Papers by Author: Lei Cui

Abstract: To investigate the influence of initial copolymer compositions of poly (lactic-co-glycolic acid) (PLGA) on mechanical properties, degradation behavior and biological properties of the scaffolds, porous PLGA scaffolds with different initial copolymer compositions (lactide/glycolide (PLA/PGA) molar ratio: 50:50, 70:30 and 80:20) were prepared by solvent casting/particulate leaching method. Mechanical properties were measured by testing the tensile strength and degradation rate was detected by soaking the scaffolds in phosphate buffered solution at 37 °C for various time points. Human dermal fibroblasts were seeded on PLGA scaffolds with different copolymer compositions. The morphology, adhesion efficiency, proliferation rate, and total collagen contents of cells on the scaffolds were analyzed. The results showed that the ratio of PLA/PGA is one important factor which influences the degradation of scaffolds. The mechanical strength of PLGA scaffolds with the ratio of 70:30 and 80:20, was higher than that of PLGA scaffolds with the ratio of 50:50.. Compared to 70:30 and 80:20 PLGA scaffolds, 50:50 PLGA had a quicker degradation. The three PLGA scaffolds had no obvious difference for cell response and all of them had excellent cytocompatibility, indicated by their high efficiency for human dermal fibroblast adhesion, fast proliferation rate and stretched cell morphology. A large amount of extracellular matrix was secreted and after 7 days of culture, and cell nearly covered the entire surface of the scaffolds. Overall, our results indicate that the copolymer compositions of PLGA have important effect on degradation and mechanical strength, but have no obvious effect on the biological properties of the scaffolds.

Abstract: Poly(butylenes succinate) (PBSU) had good biocompatibility and biodegradability, but it is left unexplored for the possible application of PBSU in tissue engineering. The aim of this study was to compare PBSU and poly (lactide-co-glycolide) (PLGA) scaffolds prepared by electrospinning technique as vascular tissue engineering materials. Both scaffolds were characterized by fiber morphology, pore structure and mechanical properties. Smooth muscle cells (SMCs) and endothelial cells (ECs) were seeded on the electrospun PBSU and PLGA scaffolds and cultured for different time periods. Cell adhesion and proliferation on the scaffolds were measured by MTT assay, while SEM was used for observing cell morphology on the scaffolds. The results showed that fiber diameter of the electrospun scaffolds ranged from 300nm to 800nm and their porosities were higher than 90%. The electrospun PBSU scaffolds showed a high tensile strength of 2.06±0.11MPa, whereas the ultimate tensile strength of the electrospun PLGA scaffolds reached 14.31±5.24MPa. Cell adhesion efficacy had no significant difference between PBSU and PLGA scaffolds, but cell proliferation rate on PLGA scaffolds was significantly higher than that on PBSU scaffolds after 7 days of culture. Cell morphology was similar on both scaffolds with the polygonal shape for ECs and spindle-like shape for SMCs. From these results, the present in vitro study revealed that as compared to PLGA scaffolds, the electrospun PBSU scaffolds showed lower tensile strength and slower proliferation rate, but as regards the biocompatibility and pore structure, the electrospun PBSU scaffolds had a potential application in vascular tissue engineering.

Abstract: Chitin/Chitosan membrane has been used as wound dressing materials to facilitate clinical wound healing for many years. However, there are fewer articles studying the cell-biomaterial interaction in vitro or in vivo. In this study, the biological characteristics of human keratinocytes cultured on chitosan membrane that was mixed with gelatin in different ratio were investigated in vitro. Chitosan-gelatin membrane (CGM) in different ratio were prepared with N, N-(3 dimethylaminopropyl)-N'-ethyl carbodiimide (EDC). CGMs were divided into four groups: pure chitosan membrane, 7:3 (chitosan: gelatin), 5:5 and 3:7 groups. Human keratinocytes were isolated from foreskin by Dispase/Trypsin-EDTA digestion. Keratinocytes of passage3 were then seeded on the surface of CGM. Cloning forming efficiency (CFE) and migration distance of cultured keratinocytes on CGM were measured. The CFE of keratinocytes cultured on the surface of pure chitosan membrane was 9.8±2.08%; cultured on 7:3 CGM was 14.33±1.53%, 5:5 CGM was 19.17±1.26%, 3:7 CGM was 18.33±2.08%. The migration distance of cultured keratinocytes on pure chitosan membrane was 61.47±2.70µm, 7:3 CGM was 66.22±9.39µm, 5:5 CGM was 120.31±15.82µm, 3:7 CGM was 225.38±10.48µm. This sutdy demonstrated that increasing contents of gelatin in CGM could promote keratinocyte proliferation and migration. The results also suggested the membrane prepared from chitosan and gelatin can be utilized as a good keratinocyte delivery system.

Abstract: Objective The purpose of this study is to explore the growth, differentiation and osteogeneration of bone marrow stromal cells (BMSCs) on partially demineralized bone matrix (pDBM) and to generate bone tissue by tissue engineering approach in vivo. Methods Demineralized bone was processed from femur head of Shanghai white swine. Calcium content, porosity and pore size was measured respectively. In vitro osteogenic differentiated human BMSCs of passage 3 were seeded in pDBM. Adhesive rate of cells to pDBM was calculated 24hours after seeding. Distribution, growth and proliferation of BMSCs on pDBM were observed with fluorescent DiI labeling. Matrix disposition was analyzed with SEM observation. Cell-material complex was implanted subcutaneously in nude mice. The implants were harvested at 8, 12 weeks post surgery and samples were observed by H&E staining. Results BMSCs adhered well on the material and the distribution of cells was uniform. The adhesive rate is 99.1%±1%. New bone formation was observed in implant of 8, 12 weeks respectively. The newly formed bone was generated on the surface of the residual material and a layer of cells with typical characteristic of osteoblast was observed to adhere on the surface of the new bone. Conclusion With good biocompatibility to hBMSCs, pDBM could serve as ideal scaffold for bone tissue engineering both in vitro and in vivo.

Abstract: Objective: To compare biocompatibility, degradation, and mechanical properties of polyglycolic acid (PGA) unwoven and woven fibers as scaffolding materials for tendon engineering in vitro. Methods: Three kinds of PGA fibers were included in this study. PGA raw material (Purac Co, Holland) was spun into single PGA filaments that were further twisted into woven fibers (PGA- 1). PGA filaments (Nantong Holycon, China) were twisted into woven fibers (PGA-2) as well. PGA-1 and PGA-2 served as experimental groups 1 and 2, while unwoven PGA fibers (Albany Co, USA) served as control group. Three types of PGA fibers were made into cord-like scaffolds that mimic tendon shape and compared with each other for biocompatibility, degradation and biomechanical properties. Avian tenocytes were isolated from digital flexor tendon and expanded in vitro. Cells of the second passage were seeded onto the PGA scaffolds. In the first 2 weeks, the cell- PGA constructs were in vitro cultured without tension and observed for cell adhesion and matrix production. The constructs were then cultured under dynamic loading in a bioreactor for another 2 weeks followed by gross and histological examinations. Results: PGA unwoven fibers have the median diameter of 10µm, while PGA-1 and PGA-2 fibers have the median diameters of 200µm and 60µm, respectively. Microscopy showed that tenocytes adhered well to all three types of PGA fibers in the first 10 days and produced abundant matrices. However, cells showed poor viability on PGA-2 fibers after 10 days, yet good viability on the other two PGA fibers over 2 weeks of observation period. H&E staining showed that there were viable cells and abundant matrices in the control and PGA-1 groups, but not in PGA-2 group after 4 weeks of in vitro culture. Additionally, PGA unwoven fibers degraded faster than woven fibers (PGA-1 and -2). Interestingly, the PGAtenocyte constructs formed tendon-like tissue after 4 weeks of in vitro culture grossly and histologically. Furthermore, mechanical test demonstrated that both PGA woven fibers had much higher tensile strength than unwoven fibers. Conclusion: Different PGA fibers have different biocompatibility with seeded tenocytes. PGA woven fibers could bear more intense mechanical loading and degrade slower than unwoven fibers, which is essential for in vitro generation of tendon tissue. Thus PGA woven fibers might serve as a proper form of scaffolding material for in vitro tendon engineering in a bioreactor.

Abstract: Bone Marrow Stromal Cells (BMSCs) have chondrogenesis potential if chondrogenic environments or factors are provided. This study tests the hypothesis that chondrocytes can promote BMSC chondrogenesis at non-chondrogensis site. Porcine BMSCs and auricular chondrocytes were mixed at different ratios and 2.5×107 mixed cells were resuspended in 0.5 ml 30％ Pluronic, and then the mixture was injected into nude mice subcutaneously as experimental groups. Chondrocytes or BMSCs at the same cell number were mixed with 0.5 ml Pluronic and injected respectively as controls. 2.5×107 chondrocytes were mixed and injected as low concentration chondrocyte control. 8 weeks later, all specimens in experimental groups and chondrocyte group formed mature cartilage with abundant collagen II expression. Mature lacuna structures and metachromatic matrices were also observed in these specimens with the same level of GAG contents. Average wet weight of specimens in experimental groups was over 70% of that in chondrocyte group. In contrast, specimens in BMSC group showed mainly fibrous tissue. Only a small amount of cartilage was formed in specimens of low concentration chondrocyte group and the average wet weight was below 30% of that in chondrocyte group. These results demonstrate that chondrocytes can provide chondrogenic microenvironment and thus promote in vivo chondrogenesis of BMSCs at non-chondrogenesis sites. It also indicates that Pluronic is an ideal injectable biomaterial for cartilage tissue engineering.