Preparation of chitosan-g-polycaprolactone copolymers through ring-opening polymerization of ε-caprolactone onto phthaloyl-protected chitosan

Amphiphilic chitosan-g-poly(trimethylene carbonate) - A new approach for biomaterials design

The paper presents the synthesis and characterization of poly(trimethylene carbonate) grafted chitosan as a new water soluble biopolymer suitable for in vivo applications. The synthesis was performed via ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) (TMC) monomer, initiated by the functional groups of chitosan in the presence of toluene as solvent/swelling agent. By varying the molar ratio between the glucosamine units of chitosan and TMC, a series of chitosan derivatives with different content of poly(trimethylene carbonate) chains was synthetized. The structural characterization of the polymers was realized by FTIR and ¹H NMR spectroscopy and their solubility was assessed in water and in organic solvents as well. The biocompatibility was investigated by MTS assay on Normal Human Dermal Fibroblasts, and the biodegradability was evaluated in lysozyme buffer solution. Further, the surface properties of the polymer films were analyzed by polarized optical microscopy, atomic force microscopy and water-to-air contact angle measurements. It was established that, by 5% substitution of chitosan with poly(trimethylene carbonate) chains having an average polymerization degree of 7, a water soluble polymer can be attained. Compared to the pristine chitosan, it has improved biocompatibility in solution and moderate wettability and higher biodegradability rate in solid state, pointing its suitability for in vivo applications.

Preparation and characterization of polycaprolactone/chitosan-g-polycaprolactone/hydroxyapatite electrospun nanocomposite scaffolds for bone tissue engineering

Chitosan (CS) and poly (ε-caprolactone) (PCL) are two most usable polymers in biomedical applications. In this study, chitosan has been modified and incorporated with poly (ε-caprolactone) to fabricate bone tissue engineering scaffold. Moreover, hydroxyapatite nanoparticles were added to enhance bioactivity and mechanical properties of scaffold. Bulk and fibrous comparative results showed significant effect of fiber diameter and distribution on mechanical properties. Moreover, the incorporation of chitosan-g-poly (ε-caprolactone) (CS-g-PCL) significantly decreases fiber diameter of pure PCL scaffold. Furthermore, both CS-g-PCL and nHA enhance mineralization and degradation of the scaffold soaked in simulated body fluid (SBF) and phosphate buffered saline (PBS), respectively. In vitro cytocompatibility assays also confirmed high cell viability and proliferation on the samples. Taken together, the results suggest that the microfabricated nanocomposite scaffolds could be used in bone tissue engineering.

Assessment of the Role of Ginsenoside RB1 Active Substance in Alginate/Chitosan/Lovastatin Composite Films

This article reports the effect of ginsenoside Rb1 on some properties, morphology, and the drug release process of the chitosan (CS)/alginate (AG)/lovastatin (LOV) composite films prepared by a solution method using different contents of ginsenoside Rb1. The ratio of AG/CS was fixed at 4/1 (wt.%/wt.%), the content of LOV was 10 wt.%, and the content of ginsenoside Rb1 was changed from 1 to 5 wt.%. The results of scanning electron microscopy and Fourier transform infrared spectroscopy analysis showed that the composite films have a heterogeneous structure and the ginsenoside Rb1 content influenced on the structure of composite films. The presence of ginsenoside Rb1 did not influence on the melting temperature of these films but caused a significant difference in the melting enthalpy of the films. The ginsenoside Rb1 was also contributed positively on the LOV release from these films in different pH buffer solutions. The LOV release process from these films included two stages (fast/burst release and slow/control release). It was increased remarkably by the synergic effect of LOV and ginsenoside Rb1 in the drug release process. From the obtained results, we suggested that ginsenoside Rb1 plays an important role not only in the enhancement of health and immunity as general but also as an efficient agent in control of the LOV size as well as LOV drug release from the composite films.

Chitosan Derivatives: Introducing New Functionalities with a Controlled Molecular Architecture for Innovative Materials

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed.

Syntheses and Characterization of Chitosan Oligosaccharide-Graft-Polycaprolactone Copolymer I Thermal and Spherulite Morphology Studies

The thermoplastic graft copolymers of chitosan oligosaccharide (PHCSO-g-PCL) were successfully synthesized via ring-opening polymerization (ROP) of ε-caprolactone (CL) through an amino group protection route using phthaloyl chitosan oligosaccharide (PHCSO) as intermediate. The graft reaction was carried out in Pyridine at 120 °C with a chitosan oligosaccharide (CSO) initiator and a tin 2-ethylhexanoate (Sn (Oct)2) catalyst. The prepared copolymer was characterized by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle X-ray diffraction (WAXD). DSC analysis of PHCSO-g-PCL showed higher melting point at 54.8 °C than linear PCL. The TGA analysis showed that PHCSO-g-PCL was more thermal stable than original CSO. The banded spherulite structure of PHCSO-g-PCL and the growth of spherulite were observed by polarized optical microscope (POM); this was further proven by WAXD results.

Chitosan-polycaprolactone copolymer microspheres for transforming growth factor-β1 delivery

Chitosan-polycaprolactone (CPC) copolymer microspheres loaded with transforming growth factor-β1 (TGF-β1) were fabricated with an emulsification method using sodium tripolyphosphate as crosslinker. They were found to be dense and had regular sphericity with various diameters changing from several hundred nanometers to a few micrometers. Their loading efficiency could be regulated by both the amount of crosslinker and the composition of CPCs, and some microspheres showed their loading efficiency higher than 80%. It was observed that in neutral PBS media, the composition of CPCs predominantly governed swelling behavior and release profiles of the microspheres while the effect of crosslinker on the swelling and release behavior was limited. The initial fast releases of TGF-β1 from different microspheres could be significantly decreased with increasing polycaprolactone content in CPCs, and some microspheres were able to maintain sustained releases of TGF-β1 by mainly controlling their composition. In addition, in a simulated acidic environment (pH 6.5) for cartilage lesions, release patterns of the microspheres were notably modulated by pH but some selected microspheres could still well administrate the release of TGF-β1 in a sustained way without severe burst features.

Fabrication of cationic nanomicelle from chitosan-graft-polycaprolactone as the carrier of 7-ethyl-10-hydroxy-camptothecin

In this research, amphiphilic brush-like polycations were synthesized, and used to fabricate cationic nanomicelle as the carrier of 7-ethyl-10-hydroxy-camptothecin (SN-38), in order to enhance its cellular uptake, solubility and stability in aqueous media. In particular, cationic chitosan-graft-polycaprolactone (CS-g-PCL) copolymers were synthesized with a facile one-pot manner via ring-opening polymerization of epsilon-CL onto the hydroxyl groups of CS by using methanesulfonic acid as solvent and catalyst. The formation of CS-g-PCL nanomicelles was confirmed by fluorescence spectrophotoscopy and particle size measurements. It was found that all the nanomicelles showed spherical shapes with narrow size distributions. Their sizes ranged from 47 to 113 nm, and the zeta potentials ranged from 26.7 to 50.8 mV, depending on the grafting content of PCL in CS-g-PCL, suggesting their passive targeting to tumor tissue and endocytosis potential. Water-insoluble antitumor drug, SN-38, was easily encapsulated into CS-g-PCL nanomicelles by lyophilization method. In comparison with bare CS-g-PCL nanomicelles, the corresponding SN-38-loaded nanomicelles showed increased particle sizes and a little reduced zeta potentials. With an increase of grafting PCL content, the drug encapsulation efficiency (EE) and drug loading (DL) of the nanomicelles increased from 64.3 to 84.6% and 6.43 to 8.66%, respectively, whereas their accumulative drug release showed a tendency to decrease due to the enhanced hydrophobic interaction between hydrophobic drug and hydrophobic PCL segments in CS-g-PCL. Also, the CS-g-PCL nanomicelles effectively protected the active lactone ring of SN-38 from hydrolysis under physiological condition, due to the encapsulation of SN-38 into the hydrophobic cores in the nanomicelles. Compared with free SN-38, the SN-38-loaded nanomicelles showed essential decreased cytotoxicity against L929 cell line, and bare CS-g-PCL nanomicelles almost showed non-toxicity. These results suggested the potential utilization of the CS-g-PCL nanomicelles as the carriers of hydrophobic drugs with improving the delivery and release properties.

Novel amphiphilic ternary polysaccharide derivates chitosan-g- PCL-b-MPEG: Synthesis, characterization, and aggregation in aqueous solution

Chitosan-g-PCL-b-MPEG copolymers of various compositions were successful synthesized via a protection-graft-deprotection procedure, by the esterification of phthaloyl-protected chitosan (PHCS) with MPEG-b-PCL-COOH, which was synthesized from MPEG and epsilon-caprolactone and carboxylated by maleic anhydride. The chemical structure of the chitosan-g-PCL-b-MPEG was characterized by Fourier transform infrared and NMR spectroscopy. The chitosan-g-PCL-b-MPEG was obtained as amphoteric hybrid with amino polysaccharide backbone and amphiphilic MPEG-b-PCL side chain. Their crystallinity and aggregation behavior in aqueous solution were also investigated.

Synthesis and characterization of the biodegradable polycaprolactone-graft-chitosan amphiphilic copolymers

A novel synthetic approach to biodegradable amphiphilic copolymers based on poly (epsilon-caprolactone) (PCL) and chitosan was presented, and the prepared copolymers were used to prepare nanoparticles successfully. The PCL-graft-chitosan copolymers were synthesized by coupling the hydroxyl end-groups on preformed PCL chains and the amino groups present on 6-O-triphenylmethyl chitosan and by removing the protective 6-O-triphenylmethyl groups in acidic aqueous solution. The PCL content in the copolymers can be controlled in the range of 10-90 wt %. The graft copolymers were thoroughly characterized by 1H NMR, 13C NMR, FT-IR and DSC. The nanoparticles made from the graft copolymers were investigated by 1H NMR, DLS, AFM and SEM measurements. It was found that the copolymers could form spherical or elliptic nanoparticles in water. The amount of available primary amines on the surface of the prepared nanoparticles was evaluated by ninhydrin assay, and it can be controlled by the grafting degree of PCL.