Controlled release of heparin from poly(epsilon-caprolactone) electrospun fibers

Dexamethasone acetate loaded poly(ε-caprolactone) nanofibers for rat corneal chemical burn treatment

Topical eye drop approaches to treat ocular inflammation in dry eyes often face limitations such as low efficiency and short duration of drug delivery. Nanofibers serve to overcome the limitation of the short duration of action of topical eye drops used against ocular inflammation in dry eyes. Several attempts to develop suitable nanofibers have been made; however, there is no ideal solution. Here, we developed polycaprolactone (PCL) nanofibers loaded with dexamethasone acetate (DEX), prepared by electrospinning, as a potential ocular drug delivery platform for corneal injury treatment. Thirty-nine Sprague Dawley rats (7 weeks old males) were divided into four treatment groups after alkaline burns of the cornea; negative control (no treatment group); dexamethasone eyedrops (DEX group); PCL fiber (PCL group); dexamethasone loaded PCL (PCL + DEX group). We evaluated therapeutic efficacy of PCL + DEX by examining the epithelial wound healing effect, the extent of corneal opacity and neovascularization. Additionally, various inflammatory factors, including IL-1β, were investigated through immunochemistry, western blot analysis, and quantitative real-time RT-PCR (qRT-PCR). PCL + DEX group showed histologically alleviated signs of corneal inflammation compared with DEX group, which showed a decrease in IL-1β and MMP9 in the corneal stroma. The quantitative expression on day 1 after alkaline burn of pro-inflammatory markers, including IL-1β and IL-6, in the PCL + DEX group was significantly lower than that in the DEX group. Notably, PCL + DEX treatment significantly suppressed neovascularization, and enhanced the anti-inflammatory function of DEX during the acute phase of ocular inflammation. Collectively, these findings suggest that PCL + DEX may be a promising approach to effective drug delivery in corneal burn injuries.

Improving hemocompatibility in tissue-engineered products employing heparin-loaded nanoplatforms

The enhancement of hemocompatibility through the use of nanoplatforms loaded with heparin represents a highly desirable characteristic in the context of emerging tissue engineering applications. The significance of employing heparin in biological processes is unquestionable, owing to its ability to interact with a diverse range of proteins. It plays a crucial role in numerous biological processes by engaging in interactions with diverse proteins and hydrogels. This review provides a summary of recent endeavors focused on augmenting the hemocompatibility of tissue engineering methods through the utilization of nanoplatforms loaded with heparin. This study also provides a comprehensive review of the various applications of heparin-loaded nanofibers and nanoparticles, as well as the techniques employed for encapsulating heparin within these nanoplatforms. The biological and physical effects resulting from the encapsulation of heparin in nanoplatforms are examined. The potential applications of heparin-based materials in tissue engineering are also discussed, along with future perspectives in this field.

Photoresponsive heparin ionic complexes toward controllable therapeutic efficacy of anticoagulation

Controllable heparin-release is of great importance and necessity for the precise anticoagulant regulation. Efforts have been made on designing heparin-releasing systems, while, it remains a great challenge for gaining the external-stimuli responsive heparin-release in either intravenous or catheter delivery. In this study, an azobenzene-containing ammonium surfactant is designed and synthesized for the fabrication of photoresponsive heparin ionic complexes through the electrostatic complexation with heparin. Under the assistance of photoinduced trans-cis isomerization of azobenzene, the obtained heparin materials perform reversible athermal phase transition between ordered crystalline and isotropic liquid state at room temperature. Compared to the ordered state, the formation of isotropic state can effectively improve the dissolving of heparin from ionic materials in aqueous condition, which realizes the photo-modulation on the concentration of free heparin molecules. With good biocompatibility, such a heparin-releasing system addresses photoresponsive anticoagulation in both in vitro and in vivo biological studies, confirming its great potential clinical values. This work provides a new designing strategy for gaining anticoagulant regulation by light, also opening new opportunities for the development of photoresponsive drugs and biomedical materials based on biomolecules.

Organic Nanoparticles in Progressing Cardiovascular Disease Treatment and Diagnosis

Cardiovascular diseases (CVDs), the world's most prominent cause of mortality, continue to be challenging conditions for patients, physicians, and researchers alike. CVDs comprise a wide range of illnesses affecting the heart, blood vessels, and the blood that flows through and between them. Advances in nanomedicine, a discipline focused on improving patient outcomes through revolutionary treatments, imaging agents, and ex vivo diagnostics, have created enthusiasm for overcoming limitations in CVDs' therapeutic and diagnostic landscapes. Nanomedicine can be involved in clinical purposes for CVD through the augmentation of cardiac or heart-related biomaterials, which can be functionally, mechanically, immunologically, and electrically improved by incorporating nanomaterials; vasculature applications, which involve systemically injected nanotherapeutics and imaging nanodiagnostics, nano-enabled biomaterials, or tissue-nanoengineered solutions; and enhancement of sensitivity and/or specificity of ex vivo diagnostic devices for patient samples. Therefore, this review discusses the latest studies based on applying organic nanoparticles in cardiovascular illness, including drug-conjugated polymers, lipid nanoparticles, and micelles. Following the revised information, it can be concluded that organic nanoparticles may be the most appropriate type of treatment for cardiovascular diseases due to their biocompatibility and capacity to integrate various drugs.

AI-Driven Optimization of PCL/PEG Electrospun Scaffolds for Enhanced In Vivo Wound Healing

Here, an artificial intelligence (AI)-based approach was employed to optimize the production of electrospun scaffolds for in vivo wound healing applications. By combining polycaprolactone (PCL) and poly(ethylene glycol) (PEG) in various concentration ratios, dissolved in chloroform (CHCl3) and dimethylformamide (DMF), 125 different polymer combinations were created. From these polymer combinations, electrospun nanofiber meshes were produced and characterized structurally and mechanically via microscopic techniques, including chemical composition and fiber diameter determination. Subsequently, these data were used to train a neural network, creating an AI model to predict the optimal scaffold production solution. Guided by the predictions and experimental outcomes of the AI model, the most promising scaffold for further in vitro analyses was identified. Moreover, we enriched this selected polymer combination by incorporating antibiotics, aiming to develop electrospun nanofiber scaffolds tailored for in vivo wound healing applications. Our study underscores three noteworthy conclusions: (i) the application of AI is pivotal in the fields of material and biomedical sciences, (ii) our methodology provides an effective blueprint for the initial screening of biomedical materials, and (iii) electrospun PCL/PEG antibiotic-bearing scaffolds exhibit outstanding results in promoting neoangiogenesis and facilitating in vivo wound treatment.

Recent Advances in Polymers as Matrices for Drug Delivery Applications

Polymeric-based drug delivery systems have become versatile and valuable candidates in sectors such as pharmaceuticals, health, medicine, etc [...].

Epsin Mimetic UPI Peptide Delivery Strategies to Improve Endothelization of Vascular Grafts

Endothelialization of engineered vascular grafts for replacement of small-diameter coronary arteries remains a critical challenge. The ability for an acellular vascular graft to promote endothelial cell (EC) recruitment in the body would be very beneficial. This study investigated epsins as a target since they are involved in internalization of vascular endothelial growth factor receptor 2. Specifically, epsin-mimetic UPI peptides are delivered locally from vascular grafts to block epsin activity and promote endothelialization. The peptide delivery from fibrin coatings allowed for controlled loading and provided a significant improvement in EC attachment, migration, and growth in vitro. The peptides have even more important impacts after grafting into rat abdominal aortae. The peptides prevented graft thrombosis and failure that is observed with a fibrin coating alone. They also modulated the in vivo remodeling. The grafts are able to remodel without the formation of a thick fibrous capsule on the adventitia with the 100 µg mL-1 peptide-loaded condition, and this condition enabled the formation of a functional EC monolayer in the graft lumen after only 1 week. Overall, this study demonstrated that the local delivery of UPI peptides is a promising strategy to improve the performance of vascular grafts.

Development of a Silk Fibroin-Small Intestinal Submucosa Small-Diameter Vascular Graft with Sequential VEGF and TGF-β1 Inhibitor Delivery for In Situ Tissue Engineering

Proper endothelialization and limited collagen deposition on the luminal surface after graft implantation plays a crucial role to prevent the occurrence of stenosis. To achieve these conditions, a biodegradable graft with adequate mechanical properties and the ability to sequentially deliver therapeutic agents isfabricated. In this study, a dual-release system is constructed through coaxial electrospinning by incorporating recombinant human vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGF-β1) inhibitor into silk fibroin (SF) nanofibers to form a bioactive membrane. The functionalized SF membrane as the inner layer of the graft is characterized by the release profile, cell proliferation and protein expression. It presents excellent biocompatibility and biodegradation, facilitating cell attachment, proliferation, and infiltration. The core-shell structure enables rapid VEGF release within 10 days and sustained plasmid delivery for 21 days. A 2.0-mm-diameter vascular graft is fabricated by integrating the SF membrane with decellularized porcine small intestinal submucosa (SIS), aiming to facilitate the integration process under a stable extracellular matrix structure. The bioengineered graft is functionalized with the sequential administration of VEGF and TGF-β1, and with the reinforced and compatible mechanical properties, thereby offers an orchestrated solution for stenosis with potential for in situ vascular tissue engineering applications.

Recent advances on nanoparticle-based therapies for cardiovascular diseases

Nanoparticles are exclusively suitable for studying and developing potential therapies against cardiovascular diseases (CVD) because of their size, fine-tunable properties, and ability to incorporate therapeutic and imaging modalities. Recent advancements in nanomaterials open new avenues for treating CVD. In cardiology, the use of nanoparticles and nanocarriers has gathered significant consideration owing to characteristic features such as active and passive targeting to the cardiac tissues, greater target specificity, and sensitivity. It has been reported that through the use of nanotechnology, more than 50% of CVDs can be treated efficiently. Heart-targeted nano carrier-based drug delivery is an effective and efficient approach for treating cardiac-related disorders such as atherosclerosis, hypertension, and myocardial infarction. In this review, the authors focus on nanoparticle-based therapies used in CVD and provide an outline of essential knowledge and critical concerns on polymer-based nanomaterials in treating CVD.

Innovative antibacterial electrospun nanofibers mats depending on piezoelectric generation

This paper introduces a new approach of testing piezoelectric nanofibers as antibacterial mat. In this work, both Polyvinylidene fluoride (PVDF) and PVDF embedded with thermoplastic polyurethane nanofibers are synthesized as nanofibers mat via electrospinning technique. Then, such mat is analyzed as piezoelectric material to generate electric voltage under different mechanical excitations. Furthermore, morphological and chemical characteristics have been operated to prove the existence of beta sheets piezoelectricity of the synthesized nanofibers mats. Then, the synthesized nanofibers surfaces have been cyclically stretched and exposed to bacteria specimen. It has been noticed that the generated voltage and the corresponding localized electric field positively affect the growth of bacteria and reduces the formation of K. penomenue samples bacteria colonies. In addition, the effect of both stretching frequency and pulses numbers have been studied on the bacteria count, growth kinetics, and protein leakage. Our contribution here is to introduce an innovative way of the direct impact of the generated electric field from piezoelectric nanofibers on the reduction of bacteria growth, without depending on traditional anti-bacterial nanoparticles. This work can open a new trend of the usability of piezoelectric nanofibers through masks, filters, and wound curing mats within anti-bacterial biological applications.

Antifungal Activity of Camelus-Derived LFA-LFC Chimeric Peptide Gelatin Film and Effect on Oral Bacterial Biofilm

The objective of this study was to construct lactoferrin (LFA-LFC) chimeric peptide gelatin drug-loaded fiber film by tissue engineering strategy, and study its bacteriostatic effect on oral pathogens (especially Candida albicans) and its effect on biofilm. First of all, LFA-LFC chitosan nanoparticles were prepared firstly, and then fluconazole gelatin (LF/GH/F) film loaded with LFA-LFC was prepared by electrospinning. Scanning electron microscope (SEM), mechanical strength, drug release, cytotoxicity, and real-time PCR were used to test the properties of the synthesized materials. SEM showed that there was the reticular structure for fiber film before and after cross-linking. LF/GH/F film had no obvious cytotoxicity, with good biocompatibility and drug release; real-time PCR and antibacterial test showed that the LF/GH/F film had good antibacterial activity. LF/GH/F film has a good inhibitory effect on oral pathogens, and its mechanism is related to biofilm. The antibacterial experiments of nanofiber membrane in vitro and the effect of bacterial biofilm were carried out. The effect of LF/GH/F on oral microbial flora structure was studied by fluorescence quantitative pest techniques.

Evolution of Electrospinning in Liver Tissue Engineering

The major goal of liver tissue engineering is to reproduce the phenotype and functions of liver cells, especially primary hepatocytes ex vivo. Several strategies have been explored in the recent past for culturing the liver cells in the most apt environment using biological scaffolds supporting hepatocyte growth and differentiation. Nanofibrous scaffolds have been widely used in the field of tissue engineering for their increased surface-to-volume ratio and increased porosity, and their close resemblance with the native tissue extracellular matrix (ECM) environment. Electrospinning is one of the most preferred techniques to produce nanofiber scaffolds. In the current review, we have discussed the various technical aspects of electrospinning that have been employed for scaffold development for different types of liver cells. We have highlighted the use of synthetic and natural electrospun polymers along with liver ECM in the fabrication of these scaffolds. We have also described novel strategies that include modifications, such as galactosylation, matrix protein incorporation, etc., in the electrospun scaffolds that have evolved to support the long-term growth and viability of the primary hepatocytes.

Bioinspired Vascular Stents with Microfluidic Electrospun Multilayer Coatings for Preventing In-Stent Restenosis

In-stent restenosis (ISR) is seriously affecting the long-term prognosis of vascular interventional therapy and leading to enormous medical burdens. Great efforts have been devoted to developing functional vascular stents with desired features and properties for effective ISR prevention. Here, a multifunctional bionic vascular stent with designed coatings prepared using microfluidic electrospinning technology is presented. Such stents are composed of biocompatible, drug-loaded methylacrylated gelatin-polyethylene glycol diacrylate (GelMA-PEGDA) and polycaprolactone composite nanofibers on 316L stainless steel stents by an easy-to-operate step-by-step spraying method. Benefitting from the addition of polydopamine during the fabrications, the drug-loaded composite nanofibers can adhere well to both the stent and the vascular wall. Furthermore, as the inner fibrous layer of the stent contacting the lumen is equipped with heparin-vascular endothelial growth factor (Hep-VEGF), it plays an anticoagulation role and promotes the growth of endothelial cells; while the outer layer contacts the vascular wall and releases rapamycin slowly, which can restrain smooth muscle proliferation. By implanting this into the rabbit carotid artery, the multi-functional bionic demonstrates that the vascular stent can achieve good anti-thrombosis and in-stent restenosis effects, which indicates its potential values in vascular intervention and other biomedical fields.

Role of Biomaterials in Cardiac Repair and Regeneration: Therapeutic Intervention for Myocardial Infarction

Heart failure or myocardial infarction (MI) is one of the world's leading causes of death. Post MI, the heart can develop pathological conditions such as ischemia, inflammation, fibrosis, and left ventricular dysfunction. However, current surgical approaches are sufficient for enhancing myocardial perfusion but are unable to reverse the pathological changes. Tissue engineering and regenerative medicine approaches have shown promising effects in the repair and replacement of injured cardiomyocytes. Additionally, biomaterial scaffolds with or without stem cells are established to provide an effective environment for cardiac regeneration. Excipients loaded with growth factors, cytokines, oligonucleotides, and exosomes are found to help in such cardiac eventualities by promoting angiogenesis, cardiomyocyte proliferation, and reducing fibrosis, inflammation, and apoptosis. Injectable hydrogels, nanocarriers, cardiac patches, and vascular grafts are some excipients that can help the self-renewal in the damaged heart but are not understood well yet, in the context of used biomaterials. This review focuses on the use of various biomaterial-based approaches for the regeneration and repair of cardiac tissue postoccurrence of MI. It also discusses the outlines of cardiac remodeling and current therapeutic approaches after myocardial infarction, which are translationally important with respect to used biomaterials. It provides comprehensive details of the biomaterial-based regenerative approaches, which are currently the focus of the research for cardiac repair and regeneration and can provide a broad outline for further improvements.

Cytocompatibility and Antibacterial Properties of Coaxial Electrospun Nanofibers Containing Ciprofloxacin and Indomethacin Drugs

A coaxial nanofibrous scaffold of poly (ε-caprolactone) and gelatin/cellulose acetate encapsulating anti-inflammatory and antibacterial drugs was co-electrospun for skin tissue regeneration. Indomethacin and ciprofloxacin as model drugs were added to the core and the shell solutions, respectively. The effect of the drugs’ presence and crosslinking on the scaffold properties was investigated. TEM images confirmed the core−shell structure of the scaffold. The fiber diameter and the pore size of the scaffold increased after crosslinking. The tensile properties of the scaffold improved after crosslinking. The crosslinked scaffold illustrated a higher rate of swelling, and a lower rate of degradation and drug release compared to the uncrosslinked one. Fitting the release data into the Peppas equation showed that Fickian diffusion was the dominant mechanism of drug release from the scaffolds. The results of biocompatibility evaluations showed no cytotoxicity and suitable adhesion and cell growth on the prepared core−shell structure. The antibacterial activity of the scaffolds was studied against one of the most common pathogens in skin wounds, where the existence of ciprofloxacin could prevent the growth of the Staphylococcus aureus bacteria around the scaffold. The obtained results suggested a new coaxial nanofibrous scaffold as a promising candidate for simultaneous tissue regeneration and controlled drug release.

Development and Optimization of Osimertinib-loaded Biodegradable Polymeric Nanoparticles Enhance In-vitro Cytotoxicity in Mutant EGFR NSCLC Cell Models and In-vivo Tumor Reduction in H1975 Xenograft Mice Models

Osimertinib (OMB), a third-generation EGFR inhibitor, specifically and irreversibly inhibits EGFR_T790M mutant form. Nevertheless, its clinical use is limited due to poor solubility, low absorption, and oral bioavailability. To overcome the low therapeutic capabilities of the free drug, we developed OMB-loaded PCL or CHS nanoparticles and characterized them. Among fifteen devised nanoparticle formulations (Npfs), OMB-PCL-f3, f9, and OMB-CHS-f3 showed great characteristics such as particle size (ranges from 101.3 ± 8.2 to 119.7 ± 10.4 nm), zeta potential (-36.4 ± 3.2 to -31.7 ± 3.9 mV), and polydispersity index (0.227 ± 0.037 to 0.261 ± 0.025). The % entrapment (91.25 ± 5.84 to 95.25 ± 5.88) and drug loading (29.64 ± 2.38 to 33.59 ± 2.36) indicated the formulation optimization. OMB-CHS-f3 demonstrated long-term in-vitro release, with a % cumulative OMB release of 99.99 ± 2.67 within 24 h, and the cytotoxicity of OMB-CHS-f3 showed 2.6- and 2.4-fold superior activity in mutant EGFR harboring H1975 and PC-9 cells, respectively, compared to plain OMB. Quantitative assessment of OMB cellular uptake from OMB-CHS-f3 showed superior drug accumulation of 81.59 ± 5.8% and 77.31 ± 4.6% in H1975 and PC-9 cells which was more than OMB-CHS-f9 and plain OMB. Flow cytometric cell cycle analysis revealed that OMB-CHS-f3 triggered G2/M phase arrest greater than OMB-PCL-f9 and plain OMB. In vivo, OMB-CHS-f3 Npf treatment reduced tumor size and body weight gain compared to Tagrisso treatment (p < 0.05). These findings showed that chitosan-coated OMB Npfs might improve outcomes by overcoming complications, including resistance and disease recurrence in NSCLC patients.

Tubular TPU/SF nanofibers covered with chitosan-based hydrogels as small-diameter vascular grafts with enhanced mechanical properties

Native grafts such as internal mammary artery and saphenous vein are the main choice for coronary artery bypass graft. However, due to the limitations associated with their availability and rapid failure caused by hyperplasia, small diameter tissue-engineered vascular grafts (TEVGs) with sufficient post-implantation patency are urgently demanded as artificial alternatives. In our previous work, we innovatively fabricated a bilayer vascular graft providing appropriate structural and biological properties using electrospinning and freeze-drying methods. It was proved that the mechanical properties of the proposed graft enhanced in comparison with using either of methods individually. Here, we adopted the same methods and incorporated an anticoagulant internal layer (inner diameter 4 mm), comprised of co-electrospun fibers of silk fibroin (SF) and heparinized thermoplastic polyurethane (TPU), and an external highly porous hydrogel fabricated by freeze-drying method. The electrospun layer exhibited strong mechanical properties including superior elastic modulus (4.92 ± 0.11 MPa), suture retention force (6.73 ± 0.83 N), elongation at break (196 ± 4%), and comparable burst pressure (1140 ± 12 mmHg) while the external hydrogel provided SMCs viability. The heparin was released in a sustain manner over 40 days, and the cytocompatibility and blood compatibility of scaffold were approved using MTT assay and platelet adhesion test. Thus, the proposed graft has a potential to be used as an artificial blood vessel scaffold for later in-vivo transplantation.

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.

SpAD Biofunctionalized Cellulose Acetate Scaffolds Inhibit Staphylococcus aureus Adherence in a Coordinating Function with the von Willebrand A1 Domain (vWF A1)

Staphylococcus aureus is one of the major pathogens causing and spreading hospital acquired infections. Since it is highly resistant to new generation antibiotics, novel strategies have to be developed such as the construction of biofunctionalized non-adherent surfaces that will prevent its tethering and subsequent spread in the hospital environment. In this frame, the domain D of protein A (SpAD) of S. aureus has been immobilized onto cellulose acetate scaffolds by using the streptavidin/biotin interaction, in order to study its interaction with the A1 domain of von Willebrand factor (vWF A1), a protein essential for hemostasis, found in human plasma. Subsequently, the biofunctionalized cellulose acetate scaffolds were incubated with S. aureus in the presence and absence of vWF A1 at different time periods and their potential to inhibit S. aureus growth was studied with scanning electron microscopy (SEM). The SpAD biofunctionalized scaffolds perceptibly ameliorated the non-adherent properties of the material, and in particular, the interaction between SpAD and vWF A1 effectively inhibited the growth of S. aureus. Thus, the exhibition of significant non-adherent properties of scaffolds addresses their potential use for covering medical equipment, implants, and stents.

A Comparative Study of an Anti-Thrombotic Small-Diameter Vascular Graft with Commercially Available e-PTFE Graft in a Porcine Carotid Model

Background:

We have designed a reinforced drug-loaded vascular graft composed of polycaprolactone (PCL) and polydioxanone (PDO) via a combination of electrospinning/3D printing approaches. To evaluate its potential for clinical application, we compared the in vivo blood compatibility and performance of PCL/PDO + 10%DY grafts doped with an antithrombotic drug (dipyridamole) with a commercial expanded polytetrafluoroethylene (e-PTFE) graft in a porcine model.

Methods:

A total of 10 pigs (weight: 25–35 kg) were used in this study. We made a new 5-mm graft with PCL/PDO composite nanofiber via the electrospinning technique. We simultaneously implanted a commercially available e-PTFE graft (n = 5) and our PCL/PDO + 10%DY graft (n = 5) into the carotid arteries of the pigs. No anticoagulant/antiplatelet agent was administered during the follow-up period, and ultrasonography was performed weekly to confirm the patency of the two grafts in vivo. Four weeks later, we explanted and compared the performance of the two grafts by histological analysis and scanning electron microscopy (SEM).

Results:

No complications, such as sweating on the graft or significant bleeding from the needle hole site, were seen in the PCL/PDO + 10%DY graft immediately after implantation. Serial ultrasonographic examination and immunohistochemical analysis demonstrated that PCL/PDO + 10%DY grafts showed normal physiological blood flow and minimal lumen reduction, and pulsed synchronously with the native artery at 4 weeks after implantation. However, all e-PTFE grafts occluded within the study period. The luminal surface of the PCL/PDO + 10%DY graft in the transitional zone was fully covered with endothelial cells as observed by SEM.

Conclusion:

The PCL/PDO + 10%DY graft was well tolerated, and no adverse tissue reaction was observed in porcine carotid models during the short-term follow-up. Colonization of the graft by host endothelial and smooth muscle cells coupled with substantial extracellular matrix production marked the regenerative capability. Thus, this material may be an ideal substitute for vascular reconstruction and bypass surgeries. Long-term observations will be necessary to determine the anti-thrombotic and remodeling potential of this device.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13770-021-00422-4.

Reactive Magnetron Plasma Modification of Electrospun PLLA Scaffolds with Incorporated Chloramphenicol for Controlled Drug Release

Surface modification with the plasma of the direct current reactive magnetron sputtering has demonstrated its efficacy as a tool for enhancing the biocompatibility of polymeric electrospun scaffolds. Improvement of the surface wettability of materials with water, as well as the formation of active chemical bonds in the near-surface layers, are the main reasons for the described effect. These surface effects are also known to increase the release rate of drugs incorporated in fibers. Herein, we investigated the effect of plasma modification on the chloramphenicol release from electrospun poly (lactic acid) fibrous scaffolds. Scaffolds with high-50 wt./wt.%-drug content were obtained. It was shown that plasma modification leads to an increase in the drug release rate and drug diffusion coefficient, while not deteriorating surface morphology and mechanical properties of scaffolds. The materials' antibacterial activity was observed to increase in the first day of the experiment, while remaining on the same level as the unmodified group during the next six days. The proposed technique for modifying the surface of scaffolds will be useful for obtaining drug delivery systems with controlled accelerated release, which can expand the possibilities of local applications of antibiotics and other drugs.

Electrospun poly(ω-pentadecalactone-co-ε-caprolactone)/gelatin/chitosan ternary nanofibers with antibacterial activity for treatment of skin infections

In recent years, there is an increasing attention on biocompatible electrospun nanofibers for drug delivery applications since they provide high surface area, controlled and sustained drug release, and they mimic the extracellular matrix. In the present study, tetracycline hydrochloride (TCH) antibiotic loaded poly(ω-pentadecalactone-co-ε-caprolactone)/gelatin/chitosan nanofibrous membranes were fabricated as a controlled drug delivery system. Poly(ω-pentadecalactone-co-ε-caprolactone) copolymer has been enzymatically synthesized in previous studies, thus it provides an originality to the membrane. Combination of a synthetic polymer, a protein, and a polysaccharide in order to obtain a synergetic effect is another novelty of this work and there exists limited examples for such electrospun membrane. Varied amounts of TCH was electrospun together with poly(ω-pentadecalactone-co-ε-caprolactone)/gelatin/chitosan (50/40/10 vol ratio) polymer blend (fiber diameters ranged between 85.7-225.2 nm) and several characterizations (morphological and molecular structure, wettability characteristics, and thermal behavior) were applied to examine the drug incorporation. Subsequently, in vitro drug release studies were conducted and mathematical modeling was applied for the detection of transport mechanism of drug. TCH release proceeded 14 days through an initial burst release in first hour and followed by a sustained release. 1% TCH-loaded sample was shown as optimal preparation with 96.5% total drug release and 11.8% initial burst release. TCH-loaded preparations demonstrated a good antibacterial activity against Gram-positive (Staphylococcus aureus and Bacillus subtilis) bacteria and a limited effect (no inhibition zone observed below 3% TCH concentration) against Gram-negative (Escherichia coli) bacterium. Thus, TCH concentrations of ≥ 3% could be preferred to obtain a wide-spectrum effectiveness. The presented drug delivery system is suggested to be applied for treatment of skin infections as a wound dressing device.

Bone Scaffolds: An Incorporation of Biomaterials, Cells, and Biofactors

Large injuries to bones are still one of the most challenging musculoskeletal problems. Tissue engineering can combine stem cells, scaffold biomaterials, and biofactors to aid in resolving this complication. Therefore, this review aims to provide information on the recent advances made to utilize the potential of biomaterials for making bone scaffolds and the assisted stem cell therapy and use of biofactors for bone tissue engineering. The requirements and different types of biomaterials used for making scaffolds are reviewed. Furthermore, the importance of stem cells and biofactors (growth factors and extracellular vesicles) in bone regeneration and their use in bone scaffolds and the key findings are discussed. Lastly, some of the main obstacles in bone tissue engineering and future trends are highlighted.

Polycaprolactone nanofibers as an adjuvant strategy for Tamoxifen release and their cytotoxicity on breast cancer cells

Breast cancer is the second leading cause of death in women, and tamoxifen citrate (TMX) is accepted widely for the treatment of hormone receptor-positive breast cancers. Several local drug-delivery systems, including nanofibers, have been developed for antitumor treatment. Nanofibers are biomaterials that mimic the natural extracellular matrix, and they have been used as controlled release devices because they enable highly efficient drug loading. The purpose of the present study was to develop polycaprolactone (PCL) nanofibers incorporating TMX for use in the treatment of breast tumors. Pristine PCL and PCL-TMX nanofibers were produced by electrospinning and characterized physiochemically using different techniques. In addition, an in vitro study of TMX release from the nanofibers was performed. The PCL-TMX nanofibers showed sustained TMX release up to 14 h, releasing 100% of the TMX. The Resazurin reduction assay was used to evaluate the TMX cytotoxicity on MCF-7 breast cancer cell line and PBMCs human. The PCL-TMX nanofiber was cytotoxic toPBMCs and MCF-7. Based on these results, the PCL-TMX nanofibers developed have potential as an alternative for local chronic TMX use for breast cancer treatment, however tissue tests must be done.

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.

Tension Stimulation of Tenocytes in Aligned Hyaluronic Acid/Platelet-Rich Plasma-Polycaprolactone Core-Sheath Nanofiber Membrane Scaffold for Tendon Tissue Engineering

To recreate the in vivo niche for tendon tissue engineering in vitro, the characteristics of tendon tissue underlines the use of biochemical and biophysical cues during tenocyte culture. Herein, we prepare core-sheath nanofibers with polycaprolactone (PCL) sheath for mechanical support and hyaluronic acid (HA)/platelet-rich plasma (PRP) core for growth factor delivery. Three types of core-sheath nanofiber membrane scaffolds (CSNMS), consisting of random HA-PCL nanofibers (Random), random HA/PRP-PCL nanofibers (Random+) or aligned HA/PRP-PCL (Align⁺) nanofibers, were used to study response of rabbit tenocytes to biochemical (PRP) and biophysical (fiber alignment) stimulation. The core-sheath structures as well as other pertinent properties of CSNMS have been characterized, with Align⁺ showing the best mechanical properties. The unidirectional growth of tenocytes, as induced by aligned fiber topography, was confirmed from cell morphology and cytoskeleton expression. The combined effects of PRP and fiber alignment in Align⁺ CSNMS lead to enhanced cell proliferation rates, as well as upregulated gene expression and marker protein synthesis. Another biophysical cue on tenocytes was introduced by dynamic culture of tenocyte-seeded Align⁺ in a bioreactor with cyclic tension stimulation. Augmented by this biophysical beacon from mechanical loading, dynamic cell culture could shorten the time for tendon maturation in vitro, with improved cell proliferation rates and tenogenic phenotype maintenance, compared to static culture. Therefore, we successfully demonstrate how combined use of biochemical/topographical cues as well as mechanical stimulation could ameliorate cellular response of tenocytes in CSNMS, which can provide a functional in vitro environmental niche for tendon tissue engineering.

Development of drug loaded cardiovascular prosthesis for thrombosis prevention using 3D printing

Cardiovascular disease (CVD) is a general term for conditions which are the leading cause of death in the world. Quick restoration of tissue perfusion is a key factor to combat these diseases and improve the quality and duration of patients' life. Revascularization techniques include angioplasty, placement of a stent, or surgical bypass grafting. For the latter technique, autologous vessels remain the best clinical option; however, many patients lack suitable autogenous due to previous operations and they are often unsuitable. Therefore, synthetic vascular grafts providing antithrombosis, neointimal hyperplasia inhibition and fast endothelialization are still needed. To address these limitations, 3D printed dipyridamole (DIP) loaded biodegradable vascular grafts were developed. Polycaprolactone (PCL) and DIP were successfully mixed without solvents and then vascular grafts were 3D printed. A mixture of high and low molecular weight PCL was used to better ensure the integration of DIP, which would offer the biological functions required above. Moreover, 3D printing technology provides the ability to fabricate structures of precise geometries from a 3D model, enabling to customize the vascular grafts' shape or size. The produced vascular grafts were fully characterized through multiple techniques and the last step was to evaluate their drug release, antiplatelet effect and cytocompatibility. The results suggested that DIP was properly mixed and integrated within the PCL matrix. Moreover, these materials can provide a sustained and linear drug release without any obvious burst release, or any faster initial release rates for 30 days. Compared to PCL alone, a clear reduced platelet deposition in all the DIP-loaded vascular grafts was evidenced. The hemolysis percentage of both materials PCL alone and PCL containing 20% DIP were lower than 4%. Moreover, PCL and 20% DIP loaded grafts were able to provide a supportive environment for cellular attachment, viability, and growth.

Recent progress in materials development and biological properties of GTR membranes for periodontal regeneration

Chronic periodontal is a very common infection that instigates the destruction of oral tissue, and for its treatment, it is necessary to minimize the infection and the defects regeneration. Periodontium consists of four types of tissues: (a) cementum, (b) periodontal ligament, (c) gingiva, and 4) alveolar bone. In separated cavities, regenerative process also allows various cell proliferations. Guided tissue regeneration (GTR) is a potential procedure that favors periodontal regrowth; however, some limitations (such as ineffective hemostatic property, poor mechanical property, and improper biodegradation) are also associated with it. This review mainly emphasizes on the following areas: (a) a summarized overview of the periodontium and its immunological situations, (b) recently utilized treatments for regeneration of distinctive periodontal tissues; (c) an overview of GTR membranes available commercially, and the latest developments on the characterization and processing of GTR membrane material; and 4) the function of the different non-polymeric/polymeric materials, which are acting as drug carriers, antibacterial agents, nanoparticles, and periodontal barrier membranes to prevent periodontal inflammation and to improve the strength of the GTR membrane.

Recent advances in PVA-polysaccharide based hydrogels and electrospun nanofibers in biomedical applications: A review

Among several types of carbohydrate polymers blend PVA hydrogel membranes used for biomedical applications in particular wound dressings; electrospun nanofibrous membranes have gained increased interest because of their extraordinary features e.g. huge surface area to volume ratio, high porosity, adequate permeability, excellent wound-exudates absorption capacity, architecture similarity with skin ECM and sustained release-profile over long time. In this study, modern perspectives of synthesized/developed electrospun nanofibrous hydrogel membranes based popular carbohydrate polymers blend PVA which recently have been employed for versatile biomedical applications particularly wound dressings, were discussed intensively and compared in detail with traditional fabricated membranes based films, as well. Clinically relevant and advantages of electrospun nanofibrous membranes were discussed in terms of their biocompatibility and easily fabrication and functionalization in different biomedical applications.

The evaluation of functional small intestinal submucosa for abdominal wall defect repair in a rat model: Potent effect of sequential release of VEGF and TGF-β1 on host integration

Ineffective vessel penetration and extracellular matrix (ECM) remodeling are responsible for the failure of porcine small intestinal submucosa (SIS)-repaired abdominal wall defects. Combined growth factors could be used as directing signals in a nature-mimicking strategy to improve this repair through mesh functionalization. In this work, vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGF-β1) were incorporated into a silk fibroin membrane via coaxial aqueous electrospinning to exploit their benefits of biological interactions. The membrane was sandwiched into the SIS bilayer as a functional mesh to repair partial-thickness defects in a rat model. Membrane characterization demonstrated that the core-shell structure ensured the independent distribution and sequential release of two regulators and protection of their bioactivities, which were confirmed by cell viability and protein expression. The mesh was further assessed to facilitate vasculature formation and collagen secretion in vitro, and exhibited better host integration than VEGF- or TGF-β1-containing mesh and developed reinforced mechanical properties compared with the VEGF-containing mesh after 28 days in vivo. Determination of the underlying biological interactions revealed that rapid VEGF release promotes angiogenesis and collagen secretion but initially potentiates the inflammatory response. Sustained TGF-β1 release at relatively low concentrations promoted VEGF for vessel permeation and maturation and steadily induced ECM remodeling under milder foreign body reactions. The functionalization of SIS improves repair by sufficient integration with timely remodeling and helps elucidate the related regulatory interactions.

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.

3D printed polymeric drug-eluting implants

An extrusion-based 3D printer has been used for the manufacturing of sustained drug release poly(ε-caprolactone) (PCL) implants. Such implants can address issues of reduced patient compliance due to the necessary frequent administration of conventional drug delivery systems, such as tablets, capsules and solutions. The selected model drug for this study was lidocaine. Polycaprolactone core-shell implants, as well as polymeric implants with no barrier shell were printed with different drug loading, without the addition of solvents or further excipients. Scanning Electron Microscopy (SEM) analysis revealed the structural integrity of the printed formulations, while Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD) and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) were used to detect potential chemical interactions or modifications. Raman spectroscopy was also used to study material distribution in the prints. The drug release rate of the differently printed formulations was evaluated using a USP4 flow-through cell apparatus. All printed implants demonstrated sustained lidocaine release and the effectiveness of the PCL barrier in this regard. The Korsmeyer-Peppas model was suggested as the best fit to drug release profiles for all the produced implants. This work demonstrates that hot-melt extrusion-based 3D printing is a robust and promising technology for the production of personalisable drug-eluting implants.

Berberine-releasing electrospun scaffold induces osteogenic differentiation of DPSCs and accelerates bone repair

The repair of skeletal defects in maxillofacial region remains an intractable problem, the rising technology of bone tissue engineering provides a new strategy to solve it. Scaffolds, a crucial element of tissue engineering, must have favorable biocompatibility as well as osteoinductivity. In this study, we prepared berberine/polycaprolactone/collagen (BBR/PCL/COL) scaffolds with different concentrations of berberine (BBR) (25, 50, 75 and 100 μg/mL) through electrospinning. The influence of dosage on scaffold morphology, cell behavior and in vivo bone defect repair were systematically studied. The results indicated that scaffolds could release BBR stably for up to 27 days. Experiments in vitro showed that BBR/PCL/COL scaffolds had appropriate biocompatibility in the concentration of 25-75 μg/mL, and 50 and 75 μg/mL scaffolds could significantly promote osteogenic differentiation of dental pulp stem cells. Scaffold with 50 μg/mL BBR was implanted into the critical bone defect of rats to evaluate the ability of bone repair in vivo. It was found that BBR/PCL/COL scaffold performed more favorable than polycaprolactone/collagen (PCL/COL) scaffold. Overall, our study is the first to evaluate the capability of in vivo bone repair of BBR/PCL/COL electrospun scaffold. The results indicate that BBR/PCL/COL scaffold has prospective potential for tissue engineering applications in bone regeneration therapy.

Effects of Polyvinylpyrrolidone and Ethyl Cellulose in Polyurethane Electrospun Nanofibers on Morphology and Drug Release Characteristics

Objectives

Polyurethanes (PUs) are a popular choice for composing nanofibers due to their spinnability, biocompatibility, high chemical stability, and good mechanical and elasticity properties. The desired release behaviors are also achieved by using combinations of PUs and various polymers. In this study, we investigated effects of polyvinylpyrrolidone (PVP) and ethyl cellulose (EC) on PU electrospun nanofibers in terms of morphological structures and drug release characteristics.

Materials and Methods

Nanofibers were prepared using blends of PU with either EC or PVP in different ratios by electrospinning. The effects of PVP or EC on the morphology and diameter of the prepared nanofibers were examined with scanning electron microscope (SEM). The compatibility of the components used in the formulations of nanofibers was determined by attenuated total reflection (ATR)-fourier-transform infrared (FTIR). Donepezil hydrochloride (DNP), a water soluble compound, was selected as a model drug to examine its release characteristics from both PU/PVP and PU/EC electrospun nanofibers. In vitro drug release studies from electrospun nanofibers were performed according to the method defined in the monograph as the "paddle over disk method" of United States Pharmacopeia 38.

Results

The SEM images showed that addition of EC or PVP to PU solutions did not affect the generation of nanofibers, and those formed had a smooth surface without beads in nanoscale. The ATR-FTIR spectra disclosed that EC and PVP were separately incorporated into the PU matrix. The in vitro release data indicated that the presence of EC or PVP in PU nanofibers dramatically changed the release behavior of DNP. PU/EC nanofibers (F4) provided sustained drug release with the Korsmeyer-Peppas drug release kinetic mechanism, in which the release rate was controlled by diffusion of the drug, while all of the PU/PVP nanofibers exhibited fast drug release.

Conclusion

Overall, these characteristics of PU/EC (10/8) electrospun nanofibers has suggested their potential use as a drug carrier from which water-soluble drug release may occur in a sustained fashion.

Poly-ion complex (PIC) formation of heparin and polyamines: PIC with tetrakis (3-aminopropyl) ammonium allows sustained release of heparin

Physical mixtures of cationic polymers and heparin have been developed to overcome the limitations of unfractionated heparin. In this study, we found that heparin associates with natural polyamines in water, resulting in the generation of a poly-ion complex (PIC). PIC formation (or stability) was influenced by the concentration and ratio of heparin and polyamines, molecular weight of heparin, nature of polyamines, and pH conditions. Interestingly, the PIC obtained when heparin and tetrakis (3-aminopropyl) ammonium (Taa) were mixed exhibited stability and was sticky in nature. PIC formation was due to an electrostatic interaction between heparin and Taa. Heparin-Taa PIC was administered subcutaneously to mice, and the time to maximum heparin concentration within the therapeutic range of heparin was markedly increased compared to that after a single dose of heparin. These results suggest that the quaternary ammonium structure of Taa is critical for the preparation of a stable PIC, thereby allowing the sustained release of heparin into the blood.

Electrospun Nanofibrous Membranes for Preventing Tendon Adhesion

Tendon injuries are frequent, and surgical interventions toward their treatment might result in significant clinical complications. Pretendinous adhesion results in the disruption of the normal gliding mechanism of a damaged tendon, painful movements, and an increased chance of rerupture in the future. To alleviate postsurgical tendon-sheath adhesions, many investigations have been directed toward the development of repair approaches using electrospun nanofiber scaffolds. Such methods mainly take advantage of nanofibrous membranes (NFMs) as physical barriers to prevent or minimize adhesion of a repaired tendon to its surrounding sheath. In addition, these nanofibers can also locally deliver antiadhesion and anti-inflammatory agents to reduce the risk of tendon adhesion. This article reviews recent advances in the design, fabrication, and characterization of nanofibrous membranes developed to serve as (i) biomimetic tendon sheaths and (ii) physical barriers. Various features of the membranes are discussed to present insights for further development of repair methods suitable for clinical practice.

[Influence of unmodified and modified sutures on experimental abdominal adhesive process]

OBJECTIVE

Experimental assessment of the effect of modified and unmodified surgical suture material on abdominal adhesive process.

MATERIAL AND METHODS

The study was performed on male rats of the Wistar subpopulation. There were 5 animals in each group. In all animals, midline abdominal incision was followed by suturing the parietal peritoneum with modified and unmodified suture material. All animals were euthanized with carbon dioxide vapors in 14 days after surgery. Macro- and microscopic assessment of severity of abdominal adhesive process was carried out. Two types of preparation of excised complexes 'peritoneum-suture material-adhesion' were applied for histological examination: paraffin sections and embedding in epoxy resin. Specimens were stained by Van Gieson and with methylene blue solution. Histological specimens were examined using Axio Imager A1 light microscope (Zeiss, Germany).

RESULTS

Polypropylene filaments result extensive adhesions occupying about 75% of the area. Adhesions have a dense structure with signs of vascularization. Modification of suture material with solution of polyhydroxybutyrate/hydroxyvalerate and heparin reduce severity of adhesions. The use of modified suture material was followed by adhesions with more loose structure, no signs of vascularization. Adhesions occupied less than 25% of the area. Histological examination of excised complexes 'peritoneum-suture material-adhesion' revealed accumulation of inflammatory cells around the unmodified suture material, while there were no signs of tissue inflammatory process around the modified sutures.

CONCLUSION

Application of polyhydroxybutyrate/hydroxyvalerate and heparin on the surface of surgical sutures is an effective method for prevention of abdominal adhesions.

Endothelialization of cardiovascular devices

Blood-contacting surfaces of cardiovascular devices are not biocompatible for creating an endothelial layer on them. Numerous research studies have mainly sought to modify these surfaces through physical, chemical and biological means to ease early endothelial cell (EC) adhesion, migration and proliferation, and eventually to build an endothelial layer on the surfaces. The first priority for surface modification is inhibition of protein adsorption that leads to inhibition of platelet adhesion to the device surfaces, which may favor EC adhesion. Surface modification through surface texturing, if applicable, can bring some hopeful outcomes in this regard. Surface modifications through chemical and/or biological means may play a significant role in easy endothelialization of cardiovascular devices and inhibit smooth muscle cell proliferation. Cellular engineering of cells relevant to endothelialization can boost the positive outcomes obtained through surface engineering. This review briefly summarizes recent developments and research in early endothelialization of cardiovascular devices. STATEMENT OF SIGNIFICANCE: Endothelialization of cardiovascular implants, including heart valves, vascular stents and vascular grafts is crucial to solve many problems in our health care system. Numerous research efforts have been made to improve endothelialization on the surfaces of cardiovascular implants, mainly through surface modifications in three ways - physically, chemically and biologically. This review is intended to highlight comprehensive research studies to date on surface modifications aiming for early endothelialization on the blood-contacting surfaces of cardiovascular implants. It also discusses future perspectives to help guide endothelialization strategies and inspire further innovations.

[Influence of suture material on the development of postoperative complications in vascular surgery and their prevention]

Postoperative complications in vascular surgery may be partly provoked by suture material. Analysis of the mechanisms of these complications may be useful for their prevention. Mechanisms of suture-induced thrombosis and neointimal hyperplasia, possible strategies for prevention of postoperative complications including those allowing drug deliveries directly to the vascular anastomosis area are discussed in the article. According to the literature data, heparin is the most optimal drug for modifying suture material and prevention of thrombosis and neointimal hyperplasia. Heparin delivery to the vascular anastomosis site will reduce the risk of thrombosis by inhibiting the activity of thrombin. Complex of heparin and antithrombin III increases inhibitory effect of antithrombin against thrombin. In addition, heparin is able to reduce proliferation of vascular smooth muscle cells through inhibition of the synthesis of extracellular matrix proteases involved in migration and proliferation of cells. Thus, heparin delivery to the vascular injury site may be used to prevent thrombosis and myoproliferative response. Moreover, this strategy prevents complications associated with systemic administration of anticoagulants.