Synthesis and properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/chitin nanocrystals composite scaffolds for tissue engineering

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/chitin nanocrystals (CNC) composite scaffolds were synthesized by the salt leaching and thermally induced phase separation (TIPS) technique. The scaffolds have porous structures with macro-pores (100-300 mm in diameters) and micro-pores (10 mm). The surface characteristics of the scaffolds were characterized by X-ray photoelectron spectroscopy (XPS) and static water contact angle measurement, and the mechanical properties were investigated by a compression test. Human adipose-derived stem cells (hADSCs) were seeded onto the PHBV/CNC scaffolds and in vitro cell culture results showed that the composite scaffolds enhanced the hADSCs adhesion, which implies that the material may have potential application in tissue engineering.     

PHBV/Sol-gel Bioglass多孔材料在模拟生理溶液中的化学反应研究

3-羟基丁酸-co-3-羟基戊酸共聚物(PHBV)/生物活性玻璃(SGBG)是一种用于骨和软骨组织工程支架的新型多孔复合材料,本文探讨了PHBV/SGBG在模拟生理溶液中的一系列化学反应,以及多孔材料在模拟生理溶液中浸泡后的成分和结构变化.研究结果表明,在SBF溶液中浸泡后,SGBG与SBF溶液的离子交换反应和PHBV的降解反应使SBF溶液的离子浓度发生变化,并在PHBV/SGBG表面形成了结晶态类骨碳酸羟基磷灰石.     

Effect of a scaffold fabricated thermally from acetylated PLGA on the formation of engineered cartilage

A MHDS has been employed to fabricate 3D scaffolds from PLGA with acetyl endgroups to achieve in vivo regeneration of cartilage tissue. The fabricated acetylated-PLGA scaffold showed open pores and interconnected structures. Rabbit chondrocytes were seeded on the PLGA scaffolds and transplanted immediately into subcutaneous sites of athymic mice. Chondrocytes transplantation with untreated PLGA scaffolds served as a control. Histological analysis of the implants at 4 weeks with H&E staining and alcian blue staining revealed higher extracellular matrix and GAG expression at the neocartilage in the PLGA-6Ac scaffolds than that of the PLGA-6OH scaffold group. This endgroup-modified scaffold may be useful for successful cartilage tissue engineering in orthopedic applications.     

A hybrid scaffold of poly(lactide-<Emphasis Type="Italic">co</Emphasis>-glycolide) sponge filled with fibrin gel for cartilage tissue engineering

The poly(lactide-co-glycolide)(PLGA) sponge fabricated by a gelatin porogen leaching method was filled with fibrin gel to obtain a hybrid scaffold for chondrocytes culture in vitro.The fibrin gel evenly distributed in the hybrid scaffold with visible fibrinogen fibers after drying.In vitro culture it was found that in the hybrid scaffold the chondrocytes distributed more evenly and kept a round morphology as that in the normal cartilage.Although the chondrocytes seeded in the control PLGA sponges showed similar proliferation behavior with that in the hybrid scaffolds,they were remarkably elongated,forming a fibroblast-like morphology.Moreover,a larger amount of glycosaminoglycans was secreted in the hybrid scaffolds than that in the PLGA sponges after in vitro culture of chondrocytes for 4 weeks.The results suggest that the fibrin/PLGA hybrid scaffold may be favorably applied for cartilage tissue engineering.     

Encapsulation and release of biomolecules from Ca-P/PHBV nanocomposite microspheres and three-dimensional scaffolds fabricated by selective laser sintering

This study focused on the fabrication of calcium phosphate (Ca-P)/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposite scaffolds loaded with biomolecules using the selective laser sintering (SLS) technique and their evaluation. Ca-P/PHBV nanocomposite microspheres loaded with bovine serum albumin (BSA) as the model protein were fabricated using the double emulsion solvent evaporation method. The encapsulation efficiency of BSA in PHBV polymer microspheres and Ca-P/PHBV nanocomposite microspheres were 18.06 ± 0.86% and 24.51 ± 0.60%, respectively. The BSA loaded Ca-P/PHBV nanocomposite microspheres were successfully produced into three-dimensional porous scaffolds with good dimensional accuracy using the SLS technique. The nanocomposite microspheres served as protective carriers and maintained the bioactivity of BSA during SLS. The effects of SLS parameters such as laser power and scan spacing on the encapsulation efficiency of BSA in the scaffolds and in vitro BSA release were studied. An initial burst release was observed, which was followed by a slow release of BSA. After 28-day release, The PHBV matrix was slightly degraded after 28-day in vitro release study. It was shown that nanocomposite scaffolds with controlled architecture obtained via SLS could be incorporated with biomolecules, enhancing them with more functions for bone tissue engineering application or making them suitable for localized delivery of therapeutics.     

Surface modification with peptide for enhancing chondrocyte adhesion and cartilage regeneration in porous scaffolds

The present study presents the regeneration of cartilage in hybrid scaffolds comprising polyethylene oxide (PEO) and chitosan with surface CDPGYIGSR. This surface peptide was grafted via crosslinking onto the scaffolds. The pores in the scaffolds were interconnected and uniformly distributed with an average diameter about 200-250 μm. A high weight percentage of PEO in the matrix yielded a rugged topography of the pore surfaces. The adhesion of bovine knee chondrocytes (BKCs) in the peptide-grafted scaffolds was more efficient than that in the peptide-free scaffolds. In addition, the constructs with surface peptide could stimulate chondrogenesis with enhanced quantities of BKCs, glycosaminoglycans (GAGs), and collagen over cultivation. The histological staining of the proliferated BKCs and secreted GAGs indicated that the surface peptide favored the production of neocartilage in the constructs. Moreover, the immunochemical staining against type II collagen demonstrated the maintenance of phenotypic chondeocytes on the peptide-grafted surfaces. The peptide-grafted PEO/chitosan scaffolds can be applied to the treatment for injured cartilage in preclinical trials.     

Synergistic effect of compatibilizer and sepiolite on the morphology of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(butylene succinate) blends

Blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(butylene succinate) (PBS) with different PHBV/PBS weight ratios (100/0, 75/25, 50/50 and 0/100) were elaborated by melt mixing. The morphological investigation of the different samples, in comparison with that of neat PHBV and neat PBS, pointed out that PHBV/PBS blends form a biphasic system over the whole composition range. Low amount of compatibilizing agent (5 wt%), obtained by grafting maleic anhydride (MA) onto PHBV, i.e. PHBV-g-MA, was used for improving the miscibility between the two components of the blend. The incorporation of a fibrous filler as the sepiolite, easily dispersible in a polymer matrix, was also investigated. The morphology of the different blends as well as the evolution of their material properties were discussed in terms of the sepiolite and compatibilizing agent contents. The dispersion of PBS in the PHBV matrix markedly became finer with incorporation of sepiolite and PHBV-g-MA, due to enhanced interactions between the components. This paper highlighted a synergistic effect induced by the presence of both compatibilizer and sepiolite leading to an improved miscibility of the two blend components. The resulting properties were correlated with the morphology observed for the different blends.     

Surface Modification of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Membrane by Combining Surface Aminolysis Treatment with Collagen Immobilization

Amino groups were introduced onto a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) surface by applying 1,6-hexanediamine treatment. The effects of aminolysis time and 1,6-hexanediamine concentration on hydrophilicity of the treated PHBV were investigated using contact angle measurement. The occurrence of the aminolysis and the introduction of NH₂ groups were verified by X-ray photoelectron spectroscopy (XPS) and ninhydrin method. By use of the NH₂ groups as active sites, collagen was further immobilized on the aminolyzed PHBV (NH₂-PHBV) membrane via a cross-linking agent, glutaraldehyde. The increase of nitrogen content and further decrease of water contact angle after immobilization of collagen suggested that the surfaces became more hydrophilic. Mouse bone marrow stromal cells (BMSc) cultured on untreated PHBV and treated PHBV films were evaluated by cell attachment, cell proliferation, and morphological observation under scanning electron microscope (SEM). The order of cytocompatibility is Coll-PHBV > NH₂-PHBV > PHBV, indicating coll-PHBV was a promising material in future tissue-engineering application.     

Evolution of concentric spherulites in crystalline-crystalline poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-b-poly(ethylene glycol) copolymers

Crystalline-crystalline poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly (ethylene glycol) (PEG) block copolymers (PHEGs) were synthesized by telechelic hydroxylated PHBV2000 and PEG with different number-average molecular weights. The synthesized PHEGs were analyzed using gel permeation chromatography and proton nuclear magnetic resonance. The cooling curves of the differential scanning calorimetry showed that the range of the melt-crystallization temperature of the PEG and PHBV blocks in the PHEGs partially overlapped. The spherulite of each PEG block and each PHBV block in the PHEGs crystallizes individually, but nucleated in the same site to form a concentric spherulite. The observations of the hot-stage polarized microscope (HSPM) showed that the first spherulite growth acted as a template for the later spherulite growth in the PHBV-b-PEG concentric spherulite. The spherulite growth rate of individual spherulite from the PEG block and PHBV block in PHEGs depends on the crystallization environment. The evolution of concentric spherulites in PHEGs at different crystallization conditions was studied in this study.     

Crystallization behavior, thermal and mechanical properties of PHBV/graphene nanosheet composites

Biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene nanosheet (GNS) composites were prepared via a solution-casting method at low GNS loadings in this work. Transmission electron microscopy revealed that a fine dispersion of GNSs was achieved in the PHBV matrix. The thermal properties of the nanocomposites were investigated by thermogravimetric analysis, and the results showed that the thermal stability of PHBV was significantly improved with a very low loading of GNSs. Nonisothermal melts crystallization behavior, spherulitic morphology and crystal structure of neat PHBV and the PHBV/GNSs nanocomposites were investigated, and the experimental results indicated that crystallization behavior of PHBV was enhanced by the presence of GNSs due to the heterogeneous nucleation effect; however, the two-dimensional (2D) GNSs might restrict the mobility of the PHBV chains in the process of crystal growing. Dynamic mechanical analysis studies showed that the storage modulus of the PHBV/GNSs nanocomposites was greatly improved.     

STUDY ON BIODEGRADABILITY OF POLY (3-HYDROXYBUTYRATE-co-3-HYDROXYVALERATE)/ORGANOPHILIC MONTMORILLONITE NANOCOMPOSITES

1. INTRODUCTION Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has been recognized as apotential environment-friendly substitute for traditional plastics. The structure, mechanicalproperties and biodegradability of PHBV as biodegradable plastic have been reported by many groups [1-3]. However, PHBV presents some problems, such as high cost, slow crystallization rate, relatively difficult processing and high degree of crystallinity. Therefore, it is difficult to use PHBV widel…     

Valorization of olive husk flour as a filler for biocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate): Effects of silane treatment

The paper deals with the influence of surface treatment of olive husk flour (OHF) by trimethoxyoctadecylsilane (TMOS) on the morphology and physical properties of bio-composites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Biocomposites based on PHBV/OHF: 80/20 (w/w) before and after filler treatment were prepared by melt compounding, while the modification of OHF surface by TMOS was performed by thermo-chemical vapor deposition. Scanning electron microscopic observations showed that modification of OHF by TMOS led to homogeneous and finer dispersion of the filler particles in PHBV matrix, indicating improved compatibility between the two components. Further, TGA data revealed an increase in thermal stability of treated PHBV/OHF biocomposites. An increase in the crystalline index determined by DSC was also observed due to the nucleating effect of OHF in the polymer matrix, however more pronounced for the treated biocomposites. The latter exhibited better tensile properties, as confirmed by DMA results, showing higher reinforcing effect of OHF for the treated biocomposites. This study highlighted significant improvements of the properties of PHBV/OHF biocomposites through silane treatment of OHF.     

STUDY ON BIODEGRADABILITY OF POLY（3-HYDROXYBUTYRATE-co-3-HYDROXYVALERATE）／ORGANOPHILIC MONTMORILLONITE NANOCOMPOSITES

Poly (3-lydroxybutyrate-co-3-hydroxyvalerate)/Organophilic montmorillonite(PHBV/OMMT) nanocomposites were prepared and the biodegradability of the PHBV/OMMT nanocomposites was studied by a cultivation degrading method in soil suspension The relationship between structure and biodegradability of PHBV/OMMT nanocomposites was investigated. The results showed that the biodegradability of PHBV/OMMT nanocomposites decreased with increasing amount of OMMT and it was related to the number of PHBV degrading microorganisms in degradation environment, the anti-microbial property of OMMT and the degree of crystallinity of the nanocomposites.     

Bioactive Phenylboronic Acid-Functionalized Hyaluronic Acid Hydrogels Induce Chondro-Aggregates and Promote Chondrocyte Phenotype

Hydrogels are extensively investigated as biomimetic extracellular matrix (ECM) scaffolds in tissue engineering. The physiological properties of ECM affect cellular behaviors, which is an inspiration for cell-based therapies. Photocurable hyaluronic acid (HA) hydrogel (AHAMA-PBA) modified with 3-aminophenylboronic acid, sodium periodate, and methacrylic anhydride simultaneously is constructed in this study. Chondrocytes are then cultured on the surface of the hydrogels to evaluate the effect of the physicochemical properties of the hydrogels on modulating cellular behaviors. Cell viability assays demonstrate that the hydrogel is non-toxic to chondrocytes. The existence of phenylboronic acid (PBA) moieties enhances the interaction of chondrocytes and hydrogel, promoting cell adhesion and aggregation through filopodia. RT-PCR indicates that the gene expression levels of type II collagen, Aggrecan, and Sox9 are significantly up-regulated in chondrocytes cultured on hydrogels. Moreover, the mechanical properties of the hydrogels have a significant effect on the cell phenotype, with soft gels (≈2 kPa) promoting chondrocytes to exhibit a hyaline phenotype. Overall, PBA-functionalized HA hydrogel with low stiffness exhibits the best effect on promoting the chondrocyte phenotype, which is a promising biomaterial for cartilage regeneration.     

Hexosaminidase inhibitors as new drug candidates for the therapy of osteoarthritis.

BACKGROUND: Articular cartilage from patients with osteoarthritis is characterized by a decreased concentration and reduced size of glycosaminoglycans. Degeneration of the cartilage matrix is a multifactorial process, which is due in part to accelerated glycosaminoglycan catabolism. Recently, we have demonstrated that hexosaminidase represents the dominant glycosaminoglycan-degrading glycosidase released by chondrocytes into the extracellular compartment and is the dominant glycosidase in synovial fluid from patients with osteoarthritis. Inhibition of hexosaminidase activity may represent a novel approach to the prevention of cartilage matrix glycosaminoglycan degradation and a potentially new strategy to treat osteoarthritis. RESULTS: We have synthesized and investigated a series of iminocyclitols designed as transition-state analog inhibitors of human hexosaminidase, and demonstrated that the five-membered iminocyclitol 4 expresses the strongest inhibitory activity with K(i)=24 nM. Inhibition of hexosaminidase activity in human cultured articular chondrocytes and human chondrosarcoma cells with iminocyclitol 4 resulted in accumulation of hyaluronic acid and sulfated glycosaminoglycans in the cell-associated fraction. Similarly, incubation of human cartilage tissue with iminocyclitol 4 resulted in an accumulation of glycosaminoglycans in the pericellular compartment. CONCLUSIONS: Inhibition of hexosaminidase activity represents a new strategy for preventing or even reversing cartilage degradation in patients with osteoarthritis.     

生物活性复合材料在生物矿化过程中的微观形貌与离子浓度变化

采用3-羟基丁酸酯-3-羟基戊酸酯的共聚物(PHBV)与磷酸三钙(TCP)、羟基磷灰石(HA)、生物活性玻璃(BG)等进行复合,获得了性能优良的生物活性骨组织工程支架材料和骨修复材料.研究和比较了3种复合材料在体外模拟生理环境中发生的生物矿化反应,对比了反应前后因矿化物的形成导致的表面微观形貌的变化,通过检测反应液离子浓度的变化对不同材料的矿化过程和生物活性进行了定量表征.研究结果表明,3种复合材料在模拟生理溶液中发生生物矿化的过程和程度不同,其中PHBV/BG的生物活性反应最为明显.     

Polymers for Multifunctional Textiles

Biodegradable P[(R,S)-3HB-co-LA] and P[(R,S)-3HB-co-CL] copolyesters for special medical application, i.e. as scaffolds for cartilage and soft tissue engineering, were synthesized by transesterification of the corresponding homopolymers, i.e. a-PHB and poly(L-lactide) or a-PHB and poly(e-caprolactone), respectively. The carried out biological studies emphasized the biocompatibility of the copolymer PHBV/a-PHB, in for its using in the manufacturing of the haemostatical dressings.     

Assessing the mechanical,phase inversion,and rheological properties of poly-[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) blended with poly-(l-lactic acid) (PLA)

Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly-(l-lactic acid) (PLA) have attracted much interest in recent years since they are biodegradable, thus can replace synthetic non-degradable materials. In this study, improvements of PHBV, mechanical, phase inversions, and rheological properties were investigated after blending with PLA in varying ratio’s. Three different blends of commercially available PLAs with 92–98% l-lactide units and one grade of PHB with 5% valerate content were blended using a micro-compounder at 175 °C. The composition of PHBV in blends ranged from 50% to 80%. With the addition of PLA, increases in the flexural strength and elastic modulus were observed for several blends, while minor to no changes were detected in the elongation at break and tensile strength as compared to pure PHBV material. Like many conventional plastics, the complex viscosity decreased with increasing rotational frequency due to decreasing entanglements and molecular weight. The complex viscosity with respect to time was very stable for the blends, but no improvements in the PHBV viscosity were observed with the addition of PLA at 170 °C. Three phase inversion models were used to predict the continuity of the blends, and the results showed both dual- and PLA-continuity phase for the blends. In summary, the mechanical results showed improvements in the tensile and flexural properties, while the rheological observation showed minor improvements in the complex viscosity for numerous concentrations.