Octadecyl Chains Immobilized onto Hyaluronic Acid Coatings by Thiol-ene "Click Chemistry" Increase the Surface Antimicrobial Properties and Prevent Platelet Adhesion and Activation to Polyurethane

Engineering anti-thrombogenic and anti-infective catheters through a stepwise metal-catechol-(amine) surface engineering strategy

Thrombosis and infection are pivotal clinical complications associated with interventional blood-contacting devices, leading to significant morbidity and mortality. To address these issues, we present a stepwise metal-catechol-(amine) (MCA) surface engineering strategy that efficiently integrates therapeutic nitric oxide (NO) gas and antibacterial peptide (ABP) onto catheters, ensuring balanced anti-thrombotic and anti-infective properties. First, copper ions were controllably incorporated with norepinephrine and hexanediamine through a one-step molecular/ion co-assembly process, creating a NO-generating and amine-rich MCA surface coating. Subsequently, azide-polyethylene glycol 4-N-hydroxysuccinimidyl and dibenzylcyclooctyne modified ABP were sequentially immobilized on the surface via amide coupling and bioorthogonal click chemistry, ensuring the dense grafting of ABP while maintaining the catalytic efficacy for NO. This efficient integration of ABP and NO-generating ability on the catheter surface provides potent antibacterial properties and ability to resist adhesion and activation of platelets, thus synergistically preventing infection and thrombosis. We anticipate that this synergistic modification strategy will offer an effective solution for advancing surface engineering and enhancing the clinical performance of biomedical devices.

Unravelling Surface Modification Strategies for Preventing Medical Device-Induced Thrombosis

The use of biomaterials in implanted medical devices remains hampered by platelet adhesion and blood coagulation. Thrombus formation is a prevalent cause of failure of these blood-contacting devices. Although systemic anticoagulant can be used to support materials and devices with poor blood compatibility, its negative effects such as an increased chance of bleeding, make materials with superior hemocompatibility extremely attractive, especially for long-term applications. This review examines blood-surface interactions, the pathogenesis of clotting on blood-contacting medical devices, popular surface modification techniques, mechanisms of action of anticoagulant coatings, and discusses future directions in biomaterial research for preventing thrombosis. In addition, this paper comprehensively reviews several novel methods that either entirely prevent interaction between material surfaces and blood components or regulate the reaction of the coagulation cascade, thrombocytes, and leukocytes.

Injectable polylysine and dextran hydrogels with robust antibacterial and ROS-scavenging activity for wound healing

Cutaneous wound management remains a major concern due to uncontrolled inflammation and bacterial infection in clinical care. A desirable hydrogel dressing with antibacterial and antioxidative properties can drive wound healing by inhibiting infection and inflammation. Herein, a multifunctional hydrogel based on polylysine-graft-cysteine (EPL-SH)/oxidized dextran (ODex) was fabricated for promoting skin tissue regeneration. The engineered hydrogel possessed versatile properties including tunable gelation time (60-300 s), typical rheological behavior, suitable swelling and degradation progress, injectable and self-healing ability. The unique hydrogels also displayed promising tissue adhesiveness, high cell affinity, excellent antioxidant and antimicrobial activity. Furthermore, the in vivo full-thickness skin defect experiment demonstrated the simple-to-implement injectable hydrogels could significantly promoting wound healing by improving the collagen deposition and angiogenesis. The manufacture of our multifunctional hydrogels dressing affords a new strategy for improving efficacy of cutaneous wound treatment.

Dicarboxylated hyaluronate: Synthesis of a new, highly functionalized and biocompatible derivative

Sequential periodate-chlorite oxidation of sodium hyaluronate to 2,3-dicarboxylated hyaluronate (DCH), a novel biocompatible and highly functionalized derivative bearing additional pair of COOH groups at C2 and C3 carbons of oxidized ᴅ-glucuronic acid units, is investigated. The impact of various reaction parameters (time, oxidizer concentration, and molar amount) on DCH's composition, molecular weight, degree of oxidation, and cytotoxicity are investigated to guide the synthesis of DCH derivatives of desired properties. Subsequently, fully (99%) and partially (70%) oxidized DCH derivatives were compared to untreated sodium hyaluronate in terms of anticancer drug cisplatin loading efficacy, carrier capacity, drug release rates, and cytotoxicity towards healthy and cancerous cell lines. DCH derivatives were found to be superior in every aspect, having nearly twice the carrier capacity, significantly slower release rates, and higher efficacy. DCH is thus a highly interesting hyaluronate derivative with an adjustable degree of oxidation, molecular weight, and great potential for further modifications.

Tiger 17 and pexiganan as antimicrobial and hemostatic boosters of cellulose acetate-containing poly(vinyl alcohol) electrospun mats for potential wound care purposes

In this research, we propose to engineer a nanostructured mat that can simultaneously kill bacteria and promote an environment conducive to healing for prospective wound care. Polyvinyl alcohol (PVA) and cellulose acetate (CA) were combined at different polymer ratios (100/0, 90/10, 80/20% v/v), electrospun and crosslinked with glutaraldehyde vapor. Crosslinked fibers increased in diameter (from 194 to 278 nm), retaining their uniform structure. Fourier-transform infrared spectroscopy and thermal analyses proved the excellent miscibility between polymers. CA incorporation incremented the fibers swelling capacity and reduced the water vapor and air permeabilities of the mats, preventing the excessive drying of wounds. The antimicrobial peptide cys-pexiganan and the immunoregulatory peptide Tiger 17 were incorporated onto the mats via polyethylene glycol spacer (hydroxyl-PEG2-maleimide) and physisorbed, respectively. Time-kill kinetics evaluations revealed the mats effectiveness against Staphylococcus aureus and Pseudomonas aeruginosa. Tiger 17 played a major role in accelerating clotting of re-calcified plasma. Data reports for the first time the collaborative effect of pexiganan and Tiger 17 against bacterial infections and in boosting hemostasis. Cytocompatibility data verified the peptide-modified mats safety. Croslinked 90/10 PVA/CA mats were deemed the most promising combination due to their moderate hydrophilicity and permeabilities, swelling capacity, and high yields of peptide loading.

Mussel-Inspired and Bioclickable Peptide Engineered Surface to Combat Thrombosis and Infection

Thrombosis and infections are the two major complications associated with extracorporeal circuits and indwelling medical devices, leading to significant mortality in clinic. To address this issue, here, we report a biomimetic surface engineering strategy by the integration of mussel-inspired adhesive peptide, with bio-orthogonal click chemistry, to tailor the surface functionalities of tubing and catheters. Inspired by mussel adhesive foot protein, a bioclickable peptide mimic (DOPA)4-azide-based structure is designed and grafted on an aminated tubing robustly based on catechol-amine chemistry. Then, the dibenzylcyclooctyne (DBCO) modified nitric oxide generating species of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelated copper ions and the DBCO-modified antimicrobial peptide (DBCO-AMP) are clicked onto the grafted surfaces via bio-orthogonal reaction. The combination of the robustly grafted AMP and Cu-DOTA endows the modified tubing with durable antimicrobial properties and ability in long-term catalytically generating NO from endogenous s-nitrosothiols to resist adhesion/activation of platelets, thus preventing the formation of thrombosis. Overall, this biomimetic surface engineering technology provides a promising solution for multicomponent surface functionalization and the surface bioengineering of biomedical devices with enhanced clinical performance.

Hyaluronic Acid-Based Wound Dressing with Antimicrobial Properties for Wound Healing Application

Wound healing is a naturally occurring process that can be aided by a wound dressing properly designed to assure an efficient healing process. An infection caused by several microorganisms could interfere with this process, delaying or even impairing wound healing. Hyaluronic acid (HA), a main constituent of the extracellular matrix (ECM) of a vertebrate’s connective tissue, represents a promising biomaterial for wound dressing thanks to its intrinsic biocompatibility, hydrophilicity and bacteriostatic properties. In this review, different and recent types of HA-based wound dressings endowed with intrinsic antimicrobial properties or co-adjuvated by antimicrobial natural or synthetic agents are highlighted.

Bioinspired ultra-low fouling coatings on medical devices to prevent device-associated infections and thrombosis

Addressing thrombosis and biofouling of indwelling medical devices within healthcare institutions is an ongoing problem. In this work, two types of ultra-low fouling surfaces (i.e., superhydrophobic and lubricant-infused slippery surfaces) were fabricated to enhance the biocompatibility of commercial medical grade silicone rubber (SR) tubes that are widely used in clinical care. The superhydrophobic (SH) coatings on the tubing substrates were successfully created by dip-coating in superhydrophobic paints consisting of polydimethylsiloxane (PDMS), perfluorosilane-coated hydrophobic zinc oxide (ZnO) and copper (Cu) nanoparticles (NPs) in tetrahydrofuran (THF). The SH surfaces were converted to lubricant-infused slippery (LIS) surfaces through the infusion of silicone oil. The anti-biofouling properties of the coatings were investigated by adsorption of platelets, whole blood coagulation, and biofilm formation in vitro. The results revealed that the LIS tubes possess superior resistance to clot formation and platelet adhesion than uncoated and SH tubes. In addition, bacterial adhesion was investigated over 7 days in a drip-flow bioreactor, where the SH-ZnO-Cu tube and its slippery counterpart significantly reduced bacterial adhesion and biofilm formation of Escherichia coli relative to control tubes (>5 log10 and >3 log10 reduction, respectively). The coatings also demonstrated good compatibility with fibroblast cells. Therefore, the proposed coatings may find potential applications in high-efficiency on-demand prevention of biofilm and thrombosis formation on medical devices to improve their biocompatibility and reduce the risk of complications from medical devices.

A One-pot-synthesized Double-layered Anticoagulant Hydrogel Tube

Extracorporeal membrane oxygenation(ECMO) has emerged as a viable treatment in severe cases of acute respiratory distress syndrome, acute respiratory failure, and adult respiratory distress syndrome. However, thromboembolic events stemming from the use of ECMO devices results in significant morbidity and mortality rates; the inner surface of the ECMO tubing comes into contact with the blood and can readily initiate coagulation. In addition, the tubing needs to be continually replaced due to thromboses on the inner tube wall, which not only increases the risk of infection but also the economic burden. Despite considerable effort, a surface modification strategy that effectively addresses these challenges has not yet been realized. In this study, we developed an integrated hollow core-shell-shell hydrogel tube of gelatin/alginate/acrylamide-bacterial nanocellulose(GAA) that meets the anticoagulant requirements for the inner tubing layer as well as the highly elastic soft material needed for the outer layer. Using static blood from healthy volunteers, we confirmed that the platelets or coagulation is not stimulated by the GAA tubing. Importantly, experiments with dynamic blood also demonstrated that the inner layer of the tubing does not elicit blood clotting. The one-pot-synthesized process may provide guidance for the design of anticoagulation tubes used clinically.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s40242-021-1267-3.

Endothelium-Mimicking Surface Combats Thrombosis and Biofouling via Synergistic Long- and Short-Distance Defense Strategy

Thrombosis and infections are the main causes of implant failures (e.g., extracorporeal circuits and indwelling medical devices), which induce significant morbidity and mortality. In this work, an endothelium-mimicking surface is engineered, which combines the nitric oxide (NO)-generating property and anti-fouling function of a healthy endothelium. The released gas signal molecules NO and the glycocalyx matrix macromolecules hyaluronic acid (HA) jointly combine long- and short-distance defense actions against thrombogenicity and biofouling. The biomimetic surface is efficiently fabricated by cografting a NO-generating species (i.e., Tri-tert-butyl 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetate-chelated Cu²⁺ , DTris@Cu) and the macromolecular HA on an aminated tube surface through one-pot amide condensation chemistry. The active attack (i.e., NO release) and zone defense (i.e., HA tethering) system endow the tubing surface with significant inhibition of platelets, fibrinogen, and bacteria adhesion, finally leading to long-term anti-thrombogenic and anti-fouling properties over 1 month. It is envisioned that this endothelium-mimicking surface engineering strategy will provide a promising solution to address the clinical issues of long-term blood-contacting devices associated with thrombosis and infection.

Decomposable black phosphorus nano-assembly for controlled delivery of cisplatin and inhibition of breast cancer metastasis

Novel platforms for cisplatin delivery with a controllable manner and combinable with other treatment modality to achieve synergistic antitumor effect and inhibition metastasis for treatment of triple negative breast cancer (TNBC) are highly desirable. Herein, we report a black phosphorus (BP) nanosheets-based nano-assembly which consists of cisplatin, BP, polydopamine (PDA) and hyaluronic acid (HA), cisplatin/BP/PDA-HA (CBPH), for controlled delivery of cisplatin and inhibition tumor growth as well as lung metastasis of TNBC. For constructing CBPH, the surface of BP was dual modified by PDA and HA, resulting in enhanced stability, tumor target ability and photothermal efficiency of BP. Cisplatin was released in response both to internal and external stimuli existed in tumor microenvironment, including low pH, hydrogen peroxide and NIR light, as accompanied by decomposition of BP. In vitro experiments demonstrated CBPH-treated 4 T1 cells showed elevated intracellular content of Pt and Pt-DNA adduct, which was further improved when exposure to NIR light, leading to potent antitumor effect in a synergistic pattern. Anti-metastasis studies in 2D monolayers and 3D organoids revealed that CBPH plus NIR light treatment exhibited significantly decreased migration, invasion and regrowth ability of 4 T1 cells. Furthermore, TNBC-bearing mice with systemic administrate of CBPH showed enhanced tumor accumulation of cisplatin and light-triggered inhibition of tumor growth at primary site and lung metastasis, with alleviated toxicity. But CBPH is yet to be optimized for realizing smart cisplatin delivery in response to acidic and redox stimuli in vivo. Collectively, our study demonstrates that this novel BP-based nano-assembly with controllable tumor delivery of cisplatin and metastasis inhibition of breast cancer expand the use of BP in biomedicine field and hold great promise for further development.

Preparation and Antifouling Property of Polyurethane Film Modified by PHMG and HA Using Layer-by-Layer Assembly

To reduce the possibility of bacterial infection and implant-related complications, surface modification on polyurethane (PU) film is an ideal solution to endow hydrophobic PU with antibacterial and antifouling properties. In this work, a variety of polyhexamethylene guanidine/ hyaluronic acid (PHMG/HA) multilayer films were self-assembled layer-by-layer on PU films using polyanions, carboxyl-activated HA, and polycations PHMG by controlling the concentration of these polyelectrolytes as well as the number of layers self-assembled. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectra, water contact angle (WCA), and A Atomic force microscope (AFM) of PU and modified PU films were studied. Protein adsorption and bacterial adhesion as well as the cytotoxicity against L929 of the film on selected PU-(PHMG/HA)₅/5-5 were estimated. The results showed that PU-(PHMG/HA)₅/5-5 had the best hydrophilicity among all the prepared films, possessing the lowest level of protein adsorption. Meanwhile, this film showed efficient broad-spectrum antibacterial performance as well as significant resistance of bacterial adhesion of more than a 99.9% drop for the selected bacteria. Moreover, almost no influence on cell viability of L929 enhanced the biocompatibility of film. Therefore, the modified PU films with admirable protein absorption resistance, antimicrobial performance, and biocompatibility would have promising applications in biomedical aspect.

Recent Advances in Fiber-Hydrogel Composites for Wound Healing and Drug Delivery Systems

In the last decades, much research has been done to fasten wound healing and target-direct drug delivery. Hydrogel-based scaffolds have been a recurrent solution in both cases, with some reaching already the market, even though their mechanical stability remains a challenge. To overcome this limitation, reinforcement of hydrogels with fibers has been explored. The structural resemblance of fiber-hydrogel composites to natural tissues has been a driving force for the optimization and exploration of these systems in biomedicine. Indeed, the combination of hydrogel-forming techniques and fiber spinning approaches has been crucial in the development of scaffolding systems with improved mechanical strength and medicinal properties. In this review, a comprehensive overview of the recently developed fiber-hydrogel composite strategies for wound healing and drug delivery is provided. The methodologies employed in fiber and hydrogel formation are also highlighted, together with the most compatible polymer combinations, as well as drug incorporation approaches creating stimuli-sensitive and triggered drug release towards an enhanced host response.

Fabrication and Evaluation of Silk Sericin-Derived Hydrogel for the Release of the Model Drug Berberine

Silk sericin (SS) produced by Bombyx mori is normally discarded as waste in manufacturing processes, which causes environmental pollution. Therefore, investigating the use of silk sericin has economic and environmental benefits. As a three-dimensional structure, the sericin-derived hydrogel was explored in different applications. However, many developed gelation procedures raise concerns regarding safety, cost, and duration of gelation time. In this work, "thiol-ene" click chemistry was used to quickly and controllably prepare an SS-derived hydrogel to resolve these early concerns. Then, berberine was loaded and used as a model for investigating the drug-release profiles of the prepared hydrogel. The experimental results revealed that this hydrogel is eligible for a long-term release of berberine. Throughout the antibacterial experiments, the released berberine maintained its antibacterial activity. Our work expands the application of SS in biomedical industries in an eco-friendly way. Furthermore, the discussed strategy could provide a reference for the subsequent development of SS-derived materials.

Spun Biotextiles in Tissue Engineering and Biomolecules Delivery Systems

Nowadays, tissue engineering is described as an interdisciplinary field that combines engineering principles and life sciences to generate implantable devices to repair, restore and/or improve functions of injured tissues. Such devices are designed to induce the interaction and integration of tissue and cells within the implantable matrices and are manufactured to meet the appropriate physical, mechanical and physiological local demands. Biodegradable constructs based on polymeric fibers are desirable for tissue engineering due to their large surface area, interconnectivity, open pore structure, and controlled mechanical strength. Additionally, biodegradable constructs are also very sought-out for biomolecule delivery systems with a target-directed action. In the present review, we explore the properties of some of the most common biodegradable polymers used in tissue engineering applications and biomolecule delivery systems and highlight their most important uses.

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

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

Self-disinfecting surfaces and infection control

According to World Health Organization, every year in the European Union, 4 million patients acquire a healthcare associated infection. Even though some microorganisms represent no threat to healthy people, hospitals harbor different levels of immunocompetent individuals, namely patients receiving immunosuppressors, with previous infections, or those with extremes of age (young children and elderly), requiring the implementation of effective control measures. Public spaces have also been found an important source of infectious disease outbreaks due to poor or none infection control measures applied. In both places, surfaces play a major role on microorganisms' propagation, yet they are very often neglected, with very few guidelines about efficient cleaning measures and microbiological assessment available. To overcome surface contamination problems, new strategies are being designed to limit the microorganisms' ability to survive over surfaces and materials. Surface modification and/or functionalization to prevent contamination is a hot-topic of research and several different approaches have been developed lately. Surfaces with anti-adhesive properties, with incorporated antimicrobial substances or modified with biological active metals are some of the strategies recently proposed. This review intends to summarize the problems associated with contaminated surfaces and their importance on infection spreading, and to present some of the strategies developed to prevent this public health problem, namely some already being commercialized.

Development and Fabrication of Vapor Cross-Linked Hyaluronan-Polyethylene Interpenetrating Polymer Network as a Biomaterial

Flexible heart valve leaflets made from hyaluronan-enhanced linear low-density polyethylene interpenetrating polymeric network (HA-LLDPE IPN) films have been shown to provide good hemodynamics, but the resulting surfaces were not consistent; therefore, the present work tries to mitigate this problem by developing a vapor cross-linked HA-LLDPE IPN. Herein, the HA-LLDPE fabrication process is studied, and its parameters are varied to assess their effects on the IPN formation. Thermal analysis and gas chromatography-mass spectrometry were used to quantify the effects of different treatment conditions on material properties. Water contact angle goniometry, infrared spectroscopy, and toluidine blue O (TBO) staining were used to characterize the surface of the HA-LLDPE IPN. The results show that a hydrophilic surface is formed on HA-LLDPE, which is indicative of HA. HA surface density data from TBO staining show consistent HA distribution on the surface. The IPN fabrication process does not affect the tensile properties that make LLDPE an attractive material for use in flexible heart valve leaflets. The 28 day in vitro biological assays show HA-LLDPE to be noncytotoxic and resistant to enzymatic degradation. The HA-LLDPE showed less platelet adhesion and caused less platelet activation than the plain LLDPE or tissue culture polystyrene. All of the results indicate that vapor cross-linked HA-LLDPE IPN is a promising material for use as flexible leaflets for heart valve replacements.

Modular Chamber Assembled with Cell-Replicated Surface for Capture of Cancer Cells

The capture of circulating tumor cells (CTCs) is mainly carried out with a small volume of blood using magnetic nanoparticles and complex microfluidics. In this study, we propose a CTC-capture apparatus based on a modular design and called this apparatus as the CTC chamber. Distinct from other CTC-capture apparatuses, the capacity of the CTC chamber could be altered by varying the number of CTC-capture modules to accommodate the different volumes of blood sample. The core component of the CTC-capture module was a polydimethylsiloxane (PDMS) film with cell-replicated topological structure and anti-EpCAM antibody coating. Both synergistic roles can enhance the capture yield of cancer cells. Furthermore, the CTC chamber was assembled with one or three CTC-capture modules for the capture of cancer cells from spiked blood samples representing late-stage (3 mL of blood, 10 cancer cells mL^-1) or middle-early stage (9 mL of blood, 1 cancer cell mL^-1) cancer. The results showed that high capture yield (EpCAM-positive, ∼80%; EpCAM-negative, ∼65%) and purity (EpCAM-positive, ∼90%; EpCAM-negative, ∼80%) could be obtained within 1 h. This economic and facile CTC chamber could therefore open up opportunities for designing the next-generation CTC detection devices suitable for the diagnosis of different stages of cancer.

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

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

Engineering Thiolated Surfaces with Polyelectrolyte Multilayers

Interfaces bearing firmly attached thiol groups are useful for many applications requiring the versatile and facile chemistry of the -SH functionality. In this work, rugged ultrathin films were prepared on substrates using layer-by-layer assembly. The surface of these smooth films was capped with a co-polymer containing benzyl mercaptan units. The utility of this coating was illustrated by three applications. First, thiol-ene "click" chemistry was used to introduce the Arg-Gly-Asp (RGD) adhesive peptide sequence on a surface that otherwise resisted good adhesion of fibroblasts. This treatment promoted cell adhesion and spreading. Similar Michael addition chemistry was employed to attach poly(ethylene glycol) to the surface, which reduced fouling by (adhesion of) serum albumin. Finally, the affinity of gold for -SH was exploited by depositing a layer of gold nanoparticles on the thiolated surface or by evaporating a tenacious film of gold without using the classical chromium "primer" layer.

Albumin conjugates and assemblies as versatile bio-functional additives and carriers for biomedical applications

As the most abundant plasma protein, serum albumin has been extensively studied and employed for therapeutic applications. Despite its direct clinical use for the maintenance of blood homeostasis in various medical conditions, this review exclusively summarizes and discusses albumin-based bio-conjugates and assemblies as versatile bio-functional additives and carriers in biomedical applications. As one of the smallest-sized proteins in the human body, albumin is physiochemically stable and biochemically inert. Moreover, albumin is also endowed with abundant specific binding sites for numerous therapeutic compounds, which also endow it with superior bioactivities. Firstly, due to its small size and binding specificity, albumin alone or its derived assemblies can be utilized as competent drug carriers, which can deliver drugs through the enhanced permeability and retention (EPR) effect or actively target lesion sites through binding with gp60 and secreted protein acidic and rich in cysteine (SPARC) in tumor sites. Furthermore, its biochemical stability and inertness make it a safe and biocompatible coating material for use in biomedical applications. Albumin-based surface modifying additives can be used to functionalize both macro substrates (e.g. surfaces of medical devices or implants) and nanoparticle surfaces (e.g. drug carriers and imaging contrast agents). In this review, we elaborate on the synthesis and applications of albumin-based bio-functional coatings and drug carriers, respectively.

Hyaluronic Acid in the Third Millennium

Since its first isolation in 1934, hyaluronic acid (HA) has been studied across a variety of research areas. This unbranched glycosaminoglycan consisting of repeating disaccharide units of N-acetyl-d-glucosamine and d-glucuronic acid is almost ubiquitous in humans and in other vertebrates. HA is involved in many key processes, including cell signaling, wound reparation, tissue regeneration, morphogenesis, matrix organization and pathobiology, and has unique physico-chemical properties, such as biocompatibility, biodegradability, mucoadhesivity, hygroscopicity and viscoelasticity. For these reasons, exogenous HA has been investigated as a drug delivery system and treatment in cancer, ophthalmology, arthrology, pneumology, rhinology, urology, aesthetic medicine and cosmetics. To improve and customize its properties and applications, HA can be subjected to chemical modifications: conjugation and crosslinking. The present review gives an overview regarding HA, describing its history, physico-chemical, structural and hydrodynamic properties and biology (occurrence, biosynthesis (by hyaluronan synthases), degradation (by hyaluronidases and oxidative stress), roles, mechanisms of action and receptors). Furthermore, both conventional and recently emerging methods developed for the industrial production of HA and its chemical derivatization are presented. Finally, the medical, pharmaceutical and cosmetic applications of HA and its derivatives are reviewed, reporting examples of HA-based products that currently are on the market or are undergoing further investigations.

Peptide-Functionalized Polyurethane Coatings Prepared via Grafting-To Strategy to Selectively Promote Endothelialization

Endothelialization, formation of endothelial cells (ECs) layer on cardiovascular implant surface, is considered an ideal approach to prevent restenosis (renarrowing of blood vessel mainly due to the accumulation of proliferated vascular smooth muscle cells, SMCs) and thrombosis. In this study, the possibility of using polyurethane (PU) as a coating platform for functionalization with peptide to enhance endothelialization on implants is explored. PUs are synthesized through metal-free organocatalytic polymerization followed by chemical conjugation with an EC-specific REDV peptide through thiol-ene reaction. Meanwhile, the free isocyanate groups of PU allow for covalent grafting of REDV-functionalized PU (PU/REDV) to silanize implant materials (nitinol and PET). PU/REDV coating with peptide grafting density of ≈2 nmol cm^-2 selectively accommodates primary human umbilical vein ECs (HUVECs) and retards spreading of primary human umbilical artery SMCs (HUASMCs). In addition, a layer of HUVECs is formed within 3 d on PU/REDV-coated surfaces, while proliferation of HUASMCs is inhibited. The selectivity is further confirmed by coculture of HUVECs and HUASMCs. Moreover, the PU/REDV-coated surfaces are less thrombogenic as evidenced by reduced number and activity of adhered platelets. Therefore, PU/REDV can be potentially used as a coating of cardiovascular implants to prevent restenosis and thrombosis by promoting endothelialization.

N-acetylcysteine-functionalized coating avoids bacterial adhesion and biofilm formation

N-acetyl cysteine (NAC) is an FDA-approved drug clinically applied on a broad range of pathologies. Further research has been conducted with this drug to benefit from its antimicrobial activity potential. However, NAC has a very short half-life and therefore strategies that accomplish high local concentrations would be beneficial. In this study, covalent immobilization of NAC was performed, in order to obtain long-lasting high local concentration of the drug onto a chitosan(Ch)-derived implant-related coating. For the development of NAC-functionalized Ch films, water-based carbodiimide chemistry was applied to avoid the use of toxic organic solvents. Here we report the optimization steps performed to immobilize NAC onto the surface of pre-prepared Ch coatings, to ensure full exposure of NAC. Surface characterization using ellipsometry, water contact angle measurements and X-ray photoelectron spectroscopy (XPS), demonstrated the success of NAC immobilization at 4 mg/mL. Quartz crystal microbalance with dissipation (QCM-D) demonstrated that surface immobilized NAC decreases protein adsorption to Ch coatings. Biological studies confirmed that immobilized NAC4 avoids methicillin-resistant Staphylococcus aureus adhesion to Ch coating, impairing biofilm formation, without inducing cytotoxic effects. This is particularly interesting towards further developments as a prevention coating.

Functionalization of electrospun polymeric wound dressings with antimicrobial peptides

Wound dressings have evolved considerably since ancient times. Modern dressings are now important systems that combine the physical and biochemical properties of natural and synthetic polymers with active compounds that are beneficial to wound healing. Antimicrobial peptides (AMPs) are the most recent addition to these systems. These aim to control the microbial proliferation and colonization of pathogens and to modulate the host's immune response. In the last decade, electrospun wound dressings have been extensively studied and the electrospinning technique recognized as an efficient approach for the production of nanoscale fibrous mats. The control of the electrospinning processing parameters, the selection of the polymer and AMPs, and the definition of the most appropriate AMPs' functionalization method contribute to the successful treatment of acute and chronic wounds. Although the use of electrospinning in wound dressings' production has been previously reviewed, the increased development of AMPs and the establishment of functionalization methods for wound dressings over recent years has increased the need for such research. In the present review, we approach all these subjects and reveal the promising therapeutic potential of wound dressings functionalized with AMPs.

Introduction of anti-fouling coatings at the surface of supramolecular elastomeric materials via post-modification of reactive supramolecular additives

A covalent anti-fouling is introduced at the surface of supramolecular ureidopyrimidinone (UPy) based materials to prevent both protein and cell adhesion.