Adsorption of Fibrinogen on Silica Surfaces-The Effect of Attached Nanoparticles

Surface Charge-Modulated Toxicity of Cysteine-Stabilized Silver Nanoparticles

The toxicity of silver nanoparticles (AgNPs) depends on their physicochemical properties. The ongoing research aims to develop effective methods for modifying AgNPs using molecules that enable control over the processes induced by nanoparticles in both normal and cancerous cells. Application of amino acid-stabilized nanoparticles appears promising, exhibiting tunable electrokinetic properties. Therefore, this study focused on determining the influence of the surface charge of cysteine (CYS)-stabilized AgNPs on their toxicity towards human normal B (COLO-720L) and T (HUT-78) lymphocyte cell lines. CYS-AgNPs were synthesized via the chemical reduction. Transmission electron microcopy (TEM) imaging revealed that they exhibited a quasi-spherical shape with an average size of 18 ± 3 nm. CYS-AgNPs remained stable under mild acidic (pH 4.0) and alkaline (7.4 and 9.0) conditions, with an isoelectric point observed at pH 5.1. Following a 24 h treatment of lymphocytes with CYS-AgNPs, concentration-dependent alterations in cell morphology were observed. Positively charged CYS-AgNPs notably decreased lymphocyte viability. Furthermore, they exhibited grater genotoxicity and more pronounced disruption of biological membranes compared to negatively charged CYZ-AgNPs. Despite both types of AgNPs interacting similarly with fetal bovine serum (FBS) and showing comparable profiles of silver ion release, the biological assays consistently revealed that the positively charged CYS-AgNPs exerted stronger effects at all investigated cellular levels. Although both types of CYS-AgNPs have the same chemical structure in their stabilizing layers, the pH-induced alterations in their surface charge significantly affect their biological activity.

Effect of free liquid layer quantity on bacteria and protein adhesion to liquid infused polymers

Liquid-infused polymers are recognized for their ability to repel foulants, making them promising for biomedical applications including catheter-associated urinary tract infections (CAUTIs). However, the impact of the quantity of free liquid layer covering the surface on protein and bacterial adhesion is not well understood. Here, we explore how the amount of free silicone liquid layer in infused silicone catheter materials influences the adhesion of bacteria and proteins relevant to CAUTIs. To alter the quantity of the free liquid layer, we either physically removed excess liquid from fully infused catheter materials or partially infused them. We then evaluated the impact on bacterial and host protein adhesion. Physical removal of the free liquid layer from the fully infused samples reduced the height of the liquid layer from 60 μm to below detection limits and silicone liquid loss into the environment by approximately 64% compared to controls, without significantly increasing the deposition of protein fibrinogen or the adhesion of the common uropathogen Enterococcus faecalis. Partially infused samples showed even greater reductions in liquid loss: samples infused to 70%-80% of their maximum capacity exhibited about an 85% decrease in liquid loss compared to fully infused controls. Notably, samples with more than 70% infusion did not show significant increases in fibrinogen or E. faecalis adhesion. These findings suggest that adjusting the levels of the free liquid layer in infused polymers can influence protein and bacterial adhesion on their surfaces. Moreover, removing the free liquid layer can effectively reduce liquid loss from these polymers while maintaining their functionality.

Removal of Free Liquid Layer from Liquid-Infused Catheters Reduces Silicone Loss into the Environment while Maintaining Adhesion Resistance

Silicone urinary catheters infused with silicone liquid offer an effective alternative to antibiotic coatings, reducing microbial adhesion while decreasing bladder colonization and systemic dissemination. However, loss of free silicone liquid from the surface into the host system is undesirable. To reduce the potential for liquid loss, free silicone liquid was removed from the surface of liquid-infused catheters by either removing excess liquid from fully infused samples or by partial infusion. The effect on bacterial and host protein adhesion was then assessed. Removing the free liquid from fully infused samples resulted in a ~64% decrease in liquid loss into the environment compared to controls, with no significant increase in deposition of the host protein fibrinogen or the adhesion of the common uropathogen Enterococcus faecalis. Partially infusing samples decreased liquid loss as total liquid content decreased, with samples infused to 70-80% of their maximum capacity showing a ~85% reduction in liquid loss compared to fully infused controls. Furthermore, samples above 70% infusion showed no significant increase in fibrinogen or E. faecalis adhesion. Together, the results suggest that eliminating free liquid layer, mechanically or through partial infusion, can reduce liquid loss from liquid-infused catheters while preserving functionality.

A multistep in vitro hemocompatibility testing protocol recapitulating the foreign body reaction to nanocarriers

The development of drug nanocarriers based on polymeric, lipid and ceramic biomaterials has been paving the way to precision medicine, where the delivery of poorly soluble active compounds and personalized doses are made possible. However, the nano-size character of these carriers has been demonstrated to have the potential to elicit pathways of the host response different from those of the same biomaterials when engineered as larger size implants and of the drugs when administered without a carrier. Therefore, a specific regulatory framework needs to be made available that can offer robust scientific insights and provide safety data by reliable tests of these novel nano-devices. In this context, the present work presents a multistep protocol for the in vitro assessment of the hemocompatibility of nanocarriers of different physicochemical properties. Poly (ethyl butyl cyanoacrylate) nanoparticles and lipid-based (LipImage™ 815) nanoparticles of comparable hydrodynamic diameter were tested through a battery of assays using human peripheral blood samples and recapitulating the main pathways of the host response upon systemic administration; i.e., protein interactions, fibrinogen-platelet binding, cytotoxicity, and inflammatory response. The data showed the sensitivity and reproducibility of the methods adopted that were also demonstrated to determine individual variability as well as to discriminate between activation of pathways of inflammation and unintended release of inflammatory signaling caused by loss of cell integrity. Therefore, this multistep testing is proposed as a reliable protocol for nanoparticle development and emerging regulatory frameworks.

Rearrangement of protein structures on a gold nanoparticle surface is regulated by ligand adsorption modes

With development of the nanomedicine field and increasing hazards of exposure to nanobiological materials, research on the protein corona is urgently required. In particular, the understanding of the mechanism of structural changes of protein on a nanosurface should be improved. Herein, we focus on exploring the role of ligand adsorption modes (physiosorbed citrates or chemisorbed GSH) in the regulation of conformational rearrangement of three blood proteins (serum albumin, globulin, and fibrinogen) on the surface of gold nanoparticles. Through experimental measurements, protein adsorption features (thermodynamics, kinetics, adsorption orientation, and structural changes) were estimated. Molecular dynamics simulations further indicated that physiosorbed citrates could be gradually peeled off by approaching proteins and that the bare Au surface provided a stronger interface interaction than the chemisorbed GSH layer. Protein structure rearrangements were due to the reduction in protein internal energy, with an increase in H-bond formation involving a decrease in the α-helical content and an increase in the β-sheet content, to offset the high interfacial energy. Rearrangement of protein structures could occur either intramolecularly or intermolecularly. These findings enhanced our understanding of nano-protein interaction in the biological milieu and facilitate biomedical exploration of engineered nanomaterials.

Improving Fibrin Hydrogels' Mechanical Properties, through Addition of Silica or Chitosan-Silica Materials, for Potential Application as Wound Dressings

Fibrin is a protein-based hydrogel formed during blood coagulation. It can also be produced in vitro from human blood plasma, and it is capable of resisting high deformations. However, after each deformation process, it loses high amounts of water, which subsequently makes it mechanically unstable and, finally, difficult to manipulate. The objective of this work was to overcome the in vitro fibrin mechanical instability. The strategy consists of adding silica or chitosan-silica materials and comparing how the different materials electrokinetic-surface properties affect the achieved improvement. The siliceous materials electrostatic and steric stabilization mechanisms, together with plasma protein adsorption on their surfaces, were corroborated by DLS and ζ-potential measurements before fibrin gelling. These properties avoid phase separation, favoring homogeneous incorporation of the solid into the forming fibrin network. Young's modulus of modified fibrin hydrogels was evaluated by AFM to quantitatively measure stiffness. It increased 2.5 times with the addition of 4 mg/mL silica. A similar improvement was achieved with only 0.7 mg/mL chitosan-silica, which highlighted the contribution of hydrophilic chitosan chains to fibrinogen crosslinking. Moreover, these chains avoided the fibroblast growth inhibition onto modified fibrin hydrogels 3D culture observed with silica. In conclusion, 0.7 mg/mL chitosan-silica improved the mechanical stability of fibrin hydrogels with low risks of cytotoxicity. This easy-to-manipulate modified fibrin hydrogel makes it suitable as a wound dressing biomaterial.

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.