Fibrinogen adsorption, platelet adhesion and activation on mixed hydroxyl-/methyl-terminated self-assembled monolayers

Electrospun membranes of diselenide-containing poly(ester urethane)urea for in situ catalytic generation of nitric oxide

Nitric oxide (NO) plays an important role as a signalling molecule in the biological system. Organoselenium-coated or grafted biomaterials have the potential to achieve controlled NO release as they can catalyse decomposition of endogenous S-nitrosothiols to NO. However, such biomaterials are often challenged by the loss of the catalytic sites, which can affect the stability in tissue repair applications. In this work, we prepare a diselenide-containing poly(ester urethane)urea (SePEUU) polymer with Se-Se in the backbone, which is further electrospun into fibrous membranes by blending with poly(ester urethane)urea (PEUU) without diselenide bonds. The presence of catalytic sites in the main chain demonstrates stable and long-lasting NO catalytic activity, while the porous structure of the fibrous membranes ensures uniform distribution of the catalytic sites and better contact with the donor-containing solution. PEUU/SePEUU50 in 50/50 mass ratio has a physiologically adapted rate of NO release, with a sustained generation of NO after exposure to PBS at 37 °C for 30 d. PEUU/SePEUU50 has a low hemolysis and protein adsorption, with mechanical properties in the wet state matching those of natural vascular tissues. It can promote the adhesion and proliferation of human umbilical vein endothelial cells in vitro and control the proliferation of vascular smooth muscle cells in the presence of NO generation. This study exhibits the electrospun fibrous membranes have potential for utilizing as hemocompatible biomaterials for regeneration of blood-contacting tissues.

High-density zwitterionic polymer brushes exhibit robust lubrication properties and high antithrombotic efficacy in blood-contacting medical devices

High-performance catheters are essential for interventional surgeries, requiring reliable anti-adhesive and lubricated surfaces. This article develops a strategy for constructing high-density sulfobetaine zwitterionic polymer brushes on the surface of catheters, utilizing dopamine and sodium alginate as the primary intermediate layers, where dopamine provides mussel-protein-like adhesion to anchor the polymer brushes to the catheter surface. Hydroxyl-rich sodium alginate increases the number of grafting sites and improves the grafting mass by more than 4 times. The developed high-density zwitterionic polymer brushes achieve long-lasting and effective lubricity (μ<0.0078) and are implanted in rabbits for four hours without bio-adhesion and thrombosis in the absence of anticoagulants such as heparin. Experiments and molecular dynamics simulations demonstrate that graft mass plays a decisive role in the lubricity and anti-adhesion of polymer brushes, and it is proposed to predict the anti-adhesion of polymer brushes by their lubricity to avoid costly and time-consuming bioassays during the development of amphoteric polymer brushes. A quantitative influence of hydration in the anti-adhesion properties of amphiphilic polymer brushes is also revealed. Thus, this study provides a new approach to safe, long-lasting lubrication and anticoagulant surface modification for medical devices in contact with blood. STATEMENT OF SIGNIFICANCE: High friction and bioadhesion on medical device surfaces can pose a significant risk to patients. In response, we have developed a safer, simpler, and more application-specific surface modification strategy that addresses both the lubrication and anti-bioadhesion needs of medical device surfaces. We used dopamine and sodium alginate as intermediate layers to drastically increase the grafting density of the zwitterionic brushes and enabled the modified surfaces to have an extremely low coefficient of friction (μ = 0.0078) and to remain non-bioadhesive for 4 hours in vivo. Furthermore, we used molecular dynamics simulations to gain insight into the mechanisms behind the superior anti-adhesion properties of the high-density polymer brushes. Our work contributes to the development and application of surface-modified coatings.

Influence of titanium nanoscale surface roughness on fibrinogen and albumin protein adsorption kinetics and platelet responses

Biomaterials with nanoscale topography have been increasingly investigated for medical device applications to improve tissue-material interactions. This study assessed the impact of nanoengineered titanium surface domain sizes on early biological responses that can significantly affect tissue interactions. Nanostructured titanium coatings with distinct nanoscale surface roughness were deposited on quartz crystal microbalance with dissipation (QCM-D) sensors by physical vapor deposition. Physico-chemical characterization was conducted to assess nanoscale surface roughness, nano-topographical morphology, wettability, and atomic composition. The results demonstrated increased projected surface area and hydrophilicity with increasing nanoscale surface roughness. The adsorption properties of albumin and fibrinogen, two major plasma proteins that readily encounter implanted surfaces, on the nanostructured surfaces were measured using QCM-D. Significant differences in the amounts and viscoelastic properties of adsorbed proteins were observed, dependent on the surface roughness, protein type, protein concentration, and protein binding affinity. The impact of protein adsorption on subsequent biological responses was also examined using qualitative and quantitative in vitro evaluation of human platelet adhesion, aggregation, and activation. Qualitative platelet morphology assessment indicated increased platelet activation/aggregation on titanium surfaces with increased roughness. These data suggest that nanoscale differences in titanium surface roughness influence biological responses that may affect implant integration.

Flexible Poly(vinyl chloride) with Durable Antibiofouling Property via Blending Star-Shaped Amphiphilic Poly(ε-caprolactone)-block-poly(methacryloxyethyl sulfobetaine)

Flexible poly(vinyl chloride) (PVC) plastics have been widely used in medical devices, but the preparation of antibiofouling flexible PVC materials that can maintain their antibiofouling performance when suffering deformation is still a challenge. In this work, we synthesized a series of amphiphilic star-shaped three-arm block copolymers SPCL-b-PSB, consisting of hydrophobic inner blocks poly(ε-caprolactone) (PCL) and hydrophilic outer blocks poly(methacryloxyethyl sulfobetaine) (PSB). Then, flexible PVC films were prepared by blending SPCL-b-PSB with PVC and plasticizer. Benefiting from the specific star-shaped topological structure of SPCL-b-PSB, hydrophilic PSB blocks of the copolymer could efficiently migrate to the surface of the film via annealing treatment, which give the film surface excellent hydrophilicity, while the latch-like entanglements between hydrophobic PCL blocks and PVC give the hydrophilic surface excellent stability. Antibiofouling properties of the blended films were investigated. The optimized blended film could reduce ∼94% of bovine serum albumin adsorption, ∼ 87% of lysozyme adsorption, and ∼89% of platelet adhesion and resist bacterial adhesion effectively. What is more, the blended films could maintain their antibiofouling performance when suffering stretching, rubbing, or bending. More than 86% of bovine serum albumin adsorption could be reduced, even when the film was stretched by 50%. This work provides a new strategy for the preparation of durable antibiofouling flexible plastics.

Preparation and Activity of Hemostatic and Antibacterial Dressings with Greige Cotton/Zeolite Formularies Having Silver and Ascorbic Acid Finishes

The need for prehospital hemostatic dressings that exert an antibacterial effect is of interest for prolonged field care. Here, we consider a series of antibacterial and zeolite formulary treatment approaches applied to a cotton-based dressing. The design of the fabric formulations was based on the hemostatic dressing TACGauze with zeolite Y incorporated as a procoagulant with calcium and pectin to facilitate fiber adherence utilizing silver nanoparticles, and cellulose-crosslinked ascorbic acid to confer antibacterial activity. Infra-red spectra were employed to characterize the chemical modifications on the dressings. Contact angle measurements were employed to document the surface hydrophobicity of the cotton fabric which plays a role in the contact activation of the coagulation cascade. Ammonium Y zeolite-treated dressings initiated fibrin equal to the accepted standard hemorrhage control dressing and showed similar improvement with antibacterial finishes. The antibacterial activity of cotton-based technology utilizing both citrate-linked ascorbate-cellulose conjugate analogs and silver nanoparticle-embedded cotton fibers was observed against Staphylococcus aureus and Klebsiella pneumoniae at a level of 99.99 percent in the AATCC 100 assay. The hydrogen peroxide levels of the ascorbic acid-based fabrics, measured over a time period from zero up to forty-eight hours, were in line with the antibacterial activities.

Efficient One-Step Passivation of Polyurethane Using Transurethanization

The uncontrolled accumulation of biological materials on the surface of medical devices through protein adsorption or cell adhesion causes adverse biological reactions in the living host system, leading to complications. In this study, poly(ethylene glycol) (PEG) is successfully grafted onto polyurethane (PU) surfaces by using a new strategy through a simple and efficient transurethanization reaction. The PEG hydroxyl group is deprotonated and then reacted with the PU surface to provide antiadhesive hydrophilic surfaces in a single step. Surface analysis techniques proved the grafting to be efficient and the formation of a hydrophilic polymeric layer at the surface of PU. Biological assays showed that the surface modification induced lower protein adsorption, cell, platelet, and bacterial adhesion than untreated surfaces, showing a potential for biomedical applications.

Factors Influencing Properties of Spider Silk Coatings and Their Interactions within a Biological Environment

Biomaterials are an indispensable part of biomedical research. However, although many materials display suitable application-specific properties, they provide only poor biocompatibility when implanted into a human/animal body leading to inflammation and rejection reactions. Coatings made of spider silk proteins are promising alternatives for various applications since they are biocompatible, non-toxic and anti-inflammatory. Nevertheless, the biological response toward a spider silk coating cannot be generalized. The properties of spider silk coatings are influenced by many factors, including silk source, solvent, the substrate to be coated, pre- and post-treatments and the processing technique. All these factors consequently affect the biological response of the environment and the putative application of the appropriate silk coating. Here, we summarize recently identified factors to be considered before spider silk processing as well as physicochemical characterization methods. Furthermore, we highlight important results of biological evaluations to emphasize the importance of adjustability and adaption to a specific application. Finally, we provide an experimental matrix of parameters to be considered for a specific application and a guided biological response as exemplarily tested with two different fibroblast cell lines.

Human Whole Blood Interactions with Craniomaxillofacial Reconstruction Materials: Exploring In Vitro the Role of Blood Cascades and Leukocytes in Early Healing Events

The present study investigated early interactions between three alloplastic materials (calcium phosphate (CaP), titanium alloy (Ti), and polyetheretherketone (PEEK) with human whole blood using an established in vitro slide chamber model. After 60 min of contact with blood, coagulation (thrombin-antithrombin complexes, TAT) was initiated on all test materials (Ti > PEEK > CaP), with a significant increase only for Ti. All materials showed increased contact activation, with the KK-AT complex significantly increasing for CaP (p < 0.001), Ti (p < 0.01), and PEEK (p < 0.01) while only CaP demonstrated a notable rise in KK-C1INH production (p < 0.01). The complement system had significant activation across all materials, with CaP (p < 0.0001, p < 0.0001) generating the most pronounced levels of C3a and sC5b-9, followed by Ti (p < 0.001, p < 0.001) and lastly, PEEK (p < 0.001, p < 0.01). This activation correlated with leukocyte stimulation, particularly myeloperoxidase release. Consequently, the complement system may assume a more significant role in the early stages post implantation in response to CaP materials than previously recognized. Activation of the complement system and the inevitable activation of leukocytes might provide a more favorable environment for tissue remodeling and repair than has been traditionally acknowledged. While these findings are limited to the early blood response, complement and leukocyte activation suggest improved healing outcomes, which may impact long-term clinical outcomes.

Tailoring crystallinity for hemocompatible and durable PEEK cardiovascular implants

Polymers have the potential to replace metallic or bioprosthetic heart valve components due to superior durability and inertness while allowing for native tissue-like flexibility. Despite these appealing properties, certain polymers such as polyetheretherketone (PEEK) have issues with hemocompatibility, which have previously been addressed through assorted complex processes. In this paper, we explore the enhancement of PEEK hemocompatibility with polymer crystallinity. Amorphous, semi-crystalline and crystalline PEEK are investigated in addition to a highly crystalline carbon fiber (CF)/PEEK composite material (CFPEEK). The functional group density of the PEEK samples is determined, showing that higher crystallinity results in increased amount of surface carbonyl functional groups. The increase of crystallinity (and negatively charged groups) appears to cause significant reductions in platelet adhesion (33 vs. 1.5 % surface coverage), hemolysis (1.55 vs. 0.75 %∙cm^-2), and thrombin generation rate (4840 vs. 1585 mU/mL/min/cm²). In combination with the hemocompatibility study, mechanical characterization demonstrates that tailoring crystallinity is a simple and effective method to control both hemocompatibility and mechanical performance of PEEK. Furthermore, the results display that CFPEEK composite performed very well in all categories due to its enhanced crystallinity and complete carbon encapsulation, allowing the unique properties of CFPEEK to empower new concepts in cardiovascular device design.

Investigation on Human Serum Protein Depositions Inside Polyvinylidene Fluoride-Based Dialysis Membrane Layers Using Synchrotron Radiation Micro-Computed Tomography (SR-μCT)

Hemodialysis (HD) membrane fouling with human serum proteins is a highly undesirable process that results in blood activations with further severe consequences for HD patients. Polyvinylidene fluoride (PVDF) membranes possess a great extent of protein adsorption due to hydrophobic interaction between the membrane surface and non-polar regions of proteins. In this study, a PVDF membrane was modified with a zwitterionic (ZW) polymeric structure based on a poly (maleic anhydride-alt-1-decene), 3-(dimethylamino)-1-propylamine derivative and 1,3-propanesultone. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and zeta potential analyses were used to determine the membrane's characteristics. Membrane fouling with human serum proteins (human serum albumin (HSA), fibrinogen (FB), and transferrin (TRF)) was investigated with synchrotron radiation micro-computed tomography (SR-μCT), which allowed us to trace the protein location layer by layer inside the membrane. Both membranes (PVDF and modified PVDF) were detected to possess the preferred FB adsorption due to the Vroman effect, resulting in an increase in FB content in the adsorbed protein compared to FB content in the protein mixture solution. Moreover, FB was shown to only replace HSA, and no significant role of TRF in the Vroman effect was detected; i.e., TRF content was nearly the same both in the adsorbed protein layer and in the protein mixture solution. Surface modification of the PVDF membrane resulted in increased FB adsorption from both the protein mixture and the FB single solution, which is supposed to be due to the presence of an uncompensated negative charge that is located at the COOH group in the ZW polymer.

A versatile strategy to construct free-standing multi-furcated vessels and a complicated vascular network in heterogeneous porous scaffolds via combination of 3D printing and stimuli-responsive hydrogels

Mimicking complex structures of natural blood vessels and constructing vascular networks in tissue engineering scaffolds are still challenging now. Herein we demonstrate a new and versatile strategy to fabricate free-standing multi-furcated vessels and complicated vascular networks in heterogeneous porous scaffolds by integrating stimuli-responsive hydrogels and 3D printing technology. Through the sol-gel transition of temperature-responsive gelatin and conversion between two physical crosslinking networks of pH-responsive chitosan (i.e., electrostatic network between protonated chitosan and sulfate ion, crystalline network of neutral chitosan), physiologically-stable gelatin/chitosan hydrogel tubes can be constructed. While stimuli-responsive hydrogels confer the formation mechanism of the hydrogel tube, 3D printing confers the feasibility to create a multi-furcated structure and interconnected network in various heterogeneous porous scaffolds. As a consequence, biomimetic multi-furcated vessels (MFVs) and heterogeneous porous scaffolds containing multi-furcated vessels (HPS-MFVs) can be constructed precisely. Our data further confirm that the artificial blood vessel (gelatin/chitosan hydrogel tube) shows good physiological stability, mechanical strength, semi-permeability, hemocompatibility, cytocompatibility and low in vivo inflammatory response. Co-culture of hepatocyte (L02 cells) and human umbilical vein endothelial cells (HUVECs) in HPS-MFVs indicates the successful construction of a liver model. We believe that our method offers a simple and easy-going way to achieve robust fabrication of free-standing multi-furcated blood vessels and prevascularization of porous scaffolds for tissue engineering and regenerative medicine.

Blood Coagulation on Titanium Dioxide Films with Various Crystal Structures on Titanium Implant Surfaces

Background: Titanium (Ti) is one of the most popular implant materials, and its surface titanium dioxide (TiO₂) provides good biocompatibility. The coagulation of blood on Ti implants plays a key role in wound healing and cell growth at the implant site; however, researchers have yet to fully elucidate the mechanism underlying this process on TiO₂. Methods: This study examined the means by which blood coagulation was affected by the crystal structure of TiO₂ thin films (thickness < 50 nm), including anatase, rutile, and mixed anatase/rutile. The films were characterized in terms of roughness using an atomic force microscope, thickness using an X-ray photoelectron spectrometer, and crystal structure using transmission electron microscopy. The surface energy and dielectric constant of the surface films were measured using a contact angle goniometer and the parallel plate method, respectively. Blood coagulation properties (including clotting time, factor XII contact activation, fibrinogen adsorption, fibrin attachment, and platelet adhesion) were then assessed on the various test specimens. Results: All of the TiO₂ films were similar in terms of surface roughness, thickness, and surface energy (hydrophilicity); however, the presence of rutile structures was associated with a higher dielectric constant, which induced the activation of factor XII, the formation of fibrin network, and platelet adhesion. Conclusions: This study provides detailed information related to the effects of TiO₂ crystal structures on blood coagulation properties on Ti implant surfaces.

Hemocompatibility Evaluation of Thai Bombyx mori Silk Fibroin and Its Improvement with Low Molecular Weight Heparin Immobilization

Bombyx mori silk fibroin (SF), from Nangnoi Srisaket 1 Thai strain, has shown potential for various biomedical applications such as wound dressing, a vascular patch, bone substitutes, and controlled release systems. The hemocompatibility of this SF is one of the important characteristics that have impacts on such applications. In this study, the hemocompatibility of Thai SF was investigated and its improvement by low molecular weight heparin (LMWH) immobilization was demonstrated. Endothelial cell proliferation on the SF and LMWH immobilized SF (Hep/SF) samples with or without fibroblast growth factor-2 (FGF-2) was also evaluated. According to hemocompatibility evaluation, Thai SF did not accelerate clotting time, excess stimulate complement and leukocyte activation, and was considered a non-hemolysis material compared to the negative control PTFE sheet. Platelet adhesion of SF film was comparable to that of the PTFE sheet. For hemocompatibility enhancement, LMWH was immobilized successfully and could improve the surface hydrophilicity of SF films. The Hep/SF films demonstrated prolonged clotting time and slightly lower complement and leukocyte activation. However, the Hep/SF films could not suppress platelet adhesion. The Hep/SF films demonstrated endothelial cell proliferation enhancement, particularly with FGF-2 addition. This study provides fundamental information for the further development of Thai SF as a hemocompatible biomaterial.

Structure-Property Relationship Based on the Amino Acid Composition of Recombinant Spider Silk Proteins for Potential Biomedical Applications

Improving biomaterials by engineering application-specific and adjustable properties is of increasing interest. Most of the commonly available materials fulfill the mechanical and physical requirements of relevant biomedical applications, but they lack biological functionality, including biocompatibility and prevention of microbial infestation. Thus, research has focused on customizable, application-specific, and modifiable surface coatings to cope with the limitations of existing biomaterials. In the case of adjustable degradation and configurable interaction with body fluids and cells, these coatings enlarge the applicability of the underlying biomaterials. Silks are interesting coating materials, e.g., for implants, since they exhibit excellent biocompatibility and mechanical properties. Herein, we present putative implant coatings made of five engineered recombinant spider silk proteins derived from the European garden spider Araneus diadematus fibroins (ADF), differing in amino acid sequence and charge. We analyzed the influence of the underlying amino acid composition on wetting behavior, blood compatibility, biodegradability, serum protein adsorption, and cell adhesion. The outcome of the comparison indicates that spider silk coatings can be engineered for explicit biomedical applications.

Race for Applicable Antimicrobial Dental Implant Surfaces to Fight Biofilm-Related Disease: Advancing in Laboratorial Studies vs Stagnation in Clinical Application

Across years, potential strategies to fight peri-implantitis have been notoriously explored through the antimicrobial coating implant surfaces capable of interfering with the bacterial adhesion process. However, although experimental studies have significantly advanced, no product has been marketed so far. For science to reach the society, the commercialization of research outcomes is necessary to provide real advancement in the biomedical field. Therefore, the aim of this study was to investigate the challenges involved in the development of antimicrobial dental implant surfaces to fight peri-implantitis, through a systematic search. Research articles reporting antimicrobial dental implant surfaces were identified by searching PubMed, Scopus, Web of Science, The Cochrane Library, Embase, and System of Information on Grey Literature in Europe, between 2008 and 2020. A total of 1778 studies were included for quality assessment and the review. An impressive number of 1655 articles (93,1%) comprised in vitro studies, whereas 123 articles refer to in vivo investigations. From those 123, 102 refer to animal studies and only 21 articles were published on the clinical performance of antibacterial dental implant surfaces. The purpose of animal studies is to test how safe and effective new treatments are before they are tested in people. Therefore, the discrepancy between the number of published studies clearly reveals that preclinical investigations still come up against several challenges to overcome before moving forward to a clinical setting. Additionally, researchers need to recognize that the complex journey from lab to market requires more than a great idea and resources to develop a commercial invention; research teams must possess the skills necessary to commercialize an invention.

Development and Validation of a Novel Tool for the Prediction of Clopidogrel Response in Chinese Acute Coronary Syndrome Patients: The GeneFA Score

Aim: Growing evidence indicated that CYP2C19 genotypes could only explain a fraction of the pharmacodynamic response to clopidogrel, while a number of clinical factors also have contributing roles. Our objective was to develop a new risk score to improve prognostication of ischemic events in Chinese patients treated with clopidogrel. Methods: A new risk score was developed and internally validated in 445 patients with acute coronary syndrome (ACS) undergoing coronary stenting. The final score was named the GeneFA score based on the inclusion of CYP2C19 genotype, fibrinogen, and age. External validation of the GeneFA score and comparison with the ABCD-GENE score were performed in an independent ACS cohort. Results: Based on the observed frequencies of high platelet reactivity (HRPR) in relation to the GeneFA risk score, a relatively higher clinical HRPR was observed in the upper quintile with a representative score of 3 (52.90%) and 4 (59.10%), whereas it was found less frequently in groups with scores 0 (6.70%), 1 (15.10%), and 2 (16.70%). Participants with a GeneFA score >2 had an increased risk of HRPR (54.3 vs. 14.7%, p < 0.001) and ischemic recurrence (20.7 vs. 5.4%, p < 0.001). The GeneFA score exhibited a better prediction for high HRPR patients as compared to the ABCD-GENE score (p < 0.001). In the validation population, GeneFA illustrated a similarly high prognostic value for HRPR incidence (C-statistic: 0.855 for GeneFA and 0.843 for ABCD-GENE) and ischemic recurrence (C-statistic: 0.726 for GeneFA and 0.724 for ABCD-GENE) on clopidogrel as compared to ABCD-GENE. Conclusion: The GeneFA risk score had a moderate predictive ability for HRPR on clopidogrel for CAD patients in Chinese populations. The predictive value of the GeneFA score was consistent with the ABCD-GENE score for HRPR identification.

Rational design of hydrogels for immunomodulation

The immune system protects organisms against endogenous and exogenous harm and plays a key role in tissue development, repair, and regeneration. Traditional immunomodulatory biologics exhibit limitations including degradation by enzymes, short half-life, and lack of targeting ability. Encapsulating or binding these biologics within biomaterials is an effective way to address these problems. Hydrogels are promising immunomodulatory materials because of their prominent biocompatibility, tuneability, and versatility. However, to take advantage of these opportunities and optimize material performance, it is important to more specifically elucidate, and leverage on, how hydrogels affect and control the immune response. Here, we summarize how key physical and chemical properties of hydrogels affect the immune response. We first provide an overview of underlying steps of the host immune response upon exposure to biomaterials. Then, we discuss recent advances in immunomodulatory strategies where hydrogels play a key role through a) physical properties including dimensionality, stiffness, porosity, and topography; b) chemical properties including wettability, electric property, and molecular presentation; and c) the delivery of bioactive molecules via chemical or physical cues. Thus, this review aims to build a conceptual and practical toolkit for the design of immune-instructive hydrogels capable of modulating the host immune response.

Enhanced blood coagulation and antibacterial activities of carboxymethyl-kappa-carrageenan-containing nanofibers

Ideal wound dressings should be biocompatible, exhibit high antibacterial activity, and promote blood coagulation. To impart these imperative functions, carboxymethyl-kappa-carrageenan was incorporated into poly(vinyl alcohol) nanofibers (PVA-CMKC). The antibacterial activity of the nanofibers was evaluated. Adsorption of two important blood proteins, fibrinogen and albumin, was also assessed. The adhesion and activation of platelets, and the clotting of whole blood were evaluated to characterize the ability of the nanofibers to promote hemostasis. Adhesion and morphology of both Staphylococcus aureus and Pseudomonas aeruginosa were evaluated using fluorescence microscopy and scanning electron microscopy. CMKC-containing nanofibers demonstrated significant increases in platelet adhesion and activation, percentage of coagulation in whole blood clotting test and fibrinogen adsorption, compared to PVA nanofibers, showing blood coagulation activity. Incorporating CMKC also reduces adhesion and viability of S. aureus and P. aeruginosa bacteria after 24 h of incubation. PVA-CMKC nanofibers show potential application as dressings for wound healing applications.

Peptide-Modified Surfaces for Binding Carbamylated Proteins from Plasma

Carbamylation of blood proteins is a common post-translational modification that occurs upon kidney dysfunction that is strongly associated with deleterious outcomes for patients treated using hemodialysis. In this study, we focused on the removal of two representative carbamylated plasma proteins, carbamylated albumin (cHSA) and fibrinogen (cFgn), through adsorption onto a surface functionalized with a specific peptide (cH2p1). Surfaces modified with poly(hydroxyethyl methacrylate) (p(HEMA)) were prepared using surface-initiated atom transfer radical polymerization (SI-ATRP) techniques and functionalized with cH2p1. cH2p1-functionalized surfaces showed selective binding toward cHSA and cFgn, compared to their native protein form, with NH-cH2p1 of superior selectivity than CO-cH2p1. The adsorption capacity of carbamylated protein on NH-cH2p1 was maintained in diluted plasma, and ultralow adsorption of native Fgn was observed. Similar to unmodified p(HEMA) surfaces, NH-cH2p1 showed a low platelet adhesion and activation, suggesting that the designed surface does not adversely affect platelets.

Antithrombotic and hemocompatible properties of nanostructured coatings assembled from block copolymers

We describe the antithrombotic properties of nanopatterned coatings created by self-assembly of poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) with different molecular weights. By changing the assembly conditions, we obtained nanopatterns that differ by their morphology (size and shape of the nanopattern) and chemistry. The surface exposition of P2VP block allowed quaternization, i.e. introduction of positive surface charge and following electrostatic deposition of heparin. Proteins (albumin and fibrinogen) adsorption, platelet adhesion and activation, cytocompatibility, and reendothelization capacity of the coatings were assessed and discussed in a function of the nanopattern morphology and chemistry. We found that quaternization results in excellent antithrombotic and hemocompatible properties comparable to heparinization by hampering the fibrinogen adhesion and platelet activation. In the case of quaternization, this effect depends on the size of the polymer blocks, while all heparinized patterns had similar performance showing that heparin surface coverage of 40 % is enough to improve substantially the hemocompatibility.

Response of RAW 264.7 and J774A.1 macrophages to particles and nanoparticles of a mesoporous bioactive glass: A comparative study

Mesoporous bioactive glasses (MBGs) are bioceramics designed to induce bone tissue regeneration and very useful materials with the ability to act as drug delivery systems. MBGs can be implanted in contact with bone tissue in different ways, as particulate material, in 3D scaffolds or as nanospheres. In this work, we assessed the effects of particles of mesoporous bioactive glass MBG-75S and mesoporous nanospheres NanoMBG-75S on RAW 264.7 and J774A.1 macrophages, which present different sensitivity and are considered as ideal models for the study of innate immune response. After evaluating several cellular parameters (morphology, size, complexity, proliferation, cell cycle and intracellular content of reactive oxygen species), the action of MBG-75S particles and NanoMBG-75S on the polarization of these macrophages towards the pro-inflammatory (M1) or reparative (M2) phenotype was determined by the expression of specific M1 (CD80) and M2 (CD206, CD163) markers. We previously measured the adsorption of albumin and fibrinogen on MBG-75S particles and the production of pro-inflammatory cytokines as TNF-α and IL-6 by macrophages in response to these particles. This comparative study demonstrates that particles of mesoporous bioactive glass MBG-75S and mesoporous nanospheres NanoMBG-75S allow the appropriated development and function of RAW 264.7 and J774A.1 macrophages and do not induce polarization towards the M1 pro-inflammatory phenotype. Therefore, considering that these mesoporous biomaterials offer the possibility of loading drugs into their pores, the results obtained indicate their high potential for use as drug-delivery systems in bone repair and osteoporosis treatments without triggering an adverse inflammatory response.

Surface modification of polytetrafluoroethylene (PTFE) with a heparin-immobilized extracellular matrix (ECM) coating for small-diameter vascular grafts applications

Intimal hyperplasia, thrombosis formation, and delayed endothelium regeneration are the main causes that restrict the clinical applications of PTFE small-diameter vascular grafts (inner diameter < 6 mm). An ideal strategy to solve such problems is to facilitate in situ endothelialization. Since the natural vascular endothelium adheres onto the basement membrane, which is a specialized form of extracellular matrix (ECM) secreted by endothelial cells (ECs) and smooth muscle cells (SMCs), functionalizing PTFE with an ECM coating was proposed. However, besides ECs, the ECM-modified PTFE improved SMC growth as well, thereby increasing the risk of intimal hyperplasia. In the present study, heparin was immobilized on the ECM coating at different densities (4.89 ± 1.02 μg/cm2, 7.24 ± 1.56 μg/cm2, 15.63 ± 2.45 μg/cm2, and 26.59 ± 3.48 μg/cm2), aiming to develop a bio-favorable environment that possessed excellent hemocompatibility and selectively inhibited SMC growth while promoting endothelialization. The results indicated that a low heparin density (4.89 ± 1.02 μg/cm2) was not enough to restrict platelet adhesion, whereas a high heparin density (26.59 ± 3.48 μg/cm2) resulted in decreased EC growth and enhanced SMC proliferation. Therefore, a heparin density at 7.24 ± 1.56 μg/cm2 was the optimal level in terms of antithrombogenicity, endothelialization, and SMC inhibition. Collectively, this study proposed a heparin-immobilized ECM coating to modify PTFE, offering a promising means to functionalize biomaterials for developing small-diameter vascular grafts.

What affects the biocompatibility of polymers?

In recent decades synthetic polymers have gained increasing popularity, and nowadays they are an integral part of people's daily lives. In addition, owing to their competitive advantage and being susceptible to modification, polymers have stimulated the fast development of innovative technologies in many areas of science. Biopolymers are of particular interest in various branches of medicine, such as implantology of bones, cartilage and skin tissues as well as blood vessels. Biomaterials with such specific applications must have appropriate mechanical and strength characteristics and above all they must be compatible with the surrounding tissues, human blood and its components, i.e. exhibit high hemo- and biocompatibility, low or no thrombo- and carcinogenicity, foreign body response (host response), appropriate osteoconduction, osteoinduction and mineralization. For biocompatibility improvement many surface treatment techniques have been utilized leading to fabricate the polymer biomaterials of required properties, also at nanoscale. This review paper discusses the most important physicochemical and biological factors that affect the biocompatibility, thus the reaction of the living organism after insertion of the polymer-based biomaterials, i.e. surface modification and/or degradation, surface composition (functional groups and charge), size and shapes, hydrophilic-hydrophobic character, wettability and surface free energy, topography (roughness, stiffness), crystalline and amorphous structure, nanostructure, cell adhesion and proliferation, cellular uptake. Particularly, the application of polysaccharides (chitosan, cellulose, starch) in the tissue engineering is emphasized.

The Role of Biodegradable Poly-(L-lactide)-Based Polymers in Blood Cell Activation and Platelet-Monocyte Interaction

The main purpose of new stent technologies is to overcome unfavorable material-related incompatibilities by producing bio- and hemo-compatible polymers with anti-inflammatory and anti-thrombogenic properties. In this context, wettability is an important surface property, which has a major impact on the biological response of blood cells. However, the influence of local hemodynamic changes also influences blood cell activation. Therefore, we investigated biodegradable polymers with different wettability to identify possible aspects for a better prediction of blood compatibility. We applied shear rates of 100 s⁻¹ and 1500 s⁻¹ and assessed platelet and monocyte activation as well as the formation of CD62P+ monocyte-bound platelets via flow cytometry. Aggregation of circulating platelets induced by collagen was assessed by light transmission aggregometry. Via live cell imaging, leukocytes were tracked on biomaterial surfaces to assess their average velocity. Monocyte adhesion on biomaterials was determined by fluorescence microscopy. In response to low shear rates of 100 s⁻¹, activation of circulating platelets and monocytes as well as the formation of CD62P+ monocyte-bound platelets corresponded to the wettability of the underlying material with the most favorable conditions on more hydrophilic surfaces. Under high shear rates, however, blood compatibility cannot only be predicted by the concept of wettability. We assume that the mechanisms of blood cell-polymer interactions do not allow for a rule-of-thumb prediction of the blood compatibility of a material, which makes extensive in vitro testing mandatory.

New Vascular Graft Using the Decellularized Human Chorion Membrane

The increase of both arterial occlusive diseases and coronary heart diseases leads to a higher demand for small-diameter vascular grafts (<6 mm). The gold standard for small-diameter vessel replacement is the use of autologous veins. Nevertheless, up to 30% of these patients need to use vascular grafts. Although synthetic polymers have been successfully used for the replacement of large-diameter vascular grafts (>6 mm), they are associated with thrombosis, intimal hyperplasia, calcification, and chronic inflammation when used as small-diameter vascular grafts. Therefore, natural materials have been studied for this application. In this study, a decellularized human chorion membrane (dHCM) vascular graft with a 3-4 mm diameter was created. Herein, the biocompatibility of dHCM with endothelial cells was demonstrated in vitro and ex ovo. Blood biocompatibility of dHCM was also shown by studying plasma protein adsorption, platelet adhesion and activation, and its hemolytic potential. Furthermore, dHCM antibacterial properties against Staphylococcus aureus were also studied. In summary, the dHCM reticular layer side presented all the needed characteristics to be used in the inner side of a vascular graft. Additionally, the mechanical properties of the dHCM tubular construct were studied, being similar to the ones of the saphenous vein, the gold standard for autologous small-diameter vessel replacement.

Effect of carbamylation on protein structure and adsorption to self-assembled monolayer surfaces

Protein adsorption research has primarily focused upon the effects of surface chemistry, with almost no emphasis on how changes to proteins that occur in various disease states may influence their adsorption. One such situation occurs with chronic kidney disease where, despite hemodialysis treatment, the retention of urea within the blood compartment leads to protein carbamylation. Protein carbamylation has been shown to alter the function and structure of proteins. This work is focused on understanding how different degrees of carbamylation affect the physicochemical properties (structure, charge, water interactions) of single proteins (α-lactalbumin, albumin, and fibrinogen) and their adsorption to self-assembled monolayers. It was found that, unlike its secondary structure, the protein's tertiary structure was significantly altered upon carbamylation. Also, compared to native proteins, an increase in carbamylation lead to an increase in the negative surface charge of the protein and a weaker hydration state of the protein. In order to study the effects of different types of neutral surfaces, of different surface-water properties, on protein adsorption both bare and alkanethiol modified (-CH₃ or -OH end-groups) Au surfaces with were used as model surfaces. A significant decrease in adsorbed amounts of carbamylated fibrinogen and carbamylated α-lactalbumin, but not for carbamylated albumin, relative to native proteins was observed for both surfaces; suggesting that the increase in negative surface charge is more influential on adsorption than the change in hydration that occurs throughout the protein upon carbamylation. This data suggests that protein alterations that occur due to disease states have a significant effect on the overall protein structure and these changes affect their adsorption to surfaces.

Highly tough and ultrafast self-healable dual physically crosslinked sulfated alginate-based polyurethane elastomers for vascular tissue engineering

Since vascular diseases are regarded as a major cause of death worldwide, developing engineered biomimetic elastomers with physicochemical and biological properties resembling those of the natural vascular tissues, is vital for vascular tissue engineering (VTE). This study reports synthesis of highly tough supramolecular biologically active alginate-based supramolecular polyurethane (BASPU) elastomers that benefit from the presence of two physical networks with different strength of soft tertiary ammonium-soft sulfate pairs, as strong ionic bonds, and soft tertiary ammonium-hard carboxylate groups, as the weak bonds. The presence of sulfate groups resulted in low Young's modulus, high toughness and stretchability, proper energy dissipation, ultrafast self-healing and complete healing efficiency of BASPU. In vitro studies showed higher endothelial cells attachment, higher anticoagulation ability and significantly less platelet adhesion for BASPUs compared to the commercial vascular prosthesis. The histological studies of subcutaneously implanted scaffolds confirmed their low fibrosis and gradual biodegradation during 2 months of following.

Understanding Surface Modifications Induced via Argon Plasma Treatment through Secondary Electron Hyperspectral Imaging

Understanding the effects that sterilization methods have on the surface of a biomaterial is a prerequisite for clinical deployment. Sterilization causes alterations in a material's surface chemistry and surface structures that can result in significant changes to its cellular response. Here we compare surfaces resulting from the application of the industry standard autoclave sterilisation to that of surfaces resulting from the use of low-pressure Argon glow discharge within a novel gas permeable packaging method in order to explore a potential new biomaterial sterilisation method. Material surfaces are assessed by applying secondary electron hyperspectral imaging (SEHI). SEHI is a novel low-voltage scanning electron microscopy based characterization technique that, in addition to capturing topographical images, also provides nanoscale resolution chemical maps by utilizing the energy distribution of emitted secondary electrons. Here, SEHI maps are exploited to assess the lateral distributions of diverse functional groups that are effected by the sterilization treatments. This information combined with a range of conventional surface analysis techniques and a cellular metabolic activity assay reveals persuasive reasons as to why low-pressure argon glow discharge should be considered for further optimization as a potential terminal sterilization method for PGS-M, a functionalized form of poly(glycerol sebacate) (PGS).

Dendronized oligoethylene glycols with phosphonate tweezers for cell-repellent coating of oxide surfaces: coarse-scale and nanoscopic interfacial forces

Coarse-scale and nanoscopic interfacial force measurements unraveled how dendronized oligoethylene glycols with phosphonate tweezers prevent non-specific cell adhesion to oxide surfaces.

Controlling the adsorption of osteopontin for mediating cell behaviour by using self-assembled monolayers with varying surface chemistry

Osteopontin (OPN) is an important protein for mediating cell behaviour on biomaterials. However, the interactions between the chemical groups on the biomaterial surface and OPN still need to be further clarified, which has restricted the application of OPN in biomaterial functionalization. In the present study, we developed different self-assembled monolayers (SAMs) with specific chemical groups, including SAMs-OH, SAMs-OEG, SAMs-COOH, SAMs-NH₂, and SAMs-PO₃H₂, to study the behavior of OPN on these SAMs. The results showed that SAMs-NH₂ could strongly adsorb OPN, and the amount of protein was highest on this material. Meanwhile, the lowest amount of OPN was present on SAMs-OEG. Interestingly, the unit-mass trend of bound OPN monoclonal antibodies (mAbs) on the SAMs was opposite to the OPN adsorption trend: lowest on SAMs-NH₂ but highest on SAMs-OEG. In vitro cell assay results showed that mouse bone marrow mesenchymal stem cells (mBMSCs) on SAMs-COOH, SAMs-NH₂, and SAMs-PO₃H₂ with pre-adsorbed OPN showed promoted behaviour, in terms of spreading, viability, and the expression levels of α_v and β₃ genes, compared with the other two SAMs, demonstrating the higher bioactivity of the adsorbed OPN. We believe that our findings will have great potential for developing OPN-activated biomaterials.

Osteopontin (OPN) is an important protein for mediating cell behaviour on biomaterials.

Direct photoreactive immobilization of water-soluble phospholipid polymers on substrates in an aqueous environment

The purpose of this study is to achieve a simpler and safer surface modification of substrates using a photoreactive polymer in an aqueous environment. We synthesized water-soluble photoreactive polymers with both phenylazide groups and phosphorylcholine groups, poly(2-methacryloyloxyethyl phosphorylcholine-co-4-methacryl tetra(ethylene glycol)oxycarbonyl-4-phenylazide) (PMEPAz), via reversible addition fragmentation chain transfer polymerization. PMEPAz with different polymerization degrees were synthesized with a well-defined structure. To immobilize PMEPAz on the substrate surface by photoreaction, it is necessary to adsorb the polymer on the substrate surface in an aqueous solution because the phenylazide groups chemically bind to the substrate via a hydrogen abstract reaction. The relationship between the polymer solubilization state in the aqueous solution and the adsorption behavior at the surface was investigated. PMEPAz began to form unstable molecular aggregates at a concentration of 10^-2 mg/mL and formed stable aggregates at 10⁰ mg/mL. At a concentration of 10^-1 mg/mL, unstable molecular aggregates of PMEPAz were formed in the aqueous solution, resulting in the maximization of the amount of adsorbed polymer and effective photoreaction with the substrate. The thickness of the reacted polymer layer on the substrate increased with an increase in the polymerization degree, a uniform polymer layer with a thickness of 3.4 nm was formed when the polymerization degree was 400. After surface modification, the hydrophobic surfaces of the original substrates became hydrophilic. Additionally, fibrinogen adsorption and platelet adhesion were effectively suppressed based on the characteristics of the phosphorylcholine unit.

CaproGlu: Multifunctional tissue adhesive platform

Driven by the clinical need for a strong tissue adhesive with elastomeric material properties, a departure from legacy crosslinking chemistries was sought as a multipurpose platform for tissue mending. A fresh approach to bonding wet substrates has yielded a synthetic biomaterial that overcomes the drawbacks of free-radical and nature-inspired bioadhesives. A food-grade liquid polycaprolactone grafted with carbene precursors yields CaproGlu. The first-of-its-kind low-viscosity prepolymer is VOC-free and requires no photoinitiators. Grafted diazirine end-groups form carbene diradicals upon low energy UVA (365 nm) activation that immediately crosslink tissue surfaces; no pre-heating or animal-derived components are required. The hydrophobic polymeric environment enables metastable functional groups not possible in formulations requiring solvents or water. Activated diazirine within CaproGlu is uniquely capable of crosslinking all amino acids, even on wet tissue substrates. CaproGlu undergoes rapid liquid-to-biorubber transition within seconds of UVA exposure-features not found in any other bioadhesive. The exceptional shelf stability of CaproGlu allows gamma sterilization with no change in material properties. CaproGlu wet adhesiveness is challenged against current unmet clinical needs: anastomosis of spliced blood vessels, anesthetic muscle patches, and human platelet-mediating coatings. The versatility of CaproGlu enables both organic and inorganic composites for future bioadhesive platforms.

Development of a Nonwoven Hemostatic Dressing Based on Unbleached Cotton: A De Novo Design Approach

Minimally processed greige (unbleached) cotton fibers demonstrate enhanced clotting relative to highly processed United States Pharmacopeia (USP) type 7 bleached cotton gauze. This effect is thought to be due to the material surface polarity. We hypothesized that a textile could be constructed, conserving the hemostasis-accelerating properties of greige cotton, while maintaining structural integrity and improving absorbance. Spun bond nonwovens of varying surface polarity were designed and prepared based on ratios of greige cotton/bleached cotton/polypropylene fibers. A thromboelastographic analysis was performed on fibrous samples in citrated blood to evaluate the rate of fibrin and clot formation. Lee White clotting times were obtained to assess the material’s clotting activity in platelet fresh blood. An electrokinetic analysis of samples was performed to analyze for material surface polarity. Hemostatic properties varied with composition ratios, fiber density, and fabric fenestration. The determinations of the surface polarity of cotton fabrics with electrokinetic analysis uncovered a range of surface polarities implicated in fabric-initiated clotting; a three-point design approach was employed with the combined use of thromboelastography, thrombin velocity index, Lee White clotting, and absorption capacity determinations applied to fabric structure versus function analysis. The resulting analysis demonstrates that greige cotton may be utilized, along with hydrophilic and hydrophobic fibers, to improve the initiation of fibrin formation and a decrease in clotting time in hemostatic dressings suitable to be commercially developed. Hydroentanglement is an efficient and effective process for imparting structural integrity to cotton-based textiles, while conserving hemostatic function.

Zwitterionic carboxybetaine polymers extend the shelf-life of human platelets

The shelf-life of human platelets preserved in vitro for therapeutic transfusion is limited because of bacterial contamination and platelet storage lesion (PSL). The PSL is the predominant factor and limiting unfavorable interactions between the platelets and the non-biocompatible storage bag surfaces is the key to alleviate PSL. Here we describe a surface modification method for biocompatible platelet storage bags that dramatically extends platelet shelf-life beyond the current US Food and Drug Administration (FDA) standards of 5 days. The surface coating of the bags can be achieved through a simple yet effective dip-coating and light-irradiation method using a biocompatible polymer. The biocompatible polymers with tunable functional groups can be routinely fabricated at any scale and impart super-hydrophilicity and non-fouling capability on commercial hydrophobic platelet storage bags. As critical parameters reflecting the platelets quality, the activation level and binding affinity with von Willebrand factor (VWF) of the platelets stored in the biocompatible platelet bags at 8 days are comparable with those in the commercial bags at 5 days. This technique also demonstrates promise for a wide range of medical and engineering applications requiring biocompatible surfaces. STATEMENT OF SIGNIFICANCE: Current standard platelet preservation techniques agitate platelets at room temperature (20-24 °C) inside a hydrophobic (e.g., polyvinyl chloride (PVC)) storage bag, thereby allowing preservation of platelets only for 5 days. A key factor leading to quality loss is the unfavorable interaction between the platelets and the non-biocompatible storage bag surfaces. Here, a surface modification method for biocompatible platelet storage bags has been created to dramatically extend platelet shelf-life beyond the current FDA standards of 5 days. The surface coating of the bags can be achieved via a simple yet effective dip-coating and light-irradiation method using a carboxybetaine polymer. This technique is also applicable to many other applications requiring biocompatible surfaces.

Electrophoretic Deposition and Characterization of Functional Coatings Based on an Antibacterial Gallium (III)-Chitosan Complex

Despite their broad biomedical applications in orthopedics and dentistry, metallic implants are still associated with failures due to their lack of surface biofunctionality, leading to prosthesis-related microbial infections. In order to address this issue, the current study focuses on the fabrication and characterization of a novel type of antibacterial coating based on gallium (III)-chitosan (Ga (III)-CS) complex layers deposited on metallic substrates via electrophoretic deposition (EPD). Aiming for the production of homogeneous and monophasic coatings, a two step-procedure was applied: the first step involved the synthesis of the Ga (III)-CS complex, followed by EPD from suitable solutions in an acetic acid–aqueous solvent. The influence of Ga (III) concentration on the stability of the suspensions was evaluated in terms of zeta potential. Fourier transform infrared (FTIR) and energy dispersive X-ray (EDX) spectroscopic analyses indicated the chelation of CS with Ga (III) within the coatings, while scanning electron microscopy (SEM) confirmed that no additional metallic gallium deposited during EPD. Furthermore, the results demonstrated that the wettability, mechanical properties, swelling ability, and enzymatic degradation of the coatings were affected by the quantity of Ga (III) ions. Colony forming unit (CFU) tests showed a strong synergistic effect between CS and Ga (III) in inhibiting Escherichia coli strain growth compared to control CS samples. An in vitro study with MG-63 cells showed that Ga (III)-containing coatings were not toxic after 24 h of incubation.

Rolling or Two-Stage Aggregation of Platelets on the Surface of Thin Ceramic Coatings under in Vitro Simulated Blood Flow Conditions

The process of modern cardiovascular device fabrication should always be associated with an investigation of how surface properties modulate its hemocompatibility through plasma protein adsorption as well as blood morphotic element activation and adhesion. In this work, a package of novel assays was used to correlate the physicochemical properties of thin ceramic coatings with hemocompatibility under dynamic conditions. Different variants of carbon-based films were prepared on polymer substrates using the magnetron sputtering method. The microstructural, mechanical, and surface physicochemical tests were performed to characterize the coatings, followed by investigation of whole human blood quality changes under blood flow conditions using the "Impact R" test, tubes' tester, and radial flow chamber assay. The applied methodology allowed us to determine that aggregate formation on hydrophobic and hydrophilic carbon-based coatings may follow one of the two different mechanisms dependent on the type and conformational changes of adsorbed blood plasma proteins.

Nonadherent Zwitterionic Composite Nanofibrous Membrane with a Halloysite Nanocarrier for Sustained Wound Anti-Infection and Cutaneous Regeneration

Wound dressing synechia and sustained postoperative bacterial infection would cause serious secondary damage to nascent cutaneous tissue and impede normal regeneration of injured wound. Endowing wound dressings with nonadherent capability and long-lasting antibacterial property could optimize the postoperative wound healing conditions and promote wound tissue neogenesis, which have important clinical application value and demand. In this study, novel nanocarrier-embedded zwitterionic composite nanofibrous membranes are fabricated using the co-electrospinning/photo-cross-linking method for the purpose of painless removal and eliminating long-lasting antibacterial infection during postoperative wound therapy. The prepared membranes possess good biocompatibility, excellent antibiofouling ability against both bacteria and plasma proteins, and platelet and L929 cell adhesion. Furthermore, in vitro and in vivo antibacterial evaluations exhibit that the composite nanofibrous membranes with a sustained drug release profile could effectively inhibit bacterial proliferation for at least 16 days. Additionally, in vivo wound regeneration assessment indicates that the obtained membranes could better enhance skin regeneration than the commercial 3M Tegaderm film, which highlights the application prospect of such novel zwitterionic composite nanofibrous membranes for sustained postoperative wound anti-infection and cutaneous regeneration.

The blood compatibility challenge. Part 4: Surface modification for hemocompatible materials: Passive and active approaches to guide blood-material interactions

Biomedical devices in the blood flow disturb the fine-tuned balance of pro- and anti-coagulant factors in blood and vessel wall. Numerous technologies have been suggested to reduce coagulant and inflammatory responses of the body towards the device material, ranging from camouflage effects to permanent activity and further to a responsive interaction with the host systems. However, not all types of modification are suitable for all types of medical products. This review has a focus on application-oriented considerations of hemocompatible surface fittings. Thus, passive versus bioactive modifications are discussed along with the control of protein adsorption, stability of the immobilization, and the type of bioactive substance, biological or synthetic. Further considerations are related to the target system, whether enzymes or cells should be addressed in arterial or venous system, or whether the blood vessel wall is addressed. Recent developments like feedback controlled or self-renewing systems for drug release or addressing cellular regulation pathways of blood platelets and endothelial cells are paradigms for a generation of blood contacting devices, which are hemocompatible by cooperation with the host system. STATEMENT OF SIGNIFICANCE: This paper is part 4 of a series of 4 reviews discussing the problem of biomaterial associated thrombogenicity. The objective was to highlight features of broad agreement and provide commentary on those aspects of the problem that were subject to dispute. We hope that future investigators will update these reviews as new scholarship resolves the uncertainties of today.

Peri-procedural thrombocytopenia after aortic bioprosthesis implant: A systematic review and meta-analysis comparison among conventional, stentless, rapid-deployment, and transcatheter valves

BACKGROUND

Thrombocytopenia has been shown to occur soon after surgical biological aortic valve replacement (AVR), and recently reported also after transcatheter valve implantation (TAVI). The mechanism underlying this phenomenon is still unknown, and its clinical impact on the peri-operative outcome has been poorly investigated.

METHODS

A systematic review and a meta-analysis of all available studies reporting data about peri-procedural thrombocytopenia on isolated bio-AVR, comparing rapid-deployment (RDV), stentless (stentless-AVR), and TAVI vs. stented (stented-AVR) valves, have been performed.

RESULTS

Fifteen trials (2.163 patients) were included in the meta-analysis. Perioperative platelet reduction ranged from 35% to 55% in stented-AVR, from 60% to 77% in stentless-AVR, from 53% to 60% in RDV, and from to 21% to 72% in TAVI (apparently, balloon-expandable valves more frequently associated to thrombocytopenia). Stented-AVR required more red blood cells transfusion than stentless-AVR (P < 0.0001), whereas no difference has been found between RDV and stented-AVR. Platelet transfusion rate was very low in all surgical groups. No difference has been found in RDV and stentless-AVR vs. stented-AVR, in terms of reoperation for bleeding, and length-of-intensive care unit or hospital stay.

CONCLUSIONS

Thrombocytopenia-related major adverse events were mainly reported in TAVI patients, whereas clinically meaningless in surgical patients. Transient peri-procedural thrombocytopenia is common after bio-AVR, regardless of prosthesis's type or implant modality. It should receive appropriate monitoring and focused investigations.

Persulfated flavonoids accelerated re-endothelialization and improved blood compatibility for vascular medical implants

Drug-eluting stents (DESs) have been used for the treatment of cardiovascular diseases including stenosis. However, in-stent restenosis, thrombosis, and delayed re-endothelialization represent challenges for their clinical applications. Here, we demonstrate a novel work to overcome these limitations through surface modification technology. The cobalt-chromium (Co-Cr) surface was modified with antioxidants such as gallic acid (GA) and rutin (Ru) and the corresponding persulfates derivatives (i.e., GAS, and RuS) through a simple conjugation procedure. Various analyses tools such as ATR-FTIR, XPS, water contact angle, SEM, and AFM characterized the functionalized surface. The surface characterization confirmed that the antioxidant and the additional persulfates were successfully bonded to the Co-Cr surface. The results of in vitro endothelial cells proved that the persulfates derivatives showed the highest tendency to get rapid re-endothelialization especially RuS. In addition, it showed inhibition to smooth muscle cells (SMCs) as compared to control Co-Cr substrate. The persulfates modified substrates reduced the amount of adsorbed fibrinogen and albumin with higher stability to fetal bovine serum. Moreover, platelet study also demonstrated that Ru and RuS presented lower platelet adhesion with round shape morphology, whereas the control Co-Cr adhere and activate many platelets with pseudopodium morphology. Moreover, these modification processes did not cause any inflammatory responses. In conclusion, it is believed that the persulfates flavonoids have a great potential in the field of drug-eluting stents and blood contacting medical implants to improve blood compatibility, suppress SMCs, and get rapid re-endothelialization.

Broad-Spectrum Anti-Adhesive Coating Based on an Extracellular Polymer from a Marine Cyanobacterium

Medical device-associated infections are a major health threat, representing about half of all hospital-acquired infections. Current strategies to prevent this problem based on device coatings with antimicrobial compounds (antibiotics or antiseptics) have proven to be insufficient, often toxic, and even promoting bacterial resistance. Herein, we report the development of an infection-preventive coating (CyanoCoating) produced with an extracellular polymer released by the marine cyanobacterium Cyanothece sp. CCY 0110. CyanoCoating was prepared by spin-coating and its bacterial anti-adhesive efficiency was evaluated against relevant etiological agents (Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa and Escherichia coli) and platelets, both in the presence or absence of human plasma proteins. CyanoCoating cytotoxicity was assessed using the L929 fibroblasts cell line. CyanoCoating exhibited a smooth topography, low thickness and high hydrophilic properties with mild negative charge. The non-cytotoxic CyanoCoating prevented adhesion of all the bacteria tested (≤80%) and platelets (<87%), without inducing platelet activation (even in the presence of plasma proteins). The significant reduction in protein adsorption (<77%) confirmed its anti-adhesive properties. The development of this anti-adhesive coating is an important step towards the establishment of a new technological platform capable of preventing medical device-associated infections, without inducing thrombus formation in blood-contacting applications.

Biocompatibility of Plasma-Treated Polymeric Implants

Cardiovascular diseases are one of the main causes of mortality in the modern world. Scientist all around the world are trying to improve medical treatment, but the success of the treatment significantly depends on the stage of disease progression. In the last phase of disease, the treatment is possible only by implantation of artificial graft. Most commonly used materials for artificial grafts are polymer materials. Despite different industrial procedures for graft fabrication, their properties are still not optimal. Grafts with small diameters (<6 mm) are the most problematic, because the platelets are more likely to re-adhere. This causes thrombus formation. Recent findings indicate that platelet adhesion is primarily influenced by blood plasma proteins that adsorb to the surface immediately after contact of a synthetic material with blood. Fibrinogen is a key blood protein responsible for the mechanisms of activation, adhesion and aggregation of platelets. Plasma treatment is considered as one of the promising methods for improving hemocompatibility of synthetic materials. Another method is endothelialization of materials with Human Umbilical Vein Endothelial cells, thus forming a uniform layer of endothelial cells on the surface. Extensive literature review led to the conclusion that in this area, despite numerous studies there are no available standardized methods for testing the hemocompatibility of biomaterials. In this review paper, the most promising methods to gain biocompatibility of synthetic materials are reported; several hypotheses to explain the improvement in hemocompatibility of plasma treated polymer surfaces are proposed.