Release Of Heparin Research Articles

Fabrication of pH-sensitive magnetic metal-organic framework for controlled-release of heparin

Heparin, the most widely used anticoagulant drug in the world today, suffers from the risk of overdose and a short serum half-life, limiting its clinical applications. Concerning the controlled, sustained, and targeted release of heparin, a delivery system was fabricated in this research using the layered composites of Fe3O4 magnetic particles and pH-sensitive metal-organic framework, Fe3O4@ZIF-8. The composite demonstrated a high loading capacity for the heparin, 66.8 mg/g. The composite had a saturation magnetization of 1.5 emu/g and thus owned a magnetic targeting function, i.e. drug can be centered at a certain point using an external magnetic field. The anticoagulant activity was assessed by monitoring their activated partial thromboplastin time. The results showed that the pH-responsive and sustained release of the heparin reduced the systemic adverse effects associated with high concentrations. Moreover, control over the dose exhibited excellent anticoagulant features with fewer side effects.

Dual surface modification of poly(L-lactide) scaffold achieved by thermal incorporation of aligned nanofiber and click immobilization of VEGF to enhance endothelialization and blood compatibility

Rapid endothelialization is very important in the development of blood-contact biomaterials because of the inhibitory effects of endothelium in preventing thrombosis and restenosis. In this study, topographical and biochemical cues were generated to accelerate endothelialization on the poly(L-lactide) (PLLA) scaffold via a simple, bio-orthogonal, and biocompatible process. Topographical guidance was incorporated into a PLLA scaffold via thermal attachment of aligned PLLA nanofibers using electrospinning. Vascular endothelial growth factor (VEGF) was covalently immobilized onto the PLLA scaffold by aminolysis and copper-catalyzed azide/alkyne cycloaddition-mediated click chemistry. Various surface analyses confirmed the presence of aligned topography and immobilized VEGF without delamination or leaching. In vitro experiments with human coronary artery endothelial cells revealed that proliferation, CD31 expression, and migration was significantly enhanced on the nanofiber-attached VEGF-immobilized PLLA scaffold. The aligned nanofiber also accommodated the sustained release of heparin, which suppressed the proliferation of human coronary artery smooth muscle cells and platelet activation without affecting surface endothelialization. The heparin-loaded, aligned, nanofiber-attached VEGF-immobilized PLLA scaffold was evidenced to be biocompatible and a promising candidate for blood-contact materials where fast endothelialization and suppressed platelet activation is required.

Hierarchical Shish-Kebab Structures Functionalizing Nanofibers for Controlled Drug Release and Improved Antithrombogenicity.

The functionalization of the fibrous scaffolds including drug loading and release is of significance in tissue engineering and regenerative medicine. Our previous results have shown that the shish-kebab structure-modified fibrous scaffold shows a completely different microenvironment that mimics the topography of the collagen fibers, which interestingly facilitates the cell adhesion and migration. However, the functionalization of the unique structure needs to be further investigated. In this study, we modified the heparin-loaded fiber with a shish-kebab structure and tuned the kebab structure as the barrier for the sustained release of heparin. The introduction of the kebab structure increases the diffusion energy barrier by extending the diffusion distance. Moreover, the discontinued surface topography of the shish-kebab structure altered the surface chemistry from hydrophobic for the original poly(ε-caprolactone) (PCL) nanofibers to hydrophilic for the PCL nanofibers with the shish-kebab structure, which might have inhibited the activation of fibrinogen and thus improved the anticoagulant ability. This synergistic effect of heparin and the kebab structure significantly promotes the endothelial cell affinity and antithrombogenicity. This method might be a viable and versatile drug delivery strategy in vascular tissue engineering.

OPTIMIZATION OF DIAGNOSIS OF SECONDARY METABOLIC DISORDERS AND TREATMENT TACTICS IN PATIENTS WITH ANEMIA IN NEOPLASTIC DISEASE IN COLORECTAL CANCER

Colorectal cancer is one of the most common oncological diseases, therefore, the study of this problem is an important issue in clinical practice. This problem becomes especially urgent in case of the formation of anemic syndrome in patients, which causes the emergence of a mutual burden syndrome and increases the risks for a patient. The progressive nature of anemia in colorectal cancer is accompanied by secondary metabolic disorders. The material for the study was the blood plasma of 445 patients (228 men and 217 women). Among them, 53 patients (31 women and 22 men) with iron deficiency anemia were examined and included in the first observation group (І) and 392 patients (206 men (52,55 %) and 186 women (47.45 %)) with colorectal cancer whose course of the underlying disease was burdened with anemia in neoplastic disease were included in the second observation group (II). Among the patients in the second (II) observation group, there were 222 individuals (119 men and 103 women) with malignant neoplasms of the colon (ICD-10 code: С.18), 29 individuals (16 men and 13 women) with malignant neoplasms of the rectosigmoid junction (ICD-10 code: C.19), 138 individuals (82 men and 56 women) with malignant neoplasms of the rectum (code ICD-10 C.20) and 3 patients (2 men and 1 woman) with malignant neoplasms of the anus (ICD-10 code: C.21). The age of the examined patients was from 22 to 79 years. It was found that prior to the initiation of treatment in patients with anemia in neoplastic disease, regardless of the course of colorectal cancer, there was a significant increase in the plasma level of free fractions of heparin, histamine and serotonin (p < 0,001); the ratio of histamine: serotonin was also changed in comparison with the values in the control group (p < 0,05), which indicated both an increased release of heparin, histamine and serotonin from the depot, and an impaired inactivation processes of these biologically active substances. It was correctly concluded that in addition to the baseline therapy the administration of arginine glutamate which causes both antihypoxic and membrane-stabilizing action, reliably contributes to the normalization of secondary metabolic disorders of histamine, serotonin and heparin metabolism in anemia in neoplastic disease in patients with colorectal cancer.

Investigation of heparin-loaded poly(ethylene glycol)-based hydrogels as anti-thrombogenic surface coatings for extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO), a critical life-sustaining tool, faces significant challenges for the maintenance of normal haemostasis due to the large volume of circulating blood continuously in contact with artificial surfaces, hyperoxia and excessive shear stresses of the extracorporeal circuit. From a biomaterials perspective, it has been hypothesised that drug eluting coatings composed of haemocompatible hydrogels loaded with an anticoagulant drug could potentially enhance the haemocompatibility of the circuit. Poly(ethylene glycol) (PEG) has been well established as a biocompatible and anti-fouling material with wide biomedical application. Unfractionated heparin is the most commonly used anticoagulant for ECMO. In the present study, the feasibility of using heparin-loaded PEG-based hydrogels as anti-thrombogenic surface coatings for ECMO was investigated. The hydrogels were synthesised by photopolymerisation using poly(ethylene glycol) diacrylate (PEGDA) as the crosslinking monomer and poly(ethylene glycol) methacrylate (PEGMA) as the hydrophilic monomer, with heparin loaded into the pre-gel solution. Factors which could affect the release of heparin were investigated, including the ratio of PEGDA/PEGMA, water content, loading level of heparin and the flow of fluid past the hydrogel. Our results showed that increased crosslinker content and decreased water content led to slower heparin release. The hydrogels with water contents of 60 wt% and 70 wt% could achieve a sustained heparin release by adjusting the ratio of PEGDA/PEGMA. The anticoagulation efficacy of the released heparin was evaluated by measuring the activated clotting time of whole blood. The hydrogels with desirable heparin release profiles were prepared onto poly(4-methyl-1-pentene) (PMP) films with the same chemical composition as the PMP ECMO membranes. The coatings showed sustained heparin release with a cumulative release of 70-80% after 7 days. Haemocompatibility tests demonstrated that PEG hydrogel coatings significantly reduced platelet adhesion and prolonged plasma recalcification time. These results suggest that heparin-loaded PEG hydrogels are potential anti-thrombogenic coatings for ECMO.

Regional anticoagulation magnetic artificial blood vessels constructed by heparin-PLCL core-shell nanofibers for rapid deployment of veno-venous bypass.

Veno-venous bypass (VVB) is necessary for maintaining hemodynamic and internal environment stabilities in complex liver surgeries. However, the current VVB strategies require systematic anticoagulation and are time-consuming, leading to unexpected complications. This study aims to overcome these limitations by using a novel magnetic artificial blood vessel constructed with heparin-PLCL core-shell nanofibers. Coaxial electrospinning was used to fabricate core-shell nanofibers with heparin encapsulated into the core layer. The microstructure, physical and chemical properties, hemocompatibility, and heparin release behavior were characterized. The regional anticoagulation magnetic artificial vessel was constructed with these nanofibers and used to perform VVB in a rat liver transplantation model for in vivo evaluation. The core-shell nanofibers appeared smooth and uniform without apparent defects. Fluorescence and TEM images indicated that heparin was successfully encapsulated into the core layer. In addition, the in vitro heparin release test presented a two-phase release profile, burst release at day 1 and sustained release from days 2 to 14, which resulted in better hemocompatibility. The VVB could be rapidly deployed in 3.65 ± 0.83 min by the magnetic artificial vessel without systemic anticoagulation. Moreover, the novel device could reduce portal pressure and abdominal organ congestion, protect intestinal function, and increase the survival rate of liver transplantation with a long anhepatic phase from 0 to 65%. In summary, VVB can be rapidly deployed using regional anticoagulation magnetic artificial blood vessels without systemic anticoagulation, which is promising for improving patient outcomes after complex liver surgery.

Using artificial neural network for design and development of PVA/chitosan/starch/heparinized nZnO hydrogels for enhanced wound healing

A study of many individual parameters is required to provide a robust investigation of a system in biomedical applications. A comprehensive understanding of these parameters is achievable by an appropriate experimental model as a valid description to predict the outputs (responses). A combination of response surface methodology and artificial neural network has been employed to design hydrogel dressings including polyvinyl alcohol, chitosan, and starch. The optimal ratio of components of hydrogels as input data based on the water vapor transmission rate, gel content, swelling ratio, and porosity properties as output parameters was determined using the quick propagation algorithm. Zinc-oxide nanoparticles were coupled with heparin and applied in the optimal formulation to investigate its effect on physical and mechanical properties, cytotoxicity, and antibacterial activities as well as in vivo wound healing. Mechanical strength improved in the presence of zinc-oxide nanoparticles. Heparin release reached with the saturation state in a longer period after conjugation onto zinc-oxide nanoparticles. Minimum inhibitory concentration decreased significantly by conjugation of heparin to the nanoparticles and current systems could protect wounds against infections. In vivo wound healing and immunohistochemistry assay indicated accelerated wound closure, re-epithelialization, and skin regeneration for hydrogel dressings containing heparin functionalized zinc-oxide nanoparticles.

Bioactive 3D Scaffolds for the Delivery of NGF and BDNF to Improve Nerve Regeneration

Peripheral nerve injury is an important cause of disability, that can hinder significantly sensory and motor function. The clinical gold standard for peripheral nerve repair is the use of autografts, nevertheless, this method has limitations such as donor site morbidity. An emerging alternative to autografts are nerve guide conduits, which are used to entubulate the severed nerve and provide guidance for the directed regeneration of the nerve tissue. These nerve guide conduits are less effective than autografts, and to enhance their performance the incorporation of neurotrophins can be considered. To enable optimal nerve regeneration, it is important to continuously stimulate neurite outgrowth by designing a delivery system for the sustained delivery of neurotrophins. The aim of this study was to develop a novel bioactive surface on electrospun fibres to supply a sustained release of heparin bound NGF or BDNF electrostatically immobilised onto an amine functionalized surface to encourage neurite outgrowth and Schwann cell migration. The bioactive surface was characterised by XPS analysis and ELISA. To assess the effect of the bioactive surface on electrospun fibres, primary chick embryo dorsal root ganglia were used, and neurite outgrowth and Schwann cell migration were measured. Our results showed a significant improvement regarding nerve regeneration, with the growth of neurites of up to 3 mm in 7 days, accompanied by Schwann cells. We hypothesize that the physical guidance provided by the fibres along the sustained delivery of NGF or BDNF created a stimulatory environment for nerve regeneration. Our results were achieved by immobilising relatively low concentrations of neurotrophins (1 ng/ml), which provides a promising, low-cost, and scalable method to improve current nerve guide conduits.

Оптимізація діагностики вторинних метаболічних порушень та лікувальної тактики у пацієнтів із анемією злоякісного новоутворення при колоректальному раку

The purpose of the study was to study the content of free fraction of heparin, histamine and serotonin in plasma of peripheral venous blood of patients with malignant neoplasm anemia in colorectal cancer, depending on the severity of anemia. Materials and methods. The material for the study was the blood plasma of 445 patients (228 men and 217 women). Among them, 53 patients (31 women and 22 men) with iron deficiency anemia were examined and included in the first observation group (І) and 392 patients (206 men (52.55 %) and 186 women (47.45 %)) with colorectal cancer whose course of the underlying disease was burdened with malignant neoplasm anemia (ICD-10 code: D63.0) were included in the second observation group (II). Among the patients in the second (II) observation group, there were 222 individuals (119 men and 103 women) with malignant neoplasms of the colon (ICD-10 code: С.18), 29 individuals (16 men and 13 women) with malignant neoplasms of the rectosigmoid junction (ICD-10 code: C.19), 138 individuals (82 men and 56 women) with malignant neoplasms of the rectum (code ICD-10 C.20) and 3 patients (2 men and 1 woman) with malignant neoplasms of the anus (ICD-10 code: C.21). The mean age of the patients was 63.3 ± 1.2 years old. The plasma level of free fraction of heparin of the examined patients was determined using the photocolorimetric method on photoelectric colorimeter 56-M after its preliminary isolation by electrophoretic method according to the appropriate procedure (B. V. Mykhailychenko, S. V. Vydyborets (2000)). The plasma level of free histamine and serotonin of the examined patients was studied using the method of fluorometric analysis on the analyzer “BIAN-130”-“BIAN-100” according to the procedure of B. V. Mykhailychenko, S. V. Vydyborets (1999). Results and discussion. It was found that prior to the initiation of treatment in patients with malignant neoplasm anemia, regardless of the course of colorectal cancer, there was a significant increase in the plasma level of free fraction of heparin, histamine, serotonin (p < 0.001); the ratio of free histamine to free serotonin was also changed in comparison with the values in the control group (p < 0.05), which indicated both an increased release of heparin, histamine and serotonin from the depot, and an impaired inactivation processes of these biologically active substances. Considering all of the above and the quite obvious reasons, namely, the secondary metabolic disorders of serotonin, histamine, heparin which manifested by a significant increase in their plasma level of patients with malignant neoplasm anemia in colorectal cancer, we suggested the need to use a medicinal product in a complex of therapeutic measures which can cause antihypoxic, membrane stabilizing and anti-edema action. Conclusion. Malignant neoplasm anemia in colorectal cancer is accompanied by significant changes in the metabolism of biologically active substances – free fraction of heparin, histamine, serotonin, and the ratio of free histamine to serotonin. It was correctly concluded that in addition to the baseline therapy the administration of arginine glutamate which causes both antihypoxic and membrane-stabilizing action, reliably contributes to the normalization of secondary metabolic disorders of histamine, serotonin and heparin metabolism in malignant neoplasm anemia in patients with colorectal cancer

Long-Term Sustained Drug Delivery via 3D Printed Masks for the Development of a Heparin-Loaded Interlayer in Vascular Tissue Engineering Applications.

Current approaches in small-diameter vascular grafts for coronary artery bypass surgeries fail to address physiological variations along the graft that contribute to thrombus formation and ultimately graft failure. We present an innovative interlayer drug delivery system that can be utilized for the sustained delivery of heparin through a graft with a high degree of temporal and spatial control. A heparin-loaded gelatin methacrylate (gelMA) interlayer sits within a biohybrid composed of decellularized bovine pericardium (dECM) and poly(propylene fumarate) (PPF), and its UV crosslinking is controlled via three-dimensional (3D) printed shadow masks. The masks can be readily designed to modulate the incident light intensity on the graft, enabling us to control the resultant gelMA crosslinking and properties. A high heparin loading efficiency was obtained in gelMA and was independent of crosslinking. We achieved sustained heparin release over the course of 2 weeks within the biohybrid material using the 3D printed mask patterns. High doses of heparin were observed to have detrimental effects on endothelial cell function. However, when exposed to heparin in a slower, more sustained manner consistent with the masks, endothelial cells behave similarly to untreated cells. Further, slower release profiles cause significantly more release of tissue factor pathway inhibitor, an anticoagulant, than a faster release profile. The heparin-loaded gelMA interlayer we have developed is a useful tool for the temporal and spatial control of heparin release that supports endothelial function and promotes an antithrombotic environment.

4D Printing of Self-Folding Hydrogel Tubes for Potential Tissue Engineering Applications

In recent years, 4D printing has gained increasing attention in the tissue engineering field since this advanced manufacturing platform can create stimulus-responsive structures, which can change their shapes, functions, and/or properties when appropriate external stimulus/stimuli is/are applied. A number of hydrogels with swellable/shrinkable abilities have been explored for 4D printing to fabricate different shape-morphing structures for tissue engineering. Among them, gelatin methacryloyl (GelMA) has been 4D printed, which can self-fold into microtubular structures. Currently, the self-folding ability of 4D printed GelMA hydrogels is mainly based on the different cross-linking degrees (which control and govern the swelling degrees) across the thickness of hydrogels. However, this strategy alone can only form self-folding GelMA tubes with diameters at the micrometer level and cannot create self-folding GelMA tubes with diameters at the millimeter level, which is mainly due to the insufficient internal force generated in 4D printed GelMA hydrogels when they are exposed to water. To overcome this limitation, this study has investigated a new strategy to fabricate self-folding GelMA tubes with large diameters at the millimeter level for tissue engineering applications. The new strategy introduced a cross-linking degree gradient across the GelMA plane in addition to its thickness by printing a second layer of strips on the first 4D printed GelMA film. In the aqueous environment, under the current fabrication condition, such bilayer GelMA hydrogels could self-fold into tubes of larger diameters up to 6[Formula: see text]mm. The in vitro release behavior of heparin incorporated into the 4D printed GelMA was also studied. It was shown that heparin release could be controlled by the GelMA concentration and heparin content in 4D printed GelMA. The 4D printed GelMA hydrogels with the improved self-folding ability and controlled release of a drug are promising for targeted tissue engineering applications.

Evaluation of angiogenic potential of heparin and thyroxine releasing wound dressings

In the present research, heparin (1 μg/ml, 5 μg/ml) and thyroxine (1 μg/ml, 5 μg/ml) loaded wound dressings were prepared. Ultrastructure of the developed scaffolds revealed by scanning electron microscope and fourier transform infrared spectroscopy proved them an attractive choice for skin tissue engineering. Drug release kinetics showed maximum release (95%) of thyroxine by day 3 compared to the heparin having sustained release until the endpoint of the assay. The angiogenic abilities of synthesized materials were evaluated through chorioallantoic membrane (CAM) assay. Our findings demonstrate that the developed scaffolds are the promising choice for wound healing applications especially with regards to their angiogenic properties.

Tight Binding of Plasmid DNA With Self-Assembled Tetramethylguanidinium Conjugated Polyethylenimine Suppresses Transfection Efficiency

Here, we have demonstrated that on modification of linear polyethylenimine (lPEI, LP) with amphiphilic 3-bromopropyltetramethylguanidinium (PTMG) linker, the transfection efficiency exhibited by the modified polymers decreased while cell viability improved. A series of LP-PTMG polymers was synthesized by the reaction of varying amounts of 3-bromopropyl tetramethylguanidinium linker with lPEI (25 kDa). These modified polymers interacted efficiently with pDNA and formed nanosized complexes as shown by dynamic light scattering analysis. The size of the complexes in the series LP-PTMG/pDNA was observed in the range of ∼178–205 nm. The interaction of modified polymers with plasmid DNA was stronger than linear PEI as evidenced by heparin release assay which showed ∼83% pDNA release from LP-PTMG-3/pDNA complexes in comparison to ∼95% in lPEI/pDNA complexes on treatment with same amount of heparin suggesting the formation of self-assembled structures in modified polymers. The transfection studies in HeLa and Chinese hamster ovary cells showed a decrease in transfection efficiency of LP-PTMG polymers, the reason for this may be strong binding of modified polymers with pDNA due to accumulation of charge on the surface. This finding showed the significance of optimum binding of polymer and DNA to form polyplexes as well as release of DNA from the polyplexes.

Heparin-Eluting Tissue-Engineered Bioabsorbable Vascular Grafts

The creation of small-diameter tissue-engineered vascular grafts using biodegradable materials has the potential to change the quality of cardiovascular surgery in the future. The implantation of these tissue-engineered arterial grafts has yet to reach clinical application. One of the reasons for this is thrombus occlusion of the graft in the acute phase. In this paper, we first describe the causes of accelerated thrombus formation and discuss the drugs that are thought to inhibit thrombus formation. We then review the latest research on methods to locally bind the anticoagulant heparin to biodegradable materials and methods to extend the duration of sustained heparin release. We also discuss the results of studies using large animal models and the challenges that need to be overcome for future clinical applications.

Physical Properties of Electropolished CoCrMo Alloy Coated with Biodegradable Polymeric Coatings Releasing Heparin after Prolonged Exposure to Artificial Urine.

In this study, we aimed to determine the effect of long-term exposure to artificial urine on the physical properties of CoCrMo alloy with biodegradable heparin-releasing polymeric coatings. Variants of polymer coatings of poly(L,L-lactide-ɛ-caprolactone) (P(L,L-L/CL)) and poly(D,L-lactide-ɛ-caprolactone) (P(D,L-L/CL)) constituting the base for heparin-releasing (HEP) polyvinyl alcohol (PVA) coatings were analyzed. The coatings were applied by the dip-coating method. Heparin was used to counteract the incrustation process in the artificial urine. The study included tests of wettability, resistance to pitting and crevice corrosion, determination of the mass density of metal ions penetrating into the artificial urine, and the kinetics of heparin release. In addition, microscopic observations of surface roughness and adhesion to the metal substrate were performed. Electrolytically polished CoCrMo samples (as a reference level) and samples with polymer coatings were used for the tests. The tests were conducted on samples in the initial state and after 30, 60, and 90 days of exposure to artificial urine. The analysis of the test results shows that the polymer coatings contribute by improving the resistance of the metal substrate to pitting and crevice corrosion in the initial state and reducing (as compared with the metal substrate) the mass density of metal ion release into the artificial urine. Moreover, the PVA + HEP coating, regardless of the base polymer coatings used, contributes to a reduction in the incrustation process in the first 30 days of exposure to the artificial urine.

Amphiphilic Core Cross-Linked Star Polymers for the Delivery of Hydrophilic Drugs from Hydrophobic Matrices.

The delivery of hydrophilic drugs from hydrophobic polymers is a long-standing challenge in the biomaterials field due to the limited solubility of the therapeutic agent within the polymer matrix. In this work, we develop a drug delivery mechanism that enables the impregnation and subsequent elution of hydrophilic drugs from a hydrophobic polymer material. This was achieved by synthesizing core cross-linked star polymer amphiphiles with hydrophilic cores and hydrophobic coronas. While significant work has been done to create nanocarriers for hydrophilic drugs, this work is distinct from previous work in that it designs amphiphilic and core cross-linked particles for controlled release from hydrophobic matrices. Ultraviolet-mediated atom transfer radical polymerization was used to synthesize the poly(ethylene glycol) (PEG)-based hydrophilic cores of the star polymers, and hydrophobic coronas of poly(caprolactone) (PCL) were then built onto the stars using ring-opening polymerization. We illustrated the cytocompatibility of PCL loaded with these star polymers through human endothelial cell adhesion and proliferation for up to 7 days, with star loadings of up to 40 wt %. We demonstrated successful loading of the hydrophilic drug heparin into the star polymer core, achieving a loading efficiency and content of 50 and 5%, respectively. Finally, the heparin-loaded star polymers were incorporated into a PCL matrix and sustained release of heparin was illustrated for over 40 days. These results support the use of core cross-linked star polymer amphiphiles for the delivery of hydrophilic drugs from hydrophobic polymer matrices. These materials were developed for application as drug-eluting and biodegradable coronary artery stents, but this flexible drug delivery platform could have impact in a broad range of medical applications.

Bladder muscle regeneration enhanced by sustainable delivery of heparin from bilayer scaffolds carrying stem cells in a rat bladder partial cystectomy model

In bladder tissue engineering, regeneration of muscle is of equal importance to epithelial regeneration. However, as yet there is no effective strategy for promoting bladder muscle regeneration. In this study we aim to promote bladder muscle regeneration by sustainably delivering heparin from a bilayer scaffold carrying stem cells. The bilayer scaffold [heparin–polycaprolactone (PCL)/bladder decellularized matrix (BAM) Hep-PB/PCL] comprises an electrospun layer (Hep-PB electrospun membrane) and a three-dimensional (3D) printed layer (PCL scaffold), fabricated via coaxial-electrospinning and 3D printing, respectively. Heparin was encapsulated into the core of the Hep-PB fibers with a core–shell structure to sustain its release. The morphology of the bilayer scaffold and the microstructure of the electrospun fibers were characterized. The release behavior of heparin from various electrospun membranes was evaluated. The role of Hep-PB in promoting myogenic differentiation of the adipose-derived stem cells (ADSCs) through sustainable release of heparin was also evaluated. After 7 d culture, Hep-PB/PCL scaffolds carrying ADSCs (defined as ASHP) were used for bladder reconstruction in a rat partial cystotomy model. The result shows that the PCL printed scaffold has ordered macropores (∼370 μm), unlike the compact microstructure of electrospun films. The Hep-PB membrane exhibits a sustained release behavior for heparin. This membrane also shows better growth and proliferation of ADSCs than the other membranes. The polymerase chain reaction results show that the expression of smooth muscle cell markers in ADSCs is enhanced by the Hep-PB scaffold. The results of retrograde urethrography and histological staining indicate that the bladder volume in the ASHP group recovers better, and the regenerated bladder muscle bundles are arranged in a more orderly fashion compared with the direct suture and bladder decellularized matrix groups. Therefore, findings from this study show that bladder muscle regeneration could be enhanced by bilayer scaffolds delivering heparin and carrying stem cells, which may provide a new strategy for bladder tissue engineering.

Effect of heparinization on promoting angiogenesis of decellularized kidney scaffolds.

Native decellularized extracellular matrix provides an adequate platform for tissues and organs and promotes the development of organogenesis and tissue remodeling. However, thrombosis poses a great challenge that hinders the transplantation for a substantial organ in vivo. Therefore, anticoagulation and re-reendothelialization of organ biological scaffolds are the primary concerns to be addressed before orthotopic transplantation. Herein, a heparinized decellularized kidney scaffold (HEP-DKSs) was prepared using end-point attachment technology, followed by binding the vascular endothelial growth factor (VEGF) to greatly improve the hemocompatibility and angiogenesis of DKSs. Based on the anticoagulant, co-culture of human umbilical vein endothelial cells, and subcapsular transplantation of kidney experiments, HEP-VEGF-DKSs are shown to reduce platelet adhesion, which is crucial for subsequent vascularization and slow release of heparin and VEGF, suggesting its ability of improve neovascularization. Taken together, these data indicated an optimal anticoagulation function of HEP-VEGF-DKSs and the potential of vascularization for regeneration of whole decellularized kidney.

Incorporation of heparin/BMP2 complex on GOCS-modified magnesium alloy to synergistically improve corrosion resistance, anticoagulation, and osteogenesis

The in vivo fast degradation and poor biocompatibility are two major challenges of the magnesium alloys in the field of artificial bone materials. In this study, graphene oxide (GO) was first functionalized by chitosan (GOCS) and then immobilized on the magnesium alloy surface, finally the complex of heparin and bone morphogenetic protein 2 was incorporated on the modified surface to synergistically improve the corrosion resistance, anticoagulation, and osteogenesis. Apart from an excellent hydrophilicity after the surface modification, a sustained heparin and BMP2 release over 14 days was achieved. The corrosion resistance of the modified magnesium alloy was significantly better than that of the control according to the results of electrochemical tests. Moreover, the corrosion rate was also significantly reduced in contrast to the control. The modified magnesium alloy not only had excellent anticoagulation, but also can significantly promote osteoblast adhesion and proliferation, upregulate the expression of alkaline phosphatase and osteocalcin, and enhance mineralization. Therefore, the method of the present study can be used to simultaneously improve the corrosion resistance and biocompatibility of the magnesium alloys targeted for the orthopedic applications.

Effects of recipient age, heparin release and allogeneic bone marrow-derived stromal cells on vascular graft remodeling

Small-caliber vascular grafts are used in a wide range of clinical conditions. However, there remains a substantial unfulfilled need for readily-available, synthetic vascular grafts with high long-term patency rate. To fulfill the translational goal for bioengineered vascular grafts, important considerations for the pre-clinical evaluation include the graft design, cell incorporation and selection of an animal model. To assess the three factors, we used vascular grafts consisting of core/shell-structured microfibers of polycaprolactone/gelatin with a thin polycaprolactone overlay. The respective influences of the heparin release mode, animal age, and allogeneic bone marrow-derived stromal cells (MSCs) seeded in the lumen on the graft remodeling were assessed after four-and-half-month implantation on an interposition graft of abdominal aorta model. Except two rats dying from graft-unrelated issues, all other rats (18 out of 20) showed good graft patency upon explantation. The cell phenotype, matrix content and structure in the neotissues around the graft, as well as the flow perfusion through the graft were examined. More grafts in the aged rats showed local narrowing and flow incongruence than the other grafts in young adult rats. Compared to acellular grafts, cellular grafts showed efficient recruitment of vascular cells to form more organized structures with elastin in the vascular wall. Endothelialization and α−smooth muscle actin-positive cells were shown in all four types of vascular grafts. This study revealed the significant effects of MSC and recipient age but not heparin release pattern on graft remodeling. Statement of significanceThe vascular graft is a mainstream of surgical intervention to treat vascular diseases. Currently, vascular grafts, particularly small-diameter ones, still show high failure rates. This study has evaluated the respective impacts of heparin release pattern, allogeneic bone marrow-derived stromal cell seeding, and recipient age on the long-term remodeling of vascular grafts. There is a dearth of literature which considers the recipient age as an influencing factor for vascular grafting. However, adults particularly elderly constitute the majority of vascular graft recipients in the “real” clinical environment. While juvenile animals were widely used for graft evaluations, this study involved adult animals. The study outcomes provided important implications regarding graft designs and evaluation approaches.