Acrylonitrile Butadiene Styrene/Thermoplastic Polyurethane Blends for Material Extrusion Three-Dimensional Printing: Effects of Blend Composition on Printability and Properties.

Blend filaments of acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU) were prepared at different weight ratios, i.e., 100:0, 70:30, 50:50, 30:70, and 0:100, for FDM printing; the prepared filaments, with an average diameter of 2.77 ± 0.19 mm, were encoded as A100, A70T30, A50T50, A30T70, and T100, respectively. The properties and printability of the filaments were thoroughly investigated. The blend composition, as well as the printing parameters, were optimized to obtain the FDM-printed objects with a well-defined surface structure and minimized warpages. The glass transition temperatures of ABS and TPU in the blends were not much altered from those of the parent filaments, whereas the thermal degradation characteristics of the blend filaments still fell between those of the neat filaments. The fractured surfaces of the filaments, observed by SEM, appeared smoother when higher amounts of TPU integrated; the smoothest surface of the ABS-based filament was found in A30T70, indicating the well-compatible blend characteristic. This was also confirmed by its rheological behavior examined by a parallel plate rheometer at 225 °C. Not only was the printability of the filaments improved, but also the warpages of the 3D-printed specimens were decreased when increasing amount of TPU was incorporated into the filaments. Among the printed objects, the A30T70 specimen exhibited the evenest surface morphology with the lowest surface roughness value of 32.9 ± 13.2 nm and the most uniform and consistent linear printing structure when being fabricated at the nozzle temperature of 225 °C and the printing bed temperature of 60 °C. However, the incorporation of TPU into the filaments markedly cut down both strength and modulus values of the fabricated materials up to about half but assisted the printed articles to absorb more energy, demonstrating that this polymer served as a good and effective toughener for ABS.

Dual-Functional Drug Delivery System for Bisphosphonate-Related Osteonecrosis Prevention and Its Bioinspired Releasing Model and In Vitro Assessment.

Clindamycin (CDM)/geranylgeraniol (GGOH)-loaded plasma-treated mesoporous silica nanoparticles/carboxymethyl chitosan composite hydrogels (CHG60 and CHG120) were developed for the prevention of medication-related osteonecrosis of the jaw associated with bisphosphonates (MRONJ-B). The pore structure and performances of CHGs, e.g., drug release profiles and kinetics, antibacterial activity, zoledronic acid (ZA)-induced cytotoxicity reversal activity, and acute cytotoxicity, were evaluated. The bioinspired platform mimicking in vivo fibrin matrices was also proposed for the in vitro/in vivo correlation. CHG120 was further encapsulated in the human-derived fibrin, generating FCHG120. The SEM and µCT images revealed the interconnected porous structures of CHG120 in both pure and fibrin-surrounding hydrogels with %porosity of 75 and 36%, respectively, indicating the presence of fibrin inside the hydrogel pores, besides its peripheral region, which was evidenced by confocal microscopy. The co-presence of GGOH moderately decelerated the overall releases of CDM from CHGs in the studied releasing fluids, i.e., phosphate buffer saline-based fluid (PBB) and simulated interstitial fluid (SIF). The whole-lifetime release patterns of CDM, fitted by the Ritger-Peppas equation, appeared nondifferentiable, divided into two releasing stages, i.e., rapid and steady releasing stages, whereas the biphasic drug release patterns of GGOH were observed with Phase I and II releases fitted by the Higuchi and Ritger-Peppas equations, respectively. Notably, the burst releases of both drugs were subsided with lengthier durations (up to 10-12 days) in SIF, compared with those in PBB, enabling CHGs to elicit satisfactory antibacterial and ZA cytotoxicity reversal activities for MRONJ-B prevention. The fibrin network in FCHG120 further reduced and sustained the drug releases for at least 14 days, lengthening bactericidal and ZA cytotoxicity reversal activities of FCHG and decreasing in vitro and in ovo acute drug toxicity. This highlighted the significance of fibrin matrices as appropriate in vivo-like platforms to evaluate the performance of an implant.

Biodegradable Dual-Function Nanocomposite Hydrogels for Prevention of Bisphosphonate-Related Osteonecrosis of the Jaw.

This study presents the development of composite hydrogels, comprising a biodegradable polymer (carboxymethyl chitosan (CMCS or CM)) and a mixture of plasma-treated mesoporous silica nanoparticles (PMCM-41 or PM) and amine-functionalized mesoporous silica nanoparticles (NMCM-41 or NM), coloaded with a hydrophilic antibiotic (clindamycin hydrochloride (CDM or C)) and a poorly water-soluble compound (geranylgeraniol (GGOH or G)) for prevention of bisphosphonate-related osteonecrosis of the jaw (BRONJ). The CG-loaded hydrogel stabilities were better maintained when CDM-preloaded PMCM-41 and NMCM-41 were initially used and governed by weight ratios of CDM-loaded PMCM-41 to NMCM-41 and CDM quantity utilized. 5PM240C-1NM-CM demonstrated the best CDM-loaded hydrogel for GGOH postloading. The scanning electron microscopy (SEM) and X-ray microcomputer-tomography (µCT) images of 5PM240C-1NM-CM revealed a porous structure with homogeneously distributed nanoparticles. Two GGOH-loaded 5PM240C-1NM-CM hydrogels were generated after GGOH loadings. Their biphasic drug release profiles were fitted by Ritger-Peppas and Hixson-Crowell models. The copresence of GGOH could hinder CDM releases, while GGOH was released with a slower rate. The hydrogels prolonged the CDM and GGOH releases up to 9 days. They possessed antibacterial activities against Streptococcus sanguinis for up to 14 days and satisfactorily provided good cytoprotection against zoledronic acid for osteoclastic and osteoblastic progenitors, thus preserving a pool of viable progenitor cells that had the capacity to differentiate into mature osteoclasts and osteoblasts in vitro, suggesting their potential local application for prevention of BRONJ.

Chondrogenic Differentiation of Human Mesenchymal Stem Cells and Macrophage Polarization on 3D-Printed Poly(ε-caprolactone)/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Blended Scaffolds with Different Secondary Porous Structures.

This study was aimed to evaluate the chondrogenic differentiation of human mesenchymal stem cells (hMSCs) and polarization of THP-1-derived macrophages cultured on poly(ε-caprolactone) (PC)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PH) blended scaffolds with dual primary (PP) and secondary (SP) pores, which were fabricated via a 3D printing technique, i.e., fused deposition modeling, followed by a salt-leaching process at 50 °C for varied times, i.e., 15, 30, and 60 min. Sodium chloride (SC), a porogen, was initially incorporated in the blend at varied weight percentages, i.e., 0, 25, and 50%, whereas 1 M NaOH solution and deionized water were used as salt-leaching agents. To elucidate the surface properties of the developed scaffolds, directly governed by the amount of the salt originally mixed and the salt-leaching efficiency, several characterization techniques, e.g., scanning electron microscopy, X-ray microcomputed tomography, mercury intrusion porosimetry, atomic force microscopy, and contact angle measurement, were used. Meanwhile, the salt-leaching efficiency was determined by means of weight loss measurement and thermogravimetric analysis. It was found that the alkaline solution could satisfactorily leach out the salt particles in 60 min with a mild etching of the polymer framework. The most immensely and homogeneously pitted filament surface was observed in the NaOH-treated scaffold initially integrated with 50% salt, i.e., 60B_PC/PH/50SC; the SP structure was mostly open and interconnected. The size of most of micropores was about 0.14 µm. With its suitable microsurface roughness and hydrophilicity, 60B_PC/PH/50SC could properly support the initial attachment and lamellipodia formation of hMSCs, which was favorable for chondrogenesis. Consequently, a significantly increased ratio of glycosaminoglycans/deoxyribonucleic acid and a superior expression of the COL2A1 gene were detected when cells were grown on this material. Although 60B_PC/PH/50SC induced the macrophages to secrete a slightly high level of IL-1ß during the first few days of culture, the polarized M1 cells could return to a nearly normal stage at Day7, suggesting no unfavorable chronic inflammation caused by the material.

A novel modified culture medium for enhancing redifferentiation of chondrocytes for cartilage tissue engineering applications.

The dedifferentiation of articular chondrocytes during in vitro expansion deteriorates the hyaline cartilage regeneration. Many approaches have been developed to enhance the redifferentiation of chondrocytes. In this study, a new and effective protocol to improve the redifferentiation of porcine chondrocytes in a pellet form was established. Pellets were initially treated in the modified culture media containing ternary mixtures, binary mixtures, or single reagents of sodium citrate (SCi), sodium chloride (SCh), and ethylenediaminetetraacetic acid (EDTA) at varied concentrations during the first 3 days of culture, followed by a normal culture medium until 21 days. Viability, proliferation, cartilaginous gene expression, extracellular matrix formation, and morphology of treated cell pellets were comparatively examined. Chondrocytes exposed to SCi, SCh, and EDTA individually or in combinations of two or three chemicals were non-cytotoxic when the concentration ranges of the chemicals were 1.83-2.75, 5.00-7.50, and 1.00-1.50 mM, respectively. Cells treated with the modified media containing EDTA alone and EDTA-containing mixtures enhanced glycosaminoglycan production as well as upregulated cartilaginous gene expression, despite their low proliferation rates. Overall, when all three reagents were in use, a pronounced synergistic effect on the activations of glycosaminoglycan accumulation and type II collagen production was explicitly observed at most, particularly when cells were cultured in the medium containing SCi, SCh, and EDTA at concentrations of 2.20, 6.00, and 1.20 mM, respectively. With a use of this protocol, the redifferentiation of articular chondrocytes for regeneration of hyaline cartilage for tissue engineering applications could be readily achieved.

Antibacterial and osteogenic activities of clindamycin-releasing mesoporous silica/carboxymethyl chitosan composite hydrogels.

Conventional treatment of jaw bone infection is often ineffective at controlling bacterial infection and enhancing bone regeneration. Biodegradable composite hydrogels comprised of carboxymethyl chitosan (CMCS) and clindamycin (CDM)-loaded mesoporous silica nanoparticles (MCM-41), possessing dual antibacterial activity and osteogenic potency, were developed in the present study. CDM was successfully loaded into both untreated and plasma-treated MCM-41 nanoparticles, denoted as (p)-MCM-41, followed by the incorporation of each of CDM-loaded (p)-MCM-41 into CMCS. The resulting CDM-loaded composite hydrogels, (p)-MCM-41-CDM-CMCS, demonstrated slow degradation rates (about 70% remaining weight after 14-day immersion), while the CDM-free composite hydrogel entirely disintegrated after 4-day immersion. The plasma treatment was found to improve drug loading capacity and slow down initial drug burst effect. The prolonged releases of CDM from both (p)-MCM-41-CDM-CMCS retained their antibacterial effect against Streptococcus sanguinis for at least 14 days in vitro. In vitro assessment of osteogenic activity showed that the CDM-incorporated composite hydrogel was cytocompatible to human mesenchymal stem cells (hMSCs) and induced hMSC mineralization via p38-dependent upregulated alkaline phosphatase activity. In conclusion, novel (p)-MCM-41-CDM-CMCS hydrogels with combined controlled release of CDM and osteogenic potency were successfully developed for the first time, suggesting their potential clinical benefit for treatment of intraoral bone infection.

Geranylgeraniol prevents zoledronic acid-mediated reduction of viable mesenchymal stem cells via induction of Rho-dependent YAP activation.

Long-term use of zoledronic acid (ZA) increases the risk of medication-related osteonecrosis of the jaw (MRONJ). This may be attributed to ZA-mediated reduction of viable mesenchymal stem cells (MSCs). ZA inhibits protein geranylgeranylation, thus suppressing cell viability and proliferation. Geranylgeraniol (GGOH), which is a naturally found intermediate compound in the mevalonate pathway, has positive effects against ZA. However, precise mechanisms by which GGOH may help preserve stem cell viability against ZA are not fully understood. The objective of this study was to investigate the cytoprotective mechanisms of GGOH against ZA. The results showed that while ZA dramatically decreased the number of viable MSCs, GGOH prevented this negative effect. GGOH-rescued ZA-exposed MSCs formed mineralization comparable to that produced by normal MSCs. Mechanistically, GGOH preserved the number of viable MSCs by its reversal of ZA-mediated Ki67+ MSC number reduction, cell cycle arrest and apoptosis. Moreover, GGOH prevented ZA-suppressed RhoA activity and YAP activation. The results also established the involvement of Rho-dependent YAP and YAP-mediated CDK6 in the cytoprotective ability of GGOH against ZA. In conclusion, GGOH preserves a pool of viable MSCs with osteogenic potency against ZA by rescuing the activity of Rho-dependent YAP activation, suggesting GGOH as a promising agent and YAP as a potential therapeutic target for MRONJ.

Intrinsic Cellular Responses of Human Wharton's Jelly Mesenchymal Stem Cells Influenced by O2-Plasma-Modified and Unmodified Surface of Alkaline-Hydrolyzed 2D and 3D PCL Scaffolds.

Polycaprolactone (PCL), a hydrophobic-degradable polyester, has been widely investigated and extensively developed, to increase the biocompatibility for tissue engineering. This research was the first trial to evaluate the intrinsic biological responses of human Wharton's Jelly Mesenchymal Stem Cells (hWJMSCs) cultured on alkaline hydrolysis and low-pressure oxygen plasma modified 2D and 3D PCL scaffolds, without adding any differentiation inducers; this has not been reported before. Four types of the substrate were newly established: 2D plasma-treated PCL (2D-TP), 2D non-plasma-treated PCL (2D-NP), 3D plasma-treated PCL (3D-TP), and 3D non-plasma-treated PCL (3D-NP). Physicochemical characterization revealed that only plasma-treated PCL scaffolds significantly increased the hydrophilicity and % oxygen/carbon ratio on the surfaces. The RMS roughness of 3D was higher than 2D conformation, whilst the plasma-treated surfaces were rougher than the non-plasma treated ones. The cytocompatibility test demonstrated that the 2D PCLs enhanced the initial cell attachment in comparison to the 3Ds, indicated by a higher expression of focal adhesion kinase. Meanwhile, the 3Ds promoted cell proliferation and migration as evidence of higher cyclin-A expression and filopodial protrusion, respectively. The 3Ds potentially protected the cell from apoptosis/necrosis but also altered the pluripotency/differentiation-related gene expression. In summary, the different configuration and surface properties of PCL scaffolds displayed the significant potential and effectiveness for facilitating stem cell growth and differentiation in vitro. The cell-substrate interactions on modified surface PCL may provide some information which could be further applied in substrate architecture for stem cell accommodation in cell delivery system for tissue repair.

Chondrogenic phenotype in responses to poly(ɛ-caprolactone) scaffolds catalyzed by bioenzymes: effects of surface topography and chemistry.

Biodegradable poly(ε-caprolactone) (PCL) has been increasingly investigated as a promising scaffolding material for articular cartilage tissue repair. However, its use can be limited due to its surface hydrophobicity and topography. In this study, 3D porous PCL scaffolds fabricated by a fused deposition modeling (FDM) machine were enzymatically hydrolyzed using two different biocatalysts, namely Novozyme®435 and Amano lipase PS, at varied treatment conditions in a pH 8.0 phosphate buffer solution. The improved surface topography and chemistry of the PCL scaffolds were anticipated to ultimately boost the growth of porcine articular chondrocytes and promote the chondrogenic phenotype during cell culture. Alterations in surface roughness, wettability, and chemistry of the PCL scaffolds after enzymatic treatment were thoroughly investigated using several techniques, e.g., SEM, AFM, contact angle and surface energy measurement, and XPS. With increasing enzyme content, incubation time, and incubation temperature, the surfaces of the PCL scaffolds became rougher and more hydrophilic. In addition, Novozyme®435 was found to have a higher enzyme activity than Amano lipase PS when both were used in the same enzymatic treatment condition. Interestingly, the enzymatic degradation process rarely induced the deterioration of compressive strength of the bulk porous PCL material and slightly reduced the molecular weight of the material at the filament surface. After 28 days of culture, both porous PCL scaffolds catalyzed by Novozyme®435 and Amano lipase PS could facilitate the chondrocytes to not only proliferate properly, but also function more effectively, compared with the non-modified porous PCL scaffold. Furthermore, the enzymatic treatments with 50 mg of Novozyme®435 at 25 °C from 10 min to 60 min were evidently proven to provide the optimally enhanced surface roughness and hydrophilicity most significantly favorable for induction of chondrogenic phenotype, indicated by the greatest expression level of cartilage-specific gene and the largest production of total glycosaminoglycans.

PCL/PHBV blended three dimensional scaffolds fabricated by fused deposition modeling and responses of chondrocytes to the scaffolds.

In this study, poly(ε-caprolactone)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PCL/PHBV) blended porous scaffolds were fabricated by fused deposition modeling (FDM). PCL/PHBV filaments, initially prepared at different weight ratios, that is, 100/0, 75/25, 50/50, and 25/75, were fabricated by the lay-down pattern of 0/90/45/135° to obtain scaffolds with dimension of 6.0 × 6.0 × 2.5 mm3 and average filament diameters and channel sizes in the ranges of 370-390 µm and 190-210 µm, respectively. To enhance the surface hydrophilicity of the materials, the scaffolds were subsequently subjected to a low pressure oxygen plasma treatment. The untreated and plasma-treated scaffolds were comparatively characterized, in terms of surface properties, mechanical strength, and biological properties. From SEM, AFM, water contact angle, and XPS results, the surface roughness, wettability, and hydrophilicity of the blended scaffolds were found to be enhanced after plasma treatment, while the compressive strength of the scaffolds was scarcely changed. It was, however, found to increase with an increasing content of PHBV incorporated. The porcine chondrocytes exhibited higher proliferative capacity and chondrogenic potential when being cultured on the scaffolds with greater PHBV contents, especially when they were plasma-treated. The PCL/PHBV scaffolds were proven to possess good physical, mechanical, and biological properties that could be appropriately used in articular cartilage regeneration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1141-1150, 2017.

Osteoinduction of stem cells by collagen peptide-immobilized hydrolyzed poly(butylene succinate)/ß-tricalcium phosphate scaffold for bone tissue engineering.

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)/ß-tricalcium phosphate (HPBSu/TCP) scaffolds. PBSu/TCP (80:20) scaffolds were fabricated by a supercritical CO2 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.

In-vitro responses of T lymphocytes to poly(butylene succinate) based biomaterials.

BACKGROUND: Polybutylene succinate (PBSu) and PBSu/ß-tricalcium phosphate (TCP) composites are biocompatible and good candidates as bone graft materials. However, little is known about the responses of T lymphocytes to these biomaterials, which play an important role in the success of bone grafting. METHODS: Activated T lymphocytes were cultured onto 32 mm diameter films (PBSu/TCP films), that had previously been placed in 6-well culture plates, for 8, 24 and 72 hours. A plastic-well culture plate was used as a control surface. The effects of PBSu-based biomaterials on T lymphocytes were examined by the using flow cytometry and reverse-transcription polymerase chain reaction. RESULTS: These biomaterials were non-toxic to T lymphocytes, allowing their normal DNA synthesis and activation. All materials induced only transient activation of T lymphocytes, which existed no longer than 72 hours. Proportions of four main CD4/CD8 T lymphocyte subpopulations were not affected by these biomaterials. Moreover, PBSu and PBSu/TCP significantly suppressed the expression of IL-1ß and IL-6 genes by 15-35% and 21-26%, respectively. In contrast, a PBSu/TCP composite (at PBSu:TCP=60:40) significantly stimulated the expression of IL-10 and IL-13 genes by 17% and 19%, respectively. CONCLUSIONS: PBSu and PBSu/TCP composites were non-toxic to T lymphocytes and did not induce unfavorable responses of T lymphocytes. The tested biomaterials down-regulated key proinflammatory cytokine genes and up-regulated anti-inflammatory cytokine genes in T lymphocytes. These suggest that the biomaterials studied are good candidates as bone graft materials.

In vitro human chondrocyte culture on plasma-treated poly(glycerol sebacate) scaffolds.

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.

Enhancement of chondrocyte proliferation, distribution, and functions within polycaprolactone scaffolds by surface treatments.

Enhancement of porcine chondrocyte growth, distribution and functions within polycaprolactone (PCL) scaffolds was attempted using alkaline hydrolysis and oxygen plasma treatment. The hydrolysis of PCL was performed either before or after scaffold fabrication in the preparations of pre-hydrolyzed PCL (pre-HPCL) or post-HPCL scaffolds, respectively. The PCL, pre-HPCL, and post-HPCL scaffolds were subsequently plasma-treated to yield plasma-treated PCL, plasma-treated pre-HPCL, and plasma-treated post-HPCL scaffolds, respectively. All scaffolds were comparatively characterized, in terms of surface morphology, hydrophilicity, and atomic composition using scanning electron microscopy, contact angle measurement and X-ray photoelectron spectroscopy, respectively. The interactions of chondrocytes with individual scaffolds were assessed, in terms of cartilage-gene expression and cartilaginous matrix production using reverse transcription polymerase chain reaction analysis and glycosaminoglycans (GAGs) assay, respectively. The cell infiltration and cartilaginous matrix distribution were investigated by histological and immunofluorescence analysis. The results revealed that the plasma treatment exhibited a more prominent effect on the enhancement of surface roughness and hydrophilicity of the scaffolds than the alkaline hydrolysis. The scaffolds subjected to both surface treatments stimulated the cells to secret more GAGs and type II collagen. The sequence of hydrolysis of PCL also evidently played a crucial role in the hydrophilicity of the materials and the cartilage-gene expression and cartilaginous matrix production of the cultured chondrocytes. The hydrolysis of PCL prior to the fabrication, followed by the oxygen plasma treatment of the resulting fabricated scaffold, yielded plasma-treated pre-HPCL scaffold with homogeneous hydrophilic characteristics all over the material. Consequently, the cells could proliferate well, infiltrate most deeply and ultimately produce the highest amounts of the cartilage-specific substances throughout this scaffold.

Stem cell adhesion and proliferation on hydrolyzed poly(butylene succinate)/ß-tricalcium phosphate composites.

Although poly(butylene succinate)/ß-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.

Enhanced osteogenic activity of a poly(butylene succinate)/calcium phosphate composite by simple alkaline hydrolysis.

Bone engineering offers the prospect of alternative therapies for clinically relevant skeletal defects. Poly(butylene succinate) (PBSu) is a biodegradable and biocompatible polyester which may possess some limitations in clinical use due to its hydrophobicity. In order to overcome these limitations and increase the bioactivity, a simple and convenient surface hydrolysis of PBSu, PBSu/hydroxyapatite and PBSu/ß-tricalcium phosphate (TCP) films was performed. The resulting surfaces (i.e., HPBSu, HPBSu/HA and HPBSu/TCP) were tested for their physicochemical property, biocompatibility and osteogenic potency. The results showed that surface hydrolysis significantly increased surface roughness and hydrophilicity of the composites, with the HPBSu/TCP possessing the most pronounced results. All the materials appeared to be biocompatible and supported in vitro growth and osteoblast differentiation of hMSCs, and the alkaline hydrolysis significantly enhanced the hMSC cell proliferation and the osteogenic potency of PBSu/TCP compared with the non-hydrolyzed sample. In conclusion, the HPBSu/TCP possessed better hydrophilicity, biocompatibility and osteogenic potency in vitro, suggesting that this simple and convenient alkaline hydrolysis could be used to augment the biological property of PBSu-based composites for bone engineering in vivo.

Comparative multifunctional properties of partially carboxymethylated cotton gauze treated by the exhaustion or pad-dry-cure methods.

A commercial cotton gauze was modified by partial carboxymethylation using both exhaustion and pad-dry-cure methods, and varying the reaction time and concentration of monochloroacetic acid and sodium hydroxide to obtain the relative degree of carboxymethylation differently. For each experiment, relative value of the degree of substitution (DSrel) of the modified cotton was evaluated and compared with whole blood clotting time, absorption and retention of chitosan and silver nitrate solutions, antibacterial activity, and physical properties of whiteness, bursting strength and water absorption. Carboxymethylated cotton gauze with a higher DSrel value showed a better absorption of chitosan and silver nitrate solutions and retained these two solutions for a much longer time than those of unmodified cotton gauze or carboxymethylated cotton gauze at a lower DSrel. Carboxymethylated cotton gauzes obtained from exhaustion method showed significant antibacterial activity and higher bursting strength and less affected whiteness index than those treated by pad-dry-cure method.

Fibroblast interaction with carboxymethylchitosan-based hydrogels.

The interaction between L929 cells and carboxymethylchitosan (CM-chitosan)-based hydrogels, hydrogels from pure CM-chitosan and its blends, was examined in this study. Cytotoxicity of all materials was also assessed. The cellular morphology and behavior on the surfaces of the hydrogels were observed by scanning electron microscopy (SEM). The effects of various parameters, e.g., type and content of blended polymers, surface structure of hydrogels, and steaming condition used for the preparation of the hydrogels, on the cell-material response were investigated. The results of the cytotoxicity test revealed that all hydrogels were non-cytotoxic. The SEM micrographs demonstrated that the cells proliferated and spread onto a porous CM-chitosan sample. Better cell spreading was found on a flat surface of a CM-chitosan film. Rounded cells were observed when poly(vinyl alcohol) (PVA) was incorporated into CM-chitosan. Fewer cells were found when the content of PVA increased. Spherical clusters of the aggregated cells existed in the blends with ultra high viscosity carboxymethylcellulose (CM-cellulose). In contrast, with the use of low viscosity CM-cellulose, the cells appeared more spreading. The attached cells on the CM-chitosan film steamed at the highest temperature and longest period appeared to spread the most among all tested steaming conditions.