Journal of Bioactive and Compatible Polymers recent issues

Heparinized Micropatterned Surfaces for the Spatial Control of Human Mesenchymal Stem Cells

Fri, 23 Oct 2009 04:11:33 PDT

In this study, a heparinized micropattern surface was prepared for the spatial control of human mesenchymal stem cells (hMSCs) that can differentiate into the desired tissues. Poly(styrene-co-vinylbenzyl N,N-diethyl-dithiocarbamate) (poly(ST-co-VBDC)) was synthesized as a photoreactive polymer; poly(ethylene glycol) methacrylate (PEGMA) was polymerized on the poly(ST-co-VBDC) coated surface by UV irradiation. XPS spectra revealed the residual DC moieties on the PEGMA-grafted surface and the linear chain growth of PEGMA was monitored according to irradiation time. After chemical immobilization of heparin onto this PEGMA surface, surface micropatterning was carried out by additional photopolymerization of PEGMA using a photomask. After incubation for 4 hour, the hMSCs adhered to the heparinized surface, while the hydrophilic PEGMA surface demonstrated no cell adhesion even after basic fibroblast growth factor (bFGF) treatment. Good alignment of hMSCs on the pattern-surface was distinctly observed along micron-sized grooves due to the presence of both heparin and bFGF. This heparinized micropattern surface can be used to study in vitro hMSCs responses with various heparin-binding growth factors in tissue engineering fields as well as cellular array for the spatial control of hMSCs.

Biomimetic Apatite-coated PCL Scaffolds: Effect of Surface Nanotopography on Cellular Functions

Beskardes, I. G., Gumusderelioglu, M. — Fri, 23 Oct 2009 04:11:33 PDT

In this study, polycaprolactone (PCL) scaffolds, consisting of agglomerated microspheres with nanotopographic surface structures, were fabricated by the freeze-drying method. These scaffolds were coated with bone-like apatite by using a calcium phosphate solution similar to saturated simulated body fluid (10x SBF-like) in two different immersion periods (6 and 24 h). Scanning electron microscopic views of the 6-h treatment in 10x SBF-like solution showed formation of calcium phosphate nucleation sites on the PCL scaffolds, while the apatite particles formed characteristic cauliflower-like morphology after 24 h. The X-ray diffraction (XRD) data showed that the mineral phase was made of hydroxyapatite (HA). The osteogenic activity of untreated and SBF-treated PCL scaffolds was examined by pre-osteoblastic MC3T3 cell culture studies. Cells had attached and spread on both the PCL scaffolds and the 6-h SBF immersion-treated scaffolds.

Hydrogels Based on Carboxymethylcellulose and Gelatin for Inclusion and Release of Chloramphenicol

Buhus, G., Popa, M., Desbrieres, J. — Fri, 23 Oct 2009 04:11:33 PDT

Hydrogels based on carboxymethylcellulose (CMC) and gelatin (GEL) crosslinked with glutaraldehyde were used to obtain interpenetrated— interconnecting polymer networks. They are designed to obtain controlled release polymeric drug systems. CMC and GEL were chosen for their biocompatibility and nontoxicity, which are compulsory conditions for polymers used in biomedical applications. By modifying the parameters of the crosslinking reaction, the obtained networks presented different crosslinking degrees and hence different swelling capacities. These properties determined the quantity of drug able to be loaded (0.25 g per gram of hydrogel). We obtained systems for which biologically active matter release was controlled by diffusion. The kinetics were zero-order during the major part of release period (~500 min). These systems improve the bactericide activity compared with free drugs.

Biodegradable Adhesives Composed of Human Serum Albumin and Organic Acid-based Crosslinkers with Active Ester Groups

Taguchi, T., Saito, H., Iwasashi, M., Sakane, M., Ochiai, N. — Fri, 23 Oct 2009 04:11:33 PDT

The organic acid-based crosslinkers trisuccinimidyl citrate (TSC), disuccinimidyl malate (DSM), and disuccinimidyl tartarate (DST) were combined with human serum albumin (HSA) to produce biodegradable solid— liquid-type adhesives, TSC-A, DSM-A, and DST-A. The bonding time of TSC-A, DSM-A, and DST-A was 15, 10, and 5 min, respectively, when the content of organic acid-based crosslinkers was 0.5 mmol and the HSA concentration was 44 w/v%. Five minutes after application of the adhesives, the DST-A adhesive had the greatest bonding strength (489.14 ± 93.06 kPa) compared with TSC-A (120.86 ± 73.83 kPa) and DSM-A (224.44 ± 79.53 kPa). The bonding strength of DSM-A and DST-A increased with increasing DSM or DST content up to 0.5 mmol, after that the bonding strength decreased. While, the bonding strength of the TSC-A adhesive was relatively low at any TSC content compared with the other adhesives. The bonding strength of DST-A with 0.3 mmol of DST increased with increasing HSA concentration up to 44 w/v%, and then decreased. The bonding strength of the DST-A adhesive was 3.2-fold greater than that of a commercial aldehyde-based adhesive and 6-fold greater than that of a fibrin-based adhesive. DST-A has excellent biocompatibility, bioabsorbability, and only mild tissue reaction in rat subcutaneous tissues.

Effects of Chitosan on Properties of Novel Human-like Collagen/Chitosan Hybrid Vascular Scaffold

Zhu, C., Fan, D., Ma, X., Xue, W., Yu, Y., Luo, Y., Liu, B., Chen, L. — Fri, 23 Oct 2009 04:11:33 PDT

Novel human-like collagen (HLC)/chitosan hybrid scaffolds were fabricated at blend ratios of 0%, 0.02%, 0.2% by crosslinking and freeze-drying process. The properties of the scaffolds were investigated, including morphology, mechanical strength, degradability, and cell biocompatibility. When the blend ratio was 0.02%, the morphology of the scaffolds was highly homogeneous with interconnected porous structure 46 ± 9 µm in size (SEM). The X-ray photoelectron spectroscopy analysis indicated intermolecular crosslinks between HLC and chitosan. The strain and stress of the scaffolds were 37.9 ± 3.3% and 309.7 ± 19.7 KPa, respectively. Human venous fibroblasts were expanded and seeded into the scaffolds in the density of 1 x 10⁵ cells/cm³ under static conditions. The cell morphology and proliferation were investigated using SEM, H&E, and MTT assay, which showed that the optimal content of the chitosan was signifcantly enhanced the cells adhesion, proliferation, and viability, compared to pure HLC, pure chitosan, and 0.2% chitosan/HLC scaffolds. These hybrid scaffolds appear to have favorable characteristics for vascular tissue engineering application.

Injectable Poly(ethylene glycol) Dimethacrylate-based Hydrogels with Hydroxyapatite

Zhou, Z., Yang, D., Nie, J., Ren, Y., Cui, F. — Tue, 08 Sep 2009 02:20:54 PDT

Injectable hydrogels are attractive materials for tissue engineering as they provide fast reaction rates, low heat release, and biocompatibility for cell proliferation and permanent interface with surrounding tissue. A series of injectable poly(ethylene glycol) dimethacrylate (PEGDMA) hydrogels with four different weight fractions of hydroxyapatite (HA) particles were prepared and thermal and mechanical properties evaluated. The cytocompatibility was assessed by examining the viability and morphology of human mesenchymal stem cells (hMSCs) seeded on the hydrogels. The in situ crosslink process displayed a vast decrease in the maximal temperature and an increase in the maximal temperature time. Cytocompatibility evaluation by MTT assay, scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) showed that the cells on the composite hydrogels possessed better viability and adherence than the hydrogels without HA. The results indicated that composite hydrogels have potential as injectable materials for tissue engineering application.

A Bilayer Hyaluronic Acid Wound Dressing to Promote Wound Healing in Diabetic Ulcer

Lin, Y.-K., Matsumoto, Y., Kuroyanagi, Y., Kagawa, S. — Tue, 08 Sep 2009 02:20:54 PDT

Several spongy wound dressings composed of various hyaluronic acid (HA) materials were developed: HA aqueous solution with cross-linking agent (epoxy compound (HAWC), without cross-linking agent (HAWOC), and combined bilayer material HAWC and HAWOC (2LHA). The microstructure, sensitivity to hyaluronidase, sensitivity to free radicals, in vitro cytotoxicity, healing potential on full-thickness defect on and diabetic ulcers were evaluated. Scanning electron micrograph views of all HA wound dressings showed an interconnected channel and high porosity structure. HAWOC was degraded rapidly in hyaluronidase and free radical solution. The in vitro cytotoxicity of HAWC was significantly (p<0.05) higher than other HA wound dressings and reduced the released amount of VEGF from human fibroblast. The HAWOC remarkably facilitated the formation of vascularized granulation tissue and provided a HA enrichment wound healing process of either a full-thickness defect or a diabetic ulcer. In contrast, the presence of un-degradable products of HAWC seemed to interfere dermal tissue restoration. Nevertheless, because of the fragile properties, rapid degradation and wound adhesion of HAWOC, the 2LHA should be developed for diabetic ulcer therapy.

Poly(Ethylene Glycol)-based Crosslinked Networks with Potential Multidrug Resistance 1 (MDR1) Protein Inhibition Effects

Santos-Roman, N., Mendez-Vega, J., Torres-Lugo, M. — Tue, 08 Sep 2009 02:20:54 PDT

Linear poly(ethylene glycol) based structures have emerged as possible inhibitors for the multidrug resistance (MDR) proteins and recognized as a major hurdle during drug absorption and distribution. In this report, PEG-based hydrogels were evaluated for transport enhancement of the known MDR1 substrate Rhodamine 123. The expression of the MDR1 protein was corroborated using an immunostaining technique. The results indicated that these hydrogels are capable of enhancing the transport of Rhodamine 123 up to 350%, most likely due to MDR1 inhibition. The length of the PEG tethered chain appears to play an important role on transport enhancement as well the concentration of PEG hydrogel. This was taken as evidence of a possible inhibition effect of the MDR1 protein. When compared to the known inhibitors, genistein and verapamil, the PEG hydrogels provided similar efflux ratio, but the transport enhancement was lower. This is the first evidence of the role of crosslinked PEG-based hydrogels as possible inhibitors of the MDR1 protein.

Posterolateral Spinal Fusion in Rabbits Using a RP-based PLGA/ TCP/Col/BMSCs-OB Biomimetic Grafting Material

Ma, X., Wu, X., Wu, Y., Liu, J., Xiong, Z., Lv, R., Yan, Y., Wang, J., Li, D. — Tue, 08 Sep 2009 02:20:55 PDT

Three-dimensional highly porous poly(DL-lactic-co-glycolic acid)/ tricalcium phosphate (PLGA/TCP) scaffolds were fabricated using a rapid prototyping technique (RP). The 3D rhombic lamellar PLGA/TCP carriers (20 mm x 20 mm x 3 mm) subsequently were coated with collagen type I (Col) to produce PLGA/TCP/Col composites. Both the RP-based PLGA/TCP scaffolds and the PLGA/TCP/Col composites were observed by scanning electron microscopy. Forty New Zealand white rabbits were equally randomized into 2 groups (group A and group B) and bilaterally underwent posterolateral intertransverse process arthrodesis at the L4—L5 level using the following graft materials: In group A, PLGA/TCP/Col/BMSCs-OB composites (on the right side, group A1, n = 20) and autogenous iliac bone grafts (on the left side, group A2, n = 20) were used; In group B, PLGA/TCP scaffolds plus fresh autogenous bone marrow (on the right side, group B1, n = 20) and PLGA/TCP scaffolds alone (on the left side, group B2, n = 20) were utilized. In group A1, rabbit bone marrow stromal cells (BMSCs) were isolated and cultured under the osteogenic conditions (BMSCs-OB). Structural PLGA/TCP/Col composites then were efficiently loaded with BMSCs-OB and cultured 5 days to make PLGA/TCP/ Col/BMSCs-OB biomaterials. Rabbits were sacrificed after 12-week follow-up and the spinal fusion were evaluated by a general observation, a manual palpation test, histological analyses and radiography. As a result, RP established PLGA/TCP scaffolds with appropriate biomaterial properties including satisfactory microstructure, inter-connectivity and porosity. Modifications to the structural highly porous PLGA/TCP scaffolds with Col (PLGA/TCP/Col) essentially increased the affinity of the carriers to seeding cells. In group A1, radiological evaluation revealed strong ability of new bone formation and bony fusion in the implanted sites and histological analyses showed highly cellular bone marrow between the newly formed trabecular bone was present in the fusion mass. In group A2, there was a reduced amount of newly formed bone. In group B1, only a few bony fusions were obtained. In group B2, PLGA/TCP scaffolds were biocompatible and biodegradable; whereas, no newly formed bone or bony fusion was found. Twelve weeks after surgery, spinal fusion rates in groups of A1, A2, B1, and B2 were 70.0%(14/20), 45.0%(9/20), 15.8%(3/19), and 0%(0/19), respectively. The rates of fusion were significantly higher in groups of A1 and A2 compared with groups of B1 and B2 (p<0.01), and there was no significant difference of fusion rate between group A1 and group A2 (p>0.05). Therefore, RP-based 3D PLGA/TCP/Col/BMSCs-OB biomaterial holds promise as a bone grafting substitute for spinal fusion. Our attempts may provide a novel method for biofabrication of the bionic construct.

Cryopreservation of Cells in 3D Constructs Based on Controlled Cell Assembly Processes

Sui, S., Wang, X., Liu, P., Yan, Y., Zhang, R. — Tue, 08 Sep 2009 02:20:55 PDT

Cryopreservation technology plays an important role in conserving three dimensional (3D) constructs containing cells. Besides preserving the characteristics of the construct, it can also save a lot of resources in many aspects, such as cell culture space, culture vessel, culture medium etc. Otherwise, the biological properties of the cells and the 3D geometrical configuration will disappear with the death of cells and breakage of configuration. Consequently, a cryopreservation method for the 3D construct fabricated with a controlled cell assembling technology was studied. 10% dimethylsulfoxide (DMSO) was incorporated into the adipose-derived stem cell (ADSC)/gelatin/ alginate/fibrinogen mixture before assembling. Results indicate that the 3D construct containing cells can be preserved below —80°C for more than 1 week. After the construct underwent the thawing process, cell viability and proliferation ability were regained. This technique holds potential to be used widely in tissue engineering and organ manufacturing fields.

Chitosan/Alginate Multilayer Scaffold Encapsulating Bone Marrow Stromal Cells In Situ on Titanium

Wu, M.-Y., Ning Chen, , Liu, L.-K., Hua Yuan, , Li, Q.-L., Chen, S.-H. — Wed, 01 Jul 2009 07:37:03 PDT

A biofilm-like scaffold with bone marrow stromal cells (BMSC) encapsulated in situ was constructed on a titanium surface using a layer-by-layer self-assembly technique for the potential application for dental or joint implant. The scaffold was formed by depositing a single layer of positively charged poly(L-lysine) on a negatively charged NaOH-treated titanium substrate, followed by alternate immersion into a negatively charged alginate—BMSC suspension and positively charged chitosan solution, respectively, and terminated a layer of chitosan. The cell-encapsulated scaffolds were evaluated by scanning electron microscopy and confocal laser scanning microscopy. The BMSC remained viable and grew well in the scaffold. This approach provides a method for the preparation of tissue engineering scaffold on titanium surfaces.

Biocompatible PEG Grafting on DLC-coated Nitinol Alloy for Vascular Stents

Wed, 01 Jul 2009 07:37:03 PDT

The surfaces of Nitinol (TiNi), a popular metal alloy for arterial stents were thin-coated with diamond-like carbon (DLC) and then grafted with poly(ethylene glycol) (PEG) to increase biocompatibility. The TiNi control, DLC-coated TiNi (TiNi—DLC), and the PEG-grafted TiNi—DLC (TiNi—DLC—PEG) surface characteristics and biocompatibility were evaluated. The hydrophilicity of the TiNi—DLC—PEG significantly increased and the amount of both oxygen and nitrogen on the TiNi—DLC—PEG also increased compared to the TiNi control and TiNi—DLC due to the grafted PEG. The ratio between albumin and fibrinogen was higher on the PEG-grafted surface than the other surfaces when tested with human blood components; the platelet adhesion decreased the most on the TiNi—DLC—PEG surface, indicating improved blood compatibility. For in vivo tests using a rat model, the samples that were implanted for 6 weeks formed fibrous tissue; the tissue layer was much thinner on the PEG-grafted sample than the other two groups. The present results indicate that PEG-grafted TiNi—DLC surface may be effective in enhancing biocompatibility of blood-contacting biomaterials including vascular stents.

Matrix Gene Expression in Dermal Fibroblasts Cultured on Hyaluronan-coated Polysulfone Membranes

Attia, J., Boumediene, K., Pujol, J.P., Valleton, J.M., Huet, E., Nguyen, Q.T. — Wed, 01 Jul 2009 07:37:03 PDT

Polysulfone (PSU) membranes, coated and uncoated hyaluronan (HA), were compared for their ability to allow dermal fibroblast express genes related to extracellular matrix synthesis and remodeling. Fibroblasts type I and type III collagens were studied on both types of membranes; only type I collagen was synthesized on control cultures in plastic Petri dishes, whereas type III collagen was also expressed on PSU membranes. Expression of metalloproteinase (MMP)1, MMP3, and MMP2 was enhanced on PSU and HA-coated PSU membranes, with a lower level of MMP2 on HA-covered membranes. These membranes promote fetal-like matrices that provide good support for skin wound healing as well as favor nonscarring tissue repair.

Rechargeable Antibacterial and Antifungal Polymeric Silver Sulfadiazines

Zhengbing Cao, , Xinbo Sun, , Yuyu Sun, , Hao Fong, — Wed, 01 Jul 2009 07:37:03 PDT

Poly(methyl methacrylate) (PMMA)-based rechargeable antibacterial and antifungal polymeric silver sulfadiazines were prepared by copolymerizing acryloyl sulfadiazine with methyl methacrylate and sequentially treating the copolymers with dilute silver nitrate aqueous solutions. The chemical structures of the samples were characterized by FT-IR, ¹H-NMR, XPS, and TGA analyses. On contact, the PMMA-based polymeric silver sulfadiazines provided 100% inactivation of 10⁸—10⁹ CFU/mL of Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Gram-positive bacteria) in 10 min, and Candida tropicalis (yeast) in 30 min. Kirby—Bauer test data indicated that the antibacterial and antifungal effects were achieved through contact kill; no silver ions leached out of the new copolymers. The antibacterial and antifungal functions were stable for at least 12 months under normal storage conditions. Silver nitrate treatments regenerated any lost of antibacterial and antifungal activity; this recharging can be repeated as needed to achieve long-term protection. These properties make the new PMMA-based polymeric silver sulfadiazines attractive candidates for a broad range of medical (orthopedic), dental, and other related applications to reduce the risks of bacterial and fungal contamination on high-touch/high-risk surfaces and foreign body-related infections.

Electroresponsive Polyacrylamide-grafted-xanthan Hydrogels for Drug Delivery

Kulkarni, R. V., Sa, B. — Wed, 01 Jul 2009 07:37:03 PDT

An electroresponsive drug delivery system was developed using poly(acrylamide-grafted-xanthan gum) (PAAm-g-XG) hydrogel for transdermal delivery of ketoprofen. The electrically sensitive PAAm-g-XG copolymer was synthesized by free radical polymerization under nitrogen atmosphere followed by alkaline hydrolysis. When a swollen PAAm-g-XG hydrogel was placed in between a pair of electrodes, deswelling of the hydrogel was observed in the vicinity of electrodes carrying the electric stimulus. The membrane-controlled drug delivery systems were prepared using drug-loaded PAAm-g-XG hydrogel as the reservoir and crosslinked with poly(vinyl alcohol) to form films as rate controlling membranes (RCM). The in vitro drug permeation study from the formulations was performed through excised rat abdominal skin. Drug permeation across the skin was greatly enhanced in the presence of electric stimulus as compared to passive diffusion and was found to be dependent upon the applied electric current strength and crosslink density of RCM. A pulsated pattern of drug release was observed as the electric stimulus was switched `on' and `off.' The skin histopathology study demonstrated that, after the application of an electrical stimulus, there were changes in the structure of stratum corneum and cell structure. These PAAm-g-XG hydrogel could be useful as transdermal drug delivery systems actuated by an electric signal to provide on-demand release of drugs.

Perspectives on: Supercritical Fluid Technology for 3D Tissue Engineering Scaffold Applications

Duarte, A. R. C., Mano, J. F., Reis, R. L. — Wed, 01 Jul 2009 07:37:03 PDT

Supercritical fluid technology has proven to be useful for many pharmaceutical applications and is now emerging as an alternative to conventional processes for the preparation of 3D structures and injectable particles suitable to be used in regenerative medicine. A current overview of the basic principles underlying supercritical fluid technology, the state of the art and future potential of this technology are presented.

Rapid Prototyping a Double-layer Polyurethane--collagen Conduit and its Schwann Cell Compatibility

Tongkui Cui, , Xiaohong Wang, , Yongnian Yan, , Renji Zhang, — Tue, 19 May 2009 02:53:08 PDT

A new double-layer conduit that combined an outer synthetic polyurethane (PU) layer and inner natural collagen layer was fabricated via a double-nozzle low-temperature deposition manufacturing (DLDM) technology. The outer PU layer provided a mechanically stable tunnel against scar tissue invasion in vivo, while the inner collagen layer promoted Schwann cell adhesion, migration, and proliferation. Microporous structures were found in both the layers. A tight connection between the double layers was achieved by adjusting the distance between the two deposit nozzles and adjusting other processing parameters. Schwann cells from rat sciatic nerves were cultured in the layered PU-collagen conduits for one week; a significant enhancement in their retention and viability was seen compared to those made of pure PU. The poly(urethane— collagen) double layer conduit had better Schwann cell compatibility and so has a great potential use in clinical peripheral nerve repair.

A Novel Osteochondral Scaffold Fabricated via Multi-nozzle Low-temperature Deposition Manufacturing

Liu, L., Xiong, Z., Zhang, R., Jin, L., Yongnian Yan, — Tue, 19 May 2009 02:53:08 PDT

A functional-region/separate-interface/single-cell-type of tissue engineering pathway was evaluated to regenerate osteochondral defects that are deep in the marrow cavity. A gradient osteochondral scaffold fabricated via a rapid prototyping technology, called multi-nozzle low-temperature deposition manufacturing, was composed of three parts with different materials and pore-structures, respectively, for bone, cartilage and a separate interface between them. The separate interface was composed of micro-pores, that were less than 5 µm and with low porosity, to reduce or to avoid the destruction of the micro-environment in vivo by preventing blood and cells and reducing the amount of oxygen and nutrients moving from the marrow cavity to the articulate marrow. The preliminary results after 6 weeks of implantation into 4 mm diameter osteochondral defects in the knee joints of rabbits showed that the defects with the scaffold/cells composition had bone-like or cartilage-like tissue filling the defects with smooth surface, while the defects with nothing (blank) showed only fibrous tissue.

Controlled Adipose-derived Stromal Cells Differentiation into Adipose and Endothelial Cells in a 3D Structure Established by Cell-assembly Technique

Xu, M., Yan, Y., Liu, H., Yao, R., Wang, X. — Tue, 19 May 2009 02:53:08 PDT

One of the major obstacles in engineering thick and complex tissues while vascularizing tissues in vitro is to maintain cell viability during tissue growth and structural organization. Adipose-derived stromal (ADS) cells were used to establish a multicellular system through a cell-assembly technique. Attempts were made to control ADS cells differentiation into different targeted cell types according to their positions within an orderly 3D structure. Oil red O staining confirmed that the ADS cells in the structure differentiated into adipocytes with a spherical shape while immunostaining tests confirmed that the endothelial growth factor induced ADS cells on the walls of channels differentiated into mature endothelial cells and then organized into tubular structures throughout the engineered 3D structure. The endothelin-1 and nitric oxide release rules of the endothelial cells were coincidental with those in vivo. This study provides a new approach to engineer orderly endothelial vessel networks in vitro and has potential applications in adipose-tissue engineering.

Design and Evaluation of a Cell Microencapsulating Device for Cell Assembly Technology

Rui Yao, , Renji Zhang, , Xiaohong Wang, — Tue, 19 May 2009 02:53:08 PDT

A cell encapsulation device based on the principle of high-voltage dispersion technology was designed and constructed. The parameters that influenced the formation of cell microcapsules, such as; voltage, push speed, electrode distance, and syringe size were analyzed and optimized. Unlike the traditional cell microencapsulating devices, both of the electrodes were separated from the CaCl₂ solution in this device, which simplified the procedure of keeping the operation within a sanitary environment. Integrated adipose derived stem cell (ADSC) microcapsules with smooth surface and consistent diameter distribution were prepared. After 1-week in culture as a microcapsule and 3 days assembled in a construct, the ADSCs maintained a high viability and significant proliferation that established a favorable basis for the controlled assembly of cell microcapsules.

Branched Channel Scaffolds Fabricated by SFF for Direct Cell Growth Observations

Shanglong Xu, , Yue Yang, , Xibin Wang, , Chaofeng Wang, — Tue, 19 May 2009 02:53:08 PDT

A β-TCP scaffold with a branched channel system was designed to create a novel micro-device that allowed culture perfusion and direct time observation of the cells attached. The scaffold was made by indirect solid free form fabrication (SFF) technology. The flow channel structure was exposed so that the perfusion of the mesenchymal stem cell (MSC) culture could be viewed directly. The cell-seeded scaffolds were continuously perfused for 7 days in the micro-device; during this time, it was possible to observe the dynamic culture processes with cells adhering to the scaffolds and real time cell growth directly. This concept has great potential for use in bone tissue engineering and for versatile fabrication of enhanced scaffolds.

In Vitro Evaluation of a 3D PLGA--TCP Composite Scaffold in an Experimental Bioreactor

Tue, 19 May 2009 02:53:08 PDT

A 3D poly(lactic acid-co-glycolic acid)/tricalcium phosphate (PLGA—TCP) composite scaffold, generated with the low-temperature deposition modeling rapid prototyping technique, was tested for its viability in a 3D cell cultivation in vitro. The aim was to find optimal cell culture conditions for the selected scaffold material and to monitor cell division, differentiation, and migration of selected cell types in this environment. In addition, the behavior and cell-matrix interactions of selected cell types were monitored as well as the biodegradation rate of the tested scaffold material. Chinese hamster ovary cells as well as a human cell line 293 epithelial cells were cultured on the scaffolds. A variety of different preconditioning protocols were deployed to prepare the scaffolds before seeding with the cells. Cell cultivations were conducted for 1—4 weeks and the coverage of the luminal surfaces was analyzed with light microscopy. Long cultivation periods were required to achieve partial coverage of the luminal surfaces of the scaffolds. Tissue engineering with 3D cell cultures and biomaterials represents a promising approach for organ manufacturing research. It may have potential for eventual on-demand high-throughput production of artificial tissues but the process has many challenges. The culture system in a well controlled bioreactor environment is discussed.

Gradient Hydrogel Construct Based on an Improved Cell Assembling System

Tue, 19 May 2009 02:53:08 PDT

In this study, a two-step crosslinking method derived from commercial rapid prototyping equipment was used to fabricate a gradient hydrogel scaffold in vitro. This system contained two types of nozzles; one was double-nozzle unit, used for relatively simple gradient hydrogel scaffold composed of two nonmiscible hydrogel materials. The other was single nozzle that was used for mixing a gradient hydrogel scaffold composed of two types of hydrogel materials. Different types of scaffolds were formed by modifying the gradient in one of the relevant nozzles. To improve the extrusion controlling effect, accessorial parameters were introduced. A 3D gradient construct containing neuron cells and Schwann cells was fabricated and cultured for 7 days. This construct was helpful in designing a gradient mode to observe the relationship between different cells in vitro. This work has improved tissue-engineering techniques for later manufacturing of very complicated organ analogs.

Three-dimensional Reconstruction of Functional Fascicular Groups Inside a Segment of Common Peroneal Nerve

Tue, 19 May 2009 02:53:08 PDT

The virtual human plan has been the hot point of recent research. The objective of this study is to explore the possibility of three-dimensional (3D) reconstruction of functional fascicular groups inside short segmental peripheral nerve. A 5 cm length of common peroneal nerve was horizontally sliced at 0.25 mm intervals, and each section was stained with acetycholinesterase histochemical staining. The 2D panorama images were acquired by high-resolution digital camera under 100x microscope and mosaic software; different functional fascicular groups were distinguished and marked. The topographic database was then matched using image processing software, through the 3D reconstruction achieved using 3D reconstruction software (Amira 3.1). The reconstructed 3D images could be rotated or zoomed in any direction and the intercross and recombination processes of nerve bundles could be observed. Based on the serial histological sections and computer technology, the 3D microstructure of short segmental peripheral nerve functional fascicular groups was reconstructed. These results provide the possibility of 3D reconstruction of long segmental peripheral nerve functional fascicular groups.

Fabrication and In Vitro Evaluation of Calcium Phosphate Combined with Chitosan Fibers for Scaffold Structures

Tue, 19 May 2009 02:53:08 PDT

A rapid prototyping and rapid tool technique-based method was developed to fabricate chitosan fiber calcium phosphate cement composites (CF/CPC) for bone tissue engineering scaffold applications. The products were characterized and the in vitro performance with canine bone marrow stem cells (BMCs) on CF/CPC scaffold with controlled fiber structures evaluated. The X-ray diffraction analysis showed that about 91% of the inorganic part of the CF/CPC scaffold was hydroxyapatite (HA) and the variation in CF had little effect on the percentage of HA content. The results from in vitro study demonstrated that the interconnected macropores rapidly formed inside the CF/CPC scaffolds and that the patterns were related to the fiber structures used. The differences in the fiber structures altered the morphology of the BMCs without affecting the proliferation of the BMCs.

Fabrication of Repairing Skull Bone Defects Based on the Rapid Prototyping

Wenzheng Wu, , Yang Zhang, , Hu Li, , Wanshan Wang, — Tue, 19 May 2009 02:53:08 PDT

The Rapid Prototyping (RP) manufacture technology, computer tomography (CT) image processing, and mechanical analyses were adopted to repair a skull defect injury. After the patient was inspected by spiral CT the data was exported to Digital Imaging and Communications in Medicine (DICOM) format. The data was processed with Mimics software to eliminate noise and gray-level registration. The processing filtered out the parenchyma data and preserved the bone data. The STL files were analyzed and processed by the Magics and put into the RP equipment. The RP equipment is one type of Stereo Lithography Apparatus (SLA) with laser light spot diameter that is <0.2 mm. The 3D models were analyzed to comply with the patients' requirements. The stereo lithography model emulated the mechanical properties and shape with the patient's bone. The titanium-alloy plate matched the anatomy well. The 3D reconstructed freeform model was accurate to within 0.2 mm.

In Vitro Cytotoxicity of Bacterial Cellulose Scaffolds Used for Tissue-engineered Bone

Tue, 19 May 2009 02:53:08 PDT

The in vitro degradation and cytotoxicity of bacterial cellulose (BC) and its degradation products were studied for potential applications in bone tissue engineering. Emission scanning electron microscope was used to observe the morphology of original materials and their degradation products. The degradation was evaluated by measuring the concentration of reducing sugar by using ultraviolet spectrophotometer. Bone forming osteoblast (OB) cells and infinite culture cell line L929 fibroblasts were used to measure the cytotoxicity of materials using the MTT assay. Both types of cells proliferated normally with the BC and its degradation products with a cytotoxicity graded of 0—1. Nevertheless, the bone-forming target OB cells were more susceptible to cytotoxicity than the infinite culture fibroblast cells L929 fibroblasts. The results indicate that the BC is not very cytotoxic and that tissue functional cells are more suitable for evaluating the cytotoxicity of biomedical materials.

Intervertebral Spinal Fusion Using a RP-based PLGA/TCP/ bBMP Biomimetic Grafting Material

Tue, 19 May 2009 02:53:08 PDT

Three-dimensional highly porous poly(DL-lactic-co-glycolic acid)/ tricalcium phosphate (PLGA/TCP) scaffolds were synthesized via a rapid prototyping (RP) technique. Bovine bone morphogenetic protein (bBMP) was loaded into the biopolymer scaffolds (PLGA/TCP/bBMP). Both the PLGA/TCP scaffolds and the PLGA/TCP/bBMP composites were evaluated by scanning electron microscopy. Lumbar intervertebral body fusion at L2~3 and L4~5 levels were performed on 15 goats using one of the following graft materials: RP synthesized PLGA/TCP scaffolds (group A), PLGA/TCP/bBMP composites (group B), and autogenous iliac bone graft (group C). All animals were sacrificed 24 weeks after surgery and the spine fusions evaluated by manual palpation tests, histological analyses, and radiography. In group A, the histological analyses showed that the PLGA/TCP scaffolds were biocompatible and biodegradable; however, no new bone was found. In group B, highly cellular bone marrow between the new trabecular bone was present in the fusion mass. In group C, there was a lesser amount of new bone. Twenty-four weeks after surgery, the fusion rate of lumbar intervertebral body fusion in group A, B, and C was 10% (1/10), 80% (8/10), and 50% (5/10), respectively. The fusion rate was significantly higher in group B compared with groups of A and C (p<0.01). Based on these results, extracted bBMP can be loaded in vitro into RP-based highly porous structural PLGA/TCP scaffolds to fabricate new graft composites that appear to be more effective for intervertebral spinal fusions. This biomimetic artificial grafting material holds promise as a tool for spine surgery.

Design and Preparation of an Electrospun Biomaterial Surgical Patch

Hai Lu, , Chen, W.-J., Yan Xing, , Ying, D.-J., Bo Jiang, — Tue, 19 May 2009 02:53:08 PDT

A biomaterial patch of electrospun collagen type fibers was designed and produced by electrospinning seven different concentrations (8%—20% w/v) of collagen solutions. The tensile strength, yield strength, and elastic modulus of the electrospun collagen fibrous patches were found to be suitable for clinical transplantation. No significant differences versus fresh porcine pericardium as controls were observed. The SEM images of the groups showed that the patches were smooth with uniform interwoven and porous morphology. The fibrous patches were biocompatible and did not elicit local or systemic toxic effects when implanted in vivo. These electrospun collagen fibrous patches have significant potential as surgical biomaterial patches.

Preparation of Bioactive Hydroxyapatite on Pure Titanium

Wang Tianshi, , Zhang Renji, , Yan Yongnian, — Tue, 19 May 2009 02:53:08 PDT

In this study, a hydroxyapatite (HA) was coated on a pure titanium surface by means of a complex oxidation and hydrothermal treatment. First an anodic oxidation was done on the titanium plates, followed by micro-arc oxidation. The HA-coated specimens and pure titanium specimens were immersed in SLB for 1, 5, and 10 days, respectively, to study their electrochemical behavior. The corrosion currents of HA-coated specimens were less than pure titanium specimens. This indicated that HA coating prevented surface metal ions of the implant from dissolving, thereby, reducing the tissue toxicity. The cytotoxic effect on fibroblasts L929 cells was measured by cell counting after being seeded for 2, 4, 8, 12, and 24 h. The number of surface cell attachments on the HA-coated specimens was much greater than on pure titanium specimens. The morphology of the cells on the HA coating had normal shapes and spread well with some cells climbing onto surface pores while cells on the pure titanium were oval shaped. The results confirm that the cell compatibility on HA-coated ion titanium surfaces is much better than pure titanium.

The Design and Modeling of Multi-axis Knee Artificial Leg

Hualong Xie, , Lixin Guo, , Yongxian Liu, , Fei Li, — Tue, 19 May 2009 02:53:08 PDT

To provide an ideal test-base for the development of an intelligent bionic leg, a new pattern humanoid robot — biped robot with heterogeneous legs (BRHL) was designed. To simulate a normal human gait, a multi-axis knee mechanism was included into the artificial leg design that was different from the artificial leg of a common biped robot. The conception and research purposed for the BRHL was developed. Based on human bioscience, the bionic design of multi-axis knee artificial leg was analyzed and a virtual prototype was made. The kinematics model and dynamics model were deduced in detail. Based on human normal gait data, a simulation of dynamics model was carried. An optimized mechanical design of multi-axis knee artificial leg is discussed and a simulation was done. The optimal mechanism parameters for the multi-axis knee artificial leg and a BRHL prototype were given. This research indicated that a multi-axis knee artificial leg can simulate a human leg.