Nanomedicine for the reduction of the thrombogenicity of stent coatings

Fabrication of mechanical skeleton of small-diameter vascular grafts via rolling on water surface

Mimicking the multilayered structure of blood vessels and constructing a porous inner surface are two effective approaches to achieve mechanical matching and rapid endothelialization to reduce occlusion in small-diameter vascular grafts. However, the fabrication processes are complex and time consuming, thus complicating the fabrication of personalized vascular grafts. A simple and versatile strategy is proposed to prepare the skeleton of vascular grafts by rolling self-adhesive polymer films. These polymer films are directly fabricated by dropping a polymer solution on a water surface. For the tubes, the length and wall thickness are controlled by the rolling number and position of each film, whereas the structure and properties are tailored by regulating the solution composition. Double-layer vascular grafts (DLVGs) with microporous inner layers and impermeable outer layers are constructed; a microporous layer is formed by introducing a hydrophilic polymer into a polyurethane (PU) solution. DLVGs exhibit a J-shaped stress-strain deformation profile and compliance comparable to that of coronary arteries, sufficient suture retention strength and burst pressure, suitable hemocompatibility, significant adhesion, and proliferation of human umbilical vein endothelial cells. Freshly prepared PU tubes exhibit good cytocompatibility. Thus, this strategy demonstrates potential for rapid construction of small-diameter vascular grafts for individual customization.

Diamond-like Carbon Coatings in the Biomedical Field: Properties, Applications and Future Development

Repairment and replacement of organs and tissues are part of the history of struggle against human diseases, in addition to the research and development (R&D) of drugs. Acquisition and processing of specific substances and physiological signals are very important to understand the effects of pathology and treatment. These depend on the available biomedical materials. The family of diamond-like carbon coatings (DLCs) has been extensively applied in many industrial fields. DLCs have also been demonstrated to be biocompatible, both in vivo and in vitro. In many cases, the performance of biomedical devices can be effectively enhanced by coating them with DLCs, such as vascular stents, prosthetic heart valves and surgical instruments. However, the feasibility of the application of DLC in biomedicine remains under discussion. This review introduces the current state of research and application of DLCs in biomedical devices, their potential application in biosensors and urgent problems to be solved. It will be useful to build a bridge between DLC R&D workers and biomedical workers in order to develop high-performance DLC films/coatings, promote their practical use and develop their potential applications in the biomedical field.

Theranostic Nanomedicines for the Treatment of Cardiovascular and Related Diseases: Current Strategies and Future Perspectives

Cardiovascular and related diseases (CVRDs) are among the most prevalent chronic diseases in the 21st century, with a high mortality rate. This review summarizes the various nanomedicines for diagnostic and therapeutic applications in CVRDs, including nanomedicine for angina pectoris, myocarditis, myocardial infarction, pericardial disorder, thrombosis, atherosclerosis, hyperlipidemia, hypertension, pulmonary arterial hypertension and stroke. Theranostic nanomedicines can prolong systemic circulation, escape from the host defense system, and deliver theranostic agents to the targeted site for imaging and therapy at a cellular and molecular level. Presently, discrete non-invasive and non-surgical theranostic methodologies are such an advancement modality capable of targeted diagnosis and therapy and have better efficacy with fewer side effects than conventional medicine. Additionally, we have presented the recent updates on nanomedicine in clinical trials, targeted nanomedicine and its translational challenges for CVRDs. Theranostic nanomedicine acts as a bridge towards CVRDs amelioration and its management.

Biosensing, Characterization of Biosensors, and Improved Drug Delivery Approaches Using Atomic Force Microscopy: A Review

Since its invention, atomic force microscopy (AFM) has come forth as a powerful member of the “scanning probe microscopy” (SPM) family and an unparallel platform for high-resolution imaging and characterization for inorganic and organic samples, especially biomolecules, biosensors, proteins, DNA, and live cells. AFM characterizes any sample by measuring interaction force between the AFM cantilever tip (the probe) and the sample surface, and it is advantageous over other SPM and electron micron microscopy techniques as it can visualize and characterize samples in liquid, ambient air, and vacuum. Therefore, it permits visualization of three-dimensional surface profiles of biological specimens in the near-physiological environment without sacrificing their native structures and functions and without using laborious sample preparation protocols such as freeze-drying, staining, metal coating, staining, or labeling. Biosensors are devices comprising a biological or biologically extracted material (assimilated in a physicochemical transducer) that are utilized to yield electronic signal proportional to the specific analyte concentration. These devices utilize particular biochemical reactions moderated by isolated tissues, enzymes, organelles, and immune system for detecting chemical compounds via thermal, optical, or electrical signals. Other than performing high-resolution imaging and nanomechanical characterization (e.g., determining Young’s modulus, adhesion, and deformation) of biosensors, AFM cantilever (with a ligand functionalized tip) can be transformed into a biosensor (microcantilever-based biosensors) to probe interactions with a particular receptors of choice on live cells at a single-molecule level (using AFM-based single-molecule force spectroscopy techniques) and determine interaction forces and binding kinetics of ligand receptor interactions. Targeted drug delivery systems or vehicles composed of nanoparticles are crucial in novel therapeutics. These systems leverage the idea of targeted delivery of the drug to the desired locations to reduce side effects. AFM is becoming an extremely useful tool in figuring out the topographical and nanomechanical properties of these nanoparticles and other drug delivery carriers. AFM also helps determine binding probabilities and interaction forces of these drug delivery carriers with the targeted receptors and choose the better agent for drug delivery vehicle by introducing competitive binding. In this review, we summarize contributions made by us and other researchers so far that showcase AFM as biosensors, to characterize other sensors, to improve drug delivery approaches, and to discuss future possibilities.

Anti-Thrombogenicity Study of a Covalently-Attached Monolayer on Stent-Grade Stainless Steel

Implantable devices fabricated from austenitic type 316L stainless steel have been employed significantly in medicine, principally because the material displays excellent mechanical characteristics and corrosion resistance. It is well known, however, that interaction of exposure of such a material to blood can initiate platelet adhesion and blood coagulation, leading to a harmful medical condition. In order to prevent undesirable surface platelet adhesion on biomaterials employed in procedures such as renal dialysis, we developed an ultrathin anti-thrombogenic covalently attached monolayer based on monoethylene glycol silane chemistry. This functions by forming an interstitial hydration layer which displays restricted mobility in the prevention of surface fouling. In the present work, the promising anti-thrombogenic properties of this film are examined with respect to platelet aggregation on 316L austenitic stainless steel exposed to whole human blood. Prior to exposure with blood, all major surface modification steps were examined by X-ray photoelectron spectroscopic analysis and surface free-angle measurement by contact angle goniometry. End-stage anti-thrombogenicity detection after 20 min of blood exposure at 100 s^-1, 300 s^-1, 600 s^-1, 750 s^-1, and 900 s^-1 shear rates revealed that a significant reduction (>90%) of platelet adhesion and aggregation was achieved for surface-modified steel, compared with untreated material. This result is confirmed by experiments conducted in real time for 60-minute exposure to blood at 100 s^-1, 600 s^-1, and 900 s^-1 shear rates.

The melding of nanomedicine in thrombosis imaging and treatment: a review

Thromboembolic diseases constitute a plague in our century, wherein an imbalance of hemostasis leads to thrombus formation and vessels constriction reducing blood flow. Hence, the recent rise of nanomedicine gives birth to advanced diagnostic modalities and therapeutic agents for the early diagnosis and treatment of such diseases. Multimodal nanoagents for the detection of intravascular thrombi and nanovehicles for thrombus-targeted fibrinolytic therapy are few paradigms of nanomedicine approaches to overcome current diagnostic treatment roadblocks and persistent clinical needs. This review highlights the nanomedicine strategies to improve the imaging and therapy of acute thrombi by nanoparticles and nanotheranostics, the detailed imaging of thrombogenic proteins and platelets via atomic force microscopy with the knowledge basis of thrombosis pathophysiology and nanotoxicity.

Lay abstract: The present review highlights the perspectives of nanomedicine in enhancing the diagnostic and therapeutic strategies to deal with thrombosis. The basics in thrombosis are highlighted to provide the reader with better comprehension of the application of nanotools and various multimodal nanocarriers for diagnosis, targeted therapy and monitoring of the disease. The visualization and treatment of acute thrombi using multifunctional nanoparticles and nanotheranostics, along with the structural investigation of the blood-clotting proteins exploiting the atomic force microscopy capabilities are comprehensively described. At the same time, toxicity and biocompatibility issues regarding nanoparticles are discussed.

Nanotechnology in diagnosis and treatment of coronary artery disease

Nanotechnology could provide a new complementary approach to treat coronary artery disease (CAD) which is now one of the biggest killers in the Western world. The course of events, which leads to atherosclerosis and CAD, involves many biological factors and cellular disease processes which may be mitigated by therapeutic methods enhanced by nanotechnology. Nanoparticles can provide a variety of delivery systems for cargoes such as drugs and genes that can address many problems within the arteries. In order to improve the performance of current stents, nanotechnology provides different nanomaterial coatings, in addition to controlled-release nanocarriers, to prevent in-stent restenosis. Nanotechnology can increase the efficiency of drugs, improve local and systematic delivery to atherosclerotic plaques and reduce the inflammatory or angiogenic response after intravascular intervention. Nanocarriers have potential for delivery of imaging and diagnostic agents to precisely targeted destinations. This review paper will cover the current applications and future outlook of nanotechnology, as well as the main diagnostic methods, in the treatment of CAD.

Oxygen-plasma-modified biomimetic nanofibrous scaffolds for enhanced compatibility of cardiovascular implants

Electrospun nanofibrous scaffolds have been extensively used in several biomedical applications for tissue engineering due to their morphological resemblance to the extracellular matrix (ECM). Especially, there is a need for the cardiovascular implants to exhibit a nanostructured surface that mimics the native endothelium in order to promote endothelialization and to reduce the complications of thrombosis and implant failure. Thus, we herein fabricated poly-ε-caprolactone (PCL) electrospun nanofibrous scaffolds, to serve as coatings for cardiovascular implants and guide tissue regeneration. Oxygen plasma treatment was applied in order to modify the surface chemistry of the scaffold and its effect on cell attachment and growth was evaluated. The conditions of the surface modification were properly adjusted in order to define those conditions of the treatment that result in surfaces favorable for cell growth, while maintaining morphological integrity and mechanical behavior. Goniometry (contact angle measurements), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) measurements were used to evaluate the morphological and chemical changes induced by the plasma treatment. Moreover, depth-sensing nanoindentation was performed to study the resistance of the plasma-treated scaffolds to plastic deformation. Lastly, the cell studies indicated that all scaffolds were cytocompatible, with the plasma-treated ones expressing a more pronounced cell viability and adhesion. All the above findings demonstrate the great potential of these biomimetic tissue-engineering constructs as efficient coatings for enhanced compatibility of cardiovascular implants.

Urokinase-coated chitosan nanoparticles for thrombolytic therapy: preparation and pharmacodynamics in vivo

Blood reperfusion of affected limbs is the most effective therapy for peripheral vascular thrombotic disease, restoring nutrition and blood flow to threatened tissues. Because it is more cost-effective than other thrombolytics, urokinase (UK) is widely used to treat venous thrombosis in China. However, its use is limited because of the risk of UK-related hemorrhagic complications. UK-coated nanoparticles (NPs) may decrease adverse effects while simultaneously increasing thrombolytic benefits. The aim of this study was to combine the sustained-release properties of NPs with the clinical benefits of catheter-directed thrombolysis (CDT) to create a promising new therapy. NPs were prepared via self-assembled chitosan and tripolyphosphate, introduced into a thrombosis model in New Zealand white rabbits, and the ratio of the residual thrombus cross-sectional area to the vascular cross-sectional area was calculated. The NPs had a drug-bearing efficiency of 14.5 ± 1.3%, an encapsulation efficiency of 94.8 ± 2.1% while the particle size of UK-coated NPs was 236 nm. Transmission electron microscopy results showed that the shape of the NPs were spherical and regular. Whether delivered by intravenation or catheter, UK-coated NPs produced a significant increase in the thrombolytic effect compared with free UK and confirmed the superiority of CDT for improving clot lysis over drug-induced systemic thrombolysis. The intravenous NPs caused an abnormal increase in fibrinogen. In conclusion, a water-soluble UK-WCS-NP suspension with good encapsulation efficiency was easily prepared UK-WCS-NPs were capable of maintaining UK activity, provided sustained-release of UK and exhibited better thrombolytic function than free UK.

Clinical significance of metallothioneins in cell therapy and nanomedicine

Mammalian metallothioneins (MTs) are low molecular weight (6–7 kDa) cysteine-rich proteins that are specifically induced by metal nanoparticles (NPs). MT induction in cell therapy may provide better protection by serving as antioxidant, anti-inflammatory, antiapoptotic agents, and by augmenting zinc-mediated transcriptional regulation of genes involved in cell proliferation and differentiation. Liposome-encapsulated MT-1 promoter has been used extensively to induce growth hormone or other genes in culture and gene-manipulated animals. MTs are induced as a defensive mechanism in chronic inflammatory conditions including neurodegenerative diseases, cardiovascular diseases, cancer, and infections, hence can serve as early and sensitive biomarkers of environmental safety and effectiveness of newly developed NPs for clinical applications. Microarray analysis has indicated that MTs are significantly induced in drug resistant cancers and during radiation treatment. Nutritional stress and environmental toxins (eg, kainic acid and domoic acid) induce MTs and aggregation of multilamellar electron-dense membrane stacks (Charnoly body) due to mitochondrial degeneration. MTs enhance mitochondrial bioenergetics of reduced nicotinamide adenine dinucleotide–ubiquinone oxidoreductase (complex-1), a rate-limiting enzyme complex involved in the oxidative phosphorylation. Monoamine oxidase-B inhibitors (eg, selegiline) inhibit α-synuclein nitration, implicated in Lewy body formation, and inhibit 1-methyl 4-phenylpyridinium and 3-morpholinosydnonimine-induced apoptosis in cultured human dopaminergic neurons and mesencephalic fetal stem cells. MTs as free radical scavengers inhibit Charnoly body formation and neurodegenerative α-synucleinopathies, hence Charnoly body formation and α-synuclein index may be used as early and sensitive biomarkers to assess NP effectiveness and toxicity to discover better drug delivery and surgical interventions. Furthermore, pharmacological interventions augmenting MTs may facilitate the theranostic potential of NP-labeled cells and other therapeutic agents. These unique characteristics of MTs might be helpful in the synthesis, characterization, and functionalization of emerging NPs for theranostic applications. This report highlights the clinical significance of MTs and their versatility as early, sensitive biomarkers in cell-based therapy and nanomedicine.

Novel nanostructured biomaterials: implications for coronary stent thrombosis

Background

Nanomedicine has the potential to revolutionize medicine and help clinicians to treat cardiovascular disease through the improvement of stents. Advanced nanomaterials and tools for monitoring cell–material interactions will aid in inhibiting stent thrombosis. Although titanium boron nitride (TiBN), titanium diboride, and carbon nanotube (CNT) thin films are emerging materials in the biomaterial field, the effect of their surface properties on platelet adhesion is relatively unexplored.

Objective and methods

In this study, novel nanomaterials made of amorphous carbon, CNTs, titanium diboride, and TiBN were grown by vacuum deposition techniques to assess their role as potential stent coatings. Platelet response towards the nanostructured surfaces of the samples was analyzed in line with their physicochemical properties. As the stent skeleton is formed mainly of stainless steel, this material was used as reference material. Platelet adhesion studies were carried out by atomic force microscopy and scanning electron microscopy observations. A cell viability study was performed to assess the cytocompatibility of all thin film groups for 24 hours with a standard immortalized cell line.

Results

The nanotopographic features of material surface, stoichiometry, and wetting properties were found to be significant factors in dictating platelet behavior and cell viability. The TiBN films with higher nitrogen contents were less thrombogenic compared with the biased carbon films and control. The carbon hybridization in carbon films and hydrophilicity, which were strongly dependent on the deposition process and its parameters, affected the thrombogenicity potential. The hydrophobic CNT materials with high nanoroughness exhibited less hemocompatibility in comparison with the other classes of materials. All the thin film groups exhibited good cytocompatibility, with the surface roughness and surface free energy influencing the viability of cells.

Development of a nanoporous and multilayer drug-delivery platform for medical implants

Biodegradable polymers can be applied to a variety of implants for controlled and local drug delivery. The aim of this study is to develop a biodegradable and nanoporous polymeric platform for a wide spectrum of drug-eluting implants with special focus on stent-coating applications. It was synthesized by poly(DL-lactide-co-glycolide) (PLGA 65:35, PLGA 75:25) and polycaprolactone (PCL) in a multilayer configuration by means of a spin-coating technique. The antiplatelet drug dipyridamole was loaded into the surface nanopores of the platform. Surface characterization was made by atomic force microscopy (AFM) and spectroscopic ellipsometry (SE). Platelet adhesion and drug-release kinetic studies were then carried out. The study revealed that the multilayer films are highly nanoporous, whereas the single layers of PLGA are atomically smooth and spherulites are formed in PCL. Their nanoporosity (pore diameter, depth, density, surface roughness) can be tailored by tuning the growth parameters (eg, spinning speed, polymer concentration), essential for drug-delivery performance. The origin of pore formation may be attributed to the phase separation of polymer blends via the spinodal decomposition mechanism. SE studies revealed the structural characteristics, film thickness, and optical properties even of the single layers in the triple-layer construct, providing substantial information for drug loading and complement AFM findings. Platelet adhesion studies showed that the dipyridamole-loaded coatings inhibit platelet aggregation that is a prerequisite for clotting. Finally, the films exhibited sustained release profiles of dipyridamole over 70 days. These results indicate that the current multilayer phase therapeutic approach constitutes an effective drug-delivery platform for drug-eluting implants and especially for cardiovascular stent applications.

Fructose-enhanced reduction of bacterial growth on nanorough surfaces

Patients on mechanical ventilators for extended periods of time often face the risk of developing ventilator-associated pneumonia. During the ventilation process, patients incapable of breathing are intubated with polyvinyl chloride (PVC) endotracheal tubes (ETTs). PVC ETTs provide surfaces where bacteria can attach and proliferate from the contaminated oropharyngeal space to the sterile bronchoalveolar area. To overcome this problem, ETTs can be coated with antimicrobial agents. However, such coatings may easily delaminate during use. Recently, it has been shown that changes in material topography at the nanometer level can provide antibacterial properties. In addition, some metabolites, such as fructose, have been found to increase the efficiency of antibiotics used to treat Staphylococcus aureus (S. aureus) infections. In this study, we combined the antibacterial effect of nanorough ETT topographies with sugar metabolites to decrease bacterial growth and biofilm formation on ETTs. We present for the first time that the presence of fructose on the nanorough surfaces decreases the number of planktonic S. aureus bacteria in the solution and biofilm formation on the surface after 24 hours. We thus envision that this method has the potential to impact the future of surface engineering of biomaterials leading to more successful clinical outcomes in terms of longer ETT lifetimes, minimized infections, and decreased antibiotic usage; all of which can decrease the presence of antibiotic resistant bacteria in the clinical setting.