Control of Anti-Thrombogenic Properties: Surface-Induced Self-Assembly of Fibrinogen Fibers

Precise antibiotic delivery to the lung infection microenvironment boosts the treatment of pneumonia with decreased gut dysbiosis

Bacterial pneumonia is a common disease with significant health risks. However, the overuse antibiotics in clinics face challenges such as inadequate targeting and limited drug utilization, leading to drug resistance and gut dysbiosis. Herein, a dual-responsive lung inflammatory tissue targeted nanoparticle (LITTN), designed for targeting lung tissue and bacteria, is screened from a series of prepared nanoparticles consisting of permanent cationic lipids, acid-responsive lipids, and reactive oxygen species-responsive and phenylboronic acid-modified lipids with different surface properties. Such nanoparticle is further verified to enhance the adsorption of vitronectin in serum. Additionally, the optimized nanoparticle exhibits more positive charge and coordination of boric acid with cis-diol in the infected microenvironment, facilitating electrostatic interactions with bacteria and biofilm penetration. Importantly, the antibacterial efficiency of dual-responsive rifampicin-loaded LITTN (Rif@LITTN) against methicillin-resistant staphylococcus aureus is 10 times higher than that of free rifampicin. In a mouse model of bacterial pneumonia, the intravenous administration of Rif@LITTN could precisely target the lungs, localize in the lung infection microenvironment, and trigger the responsive release of rifampicin, thereby effectively alleviating lung inflammation and reducing damage. Notably, the targeted delivery of rifampicin helps protect against antibiotic-induced changes in the gut microbiota. This study establishes a new strategy for precise delivery to the lung-infected microenvironment, promoting treatment efficacy while minimizing the impact on gut microbiota. STATEMENT OF SIGNIFICANCE: Intravenous antibiotics play a critical role in clinical care, particularly for severe bacterial pneumonia. However, the inability of antibiotics to reach target tissues causes serious side effects, including liver and kidney damage and intestinal dysbiosis. Therefore, achieving precise delivery of antibiotics is of great significance. In this study, we developed a novel lung inflammatory tissue-targeted nanoparticle that could target lung tissue after intravenous administration and then target the inflammatory microenvironment to trigger dual-responsive antibiotics release to synergistically treat pneumonia while maintaining the balance of gut microbiota and reducing the adverse effects of antibiotics. This study provides new ideas for targeted drug delivery and reference for clinical treatment of pneumonia.

Lung-selective nucleic acid vectors generated by in vivo lung-targeting-protein decoration of polyplexes

Nucleic acid drugs show immense therapeutic potential, but achieving selective organ targeting (SORT) for pulmonary disease therapy remains a formidable challenge due to the high mortality rate caused by pulmonary embolism via intravenous administration or the mucus barrier in the respiratory tract via nebulized delivery. To meet this important challenge, we propose a new strategy to prepare lung-selective nucleic-acid vectors generated by in vivo decoration of lung-targeting proteins on bioreducible polyplexes. First, we synthesized polyamidoamines, named pabol and polylipo, to encapsulate and protect nucleic acids, forming polyamidoamines/mRNA polyplexes. Second, bovine serum albumin (BSA) was coated on the surface of these polyplexes, called BSA@polyplexes, including BSA@pabol polyplexes and BSA@polylipo polyplexes, to neutralize excess positive charge, thereby enhancing biosafety. Finally, after subcutaneous injection, proteins, especially vitronectin and fibronectins, attached to the polyplexes, resulting in the formation of lung-selective nucleic-acid vectors that achieve efficient lung targeting.

The impact of, and expectations for, lipid nanoparticle technology: From cellular targeting to organelle targeting

The success of mRNA vaccines against COVID-19 has enhanced the potential of lipid nanoparticles (LNPs) as a system for the delivery of mRNA. In this review, we describe our progress using a lipid library to engineer ionizable lipids and promote LNP technology from the viewpoints of safety, controlled biodistribution, and mRNA vaccines. These advancements in LNP technology are applied to cancer immunology, and a potential nano-DDS is constructed to evaluate immune status that is associated with a cancer-immunity cycle that includes the sub-cycles in tumor microenvironments. We also discuss the importance of the delivery of antigens and adjuvants in enhancing the cancer-immunity cycle. Recent progress in NK cell targeting in cancer immunotherapy is also introduced. Finally, the impact of next-generation DDS technology is explained using the MITO-Porter membrane fusion-based delivery system for the organelle targeting of the mitochondria. We introduce a successful example of the MITO-Porter used in a cell therapeutic strategy to treat cardiomyopathy.

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

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

The role of protein corona on nanodrugs for organ-targeting and its prospects of application

Nowadays, nanodrugs become a hotspot in the high-end medical field. They have the ability to deliver drugs to reach their destination more effectively due to their unique properties and flexible functionalization. However, the fate of nanodrugs in vivo is not the same as those presented in vitro, which indeed influenced their therapeutic efficacy in vivo. When entering the biological organism, nanodrugs will first come into contact with biological fluids and then be covered by some biomacromolecules, especially proteins. The proteins adsorbed on the surface of nanodrugs are known as protein corona (PC), which causes the loss of prospective organ-targeting abilities. Fortunately, the reasonable utilization of PC may determine the organ-targeting efficiency of systemically administered nanodrugs based on the diverse expression of receptors on cells in different organs. In addition, the nanodrugs for local administration targeting diverse lesion sites will also form unique PC, which plays an important role in the therapeutic effect of nanodrugs. This article introduced the formation of PC on the surface of nanodrugs and summarized the recent studies about the roles of diversified proteins adsorbed on nanodrugs and relevant protein for organ-targeting receptor through different administration pathways, which may deepen our understanding of the role that PC played on organ-targeting and improve the therapeutic efficacy of nanodrugs to promote their clinical translation.

Myeloperoxidase-induced fibrinogen unfolding and clotting

Due to its unique properties and high biomedical relevance fibrinogen is a promising protein for the development of various matrixes and scaffolds for biotechnological applications. Fibrinogen molecules may form extensive clots either upon specific cleavage by thrombin or in thrombin-free environment, for example, in the presence of different salts. Here, we report the novel type of non-conventional fibrinogen clot formation, which is mediated by myeloperoxidase and takes place even at low fibrinogen concentrations (<0.1 mg/ml). We have revealed fibrillar nature of myeloperoxidase-mediated fibrinogen clots, which differ morphologically from fibrin clots. We have shown that fibrinogen clotting is mediated by direct interaction of myeloperoxidase molecules with the outer globular regions of fibrinogen molecules followed by fibrinogen unfolding from its natural trinodular to a fibrillar structure. We have demonstrated a major role of the Debye screening effect in regulating of myeloperoxidase-induced fibrinogen clotting, which is facilitated by small ionic strength. While fibrinogen in an aqueous solution with myeloperoxidase undergoes changes, the enzymatic activity of myeloperoxidase is not inhibited in excess of fibrinogen. The obtained results open new insights into fibrinogen clotting, give new possibilities for the development of fibrinogen-based functional biomaterials, and provide the novel concepts of protein unfolding.

Novel characteristics of soluble fibrin: hypercoagulability and acceleration of blood sedimentation rate mediated by its generation of erythrocyte-linked fibers

Soluble fibrin (SF) in blood consists of monomers lacking both fibrinopeptides A with a minor population in multimeric clusters. It is a substantial component of isolated fibrinogen (fg), which spontaneously self-assembles into protofibrils progressing to fibers at sub-physiologic temperatures, a process enhanced by adsorption to hydrophobic and some metal surfaces. Comparisons of SF-rich (FR) and SF-depleted (FD) fg isolates disclosed distinct molecular imprints of each via an adsorption/desorption procedure using gold surfaced silica microplates. Accelerated plasminogen activator-induced lysis and decreased stiffness (G′) of thrombin-induced FR fg clots were revealed by thomboelastography. Erythrocyte sedimentation (ESR) in afibrinogenemic plasma (Hematocrit 25–33%) was accelerated by FR fg nearly threefold that of FD fg. Stained smears disclosed frequent rouleaux formations and fibers linking stacked erythrocytes in contrast to no rouleaux by FD fg. Rouleaux formations were more pronounced at 4 °C than at ambient temperatures and at fiber-membrane contacts displayed irregular, knobby membrane contours. One of several FR fg isolates also displayed incomplete fiber networks in cell-free areas. What is more, pre-mixing FR fg with each of three monoclonal IgG anti-fg antibodies at 1.5 mol/mol fg, that inhibited fibrin polymerization, prevented rouleaux formation save occasional 2–4 erythrocyte aggregates. We conclude that spontaneously generated SF fibers bound to erythrocytes forming intercellular links culminating in rouleaux formation and ensuing ESR acceleration which in clinical settings reflects hypercoagulability. Also, the results can explain the reported fg binding to erythrocytes via ligands such as CD47, stable in vivo RBC aggregates in capillaries, and red areas of pathologic thrombi.

Lung-selective mRNA delivery of synthetic lipid nanoparticles for the treatment of pulmonary lymphangioleiomyomatosis

Safe and efficacious systemic delivery of messenger RNA (mRNA) to specific organs and cells in vivo remains the major challenge in the development of mRNA-based therapeutics. Targeting of systemically administered lipid nanoparticles (LNPs) coformulated with mRNA has largely been confined to the liver and spleen. Using a library screening approach, we identified that N-series LNPs (containing an amide bond in the tail) are capable of selectively delivering mRNA to the mouse lung, in contrast to our previous discovery that O-series LNPs (containing an ester bond in the tail) that tend to deliver mRNA to the liver. We analyzed the protein corona on the liver- and lung-targeted LNPs using liquid chromatography-mass spectrometry and identified a group of unique plasma proteins specifically absorbed onto the surface that may contribute to the targetability of these LNPs. Different pulmonary cell types can also be targeted by simply tuning the headgroup structure of N-series LNPs. Importantly, we demonstrate here the success of LNP-based RNA therapy in a preclinical model of lymphangioleiomyomatosis (LAM), a destructive lung disease caused by loss-of-function mutations in the Tsc2 gene. Our lung-targeting LNP exhibited highly efficient delivery of the mouse tuberous sclerosis complex 2 (Tsc2) mRNA for the restoration of TSC2 tumor suppressor in tumor and achieved remarkable therapeutic effect in reducing tumor burden. This research establishes mRNA LNPs as a promising therapeutic intervention for the treatment of LAM.

Polysaccharide-Protein Multilayers Based on Chitosan-Fibrinogen Assemblies for Cardiac Cell Engineering

The cell and tissue culture substrates play a pivotal role in the regulation of cell-matrix and cell-cell interactions. The surface properties of the materials control a wide variety of cell functions. Amongst various methods, layer-by-layer (LbL) assembly is a versatile surface coating technique for creating controllable bio-coatings. Here, polysaccharide/protein multilayers are proposed, which are fabricated by immersive LbL assembly and based on the chitosan/fibrinogen pair for improving the adhesion and spreading of cardiomyocytes. Two approaches in LbL assembly are employed for clarifying the effect of the bilayers order and their concentration on cardiomyocytes viability and morphology. Fourier transform infrared spectroscopy (FTIR) measurements show that the adsorption of the biopolymers is enhanced during the LbL deposition in a synergistic manner. Contact angle measurements indicate that the multilayers are alternating from less to more hydrophilic behavior depending on the biopolymer that is added last. Confocal microscopy with immunostained fibrinogen reveals that the amount of the protein is higher when the concentration of the immersion solution is increased, however, for low solution concentration it is speculated that interdigitation between the separate biopolymer layers takes place. This work motivates the use of fibrinogen in polysaccharide/protein multilayers for enhanced cytocompatibility in cardiac tissue engineering.

Fibers Generated by Plasma Des-AA Fibrin Monomers and Protofibril/Fibrinogen Clusters Bind Platelets: Clinical and Nonclinical Implications

Objective  Soluble fibrin (SF) is a substantial component of plasma fibrinogen (fg), but its composition, functions, and clinical relevance remain unclear. The study aimed to evaluate the molecular composition and procoagulant function(s) of SF. Materials and Methods  Cryoprecipitable, SF-rich (FR) and cryosoluble, SF-depleted (FD) fg isolates were prepared and adsorbed on one hydrophilic and two hydrophobic surfaces and scanned by atomic force microscopy (AFM). Standard procedures were used for fibrin polymerization, crosslinking by factor XIII, electrophoresis, and platelet adhesion. Results  Relative to FD fg, thrombin-induced polymerization of FR fg was accelerated and that induced by reptilase was markedly delayed, attributable to its decreased (fibrinopeptide A) FpA. FR fg adsorption to each surface yielded polymeric clusters and co-cryoprecipitable solitary monomers. Cluster components were crosslinked by factor XIII and comprised ≤21% of FR fg. In contrast to FD fg, FR fg adsorption on hydrophobic surfaces resulted in fiber generation enabled by both clusters and solitary monomers. This began with numerous short protofibrils, which following prolonged adsorption increased in number and length and culminated in surface-linked three-dimensional fiber networks that bound platelets. Conclusion  The abundance of adsorbed protofibrils resulted from (1) protofibril/fg clusters whose fg was dissociated during adsorption, and (2) adsorbed des-AA monomers that attracted solution counterparts initiating protofibril assembly and elongation by their continued incorporation. The substantial presence of both components in transfused plasma and cryoprecipitate augments hemostasis by accelerating thrombin-induced fibrin polymerization and by tightly anchoring the resulting clot to the underlying wound or to other abnormal vascular surfaces.

Self-assembled fibrinogen nanofibers support fibroblast adhesion and prevent E. coli infiltration

Fibrinogen nanofibers hold great potential for wound healing applications since they mimic the native blood clot architecture and offer important binding sites to support fibroblast adhesion and migration. Recently, we introduced a new method of salt-induced self-assembly to prepare nanofibrous fibrinogen scaffolds. Here, we present our results on the mechanical properties of these scaffolds and their interaction with 3T3 fibroblasts and E. coli bacteria, which we used as model systems for wound healing. Hydrated, nanofibrous fibrinogen scaffolds showed a Young's modulus of 1.3 MPa, which is close to the range of native fibrin. 3T3 fibroblasts adhered and proliferated well on nanofibrous and planar fibrinogen up to 72 h with a less pronounced actin cytoskeleton on nanofibers in comparison to planar fibrinogen. Fibroblasts on nanofibers were smaller with many short filopodia while larger cells with few long filopodia were found on planar fibrinogen. Live cell tracking revealed higher migration velocities on nanofibers in comparison to planar fibrinogen. The growth of E. coli bacteria on nanofibrous fibrinogen was significantly reduced as compared to agar controls with no bacteria migrating through the nanofibers. In summary, we conclude that self-assembled fibrinogen nanofibers could become highly attractive as future scaffolds for wound healing applications.

Principles of Fibrinogen Fiber Assembly In Vitro

Fibrinogen nanofibers hold great potential for applications in wound healing and personalized regenerative medicine due to their ability to mimic the native blood clot architecture. Although versatile strategies exist to induce fibrillogenesis of fibrinogen in vitro, little is known about the underlying mechanisms and the associated length scales. Therefore, in this manuscript the current state of research on fibrinogen fibrillogenesis in vitro is reviewed. For the first time, the manifold factors leading to the assembly of fibrinogen molecules into fibers are categorized considering three main groups: substrate interactions, denaturing and non-denaturing buffer conditions. Based on the meta-analysis in the review it is concluded that the assembly of fibrinogen is driven by several mechanisms across different length scales. In these processes, certain buffer conditions, in particular the presence of salts, play a predominant role during fibrinogen self-assembly compared to the surface chemistry of the substrate material. Yet, to tailor fibrous fibrinogen scaffolds with defined structure-function-relationships for future tissue engineering applications, it still needs to be understood which particular role each of these factors plays during fiber assembly. Therefore, the future combination of experimental and simulation studies is proposed to understand the intermolecular interactions of fibrinogen, which induce the assembly of soluble fibrinogen into solid fibers.

Transcript-Activated Coatings on Titanium Mediate Cellular Osteogenesis for Enhanced Osteointegration

Osteointegration is one of the most important factors for implant success. Several biomolecules have been used as part of drug delivery systems to improve implant integration into the surrounding bone tissue. Chemically modified mRNA (cmRNA) is a new form of therapeutic that has been used to induce bone healing. Combined with biomaterials, cmRNA can be used to develop transcript-activated matrices for local protein production with osteoinductive potential. In this study, we aimed to utilize this technology to create bone morphogenetic protein 2 (BMP2) transcript-activated coatings for titanium (Ti) implants. Therefore, different coating methodologies as well as cmRNA incorporation strategies were evaluated. Three different biocompatible biomaterials were used for the coating of Ti, namely, poly-d,l-lactic acid (PDLLA), fibrin, and fibrinogen. cmRNA-coated Ti disks were assayed for transfection efficiency, cmRNA release, cell viability and proliferation, and osteogenic activity in vitro. We found that cmRNA release was significantly delayed in Ti surfaces previously coated with biomaterials. Consequently, the transfection efficiency was greatly improved. PDLLA coating improved the transfection efficiency in a concentration-dependent manner. Lower PDLLA concentration used for the coating of Ti resulted in higher transfection efficiency. Fibrin and fibrinogen coatings showed even higher transfection efficiencies compared to all PDLLA concentrations. In those disks, not only the expression was up to 24-fold higher but also the peak of maximal expression was delayed from 24 h to 5 days, and the duration of expression was also extended until 7 days post-transfection. For fibrin, higher transfection efficiencies were obtained in the coatings with the lowest thrombin amounts. Accordingly, fibrinogen coatings gave the best results in terms of cmRNA transfection. All biomaterial-coated Ti surfaces showed improved cell viability and proliferation, though this was more noticeable in the fibrinogen-coated disks. The latter was also the only coating to support significant amounts of BMP2 produced by C2C12 cells in vitro. Osteogenesis was confirmed using BMP2 cmRNA fibrinogen-coated Ti disks, and it was dependent of the cmRNA amount present. Alkaline phosphatase (ALP) activity of C2C12 increased when using fibrinogen coatings containing 250 ng of cmRNA or more. Similarly, mineralization was also observed that increased with increasing cmRNA concentration. Overall, our results support fibrinogen as an optimal material to deliver cmRNA from titanium-coated surfaces.

Self-assembled fibrinogen–fibronectin hybrid protein nanofibers with medium-sensitive stability

Hybrid protein nanofibers (hPNFs) have been identified as promising nano building blocks for numerous applications in nanomedicine and tissue engineering. We have recently reported a nature-inspired, self-assembly route to create hPNFs from human plasma proteins, i.e., albumin and hemoglobin. However, it is still unclear whether the same route can be applied to other plasma proteins and whether it is possible to control the composition of the resulting fibers. In this context, to further understand the hPNFs self-assembly mechanism and to optimize their properties, we report herein on ethanol-induced self-assembly of two different plasma proteins, i.e., fibrinogen (FG) and fibronectin (FN). We show that by varying initial protein ratios, the composition and thus the properties of the resulting hPNFs can be fine-tuned. Specifically, atomic force microscopy, hydrodynamic diameter, and zeta potential data together revealed a strong correlation of the hPNFs dimensions and surface charge to their initial protein mixing ratio. The composition-independent prompt dissolution of hPNFs in ultrapure water, in contrast to their stability in PBS, indicates that the molecular arrangement of FN and FG in hPNFs is mainly based on electrostatic interactions. Supported by experimental data we introduce a feasible mechanism that explains the interactions between FN and FG and their self-assembly to hPNFs. These findings contribute to the understanding of dual protein interactions, which can be beneficial in designing innovative biomaterials with multifaceted biological and physical characteristics.

Hybrid protein nanofibers (hPNFs) have been identified as promising nano building blocks for numerous applications in nanomedicine and tissue engineering.

Bio-/Nanoimmobilization Platform Based on Bioinspired Fibrin-Bone@Polydopamine-Shell Adhesive Composites for Biosensing

Inspired by blood coagulation and mussel adhesion, we report novel adhesive fibrin-bone@polydopamine (PDA)-shell composite matrix as highly efficient immobilization platform for biomacromolecules and nanomaterials. Fibrin, as a bioglue, and PDA, as a chemical adhesive, are integrated in a one-pot simultaneous polymerization consisting of biopolymerization of fibrinogen and chemical polymerization of dopamine. Fibrin fibers act as adhesive bones to construct scaffold, while PDA coat on the scaffold to form adhesive shell, generating 3D porous composite matrix with unique bone@shell structure. Two types of enzymes (glucose oxidase and acetylcholinesterase) and Au nanoparticles were adopted as respective model biomolecules and nanomaterials to investigate the immobilization capability of the matrix. The bionanocomposites showed high efficiency in capturing nanoparticles and enzymes, as well as significant mass-transfer and biocatalysis efficiencies. Therefore, the bionanocomposites exhibited significant potential in biosensing of glucose and paraoxon with limits of detection down to 5.2 μM and 4 ppt, respectively. The biological-chemical-combined polymerization strategy and composite platform with high immobilization capacity and mass-transfer efficiency open up a novel way for the preparation of high-performance bionanocomposites for various applications, in particular, biosensing.

Targeting Human Thrombus by Liposomes Modified with Anti-Fibrin Protein Binders

Development of tools for direct thrombus imaging represents a key step for diagnosis and treatment of stroke. Nanoliposomal carriers of contrast agents and thrombolytics can be functionalized to target blood thrombi by small protein binders with selectivity for fibrin domains uniquely formed on insoluble fibrin. We employed a highly complex combinatorial library derived from scaffold of 46 amino acid albumin-binding domain (ABD) of streptococcal protein G, and ribosome display, to identify variants recognizing fibrin cloth in human thrombus. We constructed a recombinant target as a stretch of three identical fibrin fragments of 16 amino acid peptide of the Bβ chain fused to TolA protein. Ribosome display selection followed by large-scale Enzyme-Linked ImmunoSorbent Assay (ELISA) screening provided four protein variants preferentially binding to insoluble form of human fibrin. The most specific binder variant D7 was further modified by C-terminal FLAG/His-Tag or double His-tag for the attachment onto the surface of nanoliposomes via metallochelating bond. D7-His-nanoliposomes were tested using in vitro flow model of coronary artery and their binding to fibrin fibers was demonstrated by confocal and electron microscopy. Thus, we present here the concept of fibrin-targeted binders as a platform for functionalization of nanoliposomes in the development of advanced imaging tools and future theranostics.

Controlling the Multiscale Structure of Nanofibrous Fibrinogen Scaffolds for Wound Healing

As a key player in blood coagulation and tissue repair, fibrinogen has gained increasing attention to develop nanofibrous biomaterial scaffolds for wound healing. Current techniques to prepare protein nanofibers, like electrospinning or extrusion, are known to induce lasting changes in the protein conformation. Often, such secondary changes are associated with amyloid transitions, which can evoke unwanted disease mechanisms. Starting from our recently introduced technique to self-assemble fibrinogen scaffolds in physiological salt buffers, we here investigated the morphology and secondary structure of our novel fibrinogen nanofibers. Aiming at optimum self-assembly conditions for wound healing scaffolds, we studied the influence of fibrinogen concentration and pH on the protein conformation. Using circular dichroism and Fourier-transform infrared spectroscopy, we observed partial transitions from α-helical structures to β-strands upon fiber formation. Interestingly, a staining with thioflavin T revealed that this conformational transition was not associated with any amyloid formation. Toward novel scaffolds for wound healing, which are stable in aqueous environment, we also introduced cross-linking of fibrinogen scaffolds in formaldehyde vapor. This treatment allowed us to maintain the nanofibrous morphology while the conformation of fibrinogen nanofibers was redeveloped toward a more native state after rehydration. Altogether, self-assembled fibrinogen scaffolds are excellent candidates for novel wound healing systems since their multiscale structures can be well controlled without inducing any pathogenic amyloid transitions.

Recombinant batroxobin-coated nonwoven chitosan as hemostatic dressing for initial hemorrhage control

The choice of hemostat is determined by the situation and the degree of hemorrhage. One common hemostat, the nonwoven dressing, is easy to handled and controls severe bleeding on wider wounds. In this study, chitosan-based nonwoven dressings with recombinant batroxobin (rBat) were used as efficacious hemostatic dressing agents. Hemostatic agents need to absorb blood quickly in the early stages of blood coagulation cascade to rapidly and effectively control of excessive hemorrhages. To date, most studies of hemostatic agents focused on a single material and hemostats composed of multiple materials have not been studied sufficiently. Thus, we made a chitosan dressing coated with rBat and investigated the microstructure, mechanical properties, hemostatic efficacy, and clotting properties of the coated dressing. Our results showed that the rBat had a synergetic effect on chitosan that improved blood coagulation. Furthermore, the dressing had excellent bleeding control in an Sprague-Dawley (SD) rat femoral artery hemorrhage model. In conclusion, hemostasis can be improved by combining a chitosan-based nonwoven dressing with other agents, and rBat-coated chitosan-based nonwoven dressings have enormous potential to improve blood coagulation.

The influence of surface chemistry on adsorbed fibrinogen conformation, orientation, fiber formation and platelet adhesion

Thrombosis is a clear risk when any foreign material is in contact with the bloodstream. Here we propose an immunohistological stain-based model for non-enzymatic clot formation that enables a facile screen for the thrombogenicity of blood-contacting materials. We exposed polymers with different surface chemistries to protease-free human fibrinogen. We observed that on hydrophilic surfaces, fibrinogen is adsorbed via αC regions, while the γ400-411 platelet-binding dodecapeptide on the D region becomes exposed, and fibrinogen fibers do not form. In contrast, fibrinogen is adsorbed on hydrophobic surfaces via the relatively hydrophobic D and E regions, exposing the αC regions while rendering the γ400-411 inaccessible. Fibrinogen adsorbed on hydrophobic surfaces is thus able to recruit other fibrinogen molecules through αC regions and polymerize into large fibrinogen fibers, similar to those formed in vivo in the presence of thrombin. Moreover, the γ400-411 is available only on the large fibers not elsewhere throughout the hydrophobic surface after fibrinogen fiber formation. When these surfaces were exposed to gel-sieved platelets or platelet rich plasma, a uniform monolayer of platelets, which appeared to be activated, was observed on the hydrophilic surfaces. In contrast, large agglomerates of platelets were clustered on fibers on the hydrophobic surfaces, resembling small nucleating thrombi. Endothelial cells were also able to adhere to the monomeric coating of fibrinogen on hydrophobic surfaces. These observations reveal that the extent and type of fibrinogen adsorption, as well as the propensity of adsorbed fibrinogen to bind platelets, may be modulated by careful selection of surface chemistry.

STATEMENTS OF SIGNIFICANCE

Thrombosis is a well-known side effect of the introduction of foreign materials into the bloodstream, as might exist in medical devices including but not limited to stents, valves, and intravascular catheters. Despite many reported studies, the body's response to foreign materials in contact with the blood remains poorly understood. Current preventive methods consist of drug eluting coatings on the devices or the systemic administration of standard anticoagulants. Here we present a potential mechanism by which surface chemistry can affects fibrinogen conformation and thus affects platelet adhesion and consequently thrombus formation. Our findings suggest a possible coating which enables endothelial cell adhesion while preventing platelet adhesion.

Functional improvement of hemostatic dressing by addition of recombinant batroxobin

Although a number of natural materials have been used as hemostatic agents, many substances do not act quickly enough. Here, we created a novel dressings using collagen and chitosan with recombinant batroxobin (r-Bat) to promote faster and more effective hemostasis. We hypothesized that r-Bat would promote synergetic blood coagulation because it contains a blood coagulation active site different than those of collagen and chitosan. Our results suggest that each substances can maintain hemostatic properties while in the mixed dressings and that our novel hemostatic dressings promotes potent control of bleeding, as demonstrated by a whole blood assay and rat hemorrhage model. In a rat femoral artery model, the scaffold with a high r-Bat concentration more rapidly controlled excessive bleeding. This novel dressings has enormous possible for rapidly controlling bleeding and it improves upon the effect of collagen and chitosan used alone. Our novel r-Bat dressings is a possible candidate for improving preoperative care and displays promising properties as an absorbable agent in hemostasis.

STATEMENT OF SIGNIFICANCE

Despite the excellent hemostatic properties of collagen and chitosan pads, they reported to brittle behavior and lack sufficient hemostatic effect within relevant time. Therefore, we created a novel pad using collagen and chitosan with recombinant batroxobin (r-Bat). r-Bat acts as a thrombin-like enzyme in the coagulation cascade. Specifically, r-Bat, in contrast to thrombin, only splits fibrinopeptide A off and does not influence other hemostatic factors or cells, which makes it clinically useful as a stable hemostatic agent. Also the materials in the pad have synergetic effect because they have different hemostatic mechanisms in the coagulation cascade. This report propose the novel hemostatic pad isreasonable that a great potential for excessive bleeding injury and improve effects of natural substance hemostatic pad.

pH-Dependent Ordered Fibrinogen Adsorption on Polyethylene Single Crystals

Nanostructured surfaces have the potential to influence the assembly as well as the orientation of adsorbed proteins and may, thus, strongly influence the biomaterials' performance. For the class of polymeric (bio)materials a reproducible and well-characterized nanostructure is the ordered chain folded surface of a polyethylene single crystal (PE-SC). We tested the hypothesis that the trinodal-rod-shaped protein human plasma fibrinogen (HPF) adsorbs on the (001) surface of PE-SCs along specific crystallographic directions. The PE-SC samples were prepared by isothermal crystallization in dilute solution and characterized by atomic force microscopy (AFM) before as well as after HPF adsorption at different concentrations and pH values. At a physiological pH of 7.4, connected HPF molecules, or e.g., fibrils, fibril networks, or sponge-like structures, were observed on PE-SC surfaces that featured no preferential orientation. The observation of these nonoriented multiprotein assemblies was explained by predominant protein-protein interactions and limited surface diffusion. However, at an increased pH of 9.2, single HPF molecules, e.g., spherical-shaped and trinodal-rod-shaped HPF molecules as well as agglomerates, were observed on the PE-SC surface. The presence of single HPF molecules at increased pH was explained by decreased protein-protein interactions. These single trinodal-rod-shaped HPF molecules oriented preferentially along crystallographic [100] and [010] directions on the PE-SC surface which was explained by an increased amount of intermolecular bonds along these crystallographic directions with increased surface atom density. The study established that HPF molecules can align on chemically homogeneous surface topographies one order of magnitude smaller than the dimension of the protein. This advances the understanding of how to control the assembly and orientation of proteins on nanostructured polymer surfaces. Controlled protein adsorption is a crucial key to improve the surface functionality of future implants and biosensors.

Surface Assembly Configurations and Packing Preferences of Fibrinogen Mediated by the Periodicity and Alignment Control of Block Copolymer Nanodomains

The ability to control the specific adsorption and packing behaviors of biomedically important proteins by effectively guiding their preferred surface adsorption configuration and packing orientation on polymeric surfaces may have utility in many applications such as biomaterials, medical implants, and tissue engineering. Herein, we investigate the distinct adhesion configurations of fibrinogen (Fg) proteins and the different organization behaviors between single Fg molecules that are mediated by the changes in the periodicity and alignment of chemically alternating nanodomains in thin films of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) block copolymer (BCP). Specifically, the adsorption characteristics of individual Fg molecules were unambiguously resolved on four different PS-b-PMMA templates of dsa PS-b-PMMA, sm PS-b-PMMA, com PS-b-PMMA, and PS-r-PMMA. By direct visualization through high resolution imaging, the distinct adsorption and packing configurations of both isolated and interacting Fg molecules were determined as a function of the BCP template-specific nanodomain periodicity, domain alignment (random versus fully aligned), and protein concentration. The three dominant Fg adsorption configurations, SP∥, SP⊥, and TP, were observed and their occurrence ratios were ascertained on each PS-b-PMMA template. During surface packing, the orientation of the protein backbone was largely governed by the periodicity and alignment of the underlying PS-b-PMMA nanodomains whose specific direction was explicitly resolved relative to the polymeric nanodomain axis. The use of PS-b-PMMA with a periodicity much smaller than (and comparable to) the length of Fg led to a Fg scaffold with the protein backbone aligned parallel (and perpendicular) to the nanodomain major axis. In addition, we have successfully created fully Fg-decorated BCP constructs analogous to two-dimensional Fg crystals in which aligned protein molecules are arranged either side-on or end-on, depending on the BCP template. Our results demonstrate that the geometry and orientation of the protein can be effectively guided during Fg self-assembly by controlling the physical dimensions and orientations of the underlying BCP templates. Finally, the biofunctionality of the BCP surface-bound Fg was assessed and the Fg/BCP construct was successfully used in the Ca-P nanoparticle nucleation/growth and microglia cell activation.

Structural properties of fracture haematoma: current status and future clinical implications

Blood clots (haematomas) that form immediately following a bone fracture have been shown to be vital for the subsequent healing process. During the clotting process, a number of factors can influence the fibrin clot structure, such as fibrin polymerization, growth factor binding, cellular infiltration (including platelet retraction), protein concentrations and cytokines. The modulation of the fibrin clot structure within the fracture site has important clinical implications and could result in the development of multifunctional scaffolds that mimic the natural structure of a haematoma. Artificial haematoma structures such as these can be created from the patient's own blood and can therefore act as an ideal bone defect filling material for potential clinical application to accelerate bone regeneration. Copyright © 2016 John Wiley & Sons, Ltd.

Design of a molecular imprinting biosensor with multi-scale roughness for detection across a broad spectrum of biomolecules

The molecular imprinting technique has tremendous applications in artificial enzymes, bioseparation, and sensor devices.

Interaction of γ-Fe₂O₃ nanoparticles with fibrinogen

In this article, an attempt is made to analysis the binding mechanism of γ-Fe2O3 nanoparticles with fibrinogen by using a combination of circular dichroism, UV-vis, fluorescence spectroscopic and computational methods. The multi-spectroscopic data revealed that the complex easily formed between γ-Fe2O3 nanoparticles and fibrinogen by mainly hydrogen bonding forces. The binding constants of fibrinogen with γ-Fe2O3 nanoparticles were 2.24×10(7), 1.15×10(7) and 0.72×10(7)Lmol(-1) at 298, 304, and 310K, respectively. Furthermore, the results from circular dichroism, UV-vis, synchronous fluorescence, and three-dimensional fluorescence studies showed that the strong binding interaction of γ-Fe2O3 nanoparticles with fibrinogen induced an obvious perturbation in the protein secondary and tertiary structure. Moreover, the results of molecular modeling indicated the existence of the preferable binding site on fibrinogen for γ-Fe2O3 NPs model.

Functional peptide of dermatopontin produces fibrinogen fibrils and modifies its biological activity

BACKGROUND

Dermatopontin (DP), a small extracellular matrix protein, interacts with both fibrinogen and fibrin. DP accelerates fibrin fibril formation and enhances cell adhesion to fibrin fibrils but DP does not influence fibrinogen fibril formation. We have previously demonstrated that DP-4 (PHGQVVVAVRS) is a functional dermatopontin peptide (Wu et al., 2014).

OBJECTIVE

Identification of biological functions of DP-4.

METHODS

Protein-protein interactions were examined by solid-phase assay. The kinetics of fibrinogen/fibrin polymer formation was monitored by turbidity change, SDS-PAGE, and electron microscopy. A cell adhesion assay was performed using human umbilical vein endothelial cells.

RESULTS

Although DP promoted fibrin formation, the DP-4 peptide promoted fibrinogen polymerization but did not apparently affect fibrin formation. The polymerized fibrinogen formed straight solid fibrils comparable to the normally formed fibrin fibrils. A minimum functional sequence of the DP-4 peptide was determined to be VVVAVRS. An αC domain in fibrinogen was involved in the fibril formation. Fibrinogen fibrils made by DP-4 enhanced endothelial cell adhesion and spreading in a dose-dependent manner. This cell adhesion was inhibited by heparin and by anti-αvβ3 and β1 integrin antibodies.

CONCLUSION

DP-4 did not reproduce the full functional biological activities of DP with fibrin but DP-4 did promote fibrinogen fibril formation. The fibrinogen fibrils produced by DP-4 are useful as a novel synthetic biomaterial for therapeutic applications.