Negative regulation of fibrin polymerization and clot formation by nanoparticles of silver

Surface-Tailored Nanoplatform for the Diagnosis and Management of Stroke: Current Strategies and Future Outlook

Stroke accounts for one of the top leading reasons for neurological mortality and morbidity around the globe. Both ischemic and hemorrhagic strokes lead to local hypoxia and are brought about by the occlusion or rupturing of the blood vessels. The events taking place after the onset of a stroke include membrane ion pump failure, calcium and glutamate-mediated excitotoxicity, increased ROS production causing DNA damage, mitochondrial dysfunction, oxidative stress, development of brain edema, and microvascular dysfunction. To date, tissue plasminogen activator (tPA) therapy and mechanical removal of blood clots are the only clinically available stroke therapies, approved by Food and Drug Administration (FDA). But because of the narrow therapeutic window of around 4.5 h for tPA therapy and complications like systemic bleeding and anaphylaxis, more clinical trials are ongoing in the same field. Therefore, using nanocarriers with diverse physicochemical properties is a promising strategy in treating and diagnosing stroke as they can efficiently bypass the tight blood-brain barrier (BBB) through mechanisms like receptor-mediated transcytosis and help achieve controlled and targeted drug delivery. In this review, we will mainly focus on the pathophysiology of stroke, BBB alterations following stroke, strategies to target BBB for stroke therapies, different types of nanocarriers currently being used for therapeutic intervention of stroke, and biomarkers as well as imaging techniques used for the detection and diagnosis of stroke.

Influence of nanoparticles on the haemostatic balance: between thrombosis and haemorrhage

Maintenance of a delicate haemostatic balance or a balance between clotting and bleeding is critical to human health. Irrespective of administration route, nanoparticles can reach the bloodstream and might interrupt the haemostatic balance by interfering with one or more components of the coagulation, anticoagulation, and fibrinolytic systems, which potentially lead to thrombosis or haemorrhage. However, inadequate understanding of their effects on the haemostatic balance, along with the fact that most studies mainly focus on the functionality of nanoparticles while forgetting or leaving behind their risk to the body's haemostatic balance, is a major concern. Hence, our review aims to provide a comprehensive depiction of nanoparticle-haemostatic balance interactions, which has not yet been covered. The synergistic roles of cells and plasma factors participating in haemostatic balance are presented. Possible interactions and interference of each type of nanoparticle with the haemostatic balance are comprehensively discussed, particularly focusing on the underlying mechanisms. Interactions of nanoparticles with innate immunity potentially linked to haemostasis are mentioned. Various physicochemical characteristics that influence the nanoparticle-haemostatic balance are detailed. Challenges and future directions are also proposed. This insight would be valuable for the establishment of nanoparticles that can either avoid unintended interference with the haemostatic balance or purposely downregulate/upregulate its key components in a controlled manner.

Anti-Platelet Effect Induced by Iron Oxide Nanoparticles: Correlation with Conformational Change in Fibrinogen

Iron oxide nanoparticles are developed for various biomedical applications, however, there is limited understanding regarding their effects and toxicity on blood components. The particles traveling in circulation inevitably interact with blood cells and plasma proteins and may interfere with hemostasis. Specifically, this study focuses on the influence of superparamagnetic iron oxide nanoparticles (SPIONs) coated with a biocompatible polymer, polyvinyl alcohol (PVA), on platelet function. Here, engineered SPIONs that are functionalized with various PVA coatings to provide these particles with different surface charges and polymer packing are described. These formulations are assessed for any interference with human platelet functions and coagulation, ex vivo. Positively charged SPIONs induce a significant change in platelet GPIIb-IIIa conformation, indicative of platelet activation at the dose of 500 µg mL^-1 . Remarkably, engineered PVA(polyvinyl alcohol)-SPIONs all display a robust dose-dependent anti-platelet effect on platelet aggregation, regardless of the PVA charge and molecular weight. After assessing hypotheses involving SPION-induced steric hindrance in platelet-platelet bridging, as well as protein corona involvement in the antiplatelet effect, the study concludes that the presence of PVA-SPIONs induces fibrinogen conformational change, which correlates with the observed dose-dependent anti-platelet effect.

Effects of functionalized silver nanoparticles on aggregation of human blood platelets

PURPOSE

We studied the effects of silver nanoparticles (AgNPs) on human blood platelet function. We hypothesized that AgNPs, a known antimicrobial agent, can be used as blood-compatible, "ideal material'' in medical devices or as a drug delivery system. Therefore, the aim of the current study was to investigate if functionalized AgNPs affect platelet function and platelets as well as endothelial cell viability in vitro.

METHODS

AgNPs, functionalized with reduced glutathione (GSH), polyethylene glycol (PEG) and lipoic acid (LA) were synthesized. Quartz crystal microbalance with dissipation was used to measure the effect of AgNPs on platelet aggregation. Platelet aggregation was measured by changes in frequency and dissipation, and the presence of platelets on the sensor surface was confirmed and imaged by phase contrast microscopy. Flow cytometry was used to detect surface abundance of platelet receptors. Lactate dehydrogenase test was used to assess the potential cytotoxicity of AgNPs on human blood platelets, endothelial cells, and fibroblasts. Commercially available ELISA tests were used to measure the levels of thromboxane B2 and metalloproteinases (MMP-1, MMP-2) released by platelets as markers of platelet activation.

RESULTS

2 nm AgNPs-GSH, 3.7 nm AgNPs-PEG both at 50 and 100 µg/mL, and 2.5 nm AgNPs-LA at 100 µg/mL reduced platelet aggregation, inhibited collagen-mediated increase in total P-selectin and GPIIb/IIIa, TXB2 formation, MMP-1, and MMP-2 release. The tested AgNPs concentrations were not cytotoxic as they did not affect, platelet, endothelial cell, or fibroblast viability.

CONCLUSION

All tested functionalized AgNPs inhibited platelet aggregation at nontoxic concentrations. Therefore, functionalized AgNPs can be used as an antiplatelet agent or in design and manufacturing of blood-facing medical devices, such as vascular grafts, stents, heart valves, and catheters.

Morphofunctional Properties of Human Platelets Treated with Silver Nanoparticles

We studied structural and functional properties of human platelets in the presence of nanosilver particles. Incubation with 0.05-5 μM silver nanoparticles suppressed platelet adhesion in a dose-dependent manner without affecting internal platelet structure; during adhesion, some granules were not exocytized. Spontaneous platelet activation was observed at nanoparticle concentrations 15-100 μM. Addition of 1-5 μM nanosilver to cells undergoing adhesion blocked massive platelet degranulation, but did not prevent the formation of lamellopodia. The maximum number of preserved granules in platelets was revealed in the presence of 2.5-5 μM silver nanoparticles: 50% after platelet preincubation with silver nanoparticles and 75-77% after stabilization of adherent platelets with silver nanoparticles.

Hemocompatibility of inhaled environmental nanoparticles: Potential use of in vitro testing

Hemocompatibility testing is an important part in the evaluation of nano-based medicines. However, it is not systematically used for the assessment of environmental particles since they do not come in contact with blood immediately. Studies on human exposure to air-borne particles and pulmonary exposure of rodents have reported alterations in blood physiology. It is not clear, whether these effects are majorly caused by tissue inflammation or translocated particles in blood. This review addresses the question, if in vitro hemocompatibility testing could help in the risk evaluation of inhaled particles. Particle blood concentrations were estimated based on exposure levels, ventilation volume, deposition rate, lung surface area, and permeability of the alveolar epithelium to particles. The categories of hemocompatibility, thrombosis, coagulation, platelets, hematology, and immunology, were introduced. Also, concentrations of ultrafine particles, silver nanoparticles, carbon nanotubes that caused adverse effects in human blood samples were compared to the estimated concentrations of translocated particles. The comparison suggested that, it is unlikely for translocated nanoparticles to be the sole cause of adverse blood effects. Nevertheless, the testing of specific hemocompatibility parameters (hemolysis and clotting) in healthy blood might help to compare biological effect of inhaled particles containing different amounts of contamination. Testing of samples from healthy and diseased persons might help to identify pathological dispositions that increase the possibility of adverse reaction of nanoparticles in blood.

The effects of nanomaterials on blood coagulation in hemostasis and thrombosis

The blood coagulation balance in the organism is achieved by the interaction of the blood platelets (PLTs) with the plasma coagulation system (PCS) and the vascular endothelial cells. In healthy organism, these systems prevent thrombosis and, in events of vascular damage, enable blood clotting to stop bleeding. The dysregulation of hemostasis may cause serious thrombotic and/or hemorrhagic pathologies. Numerous engineered nanomaterials are being investigated for biomedical purposes and are unavoidably exposed to the blood. Also, nanomaterials may access vascular system after occupational, environmental, or other types of exposure. Thus, it is essential to evaluate the effects of engineered nanomaterials on hemostasis. This review focuses on investigations of nanomaterial interactions with the blood components involved in blood coagulation: the PCS and PLTs. Particular emphases include the pathophysiology of effects of nanomaterials on the PCS, including the kallikrein-kinin system, and on PLTs. Methods for investigating these interactions are briefly described, and a review of the most important studies on the interactions of nanomaterials with plasma coagulation and platelets is provided. WIREs Nanomed Nanobiotechnol 2017, 9:e1448. doi: 10.1002/wnan.1448 For further resources related to this article, please visit the WIREs website.

Algal production of nano-silver and gold: Their antimicrobial and cytotoxic activities: A review

The spreading of infectious diseases and the increase in incidence of drug resistance among pathogens have made the search for new antimicrobials inevitable, similarly is the cancer disease. Nowadays, there is a growing need for biosynthesized nanoparticles (NPs) as they are one of the most promising and novel therapeutic agents of biological origin. The unique physicochemical properties of the nano silver (Ag-NPs) as well as nano gold (Au-NPs) when combined with the growth inhibitory capacity against microbes lead to an upsurge in the research on NPs and their potential application as antimicrobials. The phytochemicals of marine algae that include hydroxyl, carboxyl, and amino functional groups can serve as effective metal reducing agents and as capping agents to provide a robust coating on the metal NPs. The biosynthesis of Ag-NPs and Au-NPs using green resources is a simple, environmentally friendly, pollutant-free and low-cost approach. The biosynthesized NPs using algae exerted an outstanding antimicrobial and cytotoxic effect.

Receptor-Meditated Endocytosis by Hyaluronic Acid@Superparamagnetic Nanovetor for Targeting of CD44-Overexpressing Tumor Cells

The present report proposes a more rational hyaluronic acid (HA) conjugation protocol that can be used to modify the surface of the superparamagnetic iron oxide nanoparticles (SPIONs) by covalently binding the targeting molecules (HA) with glutamic acid as a molecular linker on peripheral surface of SPIONs. The synthesis of HA-Glutamic Acid (GA)@SPIONs was included oxidization of nanoparticle’s surface with H₂O₂ followed by activation of hydroxyl group and reacting glutamic acid as an intermediate molecule demonstrating transfection of lung cancer cells. Fourier transform infrared (FTIR) and zeta-potential studies confirmed the chemical bonding between amino acid linker and polysaccharides. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay showed that HA-SPIONs-treated cells remained 82.9% ± 2.7% alive at high particle dosage (200 µg/mL iron concentration), whereas GA-SPIONs and bare SPIONs (B-SPIONs) treated cells had only 59.3% ± 13.4% and 26.5% ± 3.1% survival rate at the same conditions, respectively. Confocal microscopy analysis showed increased cellular internalization of HA-SPIONs compared to non-interacting agarose coated SPIONs (AgA-SPIONs).

An Evaluation of Blood Compatibility of Silver Nanoparticles

Silver nanoparticles (AgNPs) have tremendous potentials in medical devices due to their excellent antimicrobial properties. Blood compatibility should be investigated for AgNPs due to the potential blood contact. However, so far, most studies are not systematic and have not provided insights into the mechanisms for blood compatibility of AgNPs. In this study, we have investigated the blood biological effects, including hemolysis, lymphocyte proliferation, platelet aggregation, coagulation and complement activation, of 20 nm AgNPs with two different surface coatings (polyvinyl pyrrolidone and citrate). Our results have revealed AgNPs could elicit hemolysis and severely impact the proliferation and viability of lymphocytes at all investigated concentrations (10, 20, 40 μg/mL). Nevertheless, AgNPs didn't show any effect on platelet aggregation, coagulation process, or complement activation at up to ~40 μg/mL. Proteomic analysis on AgNPs plasma proteins corona has revealed that acidic and small molecular weight blood plasma proteins were preferentially adsorbed onto AgNPs, and these include some important proteins relevant to hemostasis, coagulation, platelet, complement activation and immune responses. The predicted biological effects of AgNPs by proteomic analysis are mostly consistent with our experimental data since there were few C3 components on AgNPs and more negative than positive factors involving platelet aggregation and thrombosis.

Hurdles in selection process of nanodelivery systems for multidrug-resistant cancer

PURPOSE

Most of the nanomedicines for treatment of multidrug-resistant cancer do not reach Phase III trials and many are terminated or withdrawn or are in an indeterminate state since long without any study results being presented. Extensive perusal of nanomedicine development research revealed that one of the critical aspects influencing clinical outcomes and which requires diligent scrutiny is selection process of nanodelivery system.

METHODS

Research papers and articles published on development of nanodelivery systems for treatment of multidrug-resistant cancer were analyzed. Observations and conclusions noted by these researchers which might shed some light on poor clinical performance of nanocarriers were collated and summarized under observation section. Further research articles were studied to find possible solutions which may be applied to these particular problems for resolving them. The inferences of these findings were composed in Result section.

RESULT

Plausible solutions for the observed obstacles were noted as examples of novel formulations that can yield the following: better in vivo imaging, precise targeting and dosing of a specific site and specific cell type in a particular cancer, modulation of tumor surroundings, intonation of systemic effects and high reproducibility.

CONCLUSION

The angle of approach to the development of best nanosystem for a specific type of tumor needs to be spun around. Some of these changes can be brought about by individual scientists, some need to be established by collated efforts of scientists globally and some await advent of better technologies. Regardless of the stratagem, it can be said decisively that the schematics of development phase need rethinking.

Novel osteoinductive photo-cross-linkable chitosan-lactide-fibrinogen hydrogels enhance bone regeneration in critical size segmental bone defects

The purpose of this study was to develop and characterize a novel photo-cross-linkable chitosan-lactide-fibrinogen (CLF) hydrogel and evaluate the efficacy of bone morphogenetic protein-2 (BMP-2) containing a CLF hydrogel for osteogenesis in vitro and in vivo. We synthesized the CLF hydrogels and characterized their chemical structure, degradation rate, compressive modulus and in vitro BMP-2 release kinetics. We evaluated bioactivities of the BMP-2 containing CLF hydrogels (0, 50, 100 and 500ngml(-1)) in vitro using W-20-17 preosteoblast mouse bone marrow stromal cells and C2C12 mouse myoblast cells. The effect of BMP-2 containing CLF gels (0, 0.5, 1, 2 and 5μg) on bone formation was evaluated using rat critical size segmental bone defects for 4weeks. Fourier transform infrared spectroscopy spectra and scanning electron microscopy images showed chemical and structural changes by the addition of fibrinogen into the chitosan-lactide copolymer. The incorporation of fibrinogen molecules significantly increased the compressive modulus of the hydrogels. The in vitro BMP-2 release study showed initial burst releases from the CLF hydrogels followed by sustained releases, regardless of the concentration of the BMP-2 over 4weeks. Cells in all groups were viable in the presence of the hydrogels regardless of BMP-2 doses, indicating non-cytotoxicity of hydrogels. Alkaline phosphate activity and mineralization of cells exhibited dose dependence on BMP-2 containing CLF hydrogels. Radiography, microcomputed tomography and histology confirmed that the BMP-2 containing CLF hydrogels prompted neo-osteogenesis and accelerated healing of the defects in a dose-dependent manner. Thus the CLF hydrogel is a promising delivery system of growth factors for bone regeneration.

Impact of Silver Nanoparticles on Haemolysis, Platelet Function and Coagulation

Silver nanoparticles (Ag NPs) are increasingly used in biomedical applications because of their large antimicrobial spectrum. Data in the literature on the ability of Ag NPs to perform their desired function without eliciting undesirable effects on blood elements are very limited and contradictory. We studied the impact of Ag NPs on erythrocyte integrity, platelet function and blood coagulation. Erythrocyte integrity was assessed by spectrophotometric measurement of haemoglobin release. Platelet adhesion and aggregation was determined by light transmission aggregometry and scanning electron microscopy. The calibrated thrombin generation test was used to study the impact on coagulation cascade. We demonstrated that Ag NPs induced haemolysis. They also increase platelet adhesion without having any impact on platelet aggregation. Finally, they also had procoagulant potential. Bringing all data from these tests together, the no observed effect concentration is 5 μg/mL.

Nanoparticles and the blood coagulation system. Part II: safety concerns

Nanoparticle interactions with the blood coagulation system can be beneficial or adverse depending on the intended use of a nanomaterial. Nanoparticles can be engineered to be procoagulant or to carry coagulation-initiating factors to treat certain disorders. Likewise, they can be designed to be anticoagulant or to carry anticoagulant drugs to intervene in other pathological conditions in which coagulation is a concern. An overview of the coagulation system was given and a discussion of a desirable interface between this system and engineered nanomaterials was assessed in part I, which was published in the May 2013 issue of Nanomedicine. Unwanted pro- and anti-coagulant properties of nanoparticles represent significant concerns in the field of nanomedicine, and often hamper the development and transition into the clinic of many promising engineered nanocarriers. This part will focus on the undesirable effects of engineered nanomaterials on the blood coagulation system. We will discuss the relationship between the physicochemical properties of nanoparticles (e.g., size, charge and hydrophobicity) that determine their negative effects on the blood coagulation system in order to understand how manipulation of these properties can help to overcome unwanted side effects.

Mechanisms of Silver Nanoparticle Release, Transformation and Toxicity: A Critical Review of Current Knowledge and Recommendations for Future Studies and Applications

Nanosilver, due to its small particle size and enormous specific surface area, facilitates more rapid dissolution of ions than the equivalent bulk material; potentially leading to increased toxicity of nanosilver. This, coupled with their capacity to adsorb biomolecules and interact with biological receptors can mean that nanoparticles can reach sub-cellular locations leading to potentially higher localized concentrations of ions once those particles start to dissolve or degrade in situ. Further complicating the story is the capacity for nanoparticles to generate reactive oxygen species, and to interact with, and potentially disturb the functioning of biomolecules such as proteins, enzymes and DNA. The fact that the nanoparticle size, shape, surface coating and a host of other factors contribute to these interactions, and that the particles themselves are evolving or ageing leads to further complications in terms of elucidating mechanisms of interaction and modes of action for silver nanoparticles, in contrast to dissolved silver species. This review aims to provide a critical assessment of the current understanding of silver nanoparticle toxicity, as well as to provide a set of pointers and guidelines for experimental design of future studies to assess the environmental and biological impacts of silver nanoparticles. In particular; in future we require a detailed description of the nanoparticles; their synthesis route and stabilisation mechanisms; their coating; and evolution and ageing under the exposure conditions of the assay. This would allow for comparison of data from different particles; different environmental or biological systems; and structure-activity or structure-property relationships to emerge as the basis for predictive toxicology. On the basis of currently available data; such comparisons or predictions are difficult; as the characterisation and time-resolved data is not available; and a full understanding of silver nanoparticle dissolution and ageing under different conditions is observed. Clear concerns are emerging regarding the overuse of nanosilver and the potential for bacterial resistance to develop. A significant conclusion includes the need for a risk-benefit analysis for all applications and eventually restrictions of the uses where a clear benefit cannot be demonstrated.

The α-helix to β-sheet transition in stretched and compressed hydrated fibrin clots

Fibrin is a protein polymer that forms the viscoelastic scaffold of blood clots and thrombi. Despite the critical importance of fibrin deformability for outcomes of bleeding and thrombosis, the structural origins of the clot's elasticity and plasticity remain largely unknown. However, there is substantial evidence that unfolding of fibrin is an important part of the mechanism. We used Fourier transform infrared spectroscopy to reveal force-induced changes in the secondary structure of hydrated fibrin clots made of human blood plasma in vitro. When extended or compressed, fibrin showed a shift of absorbance intensity mainly in the amide I band (1600-1700 cm(-1)) as well as in the amide II and III bands, indicating an increase of the β-sheets and a corresponding reduction of the α-helices. The structural conversions correlated directly with the strain or pressure and were partially reversible at the conditions applied. The additional absorbance observed at 1612-1624 cm(-1) was characteristic of the nascent interchain β-sheets, consistent with protein aggregation and fiber bundling during clot deformation observed using scanning electron microscopy. We conclude that under extension and/or compression an α-helix to β-sheet conversion of the coiled-coils occurs in the fibrin clot as a part of forced protein unfolding.

Molecular interaction of proteins and peptides with nanoparticles

The interaction of proteins in living cells is one of the key processes in the maintenance of their homeostasis. Introduction of additional agents into the chain of these interactions may influence homeostatic processes. Recent advances in nanotechnologies have led to a wide use of nanoparticles (NPs) in industrial and biomedical applications. NPs are small enough to enter almost all compartments of the body, including cells and organelles, and to complicate the pattern of protein interactions. In some cases, interaction of nanoscale objects with proteins leads to hazardous consequences, such as abnormal conformational changes leading to exposure of cryptic peptide epitopes or the appearance of abnormal functions caused by structural modifications. In addition, the high local protein concentration resulting from protein adsorption on NPs may provoke avidity effects arising from close spatial repetition of the same protein. Finally, the interaction of NPs with proteins is known to induce cooperative effects, such as promotion or inhibition of protein fibrillation or self-assembling of NPs on macromolecules serving as a template. It is obvious that better understanding of the molecular mechanisms of nano-bio interactions is crucial for further advances in all nanotechnological applications. This review summarizes recent progress in understanding the molecular mechanisms of the interactions between proteins or peptides and NPs in order to predict the structural, functional, and/or nanotoxic consequences of these interactions.

Novel microfilaricidal activity of nanosilver

PURPOSE

The currently available drug repertoire against lymphatic filariasis, a major health hazard in the developing world, is inadequate and is fraught with serious limitations. Thus, the development of an effective antifilarial strategy has become a global research thrust mandated by the World Health Organization. Nanoparticles of silver endowed with antibacterial potency are known to induce apoptosis in eukaryotic cells. The present study was designed to investigate the possible microfilaricidal efficacy of silver nanoparticles and to establish the validity of apoptotic rationale in antifilarial drug designing.

METHODS

This report analyzed the effect of nanoparticles of silver as well as gold (size range: 10-15 nm) on the microfilariae of Brugia malayi obtained from the lavage of peritoneal cavities of infected jirds (Meriones unguiculatus). The study included a microfilarial motility assay, a trypan blue exclusion test, a poly(adenosine diphosphate-ribose) polymerase activity study, ethidium bromide/acridine orange differential staining, and transmission, as well as scanning electron microscopic evaluation of ultrastructural changes in microfilariae.

RESULTS

The study demonstrates that nanoparticles of silver, but not of gold, elicited significant loss in microfilarial motility. Differential staining of parasites with ethidium bromide and acridine orange, poly(adenosine diphosphate-ribose) polymerase activity in microfilarial lysate, and electron microscopic findings underscored apoptotic death of parasites attributable to nanosilver. In a trypan blue exclusion test, the 50% lethal dose of nanosilver was measured to be 101.2 μM, which was higher than the recorded complete inhibitory concentration value (50.6 μM), thus supporting nanosilver as a potential drug candidate against lymphatic filariasis.

CONCLUSION

The present report provides the first ever conclusive proof in support of apoptosis as a novel stratagem in antifilarial drug designing and nanoscale silver as a valid lead in research on antifilarial therapeutics. The main embargo about the current drug diethylcarbamazine citrate is its empirical use without rationale. Effective microfilaricidal activity of nanosilver at relatively low concentrations as reported in this study, with evidence of the induction of apoptosis in microfilariae, projects nanosilver as a potential drug adjuvant against lymphatic filariasis. The much higher 50% lethal dose value of nanosilver compared to the complete inhibitory concentration value reported in this study argues in favor of a safe therapeutic window of this agent in its antifilarial efficacy.