A highly flexible paclitaxel-loaded poly(ε-caprolactone) electrospun fibrous-membrane-covered stent for benign cardia stricture

Paclitaxel-coated balloon catheter for benign esophageal stenosis in a rabbit model

Most patients with benign esophageal stenosis require multiple or even continuous balloon dilation treatments to achieve symptom relief. In this study, eighteen rabbits were used to establish an esophageal benign stenosis model and were divided into a control group (n = 6), a balloon group (n = 6) and a PTX-coated balloon group (n = 6) to evaluate the feasibility and effectiveness of paclitaxel (PTX)-coated balloons for the rabbit esophageal benign stenosis model. The weight and esophageal diameter were recorded every 2 weeks until 8 weeks post-surgery. Hematoxylin-eosin staining, Masson's trichrome staining and immunohistochemical staining were performed for pathological analysis. Four weeks post-operation, there was a significant difference in weight between the control group and the balloon group (p = 0.01) and between the control group and the PTX balloon group (p = 0.01). There was a significant difference in the esophageal diameter between the balloon group and the PTX balloon group at 8 weeks post-operation (p = 0.02). Four weeks post-operation, the degree of inflammatory cell infiltration in the PTX balloon group was significantly lower than that in the control group (p = 0.002) and balloon group (p = 0.001). The degree of collagen deposition in the PTX balloon group was significantly lower than that in the control group (p = 0.002) and balloon group (p = 0.03). Eight weeks post-operation, the percentage of cells positive for TGF-β (p < 0.001), the degree of inflammatory cell infiltration (p = 0.02) and the degree of collagen deposition (p = 0.02) in the PTX balloon group were significantly lower than those in the balloon group. Therefore, PTX-coated balloons may alleviate the local inflammatory response and collagen deposition when used during dilation treatment of benign esophageal stenosis.

Comprehensive review of materials, applications, and future innovations in biodegradable esophageal stents

Esophageal stricture (ES) results from benign and malignant conditions, such as uncontrolled gastroesophageal reflux disease (GERD) and esophageal neoplasms. Upper gastrointestinal endoscopy is the preferred diagnostic approach for ES and its underlying causes. Stent insertion using an endoscope is a prevalent method for alleviating or treating ES. Nevertheless, the widely used self-expandable metal stents (SEMS) and self-expandable plastic stents (SEPS) can result in complications such as migration and restenosis. Furthermore, they necessitate secondary extraction in cases of benign esophageal stricture (BES), rendering them unsatisfactory for clinical requirements. Over the past 3 decades, significant attention has been devoted to biodegradable materials, including synthetic polyester polymers and magnesium-based alloys, owing to their exceptional biocompatibility and biodegradability while addressing the challenges associated with recurring procedures after BES resolves. Novel esophageal stents have been developed and are undergoing experimental and clinical trials. Drug-eluting stents (DES) with drug-loading and drug-releasing capabilities are currently a research focal point, offering more efficient and precise ES treatments. Functional innovations have been investigated to optimize stent performance, including unidirectional drug-release and anti-migration features. Emerging manufacturing technologies such as three-dimensional (3D) printing and new biodegradable materials such as hydrogels have also contributed to the innovation of esophageal stents. The ultimate objective of the research and development of these materials is their clinical application in the treatment of ES and other benign conditions and the palliative treatment of malignant esophageal stricture (MES). This review aimed to offer a comprehensive overview of current biodegradable esophageal stent materials and their applications, highlight current research limitations and innovations, and offer insights into future development priorities and directions.

Near-Infrared Light-Remote Localized Drug Delivery Systems Based on Zwitterionic Polymer Nanofibers for Combination Therapy

Localized drug delivery systems (LDDS) have gained great interests because they can directly treat the tumors and minimize systematic toxicity, and maximize drug action by controlling release precisely at the tumor site. However, the resistance of the non-specific adsorption of biomolecules is also important to alleviate the inflammatory reactions and avoid the decrease in performance of LDDS. In this study, we develop a near infrared (NIR) light-triggered nanofibrous delivery system consisting of zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine)-b-poly(ε-caprolactone) (PMPC-b-PCL) encapsulated with indocyanine green (ICG) and doxorubicin (DOX) for dual photothermal therapy and chemotherapy. The nanofibrous mat shows hydrophilic characteristics and good antifouling performance. Under mild NIR irradiation, ICG could convert NIR light into thermal energy that elevates the surrounding temperature above 45 °C. This thermal energy also markedly accelerates the DOX release from the nanofibrous mat due to softening of the nanofibers, indicating the drug release could be controlled and switched on/off by light-triggering. Moreover, this light-triggered thermal energy and releasing behavior contribute to enhancing the cell lethality. Intracellular DOX distribution confirms the more drugs release upon light irradiation. All results demonstrate the developed light-triggered drug release nanofibers as LDDS are biocompatible and antifouling as well as has the superior combinational chemotherapy/photothermal therapy.

A review on biodegradable biliary stents: materials and future trends

Biliary stricture is defined as the reduction and narrowing of the bile duct lumen, which can be caused by many factors such as cancer and inflammation. Biliary stent placement can effectively alleviate benign and malignant biliary strictures. However, the commonly used plastic or metallic biliary stents are far from ideal and do not satisfy all clinical requirements，although several types of biodegradable biliary stents have been developed and used clinically. In this review, we summarized current development status of biodegradable stents with the emphasis on the stent materials. We also presented the future development trends based on the published literature.

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Summary of current development status of bioresorbable biliary stents with the emphasis on the stent materials.

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The future development trends based on the published literature.

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The advantages of bioresorbable biliary stents compared with metallic and plastic biliary stents.

Characterization of Partially Covered Self-Expandable Metallic Stents for Esophageal Cancer Treatment: In Vivo Degradation

Partially covered self-expandable metallic esophageal stent (SEMS) placement is the most frequently applied palliative treatment in esophageal cancer. Structural characterization of explanted 16 nitinol-polyurethane SEMS (the group of 6 females, 10 males, age 40-80) was performed after their removal due to dysfunction. The adverse bulk changes in the polymer structure were identified using differential scanning calorimetry (DSC), differential mechanical thermal analysis (DMTA), and attenuated total reflectance infrared spectroscopy (ATR-IR) and discussed in terms of melting point shift (9 °C), glass-transition shift (4 °C), differences in viscoelastic behavior, and systematic decrease of peaks intensities corresponding to C-H, C═O, and C-N polyurethane structural bonds. The scanning electron and confocal microscopic observations revealed all major types of surface degradation, i.e., surface cracks, peeling off of the polymer material, and surface etching. The changes in the hydrophobic polyurethane surfaces were also revealed by a significant decrease in wettability (74°) and the corresponding increase of the surface free energy (31 mJ/m²). To understand the in vivo degradation, the in vitro tests in simulated salivary and gastric fluids were performed, which mimic the environments of proximal and distal ends, respectively. It was concluded that the differences in the degradation of the proximal and distal ends of prostheses strongly depend on the physiological environment, in particular stomach content. Finally, the necessity of the in vivo tests for SEMS degradation is pointed out.

Tissue engineering stent model with long fiber-reinforced thermoplastic technique

This study aims to construct tissue engineering stents by using the long fiber-reinforced thermoplastic (LFT) technique to develop artery stents. The experimental method combines fibers, the LFT technique, and electrospinning technique. First, the biodegradable polyvinyl alcohol yarns are twisted and coated in polycaprolactone/polyethylene glycol blends through the LFT technique. Next, the weft-knitting and heat treatment are used to establish the stent structure, after which poly(ethylene oxide) (PEO) is electrospun to coat the stents. The morphology, mechanical, and biological properties of tissue engineering stents are evaluated. The test results indicated that the use of the LFT technique retains the softness of filaments, which facilitates the subsequent weft-knitting process. The coating of blends and electrospinning of PEO have a positive influence on the tissue engineering stents, as demonstrated by the tensile strength of 59.93 N and compressive strength of 6.10 N. Moreover, the in vitro degradation of stents exhibits a stabilized process. The water contact angle is 20.33°, and the cell survival rate in 24 h is over 80%. The proposed tissue engineering stents are good candidates for artery stent structure.

Dual Delivery of Gemcitabine and Paclitaxel by Wet-Spun Coaxial Fibers Induces Pancreatic Ductal Adenocarcinoma Cell Death, Reduces Tumor Volume, and Sensitizes Cells to Radiation

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis, with surgical resection of the tumor in conjunction with systemic chemotherapy the only potential curative therapy. Up to 80% of diagnosed cases are deemed unresectable, prompting the need for alternative treatment approaches. Herein, coaxial polymeric fibers loaded with two chemotherapeutic agents, gemcitabine (Gem) and paclitaxel (Ptx), are fabricated to investigate the effect of local drug delivery on PDAC cell growth in vitro and in vivo. A wet-spinning fabrication method to form a coaxial fiber with a polycaprolactone shell and alginate core loaded with Ptx and Gem, respectively, is used. In vitro, Gem+Ptx fibers display significant cytotoxicity as well as radiosensitizing properties toward PDAC cell lines greater than the equivalent free drugs, which may be attributed to a radiosensitizing effect of the polymers. In vivo studies assessing Gem+Ptx fiber efficacy found that Gem+Ptx fibers reduce tumor volume in a xenograft mouse model of PDAC. Importantly, no difference in mouse weight, circulating cytokines, or liver function is observed in mice treated with Gem+Ptx fibers compared to the empty fiber controls confirming the safety of the implant approach. With further development, Gem+Ptx fibers can improve the treatment of unresectable PDAC in the future.

Vascular Stents Coated with Electrospun Drug-Eluting Material: Functioning in Rabbit Iliac Artery

A stenting procedure aimed at blood flow restoration in stenosed arteries significantly improves the efficiency of vascular surgery. However, the current challenge is to prevent neointimal growth, which reduces the vessel lumen, in the stented segments in the long run. We tested in vivo drug-eluting coating applied by electrospinning to metal vascular stents to inhibit the overgrowth of neointimal cells via both the drug release and mechanical support of the vascular wall. The blend of polycaprolactone with human serum albumin and paclitaxel was used for stent coating by electrospinning. The drug-eluting stents (DESs) were placed using a balloon catheter to the rabbit common iliac artery for 1, 3, and 6 months. The blood flow rate was ultrasonically determined in vivo. After explantation, the stented arterial segment was visually and histologically examined. Any undesirable biological responses (rejection or hemodynamically significant stenosis) were unobservable in the experimental groups. DESs were less traumatic and induced weaker neointimal growth; over six months, the blood flow increased by 37% versus bare-metal stents, where it increased by at least double the rate. Thus, electrospun-coated DESs demonstrate considerable advantages over the bare-metal variants.

Soft-sheath, stiff-core microfiber hydrogel for coating vascular implants

Vascular implants remain clinically challenged due to often-occurring thrombosis and stenosis. Critical to addressing these complications is the design of implant material surfaces to inhibit the activities of platelets, smooth muscle cells (SMCs) and inflammatory cells. Recent mechanobiology studies accentuate the significance of material elasticity to cells and tissues. We thus developed and characterized an implant coating composed of hybrid, viscoelastic microfibers with coaxial core-sheath nanostructure. The coating over metallic stent material was formed by first depositing coaxially-electrospun fibers of poly(L-lactic acid) core and polyethylene glycol dimethacrylate sheath, and then polymerizing fibers with various UV times. Material characterizations were performed to evaluate the coating structure, mechanical property and biocompatibility. Results showed that coaxial microfibers exhibited arterial-like mechanics. The soft surface, high water content and swelling ratio of the coaxial fibers resemble hydrogels, while they are mechanically strong with an elastic modulus of 172-729 kPa. The coating strength and surface elasticity were tunable with the photopolymerization time. Further, the elastic fibers, as conformal coating on stent metal, strongly reduced SMC overgrowth and discouraged platelet adhesion and activation, compared to bare metals. Importantly, after 7-day subcutaneous implantation, coaxial fiber-coated implants showed more favorable in vivo responses with reduced tissue encapsulation, compared to bare stent metals or those coated with a two-layered fiber mixture composed of fibers from individual polymers. The excellent biocompatibility aroused from nanostructural interfaces of hybrid fibers offering hydrated, soft, nonfouling microenvironments. Such integrated fiber system may allow creation of advanced vascular implants that possess physico-mechanical properties of native arteries.

Electrospun Produced 3D Matrices for Covering of Vascular Stents: Paclitaxel Release Depending on Fiber Structure and Composition of the External Environment

Paclitaxel is a natural, highly lipophilic anti proliferative drug widely used in medicine. We have studied the release of tritium-labeled paclitaxel (³H-PTX) from matrices destined for the coating of vascular stents and produced by the electrospinning method from the solutions of polycaprolactone (PCL) with paclitaxel (PTX) in hexafluoisopropanol (HFIP) and/or solutions of PCL with PTX and human serum albumin (HSA) in HFIP or HIFP-dimethyl sulphoxide (DMSO) blend. The release of PTX has been shown to depend on the composition of electrospinning solution, as well as the surrounding medium, particularly the concentration of free PTX and PTX-binding biomolecules present in human serum. It was shown that 3D matrices can completely release PTX without weight loss. Two-phase PTX release from optimized 3D matrices was obtained: ~27% of PTX was released in the first day, another 8% were released over the next 26 days. Wherein ~2.8%, ~2.3%, and ~0.25% of PTX was released on day 3, 9, and 27, respectively. Considering PTX toxicity, the rate of its diffusion through the arterial wall, and the data obtained the minimum cytostatic dose of the drug in the arterial wall will be maintained for at least three months.

One-Step Fabrication of Three-Dimensional Fibrous Collagen-Based Macrostructure with High Water Uptake Capability by Coaxial Electrospinning

One step fabrication of the three dimension (3D) fibrous structure of Collagen-g-poly(MMA-co-EA)/Nylon6 was investigated by controlling the experimental conditions during coaxial electrospinning. This 3D fibrous structure is the result of interactions of two polymeric systems with a varied capability to be electrostatically polarized under the influence of the external electric field; the solution with the higher conductivity into the inner spinneret and the solution with the lesser conductivity into the outer capillary of the coaxial needle. This set-up was to obtain bimodal fiber fabrication in micro and nanoscale developing a spatial structure; the branches growing off a trunk. The resultant 3D collagen-based fibrous structure has two distinguished configurations: microfibers of 6.9 ± 2.2 µm diameter gap-filled with nanofibers of 216 ± 49 nm diameter. The 3D fibrous structure can be accumulated at an approximate height of 4 cm within 20 min. The mechanism of the 3D fibrous structure and the effect of experimental conditions, the associated hydration degree, water uptake and degradation rate were also investigated. This highly stable 3D fibrous structure has great potential end-uses benefitting from its large surface area and high water uptake which is caused by the high polarity and spatial orientation of collagen-based macrostructure.

High Performance of Covalently Grafting onto Collagen in The Presence of Graphene Oxide

A collagen-based copolymer, ASC-g-Poly(methyl methacrylate-co-Ethyl Acrylate), was synthesized in the presence of Graphene Oxide (GO) via an in-situ polymerization. The presence of GO that increased the accessible surface area for initiated collagen chains allowed for an accelerated polymerization with highly improved grafting performance and efficiency. This was conducted from two polymerization systems with varied comonomer feed ratios, in which two distinguished GO loadings were used. The processability of the achieved nanocomposite was then evaluated through casting and electrospinning processing methods. Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis spectroscopy, Differential Scanning Calorimeter (DSC), Thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), Transmission electron microscopy (TEM), and tensile analysis were conducted to characterize the GO-ASC-g-P(MMA-co-EA). The nanocomposite films showed a unique morphology, multilayer nanostructure of the grafted GO monolayers that deposited simultaneously one on top of another. The morphology of the electrospun fibers was affected by the addition of GO loadings in which the increase in fiber diameter was observed while the surface of the nanofibers was decorated by the GO nanolayers. To modify the collagen, this research highlights the importance of introducing functional groups of GO and the substitution of GO loadings as an active nanostructure filler to highly monomer feed ratios improving the physiochemical properties of collagen. This easy-to-apply approach is suggested for applications intending the mechanical properties and deterred degradation of Collagen-based materials.

Localized Controlled Delivery of Gemcitabine via Microsol Electrospun Fibers to Prevent Pancreatic Cancer Recurrence

The low radical surgery rate of pancreatic cancer leads to increased local recurrence and poor prognosis. Gemcitabine (GEM) is the preferred chemotherapeutic for pancreatic cancer. However, systemic chemotherapy with GEM has reached a bottleneck due to its serious side effects after frequent injections. In this study, GEM is successfully enwrapped into electrospun fibers via microsol electrospinning technology to form a stable core-shell fibrous structure. The GEM release rate can be adjusted by altering the thickness of the hyaluronan-sol inner fiber and the quantity of loaded GEM, and the release can be sustained for as long as three weeks. In vitro assays show that these electrospun fibers effectively inhibit pancreatic cancer cells and promote apoptosis. In vivo studies show that the fibrous membranes are better for inhibiting the growth of residual tumors than that of integrated tumors. Furthermore, immunohistochemistry results show that GEM-loaded fibers promote a higher cell apoptosis rate than does systemically injected GEM in residual tumors. In addition, the local delivery of GEM with fibers significantly reduces liver toxicity. In summary, a core-shell electrospun fiber for the controlled and localized delivery of GEM, which greatly improves the treatment of residual tumors and prevents pancreatic tumor recurrence, is developed.

Multiscale bioprinting of vascularized models

A basic prerequisite for the survival and function of three-dimensional (3D) engineered tissue constructs is the establishment of blood vessels. 3D bioprinting of vascular networks with hierarchical structures that resemble in vivo structures has allowed blood circulation within thick tissue constructs to accelerate vascularization and enhance tissue regeneration. Successful rapid vascularization of tissue constructs requires synergy between fabrication of perfusable channels and functional bioinks that induce angiogenesis and capillary formation within constructs. Combinations of 3D bioprinting techniques and four-dimensional (4D) printing concepts through patterning proangiogenic factors may offer novel solutions for implantation of thick constructs. In this review, we cover current bioprinting techniques for vascularized tissue constructs with vasculatures ranging from capillaries to large blood vessels and discuss how to implement these approaches for patterning proangiogenic factors to maintain long-term, stimuli-controlled formation of new capillaries.

pH/NIR-Responsive Polypyrrole-Functionalized Fibrous Localized Drug-Delivery Platform for Synergistic Cancer Therapy

Localized drug-delivery systems (LDDSs) are a promising approach for cancer treatment because they decrease systematic toxicity and enhance the therapeutic effect of the drugs via site-specific delivery of active compounds and possible gradual release. However, the development of LDDS with rationally controlled drug release and intelligent functionality holds great challenge. To this end, we have developed a tailorable fibrous site-specific drug-delivery platform functionalized with pH- and near-infrared (NIR)-responsive polypyrrole (PPy), with the aim of cancer treatment via a combination of photothermal ablation and chemotherapy. First, a paclitaxel (PTX)-loaded polycaprolactone (PCL) (PCL-PTX) mat was prepared by electrospinning and subsequently in situ membrane surface-functionalized with different concentrations of PPy. The obtained PPy-functionalized mats exhibited excellent photostability and heating property in response to NIR exposure. PPy-coated mats exhibited enhanced PTX release in a pH 5.5 environment compared to pH 7.4. Release was further accelerated in response to NIR under both conditions; however, superior release was observed at pH 5.5 compared to pH 7.4, indicating a dual stimuli-responsive (pH and NIR) drug-delivery platform. More importantly, the 808 nm NIR irradiation enabled markedly accelerated PTX release from PPy-coated PCL-PTX mats and slowed and sustained release following termination of laser irradiation, confirming representative stepwise drug-release properties. PPy-coated PCL-PTX mats presented significantly enhanced in vitro and in vivo anticancer efficacy under NIR irradiation compared to PPy-coated PCL-PTX mats not exposed to NIR or uncoated mats (PCL-PTX). This study has thus developed a promising fibrous site-specific drug-delivery platform with NIR- and pH-triggering that notably utilizes PPy as a dopant for synergistic photothermal chemotherapy.

Surface modification of esophageal stent materials by a polyethylenimine layer aiming at anti-cancer function

Esophageal cancer is difficult to cure globally and possesses high mortality rate, and it is generally accepted that palliative care such as stent implantation is the main therapy method for esophageal cancer in later period. However, the restenosis caused by tumor cells and inflammatory cells seriously interferes the stent clinical application and limits its long-term services. To solve this problem, series of drug delivery stents were developed and proven rather effective in the early stage of implantation, but more serious restenosis occurred after the drug delivery was over, which endangered the patients' life. Therefore, endowing the esophageal stent continuous anti-cancer function become an ideal strategy for inhibiting the restenosis. In this contribution, the functional layer composed of polydopamine (PDA) and Poly-ethylenimine (PEI) with series of molecular weights (MW, 1.8 × 10³, 1 × 10⁴, 2.5 × 10⁴ and 7 × 10⁴ Da) were fabricated onto the esophageal stent material 317L stainless steel (317L SS) surface. The surface characterization including amine quantitative, atomic force microscopy (AFM) and water contact angle measurement indicated successful preparation of the PDA/PEI layer. The Eca109 cells culture results proved that the PDA/PEI layers significantly improve Eca109 cells apoptosis and necrosis, suggesting excellent anti-cancer function. In addition, we also found that the anti-cancer function of the PDA/PEI layers was positively correlated to the immobilized PEIs' MW. All the results demonstrated the potential application of the PDA/PEI layers on the surface modification of esophageal stent for continuous anti-cancer function. It is generally accepted that the restenosis caused by tumor cells seriously interferes the esophageal stent clinical application. Thus, endowing the esophageal stent continuous anti-cancer function is the ideal strategy for inhibiting the restenosis. In this work, we fabricated functional layers composed of polydopamine (PDA) and Poly-ethylenimine (PEI) with series of molecular weights (MW, 1.8 × 10³, 1 × 10⁴, 2.5 × 10⁴ and 7 × 10⁴ Da) onto the esophageal stent material 317L stainless steel (317L SS) surface to inhibit the tumor cells growth, and this function was related to the PEIs' molecular weights. The functional PDA/PEI layers were expected potentially applied for surface modification of esophageal stent materials.

Effect of Resveratrol on Modulation of Endothelial Cells and Macrophages for Rapid Vascular Regeneration from Electrospun Poly(ε-caprolactone) Scaffolds

Rapid endothelialization is a key factor that determines the success of small-diameter vascular grafts as an artery substitute in the treatment of cardiovascular diseases. Aimed to facilitate vascular regeneration, we developed a vascular scaffold loaded with resveratrol, which is a natural compound extracted from plants and showed multifaceted effects in cardiovascular protection. The tubular poly(ε-caprolactone) (PCL) scaffold was prepared by electrospinning with resveratrol in the PCL solution. In vitro assay demonstrated that resveratrol could be released from the scaffolds in a sustained and controlled manner. Cell culture results indicated that the migration of endothelial cells (ECs), nitric oxide production, and the ability of tube formation increased in the resveratrol-containing PCL scaffold groups compared with the PCL control. Meanwhile, the level of tumor necrosis factor (TNF)-α, the main proinflammatory factor secreted from macrophages, was reduced, and the messenger RNA expressions of the M2 macrophage-related genes were increased in the resveratrol-containing group. Further, in vivo implantation was performed by replacing rat abdominal aorta. We observed fast endothelialization and enhanced vascular regeneration in rats with resveratrol-containing scaffolds. The presence of resveratrol also induced a large number of M2 macrophages to infiltrate into the graft wall. Taken together, the incorporation of resveratrol into the PCL grafts enhanced the vascular regeneration by modulation of ECs and macrophages.

Electrospun polymeric micro/nanofibrous scaffolds for long-term drug release and their biomedical applications

Electrospun polymeric micro/nanofibrous scaffolds have been investigated extensively as drug delivery platforms capable of controlled and sustained release of therapeutic agents in situ. Such scaffolds exhibit excellent physicochemical and biological properties and can encapsulate and release various drugs in a controlled fashion. This article reviews recent advances in the design and manufacture of electrospun scaffolds for long-term drug release, placing particular emphasis on polymer selection, types of incorporated drugs and the latest drug-loading techniques. Finally, applications of such devices in traumatic or disease states requiring effective and sustained drug action are discussed and critically appraised in their biomedical context.

Design of a Bioabsorbable Multilayered Patch for Esophagus Tissue Engineering

A gold standard for esophagus reconstruction is not still available. The present work aims to design a polymer patch combining synthetic polylactide-co-polycaprolacton and chitosan biopolymers, tailoring patch properties to esophageal tissue characteristics by a temperature-induced precipitation method, to get multilayered patches (1L, 2L, and 3L). Characterization shows stable multilayered patches (1L and 2L) by selection of copolymer type, and their M _w . In vitro investigation of the functional patch properties in simulated physiologic and pathologic conditions demonstrates that the chitosan layer (patch 3L) decreases patch stability and cell adhesion, while improves cell proliferation. Patches 2L and 3L comply with physiological esophageal pressure (3-5 kPa) and elongation (20%).

History of the Use of Esophageal Stent in Management of Dysphagia and Its Improvement Over the Years

The art and science of using stents to treat dysphagia and seal fistula, leaks and perforations has been evolving. Lessons learnt from the deficiencies of previous models led to several improvements making stent deployment easier, and with some designs, it was also possible to remove the stents if needed. With these improvements, besides malignant dysphagia, newer indications for using stents emerged. Unfortunately, despite several decades of evolution, as yet, there is no perfect stent that "fits all." This article is an overview of how this evolution process happened and where we are currently with using stents to manage patients with dysphagia and with other esophageal disorders.

Polymeric Biodegradable Stent Insertion in the Esophagus

Esophageal stent insertion has been used as a well-accepted and effective alternative to manage and improve the quality of life for patients diagnosed with esophageal diseases and disorders. Current stents are either permanent or temporary and are fabricated from either metal or plastic. The partially covered self-expanding metal stent (SEMS) has a firm anchoring effect and prevent stent migration, however, the hyperplastic tissue reaction cause stent restenosis and make it difficult to remove. A fully covered SEMS and self-expanding plastic stent (SEPS) reduced reactive hyperplasia but has a high migration rate. The main advantage that polymeric biodegradable stents (BDSs) have over metal or plastic stents is that removal is not require and reduce the need for repeated stent insertion. But the slightly lower radial force of BDS may be its main shortcoming and a post-implant problem. Thus, strengthening support of BDS is a content of the research in the future. BDSs are often temporarily effective in esophageal stricture to relieve dysphagia. In the future, it can be expect that biodegradable drug-eluting stents (DES) will be available to treat benign esophageal stricture, perforations or leaks with additional use as palliative modalities for treating malignant esophageal stricture, as the bridge to surgery or to maintain luminal patency during neoadjuvant chemoradiation.

Upregulating Hif-1α by Hydrogel Nanofibrous Scaffolds for Rapidly Recruiting Angiogenesis Relative Cells in Diabetic Wound

Nonhealing chronic wounds on foot are one of the most dreaded complications of diabetes, and biomedical scaffolds remain an attractive option for repairing or regenerating tissues. Accelerating angiogenesis in the early stage after injury is critical to wound healing process; however, the scaffolds accelerate the angiogenesis in the beginning but with the acceleration of vessel network formation the scaffold network hinders the process. In this study, the water soluble drugs-loaded hydrogel nanofibrous scaffolds are designed for rapidly recruiting angiogenesis relative cells and promoting wound healing. The sustained release profile of desferrioxamine (DFO), which continues for about 72 h, leads to significantly increase of neovascularization. The majority of the scaffold is degraded in 14 d, leaving enough space for cell proliferation and vessel formation. The in vitro results show that the scaffolds upregulate the expression of Hif-1α and vascular endothelial growth factor, and enhance the interaction between fibroblasts and endothelial cells. The in vivo studies show a higher expression of angiogenesis related cytokines. This study demonstrates that the DFO released from hydrogel nanofibrous scaffolds of quick degradation can interfere with the required prolyl-hydroxylases cofactors by acting as Fe(2+) chelator and upregulate the expression of Hif-1α, leading to a significant increase of the neovascularization.

The metamorphosis of vascular stents: passive structures to smart devices

The role of nanotechnology enabled techniques in the evolution of vascular stents.

Fabrication and investigation of nanofibrous matrices as esophageal tissue scaffolds using human non-keratinized, stratified, squamous epithelial cells

Clinical conditions of the esophagus are conventionally treated by autologous grafts and are generally associated with complications such as leakage, infection and stenosis necessitating an alternative synthetic graft with superior outcomes.

Multilayered electrospun fibrous meshes for restenosis-suppressing metallic stents

Nanofiber is a flexible and highly porous mesh that is advantageous for coating bare metal stent and local drug delivery. Herein, we developed drug-eluting stent coated with PCL/PU blending coaxial nanofiber for controlling drug release manner and suppressing in-stent restenosis, which is a representative side effect of stenting surgery. The shell of coaxial electrospun nanofibrous are composed of poly (ε-caprolactone) (PCL) and polyurethane (PU) for biodegradability and elasticity to the polymeric coating of stent. Paclitaxel (PTX) is loaded into both the core and shell through electrospinning using coaxial nozzle with different weight ratio. The morphology of nanofiber-coated stent, expansion state, and core/shell structure of nanofiber were visualized by scanning electron microscope and transmission electron microscope. As more amount of PCL/PU was infused from the outer nozzle, PTX release speed from the nanofiber was increased. And PTX suppressed L6 cell proliferation in vitro expecting potential possibility of PTX-loaded coaxial nanofiber as a drug-eluting stent coating material. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 628-635, 2017.

Creation of a functional graded nanobiomembrane using a new electrospinning system for drug release control and an in vitro validation of drug release behavior of the coating membrane

Functional graded nanobiomembranes (FGMs) with multiple layers were created by a single process using a novel electrospinning system equipped with a generator and a PCI type motion board as a controller in order to control the drug release rate. By varying physical apparatus-related parameters such as nozzle-to-collector distance via a robot and the collector moving velocity the FGMs were formed. For the membrane base layer, poly-(ε-caprolactone) (PCL) with paclitaxel (PTX) was dissolved in a solvent (dichloromethane, N,N-dimethylformamide) and electrospun. For the top layers, the PCL solution was electrospun according to the distance and FGM system parameters, which can move the collector location at a constant ratio. It was observed that pore size, porosity, and permeability were higher when the membrane was spun at the far distance. The top surface of FGM is more porous, rougher, more permeable, and more hydrophilic so as to be active to the surrounding tissue cells. Meanwhile, the porous inside membrane was as low as the membrane spun at a close distance. Thus it induced a slow drug release due to the internal structure of FGM, which is considered to be very effective for slow drug release as well as bioactivity and bioconductivity.

Electrospun anisotropic architectures and porous structures for tissue engineering

Recent advances in electrospun anisotropic architectures and porous structures, as well as their applications in tissue engineering, are presented.

A hierarchical, stretchable and stiff fibrous biotemplate engineered using stagger-electrospinning for augmentation of rotator cuff tendon-healing

The regeneration of fibrocartilage at the tendon-bone insertion site in rotator cuff tears (RCTs) is challenging due to the complexity of its composition and mechanical properties. In this study, hierarchical, stretchable and stiff fibrous scaffolds composed of microfibers of poly(ε-caprolactone) (PCL) and nanofibers of chitosan (CS) were fabricated using stagger-electrospinning for the augmentation of RCT-healing. It was found that the composite PCL-CS scaffolds had significantly improved strength and failure strain compared to the control CS scaffolds and increased stiffness compared to the control PCL scaffolds. These scaffolds also showed enhanced hydrophilicity, water absorption and a faster degradation rate compared to the PCL scaffolds. Moreover, they demonstrated better fibroblast attachment and proliferation compared to the PCL scaffolds. Radiological and histological analysis revealed that the PCL-CS scaffolds enhanced new bone formation (mineralization) and collagen and glycosaminoglycan expression (major components of extracellular matrix) compared to the PCL scaffolds. Furthermore, the torn tissues at the tendon-bone insertion site regenerated with the PCL-CS scaffolds showed higher strength and failure strain as well as stiffness compared to those repaired using only the PCL scaffolds. The above mentioned results suggest that the hierarchical, stretchable and stiff fibrous scaffolds engineered using stagger-electrospinning have great potential for the augmentation of RCT-healing.

Prototype of biliary drug-eluting stent with photodynamic and chemotherapy using electrospinning

Background

The combination of biliary stent with photodynamic and chemotherapy seemed to be a beneficial palliative treatment of unresectable cholangiocarcinoma. However, by intravenous delivery to the target tumor the distribution of the drug had its limitations and caused serious side effect on non-target organs. Therefore, in this study, we are going to develop a localized eluting stent, named PDT-chemo stent, covered with gemcitabine (GEM) and hematoporphyrin (HP).

Methods

The prototype of PDT-chemo stent was made through electrospinning and electrospraying dual-processes with an electrical charge to cover the stent with a drug-storing membrane from polymer liquid. The design of prototype used PU as the material of the backing layer, and PCL/PEG blends in different molar ratio of 9:1 and of 1:4 were used in two drug-storing layers with GEM and HP loaded respectively.

Results

The optical microscopy revealed that the backing layer was formed in fine fibers from electrospinning, while drug-storing layers, attributed to the droplets from electrospraying process. The covered membrane, the morphology of which was observed by scanning electron microscopy (SEM), covered the stent surface homogeneously without crack appearances. The GEM had almost 100% of electrosprayed efficiency than 70% HP loaded on the covered membrane due to the different solubility of drug in PEG/PCL blends. Drug release study confirmed the two-phased drug release pattern by regulating in different molar ratio of PEG/PCL blends polymer.

Conclusions

The result proves that the PDT-chemo stent is composed of a first burst-releasing phase from HP and a later slow-releasing phase from GEM eluting. This two-phase of drug eluting stent may provide a new prospect of localized and controlled release treatment for cholangiocarcinoma disease.

Highly flexible and rapidly degradable papaverine-loaded electrospun fibrous membranes for preventing vasospasm and repairing vascular tissue

Vasospasm is a common post-operative complication after vascular anastomosis. Currently, the main treatment is a local injection of antispasmodic drugs. However, this method has a high rate of relapse and is subject to a large degree of individual variation, and repeated injections cause additional pain for patients. In this study, we developed highly flexible and rapidly degradable papaverine-loaded electrospun fibrous membranes to be wrapped around vascular suturing to prevent vasospasm. Poly-l-lactic acid/polyethylene glycol (PLLA/PEG) electrospun fibers containing papaverine maintained a high degree of flexibility and could withstand any folding, and are therefore suitable for wrapping vascular suturing. A rapid release of papaverine, between 2 and 7 days, was achieved by adjusting the proportions of PEG and PLLA. PLLA electrospun fibers containing 40% PEG (PLLA-40%) could control drug release and polymer degradation most effectively during the first 2 weeks post-operation. Testing using an in vivo rabbit model showed that PLLA-40% fibrous membranes produced significant antispasmodic effect without observable inflammation or hyperplasia, and the fibrous membranes were ideally biodegradable, with no impact on regional blood flow, pressure, vessel diameter or surrounding tissue hyperplasia. Therefore, papaverine-loaded electrospun fibrous membranes show the potential to greatly reduce post-operative vasospasm and maintain regular vascular morphology during antispasmodic therapy.

Gold nanorod-embedded electrospun fibrous membrane as a photothermal therapy platform

A strategy of using a gold nanorod (GNR)-loaded electrospun membrane as a photothermal therapy platform of cancer is reported. The strategy takes both the advantages of the excellent photothermal properties of GNRs to selectively kill the cancerous cells, and the widely used biodegradable electrospun membrane to serve as GNR-carrier and surgical recovery material. PEG modified GNRs were embedded into the electrospun fibrous membrane which was composed of PLGA and PLA-b-PEG with an 85:15 ratio. After incubation with the cells in the cell culture medium, the PEG-GNRs were released from the membrane and taken up by cancer cells, allowing the generation of heat upon NIR irradiation to induce cancer cell death. We have demonstrated that the use of PEG-GNR-embedded membrane selectively killed the cancerous cells and effectively inhibited cancer cell proliferation though in vitro experiments. The PEG-GNRs-loaded membrane is a promising material for postsurgical recovery of cancer.

In vitro and in vivo evaluation of Rapamycin-eluting nanofibers coated on cardia stents

Diagram of the process used to fabricate non-biodegradable metal stents with an outer layer of Rapa-loaded fibrous membrane using the electrospinning process. With the release of Rapa, the stents are expected to inhibit fibroblast proliferation and tissue hyperplasia, therefore treating a benign cardia stricture.