Recent advances in bioprinting techniques: approaches, applications and future prospects.

Bioprinting technology shows potential in tissue engineering for the fabrication of scaffolds, cells, tissues and organs reproducibly and with high accuracy. Bioprinting technologies are mainly divided into three categories, inkjet-based bioprinting, pressure-assisted bioprinting and laser-assisted bioprinting, based on their underlying printing principles. These various printing technologies have their advantages and limitations. Bioprinting utilizes biomaterials, cells or cell factors as a "bioink" to fabricate prospective tissue structures. Biomaterial parameters such as biocompatibility, cell viability and the cellular microenvironment strongly influence the printed product. Various printing technologies have been investigated, and great progress has been made in printing various types of tissue, including vasculature, heart, bone, cartilage, skin and liver. This review introduces basic principles and key aspects of some frequently used printing technologies. We focus on recent advances in three-dimensional printing applications, current challenges and future directions.

Treatment of orbital blowout fracture using porous polyethylene with embedded titanium.

The study was performed to evaluate the effectiveness and safety of porous polyethylene with embedded titanium in the repair of orbital blowout fracture. The study was designed as a prospective case series. Patients who were diagnosed with orbital blowout fracture from May 2012 to March 2013 were included in the study. A composite material of porous polyethylene and titanium mesh was used. Orbital volumes before and after surgery were measured, and the results of diplopia and ocular movement were recorded. The occurrence of diplopia was grouped and compared according to the time interval between injury and surgery. The incidence of other complications was also recorded. A total of 26 patients were involved in the study. The minimal follow-up time was 12 months. All surgeries were performed uneventfully. The orbital volume significantly decreased after the surgery, and the remission rate and the elimination rate of diplopia in 12 months were 85.7% and 47.6%, respectively. Postoperative diplopia was correlated with the time interval between injury and surgery. One patient presented with undercorrection of enophthalmos, and another patient presented with acute aggravation of diplopia and exophthalmos after surgery, which was resolved with treatment. In conclusion, porous polyethylene with embedded titanium was effective and safe in the repair of orbital blowout fracture, and studies with more subjects and longer follow-up period are recommended in future studies.

Repair of orbital bone defects in canines using grafts of enriched autologous bone marrow stromal cells.

BACKGROUND: Bone tissue engineering is a new approach for the repair of orbital defects. The aim of the present study was to explore the feasibility of tissue-engineered bone constructed using bone marrow stromal cells (BMSCs) that were rapidly isolated and concentrated from bone marrow (BM) by the red cell lysis method, then combined with ß-tricalcium phosphate (ß-TCP) to create grafts used to restore orbital bone defects in canines. METHODS: In the experimental group, grafts were constructed using BMSCs obtained by red cell lysis from 20 ml bone marrow, combined with ß-TCP and BM via the custom-made stem cell-scaffold device, then used to repair 10 mm diameter medial orbital wall bony defects in canines. Results were compared with those in groups grafted with BM/ß-TCP or ß-TCP alone, or with defects left untreated as controls. The enrichment of BMSCs and nucleated cells (NCs) in the graft was calculated from the number in untreated bone marrow and in suspensions after red cell lysis. Spiral computed tomography (CT) scans were performed 1, 4, 12 and 24 weeks after implantation in all groups. Gross examination, micro-CT and histological measurements were performed 24 weeks after surgery. The results were analyzed to evaluate the efficacy of bone repair. RESULTS: The number of NCs and of colony-forming units within the scaffolds were increased 54.8 times and 53.4 times, respectively, compared with untreated bone marrow. In the BMSC-BM/ß-TCP group, CT examination revealed that the scaffolds were gradually absorbed and the bony defects were restored. Micro-CT and histological examination confirmed that the implantations led to good repair of the defects, with 6 out 8 orbital defects completely restored in the experimental group, while by contrast, the grafts in the control groups did not fully repair the bony defects, a difference which was statistically significant (p<0.05). CONCLUSIONS: Tissue-engineered bone, constructed using BMSCs isolated by red cell lysis of BM, can restore critical-sized orbital wall defects in canines.

The application and progress of high-density porous polyethylene in the repair of orbital wall defect.

High-density porous polyethylene is a type of polymeric biomaterial. When used to efficiently fill the extensive orbital volume and correct enophthalmos caused by orbital wall defect, it has a significant advantage of biocompatibility, which results in a low rate of postoperative exposure and infection. The major disadvantage of this material is its radiolucency. However, with the development of imaging techniques, it is now possible to use multidetector computed tomography to directly contour the implant and describe its position. The use of tissue engineering involving high-density porous polyethylene will further improve its biocompatibility. At the same time, composite materials will play an important role in the repair of orbital wall defect.

Advances and Prospects in Materials for Craniofacial Bone Reconstruction.

The craniofacial region is composed of 23 bones, which provide crucial function in keeping the normal position of brain and eyeballs, aesthetics of the craniofacial complex, facial movements, and visual function. Given the complex geometry and architecture, craniofacial bone defects not only affect the normal craniofacial structure but also may result in severe craniofacial dysfunction. Therefore, the exploration of rapid, precise, and effective reconstruction of craniofacial bone defects is urgent. Recently, developments in advanced bone tissue engineering bring new hope for the ideal reconstruction of the craniofacial bone defects. This report, presenting a first-time comprehensive review of recent advances of biomaterials in craniofacial bone tissue engineering, overviews the modification of traditional biomaterials and development of advanced biomaterials applying to craniofacial reconstruction. Challenges and perspectives of biomaterial development in craniofacial fields are discussed in the end.

Combination of transorbital and endoscopic transnasal approaches to repair orbital medial wall and floor fractures.

PURPOSE: This study aimed to illustrate the effectiveness of the combination of the transorbital and the endoscopic transnasal approach in the repair of medial wall and floor orbital fractures in Chinese patients. METHODS: A retrospective study was carried out on 25 Chinese patients (18 men and 7 women) with orbital medial wall and floor fractures. All patients had enophthalmos more than 2 mm, 23 had diplopia, and 11 had eye movement restriction. Bone defect involving both medial and inferior walls was found with computed tomographic scans in all patients. In all 25 patients, surgery was done by 1 surgeon group using the transorbital and the endoscope-assisted transnasal approach. The endoscope was used to give a clear view of the posterior edge of the fracture. Titanium meshes were used to repair fractures of the orbital floor and the medial wall. Porous polyethylene sheet implants were used to recover the orbital volume. All patients were followed up 12 months after surgery. RESULTS: Enophthalmos was corrected in all 25 patients immediately, diplopia disappeared or improved in 21 of 23 cases, and eye movement restriction was released or improved in all 11 patients. No significant complications occurred. The titanium mesh was completely covered by nasal mucosa at 1 month after surgery by an endoscopic check. CONCLUSIONS: The endoscope-assisted transnasal approach allows for excellent visualization of the extent of the fracture, particularly in areas that are difficult to visualize by conventional methods. The combination of the transorbital and the endoscope-assisted transnasal approach is a good way to reconstruct a large orbital wall fracture involving the floor and the medial wall.

Repair of exposed hydroxyapatite orbital implants by subconjunctival tissue flaps.

PURPOSE: The purpose of the study was to determine the feasibility of the use of subconjunctival tissue flaps to repair exposed hydroxyapatite (HA) orbital implants. METHODS: One hundred thirty-eight consecutive patients underwent repair of exposed HA orbital implants via a procedure that involved the creation of subconjunctival tissue flaps. After the superior and inferior subconjunctival flaps were created, they were sutured together in the tension-free state to seal the exposure. During follow-up examinations, complications were assessed. RESULTS: Twelve patients were lost after the 3-month follow-up, leaving 126 patients who were followed from 12 to 60 months (average, 24 months). Problems occurred in 22 patients (17.5%), including recurrence of exposure in 4 patients (3.2%), ptosis in 12 patients (9.5%), pyogenic granulomas in 1 patient (0.8%), a conjunctival cyst in 1 patient (0.8%), implant infection in 1 patient (0.8%), and poor transfer of movement in 3 patients (2.4%). CONCLUSIONS: The use of the subconjunctival tissue flaps for repairing exposed HA orbital implants is a promising alternative for the management of implant exposure. Although this novel technique is associated with some complications, these problems can be minimized by careful case selection and careful surgery.

Reconstruction of a tissue-engineered cornea with porcine corneal acellular matrix as the scaffold.

Interest in developing tissue-engineered cornea has increased with the decrease in the supply of donor tissue. The aim of the present study was to investigate the feasibility and method of reconstructing corneal equivalents with porcine corneal acellular matrix as the scaffold in a dynamic culturing system. Applying the detergent Triton X-100 (1%) and a freeze-drying process, porcine corneas were decellularized and prepared as a scaffold, and hematoxylin-eosin staining and scanning electron microscopy showed no cells in the decellularized stroma. In order to measure the in vivo biocompatibility, part of the scaffold was transplanted into a pocket of rabbit corneal stroma and observed for 3 months. No sign of rejection were observed, and the acellular matrix gradually integrated in the rabbit cornea, indicating that the scaffold had good biocompatibility. To reconstruct a tissue-engineered cornea, cultured rabbit keratocytes were seeded into the scaffold. After 1 week of culture in a culturing vessel, rabbit epithelial and endothelial cells were seeded on both sides of the stroma, respectively. The reconstructed cornea consisted of three layers in histological structure: the epithelium, stoma and endothelium. Stratified epithelial cells formed on the surface, which were cytokeratin 3 positive in the cytoplasm; endothelial cell monolayers were located on the inner side, and pump-related aquaporin 1 was found in the cells. These results confirmed that the corneal acellular matrix can be used as a scaffold for tissue-engineered cornea, and a biological corneal equivalent can be reconstructed in a dynamic culturing system.

Distinct antibacterial activity of a vertically aligned graphene coating against Gram-positive and Gram-negative bacteria.

Graphene-based nanomaterials (GBNs) are known to exhibit biocidal activities, however, the combined effect of GBNs based on physical disruption and oxidative stress on different types of bacteria remain unclear. Here, we use both Gram-negative (Escherichia coli and Salmonella typhimurium) and Gram-positive (Staphylococcus aureus and Staphylococcus epidermidis) bacteria to investigate the antimicrobial properties of vertically and horizontally aligned graphenes grown on semiconductor silicon (Si) and insulator silicon dioxide (SiO2). It is found that the bacteria show different sensitivity to isomeric-structured GBNs. Gram-negative bacteria are more vulnerable to graphene-coated Si substrates than to SiO2, because the less negatively charged membrane enhances the electron transfer effect that extracts the electrons from the microbial membranes, and Gram-positive bacteria seem to show more susceptibility to physical puncturing of vertically aligned graphene than to horizontally aligned graphene due to the nature of the compound and the shape of the membrane structure. Subsequently, the vertically aligned graphene Si substrate (G@V-Si) exerts the superior antimicrobial ability on all the bacteria. Finally, all the above GBNs show low cytotoxicity and high biocompatibility, and the robust in vivo antibacterial effect indicates that G@V-Si could serve as an ideal platform for antimicrobial treatment.

[Repairing rabbit orbital defects with human BMP-2 gene modified bone marrow stromal cells and coral].

OBJECTIVE: To investigate the efficacy of tissue-engineered bone (human BMP-2 genetic modified BMSC combined with coral) in healing the segmental orbital defect in rabbits. METHODS: Rabbit BMSC were isolated and cultured in vitro, and cells of passage 2 were infected with adenovirus-mediated transfection of human BMP-2 gene (150 pfu/cell). After infection, the expression of BMP-2 was determined by RT-PCR and Western blot analysis, and cell proliferation and osteogenic differentiation were observed by flow cytometry, ALP and Alizarin red staining. A 12 mm bone defect in the infraorbital rim was induced by surgery in both orbits of 24 New Zealand white rabbits. The defects were repaired with modified tissue-engineered bone constructed with coral plus BMP-2 transfected BMSC (Group A, n = 12), constructed by coral plus non-transfected BMSC (Group B, n = 12) and grafts of coral alone (Group C, n = 12), with untreated group (Group D, n = 12) served as control. The osteogenesis of bone defect was monitored by gross observation, micro-CT measurement, histological and histomorphologic analysis at 4, 8, and 16 weeks after the implantation. RESULTS: After transfection, the BMP-2 expression was confirmed by RT-PCR and western blot, and the osteogenesis activity of BMSC could be obviously enhanced. The 12 mm segmental defect of rabbit orbit couldn't heal alone. Gross observation and micro-CT demonstrated well the bony-union in experimental group, with higher bone mineral density and more bone volume than other control groups (F = ll.46, F = 7180.97; P < 0.05). CONCLUSION: This study demonstrated that the rabbit orbital defect could be successfully repaired by tissue-engineered bone constructed with human BMP-2 gene modified BMSC and coral.

In situ bone regeneration enabled by a biodegradable hybrid double-network hydrogel.

Stem cell therapy based on advanced biomaterials provides a promising strategy in bone tissue engineering. Nevertheless, guided bone regeneration which fulfills the criteria in terms of biomechanics, biodegradability and bioactivity is highly appealing but challenging. Inspired by the superior double-network (DN) structure, herein, a biodegradable hybrid DN hydrogel is proposed to promote in situ bone regeneration. The DN hydrogel is constructed by interspersing a methacrylated gelatin (GelMA) network into a well-defined nanocomposite (NC) hydrogel consisting of methacrylated chitosan (CSMA) and polyhedral oligomeric silsesquioxane (POSS) via a two-step photo-crosslinking process. The hybrid DN hydrogel has the following advantageous characteristics: (i) it exhibits enhanced stiffness and toughness benefiting from the inorganic POSS units and unique energy dissipation; (ii) naturally occurring biomacromolecules (chitosan and gelatin) as the hydrogel framework result in an appropriate biodegradation behavior, which can be replaced by newly formed tissues; (iii) it preferentially guides mesenchymal stem cells (MSCs) toward osteogenic differentiation in vitro by detecting the elevated levels of enzyme activity and calcium deposition along with the up-regulated osteogenesis-related genes and proteins; and (iv) accelerated in situ bone regeneration is observed after implanting MSC-loaded hydrogels into rat calvarial defects. Therefore, we provide a new insight to develop functional hydrogels for triggering specific cellular responses toward stem cell therapy and bone-related tissue engineering.

A biodegradable functional water-responsive shape memory polymer for biomedical applications.

Shape memory polymers (SMPs) have exhibited great potential in biomedical applications. However, the typical triggers of shape recovery such as heat, UV light, and electricity may be harmful to humans. Accordingly, water-responsive SMPs have become significant, especially for in vivo applications, due to the intrinsic biocompatibility and ready availability of water. However, the reported water-responsive SMPs are limited and relatively complicated. Here, we design a new water-responsive SMP, poly(butanetetrol fumarate) (PBF); the properties of PBF could be modulated by curing. The cured PBF scaffolds exhibited high shape recovery and fixity rates (>95%). PBF showed good biodegradability, and it could support the attachment, viability and alkaline phosphatase activity of osteoblasts. Furthermore, PBF could be readily functionalized via pendant hydroxyl groups, which was demonstrated by the immobilization and controlled release of bone morphogenetic protein 2. We expect that PBF will be useful for various biomedical applications including water-responsive scaffolds, sensors or actuators.

Mussel-inspired injectable hydrogel and its counterpart for actuating proliferation and neuronal differentiation of retinal progenitor cells.

Biomaterials-mediated retinal progenitor cell (RPC)-based transplantation therapy has shown substantial potential for retinal degeneration (RD), but it is limited by the poor RPC survival, proliferation and differentiation. Herein, the gelatin-hyaluronic acid (Gel-HA)-based hydrogels formed via moderate Michael-type addition reaction with or without the introduction of mussel-inspired polydopamine (PDA), i.e. Gel-HA-PDA and its counterpart Gel-HA hydrogels are developed, and their effects on the biological behaviour of RPCs, including adhesion, survival, proliferation, differentiation, delivery and migration are investigated. The hybrid hydrogels can adopt the intricate structure of the retina with suitable mechanical strength, degradation rate and biological activity to support cellular adhesion, survival and delivery. Meanwhile, Gel-HA hydrogel can remarkably promote RPC proliferation with much larger cell clusters, while Gel-HA-PDA hydrogel significantly enhances RPC adhesion and migration, and directs RPCs to preferentially differentiate toward retinal neurons such as photoreceptors (the most crucial cell-type for RD treatment), which is mainly induced by the activation of integrin α5ß1-phosphatidylinositol-3-kinase (PI3K) pathway. This study demonstrates that Gel-HA hydrogel possesses great potential for RPC proliferation, while mussel-inspired PDA-modified Gel-HA hydrogel with superior biocompatibility can significantly promote RPC neuronal differentiation, providing new insights for developing biomedical materials applied for RPC-based transplantation therapy.

[Xenogenic corneal acellular matrix as carrier for reconstruction of biological cornea epithelium-scaffold-endothelium compound].

OBJECTIVE: To investigate the method and feasibility of constructing biological cornea by culturing corneal epithelial and endothelial cells on the scaffold of xenogenic corneal acellular matrix (XCAM) in vitro. METHODS: Porcine cornea was prepared as XCAM by application of detergent 1% Triton X-100 and freeze-drying process. After the carrier has rehydrated, rabbit epithelial and endothelial cells were seeded on each side of XCAM. After 2 weeks of culture, the reconstructed tissue of epithelium-scaffold-endothelium compound was examined by histological studies by HE staining and scanning electron microscope (SEM). The epithelium was examined by immunohistochemical studies using antibodies to cytokeratin (CK3), and the endothelium was stained with trypan blue and alizarin red. RESULTS: Reconstructed biological cornea was composed of epithelium, acellular stroma and endothelium. Four to five layers of stratified flat cells were formed on the surface of XCAM, which were stained positively by CK3. Continuous monolayer cells located on the endothelial side, which were alive and showed honeycomb-like shape via dual staining with trypan blue and alizarin red, cells arranged tightly. Under SEM, epithelial cells showed several layers with the morphology of flat and spindle cells alternatively, endothelial cells showed polygonal shape with microvillus over the surface. CONCLUSIONS: The biological corneal tissue reconstructed in vitro possessed three layers: the epithelium, scaffold and the endothelium. XCAM provides ideal surface for corneal epithelial and endothelial cells' adhesion and proliferation, it is desired to be used as scaffold for reconstruction of cornea in vitro.

[The clinical study of lacrimal bypass surgery with high-density porous polyethylene coated tear drain implantation].

OBJECTIVE: To analyze the outcomes of lacrimal bypass surgery using the high-density porous polyethylene (HDPP) coated tear drain and to evaluate the validity and safety of this procedure. METHODS: Twenty-six patients (26 eyes) with severe epiphora who could not be cured by canaliculo-anastomosis and dacryocystorhinostomy were treated by the lacrimal bypass surgery with the HDPP coated tear drain. HDPP tube insertion: 10 patients with defect of the punctum or the canaliculi and in the presence of lacrimal sac were treated by conjunctiva-dacryocystorhinostomy with HDPP coated tear drain implantation. 16 patients with defect of the punctum or the canaliculi and without lacrimal sac were treated by simple HDPP coated tear drain insertion. RESULTS: No tube extrusion or severe malposition occurred after 4 - 28 months follow-up. Complete or significant improvement of epiphora was achieved in 88.5% cases. Most patients (80.8%) satisfied with the therapeutic result of this procedure. Complications included obstruction (9 eyes), discomfort (4 eyes), improper tube length (2 eyes), malposition (1 eye), infection (1 eye), diplopia (1 eye), abrasion of cornea (1 eye) and nasal secretion countercurrent (1 eye). CONCLUSIONS: The lacrimal bypass surgery with the HDPP coated tear drain could be expected to improve epiphora significantly in most cases of lacrimal obstruction. This surgery has a higher successful rate and fewer complications than that of Jones tube insertion and is a safe and efficient procedure.

[A retrospective analysis of 621 cases with craniomaxillofacial fractures].

PURPOSE: To investigate the epidemiological characteristics of 621 hospitalized patients with craniomaxillofacial fractures by a retrospective study. METHODS: From July 2015 to August 2016, the medical records of 621 patients with craniomaxillofacial fractures in Shanghai Ninth People's Hospital were analyzed statistically according to age, gender, etiology and site of fracture. Chi-square test was used to analyze the causes of single and multiple fractures with SPSS 20.0 software package. RESULTS: The male to female ratio was 2.18: 1. The average age was 34.7±15.5 years with 19-29 years old group accounted for the most (28.3%). Traffic accident was the top cause of injury (49.0% ); There were 319 cases of orbital fractures (51.4%), followed by 292 cases of zygomatic complex (47.0%) and 247 cases of mandibular fractures (39.8%). CONCLUSION: The quantity and location of fractures are related to the cause of injury, the nature of stress and anatomical structure of corresponding areas. Establishing a sound system of traffic accident management and related laws is an urgent problem to be solved.

Long-term infectious complications of using porous polyethylene mesh for orbital fracture reconstruction.

Porous polyethylene is a widely used implants in orbital reconstruction, on which comprehensive clinical analysis, various treatments, and different prognosis according to specific classification principles on long-term complications have not been reported.To investigate the new clinical symptoms, intraoperative findings, treatments, and outcomes of complications long period after previous surgery, resulting from the use of porous polyethylene mesh for orbital fracture reconstruction.A retrospective study was conducted on 21 patients at the Department of Ophthalmology, Shanghai Ninth People's Hospital with orbital complications after orbital fracture reconstruction with porous polyethylene mesh for 4 ±â€Š2.2 years from 2011 to 2013. These data included new clinical symptoms after previous surgery, computerized tomography data, intraoperative findings, treatments, and outcomes.Data from 21 patients were analyzed in this study. Two patients received conservative treatment, while the other 19 patients underwent surgical approaches. Classification principles for orbital complications after orbital wall defect reconstruction with porous polyethylene mesh were formulated according to patients' new clinical symptoms, computed tomography (CT), and intraoperative findings after previous surgery. In the last follow-up, 19 patients (90.5%) were cured or improved according to our assessment principle. The follow-up ranged from 3 to 45 months (35 months in average).According to specific classification for orbital complications resulting from the use of porous polyethylene mesh for orbital fracture reconstruction, various medical treatments should be carried out, and the prognosis may be different.

Electrospun silk fibroin/poly(lactide-co-ε-caprolactone) nanofibrous scaffolds for bone regeneration.

BACKGROUND: Tissue engineering has become a promising therapeutic approach for bone regeneration. Nanofibrous scaffolds have attracted great interest mainly due to their structural similarity to natural extracellular matrix (ECM). Poly(lactide-co-ε-caprolactone) (PLCL) has been successfully used in bone regeneration, but PLCL polymers are inert and lack natural cell recognition sites, and the surface of PLCL scaffold is hydrophobic. Silk fibroin (SF) is a kind of natural polymer with inherent bioactivity, and supports mesenchymal stem cell attachment, osteogenesis, and ECM deposition. Therefore, we fabricated hybrid nanofibrous scaffolds by adding different weight ratios of SF to PLCL in order to find a scaffold with improved properties for bone regeneration. METHODS: Hybrid nanofibrous scaffolds were fabricated by blending different weight ratios of SF with PLCL. Human adipose-derived stem cells (hADSCs) were seeded on SF/PLCL nanofibrous scaffolds of various ratios for a systematic evaluation of cell adhesion, proliferation, cytotoxicity, and osteogenic differentiation; the efficacy of the composite of hADSCs and scaffolds in repairing critical-sized calvarial defects in rats was investigated. RESULTS: The SF/PLCL (50/50) scaffold exhibited favorable tensile strength, surface roughness, and hydrophilicity, which facilitated cell adhesion and proliferation. Moreover, the SF/PLCL (50/50) scaffold promoted the osteogenic differentiation of hADSCs by elevating the expression levels of osteogenic marker genes such as BSP, Ocn, Col1A1, and OPN and enhanced ECM mineralization. In vivo assays showed that SF/PLCL (50/50) scaffold improved the repair of the critical-sized calvarial defect in rats, resulting in increased bone volume, higher trabecular number, enhanced bone mineral density, and increased new bone areas, compared with the pure PLCL scaffold. CONCLUSION: The SF/PLCL (50/50) nanofibrous scaffold facilitated hADSC proliferation and osteogenic differentiation in vitro and further promoted new bone formation in vivo, suggesting that the SF/PLCL (50/50) nanofibrous scaffold holds great potential in bone tissue regeneration.

Poly(1,3-propylene sebacate) and Poly(sebacoyl diglyceride): A Pair of Potential Polymers for the Proliferation and Differentiation of Retinal Progenitor Cells.

Using suitable polymers as a carrier for growing and delivering retinal progenitor cells (RPCs) is a promising therapeutic strategy in retinal cell-replacement therapy. Herein recently developed polymer, poly(sebacoyl diglyceride) (PSeD), is selected and its nonhydroxylized counterpart poly(1,3-propylene sebacate) (PPS) is designed to evaluate their potentials for RPC growth and future RPC application. The structures and mechanical properties of the polymers are characterized. The cytocompatibility and effects of these polymers on RPC proliferation, differentiation, and migration are systematically investigated in vitro. Our data show that PPS and PSeD display excellent cytocompatibility with low expression of inflammation and apoptosis factors, which benefit RPC growth. In proliferation assays reveal that RPCs expands well on the polymers, but PPS performs the best for RPC expansion, indicating that PPS can remarkably promote RPC proliferation. In differentiation conditions, RPCs grown on PSeD are more likely to differentiate toward retinal neurons, including photoreceptors, the most interesting type of cells for retinal cell-replacement therapy. Additionally, our results demonstrate that RPCs grown on PSeD display an outstanding ability to migrate. In conclusion, PPS can markedly promote RPC proliferation, whereas PSeD can enhance RPC differentiation toward retinal neurons, suggesting that PSeD and PPS have potential applications in future retinal cell-replacement therapies.

Electrospun nanofibrous SF/P(LLA-CL) membrane: a potential substratum for endothelial keratoplasty.

BACKGROUND: Cornea transplant technology has progressed markedly in recent decades, allowing surgeons to replace diseased corneal endothelium by a thin lamellar structure. A thin, transparent, biocompatible, tissue-engineered substratum with corneal endothelial cells for endothelial keratoplasty is currently of interest. Electrospinning a nanofibrous structure can simulate the extracellular matrix and have beneficial effects for cell culture. Silk fibroin (SF) has good biocompatibility but poor mechanical properties, while poly(L-lactic acid-co-ε-caprolactone) (P(LLA-CL)) has good mechanical properties but poor biocompatibility. Blending SF with P(LLA-CL) can maintain the advantages of both these materials and overcome their disadvantages. Blended electrospun nanofibrous membranes may be suitable for regeneration of the corneal endothelium. The aim of this study was to produce a tissue-engineered construct suitable for endothelial keratoplasty. METHODS: Five scaffolds containing different SF:P(LLA-CL) blended ratios (100:0, 75:25, 50:50, 25:75, 0:100) were manufactured. A human corneal endothelial (B4G12) cell line was cultured on the membranes. Light transmission, speed of cell adherence, cell viability (live-dead test), cell proliferation (Ki-67, BrdU staining), and cell monolayer formation were detected on membranes with the different blended ratios, and expression of some functional genes was also detected by real-time polymerase chain reaction. RESULTS: Different blended ratios of scaffolds had different light transmittance properties. The 25:75 blended ratio membrane had the best transmittance among these scaffolds. All electrospun nanofibrous membranes showed improved speed of cell adherence when compared with the control group, especially when the P(LLA-CL) ratio increased. The 25:75 blended ratio membranes also had the highest cell proliferation. B4G12 cells could form a monolayer on all scaffolds, and most functional genes were also stably expressed on all scaffolds. Only two genes showed changes in expression. CONCLUSION: All blended ratios of SF:P(LLA-CL) scaffolds were evaluated and showed good biocompatibility for cell adherence and monolayer formation. Among them, the 25:75 blended ratio SF:P(LLA-CL) scaffold had the best transmittance and the highest cell proliferation. These attributes further the potential application of the SF:P(LLA-CL) scaffold for corneal endothelial transplantation.