Surface chemical and physical modification in stent technology for the treatment of coronary artery disease

Early-Stage Protein Adsorption Sequence on Blood-Contacting Surfaces: Answer to Vroman's Question

Plasma protein adsorption on blood-contacting surfaces is the initiating significant event and modulates the subsequent coagulation response. Despite decades of research in this area, Vroman's questions in 1986 "Who gets there first?" and "When does the next protein arrive?" remain unanswered due to the lack of detection techniques with sufficient temporal resolution. In this work, we develop a droplet microfluidic technology to detect protein adsorption sequences on six typical blood-contacting surfaces in milliseconds. Apolipoproteins (Apo) are found to be the first proteins to adsorb onto the surfaces in a plasma droplet, and the specific type of apolipoprotein depends on the surface. Apo CI is the first protein adsorbed on gold, platinum, graphene, stainless steel, and polyvinyl chloride with the adsorption time varying from 0.01 to 1 s, while Apo CIII preferentially reaches the titanium alloy surface within 1 s. Subsequent to the initial adsorption, Apo AI, AII, and other proteins continue to adsorb until albumin arrives. Thus, the adsorption sequence is revealed, and Vroman's questions are answered. Moreover, this finding demonstrates the influence of the initial protein adsorption on subsequent coagulation at the surface, and it offers new insights into the development of anticoagulant surfaces.

Surface modification strategies for improved hemocompatibility of polymeric materials: a comprehensive review

Polymeric biomaterials are a widely used class of materials due to their versatile properties. However, as with all other types of materials used for biomaterials, polymers also have to interact with blood. When blood comes into contact with any foreign body, it initiates a cascade which leads to platelet activation and blood coagulation. The implant surface also has to encounter a thromboinflammatory response which makes the implant integrity vulnerable, this leads to blood coagulation on the implant and obstructs it from performing its function. Hence, the surface plays a pivotal role in the design and application of biomaterials. In particular, the surface properties of biomaterials are responsible for biocompatibility with biological systems and hemocompatibility. This review provides a report on recent advances in the field of surface modification approaches for improved hemocompatibility. We focus on the surface properties of polysaccharides, proteins, and synthetic polymers. The blood coagulation cascade has been discussed and blood - material surface interactions have also been explained. The interactions of blood proteins and cells with polymeric material surfaces have been discussed. Moreover, the benefits as well as drawbacks of blood coagulation on the implant surface for wound healing purposes have also been studied. Surface modifications implemented by other researchers to enhance as well as prevent blood coagulation have also been analyzed.

Coatings for Cardiovascular Stents-An Up-to-Date Review

Cardiovascular diseases (CVDs) increasingly burden health systems and patients worldwide, necessitating the improved awareness of current treatment possibilities and the development of more efficient therapeutic strategies. When plaque deposits narrow the arteries, the standard of care implies the insertion of a stent at the lesion site. The most promising development in cardiovascular stents has been the release of medications from these stents. However, the use of drug-eluting stents (DESs) is still challenged by in-stent restenosis occurrence. DESs' long-term clinical success depends on several parameters, including the degradability of the polymers, drug release profiles, stent platforms, coating polymers, and the metals and their alloys that are employed as metal frames in the stents. Thus, it is critical to investigate new approaches to optimize the most suitable DESs to solve problems with the inflammatory response, delayed endothelialization, and sub-acute stent thrombosis. As certain advancements have been reported in the literature, this review aims to present the latest updates in the coatings field for cardiovascular stents. Specifically, there are described various organic (e.g., synthetic and natural polymer-based coatings, stents coated directly with drugs, and coatings containing endothelial cells) and inorganic (e.g., metallic and nonmetallic materials) stent coating options, aiming to create an updated framework that would serve as an inception point for future research.

Characteristics of Phospholipid-Immunosuppressant-Antioxidant Mixed Langmuir-Blodgett Films

Hemocompatibility is one of the major criteria for the successful cardiovascular applicability of novel biomaterials. In this context, monolayers of certain biomolecules can be used to improve surface biocompatibility. To this end, biocoatings incorporating a phospholipid (1,2-dioleoyl-sn-glycero-3-phosphocholine, DOPC), an immunosuppressant (cyclosporine A, CsA), and an antioxidant material (lauryl gallate, LG) were fabricated by depositing Langmuir films onto gold or mica substrates using the Langmuir-Blodgett (LB) technique. These LB monolayers were thoroughly characterized by means of quartz crystal microbalance (QCM), atomic force microscopy (AFM), cyclic voltammetry (CV), and contact angle (CA) measurements. The obtained results indicate that the properties of these LB films are modulated by the monolayer composition. The presence of LG in the three-component systems (DOPC-CsA-LG) increases the molecular packing and the surface coverage of the substrate, which affects the wettability of the biocoating. From the different compositions studied here, we conclude that DOPC-CsA-LG monolayers with a DOPC/CsA ratio of 1:1 and LG molar fractions of 0.50 and 0.75 exhibit improved surface biocompatible characteristics. These results open up new perspectives on our knowledge and better understanding of phenomena at the biomaterial/host interface.

Flexible 3D Nanonetworked Silica Film as a Polymer-Free Drug-Eluting Stent Platform to Effectively Suppress Tissue Hyperplasia in Rat Esophagus

Loading and eluting drugs on self-expandable metallic stents (SEMSs) can be challenging in terms of fabrication, mechanical stability, and therapeutic effects. In this study, a flexible 3D nanonetworked silica film (NSF) capable of withstanding mechanical stress during dynamic expansion is constructed to function as a drug delivery platform on an entire SEMS surface. Despite covering a broad curved area, the synthesized NSF is defect-free and thin enough to increase the stent strut diameter (110 µm) by only 0.4 percent (110.45 µm). The hydrophobic modification of the surface enables loading of 4.7 times the sirolimus (SRL) concentration in NSF than Cypher, polymer-coated commercial stent, which is based on the same thickness of coating layer. Furthermore, SRL-loaded NSF exhibits a twofold delay in release compared to the control group without NSF. The SRL-loaded NSF SEMS significantly suppresses stent-induced tissue hyperplasia than the control SEMS in the rat esophagus (all variables, p < 0.05). Thus, the developed NSF is a promising polymer-free drug delivery platform to efficiently treat esophageal stricture.

Nanoparticles-reinforced poly-l-lactic acid composite materials as bioresorbable scaffold candidates for coronary stents: Insights from mechanical and finite element analysis

Current generation of bioresorbable coronary scaffolds (BRS) posed thrombogenicity and deployment issues owing to its thick struts and overall profile. To this end, we hypothesize that the use of nanocomposite materials is able to provide improved material properties and sufficient radial strength for the intended application even at reduced strut thickness. The nanocomposite formulations of tantalum dioxide (Ta₂O₅), L-lactide functionalized (LA)-Ta₂O₅, hydroxyapatite (HA) and LA-HA with poly-l-lactic acid (PLLA) were evaluated in this study. Results showed that tensile modulus and strength were enhanced with non-functionalized nanofillers up until 15 wt% loading, whereas ductility was compromised. On the other hand, functionalized nanofillers/PLLA exhibited improved nanofiller dispersion which resulted higher tensile modulus, strength, and ductility. Selected nanocomposite formulations were evaluated using finite element analysis (FEA) of a stent with varying strut thickness (80, 100 and 150 μm). FEA data has shown that nanocomposite BRS with thinner struts (80-100 μm) made with 15 wt% LA-Ta₂O₅/PLLA and 10 wt% LA-HA/PLLA have increased radial strength, stiffness and reduced recoil compared to PLLA BRS at 150 μm. The reduced strut thickness can potentially mitigate issues such as scaffold thrombosis and promote re-endothelialisation of the vessel.

Finite element analysis of the mechanical performance of a zinc alloy stent with the tenon-and-mortise structure

BACKGROUND

Inadequate scaffolding performance hinders the clinical application of the biodegradable zinc alloy stents.

OBJECTIVE

In this study we propose a novel stent with the tenon-and-mortise structure to improve its scaffolding performance.

METHODS

3D models of stents were established in Pro/E. Based on the biodegradable zinc alloy material and two numerical simulation experiments were performed in ABAQUS. Firstly, the novel stent could be compressed to a small-closed ring by a crimp shell and can form a tenon-and-mortise structure after expanded by a balloon. Finally, 0.35 MPa was applied to the crimp shell to test the scaffolding performance of the novel stent and meanwhile compare it with an ordinary stent.

RESULTS

Results showed that the novel stent decreased the recoiling ratio by 70.7% compared with the ordinary stent, indicating the novel structure improved the scaffolding performance of the biodegradable zinc alloy stent.

CONCLUSION

This study proposes a novel design that is expected to improve the scaffolding performance of biodegradable stents.

Surface engineering at the nanoscale: A way forward to improve coronary stent efficacy

Coronary in-stent restenosis and late stent thrombosis are the two major inadequacies of vascular stents that limit its long-term efficacy. Although restenosis has been successfully inhibited through the use of the current clinical drug-eluting stent which releases antiproliferative drugs, problems of late-stent thrombosis remain a concern due to polymer hypersensitivity and delayed re-endothelialization. Thus, the field of coronary stenting demands devices having enhanced compatibility and effectiveness to endothelial cells. Nanotechnology allows for efficient modulation of surface roughness, chemistry, feature size, and drug/biologics loading, to attain the desired biological response. Hence, surface topographical modification at the nanoscale is a plausible strategy to improve stent performance by utilizing novel design schemes that incorporate nanofeatures via the use of nanostructures, particles, or fibers, with or without the use of drugs/biologics. The main intent of this review is to deliberate on the impact of nanotechnology approaches for stent design and development and the recent advancements in this field on vascular stent performance.

Cardiovascular Stents: A Review of Past, Current, and Emerging Devices

One of the leading causes of morbidity and mortality worldwide is coronary artery disease, a condition characterized by the narrowing of the artery due to plaque deposits. The standard of care for treating this disease is the introduction of a stent at the lesion site. This life-saving tubular device ensures vessel support, keeping the blood-flow path open so that the cardiac muscle receives its vital nutrients and oxygen supply. Several generations of stents have been iteratively developed towards improving patient outcomes and diminishing adverse side effects following the implanting procedure. Moving from bare-metal stents to drug-eluting stents, and recently reaching bioresorbable stents, this research field is under continuous development. To keep up with how stent technology has advanced in the past few decades, this paper reviews the evolution of these devices, focusing on how they can be further optimized towards creating an ideal vascular scaffold.

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.

Additive Manufacturing of Titanium-Based Implants with Metal-Based Antimicrobial Agents

Due to increasing bacterial resistance to antibiotics, surface coatings of medical devices with antimicrobial agents have come to the fore. These surface coatings on medical devices were basically thin coatings that delaminated from the medical devices due to the fluid environment and the biomechanical activities associated with in-service implants. The conventional methods of manufacturing have been used to alloy metal-based antimicrobial (MBA) agents such as Cu with Ti6Al4V to enhance its antibacterial properties but failed to produce intricate shapes. Additive manufacturing technology, such as laser powder bed fusion (LPBF), could be used to produce the Ti6Al4V–xCu alloy with intricate shapes to enhance osseointegration, but have not been successful for texturing the surfaces of the Ti6Al4V–xCu samples at the nanoscale.

Functionalization Strategies and Fabrication of Solvent-Cast PLLA for Bioresorbable Stents

Actual polymer bioresorbable stents (BRS) generate a risk of device thrombosis as a consequence of the incomplete endothelialization after stent implantation. The material-tissue interactions are not fully controlled and stent fabrication techniques do not allow personalized medical solutions. This work investigates the effect of different functionalization strategies onto solvent-cast poly(l-lactic acid) (PLLA) surfaces with the capacity to enhance surface endothelial adhesion and the fabrication of 3D printed BRS. PLLA films were obtained by solvent casting and treated thermally to increase mechanical properties. Surface functionalization was performed by oxygen plasma (OP), sodium hydroxide (SH) etching, or cutinase enzyme (ET) hydrolysis, generating hydroxyl and carboxyl groups. A higher amount of carboxyl and hydroxyl groups was determined on OP and ET compared to the SH surfaces, as determined by contact angle and X-ray photoelectron spectroscopy (XPS). Endothelial cells (ECs) adhesion and spreading was higher on OP and ET functionalized surfaces correlated with the increase of functional groups without affecting the degradation. To verify the feasibility of the approach proposed, 3D printed PLLA BRS stents were produced by the solvent-cast direct writing technique.

Occurrence and predictive factors of restenosis in coronary heart disease patients underwent sirolimus-eluting stent implantation

BACKGROUND

This study aimed to investigate the occurrence and predictive factors of restenosis in coronary heart disease (CHD) patients underwent percutaneous coronary intervention (PCI) with sirolimus-eluting stent (SES).

METHODS

Demographic data, clinical features, and laboratory tests of 398 CHD patients underwent PCI with SES were retrospectively reviewed. Coronary angiography was performed to evaluate coronary stenosis before PCI and in-stent restenosis at 1-year follow-up.

RESULTS

There were 37 (9.3%) patients suffered restenosis, but 361 (90.7%) patients did not develop restenosis at 1-year follow-up. Demographic characteristic (age), cardiovascular risk factors (hypertension and hyperuricemia), biochemical indexes (fasting blood-glucose, total cholesterol, low density lipoprotein cholesterol (LDL-C) and high-sensitivity C-reactive protein (HsCRP)), cardiac function index (cardiac troponin I), lesion features (multivessel artery lesions, target lesion at left circumflex artery (LCX), two target lesions and length of target lesion), and operation procedure (length of stent) were correlated with higher restenosis risk. Moreover, age, hypertension, diabetes mellitus, LDL-C, HsCRP, and target lesion at LCX were independent predictive factors for raised restenosis risk. Based on these independent predictive factors, we established a restenosis risk prediction model, and receiver-operating characteristic curves displayed that this model exhibited an excellent predictive value for higher restenosis risk (areas under the curve 0.953 (95% CI 0.926-0.981)).

CONCLUSION

Our findings provide a new insight into the prediction for restenosis in CHD patients underwent PCI with SES.

Direct Laser Interference Patterning of CoCr Alloy Surfaces to Control Endothelial Cell and Platelet Response for Cardiovascular Applications

The main drawbacks of cardiovascular bare-metal stents (BMS) are in-stent restenosis and stent thrombosis as a result of an incomplete endothelialization after stent implantation. Nano- and microscale modification of implant surfaces is a strategy to recover the functionality of the artery by stimulating and guiding molecular and biological processes at the implant/tissue interface. In this study, cobalt-chromium (CoCr) alloy surfaces are modified via direct laser interference patterning (DLIP) in order to create linear patterning onto CoCr surfaces with different periodicities (≈3, 10, 20, and 32 µm) and depths (≈20 and 800 nm). Changes in surface topography, chemistry, and wettability are thoroughly characterized before and after modification. Human umbilical vein endothelial cells' adhesion and spreading are similar for all patterned and plain CoCr surfaces. Moreover, high-depth series induce cell elongation, alignment, and migration along the patterned lines. Platelet adhesion and aggregation decrease in all patterned surfaces compared to CoCr control, which is associated with changes in wettability and oxide layer characteristics. Cellular studies provide evidence of the potential of DLIP topographies to foster endothelialization without enhancement of platelet adhesion, which will be of high importance when designing new BMS in the future.

Initial contact guidance during cell spreading is contractility-independent

A wide variety of cell types exhibit substrate topography-based behavior, also known as contact guidance. However, the precise cellular mechanisms underlying this process are still unknown. In this study, we investigated contact guidance by studying the reaction of human endothelial cells (ECs) to well-defined microgroove topographies, both during and after initial cell spreading. As the cytoskeleton plays a major role in cellular adaptation to topographical features, two methods were used to perturb cytoskeletal structures. Inhibition of actomyosin contractility with the chemical inhibitor blebbistatatin demonstrated that initial contact guidance events are independent of traction force generation. However, cell alignment to the grooved substrate was altered at later time points, suggesting an initial 'passive' phase of contact guidance, followed by a contractility-dependent 'active' phase that relies on mechanosensitive feedback. The actin cytoskeleton was also perturbed in an indirect manner by culturing cells upside down, resulting in decreased levels of contact guidance and suggesting that a possible loss of contact between the actin cytoskeleton and the substrate could lead to cytoskeleton impairment. The process of contact guidance at the microscale was found to be primarily lamellipodia driven, as no bias in filopodia extension was observed on micron-scale grooves.

Ultra-hydrophilic stent platforms promote early vascular healing and minimise late tissue response: a potential alternative to second-generation drug-eluting stents

AIMS

Simple surface modifications can enhance coronary stent performance. Ultra-hydrophilic surface (UHS) treatment of contemporary bare metal stents (BMS) was assessed in vivo to verify whether such stents can provide long-term efficacy comparable to second-generation drug-eluting stents (DES) while promoting healing comparably to BMS.

METHODS AND RESULTS

UHS-treated BMS, untreated BMS and corresponding DES were tested for three commercial platforms. A thirty-day and a 90-day porcine coronary model were used to characterise late tissue response. Three-day porcine coronary and seven-day rabbit iliac models were used for early healing assessment. In porcine coronary arteries, hydrophilic treatment reduced intimal hyperplasia relative to the BMS and corresponding DES platforms (1.5-fold to threefold reduction in 30-day angiographic and histological stenosis; p<0.04). Endothelialisation was similar on UHS-treated BMS and untreated BMS, both in swine and rabbit models, and lower on DES. Elevation in thrombotic indices was infrequent (never observed with UHS, rare with BMS, most often with DES), but, when present, correlated with reduced endothelialisation (p<0.01).

CONCLUSIONS

Ultra-hydrophilic surface treatment of contemporary stents conferred good healing while moderating neointimal and thrombotic responses. Such surfaces may offer safe alternatives to DES, particularly when rapid healing and short dual antiplatelet therapy (DAPT) are crucial.

First-in-man six-month results of a surface-modified coronary stent system in native coronary stenosis

AIMS

In preclinical studies, a bare metal cobalt-chromium stent with an active surface oxide layer modification (BMSmod) has been shown to inhibit neointimal hyperplasia effectively. We sought to assess both the clinical safety and feasibility of the BMSmod.

METHODS AND RESULTS

In this prospective, non-randomised, first-in-man multicentre study, a total of 31 patients with de novo coronary lesions, reference lumen diameters of 2.5-3.5 mm and lesion length ≤16 mm, were enrolled. Quantitative coronary angiography and optical coherence tomography (OCT) were performed at baseline and six-month follow-up. Primary angiographic and OCT endpoints included in-stent late lumen loss (LLL) and mean neointimal thickness at six months. The device-oriented composite endpoint (DoCE), defined as cardiac death, myocardial infarction not clearly attributable to a non-intervention vessel, and clinically indicated target lesion revascularisation (CI-TLR), was analysed according to the intention-to-treat principle. In 31 patients (33 lesions), the procedural success rate was 93.5%. At six months, angiographic LLL was 0.91±0.45 mm and binary angiographic restenosis occurred in 23.3% of lesions. Out of 33 lesions, OCT was performed in 27 lesions at both time points. Mean neointimal thickness amounted to 348±116 µm. At six months, the DoCE was 19.4% due to the occurrence of CI-TLR in five patients (including one late definite stent thrombosis of a non-study stent).

CONCLUSIONS

In contrast to previous preclinical pathophysiological work, the BMSmod did not prevent neointimal hyperplasia in a first-in-man clinical setting.

Ultrathin Monomolecular Films and Robust Assemblies Based on Cyclic Catechols

We introduce a newly designed catechol-based compound and its application for the preparation of homogeneous monomolecular layers as well as for robust assemblies on various substrates. The precisely defined cyclic catechol material (CyCat) was prepared from ortho-dimethoxybenzene in a phenolic resin-like synthesis and subsequent deprotection, featuring molecules with up to 32 catechol units. The CyCat's chemical structure was carefully assessed via matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF), proton nuclear magnetic resonance (¹H NMR), diffusion ordered spectroscopy (2D DOSY) and high resolution electrospray ionization mass spectrometry (ESI MS) experiments. The formation of colloidal aggregates of the CyCat material in alkaline solution was followed by dynamic light scattering (DLS) and further verified by dropcasting CyCat from solution on highly oriented pyrolytic graphite (HOPG), which was examined by Kelvin probe force microscopy (KPFM). The adsorption behavior of the CyCat to form monomolecular layers was investigated in real time by surface plasmon resonance (SPR). Formation of these thin CyCat layers (1.6-2.1 nm) on Au, SiO₂ and TiO₂ substrates was corroborated by spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS). The prepared coating perfectly reflects the surface structure of the underlying substrate and does not exhibit CyCat colloidal aggregates as verified by atomic force microscopy (AFM). The functional nature of the prepared catechol monolayers was evidenced by reaction with 4-bromophenethylamine and bis(3-aminopropyl)-terminated poly(ethylene oxide) (PEO). Multilayer assemblies were prepared by a simple procedure of iterative immersion in solutions of CyCat and a multifunctional amine on Au, SiO₂ and TiO₂ substrates forming thicker coatings (up to 12 nm). Postmodification with small organic molecules was performed to covalently attach trifluoroacetyl, tetrazole and 2-bromo-2-methylpropanoyl moieties to the amine groups of the multilayer assembly coating. Furthermore, the versatility of the novel multilayer coating was underpinned by "grafting-to" of phenacyl sulfide-terminated PEO and "grafting-from" of poly(methyl methacrylate) via surface-initiated atom transfer radical polymerization (ATRP).

Nano- and microstructured materials for in vitro studies of the physiology of vascular cells

The extracellular environment of vascular cells in vivo is complex in its chemical composition, physical properties, and architecture. Consequently, it has been a great challenge to study vascular cell responses in vitro, either to understand their interaction with their native environment or to investigate their interaction with artificial structures such as implant surfaces. New procedures and techniques from materials science to fabricate bio-scaffolds and surfaces have enabled novel studies of vascular cell responses under well-defined, controllable culture conditions. These advancements are paving the way for a deeper understanding of vascular cell biology and materials-cell interaction. Here, we review previous work focusing on the interaction of vascular smooth muscle cells (SMCs) and endothelial cells (ECs) with materials having micro- and nanostructured surfaces. We summarize fabrication techniques for surface topographies, materials, geometries, biochemical functionalization, and mechanical properties of such materials. Furthermore, various studies on vascular cell behavior and their biological responses to micro- and nanostructured surfaces are reviewed. Emphasis is given to studies of cell morphology and motility, cell proliferation, the cytoskeleton and cell-matrix adhesions, and signal transduction pathways of vascular cells. We finalize with a short outlook on potential interesting future studies.

Characterization of Amorphous Oxide Nano-Thick Layers on 316L Stainless Steel by Electron Channeling Contrast Imaging and Electron Backscatter Diffraction

Characterization of the topmost surface of biomaterials is crucial to understanding their properties and interactions with the local environment. In this study, the oxide layer microstructure of plasma-modified 316L stainless steel (SS316L) samples was analyzed by a combination of electron backscatter diffraction and electron channeling contrast imaging using low-energy incident electrons. Both techniques allowed clear identification of a nano-thick amorphous oxide layer, on top of the polycrystalline substrate, for the plasma-modified samples. A methodology was developed using Monte Carlo simulations combined with the experimental results to estimate thickness of the amorphous layer for different surface conditions. X-ray photoelectron spectroscopy depth profiles were used to validate these estimations.

Nanochips of Tantalum Oxide Nanodots as artificial-microenvironments for monitoring Ovarian cancer progressiveness

Nanotopography modulates cell characteristics and cell behavior. Nanotopological cues can be exploited to investigate the in-vivo modulation of cell characteristics by the cellular microenvironment. However, the studies explaining the modulation of tumor cell characteristics and identifying the transition step in cancer progressiveness are scarce. Here, we engineered nanochips comprising of Tantalum oxide nanodot arrays of 10, 50, 100 and 200 nm as artificial microenvironments to study the modulation of cancer cell behavior. Clinical samples of different types of Ovarian cancer at different stages were obtained, primary cultures were established and then seeded on different nanochips. Immunofluorescence (IF) was performed to compare the morphologies and cell characteristics. Indices corresponding to cell characteristics were defined. A statistical comparison of the cell characteristics in response to the nanochips was performed. The cells displayed differential growth parameters. Morphology, Viability, focal adhesions, microfilament bundles and cell area were modulated by the nanochips which can be used as a measure to study the cancer progressiveness. The ease of fabrication of nanochips ensures mass-production. The ability of the nanochips to act as artificial microenvironments and modulate cell behavior may lead to further prospects in the markerless monitoring of the progressiveness and ultimately, improving the prognosis of Ovarian cancer.

Spatial Control of Cell-Nanosurface Interactions by Tantalum Oxide Nanodots for Improved Implant Geometry

Nanotopological cues can be exploited to understand the nature of interactions between cells and their microenvironment to generate superior implant geometries. Nanosurface parameters which modulate the cell behavior and characteristics such as focal adhesions, cell morphology are not clearly understood. Here, we studied the role of different nanotopographic dimensions in modulating the cell behavior, characteristics and ultimately the cell fate and accordingly, a methodology to improve implant surface geometry is proposed. Tantalum oxide nanodots of 50, 100nm dot diameter with an inter-dot spacing of 20, 70nm and heights 40, 100nm respectively, were engineered on Silicon substrates. MG63 cells were cultured for 72 hours and the modulation in morphology, focal adhesions, cell extensible area, cell viability, transcription factors and genes responsible for bone protein secretion as a function of the nanodot diameter, inter-dot distance and nanodot height were evaluated. Nanodots of 50nm diameter with a 20nm inter-dot spacing and 40nm height enhanced cell spreading area by 40%, promoted cell viability by 70% and upregulated transcription factors and genes twice as much, as compared to the 100nm nanodots with 70nm inter-dot spacing and 100nm height. Favorable interactions between cells and all dimensions of 50nm nanodot diameter were observed, determined with Scanning electron microscopy and Immunofluorescence staining. Nanodot height played a vital role in controlling the cell fate. Dimensions of nanodot features which triggered a transition in cell characteristics or behavior was also defined through statistical analysis. The findings of this study provide insights in the parameters of nanotopographic features which can vitally control the cell fate and should therefore be taken into account when designing implant geometries.

The Systems Biocompatibility of Coronary Stenting

The coronary stent has propelled our understanding of the term "biocompatibility." Stents are expanded at sites of arterial blockage and mechanically reestablish blood flow. This simplicity belies the complex reactions that occur when a stent contacts living substrates. Biocompatible seek to elicit the intended response; stents should perform rather than merely exist. Because performance is assessed in the patient, stent biocompatibility is the multiscale examination of material and cell, and of material, structure, and device in the context of cell, tissue, and organism. This review tracks major biomaterial advances in coronary stent design and discusses biocompatibility clinical performance.

Novel glass-like coatings for cardiovascular implant application: Preparation, characterization and cellular interaction

Glass coatings are of great interest for biomedical implant application due to their excellent properties. Nowadays they are used in different fields including drug delivery, for bone tissue regeneration or as implant. Nevertheless they can only be applied using high temperatures. Therefore their usage in the field of cardiovascular implant application is still restricted. Accordingly new developments in this field have been carried out to overcome this problem and to coat cardiovascular implants. Here, novel glass-like coatings have been developed and applied using sol-gel technique at moderate temperatures. The biocompatibility and selectivity have been analyzed using human endothelial cells. The obtained results clarify that the developed compositions can either promote or suppress endothelial cell growth only by altering the sintering atmosphere. A later application as thin layer on cardiovascular implants like stents is conceivable.

Topological control of nitric oxide secretion by tantalum oxide nanodot arrays

BACKGROUND

Nitric oxide (NO) plays a very important role in the cardiovascular system as a major secondary messenger in signaling pathway. Its concentration regulates most of the important physiological indexes including the systemic blood pressure, blood flow, regional vascular tone and other cardiac functions. The effect of nanotopography on the NO secretion in cardiomyocytes has not been elucidated before. In this study, we report how the nanotopography can modulate the secretion profile of NO and attempt to elucidate the genetic pathways responsible for the same by using Tantalum Oxide nanodot arrays ranging from 10 to 200 nm. A series of nanodot arrays were fabricated with dot diameter ranging from 10 to 200 nm. Temporal NO release of cardiomyocytes was quantified when grown on different surfaces. Quantitative RT-PCR and Western blot were performed to verify the genetic pathways of NO release.

RESULTS

After hours 24 of cell seeding, NO release was slowly enhanced by the increase of dot diameter from 10 nm up to 50 nm, mildly enhanced to a medium level at 100 nm, and increase rapidly to a high level at 200 nm. The temporal enhancement of NO release dropped dramatically on day 3. On day 5, a topology-dependent profile was established that maximized at 50 nm and dropped to control level at 200 nm. The NO releasing profile was closely associated with the expression patterns of genes associated with Endothelial nitric oxide synthase (eNOS) pathway [GPCR, PI3K, Akt, Bad, Bcl-2, NFκB(p65), eNOS], but less associated with Inducible nitric oxide synthase (iNOS) pathway (TNF-α, ILK, Akt, IκBα, NFκB, iNOS). Western blotting of Akt, eNOS, iNOS, and NFκB further validated that eNOS pathway was modulated by nanotopology.

CONCLUSIONS

Based on the findings of the present study, 50, 100 nm can serve as the suitable nanotopography patterns for cardiac implant surface design. These two nanodot arrays promote NO secretion and can also promote the vascular smooth muscle relaxation. The results of this study can improve the heart stent design in the medical treatments.

In vitro and in vivo cell-capture strategies using cardiac stent technology - A review

Stenosis is a symptom of coronary artery disease (CAD), and is caused by narrowing of arteries in the heart. Over the last several decades, medical implants such as cardiac stents have been developed to counter stenosis. Upon implantation of a stent to open up a restricted artery, narrowing of the artery can reoccur (restenosis), due to an immune response launched by the body towards the stent. Currently, restenosis is a major health concern for patients who have undergone heart surgery for coronary artery disease. Recently, there have been new methods developed to combat restenosis, which have shown potential signs of success. One proposed method is the use of stents to capture cells, thereby reducing immune response. This review will explore the different methods for cell capture both in vitro and in vivo. Biological modifications of the stent will be surveyed, as well as the use of surface science to immobilize biological probes. Immobilization of proteins and nucleotides, as well as use of magnetic field are all methods that will be further discussed. Finally, concluding remarks and future prospects will be presented.

Controlled Slow-Release Drug-Eluting Stents for the Prevention of Coronary Restenosis: Recent Progress and Future Prospects

Drug-eluting stents (DES) have become more widely used by cardiologists than bare metal stents (BMS) because of their better ability to control restenosis. However, recognized negative events, particularly including delayed or incomplete endothelialization and late stent thrombosis, have caused concerns over the long-term safety of DES. Although stent-based drug delivery can facilitate a drug's release directly to the restenosis site, a burst of drug release can seriously affect the pharmacological action and is a major factor accounting for adverse effects. Therefore, the drug release rate has become an important criterion in evaluating DES. The factors affecting the drug release rate include the drug carrier, drug, coating methods, drug storage, elution direction, coating thickness, pore size in the coating, release conditions (release medium, pH value, temperature), and hemodynamics after the stent implantation. A better understanding of how these factors influence drug release is particularly important for the reasonable use of efficient control strategies for drug release. This review summarizes the factors influencing the drug release from DES and presents strategies for enhancing the control of the drug's release, including the stent design, the application of absorbable stents, the development of new polymers, and the application of nanocarriers and improvements in the coating technology. Therefore, this paper provides a reference for the preparation of novel controlled slow-release DES.

Accelerating in situ endothelialisation of cardiovascular bypass grafts

The patency of synthetic cardiovascular grafts in the long run is synonymous with their ability to inhibit the processes of intimal hyperplasia, thrombosis and calcification. In the human body, the endothelium of blood vessels exhibits characteristics that inhibit such processes. As such it is not surprising that research in tissue engineering is directed towards replicating the functionality of the natural endothelium in cardiovascular grafts. This can be done either by seeding the endothelium within the lumen of the grafts prior to implantation or by designing the graft such that in situ endothelialisation takes place after implantation. Due to certain difficulties identified with in vitro endothelialisation, in situ endothelialisation, which will be the focus of this article, has garnered interest in the last years. To promote in situ endothelialisation, the following aspects can be taken into account: (1) Endothelial progenital cell mobilization, adhesion and proliferation; (2) Regulating differentiation of progenitor cells to mature endothelium; (3) Preventing thrombogenesis and inflammation during endothelialisation. This article aims to review and compile recent developments to promote the in situ endothelialisation of cardiovascular grafts and subsequently improve their patency, which can also have widespread implications in the field of tissue engineering.

Surface modification of coronary stents with SiCOH plasma nanocoatings for improving endothelialization and anticoagulation

The surface properties of intravascular stent play a crucial role in preventing in-stent restenosis (ISR). In this study, SiCOH plasma nanocoatings were used to modify the surfaces of intravascular stents to improve their endothelialization and anticoagulation properties. SiCOH plasma nanocoatings with thickness of 30-40 nm were deposited by low-temperature plasmas from a gas mixture of trimethysilane (TMS) and oxygen at different TMS:O2 ratios. Water contact angle measurements showed that the SiCOH plasma nanocoating surfaces prepared from TMS:O2  = 1:4 are hydrophilic with contact angle of 29.5 ± 1.9°. The SiCOH plasma nanocoated 316L stainless steel (316L SS) wafers were first characterized by in vitro adhesion tests for blood platelets and human umbilical vein endothelial cells. The in vitro test results showed that the SiCOH plasma nanocoatings prepared from TMS:O2  = 1:4 had excellent hemo- and cytocompatibility. With uncoated 316L SS stents as the control, the SiCOH plasma nanocoated 316L SS stents were implanted into rabbit abdominal artery model for in vivo evaluation of re-endothelialization and ISR inhibition. After implantation for 12 weeks, the animals testing results showed that the SiCOH plasma nanocoatings accelerated re-endothelialization and inhibited ISR with lumen reduction of 26.3 ± 10.1%, which were considerably less than the 41.9 ± 11.6% lumen reduction from the uncoated control group.

Enhancement of endothelialisation of coronary stents by laser surface engineering

BACKGROUND AND OBJECTIVE

Coronary stents have been widely used in the treatment of coronary heart disease. However, complications have hampered the long-term success of the device. Bare-metal stents (BMS) have a high rate of restenosis and poor endothelialisation. The drug-eluting stents (DES), although dramatically reduce restenosis, significantly prevent endothelialisation leading to late thrombosis and behave the same way as BMS after drug releasing. Rapid adhesion and growth of endothelial cells on the stent surface is a key process for early vascular healing after coronary stenting which contributes to the reduction of major complications. Surface properties manipulate cell growth and directly determine the success and life-span of the implants. However, the ideal surface properties of coronary stents are not yet fully understood. The objective of this research is to understand how surface micro/nano textures and associated material chemistry changes generated by a laser beam affect the behavior of endothelial cells on bare metal 316L stents.

MATERIALS AND METHODS

A high power laser beam was applied to modifying the surface properties of 316L coronary stent material and the commercial coronary stents, followed by examination of the adhesion and proliferation of human coronary endothelial cells that were growing on the surfaces. Surface properties were examined by scanning electron microscopy, contact angle measurement, and X-ray photoelectron spectroscopy.

RESULTS

A novel surface with combined micro/nano features was created on stent material 316L and coronary stent with a specific surface chemistry. This surface gives rise to a threefold increase in the adhesion and eightfold increase in the proliferation of endothelial cells. Interestingly, such effects were only observed when the surface texture was produced in the nitrogen atmosphere suggesting the importance of the surface chemistry, including the dramatic increase of chromium nitride, for the interaction of endothelial cells with the material surface. This novel surface is also super-hydrophilic with close to zero water/cell culture fluid contact angles and low cytotoxicity.

CONCLUSIONS

A novel surface created by laser surface-engineering with a combination of defined surface texture and surface chemistry was found beneficial for the improvement of coronary stent endothelialisation. The technology presented here could work with both DES and BMS with added benefit for the improvement of the biocompatibility of current coronary stents.