Electroactive porous tubular scaffolds with degradability and non-cytotoxicity for neural tissue regeneration

Electroactive degradable porous tubular scaffolds were fabricated from the blends of polycaprolactone and a hyperbranched degradable conducting copolymer at different feed ratios by a solution-casting/salt-leaching method. Scaning electron microscopy (SEM) and microcomputed tomography tests indicated that these scaffolds had homogeneously distributed interconnected pores on the cross-section and surface. The electrical conductivity of films with the same composition as the scaffolds was between 3.4 × 10⁻⁶ and 3.1 × 10⁻⁷ S cm⁻¹, depending on the ratio of hyperbranched degradable conducting copolymer to polycaprolactone. A hydrophilic surface with a contact angle of water about 30° was achieved by doping the films with (±)-10-camphorsulfonic acid. The mechanical properties of the films were investigated by tensile tests, and the morphology of the films was studied by SEM. The scaffolds were subjected to the WST test (a cell proliferation and cytotoxicity assay using water-soluble tetrazolium salts) with HaCaT keratinocyte cells, and the results show that these scaffolds are non-cytotoxic. These degradable electroactive tubular scaffolds are good candidates for neural tissue engineering application.     

The use of reactive polymer coatings to facilitate gene delivery from poly (-caprolactone) scaffolds

To functionalize biomaterials for bioconjugation, a chemical vapor deposition (CVD) polymerization technique was utilized to modify material surfaces. Poly [(4-amino-p-xylylene)-co-(p-xylylene)] (PPX–NH₂) was deposited on inert polycaprolactone (PCL) surfaces to provide a reactive amine layer on the substrate surfaces. The biocompatibility of PPX–NH₂ was evaluated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase (LDH) assays. The results demonstrated that cells continuously proliferated on CVD treated PCL surfaces with high survival rates. Biotin was conjugated on modified PCL surfaces to immobilize avidin for binding of biotinylated adenovirus. Scanning electron microscopy (SEM) examination illustrated that adenoviruses were evenly bound on both 2-D films and 3-D scaffolds, suggesting CVD was capable of modifying various substrates with different geometries. Using a wax masking technique, the biotin conjugation was controlled to immobilize avidin on specific sites. Due to the virus binding specificity on CVD-modified surfaces, cell transduction was restricted to the pattern of immobilized virus on biomaterials, by which transduced and non-transduced cells were controlled in different regions with a distinct interface. Because CVD was functional in different hierarchies, this surface modification should be able to custom-tailor bioconjugation for different applications.     

Characterization of a novel composite scaffold consisting of acellular bladder submucosa matrix,polycaprolactone and Pluronic F127 as a substance for bladder reconstruction

The bladder is an organ susceptible to a variety of congenital anomalies, injuries and disorders. To address the clinical limitations of existing scaffolds, we fabricated a novel scaffold that can be applied to morphological and functional bladder reconstruction. As a first step to prove the benefit of the scaffold, intensive in vitro and in vivo analyses were conducted. The novel composite scaffold was fabricated using polycaprolactone/Pluronic F127 (PCL/F127) and variable proportions (1, 3, 5 and 10 wt.%) of porcine acellular bladder submucosa matrix (BSM). Physicochemical properties and biocompatibilities of the scaffolds were characterized. For cell-mediated analysis, upper-urinary-tract-derived urine stem cells were used. Observations of tensile strength, modulus, porosity, cell adhesion, viability and proliferation characteristics of scaffolds indicated that the optimum proportion of BSM in the composite scaffolds was 3 or 5 wt.%. Based on comparison of 3 and 5 wt.% BSM/PCL/F127 scaffolds with respect to degradability, hydrophilicity, surface properties and functional group presence, the 3 wt.% BSM was chosen for in vivo studies. 8 weeks after kidney-subcapsular implantation of the 3 wt.% BSM/PCL/F127 scaffold, cells remained attached to the surface and there was no evidence of teratomas. A BSM content of 3 wt.% was the optimum proportion for fabrication of the neo scaffold. We predict that the 3 wt.% BSM/PCL/F127 composite scaffold could act as an ideal matrix after cystectomy based on its favorable physicochemical properties and biocompatibilities.     

Biological performance of a polycaprolactone-based scaffold plus recombinant human morphogenetic protein-2 (rhBMP-2) in an ovine thoracic interbody fusion model

Purpose

We develop a sheep thoracic spine interbody fusion model to study the suitability of polycaprolactone-based scaffold and recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone graft substitute within the thoracic spine. The surgical approach is a mini-open thoracotomy with relevance to minimally invasive deformity correction surgery for adolescent idiopathic scoliosis. To date there are no studies examining the use of this biodegradable implant in combination with biologics in a sheep thoracic spine model.

Methods

In the present study, six sheep underwent a 3-level (T6/7, T8/9 and T10/11) discectomy with randomly allocated implantation of a different graft substitute at each of the three levels: (a) calcium phosphate (CaP) coated polycaprolactone-based scaffold plus 0.54 μg rhBMP-2 (b) CaP-coated PCL-based scaffold alone or (c) autograft (mulched rib head). Fusion was assessed at 6 months post-surgery.

Results

Computed Tomographic scanning demonstrated higher fusion grades in the rhBMP-2 plus PCL-based scaffold group in comparison with either PCL-based scaffold alone or autograft. These results were supported by histological evaluations of the respective groups. Biomechanical testing revealed significantly higher stiffness for the rhBMP-2 plus PCL-based scaffold group in all loading directions in comparison with the other two groups.

Conclusion

The results of this study demonstrate that rhBMP-2 plus PCL-based scaffold is a viable bone graft substitute, providing an optimal environment for thoracic interbody spinal fusion in a large animal model.     

TGF-β3-induced chondrogenesis in co-cultures of chondrocytes and mesenchymal stem cells on biodegradable scaffolds

In this work, it was hypothesized that co-cultures of articular chondrocytes (ACs) and mesenchymal stem cells (MSCs) would exhibit enhanced sensitivity to chondrogenic stimuli, such as TGF-β3, and would require a reduced concentration of TGF-β3 to achieve an equivalent level of chondrogenesis compared to monocultures of each cell type. Furthermore, it was hypothesized that compared to monocultures, the chondrogenic phenotype of AC/MSC co-cultures would be more stable upon the removal of TGF-β3 from the culture medium. These hypotheses were investigated by culturing ACs and MSCs alone and in a 1:3 ratio on electrospun poly(?-caprolactone) scaffolds. All cell populations were cultured for two weeks with 0, 1, 3, or 10 ng/ml of TGF-β3. After two weeks growth factor supplementation was removed, and the constructs were cultured for two additional weeks. Cell proliferation, extracellular matrix production, and chondrogenic gene expression were evaluated after two and four weeks. The results demonstrated that co-cultures of ACs and MSCs require a reduced concentration and duration of TGF-β3 exposure to achieve an equivalent level of chondrogenesis compared to AC or MSC monocultures. Thus, the present work implicates that the promise of co-cultures for cartilage engineering is enhanced by their robust phenotype and heightened sensitivity to TGF-β3.     

微孔聚已内酯膜对异体肌腱移植后粘连的预防作用

目的研究微孔聚己内酯(PCL)薄膜对同种异体肌腱移植后粘连的预防作用,并探讨其对肌腱愈合的影响。方法选用在-84℃冰箱冻存10d的兔同种异体肌腱移植于30只受体兔右下肢肌腱缺损处,随机分为2组,A组在腱移植处包裹微孔PCL薄膜作为实验组,B组在腱移植处不包裹薄膜作为对照组。术后不同时间,切取腱移植部位,进行大体观察,常规制成光、电镜标本,镜下观察;对移植腱段、吻合口进行羟脯氨酸(HyP)含量及腱周粘连定量测定。结果镜下微孔PCL包膜组腱移植段内部的成纤维细胞数和胶原纤维量与不包膜组无明显差别,但不包膜组腱周组织成纤维细胞数和胶原纤维量明显较微孔PCL包膜组多;HyP含量不包膜组与微孔PCL组差异无统计学意义(P>0.05),移植腱段和吻合口的羟脯氨酸含量,微孔PCL组分别为(27.3±3.5)mg/g体重,(19.2±3.8)mg/g体重;未包膜组为(28.4±3.6)mg/g体重,(20.1±3.2)mg/g体重;不包膜组比微孔PCL组粘连程度重(P<0.05)。结论微孔PCL膜有预防肌腱粘连的作用,对肌腱愈合无影响,临床可作为一种预防肌腱粘连措施。     

Biodegradable nanoparticles as a delivery system for cyclosporine: preparation and characterization

Cyclosporine (CyA) was incorporated into polycaprolactone nanoparticles (PCL-NP) in order to increase its oral bioavailability and to control drug distribution, thereby potentially reducing its toxicity. Prior to in vivo studies, the carrier was optimized and characterized by using different techniques. Light scattering (LS) and transmission and scanning electron microscopy (TEM and SEM) indicated the NP were spherical in shape with a mean size of 100nm. The influence of the solvent evaporation conditions and the polymer and drug amounts on CyA incorporation was established in order to optimize drug loading. When acetone and excess water were removed at constant temperature, no aggregation phenomena were observed. A value of 180mg PCL was the minimum polymer amount necessary to encapsulate 95%of the drug initially added to the preparation. Under these conditions, HPLC analysis revealed that 130mug CyA per mg PCL were incorporated for a total CyA concentration of 2.5mg/ml, being part of the drug adsorbed onto the particle surface. No structural changes or instability of the components during NP preparation were detected by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). However, GPC studies showed a competition between poloxamer and CyA for adsorption onto the carrier. In addition, DSC results suggested that at least part of the drug associated to NP remained in its crystal form. Therefore, CyA-loaded NP were easily manufactured and characterized and allow for the administration of therapeutic drug doses to experimental animals.     

Low density biodegradable shape memory polyurethane foams for embolic biomedical applications

Low density shape memory polymer foams hold significant interest in the biomaterials community for their potential use in minimally invasive embolic biomedical applications. The unique shape memory behavior of these foams allows them to be compressed to a miniaturized form, which can be delivered to an anatomical site via a transcatheter process and thereafter actuated to embolize the desired area. Previous work in this field has described the use of a highly covalently crosslinked polymer structure for maintaining excellent mechanical and shape memory properties at the application-specific ultralow densities. This work is aimed at further expanding the utility of these biomaterials, as implantable low density shape memory polymer foams, by introducing controlled biodegradability. A highly covalently crosslinked network structure was maintained by use of low molecular weight, symmetrical and polyfunctional hydroxyl monomers such as polycaprolactone triol (PCL-t, Mn = 900 g), N,N,N0,N0-tetrakis(hydroxypropyl)ethylenediamine and tris(2-hydroxyethyl)amine. Control over the degradation rate of the materials was achieved by changing the concentration of the degradable PCL-t monomer and by varying the material hydrophobicity. These porous SMP materials exhibit a uniform cell morphology and excellent shape recovery, along with controllable actuation temperature and degradation rate. We believe that they form a new class of low density biodegradable SMP scaffolds that can potentially be used as “smart” non-permanent implants in multiple minimally invasive biomedical applications.     

Recent advances in developing polymeric micelles for treating cancer: Breakthroughs and bottlenecks in their clinical translation

Polymeric micelles (PMs) have been explored pre-clinically for the delivery of chemotherapeutics to treat cancer. Their unique features, such as easy surface functionalization, stimuli-responsiveness, good stability, ability to modify drug release, enhanced permeation and retention effect, and potential to encapsulate more than one type of therapeutic molecules at a time, make them unique carriers for the targeted delivery or for enhancing the bioavailability of chemotherapeutics. PMs can also be used as theranostic nanocarriers for the mapping of drug therapy along with tumor imaging in patients with cancer. This review focuses on the limitations of existing treatment strategies and on innovative approaches employed for the functionalization of PMs for targeting cancer cells. In addition, the bottlenecks associated with the translation of PMs from the laboratory to clinics are also discussed.     

筋膜包裹的骨髓间充质干细胞/聚己内酯复合体血管化组织工程骨修复比格犬骨缺损

背景：骨组织工程技术的材料/细胞复合物已能在肌肉、皮下等异位组织内成骨,或是在小型哺乳动物的骨缺损处修复成骨,但这与临床的实际仍有较大差距,骨组织工程技术能否修复大型哺乳动物大范围的骨缺损,以及如何促进组织工程骨的体内再血管化进程还不明确。 目的：观察应用比格犬带血管蒂深筋膜瓣及组织工程骨在体内的成骨情况。 方法：分离培养比格犬骨髓间充质干细胞,将骨髓间充质干细胞以自然沉淀法进行组织构建,接种于聚己内酯材料上,与支架材料复合。在比格犬左足胫骨中段制作骨-骨膜缺损模型,植入以筋膜包裹的骨髓间充质干细胞/聚己内酯复合体作为实验组;右足制作胫骨中段骨-骨膜缺损模型后,植入骨髓间充质干细胞/聚己内酯复合体;另取2只犬制作骨-骨膜缺损模型不植入任何材料作为空白对照。术后进行大体、X射线片、组织学、磁共振灌注成像观察骨模具上成骨细胞生长与血管化情况。 结果与结论：空白对照组无新骨生成,无血管长入,最后缺损由纤维瘢痕组织填充;对照组8~16周骨缺损逐渐被骨样组织填充,可见较多的骨痂,骨痂向移植物长入,断端连接不完全,髓腔硬化。实验组成骨过程及速度明显优于对照组,术后6周骨痂量较多,术后8周支架材料已完全降解,术后12周骨缺损完全修复,可见大量松质骨形成,新骨髓腔较通畅,骨皮质连续较牢靠,所形成的血管在数量、孔径和发布上均明显优于对照组。提示组织工程骨有较强、较快修复大动物大段负重骨缺损的能力,而带蒂的筋膜瓣则通过促进其再血管化而使其这种能力得到更好的发挥。