Endogenous Nitric Oxide-Releasing Microgel Coating Prevents Clot Formation on Oxygenator Fibers Exposed to In Vitro Blood Flow

Material-specific binding peptides empower sustainable innovations in plant health, biocatalysis, medicine and microplastic quantification

Material-binding peptides (MBPs) have emerged as a diverse and innovation-enabling class of peptides in applications such as plant-/human health, immobilization of catalysts, bioactive coatings, accelerated polymer degradation and analytics for micro-/nanoplastics quantification. Progress has been fuelled by recent advancements in protein engineering methodologies and advances in computational and analytical methodologies, which allow the design of, for instance, material-specific MBPs with fine-tuned binding strength for numerous demands in material science applications. A genetic or chemical conjugation of second (biological, chemical or physical property-changing) functionality to MBPs empowers the design of advanced (hybrid) materials, bioactive coatings and analytical tools. In this review, we provide a comprehensive overview comprising naturally occurring MBPs and their function in nature, binding properties of short man-made MBPs (<20 amino acids) mainly obtained from phage-display libraries, and medium-sized binding peptides (20-100 amino acids) that have been reported to bind to metals, polymers or other industrially produced materials. The goal of this review is to provide an in-depth understanding of molecular interactions between materials and material-specific binding peptides, and thereby empower the use of MBPs in material science applications. Protein engineering methodologies and selected examples to tailor MBPs toward applications in agriculture with a focus on plant health, biocatalysis, medicine and environmental monitoring serve as examples of the transformative power of MBPs for various industrial applications. An emphasis will be given to MBPs' role in detecting and quantifying microplastics in high throughput, distinguishing microplastics from other environmental particles, and thereby assisting to close an analytical gap in food safety and monitoring of environmental plastic pollution. In essence, this review aims to provide an overview among researchers from diverse disciplines in respect to material-(specific) binding of MBPs, protein engineering methodologies to tailor their properties to application demands, re-engineering for material science applications using MBPs, and thereby inspire researchers to employ MBPs in their research.

Electrospun Membranes Based on Quaternized Polysulfones: Rheological Properties-Electrospinning Mechanisms Relationship

Composite membranes based on a polymer mixture solution of quaternized polysulfone (PSFQ), cellulose acetate phthalate (CAP), and polyvinylidene fluoride (PVDF) for biomedical applications were successfully obtained through the electrospinning technique. To ensure the polysulfone membranes' functionality in targeted applications, the selection of electrospinning conditions was essential. Moreover, understanding the geometric characteristics and morphology of fibrous membranes is crucial in designing them to meet the performance standards necessary for future biomedical applications. Thus, the viscosity of the solutions used in the electrospinning process was determined, and the morphology of the electrospun membranes was examined using scanning electron microscopy (SEM). Investigations on the surfaces of electrospun membranes based on water vapor sorption data have demonstrated that their surface properties dictate their biological ability more than their specific surfaces. Furthermore, in order to understand the different macromolecular rearrangements of membrane structures caused by physical interactions between the polymeric chains as well as by the orientation of functional groups during the electrospinning process, Fourier transform infrared (FTIR) spectroscopy was used. The applicability of composite membranes in the biomedical field was established by bacterial adhesion testing on the surface of electrospun membranes using Escherichia coli and Staphylococcus aureus microorganisms. The biological experiments conducted establish a foundation for future applications of these membranes and validate their effectiveness in specific fields.

Endothelium-Mimicking Bilayer Vascular Grafts with Dual-Releasing of NO/H2S for Anti-Inflammation and Anticalcification

Vascular complications caused by diabetes impair the activities of endothelial nitric oxide synthase (eNOS) and cystathionine γ-lyase (CSE), resulting in decreased physiological levels of nitric oxide (NO) and hydrogen sulfide (H2S). The low bioavailability of NO and H2S hinders the endothelialization of vascular grafts. In this study, endothelium-mimicking bilayer vascular grafts were designed with spatiotemporally controlled dual releases of NO and H2S for in situ endothelialization and angiogenesis. Keratin-based H2S donor was synthesized and electrospun with poly(l-lactide-co-ε-caprolactone) (PLCL) as the outer layer of the graft to release H2S. Hyaluronic acid, one of the major glycosaminoglycans in endothelial glycocalyx, was complexed with Cu ions as the inner layer to mimic glutathione peroxidase (GPx) and maintain long-term physiological NO flux. The synergistic effects of NO and H2S of bilayer grafts selectively promoted the regeneration and migration of human umbilical vascular endothelial cells (HUVECs), while inhibiting the overproliferation of human umbilical artery smooth muscle cells (HUASMCs). Bilayer grafts could effectively prevent vascular calcification, reduce inflammation, and alleviate endothelial dysfunction. The in vivo study in a rat abdominal aorta replacement model for 1 month showed that the graft had a good patency rate and had potential for vascular remodeling in situ.

Polymeric Based Hydrogel Membranes for Biomedical Applications

The development of biomedical applications is a transdisciplinary field that in recent years has involved researchers from chemistry, pharmacy, medicine, biology, biophysics, and biomechanical engineering. The fabrication of biomedical devices requires the use of biocompatible materials that do not damage living tissues and have some biomechanical characteristics. The use of polymeric membranes, as materials meeting the above-mentioned requirements, has become increasingly popular in recent years, with outstanding results in tissue engineering, for regeneration and replenishment of tissues constituting internal organs, in wound healing dressings, and in the realization of systems for diagnosis and therapy, through the controlled release of active substances. The biomedical application of hydrogel membranes has had little uptake in the past due to the toxicity of cross-linking agents and to the existing limitations regarding gelation under physiological conditions, but now it is proving to be a very promising field This review presents the important technological innovations that the use of membrane hydrogels has promoted, enabling the resolution of recurrent clinical problems, such as post-transplant rejection crises, haemorrhagic crises due to the adhesion of proteins, bacteria, and platelets on biomedical devices in contact with blood, and poor compliance of patients undergoing long-term drug therapies.

Commercial and novel anticoagulant ECMO coatings: a review

Extracorporeal membrane oxygenation (ECMO) is an invasive and last-resort treatment for circulatory and respiratory failure. Prolonged ECMO support can disrupt the coagulation and anticoagulation systems in a patient, leading to adverse consequences, such as bleeding and thrombosis. To address this problem, anticoagulation coatings have been developed for use in ECMO circuits. This article reviews commonly used commercial and novel anticoagulant coatings developed in recent years and proposes a new classification of coatings based on the current state. While commercial coatings have been used clinically for decades, this review focuses on comparing the effectiveness and stability of coatings to support clinical selections. Furthermore, novel anticoagulation coatings often involve complex mechanisms and elaborate design strategies, and this review summarises representative studies on mainstream anticoagulation coatings to provide a point of reference for future studies.

A dual-action nitric oxide-releasing slippery surface for extracorporeal organ support: Dynamic in vitro hemocompatibility evaluation

Numerous biomaterials have been developed for application in blood-contacting medical devices to prevent thrombosis; however, few materials have been applied to full-scale devices and evaluated for hemocompatibility under clinical blood flow conditions. We applied a dual-action slippery liquid-infused (LI) nitric oxide (NO)-releasing material modification (LINO) to full-scale blood circulation tubing for extracorporeal lung support and evaluated the tubing ex vivo using swine whole blood circulated for 6 h at a clinically relevant flow. LINO tubing was compared to unmodified tubing (CTRL) and isolated LI and NO-releasing modifications (n = 9/group). The primary objective was to evaluate safety and blood compatibility of this approach, prior to progression to in vivo testing of efficacy in animal models. The secondary objective was to evaluate coagulation outcomes relevant to hemocompatibility. No untoward effects of the coating, such as elevated methemoglobin fraction, were observed. Additionally, LINO delayed platelet loss until 6 h versus the reduction in platelet count in CTRL at 3 h. At 6 h, LINO significantly reduced the concentration of platelets in an activated P-selectin expressing state versus CTRL (32 ± 1% decrease, p = .02). Blood clot deposition was significantly reduced on LINO blood pumps (p = .007) and numerically reduced on tubing versus CTRL. Following blood exposure, LINO tubing continued to produce a measurable NO-flux (0.20 ± 0.06 × 10^-10  mol cm^-2  min^-1 ). LINO is a potential solution to reduce circuit-related bleeding and clotting during extracorporeal organ support, pending future extended testing in vivo using full-scale extracorporeal lung support devices.

Bioimpedance Analysis as Early Predictor for Clot Formation Inside a Blood-Perfused Test Chamber: Proof of Concept Using an In Vitro Test-Circuit

Clot formation inside a membrane oxygenator (MO) due to blood-to-foreign surface interaction represents a frequent complication during extracorporeal membrane oxygenation. Since current standard monitoring methods of coagulation status inside the MO fail to detect clot formation at an early stage, reliable sensors for early clot detection are in demand to reduce associated complications and adverse events. Bioimpedance analysis offers a monitoring concept by integrating sensor fibers into the MO. Herein, the feasibility of clot detection via bioimpedance analysis is evaluated. A custom-made test chamber with integrated titanium fibers acting as sensors was perfused with heparinized human whole blood in an in vitro test circuit until clot formation occurred. The clot detection capability of bioimpedance analysis was directly compared to the pressure difference across the test chamber (ΔP-TC), analogous to the measurement across MOs (ΔP-MO), the clinical gold standard for clot detection. We found that bioimpedance measurement increased significantly 8 min prior to a significant increase in ΔP-TC, indicating fulminant clot formation. Experiments without clot formation resulted in a lack of increase in bioimpedance or ΔP-TC. This study shows that clot detection via bioimpedance analysis under flow conditions in a blood-perfused test chamber is generally feasible, thus paving the way for further investigation.

Biomedical applications of solid-binding peptides and proteins

Over the past decades, solid-binding peptides (SBPs) have found multiple applications in materials science. In non-covalent surface modification strategies, solid-binding peptides are a simple and versatile tool for the immobilization of biomolecules on a vast variety of solid surfaces. Especially in physiological environments, SBPs can increase the biocompatibility of hybrid materials and offer tunable properties for the display of biomolecules with minimal impact on their functionality. All these features make SBPs attractive for the manufacturing of bioinspired materials in diagnostic and therapeutic applications. In particular, biomedical applications such as drug delivery, biosensing, and regenerative therapies have benefited from the introduction of SBPs. Here, we review recent literature on the use of solid-binding peptides and solid-binding proteins in biomedical applications. We focus on applications where modulating the interactions between solid materials and biomolecules is crucial. In this review, we describe solid-binding peptides and proteins, providing background on sequence design and binding mechanism. We then discuss their application on materials relevant for biomedicine (calcium phosphates, silicates, ice crystals, metals, plastics, and graphene). Although the limited characterization of SBPs still represents a challenge for their design and widespread application, our review shows that SBP-mediated bioconjugation can be easily introduced into complex designs and on nanomaterials with very different surface chemistries.

Polymeric Membranes for Biomedical Applications

Polymeric membranes are selective materials used in a wide range of applications that require separation processes, from water filtration and purification to industrial separations. Because of these materials' remarkable properties, namely, selectivity, membranes are also used in a wide range of biomedical applications that require separations. Considering the fact that most organs (apart from the heart and brain) have separation processes associated with the physiological function (kidneys, lungs, intestines, stomach, etc.), technological solutions have been developed to replace the function of these organs with the help of polymer membranes. This review presents the main biomedical applications of polymer membranes, such as hemodialysis (for chronic kidney disease), membrane-based artificial oxygenators (for artificial lung), artificial liver, artificial pancreas, and membranes for osseointegration and drug delivery systems based on membranes.

Hemocompatibility challenge of membrane oxygenator for artificial lung technology

The artificial lung (AL) technology is one of the membrane-based artificial organs that partly augments lung functions, i.e. blood oxygenation and CO₂ removal. It is generally employed as an extracorporeal membrane oxygenation (ECMO) device to treat acute and chronic lung-failure patients, and the recent outbreak of the COVID-19 pandemic has re-emphasized the importance of this technology. The principal component in AL is the polymeric membrane oxygenator that facilitates the O₂/CO₂ exchange with the blood. Despite the considerable improvement in anti-thrombogenic biomaterials in other applications (e.g., stents), AL research has not advanced at the same rate. This is partly because AL research requires interdisciplinary knowledge in biomaterials and membrane technology. Some of the promising biomaterials with reasonable hemocompatibility - such as emerging fluoropolymers of extremely low surface energy - must first be fabricated into membranes to exhibit effective gas exchange performance. As AL membranes must also demonstrate high hemocompatibility in tandem, it is essential to test the membranes using in-vitro hemocompatibility experiments before in-vivo test. Hence, it is vital to have a reliable in-vitro experimental protocol that can be reasonably correlated with the in-vivo results. However, current in-vitro AL studies are unsystematic to allow a consistent comparison with in-vivo results. More specifically, current literature on AL biomaterial in-vitro hemocompatibility data are not quantitatively comparable due to the use of unstandardized and unreliable protocols. Such a wide gap has been the main bottleneck in the improvement of AL research, preventing promising biomaterials from reaching clinical trials. This review summarizes the current state-of-the-art and status of AL technology from membrane researcher perspectives. Particularly, most of the reported in-vitro experiments to assess AL membrane hemocompatibility are compiled and critically compared to suggest the most reliable method suitable for AL biomaterial research. Also, a brief review of current approaches to improve AL hemocompatibility is summarized. STATEMENT OF SIGNIFICANCE: The importance of Artificial Lung (AL) technology has been re-emphasized in the time of the COVID-19 pandemic. The utmost bottleneck in the current AL technology is the poor hemocompatibility of the polymer membrane used for O₂/CO₂ gas exchange, limiting its use in the long-term. Unfortunately, most of the in-vitro AL experiments are unsystematic, irreproducible, and unreliable. There are no standardized in-vitro hemocompatibility characterization protocols for quantitative comparison between AL biomaterials. In this review, we tackled this bottleneck by compiling the scattered in-vitro data and suggesting the most suitable experimental protocol to obtain reliable and comparable hemocompatibility results. To the best of our knowledge, this is the first review paper focusing on the hemocompatibility challenge of AL technology.

The effects of protein corona on in vivo fate of nanocarriers

With the emerging advances in utilizing nanocarriers for biomedical applications, a molecular-level understanding of the in vivo fate of nanocarriers is necessary. After administration into human fluids, nanocarriers can attract proteins onto their surfaces, forming an assembled adsorption layer called protein corona (PC). The formed PC can influence the physicochemical properties and subsequently determine nanocarriers' biological behaviors. Therefore, an in-depth understanding of the features and effects of the PC on the nanocarriers' surface is the first and most important step towards controlling their in vivo fate. This review introduces fundamental knowledge such as the definition, formation, composition, conformation, and characterization of the PC, emphasizing the in vivo environmental factors that control the PC formation. The effect of PC on the physicochemical properties and thus biological behaviors of nanocarriers was then presented and thoroughly discussed. Finally, we proposed the design strategies available for engineering PC onto nanocarriers to manipulate them with the desired surface properties and achieve the best biomedical outcomes.