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Stent insertion can serve as an effective therapy method for patients with esophageal stricture but stents with inappropriate mechanical properties lead to restenosis. To prepare a stent matching the esophageal environmental mechanics, both the NiTi spring yarn and polyester multifilament were used to produce seven kinds of stents by braiding technology. The mechanical properties of the stents were tested including compression, flexibility, and antimigration behavior. Results showed that three different parameters including spring consistency with tracks, spring content, and spring pitch altered the effective number of coils and elastic modulus, and affected the compression strength, flexibility and migration resistance of the stent. In particular, the integrated braided stent with full consistency, 12 NiTi spiral yarns, and spring pitch of 1.00 mm had the best mechanical properties among all the prototypes in this research. The compression strength, bending strength, and migration resistance were 1048.75 cN, 46.35 cN, and 3.74 N, respectively. In summary, this research presents a new preparation method for esophageal stent manufacture in the treatment of inoperable esophageal malignancies.

Rapid formation of a continuous endothelial cell (EC) monolayer with healthy endothelium function on the luminal surface of vascular implants is imperative to improve the longtime patency of small-diameter vascular implants. In the present study, we combined the contact guidance effects of aligned nanofibers, which enhance EC adhesion and proliferation because of its similar fiber scale with native vascular basement membranes, and aligned microfibers, which could induce EC elongation effectively and allow ECs infiltration. It was followed by successive immobilization of collagen IV and laminin to fabricate a biomimetic basement membrane (BBM) with structural and compositional biomimicry. The hemolysis assay and platelet adhesion results showed that the BBM exhibited excellent hemocompatibility. Meanwhile, the adhered human umbilical vein endothelial cells (HUVECs) onto the BBM aligned along the orientation of the microfibers with an elongated morphology, and the data demonstrated that the BBM showed favorable effects on EC attachment, proliferation, and viability. The oriented EC monolayer formed on the BBM exhibited improved antithrombotic capability as indicated by higher production of nitric oxide and prostacyclin (PGI2). Furthermore, fluorescence images indicated that HUVECs could infiltrate into the BBM, implying the BBM’s ability to enhance transmural endothelialization. Hence, the BBM possessed the properties to regulate EC behaviors and allow transmural ingrowth, demonstrating the potential to be applied as the luminal surface of small-diameter vascular implants for rapid endothelialization.

Several studies found that hip fracture patient outcome is greatly influenced by the time from admission to surgery. To avoid surgical delay, surgery for hip fracture may be performed at night or weekends. However, after-hours surgery may lead to a reduction in support staff and to surgeon fatigue, which ultimately increases mortality and complications. Therefore, we wanted to compare the outcomes of daytime and after-hours surgery in hip fracture patients. A literature search was performed in the Cochrane Library, and the Web of Science, PubMed, Embase, and Springer databases from inception to December 2019. Relevant studies comparing the results of operations performed at different time periods were included. The main clinical outcomes included total complications, mortality, blood loss, surgical time, and length of hospitalization. Data were pooled, and a meta-analysis was completed. Nine retrospective cohort studies and one randomized controlled trial met the inclusion criteria; the studies included a total of 583,290 patients. We found no significant differences in mortality, surgical time or blood loss between daytime and after-hours surgery in hip fracture patients (P > 0.05). Of note, the patients who underwent after-hours surgery had fewer surgical complications (P

Orthopedic suture, as an implantable surgical device for skeletal and soft tissue connection, is vital in tendon or ligament injury repair. Resorbable therapy approaches exhibit excellent biocompatibility in the field of suture materials but lack a long-term fixation effect in orthopedic treatment. Herein, this study focused on a series of partially absorbable orthopedic sutures, which were composed of absorbable polycaprolactone (PCL) multifilament and non-absorbable ultra-high molecular weight polyethylene (UHMWPE) multifilament. Comprehensive in vitro mechanical evaluations were conducted to probe the relationship between material composition and mechanical properties of the sutures. The results showed that the partially absorbable sutures, especially P/U = 50/50 and P/U = 25/75, exhibited significant improvements in mechanical properties compared to single-material sutures. The tensile strength of P/U = 50/50 and P/U = 25/75 was 180.99 and 210.91 N, respectively, which was about two times higher than that of absorbable PCL suture P/U = 100/0 (62.42 N). Furthermore, their suture-to-suture friction force was 1.89 times and 2.51 times that of non-absorbable UHMWPE suture P/U = 0/100, respectively, which guaranteed good knot security. Compared with the clinically used orthopedic suture Ethibond (110 N), P/U = 50/50 and P/U = 25/75 also presented superior tensile properties. Notably, P/U = 50/50 and P/U = 25/75 had similar tensile curves to that of the native tendon/ligament, which might be beneficial to tissue healing. Moreover, the R2 of Eyring's model to simulate the creep curves of each suture was higher than 0.99, which indicated that Eyring's model could be used in predicting the long-term creep behavior of the sutures.

Stents or stent-grafts are often functionalized with films to enhance cell/surface interactions and improve endothelialization. However, continuous film coatings by common surface modification tactics may preclude cells from migrating along the thickness direction and may change the physical characteristics of stent-grafts. Here, polydopamine nanoparticles (PDA-NPs) are attached on braided stent-grafts tightly, forming a nanostructure on microfilaments. They also serve as the anchor for bioactive REDV peptide immobilization to promote endothelia cells (ECs) activities. The results show that braided stent-grafts decorated with PDA-NPs and REDV demonstrate an excellent endothelialization performance and hemocompatibility due to the micro/nanostructure formed and REDV affinity to ECs. The physical properties of stent-grafts are also not compromised. A potential surface modification strategy for scaffold applications is illustrated.

A PVA/PAAm (polyvinyl alcohol/polyacrylamide) hydrogel vascular graft reinforced by a braided fiber stent was prepared in the present work, and a series of characterizations were carried out for evaluating the comprehensive performance of the reinforced hydrogel vascular graft (RHVG), including the morphology, the mechanical properties and the biocompatibility. The results show that hydrogel with a mass ratio of 5:8 (PVA:PAAm) is the best candidate for developing an implantation-oriented vascular graft, whose overall performance is the closest to the requirements of clinical applications. The surface of the PVA/PAAm hydrogel is smooth, and the porous structure is uniform and stable. When the longitudinal strain of the RHVG was 50%, the tensile strength reached 905.6 ± 63.1 kPa, much higher than that of a swine common carotid artery (185 kPa). Moreover, the circumferential tensile strength was significantly enhanced by the integration of the stent, and the circumferential compression recovery reached 93.4 ± 6.7%, showing satisfactory structural stability. Furthermore, the suture retention force approached (9.89 ± 0.64 N), higher than that of a canine femoral artery (7.90 ± 0.36 N). More importantly, the radial dynamic compliance reached 3.11 ± 0.09% under testing pressure of 80–120 mmHg, which is 6.9 times that of a commercial expanded polytetrafluoroethylene vascular graft. Lastly, the RHVG has satisfying cytocompatibility and a low hemolysis rate. In summary, the present work may pave the way for developing a novel small-diameter vascular graft for clinical implantation.

Water permeability of textile vascular grafts has been considered as a key indicator for predicting blood permeability after implantation. However, a correlation between water and blood permeability has not been established yet. Therefore, even though the water permeability of a vascular graft can be tested according to the standard ISO 7198, the results fail to guide a manufacturer or a surgeon to judge whether this vascular graft needs pre-clotting or not prior to implantation. As a result, all commercial graft products show almost zero water permeability, which leads to the loss of advantages that textile vascular grafts have the pore size-controlled porous wall. To solve this problem, four types of woven vascular grafts were designed and manufactured in the present work. Then their permeability to water, simulated plasma, and anticoagulated whole blood were measured at graded pressures from 8 to 16 kPa. Moreover, the correlations among the water permeability, the simulated plasma permeability, and the anticoagulated whole blood permeability were established. The results suggest that relatively steady correlations exist between the water permeability and the anticoagulated whole blood permeability, and that the evaluation of the blood permeability using the water permeability is feasible and objective. The present work provides a quantitative method for evaluating the blood permeability using the water permeability, and the latter is thus endowed with practical significance for guiding designs and clinical pre-clotting operations of textiles vascular grafts.

Developing a small-diameter vascular graft with a satisfactory performance in terms of mechanical and biological properties remains a challenging issue because of comprehensive requirements from clinical applications. Polyvinyl alcohol (PVA)/polyacrylamide (PAAm) hydrogels exhibit many desirable characteristics for small-diameter vascular grafts because of their tunable mechanical properties, especially high compliance. However, poor cells adhesion hinders their application for endothelialization in situ. Therefore, in the present work, polydopamine (PDA) and tetrapeptide Arg-Glu-Asp-Val (REDV) were used to functionalize the hydrogels surface and improve cells adhesion. A series of characterizations were systematically conducted to examine the applicability of coated hydrogels to small-diameter vascular grafts. Results showed that bare and coated hydrogels have appropriate structural stability, and no significant differences in tensile properties could be found after being coated with PDA or PDA-REDV. The hydrophilicity of the hydrogels decreased with the coatings of PDA and especially PDA-REDV to improve protein adsorption, porcine iliac artery endothelial cells (PIECs) adhesion, viability, proliferation, and spreading on the hydrogels. Lower hemolysis percentages and higher blood clotting index values were attained for the hydrogels, suggesting their satisfactory hemocompatibility. Overall, the present work provided insights into the development of a novel hydrogel-based small-diameter vascular graft. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:117-127, 2020.

Biliary stent has been widely used in the treatment of biliary stricture and obstruction, it can relieve the pain of patients effectively, but bacterial infection and stent obstruction are still troublesome after surgery. We introduce the mechanism of infection and stent blockage caused by bacterial invasion after biliary stent implantation, and expound the formation mechanism of bacterial biofilm and bile sludge in this review. Antibacterial biliary stent is an effective way to inhibit biliary tract infection, the literatures on antibacterial modification of biliary stent with different antibacterial methods in domestic and abroad are reviewed, and the research prospect of antibacterial biliary stent is summarized and prospected.

An endothelial cell (EC) monolayer aligned along the direction of blood flow in vivo shows excellent capacity for anti-inflammation and anti-thrombosis. Therefore, aligned electrospun fibers have been much studied in the field of vascular implants since they are considered to facilitate the formation of an aligned EC monolayer, yet few research studies have been comprehensively reported concerning the effects of diameter scales of aligned fibers. In the present work, a series of aligned polycaprolactone (PCL) electrospun fibers with varying diameters ranging from dozens of nanometers to several micrometers were developed, and the effects of the fiber scales on EC behaviors, hemocompatibility as well as inflammatory cell behaviors were investigated, to evaluate their potential performance in the field of vascular implants. Our results showed that platelets exhibited small attachment forces on all fibers, and the anticoagulation property improved with the decrease of the fiber diameters. The impact of fiber diameters on human umbilical vein endothelial cell (HUVEC) adhesion and NO release was limited, while significant on HUVEC proliferation. With the increase of the fiber diameters, the elongation of HUVECs on our samples increased first then decreased, and exhibited maximum elongation degrees on 2738 nm and 2036 nm due to the strong contact guidance effect on these graphical cues; too thick or too fine fibers would weaken the contact guidance effect. Furthermore, we hypothesized that HUVECs cultured on 2036 nm had the smallest spreading area because of their elongation, but 2738 nm restricted HUVECs spreading limitedly. Similarly, NO production of HUVECs showed a similar change trend as their elongation degrees on different fibers. Except for 2036 nm, it exhibited the second highest NO production. For RAW 264.7 cells, poorer cell adhesion and lower TNF-α concentration of 1456 nm indicated its superior anti-inflammation property, while 73 nm showed a contrasting performance. Overall, these findings partly revealed the relationship between different topographies and cell behaviors, providing basic insight into vascular implant design.

Intimal hyperplasia, thrombosis formation, and delayed endothelium regeneration are the main causes that restrict the clinical applications of PTFE small-diameter vascular grafts (inner diameter < 6 mm). An ideal strategy to solve such problems is to facilitate in situ endothelialization. Since the natural vascular endothelium adheres onto the basement membrane, which is a specialized form of extracellular matrix (ECM) secreted by endothelial cells (ECs) and smooth muscle cells (SMCs), functionalizing PTFE with an ECM coating was proposed. However, besides ECs, the ECM-modified PTFE improved SMC growth as well, thereby increasing the risk of intimal hyperplasia. In the present study, heparin was immobilized on the ECM coating at different densities (4.89 ± 1.02 μg/cm(2), 7.24 ± 1.56 μg/cm(2), 15.63 ± 2.45 μg/cm(2), and 26.59 ± 3.48 μg/cm(2)), aiming to develop a bio-favorable environment that possessed excellent hemocompatibility and selectively inhibited SMC growth while promoting endothelialization. The results indicated that a low heparin density (4.89 ± 1.02 μg/cm(2)) was not enough to restrict platelet adhesion, whereas a high heparin density (26.59 ± 3.48 μg/cm(2)) resulted in decreased EC growth and enhanced SMC proliferation. Therefore, a heparin density at 7.24 ± 1.56 μg/cm(2) was the optimal level in terms of antithrombogenicity, endothelialization, and SMC inhibition. Collectively, this study proposed a heparin-immobilized ECM coating to modify PTFE, offering a promising means to functionalize biomaterials for developing small-diameter vascular grafts.

Background Thoracolumbar burst fractures (TBFs) are often followed by bilateral pedicle screw fixation (BPSF) at the level of fracture using posterior short-segment pedicle instrumentation (SSPI). There has been increasing support for unilateral pedicle screw fixation (UPSF) in an attempt to reduce complications and costs. The aim of this study was to compare the clinical and radiologic results of UPSF versus BPSF at the level of fracture using SSPI in the treatment of severe TBFs. Methods The records of 42 consecutive patients with severe TBFs who underwent SSPI were divided into 2 groups according to the number of screws in the fracture level, including 20 patients (five screws) in UPSF group and 22 patients (six screws) in BPSF. Different clinical and radiological parameters were recorded before surgery, after surgery, and 1.5 years after operation. The patients'clinical outcomes were assessed using visual analog scale (VAS), and Oswestry Disability Index (ODI). For radiological evaluation, changes in local kyphosis angle (LKA), vertebral wedge angle (VWA), and anterior vertebral height (AVH) were investigated using plain radiographs. Results Mean follow-up was 18.3 months for UPSF group and 19.0 months for BPSF group (P > 0.05). There were no significant differences in the age, gender, fracture type and site in both groups. Radiologically, no statistically difference was observed between the two groups in corrected rate of LKA, VWA, or AVH(all P > 0.05). With respect to clinical variants including VAS and ODI scores, there were also no significant differences. However, the UPSF group seemed to have advantages over BPSF group in operative time, blood loss, postoperative drainage, hospitalization time (P > 0.05). Especially, implant cost for the BPSF group was 22% greater than the UPSF group. No serious complications occurred in our study. In all cases, fusions healed well and no revision surgery was performed for loss of correction or failure of instrumentation during follow-up. Conclusions The present study is the first to demonstrate that patients undergoing SSPI with UPSF as compared with BPSF for the treatment of severe TBFs had similar clinical and radiologic outcomes.

Polyethylene glycol terephthalate (PET) fabrics with woven structures have proved to be quite effective for use on large diameter artificial blood vessels. However, their use within small-diameter artificial blood vessels has been associated with poor long-term patency, a problem resulting from slow endothelialization on PET and an over hyperplasia of smooth muscle cells. Previous research from our laboratory has revealed that ICAM-1 can be used as a marker to investigate cell adhesion, an effect which was closely associated with cell behavior on the surface of polycaprolactone (PCL) films. Moreover, we found that the coarseness or pore size of the surface exerts considerable influence on cell adhesion and proliferation on PCL films. In this study, we successfully fabricated six types of PET woven fabrics with varying gradients of tightness and porosities. Levels of ICAM-1 expression (membrane ICAM-1 & soluble ICAM-1) were then determined in these woven fabrics. Our results show that increased levels of mICAM-1 and decreased levels of sICAM-1 expression were obtained in HUVECs seeded on these six samples. These findings indicate that cell adhesion and proliferation on fabric surfaces were strongly influenced by their structural parameters, in particular the initial adhesion between the cell and fabric surface. In addition, we also found that extracellular matrix adhesion tends to prefer flat and tight surfaces, which promotes cell-cell and cell-matrix interactions, as well as the endothelialization on the surface of PET fabrics. These findings provide some novel insights with regard to the design and application of small-diameter artificial blood vessels. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 954-964, 2018.

Acute thrombosis remains the main limitation of small-diameter vascular grafts (inner diameter &lt, 6 mm) for bridging and bypassing of small arteries defects and occlusion. The use of hydrogel tubes represents a promising strategy. However, their low mechanical strength and high swelling tendency may limit their further application. In the present study, a hydrogel vascular graft of Ca alginate/polyacrylamide reinforced with a braided fiber strut was designed and fabricated with the assistance of a customized casting mold. Morphology, structure, swellability, mechanical properties, cyto- and hemocompatibility of the reinforced graft were characterized. The results showed that the reinforced graft was transparent and robust, with a smooth surface. Scanning electron microscopic examination confirmed a uniform porous structure throughout the hydrogel. The swelling of the reinforced grafts could be controlled to 100%, obtaining clinically satisfactory mechanical properties. In particular, the dynamic circumferential compliance reached (1.7 &plusmn, 0.1)%/100 mmHg for 50&ndash, 90 mmHg, a value significantly higher than that of expanded polytetrafluoroethylene (ePTFE) vascular grafts. Biological tests revealed that the reinforced graft was non-cytotoxic and had a low hemolysis percentage (HP) corresponding to (0.9 &plusmn, 0.2)%. In summary, the braided fiber-reinforced hydrogel vascular grafts demonstrated both physical and biological superiority, suggesting their suitability for vascular grafts.

Here, we investigate the relationship between the expression of intercellular adhesion molecule-1 (ICAM-1) and the adhesion of human umbilical vein endothelial cells (HUVECs) on a poly-e-caprolactone (PCL) film with micropores of different pore sizes. The results showed that surface hydrophilicity increased with larger pore sizes, while surfaces became less hydrophilic as the pore size decreased. The ability for adhesion and proliferation of HUVECs on surfaces with larger pore sizes was enhanced as compared with that of surfaces with smaller pore sizes or a flat film. Furthermore, levels of mICAM-1 were increased and sICAM-1 decreased as a function of increasing pore size. These findings demonstrate that film surfaces with larger pore sizes may promote cell adhesion and proliferation and lead to increases in expression of mICAM-1. Thus, we conclude that the pore size of the material's surface exerts a significant impact on the expression of adhesion molecules, the expression of which can represent an important new marker for investigating cell-surface adhesion and proliferation. Moreover, as elevated levels of sICAM-1 are associated with conditions such as inflammation, thrombosis, cerebral infarct and other diseases in vivo, it may serve as an early-warning risk marker when using medical biomaterials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2775-2784, 2016.

Stents have been widely used in percutaneous surgery to treat stenosis diseases. The braided NiTi stent, as a promising prototype, still has limitations of low radial force and loose structure. In the present study, a newly integrated composite stent was designed and braided with NiTi wires and polyester multifilament yarns by textile technology. The mechanical properties of four composite stents and the control bare NiTi stent were evaluated by in vitro compression, bending and anti-torsion tests. The results showed that integrated polyester/NiTi composite stents were superior in radial support. The stents could keep patency even when highly curved and had lower stent straightening force. Composite stents with certain structure stayed stable under twisting. The configuration of NiTi wires in composite stents could significantly impact stent deformation under twisting. Keywords: Vascular stent, Mechanical performance, Compression, Bending, Torsion

This study aimed to explore the neuroprotective effect of mesencephalic astrocyte-derived neurotrophic factor (MANF) protein on early brain injury caused by subarachnoid hemorrhage (SAH) and the relevant mechanisms in experimental rats, expecting to understand whether MANF was a potential therapeutic target for SAH treatment. A perforation model of SAH was introduced into the study. Recombinant human MANF (rh-MANF) and protein kinase B (Akt) inhibitor (MK2206) were used to explore the effect and the mechanisms. Multiple approaches for systemic assessment were employed in the research, including the Garcia test, the SAH grade, Evans blue (EB) dye leakage, brain-water content (BWC), the rotarod test, and the Morris water-navigation task, as were biotechniques, such as immunohistochemistry, Western blot, transmission electron microscopy, and flow cytometry. MANF was mainly expressed in rat neurons, and its expression increased significantly at 3 h after SAH induction and peaked at 24 h. Stereotactic injection of rh-MANF into the cerebroventricle significantly increased the level of MANF, p-Akt, p-mouse double minute 2 homolog (p-MDM2), and B-cell lymphoma 2 (Bcl-2) in brain tissue, whereas it down-regulated the expression of P53, Bcl-2-associated X protein (Bax), and cleaved caspase-3, which indicated that neuronal apoptosis was remarkably suppressed. Expression of matrix metallopeptidase 9 (MMP-9) was also suppressed by the rh-MANF injection. Furthermore, neurologic deficits, EB dye leakage, and BWC were reduced, and long-lasting neuroprotection was noted with rh-MANF administration. The antiapoptotic and blood-brain barrier (BBB) protective effect could be offset by administering MK2206. MANF could alleviate neuronal apoptosis by activating Akt-dependent prosurvival pathway and abate BBB damage via MMP-9 suppression. MANF showed not only transient but also long-lasting neuroprotective properties. The rh-MANF as a potential drug for treating SAH might be of clinical use.-Li, T., Xu, W., Gao, L., Guan, G., Zhang, Z., He, P., Xu, H., Fan, L., Yan, F., Chen, G. Mesencephalic astrocyte-derived neurotrophic factor affords neuroprotection to early brain injury induced by subarachnoid hemorrhage via activating Akt-dependent prosurvival pathway and defending blood-brain barrier integrity.

Endoleak and luminal loss related to blood permeation and microthrombus migration remain the main challenges in the aneurysm treatment, although stent-grafts have been widely applied. Stent-grafts provide a boundary to shield blood and microemboli transport, which are correlated with their mass transfer performance. Water permeability of vascular prostheses with woven and knitted structures has been analyzed and documented by many researchers, as well as oxygen and protein transfer. However, it is almost a total lack of blood and microemboli transfer along the braided stent-graft thickness direction. In this research, we provided a methodology for the vascular prostheses mass transfer evaluation. Braided stent-grafts in our former research were conducted on a self-developed testing system to investigate their blood permeability and microthrombus transfer behaviors. The pressure along wall thickness direction can be changed. Analytical models were also established based on pore parameters, making them applicative to different structures. Results revealed that the mass transfer behavior of stent-grafts was positively affected by porosity and pore diameter while negatively influenced by their thickness.

Sericin gum is like a two edged sword! It acts as the natural binder to maintain the structural integrity of silk filaments as well as to make the yarn more abrasion resistant. However, when used as an implantable device, for example, an arterial prosthesis, the presence of sericin increases the toxicity of the material. It is therefore necessary to remove all sericin before implantation. Although there are many methods to remove the sericin in the silk yarns or flat fabrics fabricated from silk yarns, there is little report about the method to degum silk in the tubular fabrics especially about small diameter (d≤6 mm) ones. In this study, small diameter arterial prostheses were woven using silk yarns still coated in sericin until the weaving process was completed. Then the samples were scoured to remove the sericin gum in sodium carbonate (0.05 wt. %) at 87 °C for 90 min with mechanical action. In order to make sure 90 min is enough to remove the sericin, the degumming time was extended to 210 min for some samples. Moreover, the degumming effect was examined on both inner and outer surfaces of the tubular samples to test the efficiency of the degumming method. The samples were first dyed with a picric acid-camine compound dye liquor which produces a red color with sericin and a yellow color with silk fibroin. After 90 min scouring, the samples showed a yellow color which indicates that the sericin had been removed completely by the degumming process. The effect of degumming was confirmed gravimetrically by measuring the weight loss, which was between 13.79 % and 23.99 % and remained steady after 90 min. Above all, the cytotoxicity was applied as one of the method to inspect the efficiency of degumming, which showed the result that, after degumming the samples were cytocompatible which is fit for implantation.

Cadherins are surface glycoproteins on plasma membranes and exist in many forms: T-cadherin, neuronal cadherin (N-cadherin), epithelial cadherin (E-cadherin), and vascular endothelial (VE-cadherin). Cadherins play critical roles in cell–cell interactions and are involved in multiple functions related to cell growth and proliferation. Findings from numerous reports have indicated that VE-cadherin regulates the remodeling, gating, and maturation of vascular vessels. The surface morphology of materials also impacts endothelial cell adhesion. This report is an overview of recent research on the effects of cadherins on cell–cell interactions, along with cell adhesions as examined on different materials. This summary will provide novel insights and approaches for research on cell–cell and cell–material interactions and illuminate some of the mechanisms of cell growth on different materials.

There is an urgent need to develop a biologically active implantable small-diameter vascular prosthesis with long-term patency. Silk-fibroin-based small-diameter vascular prosthesis is a promising candidate having higher patency rate; however, the surface modification is indeed required to improve its further hemocompatibility. In this study, silk fibroin fabric was modified by a two-stage process. First, the surface of silk fibroin fabric was coated using a layer-by-layer polyelectrolyte deposition technique by stepwise dipping the silk fibroin fabric into a solution of cationic poly(allylamine hydrochloride) (PAH) and anionic poly(acrylic acid) (PAA) solution. The dipping procedure was repeated to obtain the PAH/PAA multilayers deposited on the silk fibroin fabrics. Second, the polyelectrolyte-deposited silk fibroin fabrics were treated in EDC/NHS-activated low-molecular-weight heparin (LMWH) solution at 4 °C for 24 h, resulting in immobilization of LMWH on the silk fibroin fabrics surface. Scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray data revealed the accomplishment of LMWH immobilization on the polyelectrolyte-deposited silk fibroin fabric surface. The higher the number of PAH/PAA coating layers on the silk fibroin fabric, the more surface hydrophilicity could be obtained, resulting in a higher fetal bovine serum protein and platelets adhesion resistance properties when tested in vitro. In addition, compared with untreated sample, the surface-modified silk fibroin fabrics showed negligible loss of bursting strength and thus reveal the acceptability of polyelectrolytes deposition and heparin immobilization approach for silk-fibroin-based small-diameter vascular prostheses modification.

There are usually two forms of bone repair materials, block and granular, for common clinical use. This paper describes a novel injectable material, nano-HA/collagen/alginate (nHAC/Alg) composite biomaterial, including its preparation and evaluationsin vitro. Based on the idea of bionics and the study of collagen/calcium phosphate salt composite materials, the injectable bone repair material was developed. Then, human bone marrow stem cells (hBMSCs) were cultured on the nHAC/Alg material. The cell attachment, proliferation, and differentiation were evaluated with inverted microscope, scanning electron microscope, laser scanning confocal microscope, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) analysis, and alkaline phosphatase (ALP) test. The results showed that nHAC/Alg not only had no negative effect on cellular functions but also promotes cell proliferation and differentiation into osteogenic cells, which suggests that the nanoscaled injectable bone repair material has good clinical application prospects for bone repair.

Debridement describes the removal of necrotic tissue, cell debris and bacteria from a wound site. It aids the wound healing process and is considered as the cornerstone in proper wound management. The present work introduces a feasible approach to fabricate textile pile debridement materials with controllable structures. Six pile materials with variable pile densities and numbers of ground yarns were prepared based on the sliver knitting technology followed by back-coating, heat setting and shearing. Their surface morphology and chemistry were inspected by using SEM and FTIR. The mass per unit area and stitch density were measured to describe the basic geometric structures of the pile materials. The mechanical, liquid absorption and biological properties for the textile pile materials were assessed and compared with a commercial cotton gauze which is commonly used in clinical practice. The influence of structures on the mechanical, liquid absorption properties of the textile pile materials was also analyzed. Results show that pile density is the primary structure factor that affects the properties of the textile pile materials. Furthermore, all the six pile materials prepared in this study exhibited superior performance in both mechanical behaviors and liquid absorption capacity compared to the commercial gauze control. In addition, the results of biological evaluation indicate a satisfactory biocompatibility of the pile debridement material. Therefore the textile pile material offers a potential for wound debridement application.

Stent-grafts in peripheral arteries suffer from complex cyclic loadings in vivo, including pulsatile, axial bending and torsion. Normal fatigue durability evaluation technologies, however, are majorly based on pulsation and thus are short of accuracy under the complicated stress conditions experienced physiologically. While there is a little research focused on the cyclic fatigue of stent-grafts in bending, it remains an almost total lack of deformation or fatigue mechanisms. In this work, composite braided stent-grafts incorporating Nitinol (NiTi) yarns and polyethylene terephthalate (PET) multifilament yarns were cycled in bending by the self-developed testing system to investigate their deformation behaviors. Deformation mechanisms at the yarn level were discussed, and NiTi yarn crossover structure was considered the primary factor affecting the deformation modes. Four yarn-crossover-based deformation modes (accordion buckling, diamond-shaped buckling, neck propagation and microbuckling) revealed the mechanisms of energy absorption of braided stent-grafts on the mesoscopic scale. Further, mechanical modes were applied to help regulate stent designs.

The molecular mechanism underlying the fibrosis of ligamentum flavum(LF) in patients with lumbar spinal canal stenosis(LSCS) remains unknown. MicroRNAs are reported to play important roles in regulating fibrosis in different organs. The present study aimed to identify fibrosis related miR-21 expression profile and investigate the pathological process of miR-21 in the fibrosis of LF hypertrophy and associated regulatory mechanisms. 15 patients with LSCS underwent surgical treatment were enrolled in this study. For the control group, 11 patients with lumbar disc herniation(LDH) was included. The LF thickness was measured on MRI. LF samples were obtained during the surgery. Fibrosis score was assessed by Masson's trichrome staining. The expression of miR-21 in LF tissues were determined by RT-PCR. Correlation among LF thickness, fibrosis score, and miR-21 expression was analyzed. In addition, Lentiviral vectors for miR-21 mimic were constructed and transfected into LF cells to examine the role of miR-21 in LF fibrosis. Types I and III collagen were used as indicators of fibrosis. IL-6 expression in LF cells after transfection was investigated by RT-PCR and ELISA. Patients in two groups showed similar outcomes regarding age, gender, level of LF tissue. The thickness and fibrosis score of LF in the LSCS group were significantly greater than those in LDH group (all P 0.05). Similarly, the expression of miR-21 in LSCS group was substantially higher than that in LDH group(P 0.05). Furthermore, the miR-21 expression exhibited positive correlations with the LF thickness (r = 0.595, P 0.05) and fibrosis score (r = 0.608, P 0.05). Of note, miR-21 over-expression increased the expression levels of collagen I and III (P 0.05). Also, IL-6 expression and secretion in LF cells was elevated after transfection of miR-21 mimic. MiR-21 is a fibrosis-associated miRNA and promotes inflammation in LF tissue by activating IL-6 expression, leading to LF fibrosis and hypertrophy.

To enhance the hemocompatibility of silk fibroin fabric as biomedical material, polyelectrolytes architectures have been assembled through the layer-by-layer (LbL) technique on silk fibroin fabric (SFF). In particular, 1.5 and 2.5 bilayer of oppositely charged polyelectrolytes were assembled onto SFF using poly(allylamine hydrochloride) (PAH) as polycationic polymer and poly(acrylic acid) (PAA) as polyanionic polymer with PAH topmost. Low molecular weight heparin (LMWH) activated with 1-ethyl-3-(dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was then immobilized on its surface. Alcian Blue staining, toluidine blue assay and X-ray photoelectron spectroscopy (XPS) confirmed the presence of heparin on modified SFF surfaces. The surface morphology of the modified silk fibroin fabric surfaces was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and obtained increased roughness. Negligible hemolytic effect and a higher concentration of free hemoglobin by a kinetic clotting time test ensured the improved biological performance of the modified fibroin fabric. Overall, the deposition of 2.5 bilayer was found effective in terms of biological and surface properties of the modified fibroin fabric compared to 1.5 bilayer self-assembly technique. Therefore, this novel approach to surface modification may demonstrate long term patency in future in vivo animal trials of small diameter silk fibroin vascular grafts.

Since the bioresorption process has a strong impact not only on the mechanical properties of the biomaterial but also on the extent of tissue regeneration, in vivo biodegradation of absorbable porous biomaterials plays a key role in tissue repair and wound healing. In the present work, porous silk fibroin films (PSFFs) were prepared by a freeze-drying method and then implanted beneath the dorsal skin and the femoral skeletal muscle of the rat. The objective was to study the rate of biodegradation of the PSFFs in different tissues, each with its distinct metabolic rate. In addition we examined the relationship between the biodegradation rate and tissue-regeneration rate semi-quantitatively by incorporating histology, microscopy and image analysis methods. Furthermore, based on our previous findings, we also explored the relationship between in vitro and in vivo rates of biodegradation. The results suggest that the PSFFs experience a similar biodegradation process regardless of the type of tissue in which they are implanted, in spite of the higher metabolic rate of the skeletal muscle. In addition, the in vitro biodegradation rate of the PSFFs was comparable to that of both skin and skeletal muscle, suggesting that an in vitro biodegradation test could be used to predict in vivo performance.

Vascular basement membrane (VBM) is a thin layer of fibrous extracellular matrix linking endothelium, and collagen type IV (COL IV) is its main composition. VBM plays a crucial role in anchoring down the endothelium to its loose connective tissue underneath. For vascular grafts, constructing biomimetic VBMs on the luminal surface is thus an effective approach to improve endothelialization in situ. In the present work, three types of polycaprolactone (PCL) membranes were produced and characterized through cell counting kit-8 (CCK-8) assay, adhesion force and elastic modulus test to examine the influence of fiber diameter and membrane composition on vascular endothelial cell (EC) behaviors. The PCL membranes with finer fibers of 54.77 nm (PCL-54) could biomimic the nanotopography of VBMs more efficiently than 544.64 nm (PCL-544), and they were more suitable for Pig iliac endothelium cells (PIECs) adhesion and proliferation, meanwhile, inducing higher elastic modulus and adhesion force of PIECs. On this foundation, we further immobilized COL IV onto PCL-54 (PCL-COL IV) to biomimic VBMs compositionally. Results showed that PIECs on PCL-COL IV exhibited the highest viability and proliferation. Besides, quantitative data indicated that the elastic modulus of the PIECs on PCL-COL IV (4441.00 Pa) was as two times higher than that on PCL-54 (2312.26 Pa), and the adhesion force grew to 1120.99 pN from 673.58 pN of PIECs on PCL-54. In summary, the PCL-COL IV membranes show high similarity with the native VBMs in terms of structure and composition, suggesting a promising potential for surface modification to vascular grafts for improved endothelialization.

The development of a small diameter (≤5 mm) arterial prosthesis requires the appropriate selection of materials, structure and fabrication method so as to provide adequate mechanical properties, superior biocompatibility and precise control over the diameter. In this study, 100% polyester, 100% silk fibroin and a combination of both yarns were woven into seamless tubular prototype prostheses with different basic weaves. After degumming/scouring they met a target inner diameter of 3.9±0.3 mm which demonstrates that weaving is a precise way to manufacture small caliber arterial prostheses. In conclusion, the bicomponent polyester/silk woven samples had superior mechanical properties and improved cytocompatibility compared to commercial ePTFE devices.

The repair of the damaged bone tissue caused by damage or bone disease was still a problem. Current strategies including the use of autografts and allografts have the disadvantages, namely, diseases transmission, tissue availability and donor morbidity. Bone tissue engineering has been developed and regarded as a new way of regenerating bone tissues to repair or substitute damaged or diseased ones. The main limitation in engineering in vitro tissues is the lack of a sufficient blood vessel system, the vascularization. In this paper, a new-typed hydroxyapatite/collagen composite scaffold which was reinforced by chitosan fibers and cultured with osteoblasts and endothelial cells was fabricated. General observation, histological observation, detection of the degree of vascularization, and X-ray examination had been done to learn the effect of vascularized bone repair materials on the regeneration of bone. The results show that new vessel and bone formed using implant cultured with osteoblasts and endothelial cells. Nanofiber-reinforced scaffold cultured with osteoblasts and endothelial cells can induce vascularized bone tissue formation.

Background A review of the literature showed that posterior short-segment fixation including the fractured vertebra (PSFFV) has better outcomes in the treatment of thoracolumbar burst fractures(TBFs) than patients with short-segment pedicle screw fixation(SSPF) alone. However, its efficacy in mild TBFs with load-sharing scores of 3 and 4 points has not been specifically analyzed. The aim of this study was to compare the clinical, functional and radiologic results of PSFFV with SSPF for mild TBFs and to determine whether the screws in the fractured vetebra were necessary for these patients. Methods In this retrospective study, sixty-nine patients with mild TBFs were divided into 2 groups according to the number of instrumented levels. Group A included 34 patients treated by SSPF (four screws:one level above and below the fracture), and Group B included 35 patients treated by PSFFV (six screws: including the fractured vertebra). Clinical and radiologic parameters were evaluated before surgery, after surgery, and at follow-up. They included clinical outcomes: visual analog scale (VAS), Oswestry Disability Index (ODI). Being a radiology-based study, the radiologic measures included vertebral wedge angle (VWA), and anterior vertebral height (AVH). Results A sum of 69 patients (34 patients in Group A and 35 patients in Group B) were enrolled in the study. The patients in both the groups showed similar outcomes with regards to age, gender, fracture type and site. We did not find any statistically difference between the two groups in corrected rate of VWA or AVH (P > 0.05). In terms of clinical variants such as VAS and ODI scores, there were also no significant differences. However, the SSPF had advantages over PSFFV method in operative time, blood loss, postoperative drainage and postoperative hospitalization time (P > 0.05). There were no serious complications occurring during our study, such as infection, blood vessel injury, spinal cord or nerve root injury. No patient needed revision for loss of correction or failure of instrumentation. Conclusions SSPF alone is a safe and effective surgical method for restoration and maintenance of vertebral column stability in treating mild TBFs. It gives excellent clinical and radiological results regardless of whether the fractured vertebra is included in the fixation or not.

Here, we investigate the relationship between the expression of intercellular adhesion molecule-1 (ICAM-1) and the adhesion of human umbilical vein endothelial cells (HUVECs) on a poly-ε-caprolactone (PCL) film with micropores of different pore sizes. The results showed that surface hydrophilicity increased with larger pore sizes, while surfaces became less hydrophilic as the pore size decreased. The ability for adhesion and proliferation of HUVECs on surfaces with larger pore sizes was enhanced as compared with that of surfaces with smaller pore sizes or a flat film. Furthermore, levels of mICAM-1 were increased and sICAM-1 decreased as a function of increasing pore size. These findings demonstrate that film surfaces with larger pore sizes may promote cell adhesion and proliferation and lead to increases in expression of mICAM-1. Thus, we conclude that the pore size of the material's surface exerts a significant impact on the expression of adhesion molecules, the expression of which can represent an important new marker for investigating cell-surface adhesion and proliferation. Moreover, as elevated levels of sICAM-1 are associated with conditions such as inflammation, thrombosis, cerebral infarct and other diseases in vivo, it may serve as an early-warning risk marker when using medical biomaterials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2775-2784, 2016.

In this study, the porous silk fibroin film (PSFF) is implanted into the body of a rat. Ten days later, the growing state of the capillaries in the material was observed, and the growing law of the capillaries in porous material is discussed to better understand the growing state of the peripheral tissue and cells around the material. The fact that the PSFF creates a beneficial environment for the growth of the capillaries in the tissue is confirmed, and the good growing states of the new skeleton muscle and the hypodermal tissue are also observed. This provides basic experimental results for the design of the PSFFs, which is a new medical biomaterial.

In order to obtain porous silk fibroin films (PSFFs) fit for the repair of different tissues and organs and design the configuration of the PSFFs more rationally, a model of the oxygen diffusing system of the capillary was built, and also the equations of the model were solved. Moreover, the relationships between the distribution of the oxygen concentration and each affecting factors were discussed, a method was developed to estimate the density of the capillaries in the tissue, and hereby discussed the characteristics of the oxygen diffusion in the tissues around the open capillaries.

Background In this study, we fabricated prototype bicomponent polyester/silk fibroin small-diameter arterial prostheses using a specially designed narrow ribbon shuttle loom. Methods The 2-layered flat fabrics were then heatset on a mandrel to form tubes with a round cross section. Results The woven samples had a wall thickness between 0.23 mm and 0.29 mm and an inner diameter between 3.53 mm and 3.95 mm, depending on the yarn type and the weave structure. Conclusions The bicomponent polyester/silk fibroin samples had superior bursting strength, circumferential strength and suture retention strength compared with a commercial small-diameter arterial prosthesis made from ePTFE. In addition, these prototype samples had greater suture retention strengths than a dog femoral artery, which indicates that they have adequate biostability for clinical use. While their amount of radial compliance was superior to that of the ePTFE commercial graft control, it did not match that of a natural artery. So there is still a need for future improvement in compliance. All of the woven prototypes had water permeability values between 26 and 180 ml/(cm2*min), which confirms that none of these arterial prostheses needs to be preclotted at the time of implantation. The biocompatibility of the woven prototypes was evaluated using porcine endothelial cells and an MTT assay. Their cytocompatibility was found to be superior to the ePTFE commercial control, and the level of cell attachment was observed to increase on these prototypes woven with a higher silk fibroin content.