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Copolyesters of ε-caprolactone and l-lactide catalyzed by a tetrabutylammonium phthalimide-N-oxyl organocatalyst.

ABSTRACT: Aliphatic polyesters are biocompatible materials that can be used in biomedical applications. We report here the use of tetrabutylammonium phthalimide-N-oxyl catalyst (TBAPINO), as a thermally stable organocatalyst for the ring-opening polymerization (ROP) of cyclic esters under mild conditions. In the solution ROP of ε-caprolactone (ε-CL), quantitative conversion and M _n of ∼20 000 g mol^-1 are achieved in a wide temperature range from -15 to 60 °C. Under bulk condition, the conversion of ε-CL reaches over 85% at 120 °C within 2 h. The living ROP character of l-lactide (l-LA) catalyzed over TBAPINO is proved by multiple additions of monomer in the bulk polymerization. The catalyst shows comparable selectivity towards the ring-opening polymerization of l-LA and ε-CL. Their copolymerization over TBAPINO is carried out in one-pot bulk condition in terms of the reaction time, monomer feed ratio, and sequence of addition. The colorless poly(ε-caprolactone-co-lactide) (PCLA) is obtained with considerable conversion of both monomers with the M _n over 22 000 g mol^-1.

SUBMITTER: Feng Z

PROVIDER: S-EPMC9033473 | biostudies-literature | 2021 May

REPOSITORIES: biostudies-literature

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Copolyesters of ε-caprolactone and l-lactide catalyzed by a tetrabutylammonium phthalimide-N-oxyl organocatalyst.

Feng Zhiheng Z Wu Li L Dong Huan H Liu Boping B Cheng Ruihua R

RSC advances 20210526 31

Aliphatic polyesters are biocompatible materials that can be used in biomedical applications. We report here the use of tetrabutylammonium phthalimide-N-oxyl catalyst (TBAPINO), as a thermally stable organocatalyst for the ring-opening polymerization (ROP) of cyclic esters under mild conditions. In the solution ROP of ε-caprolactone (ε-CL), quantitative conversion and M n of ∼20 000 g mol-1 are achieved in a wide temperature range from -15 to 60 °C. Under bulk ...[more]

PMID: 35478625

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Project description:Vascular endothelial growth factor (VEGF) is the major regulating factor for the formation of new blood vessels, also known as angiogenesis. VEGF is often incorporated in synthetic scaffolds to promote vascularization and to enhance the survival of cells that have been seeded in these devices. Such applications require sustained local delivery of VEGF of around 4 weeks for stable blood vessel formation. Most delivery systems for VEGF only provide short-term release for a couple of days, followed by a release phase with very low VEGF release. We now have developed VEGF-loaded polymeric microspheres that provide sustained release of bioactive VEGF for 4 weeks. Blends of two swellable poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone)-b-poly(l-lactide) ([PCL-PEG-PCL]-b-[PLLA])-based multiblock copolymers with different PEG content and PEG molecular weight were used to prepare the microspheres. Loading of the microspheres was established by a solvent evaporation-based membrane emulsification method. The resulting VEGF-loaded microspheres had average sizes of 40-50 μm and a narrow size distribution. Optimized formulations of a 50:50 blend of the two multiblock copolymers had an average VEGF loading of 0.79 ± 0.09%, representing a high average VEGF loading efficiency of 78 ± 16%. These microspheres released VEGF continuously over 4 weeks in phosphate-buffered saline pH 7.4 at 37 °C. This release profile was preserved after repeated and long-term storage at -20 °C for up to 9 months, thereby demonstrating excellent storage stability. VEGF release was governed by diffusion through the water-filled polymer matrix, depending on PEG molecular weight and PEG content of the polymers. The bioactivity of the released VEGF was retained within the experimental error in the 4-week release window, as demonstrated using a human umbilical vein endothelial cells proliferation assay. Thus, the microspheres prepared in this study are suitable for embedment in polymeric scaffolds with the aim of promoting their functional vascularization.

Project description:BackgroundTissue engineering has become a promising therapeutic approach for bone regeneration. Nanofibrous scaffolds have attracted great interest mainly due to their structural similarity to natural extracellular matrix (ECM). Poly(lactide-co-ε-caprolactone) (PLCL) has been successfully used in bone regeneration, but PLCL polymers are inert and lack natural cell recognition sites, and the surface of PLCL scaffold is hydrophobic. Silk fibroin (SF) is a kind of natural polymer with inherent bioactivity, and supports mesenchymal stem cell attachment, osteogenesis, and ECM deposition. Therefore, we fabricated hybrid nanofibrous scaffolds by adding different weight ratios of SF to PLCL in order to find a scaffold with improved properties for bone regeneration.MethodsHybrid nanofibrous scaffolds were fabricated by blending different weight ratios of SF with PLCL. Human adipose-derived stem cells (hADSCs) were seeded on SF/PLCL nanofibrous scaffolds of various ratios for a systematic evaluation of cell adhesion, proliferation, cytotoxicity, and osteogenic differentiation; the efficacy of the composite of hADSCs and scaffolds in repairing critical-sized calvarial defects in rats was investigated.ResultsThe SF/PLCL (50/50) scaffold exhibited favorable tensile strength, surface roughness, and hydrophilicity, which facilitated cell adhesion and proliferation. Moreover, the SF/PLCL (50/50) scaffold promoted the osteogenic differentiation of hADSCs by elevating the expression levels of osteogenic marker genes such as BSP, Ocn, Col1A1, and OPN and enhanced ECM mineralization. In vivo assays showed that SF/PLCL (50/50) scaffold improved the repair of the critical-sized calvarial defect in rats, resulting in increased bone volume, higher trabecular number, enhanced bone mineral density, and increased new bone areas, compared with the pure PLCL scaffold.ConclusionThe SF/PLCL (50/50) nanofibrous scaffold facilitated hADSC proliferation and osteogenic differentiation in vitro and further promoted new bone formation in vivo, suggesting that the SF/PLCL (50/50) nanofibrous scaffold holds great potential in bone tissue regeneration.

Dataset Information

Copolyesters of ε-caprolactone and l-lactide catalyzed by a tetrabutylammonium phthalimide-N-oxyl organocatalyst.

Publications

Copolyesters of ε-caprolactone and l-lactide catalyzed by a tetrabutylammonium phthalimide-<i>N</i>-oxyl organocatalyst.

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