Although poly(butylene succinate)/β-tricalcium phosphate (PBSu/TCP) composites are biocompatible and allow the growth and osteogenic differentiation of stem cells, cell attachment and adhesion to the PBSu-based substrates is often limited. To enhance cell adhesion and proliferation, we used a sodium hydroxide (NaOH) hydrolysis technique to generate a different degree of roughness on PBSu/TCP substrates with different PBSu:TCP ratios. The results showed that NaOH hydrolysis increased surface roughness of PBSu/TCP substrates in a concentration-dependent manner. Substrates with higher ratios of TCP:PBSu provided more porous topography after NaOH hydrolysis, with a substrate containing 40 wt % TCP (PBSu/TCP-6040) hydrolyzed with 1.5M NaOH (HPBSu/TCP-6040-1.5) showing the highest degree of roughness. As with the roughness, PBSu/TCP surface hydrophilicity was positively affected by the increasing NaOH concentration and TCP incorporation. Stem cells adhered best on HPBSu/TCP-6040-1.5 with three-dimensionally elongated cell extensions. Moreover, the HPBSu/TCP-6040-1.5 substrate most significantly facilitated stem cell actin cytoskeleton reorganization and vinculin-positive focal adhesion formation when compared with the other substrates tested. HPBSu/TCP-6040-1.5 also demonstrated the greatest increase in cell proliferation when compared with the other substrates studied. In conclusion, the results have shown that among various substrates tested, HPBSu/TCP-6040-1.5 provided the best support for stem cell adhesion and proliferation, suggesting its potential use in bone engineering.

Lignin and melanin are aromatic biopolymers that are contained in large amounts in plants and animals. Biopolymers containing hydrogen bond donor (HBD) moieties (phenols, diols, amino acids, etc.) are sustainable...

The synthesis of cyclic carbonates by cycloaddition of CO2 to epoxides is a convenient non-reductive strategy to valorize carbon dioxide. Biphasic chemistry is an emerging and convenient approach to carry...

Some novel polymeric fibrous nonwoven meshes have been processed from solution blends of poly(L-lactide-cocaprolactone), P(LL-CL), and gelatin for use as biodegradable porous scaffolds in articular cartilage tissue engineering. P(LL-CL) copolymers with LL:CL compositions ranging from 50:50 to 80:20 mol% were synthesized via the bulk ring-opening copolymerization of L-lactide (LL) and e-caprolactone (CL) using tin(II) octoate, Sn(Oct) 2 , as the initiator. To make the hydrophobic P(LL-CL) more hydrophilic for cell culture, it was solution blended with gelatin using trifluoroethanol as a common solvent to give P(LL-CL):gelatin contents in the final scaffolds ranging from 70:30 to 95:5 wt%. Two different processing methods were used: electrospinning and wet spinning. Although electrospinning gave a more uniform mesh of nanosized fibers, the nonwoven mesh from wet spinning with its much larger pores and greater pliability was found to be more suitable for water absorption, cell infiltration and shape-forming. Scanning electron micrographs of the scaffolds from the two techniques are compared. From the results obtained, the wet-spun P(LL-CL)50:50/gelatin 95:5 scaffold gave the best combination of properties. In particular, the 5% gelatin content resulted in a fivefold increase in the scaffold's equilibrium water uptake from about 10% to over 50% by weight. POLYM. ENG. SCI., 57:875-882, a LL:CL ratios are the comonomer feeds (mol%) used in synthesis. b LL:CL ratios are the actual copolymer compositions (mol%) from 1 H-NMR. c PDI 5 polydispersity index 5 M w /M n (where M w and M n have units of g/mol). d DSC data obtained from second heating scan. e T g determined by dynamic mechanical analysis (DMA): temperature scan from 280 to 1008C at 28C/min, frequency 1 Hz, on thin film sample in tension mode. f 50:50 copolymer was completely amorphous with no observed T c or T m transitions.

The catalytic cycloaddition of CO2 to epoxides to afford cyclic carbonates as useful monomers, intermediates, solvents, and additives is a continuously growing field of investigation as a way to carry out the atom-economic conversion of CO2 to value-added products. Metal-free organocatalytic compounds are attractive systems among various catalysts for such transformations because they are inexpensive, nontoxic, and readily available. Herein, we highlight and discuss key advances in the development of polymer-based organocatalytic materials that match these requirements of affordability and availability by considering their synthetic routes, the monomers, and the supports employed. The discussion is organized according to the number (monofunctional versus bifunctional materials) and type of catalytically active moieties, including both halide-based and halide-free systems. Two general synthetic approaches are identified based on the postsynthetic functionalization of polymeric supports or the copolymerization of monomers bearing catalytically active moieties. After a review of the material syntheses and catalytic activities, the chemical and structural features affecting catalytic performance are discussed. Based on such analysis, some strategies for the future design of affordable and readily available polymer-based organocatalysts with enhanced catalytic activity under mild conditions are considered.

Porous poly(glycerol sebacate) (PGS) scaffolds were prepared using a salt leaching technique and subsequently surface modified by a low oxygen plasma treatment prior to the use in the in vitro culture of human chondrocytes. Condensation polymerization of glycerol and sebacic acid used at various mole ratios, i.e. 1:1, 1:1.25, and 1:1.5, was initially conducted to prepare PGS prepolymers. Porous elastomeric PGS scaffolds were directly fabricated from the mixtures of each prepolymer and 90% (w/w) NaCl particles and then subjected to the plasma treatment to enhance the surface hydrophilicity of the materials. The properties of both untreated and plasma-treated PGS scaffolds were comparatively evaluated, in terms of surface morphology, surface chemical composition, porosity, and storage modulus using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy, micro-computed tomography, and dynamic mechanical analysis, respectively. The responses of chondrocytes cultured on individual PGS scaffolds were assessed, in terms of cell proliferation and ECM production. The results revealed that average pore sizes and porosity of the scaffolds were increased with an increasing sebacic acid concentration used. The storage moduli of the scaffolds were raised after the plasma treatment, possibly due to the further crosslinking of PGS upon treatment. Moreover, the scaffold prepared with a higher sebacic acid content demonstrated a greater capability of promoting cell infiltration, proliferation, and ECM production, especially when it was plasma-treated; the greatest HA, sGAG, uronic acid, and collagen contents were detected in matrix of this scaffold. The H & E and safranin O staining results also strongly supported this finding. The storage modulus of the scaffold was intensified after incubation with the chondrocytes for 21 days, indicating the accretion and retention of matrix ECM on the cell-cultured scaffold.

Bone substitute is a therapeutic approach to treat bone abnormalities. A scaffold serves mainly as osteoconductive elements. To facilitate a better biological performance, short collagen peptide was immobilized onto hydrolyzed poly(butylene succinate)/β-tricalcium phosphate (HPBSu/TCP) scaffolds. PBSu/TCP (80:20) scaffolds were fabricated by a supercritical CO technique, hydrolyzed with 0.6 M NaOH and conjugated with short collagen peptide tagged with or without red fluorescence. The surface morphology and porous structure of scaffolds were characterized by scanning electron microscopy and micro-computed tomography. Human mesenchymal stem cells were cultured onto the scaffolds and examined for osteogenic differentiation and biomineralization in vitro by means of alkaline phosphatase activity, alizarin red staining, and reverse transcription-polymerase chain reaction. The PBSu/TCP and HPBSu/TCP scaffolds were successfully prepared. Scanning electron microscopy and micro-computed tomography results showed that the porosity was distributed throughout the scaffolds with the pore sizes in the range of 250-900 µm. Fluorescence microscopy demonstrated retention of tagged short collagen peptide on the scaffold. Mesenchymal stem cells adhered and grew well on the material. Under osteogenic induction, cells cultured on the short collagen peptide -immobilized scaffold significantly produced a greater amount of alkaline phosphatase activity and positive mineralization than those cultured on the control scaffold. The present results have shown that the short collagen peptide-immobilized HPBSu/TCP scaffold enhanced osteoinduction and biomineralization of stem cell-derived osteoblasts, possibly via stimulation of alkaline phosphatase activity. This suggests the potential use of osteogenic peptide-immobilized material in bone tissue engineering for correcting bone defects.

Although attempts have been made to immobilize dual short peptides on a biomaterial surface, the optimization, characterization and functional analysis of the peptide immobilization onto poly(buthylene succinate)/β-tricalcium phosphate (PBSu/TCP) composites have not yet been reported. The present study was, therefore, carried out to optimize and characterize the dual immobilization of type I collagen short peptide (COLsp) and bone morphogenetic protein-2 short peptide (BMP-2sp) onto hydrolyzed PBSu/TCP (HPBSu/TCP) composites, and the bioactivity of the resulting dual peptide-immobilized surfaces was also determined in vitro. The results demonstrated that sequential immobilization of the dual short peptides was successfully established. Each of the peptides was chemically bound to the 1.5 M NaOH-treated composite (with the PBSu to TCP weight ratio of 60:40) (HPBSu/TCP-6040–1.5); bright red fluorescence of COLsp (25 µM) and vividly green fluorescence of BMP-2sp (50 µM) were individually observed explicitly on the dual peptide-immobilized material. As a result, the HPBSu/TCP-6040–1.5 composite film conjugated with both 25 µM Col I and 50 µM BMP-2 was examined for its osteogenic efficacy. The results showed that COLsp/BMP-2sp-immobilized HPBSu/TCP composite significantly enhanced hMSC proliferation as well as osteoblast differentiation of hMSCs under osteogenic induction. Most importantly, COLsp/BMP-2sp-immobilized HPBSu/TCP composite induced biomineralization in the absence of any additional osteogenic stimulus. The present study has successfully demonstrated the sequential immobilization of the dual short peptides, i.e., COLsp and BMP-2sp, on HPBSu/TCP surface, with each short peptide being chemically bound to the hydrolyzed composite surface. The COLsp/BMP-2sp-immobilized HPBSu/TCP film possessed the bioactivities of the respective full-length proteins by stimulating hMSC proliferation, osteoblast differentiation and, most importantly, mineralization without the requirement of exogenous osteogenic supplements. This suggests highly improved performance of the biologically responsive HPBSu/TCP composite and thus its potential use in bone tissue engineering.