Multifunctional Coating Based on Hyaluronic Acid and Dopamine Conjugate for Potential Application on Surface Modification of Cardiovascular Implanted Devices

Facile Fabrication of Multifunctional Hydrogel Nanoweb Coating Using Carboxymethyl Chitosan-Based Short Nanofibers for Blood-Contacting Medical Devices

Blood-contacting medical devices (BCDs) require antithrombotic, antibacterial, and low-friction surfaces. Incorporating a nanostructured surface with the functional hydrogel onto BCD surfaces can enhance the performances; however, their fabrication remains challenging. Here, we introduce a straightforward method to fabricate a multifunctional hydrogel-based nanostructure on BCD surfaces using O-carboxymethyl chitosan-based short nanofibers (CMC-SNFs). CMC-SNFs, fabricated via electrospinning and cutting processes, are easily sprayed and entangled onto the BCD surface. The deposited CMC-SNFs form a robust nanoweb layer via fusion at the contact area of the nanofiber interfaces. The superhydrophilic CMS-SNF nanoweb surface creates a water-bound layer that effectively prevents the nonspecific adhesion of bacteria and blood cells, thereby enhancing both antimicrobial and antithrombotic performances. Furthermore, the CMC-SNF nanoweb exhibits excellent lubricity and durability on the bovine aorta. The demonstration results of the CMC-SNF coating on catheters and sheaths provide evidence of its capability to apply multifunctional surfaces simply for diverse BCDs.

A graft-to strategy of poly(vinylphosphonates) on dopazide-coated gold nanoparticles using in situ catalyst activation

A modular synthetic pathway for poly(diethyl vinylphosphonates) grafting-to gold nanoparticles is presented. Utilising an azide-dopamine derivative as nanoparticle coating agent, alkyne-azide click conditions were used to covalently tether the polymer to gold nanoparticles leading to stable and well distributed colloids for different applications.

Coatings for Cardiovascular Stents-An Up-to-Date Review

Cardiovascular diseases (CVDs) increasingly burden health systems and patients worldwide, necessitating the improved awareness of current treatment possibilities and the development of more efficient therapeutic strategies. When plaque deposits narrow the arteries, the standard of care implies the insertion of a stent at the lesion site. The most promising development in cardiovascular stents has been the release of medications from these stents. However, the use of drug-eluting stents (DESs) is still challenged by in-stent restenosis occurrence. DESs' long-term clinical success depends on several parameters, including the degradability of the polymers, drug release profiles, stent platforms, coating polymers, and the metals and their alloys that are employed as metal frames in the stents. Thus, it is critical to investigate new approaches to optimize the most suitable DESs to solve problems with the inflammatory response, delayed endothelialization, and sub-acute stent thrombosis. As certain advancements have been reported in the literature, this review aims to present the latest updates in the coatings field for cardiovascular stents. Specifically, there are described various organic (e.g., synthetic and natural polymer-based coatings, stents coated directly with drugs, and coatings containing endothelial cells) and inorganic (e.g., metallic and nonmetallic materials) stent coating options, aiming to create an updated framework that would serve as an inception point for future research.

Glycocalyx-inspired dynamic antifouling surfaces for temporary intravascular devices

Protein and cell adhesion on temporary intravascular devices can lead to thrombosis and tissue embedment, significantly increasing complications and device retrieval difficulties. Here, we propose an endothelial glycocalyx-inspired dynamic antifouling surface strategy for indwelling catheters and retrievable vascular filters to prevent thrombosis and suppress intimal embedment. This strategy is realized on the surfaces of substrates by the intensely dense grafting of hydrolyzable endothelial polysaccharide hyaluronic acid (HA), assisted by an amine-rich phenol-polyamine universal platform. The resultant super-hydrophilic surface exhibits potent antifouling property against proteins and cells. Additionally, the HA hydrolysis induces continuous degradation of the coating, enabling removal of inevitable biofouling on the surface. Moreover, the dense grafting of HA also ensures the medium-term effectiveness of this dynamic antifouling surface. The coated catheters maintain a superior anti-thrombosis capacity in ex vivo blood circulation after 30 days immersion. In the abdominal veins of rats, the coated implants show inhibitory effects on intimal embedment up to 2 months. Overall, we envision that this glycocalyx-inspired dynamic antifouling surface strategy could be a promising surface engineering technology for temporary intravascular devices.

Polydopamine (PDA) coatings with endothelial vascular growth factor (VEGF) immobilization inhibiting neointimal formation post zinc (zn) wire implantation in rat aortas

BACKGROUND

Bioresorbable stents are designed to provide temporary mechanical support to the coronary arteries and then slowly degrade in vivo to avoid chronic inflammation. Zinc (Zn) is a promising material for bioresorbable stents; However, it can cause inflammation and neointimal formation after being implanted into blood vessels.

METHODS

To improve biocompatibility of Zn, we first coated it with polydopamine (PDA), followed by immobilization of endothelial vascular growth factor (VEGF) onto the PDA coatings. Adhesion, proliferation, and phenotype maintenance of endothelial cells (ECs) on the coated Zn were evaluated in vitro. Then, a wire aortic implantation model in rats mimicking endovascular stent implantation in humans was used to assess vascular responses to the coated Zn wires in vivo. Thrombosis in aortas post Zn wire implantation, degradation of Zn wires in vivo, neointimal formation surrounding Zn wires, and macrophage infiltration and extracellular matrix (ECM) remodeling in the neointimas were examined.

RESULTS

In vitro data showed that the PDA-coated Zn encouraged EC adhesion, spreading, proliferation, and phenotype maintenance on its surfaces. VEGF functionalization on PDA coatings further enhanced the biocompatibility of Zn to ECs. Implantation of PDA-coated Zn wires into rat aortas didn't cause thrombosis and showed a faster blood flow than pure Zn or the Zn wires coated with VEGF alone. In addition, the PDA coating didn't affect the degradation of Zn wires in vivo. Besides, the PDA-coated Zn wires reduced neointimal formation, increased EC coverage, decreased macrophage infiltration, and declined aggrecan accumulation in ECM. VEGF immobilization onto PDA coatings didn't cause thrombosis and affect Zn degradation in vivo as well, and further increased the endothelization percentage as compared to PDA coating alone, thus resulting in thinner neointimas.

CONCLUSION

These results indicate that PDA coatings with VEGF immobilization would be a promising approach to functionalize Zn surfaces to increase biocompatibility, reduce inflammation, and inhibit neointimal formation after Zn implantation in vivo.

Oral Delivery of Protein Drugs via Lysine Polymer-Based Nanoparticle Platforms

Oral delivery of proteins has opened a new perspective for the treatment of different diseases. However, advances of oral protein formulation are usually hindered by protein susceptibility and suboptimal absorption in the gastrointestinal tract (GIT). Polymeric nano drug delivery systems are considered revolutionary candidates to solve these issues, which can be preferably tunable against specific delivery challenges. Herein, a tailored family of lysine-based poly(ester amide)s (Lys-aaPEAs) is designed as a general oral protein delivery platform for efficient protein loading and protection from degradation. Insulin, as a model protein, can achieve effective internalization by epithelial cells and efficient transport across the intestinal epithelium layer into the systemic circulation, followed by controlled release in physiological environments. After the oral administration of insulin carried by Lys-aaPEAs with ornamental hyaluronic acid (HA), mice with type 1 diabetes mellitus showed an acceptable hypoglycemic effect with alleviated complications. A successful oral insulin delivery is associated with patient comfort and convenience and simultaneously avoids the risk of hypoglycemia compared with injections, which is of great feasibility for daily diabetes therapy. More importantly, this versatile Lys-aaPEAs polymeric library can be recognized as a universal vehicle for oral biomacromolecule delivery, providing more possibilities for treating various diseases.

Functional liquid-infused PDMS sponge-based catheter with antithrombosis, antibacteria, and anti-inflammatory properties

A functional liquid-infused catheter surface strategy has recently attracted increasing attention for blood transport with the remarkable antibiofouling performance. Nevertheless, constructing porous structure inside a catheter with effective functional liquid-locking ability remains extremely challenging. Herein, the central cylinder mold and sodium chloride particle templates technique was used to create a PDMS sponge-based catheter that stores a stable functional liquid. Our multifunctional liquid-infused PDMS sponge-based catheter can not only exhibit bacterial resistant, less macrophages infiltration, a slighter inflammation response, but also capability to prevent platelet adhesion and activation, and impressively reduce thrombosis in vivo even at high shear. Therefore, these desirable properties will endow the prospective practical applications and serve as a watershed moment in the development of biomedical devices.

A Conductive Hydrogel Microneedle-Based Assay Integrating PEDOT:PSS and Ag-Pt Nanoparticles for Real-Time, Enzyme-Less, and Electrochemical Sensing of Glucose

Continuous glucose meters (CGMs) have tremendously boosted diabetes care by emancipating millions of diabetic patients' need for repeated self-testing by pricking their fingers every few hours. However, CGMs still suffer from major deficiencies regarding accuracy, precision, and stability. This is mainly due to their dependency on an enzymatic detection mechanism. Here a low-cost hydrogel microneedle (HMN)-CGM assay fabricated using swellable dopamine (DA)-hyaluronic acid (HA) hydrogel for glucose interrogation in dermal interstitial fluid (ISF) is introduced. Platinum and silver nanoparticles are synthesized within the 3D porous hydrogel scaffolds for nonenzymatic electrochemical sensing of the glucose. Incorporation of a highly water dispersible conductive polymer, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) enhances the electrical properties of HMN array, making the patch suitable as the working electrode of the sensor. The in vitro and ex vivo characterization of this newly developed HMN patch is fully studied. The performance of the HMN-CGM for real-time measurement of glucose is also shown using a rat model of type 1 diabetes. The device introduces the first HMN-based assay for tracking important disease biomarkers and expect to pave the way for next generation of polymeric-based sensors.

Dual-catalytic CuTPP/TiO2 nanoparticles for surface catalysis engineering of cardiovascular materials

Endowing materials with catalytic activities analogous to those of the natural endothelium to thus enhance their biological performance has become an option for constructing advanced blood-contact materials. The electron transfer between Cu2+ and Cu+ in the porphyrin center can catalyze the reaction of GSH and GSNO to generate NO, and this electron transfer can also catalyze the decomposition of ROS. Based on this, we created a dual-catalytic surface possessing NO-generating and ROS-scavenging activities to better mimic the versatile catalytic abilities of the endothelium. Copper tetraphenylporphyrin/titanium dioxide nanoparticles (CuTPP/TiO2-NPs) exhibiting excellent NO-generating and ROS-scavenging activities were synthesized and immobilized on the material surface to form a dual-catalytic film (CuTPP/TiO2-film) with the help of the catechol chemistry technique. Unlike most single catalytic surfaces, the dual-catalytic CuTPP/TiO2-film effectively regulated the microenvironment surrounding the implanted device by releasing NO signaling molecules and scavenging harmful ROS. This dual-catalytic film exhibited excellent biosafety and biocompatibility with anti-thrombosis, vascular wall cells (ECs and SMCs) modulation, and anti-inflammatory properties. We envision that this dual-catalytic endothelial bionic strategy may provide a promising solution to the clinical problems plaguing blood-contact devices and provide a novel basis for the further development of surface catalytic-engineered biomaterials.

Extracellular Matrix Coatings on Cardiovascular Materials—A Review

Vascular transplantation is an effective and common treatment for cardiovascular disease (CVD). However, the low biocompatibility of implants is a major problem that hinders its clinical application. Surface modification of implants with extracellular matrix (ECM) coatings is an effective approach to improve the biocompatibility of cardiovascular materials. The complete ECM seems to have better biocompatibility, which may give cardiovascular biomaterials a more functional surface. The use of one or several ECM proteins to construct a surface allows customization of coating composition and structure, possibly resulting in some unique functions. ECM is a complex three-dimensional structure composed of a variety of functional biological macromolecules, and changes in the composition will directly affect the function of the coating. Therefore, understanding the chemical composition of the ECM and its interaction with cells is beneficial to provide new approaches for coating surface modification. This article reviews novel ECM coatings, including coatings composed of intact ECM and biomimetic coatings tailored from several ECM proteins, and introduces new advances in coating fabrication. These ECM coatings are effective in improving the biocompatibility of vascular grafts.

Advances in Hyaluronic Acid for Biomedical Applications

Hyaluronic acid (HA) is a large non-sulfated glycosaminoglycan that is the main component of the extracellular matrix (ECM). Because of its strong and diversified functions applied in broad fields, HA has been widely studied and reported previously. The molecular properties of HA and its derivatives, including a wide range of molecular weights but distinct effects on cells, moisture retention and anti-aging, and CD44 targeting, promised its role as a popular participant in tissue engineering, wound healing, cancer treatment, ophthalmology, and cosmetics. In recent years, HA and its derivatives have played an increasingly important role in the aforementioned biomedical fields in the formulation of coatings, nanoparticles, and hydrogels. This article highlights recent efforts in converting HA to smart formulation, such as multifunctional coatings, targeted nanoparticles, or injectable hydrogels, which are used in advanced biomedical application.

Dopamine-conjugated hyaluronic acid delivered via intra-articular injection provides articular cartilage lubrication and protection

Due to its high molecular weight and viscosity, hyaluronic acid (HA) is widely used for viscosupplementation to provide joint pain relief in osteoarthritis. However, this benefit is temporary due to poor adhesion of HA on articular surfaces. In this study, we therefore conjugated HA with dopamine to form HADN, which made the HA adhesive while retaining its viscosity enhancement capacity. We hypothesized that HADN could enhance cartilage lubrication through adsorption onto the exposed collagen type II network and repair the lamina splendens. HADN was synthesized by carbodiimide chemistry between hyaluronic acid and dopamine. Analysis of Magnetic Resonance (NMR) and Ultraviolet spectrophotometry (Uv-vis) showed that HADN was successfully synthesized. Adsorption of HADN on collagen was demonstrated using Quartz crystal microbalance with dissipation (QCM-D). Ex vivo tribological tests including measurement of coefficient of friction (COF), dynamic creep, in stance (40 N) and swing (4 N) phases of gait cycle indicated adequate protection of cartilage by HADN with higher lubrication compared to HA alone. HADN solution at the cartilage-glass sliding interface not only retains the same viscosity as HA and provides fluid film lubrication, but also ensures better boundary lubrication through adsorption. To confirm the cartilage surface protection of HADN, we visualized cartilage wear using optical coherence tomography (OCT) and atomic force microscopy (AFM).

Tailoring ZE21B Alloy with Nature-Inspired Extracellular Matrix Secreted by Micro-Patterned Smooth Muscle Cells and Endothelial Cells to Promote Surface Biocompatibility

Delayed surface endothelialization is a bottleneck that restricts the further application of cardiovascular stents. It has been reported that the nature-inspired extracellular matrix (ECM) secreted by the hyaluronic acid (HA) micro-patterned smooth muscle cells (SMC) and endothelial cells (EC) can significantly promote surface endothelialization. However, this ECM coating obtained by decellularized method (dECM) is difficult to obtain directly on the surface of degradable magnesium (Mg) alloy. In this study, the method of obtaining bionic dECM by micro-patterning SMC/EC was further improved, and the nature-inspired ECM was prepared onto the Mg-Zn-Y-Nd (ZE21B) alloy surface by self-assembly. The results showed that the ECM coating not only improved surface endothelialization of ZE21B alloy, but also presented better blood compatibility, anti-hyperplasia, and anti-inflammation functions. The innovation and significance of the study is to overcome the disadvantage of traditional dECM coating and further expand the application of dECM coating to the surface of degradable materials and materials with different shapes.

Platelet-Derived Growth Factor-Functionalized Scaffolds for the Recruitment of Synovial Mesenchymal Stem Cells for Osteochondral Repair

Cartilage regeneration is still a challenge for clinicians because of avascularity, denervation, load-bearing, synovial movement, and the paucity of endogenous repair cells. We constructed a multilayered osteochondral bionic scaffold and examined its repair capacity using a rabbit osteochondral defect model. The cartilage phase and interface layer of the scaffold were prepared by freeze-drying, whereas the bone phase of the scaffold was prepared by high-temperature sintering. The three-phase osteochondral bionic scaffold was formed by joining the hydroxyapatite (HAp) and silk fibroin (SF) scaffolds using the repeated freeze-thaw method. Different groups of scaffolds were implanted into the rabbit osteochondral defect model, and their repair capacities were assessed using imaging and histological analyses. The cartilage phase and the interface layer of the scaffold had a pore size of 110.13 ± 29.38 and 96.53 ± 33.72 μm, respectively. All generated scaffolds exhibited a honeycomb porous structure. The polydopamine- (PDA-) modified scaffold released platelet-derived growth factor (PDGF) for 4 weeks continuously, reaching a cumulative release of 71.74 ± 5.38%. Synovial mesenchymal stem cells (SMSCs) adhered well to all scaffolds, but demonstrated the strongest proliferation ability in the HSPP (HAp-Silk-PDA-PDGF) group. Following scaffold-induced chondrogenic differentiation, SMSCs produced much chondrocyte extracellular matrix (ECM). In in vivo experiments, the HSPP group exhibited a significantly higher gross tissue morphology score and achieved cartilage regeneration at an earlier stage and a significantly better repair process compared with the other groups (P < 0.05). Histological analysis revealed that the new cartilage tissue in the experimental group had a better shape and almost filled the defect area, whereas the scaffold was nearly completely degraded. The new cartilage was effectively fused with the surrounding normal cartilage, and a substantial amount of chondrocyte ECM was formed. The SF/HAp three-layer osteochondral bionic scaffold exhibited favorable pore size, porosity, and drug sustained-release properties. It demonstrated good biocompatibility in vitro and encouraging repair effect at osteochondral defect site in vivo, thereby expected to enabling the repair and regeneration of osteochondral damage.

Multilayered mucoadhesive hydrogel films based on Ocimum basilicum seed mucilage/thiolated alginate/dopamine-modified hyaluronic acid and PDA coating for sublingual administration of nystatin

The present study establishes an experimental design for the preparation of new bi and tri-layer mucoadhesive sublingual films based on basil (Ocimum basilicum L.) seed mucilage (OBM) as novel plant-polysaccharide for oromucosal administration of nystatin (Nys). The films formulation consists of a drug reservoir-mucoadhesive layer cross-linked via CaCl₂, with protective mucoadhesive layers based on thiolated alginate (TA) and polydopamine (PDA). OBM served as a new mucoadhesive polysaccharide in second layers, where the dopamine-modified-hyaluronic acid (DHA) improved the mucoadhesive strength and swelling rate properties. The drug-loaded formulations of trilayer film with PDA coating, and bilayer film with DHA/OBM (1:1) in the second layer, showed the desired mucoadhesion properties (about 69 and 75.3% respectively). The obtained results revealed that the bilayer film containing DHA had a superior swelling degree in the range of 15-19 (g/g). While the PDA coating sample showed the highest resistance to water uptake and erosion. The bilayer film (DHA/OBM with 1:1 ratio) provided a maximum drug release of 86% after 4 h. The selected formulations indicated good mechanical properties with no cytotoxicity.

Immobilization of Glycogen Synthase Kinase-3β Inhibitor on 316L Stainless Steel via Polydopamine to Accelerate Endothelialization

The coverage of stents with healthy endothelium is crucial to the success of cardiovascular stent implantation. Immobilizing bioactive molecules on stents is an effective strategy to generate such stents. Glycogen synthase kinase-3β inhibitor (GSKi) is a bioactive molecule that can effectively accelerate vascular endothelialization. In this work, GSKi was covalently conjugated on 316L stainless steel through polydopamine to develop a stable bioactive surface. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and water contact angle results revealed the successful introduction of GSKi onto 316L stainless steel. The GSKi coating did not obviously affect the hemocompatibility of plates. The adhesion and proliferation of human coronary artery endothelial cells (HCAECs) on stainless steel was significantly promoted by the addition of GSKi. In summary, this work provides a universal and stable strategy of immobilizing GSKi on the stent surface. This method has the potential for widespread application in the modification of vascular stents.

Immune checkpoint programmed death-1 mediates abdominal aortic aneurysm and pseudoaneurysm progression

PURPOSE

The causes and pathogenetic mechanisms underlying abdominal aortic aneurysms (AAAs) and pseudoaneurysms are not fully understood. We hypothesized that inhibiting programmed death-1 (PD-1) can decrease AAA and pseudoaneurysm formation in mouse and rat models.

METHODS

Human AAA samples were examined in conjunction with an adventitial calcium chloride (CaCl2) application mouse model and an aortic patch angioplasty rat model. Single-dose PD-1 antibody (4 mg/kg) or BMS-1 (PD-1 inhibitor-1) (1 mg/kg) was administered by intraperitoneal (IP) or intraluminal injection. In the intramural injection group, PD-1 antibody was injected after CaCl2 incubation. The rats were divided into three groups: (1) the control group was only decellularized without other special treatment, (2) the PD-1 antibody-coated patch group, and (3) the BMS-1 coated patch group. Patches implanted in the rat abdominal aorta were harvested on day 14 after implantation and analyzed.

RESULTS

Immunohistochemical analysis showed PD-1-positive cells, PD-1 and CD3, PD-1 and CD68, and PD-1 and α-actin co-expressed in the human AAA samples. Intraperitoneal (IP) injection or intraluminal injection of PD-1antibody/BMS-1 significantly inhibited AAA progression. PD-1 antibody and BMS-1 were each successfully conjugated to decellularized rat thoracic artery patches, respectively, by hyaluronic acid. Patches coated with either humanized PD-1 antibody or BMS-1 can also inhibit pseudoaneurysm progression and inflammatory cell infiltration.

CONCLUSION

PD-1 pathway inhibition may be a promising therapeutic strategy for inhibiting AAA and pseudoaneurysm progression.

Development of biodegradable zein-based bilayer coatings for drug-eluting stents

Drug-eluting stents (DES) have been widely used for the treatment of cardiovascular diseases. Nevertheless, chronic inflammation and delayed re-endothelialization still represent challenges for their clinical use. In the present work, we developed novel bilayer coatings for stent applications that could overcome these limitations, exclusively using biodegradable plant-based drugs and polymers. In particular, stainless steel surfaces were coated with rutin-loaded zein (the active layer) and cross-linked alginate (the sacrificial layer) via facile dip and spray coating methods. Various mechanical tests and analysis tools, such as infrared spectroscopy, water contact angle measurements, and scanning electron microscopy were used to characterize the coated surfaces. Degradation and release studies of the films were extensively carried out and compared. The release rate of rutin from the bilayer coating reached 66.1 ± 3.2% within 24 hours of incubation (initial burst period), while the rest of the drug was released over 21 days in a sustained manner. Antioxidant assays confirmed that rutin retained its free radical scavenging ability after being eluted in phosphate buffer at 37 °C. In vitro results with human fibroblasts and endothelial cells suggested that the coating materials and their degradation products are highly biocompatible. In conclusion, our novel drug-eluting coatings, fabricated with natural biodegradable polymers, are promising materials for DES applications, allowing a sustained drug delivery and improving the biocompatibility of cardiovascular implanted devices.

Programmed death-1 mediates venous neointimal hyperplasia in humans and rats

Venous neointimal hyperplasia can be a problem after vein interventions. We hypothesized that inhibiting programmed death-1 (PD-1) can decrease venous neointimal hyperplasia in a rat inferior vena cava (IVC) patch venoplasty model. The rats were divided into four groups: the control group was only decellularized without other special treatment; the PD-1 group was injected with a single dose of humanized PD-1 antibody (4 mg/kg); the PD-1 antibody coated patches group; the BMS-1 (a PD-1 small molecular inhibitor) coated patches group (PD-1 inhibitor-1). Patches were implanted to the rat IVC and harvested on day 14 and analyzed. Immunohistochemical analysis showed PD-1-positive cells in the neointima in the human samples. There was high protein expression of PD-1 in the neointima in the rat IVC venoplasty model. PD-1 antibody injection can significantly decrease neointimal thickness (p < 0.0001). PD-1 antibody or BMS-1 was successfully conjugated to the decellularized rat thoracic artery patch by hyaluronic acid with altered morphology and reduced the water contact angle (WCA). Patches coated with humanized PD-1 antibody or BMS-1 both can also decrease neointimal hyperplasia and inflammatory cells infiltration. PD-1-positive cells are present in venous neointima in both human and rat samples. Inhibition of the PD-1 pathway may be a promising therapeutic strategy to inhibit venous neointimal hyperplasia.

Biocompatibility Evolves: Phenomenology to Toxicology to Regeneration

The word "biocompatibility," is inconsistent with the observations of healing for so-called biocompatible biomaterials. The vast majority of the millions of medical implants in humans today, presumably "biocompatible," are walled off by a dense, avascular, crosslinked collagen capsule, hardly suggestive of life or compatibility. In contrast, one is now seeing examples of implant biomaterials that lead to a vascularized reconstruction of localized tissue, a biological reaction different from traditional biocompatible materials that generate a foreign body capsule. Both the encapsulated biomaterials and the reconstructive biomaterials qualify as "biocompatible" by present day measurements of biocompatibility. Yet, this new generation of materials would seem to heal "compatibly" with the living organism, where older biomaterials are isolated from the living organism by the dense capsule. This review/perspective article will explore this biocompatibility etymological conundrum by reviewing the history of the concepts around biocompatibility, today's standard methods for assessing biocompatibility, a contemporary view of the foreign body reaction and finally, a compendium of new biomaterials that heal without the foreign body capsule. A new definition of biocompatibility is offered here to address advances in biomaterials design leading to biomaterials that heal into the body in a facile manner.

Endothelial Cell-Mediated Gene Delivery for In Situ Accelerated Endothelialization of a Vascular Graft

As an urgently needed device for vascular diseases, the small-diameter vascular graft is limited by high thrombogenicity in clinical applications. Rapid endothelialization is a promising approach to construct an antithrombogenic inner surface of the vascular graft. The main bottleneck for rapid endothelialization is the adhesion, migration, and proliferation of endothelial cells (ECs) in situ of the small-diameter vascular graft. Herein, we innovatively fabricated an intelligent gene delivery small-caliber vascular graft based on electrospun poly(lactic acid-co-caprolactone) and gelatin for rapid in situ endothelialization. The graft surface was co-modified with EC adhesive peptide of Arg-Glu-Asp-Val (REDV) and responsive gene delivery system. REDV can selectively adhere ECs onto the graft surface; subsequently, the overexpressed matrix metalloproteinase by ECs can effectively cleave the linker peptide GPQGIWGQ-C; and finally, the gene complexes were intelligently and enzymatically released from the graft surface, and thereby, the gene can efficiently transfect ECs. Importantly, this enzymatically releasing gene surface has been proven to be safe and temporarily stable in blood flow owing to the biotin-avidin interaction to immobilize gene complexes on the inner surface of vascular grafts through the GPQGIWGQ-C peptide linker. It has the advantage of specifically adhering the ECs to the surface and smartly transfecting them with high transfection efficiency. The co-modified surface has been demonstrated to accelerate the luminal endothelialization in vivo, which might be attributed to the synergistic effect of REDV and effective gene transfection. Particularly, the intelligent and responsive gene release surface will open a new avenue to enhance the endothelialization of blood-contacting devices.

Hyaluronic acid/polyethyleneimine nanoparticles loaded with copper ion and disulfiram for esophageal cancer

In the clinical treatment of cancer, improving the effectiveness and targeting of drugs has always been a bottleneck problem that needs to be solved. In this contribution, inspired by the targeted inhibition on cancer from combination application of disulfiram and divalent copper ion (Cu²⁺), we optimized the concentration of disulfiram and Cu²⁺ ion for inhibiting esophageal cancer cells, and loaded them in hyaluronic acid (HA)/polyethyleneimine (PEI) nanoparticles with specific scales, in order to improve the effectiveness and targeting of drugs. The in vitro cell experiments demonstrated that more drug loaded HA/PEI nanoparticles accumulated to the esophageal squamous cell carcinoma (Eca109) and promoted higher apoptosis ratio of Eca109. Both in vitro and in vivo biological assessment verified that the disulfiram/Cu²⁺ loaded HA/PEI nanoparticles promoted the apoptosis of cancer cells and inhibited the tumor proliferation, but had no toxicity on other normal organs.

Preparation of phospholipid-based polycarbonate urethanes for potential applications of blood-contacting implants

Polyurethanes are widely used in interventional devices due to the excellent physicochemical property. However, non-specific adhesion and severe inflammatory response of ordinary polyurethanes may lead to severe complications of intravenous devices. Herein, a novel phospholipid-based polycarbonate urethanes (PCUs) were developed via two-step solution polymerization by direct synthesis based on functional raw materials. Furthermore, PCUs were coated on biomedical metal sheets to construct biomimetic anti-fouling surface. The results of stress–strain curves exhibited excellent tensile properties of PCUs films. Differential scanning calorimetry results indicated that the microphase separation of such PCUs polymers could be well regulated by adjusting the formulation of chain extender, leading to different biological response. In vitro blood compatibility tests including bovine serum albumin adsorption, fibrinogen adsorption and denaturation, platelet adhesion and whole-blood experiment showed superior performance in inhibition non-specific adhesion of PCUs samples. Endothelial cells and smooth muscle cells culture tests further revealed a good anti-cell adhesion ability. Finally, animal experiments including ex vivo blood circulation and subcutaneous inflammation animal experiments indicated a strong ability in anti-thrombosis and histocompatibility. These results high light the strong anti-adhesion property of phospholipid-based PCUs films, which may be applied to the blood-contacting implants such as intravenous catheter or antithrombotic surface in the future.

Preparation, purification, and characterization of low-molecular-weight hyaluronic acid

OBJECTIVE

The use and commercial value of hyaluronic acid (HA) as an important element in the pharmaceutical, biomedical, and cosmetics industry is because of its purity. Four recombinant strains of Corynebacterium glutamicum containing different genes were used to produce HA.

RESULTS

The production parameters were measured and strain 183.2, with the highest amount of HA (2.15 mg/ml), was selected for further experiments. HA was precipitated by different ratios of ethanol-isopropanol at 4 °C and - 20 °C. Active charcoal (1%) was added to the solvent precipitation mixture at pH 5 and 10. Finally, to achieve more purity and separation, gel filtration chromatography was used. The best result was obtained using an ethanol-isopropanol ratio of 1:1 of at - 20 °C, followed by active charcoal treatment at the acidic pH, and three fractions of the chromatography with molecular weights of 27, 27-110, and < 27 KDa were more analyzed with electrophoresis and FTIR.

CONCLUSIONS

The present study described a simple, economical, and reproducible method resulting in a high yield for low-MW HA from C. glutamicum.

Mimicking the Nitric Oxide-Releasing and Glycocalyx Functions of Endothelium on Vascular Stent Surfaces

Endothelium can secrete vasoactive mediators and produce specific extracellular matrix, which contribute jointly to the thromboresistance and regulation of vascular cell behaviors. From a bionic point of view, introducing endothelium-like functions onto cardiovascular stents represents the most effective means to improve hemocompatibility and reduce late stent restenosis. However, current surface strategies for vascular stents still have limitations, like the lack of multifunctionality, especially the monotony in endothelial-mimic functions. Herein, a layer-by-layer grafting strategy to create endothelium-like dual-functional surface on cardiovascular scaffolds is reported. Typically, a nitric oxide (NO, vasoactive mediator)-generating compound and an endothelial polysaccharide matrix molecule hyaluronan (HA) are sequentially immobilized on allylamine-plasma-deposited stents through aqueous amidation. In this case, the stents could be well-engineered with dual endothelial functions capable of remote and close-range regulation of the vascular microenvironment. The synergy of NO and endothelial glycocalyx molecules leads to efficient antithrombosis, smooth muscle cell (SMC) inhibition, and perfect endothelial cell (EC)-compatibility of the stents in vitro. Moreover, the dual-functional stents show efficient antithrombogenesis ex vivo, rapid endothelialization, and long-term prevention of restenosis in vivo. Therefore, this study will provide new solutions for not only multicomponent surface functionalization but also the bioengineering of endothelium-mimic vascular scaffolds with improved clinical outcomes.

Sulfur Contents in Sulfonated Hyaluronic Acid Direct the Cardiovascular Cells Fate

Hyaluronic acid (HA) is recognized as a functional carbohydrate polymer applied for the surface modification of cardiovascular implanted materials due to its molecular weight (MW) dependent cellular regulation. However, due to the enzyme digestion of hyaluronidase on HA in vivo, the stability of HA MW needs to be further improved. It has been reported that the stability of HA MW can be improved by sulfonation. In this study, sulfonated hyaluronic acids (S-HA) with sulfur content of 2.06, 3.69, 7.10, 8.98, and 9.71 were prepared through different sulfuric acid treatment procedures. Cell tests showed that S-HA with higher sulfur content played a significant role in promoting the proliferation and migration of endothelial cells and regulating smooth muscle cells to the physiological phenotype. In addition, it was also proved to inhibit the inflammatory macrophages adhesion/activation. Our data indicates that S-HA may be a better carbohydrate polymer for potential application of cardiovascular biomaterials.

SiCxNyOz Coatings Enhance Endothelialization and Bactericidal activity and Reduce Blood Cell Activation

For biomedical applications, a number of ceramic coatings have been investigated, but the interactions with the components of living system remain unexplored for oxycarbonitride coatings. While addressing this aspect, the present study aims to provide an understanding of the biocompatibility of novel SiC_xN_yO_z coatings that could validate the hypothesis that such coatings may not only enhance the cell-material interaction by re-endothelialization but also can help to reduce bacterial adhesion and activation of blood cells. This work reports the physicochemical properties, hemocompatibility, endothelialization, and antibacterial properties of novel amorphous SiC_xN_yO_z coatings deposited on commercial pure titanium (Ti) by radiofrequency (RF) magnetron sputtering at varied nitrogen (N₂) flow rates. A comparison is made with diamond-like carbon (DLC) coatings, which are clinically used. The surface roughness, surface wettability, nanoscale hardness, and surface energy of SiC_xN_yO_z coatings were found to be dependent on the nitrogen (N₂) flow rate. Importantly, the as-deposited SiC_xN_yO_z coatings exhibited much better nanoscale hardness and scratch resistance than DLC coatings. Furthermore, Raman spectroscopy analysis of the SiC_xN_yO_z coating deposited on Ti showed a change in the graphitic/disordered carbon content. Cytocompatibility and hemocompatibility properties of the as-deposited SiC_xN_yO_z coating were evaluated using the Mus musculus lymphoid endothelial cell line (SVEC4-10) and rabbit blood in vitro. WST-1 assay analysis showed that these coatings, when compared to DLC, exhibited a better proliferation of endothelial cells, which can potentially result in improved surface endothelialization. Furthermore, qualitative and quantitative analyses of immunofluorescence images revealed a dense cellular layer of SVEC4-10 on SiC_xN_yO_z coatings, deposited at 15 and 30 sccm nitrogen flow rates. As far as compatibility with rabbit blood is concerned, the hemolysis of the SiC_xN_yO_z coatings was less than 4%, with slightly lower values for coatings deposited without N₂ flow. The SiC_xN_yO_z coatings support less platelet adhesion and aggregation, with no signature of morphological deformation, as compared to the uncoated titanium substrate or DLC coatings. Furthermore, SiC_xN_yO_z coatings were also found to be effectively extending the blood coagulation time for a period of 60 min. The antimicrobial study of as-deposited SiC_xN_yO_z coatings on E. coli and S. aureus bacteria revealed the effective inhibition of bacterial proliferation after 24 h of culture. An attempt has been made to explain the cyto- and hemocompatibility properties with antimicrobial efficacy of coatings in terms of the variation in the coating composition and surface energy. Taken together, we conclude that SiC_1.3N_0.76O_0.87 coating having a roughness of 17 nm and a surface free energy of 54.0 ± 0.7 mN/m can exhibit the best combination of hardness, elastic modulus, scratch resistance, cytocompatibility, hemocompatibility, and bactericidal properties.

Enhanced Biocompatibility and Differentiation Capacity of Mesenchymal Stem Cells on Poly(dimethylsiloxane) by Topographically Patterned Dopamine

Controlling the behavior of mesenchymal stem cells (MSCs) through topographic patterns is an effective approach for stem cell studies. We, herein, reported a facile method to create a dopamine (DA) pattern on poly(dimethylsiloxane) (PDMS). The topography of micropatterned DA was produced on PDMS after plasma treatment. The grid-topographic-patterned surface of PDMS-DA (PDMS-DA-P) was measured for adhesion force and Young's modulus by atomic force microscopy. The surface of PDMS-DA-P demonstrated less stiff and more elastic characteristics compared to either nonpatterned PDMS-DA or PDMS. The PDMS-DA-P evidently enhanced the differentiation of MSCs into various tissue cells, including nerve, vessel, bone, and fat. We further designed comprehensive experiments to investigate adhesion, proliferation, and differentiation of MSCs in response to PDMS-DA-P and showed that the DA-patterned surface had good biocompatibility and did not activate macrophages or platelets in vitro and had low foreign body reaction in vivo. Besides, it protected MSCs from apoptosis as well as excessive reactive oxygen species (ROS) generation. Particularly, the patterned surface enhanced the differentiation capacity of MSCs toward neural and endothelial cells. The stromal cell-derived factor-1α/CXantiCR4 pathway may be involved in mediating the self-recruitment and promoting the differentiation of MSCs. These findings support the potential application of PDMS-DA-P in either cell treatment or tissue repair.

Effect of the mechanical properties of carbon-based coatings on the mechanics of cell-material interactions

The paper presents an influence of the surface mechanical properties of thin-film materials on blood cell adhesion under shear stress conditions. Physical vapour deposited (PVD) coatings i.e. hydrogenated amorphous carbon (a-C:H) doped with nitrogen or silicon have been investigated. The mechanical properties of materials, namely their microhardness and Young's modulus were measured using indentation test with Rockwell indenter. The adhesion efficiency of blood cells in dynamic conditions were analysed using a radial flow chamber. Red blood cells (RBC) were used as representative cells to analyse cell-material interactions. The biomaterial examinations were performed under physiological flow conditions at the single-cell level. The 3D FVM (finite volume method) model of multi-phase radial flow test was developed to reproduce the physical test and to predict distributions of shear stresses and velocity during blood washout with PBS. Cell-material interactions were found to be strongly associated with the mechanical properties of the thin-film material. The decrease in the hardness of the coatings translated into a weaker cell - material interactions.

Surface Engineering of Cardiovascular Devices for Improved Hemocompatibility and Rapid Endothelialization

Cardiovascular devices have been widely applied in the clinical treatment of cardiovascular diseases. However, poor hemocompatibility and slow endothelialization on their surface still exist. Numerous surface engineering strategies have mainly sought to modify the device surface through physical, chemical, and biological approaches to improve surface hemocompatibility and endothelialization. The alteration of physical characteristics and pattern topographies brings some hopeful outcomes and plays a notable role in this respect. The chemical and biological approaches can provide potential signs of success in the endothelialization of vascular device surfaces. They usually involve therapeutic drugs, specific peptides, adhesive proteins, antibodies, growth factors and nitric oxide (NO) donors. The gene engineering can enhance the proliferation, growth, and migration of vascular cells, thus boosting the endothelialization. In this review, the surface engineering strategies are highlighted and summarized to improve hemocompatibility and rapid endothelialization on the cardiovascular devices. The potential outlook is also briefly discussed to help guide endothelialization strategies and inspire further innovations. It is hoped that this review can assist with the surface engineering of cardiovascular devices and promote future advancements in this emerging research field.

A Novel Nanoparticle Preparation to Enhance the Gastric Adhesion and Bioavailability of Xanthatin

OBJECTIVE

To prepare xanthatin (XA)-loaded polydopamine (PDA) nanoparticles (PDA-XA-NPs) and to investigate their adhesion and bioavailability.

MATERIALS AND METHODS

PDA-XA-NPs were synthesized and characterized using transmission electron microscopy, zeta potential analysis and encapsulation efficiency analysis. Their in vitro release kinetics and inhibitory effects on gastric cancer were studied. The adhesion of PDA-XA-NPs was evaluated by in vivo imaging atlas. The pharmacokinetics of PDA-XA-NPs and XA was compared.

RESULTS

PDA-XA-NPs had a spherical shape, a particle size of about 380 nm, an encapsulation efficiency of (82.1 ± 0.02) % and a drug loading capacity of (5.5 ± 0.1)%. The release of PDA-XA-NPs in PBS was stable and slow, without being affected by pH. The adhesion capacity of PDA-XA-NPs for mucin was significantly higher than that of bulk drug. The gastric mucosal retention of PDA-XA-NPs reached 89.1% which significantly exceeded that of XA. In vivo imaging showed that PDA-XA-NPs targeting the stomach were retained for a period of time. The pharmacokinetics study showed that PDA-XA-NPs had a longer retention time and a slower drug release than those of XA. In vitro experiments confirmed that PDA-XA-NPs exerted similar inhibitory effects on gastric cancer to those of XA, which lasted for a period of time.

CONCLUSION

High-adhesion NPs were constructed. Gastric cancer was targeted by orally administered PDA-XA-NPs, as a potentially feasible therapy. Eventually, the bioavailability of XA was increased.

Phospholipid-based multifunctional coating via layer-by-layer self-assembly for biomedical applications

As an important class of biomaterials，bionics inspired materials has been widely used in creating extracorporeal and implantable medical devices. However, specific service environment is often faced with multiple requirements rather than single function. Herein, we designed a phospholipid-based multifunctional coating with phospholipids-based polymers, type I collagen (Col-I) and Arg-Glu-Asp-Val (REDV) peptide, via layer-by-layer assembly. The successful synthesis of the polymers and the coating is proved by a series of characterization methods including Fourier transforming infrared spectra (FTIR), proton nuclear magnetic resonance (¹H NMR), ultraviolet-visible spectra (UV) and X-ray photoelectron spectroscopy (XPS), while the assembly process and quality change of the coating were monitored via quartz crystal microbalance (QCM). Besides, hydrophilicity and roughness of this coating was analyzed via water contact angle (WCA) and atomic force microscope (AFM), respectively. Finally, results from platelet adhesion, activation assay, smooth muscle cells (SMCs) and endothelial cells (ECs) cultures indicated that the multifunctional coating could strongly inhibit platelet adhesion and SMCs proliferation, hence provide practical application of the coating with good biocompatibility, especially the anticoagulant property and cell compatibility. It is expected that this coating may be used in blood-contacting fields such as cardiovascular stent or other devices in the future.

Benlysta-Loaded Sodium Alginate Hydrogel and Its Selective Functions in Promoting Skin Cell Growth and Inhibiting Inflammation

Benlysta is a new drug approved by the US Food and Drug Administration (US FDA) in 2019 for the treatment of systemic lupus erythematosus. In this study, we loaded the benlysta in the traditional sodium alginate (SA) hydrogel to investigate the potential application of the drug-loaded hydrogel for skin dressing or hypodermic drug. Live/dead staining images and the CCK-8 results showed that the benlysta-loaded hydrogel could promote the growth of human epidermal cells (HaCat), fibroblasts (L929), and endothelial cells while inhibiting the aggregation of inflammatory cells (macrophages). In addition, the hydrogel degradation and drug release are slow and controllable, and the gel time of drug-loaded hydrogel can be adjusted by adding sodium alginate ratios according to the requirement. In summary, we prepared a time-dependent drug-loaded hydrogel for potential application in the treatment of skin injury that may be caused by other diseases.

Preparing a novel magnesium-doped hyaluronan/polyethyleneimine nanoparticle to improve endothelial functionalisation

Nowadays, tissue engineering vascularisation has become an important means of organ repair and treatment of major traumatic diseases. Vascular endothelial layer regeneration and endothelial functionalisation are prerequisites and important components of tissue engineering vascularisation. The present researches of endothelial functionalisation mainly focus on tissue engineering scaffold preparation and implant surface modification. Few studies have reported the interaction of endothelial functionalisation and scaled materials, especially the nanomaterials. Magnesium (Mg), as an essential cytotropic active element in the human body, should promote the growth of endothelial cells. However, the authors' previous work found that the Mg in the alloys had a defect of delayed endothelialisation, which may be attributed to the non-uniform scales of the degradation products from Mg alloys. To validate this hypothesis and fabricate a novel nanomaterial for tissue engineering vascularisation, the authors prepared Mg-doped hyaluronan (HA)/polyethyleneimine (PEI) nanoparticles for endothelial cells testing. Their data showed that the Mg-doped HA/PEI nanoparticle with small scales (diameter <150 nm) presented better ability on improving endothelial cells growth, functionalisation and nitric oxide release.

Advances in biomolecule inspired polymeric material decorated interfaces for biological applications

With the development of surface modification technology, interface properties have great effects on the interaction between biomedical materials and cells and biomolecules, which significantly affects the biocompatibility and functionality of materials. As an orderly and perfect system, biological organisms in nature effectively integrate all kinds of bio-interfaces with physiological functions, which shed light on the importance of biomolecules in organisms. It gives birth to a bio-inspiration strategy to design and fabricate smart materials with specific functionalities, e.g. osteogenic and chondrocytic induced materials inspired by bone sialoprotein and chondroitin sulfate. Through this mimicking approach, various functional materials were utilized to decorate the interfaces and further optimize the performance of biomedical materials, which would widely expand their applications. In this review, followed by a summary and brief introduction of surface modification methods, we highlight recent advances in the fabrication of functional polymeric materials inspired by a range of biomolecules for decorating interfaces. Then, the other applications of biomolecule inspired materials including tissue engineering, diagnosis and treatment of diseases and physiological function regulation are presented and the future outlook is discussed as well.

Investigation of Mg-Zn-Y-Nd alloy for potential application of biodegradable esophageal stent material

In recent years, due to unhealthy dietary habits and other reasons, advanced esophageal cancer patients are on the rise, threatening human health and life safety at all times. Stents implantation as an important complementary or alternative method for chemotherapy has been widely applied in clinics. However, the adhesion and proliferation of pathological cells, such as tumor cells, fibroblasts and epithelial cells, may interfere the efficacy of stents. Further multiple implantation due to restenosis may also bring pain to patients. In this contribution, we preferred a biodegradable material Mg-Zn-Y-Nd alloy for potential application of esophageal stent. The hardness testing showed that Mg-Zn-Y-Nd alloy owned less mechanical properties compared with the commercial esophageal stents material, 317L stainless steel (317L SS), while Mg-Zn-Y-Nd displayed significantly better biodegradation than 317L SS. Cell apoptosis assay indicated Mg-Zn-Y-Nd inhibited adhesion and proliferation of tumor cells, fibroblasts and epithelial cells. Our research suggested potential application of Mg-Zn-Y-Nd alloy as a novel material for biodegradable esophageal stent.

An Injectable Nanocomposite Hydrogel for Potential Application of Vascularization and Tissue Repair

In this contribution, an injectable hydrogel was developed with chitosan, gelatin, β-glycerphosphate and Arg-Gly-Asp (RGD) peptide: this hydrogel is liquid in room temperature and rapidly gels at 37 °C; RGD peptide promises better growth microenvironment for various cells, especially endothelial cells (EC), smooth muscle cells (SMC) and mesenchymal stem cells (MSC). Both stromal cell-derived factor-1 (SDF-1) nanoparticle and vascular endothelial growth factor (VEGF) nanoparticles were loaded in the injectable hydrogel to simulate the natural nanoparticles in the extracellular matrix (ECM) to promote angiogenesis. In vitro EC/SMC and MSC/SMC co-culture experiment indicated that the nanocomposite hydrogel accelerated constructing embryonic form of blood vessels, and chick embryo chorioallantoic membrane model demonstrated its ability of improving cells migration and blood vessel regeneration. We injected this nanocomposite hydrogel into rat myocardial infarction (MI) model and the results indicated that the rats heart function recovered better compared control group. We hope this injectable nanocomposite hydrogel may possess wider application in tissue engineering.

Hyaluronic acid-heparin conjugated decellularized human great saphenous vein patches decrease neointimal thickness

Although the science of implantable materials has advanced therapeutic options in vascular surgery, graft failure is still a problem in need of a durable solution. With the development of coating and decellularization techniques, coated prosthetic grafts have become an option; however, whether decellularized human saphenous vein can be conjugated and implanted is not known. Human great saphenous vein (GSV) was harvested and decellularized and hyaluronic acid (HA)-heparin was conjugated to the GSV; water contact angles (WCA), morphology, and sulfur element change were measured before and after heparin bonding. GSV patches were implanted into the rat inferior vena cava and aorta; patches were harvested (Day 14) and analyzed. HA-heparin was successfully conjugated to the decellularized human GSV with altered morphology and reduced WCA. The HA-heparin coated decellularized GSV patch was anti-thrombotic in vitro, and significantly decreased neointimal thickness both in patch venoplasty and angioplasty in a rat model. Both CD90 and nestin positive cells participated in neointima formation. These data show that HA-heparin coated human GSV patches decrease neointimal thickness when used both in venoplasty and arterioplasty. Tissue engineered decellularized human GSV is a promising vascular prosthesis.

A multifunctional gelatine-quaternary ammonium copolymer: An efficient material for reducing dye emission in leather tanning process by superior anionic dye adsorption

Leather wastewater is one of the most polluting industrial emissions. The efficiency of wastewater remediation is limited by its complex composition. Herein, a novel strategy for designing modified gelatine with higher degree of quaternization (MG-2) is presented. The higher degree of quaternization allows sufficient adsorption of dyes in the tanning process. It is an in situ, environmentally friendly, and innovative strategy to limit dye emissions and can circumvent the subsequent waste management. Dyes such as Direct Purple N and Acid Black 24 could be adsorbed completely within 5 min by the MG-2 film formed from MG-2 solution. In addition, a remarkable efficiency in removing Acid Red 73, Golden Orange G, and Acid Orange II (>96.1% removal rates) was achieved within 30 min. The adsorption equilibrium data suggested that the adsorption capacity was positively correlated to the concentration of MG-2. When Acid Orange II and MG-2 were used in the industrial re-tanning process, the residual dye concentration in wastewater was only 23.1 mg L^-1, indicating that MG-2 is a promising re-tanning agent for adsorbing dyes in the leather tanning process.

Bioinspired, Artificial, Small-Diameter Vascular Grafts with Selective and Rapid Endothelialization Based on an Amniotic Membrane-Derived Hydrogel

Clinical application of the amniotic membrane (AM) in vascular reconstruction was limited by poor processability, rapid biodegradation, and insufficient hemocompatibility. In this work, decellularized AM was digested to a thermosensitive hydrogel and densely cross-linked in the nanoscale as "enhanced" collagenous fibers. Via N-(3-dimehylaminopropyl)-N'-ethylcarbodiimide and N-hydroxysuccinimide (EDC/NHS) catalysis, REDV was further grafted to simulate anticoagulant substances on naturally derived blood vessels. This modification approach endowed AM with rapid endothelialization and rare vascular restenosis. Through adjusting the fixation condition, the pore size and mechanical stability of the fiber network were approximate to those of natural tissues and precisely designed to fit for cell adhesion. AM was synchronously fixed by alginate dialdehyde (ADA) and EDC/NHS, forming a "double-cross-linked" stable structure with significantly improved mechanical strength and resistance against enzymic degradation. The hemolytic and platelet adhesion test indicated that ADA/REDV-AM could inhibit hemolysis and coagulation. It also exhibited excellent cytocompatibility. It selectively accelerated adsorption and migration of endothelial cells (ECs) while impeding adhesion and proliferation of smooth muscle cells (SMCs). It maintained EC superiority in competitive growth and avoided thrombosis in vivo. Furthermore, its property of promoting reconstruction and repair of blood vessels was proved in an animal experiment. Overall, the present study demonstrates that ADA/REDV-AM has potential application as a small-diameter artificial vascular intima with rapid endothelialization and reduced SMC/platelet adhesion.