Shan Ding

In vitro evaluation of random and aligned polycaprolactone/gelatin fibers via electrospinning for bone tissue engineering.

Scaffold, as an essential element of tissue engineering, should provide proper chemical and structural cues to direct tissue regeneration. In this study, aligned and random polycaprolactone (PCL)/gelatin fibrous scaffolds with different mass ratio were electrospun. Chemical, structural, and mechanical properties of PCL/gelatin fibrous scaffolds were characterized by FTIR and tensile measurements. The average diameters of different groups were between 334.96 ± 41.43 nm and 363.78 ± 50.49 nm. Blending PCL with gelatin increased the mechanical properties of the scaffolds. The cell culture results demonstrated that the mass ratio of PCL and gelatin showed no obvious effects on cell behavior, whereas the cell growth behavior was affected by the fibers orientation. Higher elongation ratio, enhanced cell proliferation and elevated alkaline phosphatase activity were observed for cells cultured on aligned fibers. The findings in our research provide insightful information for the design and fabrication of scaffolds for bone tissue engineering.

Rapid biomimetic mineralization of collagen fibrils and combining with human umbilical cord mesenchymal stem cells for bone defects healing.

Collagen biomineralization is regulated by complicated interactions between the collagen matrix and non-collagenous extracellular proteins. Here, the use of sodium tripolyphosphate to simulate the templating functional motif of the C-terminal fragment of non-collagenous proteins is reported, and a low molecular weight polyacrylic acid served as a sequestration agent to stabilize amorphous calcium phosphate into nanoprecursors. Self-assembled collagen fibrils served as a fixed template for achieving rapid biomimetic mineralization in vitro. Results demonstrated that, during the mineralization process, intrafibrillar and extrafibrillar hydroxyapatite mineral with collagen fibrils formed and did so via bottom-up nanoparticle assembly based on the non-classical crystallization approach in the presence of these dual biomimetic functional analogues. In vitro human umbilical cord mesenchymal stem cell (hUCMSC) culture found that the mineralized scaffolds have a better cytocompatibility in terms of cell viability, adhesion, proliferation, and differentiation into osteoblasts. A rabbit femoral condyle defect model was established to confirm the ability of the n-HA/collagen scaffolds to facilitate bone regeneration and repair. The images of gross anatomy, MRI, CT and histomorphology taken 6 and 12weeks after surgery showed that the biomimetic mineralized collagen scaffolds with hUCMSCs can promote the healing speed of bone defects in vivo, and both of the scaffolds groups performing better than the bone defect control group. As new bone tissue formed, the scaffolds degraded and were gradually absorbed. All these results demonstrated that both of the scaffolds and cells have better histocompatibility.

Liposomes coated with thiolated chitosan as drug carriers of curcumin

Liposome is one of a promising delivery system to improve water solubility, stability, and bioavailability of curcumin. But its instability is not favorable for long-circulating treatment, controlled release or conservation. To overcome the disadvantages, thiol derivatised chitosan (CSSH) were synthesized and utilized to coat liposomes. The CSSH coated curcumin liposomes (Cur-Lip-CSSH) had an encapsulation efficiency (EE) of 93.95%, a drug loading (DL) of 7.95%, an average particle size of 406.0nm, and a positive zeta-potential of 36.6mV, which were all higher than that of Cur-Lip. Cur-Lip-CSSH showed slower in vitro release than Cur-Lip at pH5.5 and pH7.4, and the higher retention of curcumin would be remained for the following uptake of cells. The stability of the both liposomes at 4°C was almost the same, but Cur-Lip-CSSH displayed a higher stability at room temperature and higher temperature by DSC characterization. Curcumin can inhibit the growth of cancer cells under certain conditions. MCF-7 cell line was used to study its inhibition and proliferation after treating with curcumin and Cur-Lip-CSSH. Treatment of MCF-7 with curcumin and Cur-Lip-CSSH showed dose and time dependent cytotoxicity, with growth suppression at 200μM, 72h, obviously. These results indicate that the proper coating of liposomes is able to improve the stability of liposomes and the Lip-CSSH can function as potential drug delivery system.

Mechanical properties and osteogenic activity of poly( l -lactide) fibrous membrane synergistically enhanced by chitosan nanofibers and polydopamine layer

To synergistically improve the mechanical properties and osteogenic activity of electrospinning poly(l-lactide) (PLLA) membrane, chitosan (CS) nanofibers were firstly introduced to prepare sub-micro and nanofibers interpenetrated PLLA/CS membrane, which was further surface modified with a polydopamine (PDA) layer to obtain PLLA/CS-PDA. Surface morphology, porosity, surface area and hydrophilicity of the obtained fibrous membranes were studied in detail. As compared to pure PLLA, the significant increase in the mechanical properties of the PLLA/CS, and especially of the PLLA/CS-PDA, was confirmed by tensile testing both in dry and wet states. Cells culture results indicated that both the PLLA/CS and PLLA/CS-PDA membranes, especially the latter, were more beneficial to adhesion, spreading and proliferation, as well as up-regulating alkaline phosphate activity and calcium deposition of MC3T3-E1 cells than PLLA membrane. Results suggested there was a synergistic effect of the CS nanofibers and PDA layer on the mechanical properties and osteogenic activity of PLLA membrane.

Collagen films with stabilized liquid crystalline phases and concerns on osteoblast behaviors.

To duplicate collagens in vivo liquid crystalline (LC) phase and investigate the relationship between the morphology of LC collagen and osteoblast behavior, a self-assembly method was introduced for preparing collagen films with a stabilized LC phase. The LC texture and topological structure of the films before and after stabilization were observed with polarizing optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The relationship between the collagen films and osteoblast behavior was studied with the 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide method, proliferation index detection, alkaline phosphatase measurements, osteocalcin assay, inverted microscopy, SEM observation, AFM observation, and cytoskeleton fluorescence staining. The results showed that the LC collagen film had continuously twisting orientations in the cholesteric phase with a typical series of arced patterns. The collagen fibers assembled in a well-organized orientation in the LC film. Compared to the non-LC film, the LC collagen film can promote cell proliferation, and increase ALP and osteocalcin expression, revealing a contact guide effect on osteoblasts.

Single-step mineralization of woodpile chitosan scaffolds with improved cell compatibility.

A facile and efficient single-step mineralization approach was exploited for achieving nanoscopic hydroxyapatite (HAP) crystal layer in chitosan porous matrix, wherein a mixed water-ethanol solvent was used to control the growth of minerals. The crystallographic structure, morphology, and mechanical properties of the scaffold were analyzed with XRD, FTIR, environmental scanning electric microscopy (ESEM), TEM, and compression tests. The behaviors and responses of MC3T3-E1 pre-osteoblast cells on the scaffolds were studied as well. The results showed that the scaffolds kept woodpile structure with predefined and controlled hierarchical structure after mineralization. The inorganic phase in the mineralized chitosan scaffolds was determined as pure rod-like HAP, which settled densely on the matrix. The compression strength and compressive modulus of the scaffolds increased dramatically to 0.54 ± 0.005 MPa and 5.47 ± 0.65 MPa, respectively. During a culture period of 2 and 3 weeks, cell proliferation and in-growth were observed by phase contrast light microscopy and SEM. The alkaline phosphatase (ALP) activity increased after 1 week. Cell viability and cell proliferation index (PI) obtained higher values than that of the chitosan scaffolds. The novel single-step mineralization approach and the porous hybrid scaffolds would be a promising method for designing hybrid bone graft.

A novel biomimetic scaffold with hUCMSCs for lumbar fusion

Discectomy and lumbar fusion are common clinical approaches to treating intervertebral disc (IVD) degeneration with the aid of autologous bone and/or biomaterials. Biomaterials are considered suitable if they are biodegradable and can guide tissue regeneration. These features are necessary for total IVD removal, when it degenerates, as lumbar fusion treatment, avoiding secondary damage caused by the use of autogenous bone. In this work, a novel biomimetic porous chitosan/poly(l-lactic acid) scaffold with human umbilical cord mesenchymal stem cells (hUCMSCs) was applied in lumbar fusion. Hierarchically porous chitosan scaffolds were prepared using molds, porogens and freeze drying, and then poly(l-lactic acid) networks were distributed throughout the interior scaffold to enhance mechanical strength. We conducted cell culture in vitro and animal experiments in vivo. The scaffolds were incubated in hUCMSCs medium and co-cultured for 8 days, and then implanted into half-destroyed IVDs in New Zealand rabbits. The results show that scaffolds with hUCMSCs had greater ability to guide disc regeneration than the blank control and autologous bone, as determined using X-rays, computed tomography, and histologic analyses. Findings confirmed the role of hUCMSCs stimulation in bone-tissue healing and IVD regeneration. This hMUMSCs-based approach, together with the strategy proposed for incorporating osteoblastic cells into scaffolds that promote endogenous or synthetic repair mechanisms, may then be used to develop strategies for the stem-cell-based healing of other acute injuries and chronic diseases.

Dual drug loaded coaxial electrospun PLGA/PVP fiber for guided tissue regeneration under control of infection

Electrospinning promisingly fabricate mats for Guided Tissue Regeneration (GTR). Due to a chronic inflammatory pathology in periodontal, it is highly desirable to develop a novel GTR mats to realize tissue regeneration under control of infection. In the study, coaxial electrospinning was firstly conducted to fabricate dual drug loaded fiber mats with core/shell structure. Naringin-loaded polyvinylpyrrolidone was designed as core fiber to enrich tissue regeneration and metronidazole-loaded poly(lactic-co-glycolic acid) as shell fiber to inhibit bacterial. TEM revealed that the fibers with distinct core/shell structure were in an outer diameter of 1.5-1.7 μm with an inner diameter of <1.0 μm. The loading of dual drug decreased the tensile strength and elongation of the coaxial fiber mats. On in vitro assessment, metronidazole had a short-term release while naringin had a long-term release behavior in all the coaxial mats. The colonization of anaerobic bacteria on the mats effectively were inhibited over 21 days. Furthermore, the dual drug loaded coaxial fiber mats were observed to positively supported the adhesion and proliferation of MC3T3-E1 and was conductive to high alkaline phosphatase express. Thus, a simple and effective coaxial electrospinning approach was demonstrated for the fabrication of anti-infective GTR mats with promoting tissue regeneration.