Composite nanofibrous dressing loaded with Prussian blue and heparin for anti-inflammation therapy and diabetic wound healing

Diabetic ulcer is a severe complication of diabetes that can lead to amputation due to the overproduction of pro-inflammatory factors and reactive oxygen species (ROS). In this study, a composite nanofibrous dressing was developed by combining Prussian blue nanocrystals (PBNCs) and heparin sodium (Hep) through electrospinning, electrospraying, and chemical deposition. The nanofibrous dressing (PPBDH) was designed to take advantage of the excellent pro-inflammatory factor-adsorbing capability of Hep and the ROS-scavenging capabilities of PBNCs, resulting in synergistic treatment. It is worth noting that the nanozymes were firmly anchored to the fiber surfaces through slight polymer swelling caused by the solvent during electrospinning, thereby guaranteeing the preservation of the enzyme-like activity levels of PBNCs. The PPBDH dressing was found to be effective in reducing intracellular ROS levels, protecting cells from ROS-induced apoptosis, and capturing excessive pro-inflammatory factors, including chemoattractant protein-1 (MCP-1) and interleukin-1β (IL-1β). Furthermore, a chronic wound healing evaluation conducted in vivo demonstrated that the PPBDH dressing was able to effectively alleviate the inflammatory response and accelerate wound healing. This research presents an innovative approach to fabricate nanozyme hybrid nanofibrous dressings, which have great potential in accelerating the healing of chronic and refractory wounds with uncontrolled inflammation.

Advances in Enhancing Hemocompatibility of Hemodialysis Hollow-Fiber Membranes

Hemodialysis, the most common modality of renal replacement therapy, is critically required to remove uremic toxins from the blood of patients with end-stage kidney disease. However, the chronic inflammation, oxidative stress as well as thrombosis induced by the long-term contact of hemoincompatible hollow-fiber membranes (HFMs) contribute to the increase in cardiovascular diseases and mortality in this patient population. This review first retrospectively analyzes the current clinical and laboratory research progress in improving the hemocompatibility of HFMs. Details on different HFMs currently in clinical use and their design are described. Subsequently, we elaborate on the adverse interactions between blood and HFMs, involving protein adsorption, platelet adhesion and activation, and the activation of immune and coagulation systems, and the focus is on how to improve the hemocompatibility of HFMs in these aspects. Finally, challenges and future perspectives for improving the hemocompatibility of HFMs are also discussed to promote the development and clinical application of new hemocompatible HFMs.

Graphical Abstract

Recent research advances on corrosion mechanism and protection, and novel coating materials of magnesium alloys: a review

Magnesium alloys have achieved a good balance between biocompatibility and mechanical properties, and have great potential for clinical application, and their performance as implant materials has been continuously improved in recent years. However, a high degradation rate of Mg alloys in a physiological environment remains a major limitation before clinical application. In this review, according to the human body's intake of elements, the current mainstream implanted magnesium alloy system is classified and discussed, and the corrosion mechanism of magnesium alloy in vivo and in vitro is described, including general corrosion, localized corrosion, pitting corrosion, and degradation of body fluid environment impact etc. The introduction of methods to improve the mechanical properties and biocorrosion resistance of magnesium alloys is divided into two parts: the alloying part mainly discusses the strengthening mechanisms of alloying elements, including grain refinement strengthening, solid solution strengthening, dislocation strengthening and precipitation strengthening etc.; the surface modification part introduces the ideas and applications of novel materials with excellent properties such as graphene and biomimetic materials in the development of functional coatings. Finally, the existing problems are summarized, and the future development direction is prospected.

Antiblood Cell Adhesion of Mussel-Inspired Chondroitin Sulfate- and Caffeic Acid-Modified Polycarbonate Membranes

We fabricated a mussel-inspired hemocompatible polycarbonate membrane (PC) modified by the cross-linking of chondroitin sulfate and caffeic acid polymer using CA-CS via a Schiff base and Michael addition reaction and named it CA-CS-PC. The as-fabricated CA-CS-PC membrane shows excellent hydrophilicity with a water contact angle of 0° and a negative surface charge with a zeta potential of -32 mV. The antiadhesion property of the CA-CS-modified PC membrane was investigated by enzyme-linked immunosorbent assay (ELISA), using human plasma protein fibrinogen adsorption studies, and proved to have excellent antiadhesion properties, because of the lower fibrinogen adsorption. In addition, the CA-CS-PC membrane also shows enhanced hemocompatibility. Finally, blood cell attachment tests of the CA-CS-PC membrane were observed by CLSM and SEM, and the obtained results proved that CA-CS-PC effectively resisted cell adhesion, such as platelets and leucocytes. Therefore, this work disclosed a new way to design a simple and versatile modification of the membrane surface by caffeic acid and chondroitin sulfate and apply it for cell adhesion.

Targeted chitosan nanoparticles embedded into graphene oxide functionalized with caffeic acid as a potential drug delivery system: New insight into cancer therapy

As a novel drug delivery technology, chitosan (CHI) nanoparticles are encapsulated in graphene oxide (GO) with caffeic acid (CA). The nanocarrier technique combines targeted drug delivery with molecular imaging to provide new cancer insights. Attachment of CA, an anticancer agent for controlled drug release, to functionalized graphene oxide (GON) utilizing 3-aminopropyltriethoxysilane (APTES) was followed by encapsulation of GO with folic acid (FA) attached CHI to produce this novel system. FT-IR was used to characterize and confirm the chemical production process. Brunau-Emmet-Teller (BET) analysis was used to validate multi-holes and nanometric dimensions (1-100 nm) and assess their drug administration use. Release and loading tests showed a pH dependence and implied CA hydrogen-bonding in GON. CA encapsulation and loading percentages are 86 % and 67 %, respectively. The acidic environment (pH 5.3) of tumor cells may produce a larger release of CA, and the release rate of CA maintains a constant trend, indicating the drug is released for more than a week (because the release rate has not reached zero). The proposed method provides a potential candidate for a novel drug delivery system in cancer therapy. The resulting nanohybrid system is a new way to combine biodegradable materials, that can be used in biomedical applications.

Glycosaminoglycan Mimetic Precision Glycomacromolecules with Sequence-Defined Sulfation and Rigidity Patterns

Sulfated glycosaminoglycans (sGAGs) such as heparan sulfate (HS) are structurally diverse linear polysaccharides that are involved in many biological processes and have gained interest as antiviral compounds. Their recognition is driven by a complex orchestra of structural parameters that are still under intense investigation. One distinct characteristic is the incorporation of sulfation patterns including highly sulfated and non-sulfated sequences that provide variations in flexibility and conformation, which in turn impact the biological function of sGAGs. However, these distinct features have not yet been fully realized in the synthetic preparation of sGAG mimetics. Here, we present the synthesis of three groups of sulfated glycomacromolecules as sGAG mimetics: (i) globally sulfated glycooligomers, (ii) glycooligomers with sequence-defined sulfation patterns, and (iii) a globally sulfated glycooligomer-oligo-L-proline hybrid structure. The complete synthesis, including chemical sulfation, was conducted on solid support, enabled by the introduction of a commercially available photocleavable linker allowing for the preservation of sensitive sulfates during cleavage of the products. Structures were obtained in good purity and with high degrees of sulfation demonstrating the wide applicability of this methodology to prepare tailor-made sulfated glycomacromolecules and similar sGAG mimetics. Structures were tested for their anticoagulant properties showing activity similar to their natural HS counterpart and significantly lower than HP.

Preparation and blood compatibility of polyethersulfone dialysis membrane modified by apixaban as coagulation factor Xa inhibitor

Blood purification therapy is widely used in the treatment of critically ill patients. However, most dialysis membranes are prone to thrombosis. Activated coagulation factor X (FXa) functions at the intersection of intrinsic, extrinsic, and common coagulation pathways and plays a central role in thrombogenesis. To date, few dialysis membranes that directly inhibit FXa have been reported. We modified a polyethersulfone(PES) membrane using apixaban as an FXa inhibitor and investigated the performance of this membrane (AMPES). The contact angle of the modified membrane was reduced. PWF and retention rates of BSA were increased, demonstrating good hydrophilicity and dialysis performance. Albumin adsorption was reduced from 141.8 ± 15.5 to 114.1 ± 6.9 μg cm^-2. Reduced protein adsorption, especially targeted anti-FXa effect, inhibited the activation of intrinsic, extrinsic, and common coagulation pathways, as evidenced by significant prolongations of activated partial thromboplastin time, prothrombin time, and thrombin time by 145.04, 46.84 and 11.46 s, respectively. Furthermore, we determined the FXa concentration of each group, and found that the modified membrane had better anticoagulant performance through the inhibition of FXa. Favorable antiplatelet activity was also demonstrated. Thromboelastogram was used to comprehensively evaluate the anticoagulant and antithrombotic activities of the modified membrane. The R value was increased by 43.1 min, while the reduction in α angle was 42.5°. The coagulation comprehensive index reduction was 34.3. In addition, C3a and C5a were decreased by 15.3 % and 30.4 %, respectively. Furthermore, in vitro cytotoxicity and erythrocyte stability testing as well as in vivo murine experiments demonstrated the biosafety of the modified membrane. These results indicate that the AMPES dialysis membrane has an excellent potential for clinical applications.

One step preparation of multifunctional poly (ether sulfone) thin films with potential for wound dressing

The increasing demand for higher-quality medical care has resulted in the obsolescence of traditional biomaterials. Medical care is currently transitioning from an era depending on single-functional biomaterials to one that is supported by multifunctional and stable biomaterials. Herein, long-lasting multifunctional poly(ether sulfone) thin films (MPFs) containing heparin-mimic groups and a quaternary ammonium compound (QAC) were prepared via semi-interpenetrating polymer network (SIPN) strategy. The MPFs, with rough surface and inner finger-like macrovoid, had better hydrophilicity and anti-protein fouling ability, as revealed by scanning electron microscopy (SEM), atomic force microscope (AFM) and water contact angle (WCA) and protein adsorption tests. The results of platelet adhesion and activation, and clotting time confirmed that the hemocompatibility of the MPFs was significantly improved. From cell culture and germ-culture test, it was noted that the overall trend of human umbilical vein endothelial cell (HUVEC) proliferation was enhanced by a combination of heparin-mimic groups and QAC, whereas the growth of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was significantly prohibited. In addition, the MPFs were capable of modulating the expression level of basic fibroblast growth factor (bFGF) and transforming growth factor-beta1 (TGF-β1) in fibroblast, which was beneficial to controlling the formation of hypertrophic scar. In summary, the MPFs had potential to be used in the field of wound management and the study might help guide the design of surface structure of wound dressing.

Manufacturing and Separation Characteristics of Hemodialysis Membranes to Improve Toxin Removal Rate

With the recently growing interest in health care, hemodialysis is being performed not only to treat patients with renal disease but also to improve blood circulation. At present, filters used for hemodialysis are manufactured only in certain countries, and all other countries must rely on imports. In this study, polyethersulfone (PES), which has excellent blood compatibility, was used as the main material to develop hemodialysis membranes for hemodialysis filters, and these hemodialysis membranes were prepared by adding a hydrophilic polymer, polyvinylpyrrolidone (PVP), and varying the type of nonsolvent during the manufacturing process to improve the toxin removal rate and biocompatibility. The addition of PVP was confirmed through attenuated total reflection Fourier transform infrared (ATR-FTIR), and the structure of the membranes depending on the nonsolvent was analyzed through scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. The contact angle results indicated that the hydrophilicity of the membrane surface was improved as the concentration of PVP increased. The results of the toxin filtration efficiency experiment using urea, creatinine, and bovine serum albumin (BSA) confirmed removal rates of 58.8% and 56.87%, respectively, and a protein loss of less than 8%. Also, cell viability was over 90% at the PVP concentration of 2% or higher. A preliminary study was conducted on the improvement of toxin filtration efficiency and the development potential of these hemodialysis membranes with excellent biocompatibility.

Synthesis of Star 6-Arm Polyethylene Glycol-Heparin Copolymer to Construct Anticorrosive and Biocompatible Coating on Magnesium Alloy Surface

Magnesium alloy has become a research hotspot of the degradable vascular stent materials due to its biodegradability and excellent mechanical properties. However, its rapid degradation rate after implantation and the limited biocompatibility restrict its application in clinic. Constructing a multifunctional bioactive polymer coating on the magnesium alloys represents one of the popular and effective approaches to simultaneously improve the corrosion resistance and biocompatibility. In the present study, the copolymer of 6-arm polyethylene glycol and heparin (PEG-Hep) was successfully synthesized and then immobilized on the surface of chitosan (Chi)-modified magnesium alloy surface through electrostatic interaction to improve the corrosion resistance and biocompatibility. The results of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy showed that a dense and compact coating was created on the magnesium alloy surface. The coating displayed excellent hydrophilicity. At the same time, the as-prepared coating can significantly not only improve the corrosion potential, reduce the corrosion current and the pH changes of the immersion solution, but also keep a relatively intact surface morphology after immersing in simulated body fluid solution for 14 days, demonstrating that the coating can significantly improve the corrosion resistance of the magnesium alloy. Moreover, the magnesium alloy with PEG-Hep coating exhibited excellent hemocompatibility according to the results of the hemolysis rate and platelet adhesion and activation. In addition, the modified magnesium alloy had a good ability to promote the endothelial cell adhesion and proliferation. Therefore, the PEG-Hep multifunctional coating can be applied in the surface modification of the biodegradable magnesium alloy stent to simultaneously improve the corrosion resistance and biocompatibility.

Recent trends in therapeutic application of engineered blood purification materials for kidney disease

Blood purification is a commonly used method to remove excess metabolic waste in the blood in renal replacement therapy. The sufficient removal of these toxins from blood can reduce complications and improve survival lifetime in dialysis patients. However, the current biological blood purification materials in clinical practice are not ideal, where there is an unmet need for producing novel materials that have better biocompatibility, reduced toxicity, and, in particular, more efficient toxin clearance rates and a lower cost of production. Given this, this review has carefully summarized newly developed engineered different structural biomedical materials for blood purification in terms of types and structure characteristics of blood purification materials, the production process, as well as interfacial chemical adsorption properties or mechanisms. This study may provide a valuable reference for fabricating a user-friendly purification device that is more suitable for clinical blood purification applications in dialysis patients.

Fluorescent polydopamine based molecularly imprinted sensor for ultrafast and selective detection of p-nitrophenol in drinking water

A highly effective fluorescent molecularly imprinted sensor (F-PDA-MIS) based on fluorescent polydopamine (F-PDA) was successfully synthesized for selective and ultrafast detection of p-nitrophenol (P-NP) in drinking water. F-PDA with abundant surface functional groups has been artfully modified to firstly serve as both fluorescent monomer and functional monomer in the synthesis of a uniform luminous F-PDA-MIS, which can greatly improve the detection efficiency. As expected, F-PDA-MIS had an obvious emission wavelength of 535 nm with the optimal excitation wavelength at 400 nm. Specially, F-PDA-MIS could detect P-NP in the range 100 to 1100 nM with much lower detection limit of 24.2 nM within 120 s compared with other conventional imprinted fluorescent sensors based on pure quantum dots (QDs) or dyes. This excellent test phenomenon is mainly ascribed to the rapid electron transfer between F-PDA and P-NP. Satisfactory recovery of 98.0-104% for mineral water and 98.6-106% for boiling water were obtained with relative standard deviations (RSDs) of 2.7-3.4% and 2.6-3.5% respectively. The detection reliability of F-PDA-MIS was verified by the comparison with high-performance liquid chromatography (HPLC-UV). Consequently, F-PDA as a fluorescence functional monomer has been shown to be a possible strategy to effectively improve the detection limit and shorten response time of the target determination in water..

Advances in coatings on magnesium alloys for cardiovascular stents - A review

Magnesium (Mg) and its alloys, as potential biodegradable materials, have drawn wide attention in the cardiovascular stent field because of their appropriate mechanical properties and biocompatibility. Nevertheless, the occurrence of thrombosis, inflammation, and restenosis of implanted Mg alloy stents caused by their poor corrosion resistance and insufficient endothelialization restrains their anticipated clinical applications. Numerous surface treatment tactics have mainly striven to modify the Mg alloy for inhibiting its degradation rate and enduing it with biological functionality. This review focuses on highlighting and summarizing the latest research progress in functionalized coatings on Mg alloys for cardiovascular stents over the last decade, regarding preparation strategies for metal oxide, metal hydroxide, inorganic nonmetallic, polymer, and their composite coatings; and the performance of these strategies in regulating degradation behavior and biofunction. Potential research direction is also concisely discussed to help guide biological functionalized strategies and inspire further innovations. It is hoped that this review can give assistance to the surface modification of cardiovascular Mg-based stents and promote future advancements in this emerging research field.

Hyaluronic Acid/Collagen Nanofiber Tubular Scaffolds Support Endothelial Cell Proliferation, Phenotypic Shape and Endothelialization

In this study, we designed and synthetized artificial vascular scaffolds based on nanofibers of collagen functionalized with hyaluronic acid (HA) in order to direct the phenotypic shape, proliferation, and complete endothelization of mouse primary aortic endothelial cells (PAECs). Layered tubular HA/collagen nanofibers were prepared using electrospinning and crosslinking process. The obtained scaffold is composed of a thin inner layer and a thick outer layer that structurally mimic the layer the intima and media layers of the native blood vessels, respectively. Compared with the pure tubular collagen nanofibers, the surface of HA functionalized collagen nanofibers has higher anisotropic wettability and mechanical flexibility. HA/collagen nanofibers can significantly promote the elongation, proliferation and phenotypic shape expression of PAECs. In vitro co-culture of mouse PAECs and their corresponding smooth muscle cells (SMCs) showed that the luminal endothelialization governs the biophysical integrity of the newly formed extracellular matrix (e.g., collagen and elastin fibers) and structural remodeling of SMCs. Furthermore, in vitro hemocompatibility assays indicated that HA/collagen nanofibers have no detectable degree of hemolysis and coagulation, suggesting their promise as engineered vascular implants.

Novel Positively Charged Metal-Coordinated Nanofiltration Membrane for Lithium Recovery

Nanofiltration (NF) with high water flux and precise separation performance with high Li⁺/Mg²⁺ selectivity is ideal for lithium brine recovery. However, conventional polyamide-based commercial NF membranes are ineffective in lithium recovery processes due to their undesired Li⁺/Mg²⁺ selectivity. In addition, they are constrained by the water permeance selectivity trade-off, which means that a highly permeable membrane often has lower selectivity. In this study, we developed a novel nonpolyamide NF membrane based on metal-coordinated structure, which exhibits simultaneously improved water permeance and Li⁺/Mg²⁺ selectivity. Specifically, the optimized Cu-m-phenylenediamine (MPD) membrane demonstrated a high water permeance of 16.2 ± 2.7 LMH/bar and a high Li⁺/Mg²⁺ selectivity of 8.0 ± 1.0, which surpassed the trade-off of permeance selectivity. Meanwhile, the existence of copper in the Cu-MPD membrane further enhanced anti-biofouling property and the metal-coordinated nanofiltration membrane possesses a pH-responsive property. Finally, a transport model based on the Nernst-Planck equations has been developed to fit the water flux and rejection of uncharged solutes to the experiments conducted. The model had a deviation below 2% for all experiments performed and suggested an average pore radius of 1.25 nm with a porosity of 21% for the Cu-MPD membrane. Overall, our study provides an exciting approach for fabricating a nonpolyamide high-performance nanofiltration membrane in the context of lithium recovery.

Dopamine-Functionalized Gellan Gum Hydrogel as a Candidate Biomaterial for a Retinal Pigment Epithelium Cell Delivery System

In this study, dopamine-functionalized gellan gum (DFG) hydrogel was prepared as a carrier for retinal pigment epithelium (RPE) cell delivery via a carbodiimide reaction. The carboxylic acid of gellan gum (GG) was replaced with catechol in a 21.3% yield, which was confirmed by NMR. Sol fraction and weight loss measurements revealed that dopamine improved degradability in the GG hydrogel. Measurements of the viscosity, injection force, and compressibility also showed that dopamine-functionalized GG hydrogels had more desirable rheological/mechanical properties for improving injectability. These characteristics were confirmed to arise from the GG's helix structure loosened by the dopamine's bulky nature. Moreover, dopamine's hydrophilic characteristics were confirmed to create a more favorable microenvironment for cell growth by promoting swelling capability and cell attachment. This improved biocompatibility became more pronounced when the hydrophilicity of dopamine was combined with a larger specific surface area stemming from the less porous structure of the dopamine-grafted hydrogels. This effect was apparent from the live/dead staining images of the as-prepared hydrogels. Meanwhile, the nonionic cross-linked DFG (DG) hydrogel showed the lowest protein expression in the immunofluorescence staining images obtained after 28 days of culture, supporting that it had the highest degradability and associated cell-releasing ability. That tendency was also observed in the gene expression data acquired by real-time polymerase chain reaction (RT-PCR) analysis. RT-PCR analysis also revealed that the DG hydrogel carrier could upregulate the visual function-related gene of RPE. Overall, the DG hydrogel system demonstrated its feasibility as a carrier of RPE cells and its potential as a means of improving visual function.

Resveratrol as a plant type antioxidant modifier for polysulfone membranes to improve hemodialysis-induced oxidative stress

Resveratrol (RES) is a plant extract with excellent antioxidant, biocompatibility, anti-inflammatory and inhibition of platelet aggregation. RES-modified polysulfone (PSF) hemodialysis membranes have been fabricated using an immersion phase transformation method. The antioxidant properties of the blend membranes were evaluated in terms of their 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS⁺), reactive oxygen species (ROS) free radicals scavenging, total antioxidant capacity (T-AOC) of serum and lipid peroxidation inhibition. The observed results of decreasing DPPH and ABTS⁺ levels, scavenging ROS, significant inhibition of lipid peroxidation and improving the T-AOC of serum all contribute to the recovery of oxidative balance and the use of RES as an antioxidant modifier. The antioxidant stability of PSF/RES blend membranes was also studied. Moreover, the results of blood compatibility experiments showed that the addition of RES improved the blood compatibility of PSF membrane, inhibited the adhesion of red blood cells and platelets; inhibited complement activation; and reduced the blood cells deformation rate. The dialysis simulation experiment indicated that PSF/RES membrane (M-3) can clear 90.33% urea, 89.50% creatinine, 74.60% lysozyme and retention 90.47% BSA. All these results showed the new PSF/RES blend membranes have potential to be used in the field of hemodialysis to improve oxidative stress status in patients.

A review on surface modification methods of poly(arylsulfone) membranes for biomedical applications

Considerable methods have so far been used for the surface modification of biomedical membranes. Several reviews and articles have been published on the improvements achieved in the field of poly(arylsulfone) membranes subjected to various surface modification methods and used in biomedical applications. This review concentrates on the surface modification, biological applications and future perspective of the poly(arylsulfone) biomedical membranes. Different surface modification procedures employed for the poly(arylsulfone) membranes have been classified, studied and compared. Diverse surface modification techniques include surface coating, chemical modification and immobilization/cross-linking, grafting, surface zwitterionicalization, mussel-inspired coating and layer-by-layer assembly. Furthermore, we review the recent research studies performed on the surface modification of the poly(arylsulfone) biomedical membranes. Meanwhile, the properties of biomedical membranes are also discussed in each section. At last, the future perspective and challenges of the strategies utilized for the surface modification of poly(arylsulfone) biomedical membranes are presented.

Vascular cell responses to silicone surfaces grafted with heparin-like polymers: surface chemical composition vs. topographic patterning

Heparin-like polymers are promising synthetic materials with biological functionalities, such as anticoagulant ability, growth factor binding to regulate cellular functions, and inflammation mediation, similar to heparin. The biocompatibility of heparin-like polymers with well-defined chemical structures has inspired many researchers to design heparin-like surfaces to explore their biological applications. The concept of the recombination of functional heparin structural units (sulfonate- and glyco-containing units) was proven to be successful in designing heparin-mimicking surfaces. However, besides surface structural units, topographic patterning is also an important contributor to the biological activity of the surfaces modified with heparin-like polymers. In this work, both surface structural units and topographic patterning were taken into account to investigate the vascular cell behaviors on the silicone surfaces. A facile method for the production of patterned bromine-containing polydimethylsiloxane surface (PDMS-Br) was developed from a one-step multicomponent thermocuring procedure and replica molding using a nanohole-arrayed silicon template. Different structural units of heparin-like polymers, i.e. homopolymer of sulfonate-containing sodium 4-vinylbenzenesulfonate (pSS), homopolymer of glyco-containing 2-(methacrylamido)glucopyranose (pMAG), and copolymers of MAG and SS (pSG), were then introduced on the flat and patterned PDMS-Br surface using visible light-induced graft polymerization. For the flat surfaces, compared with the PDMS-Br surface, pSS-grafted and pSG-grafted surfaces significantly increased cell densities of both human umbilical vein endothelial cells (HUVECs) and human umbilical vein smooth muscle cells (HUVSMCs), indicating that they are "vascular cell-friendly". In contrast, the pMAG-grafted surface showed decreased cell attachment of both HUVECs and HUVSMCs, indicating that the pMAG-grafted surface is "vascular cell-resistant". Moreover, surface topographic patterning enhanced the cell responses to the corresponding flat surfaces. That is to say, surface patterning can make the "vascular cell-friendly" surface still friendly, and the "vascular cell-resistant" surface much more resistant. The combination of surface structural units and topographic patterning shows promise in the preparation of new heparin-like surfaces with improved cell compatibility that is suitable for blood-compatible biomaterials.

Bio-surface coated titanium scaffolds with cancellous bone-like biomimetic structure for enhanced bone tissue regeneration

In view of the fact that titanium (Ti)-based implants still face the problem of loosening and failure of the implants caused by the slow biological response, the low osseointegration rate and the implant bacterial infection in clinical application, we designed a cancellous bone-like biomimetic Ti scaffold using the template accumulated by sugar spheres as a pore-forming agent. And based on a modified surface mineralization process and mussel-like adhesion mechanism, a silicon-doped calcium phosphate composite coating (Van-pBNPs/pep@pSiCaP) with Vancomycin (Van)-loaded polydopamine (pDA)-modified albumin nanoparticles (Van-pBNPs) and cell adhesion peptides (GFOGER) was constructed on the surface of Ti scaffold for mimicking the extracellular matrix (ECM) microenvironment of natural bone matrix to induce greater tissue regeneration. The in vitro study demonstrated that this porous Ti scaffold with functional bio-surface could distinctly facilitate cell early adhesion and spreading, and activate the expression of α2β1 integrin receptor on the cell membrane through promoting the formation of focal adhesions (FAs) in bone marrow stromal cells (BMSCs), thus mediating greater osteogenic cell differentiation. And it could also effectively inhibit the adhesion and growth of Staphylococcus epidermidis, exhibiting good antibacterial properties. Moreover, the Van-pBNPs/pep@pSiCaP-Ti scaffolds showed enhanced in vivo bone-forming ability due to the contributions of bioactive chemical components and the natural cancellous bone-like macrostructure. This work offers a promising structural and functional bio-inspired strategy for designing metal implants with desirable ability of osteoinduction synergistically with antibacterial efficacy for promoting bone regeneration and infection prevention simultaneously. STATEMENT OF SIGNIFICANCE: This manuscript describes a new method for making porous Ti scaffolds with a natural cancellous bone-like structure. Besides, a functional bio-surface was constructed on the bionic structure, mimicking some of the functions of the collagen-rich organic matrix and inorganic CaP nanocrystallites of native ECM of bone in chemical components and biological activities. This interconnected inter-pore opening structure encouraged the migration of cells among open macro-pores within the scaffold. In addition, the functionalized surface not only improved early cell adhesion, spreading, stimulated greater osteogenic differentiation of bone-forming cells, but also endowed the scaffold with excellent antibacterial effect. The biomimetic metal implant with multiple biomedical functions designed in this study has a great clinical application potential. This study represents a feasible method for the preparation of biomimetic structure of metal implants and the improvement of their surface biological activity.

Metallic Nanoparticle-Decorated Polydopamine Thin Films and Their Cell Proliferation Characteristics

Plasmonic metal nanoparticle (NP)-decorated thin films of biobased and biocompatible polymers provide significant opportunities in various biomedical applications. Inspired from the adhesive proteins of the marine mussels, polydopamine (PDA) serves as a versatile, biocompatible, and simple thin-film material and enhances cell growth and proliferation. Herein, we report the fabrication of the gold NPs (AuNPs) or silver NPs (AgNPs)-deposited thin films of PDA and their employment in cell growth and proliferation. PDA thin film with its numerous functional groups enabled well-controlled adsorption of NPs. The number density of NPs was manipulated simply by tuning the deposition time. Cell viability test for human lung cancer (A549) and human colon cancer (CaCO2) cell lines indicated that a thin layer of PDA film remarkably enhanced the cell growth and proliferation. The lower number density of NPs for the 24 h of the culture time resulted in a higher proliferation rate. However, the increase in both the number density of NPs and culture time led to a decrease in cell growth.

Hemocompatible magnetic particles with broad-spectrum bacteria capture capability for blood purification

Pathogen capture and removal from whole blood is a new strategy for extracorporeal blood purification, especially in initial treatment of sepsis before pathogen identification. Herein, hemocompatible magnetic particles with broad-spectrum bacteria capture capability were proposed for pathogen removal from whole blood, omitting the necessity of pathogen identification. Firstly, we designed and synthesized a new kind of imidazolium-based ionic liquid with good antibacterial activity, and polydopamine coating was utilized as a hemocompatible platform to immobilize ionic liquids on Fe₃O₄ nanoparticles, forming the hemocompatible magnetic particles (Fe₃O₄@PDA-IL). The magnetic particles exhibited good hemocompatibility and performed well in the removal of various species of clinically significant pathogens from human whole blood, including S. aureus, E. coli, and the hard-to-treat bacteria of P. aeruginosa and Methicillin-resistant S. aureus, which are the most common pathogens in bloodstream infections. Besides, the Fe₃O₄@PDA-IL particles were also capable to remove bacterial endotoxins from blood, inhibiting further aggravation of sepsis. Overall, we demonstrated the application of hemocompatible magnetic particles in the removal of pathogens and bacterial endotoxins from whole blood via electrostatic and hydrophobic interactions, without significant effects on blood cells or the activation of coagulation and complement, addressing the feasibility of using imidazolium-based ionic liquids for bacteria capture and removal from whole blood. It would contribute to the development of magnetic separation-based approaches to remove bacteria and bacterial endotoxin for extracorporeal blood purification, especially in initial sepsis therapy before pathogen identification.

Layered hydroxide/polydopamine/hyaluronic acid functionalized magnesium alloys for enhanced anticorrosion, biocompatibility and antithrombogenicity in vascular stents

Magnesium alloys are promising cardiovascular stent materials due to the favourable physical properties and complete biodegradability in vivo. However, the rapid degradation, poor cytocompatibility and tendency of thrombogenesis hinder practical clinical applications. In order to solve these problems, a facile and highly efficient strategy of alkali treatment combined with subsequent layer-by-layer assembly was used to fabricate a multifunctional coating. A bottom layer hydroxyl (–OH) with negative charge after alkali treatment first formed a solid bond with magnesium matrix to provide a rough outer surface for the further immobilization of functional biomolecules. Afterwards, polydopamine and hyaluronic acid were successively immobilized on alkali-treated magnesium surface via strong electrostatic adsorption and covalent bonding between carboxyl group of hyaluronic acid and amine or hydroxyl of polydopamine to form magnesium/OH/polydopamine/hyaluronic acid. Hydroxyl significantly improves the corrosion resistance while polydopamine and hyaluronic acid layers act as a further barrier to provide better anticorrosion. A balance between biocompatibility and antithrombogenicity has been achieved by adjusting the content of hyaluronic acid on polydopamine surface. The multifunctional magnesium/OH/polydopamine/hyaluronic acid coating with lower hyaluronic acid concentrations expose more active sites of polydopamine molecules to promote endothelial cell proliferation while retaining the intrinsic antithrombogenic function of hyaluronic acid to offer a potential application for vascular stents.

An Injectable Conductive Three-Dimensional Elastic Network by Tangled Surgical-Suture Spring for Heart Repair

Designing scaffolds with persistent elasticity and conductivity to mimic microenvironments becomes a feasible way to repair cardiac tissue. Injectable biomaterials for cardiac tissue engineering have demonstrated the ability to restore cardiac function by preventing ventricular dilation, enhancing angiogenesis, and improving conduction velocity. However, limitations are still among them, such as poor mechanical stability, low conductivity, and complicated procedure. Here, we developed thermal plastic poly(glycolic acid) surgical suture and mussel-inspired conductive particle's adhesion into a highly elastic, conductive spring-like coils. The polypyrrole (PPy)-coated biospring acted as an electrode and then was assembled into a solid-state supercapacitor. After being injected through a syringe needle (0.33 mm inner diameter), the tangled coils formed an elastically conductive three-dimensional (3-D) network to modulate cardiac function. We found that cardiomyocytes (CMs) grew along the spring coils' track with elongated morphologies and formed highly oriented sarcomeres. The biospring enhanced the CMs' maturation in synchronous contraction accompanied by high expressions of cardiac-specific proteins, α-actinin, and connexin 43 (cx43). After the elastic, conductive biosprings were injected into the myocardial infarction (MI) area, the left ventricular fractional shortening was improved by about 12.6% and the infarct size was decreased by about 34%. Interestingly, the spring can be utilized as a sensor to measure the CMs' contractile force, which was 1.57 × 10^-3 ± 0.26 × 10^-3 mN (∼4.1 × 10⁶ cells). Accordingly, this study highlights an injectable biospring to form a tangled conductive 3-D network in vivo for MI repair.

Urease immobilized GO core@shell heparin-mimicking polymer beads with safe and effective urea removal for blood purification

Adsorbents are usually used to remove uremic toxins for blood purification. However, the removal of urea is still an intractable problem, since no effective material has been found for urea removal by physical adsorption. Here, urease immobilized graphene oxide core@shell heparin-mimicking polymer (U-GO-HMP) beads were designed, which exhibited good urea removal ability with a removal amount of about 635 mg/g and a removal ratio of about 80% from urea solution. In addition, urea could be removed from collected dialysate and the removal ratio could reach 60% within 480 min. Beyond that, the U-GO-HMP beads also showed good reusability with sustainable relative activity after 5 cycles. Furthermore, the U-GO-HMP beads exhibited good blood compatibility with low hemolysis ratio, suppressed complement activation and contact activation, as well as increased clotting times. It is worthy believing that the U-GO-HMP beads may have great potential in the field of blood purification for urea removal.

Synergistic effect of functionalized poly(l-lactide) with surface-modified MgO and chitin whiskers on osteogenesis in vivo and in vitro

Favorable cytocompatibility and osteogenesis potential are critical for the development of a bone repair material. In this study, two types of surface-modified whiskers, grafted magnesia and chitin (g-MgO and g-CHN) whiskers, were synthesized and introduced into a poly(l-lactide) (PLLA) matrix singly or together to prepare PLLA/g-MgO/g-CHN composite films and bone nails via injection molding. On the account of the synergetic contribution of g-MgO and g-CHN whiskers, the enhanced cell adhesion, spreading, proliferation of mouse embryo osteoblast precursor (MC3T3-E1) cells, as well as the alteration of cell-cycle and inhibition of cell apoptosis, were observed on PLLA/g-MgO/g-CHN film as compared to pure PLLA, PLLA/g-MgO and PLLA/g-CHN films. More importantly, the highest level of the secretion of ALP and the formation of calcium deposition, accompanied with expression of osteogenesis genes (ALP, Runx-2, COL I, OCN) in vitro were obtained for the PLLA/g-MgO/g-CHN film among all of the material groups. Additionally, the PLLA and PLLA composite bone nails were implanted in rabbits' femurs and new bone formation was detected on PLLA/g-MgO/g-CHN group after 16 weeks of implantation by 3D reconstruction of micro-CT and histological analyses. Besides, the bending strength of defected bone repaired by PLLA/g-MgO/g-CHN bone nail was high to 48 MPa, which was far stronger than other bone nail groups. Overall, this study demonstrated the addition of g-MgO and g-CHN whiskers together in PLLA matrix played a synergistic promoting role in cell affinity and osteogenic differentiation, and the developed PLLA/g-MgO/g-CHN composites hold great potential in fields of bone repair.

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.

In vitro and in vivo anticoagulant activity of heparin-like biomacromolecules and the mechanism analysis for heparin-mimicking activity

Heparin-like biomacromolecules (HepLBm), exhibiting similar chemical structure and biological properties to heparin, can be obtained by modifying either synthetic biopolymers or natural biomacromolecules with physical or chemical methods. In this work, a low-cost and biocompatible sodium alginate was chosen as a model biomacromolecule to design anticoagulant HepLBm with a similar sulfation degree to heparin. FTIR, ¹H NMR, and element analysis data were used to confirm the chemical structure of HepLBm. Hemolysis tests, clotting time, complement activation, and contact activation tests were carried out to determine the in vitro anticoagulant activity of HepLBm. In addition, systematic studies of blood cell count, coagulation function, and histopathology were performed to demonstrate the in vivo anticoagulant activity and toxicity of HepLBm with SD rat experiments. Furthermore, a series of linear molecules containing carboxyl groups, sulfonic groups, and hydroxyl groups were selected and their clotting time was tested to provide a mechanism analysis for the excellent anticoagulant activity of HepLBm. With the excellent in vitro/in vivo anticoagulant activity, good biocompatibility, and low cost, the HepLBm synthesized in this work would have great potential for substitution of heparin in many application fields, such as the surface modification of biomedical devices, extracorporeal anticoagulants, and other clinical fields.

Chemical synthesis of glycosaminoglycan-mimetic polymers

This review describes several general chemical approaches for the preparation of glycosaminoglycan (GAG)-mimetic polymers based on different backbones and sidechains, and highlights the importance of these synthetic GAG-mimetic polymers in controlling key biofunctions.

Heparin-based and heparin-inspired hydrogels: size-effect, gelation and biomedical applications

The size-effect, fabrication methods and biomedical applications of heparin-based and heparin-inspired hydrogels are reviewed.