Prospects of polyglycolic acid sheets for the treatment of esophageal stricture after esophageal endoscopic submucosal dissection

Esophageal cancer is the seventh most common type of cancer and the sixth leading cause of cancer-related mortality worldwide.Endoscopic submucosal dissection(ESD)is widely used for the resection of early esophageal cancer.However,post-ESD esophageal stricture is a common long-term complication,which requires attention.Patients with post-ESD esophageal stricture often experience dysphagia and require multiple dilatations,which greatly affects their quality of life and increases healthcare costs.Therefore,to manage post-ESD esophageal stricture,researchers are actively exploring various strategies,such as pharmaceutical interventions,endoscopic balloon dilation,and esophageal stenting.Although steroids-based therapy has achieved some success,steroids can lead to complications such as osteoporosis and infection.Meanwhile,endoscopic balloon dilatation is effective in the short term,but is prone to recurrence and perforation.Additionally,esophageal stenting can alleviate the stricture,but is associated with discomfort during stenting and the complication of easy displacement also present challenges.Tissue engineering has evolved rapidly in recent years,and hydrogel materials have good biodegradability and biocompatibility.A novel type of polyglycolic acid(PGA)sheets has been found to be effective in preventing esophageal stricture after ESD,with the advantages of a simple operation and low complication rate.PGA membranes act as a biophysical barrier to cover the wound as well as facilitate the delivery of medications to promote wound repair and healing.However,there is still a lack of multicenter,large-sample randomized controlled clinical studies focused on the treatment of post-ESD esophageal strictures with PGA membrane,which will be a promising direction for future advancements in this field.

Preparation and Drug-Release Property of Polycaprolactone (PCL)/Polyglycolic Acid (PGA) Composite Masterbatch with Drug of Tea Polyphenols (TPs)

In order to effectively control the drug-release rate of medical textiles,biodegradable polycaprolactone(PCL) and polyglycolic acid(PGA) were blended at various mass ratios to prepare composite masterbatches for medical textiles.The surface morphology and the chemical structure of the masterbatches were analyzed.The crystallization,mass losses,strengths and drug-release rates of the composite masterbatches at different PCL/PGA mass ratios were explored.The results show that the degradation rate of the PGA carrier is obvious higher than that of the PCL carrier,and PCL,PGA and the tea polyphenol(TP) drug just physically mix without chemical reaction.During the degradation,the strength of the composite masterbatches gradually decreases.In addition,the drug-release rates of composite masterbatches at different mass ratios are different,and the more the PGA in the composite masterbatches,the faster the drug release of the composite masterbatches.The drug-release rate of the composite masterbatches can be controlled by adjusting the contents of PCL and PGA.

Surface Modification of Polyglycolic Acid Fibers by Hydrogen Peroxide for Enhancing Hydrophilicity and Cytocompatibility

Hydrogen peroxide( H_2O_2) is applied for surface modification of polyglycolic acid( PGA) fibers in order to enhance the hydrophilicity and cytocompatibility of PGA fibers effectively,and maintain the breaking strength as the same time. PGA fibers are dipped in H_2O_2 solution a certain time for modification. Scanning electron microscopy( SEM) was used to observe the surface morphology of PGA fibers before and after modification. The varying of PGA macromolecule was examined with Fourier transform infrared spectroscopy( FTIR) analyses. X-ray diffraction( XRD) and differential scanning calorimetry( DSC) analysis showed that crystallinity slightly decreases. Mechanical performance test showed tensile force of modified PGA fiber was increased. The water contact angle test indicated the improving of hydrophilic. A cell proliferation assay showed that fibroblast cells attach and proliferate well on the fibers, which meant the modified fibers possess good cytocompatibility. These results suggest that H_2O_2 surface modification is easy to operate and a advantageous modification method for PGA fibers.

Polyglycolic Acid Fibrous Scaffold Improving Endothelial Cell Coating and Vascularization of Islet

Background：Improving islet graft revascularization has become a crucial task for prolonging islet graft survival.Endothelial cells （ECs） are the basis of new microvessels in an isolated islet,and EC coating has been demonstrated to improve the vascularization and survival of an islet.However,the traditional method of EC coating of islets has low efficiency in vitro.This study was conducted to evaluate the effect of a polyglycolic acid （PGA） scaffold on the efficiency of islet coating by ECs and the angiogenesis in the coated islet graft.Methods：A PGA fibrous scaffold was used for EC coating of islet culture and was evaluated for its efficiency of EC coating on islets and islet graft angiogenesis.Results：In in vitro experiments,we found that apoptosis index of ECs-coating islet in PGA group （27% ± 8%） was significantly lower than that in control group （83% ± 20%,P 〈 0.05） after 7 days culture.Stimulation index was significantly greater in the PGA group than in the control group at day 7 after ECs-coating （2.07 ± 0.31 vs.1.80 ± 0.23,P 〈 0.05）.vascular endothelial growth factor （VEGF） level in the PGA group was significantly higher than the coating in the control group after 7 days culture （52.10 ± 13.50 ng/ml vs.16.30 ± 8.10 ng/ml,P 〈 0.05）.Because of a tight,circumvallated,adhesive and three-dimensional growth microenvironment,islet cultured in a PGA scaffold had higher coating efficiency showing stronger staining intensity of enzyme than those in the control group after 14 days of culture following ECs-coating.For in vivo study,PGA scaffold significantly prolonged the average survival time of EC-coated islet graft after transplantation compared with control group （15.30 ± 5.60 days vs.8.30 ± 2.45 days,P 〈 0.05）.The angiogenesis and area of survived grafts were more in the PGA group compared with the control group by measuring the mean microvessel density （8.60 ± 1.21/mm2 vs.5.20 ± 0.87/mm2,P 〈 0.05）.In addition,expression of VEGF and tyrosin-protein kinase receptor （Tie-2） gene increased in PGA scaffold group than that in control group by real-time reverse transcription-polymerase chain reaction analysis.Conclusions：These results demonstrate that the efficiency of EC coating of islets was successfully increased by culturing ECs on a PGA scaffold.This method enhances the function,survival,and vascularization of isolated islets in vitro and in vivo.

In vitro Degradation Study of a Braided Thin-Walled Biodegradable Ureteral Stent

The main disadvantage of conventional ureteral stents commonly used to provide urinary drainage after urological practice is that the patients have to undergo a secondary surgical procedure to remove stents. A new braided thin-walled biodegradable ureteral stent composed of PGA （ polyglycolic acid） and PLGA （ eopolymer of polylactic and polygiycolic acid） mnltifilaments was evaluated in v/tro in this study. In vitro degradation was performed in artificial urine with pH of 5.8 and the temperature of 37~C. The mass loss, mechanical properties, and morphology were observed at different degradaing time intervals of 0, 1, 2, 3, 4, and 5 weeks. The stent had a thinner wail than those of other degradable stents and provided better mechanical properties. The braided thin-walled biodegradable ureteral stents began to degrade after 2 weeks. At the week of 5, the stents were fully degraded. The degradative process of stents is smooth and well controlled.

Repair of acutely injured spinal cord through constructing tissue-engineered neural complex in adult rats

Objective： To construct tissue-engineered neural complex in vitro and study its effect in repairing acutely injured spinal cord in adult rats. Methods： Neural stem cells were harvested from the spinal cord of embryo rats and propagated in vitro. Then the neural stem cells were seeded into polygiycolic acid scaffolds and co-cultured with extract of embryonic spinal cord in vitro. ce histochemistry and scanning electron microscope were used to observe the microstructure of this complex. Animal model of spine semi-transection was made and tissue-engineered neural complex was implanted by surgical intervention. Six weeks after transplantation, functional evaluation and histochemistry were applied to evaluate the functional recovery and anatomic reconstruction. Results： The tissue-engineered neural complex had a distinct structure, which contained neonatal neurons, oligodendrocytes and astrocytes. After tissue-engineered neural complex was implanted into the injured spinal cord, the cell components such as neurons, astrocytes and oligodendrocytes, could survive and keep on developing. The adult rats suffering from spinal cord injury got an obvious neurological recovery in motor skills. Conclusions： The tissue-engineered neural complex appears to have therapeutic effects on the functional recovery and anatomic reconstruction of the adult rats with spinal cord injury.

Experimental study on the adhesion, migration and three-dimensional growth of Schwann cells on absorbable biological materials

OBJECTIVE: To study the adhesion, migration and three-dimentional growth of Schwann cells on PLA (polylactic acid) nonspinning fibre cloth and polyglycolic/polylactic acid (PLGA) fibres. METHODS: Schwann cells/ECM gel solution and PLA nonspinning fibre cloth and PLGA fibres pretreated by collagen, polylysine and ECM were co-cultured. Then the migration and three-dimensional growth of Schwann cells on the fibres were observed under phase contrast microscope and laser scanning confocal microscope. RESULTS: Schwann cell/ECM solution was compounded with PLA nonspinning fibre cloth. With formation of gel, most Schwann cells resided in the fibre net holes, and adhered to the fibres to form a multiplayer-arranged Schwann cell column like Bungner band. Schwann cells could adhere to PLGA fibres and grew and migrated along the fibres. ECM gel could significantly increase the adhering and migrating cell number. CONCLUSIONS: ECM gel can facilitate the adhesion, growth and migration of Schwann cells on the seteroframe. It is a good integrating material for tissue engineering bioartificial nerve.