Corrigendum: Challenge of material haemocompatibility for microfluidic blood-contacting applications

[This corrects the article DOI: 10.3389/fbioe.2023.1249753.].

Challenge of material haemocompatibility for microfluidic blood-contacting applications

Biological applications of microfluidics technology is beginning to expand beyond the original focus of diagnostics, analytics and organ-on-chip devices. There is a growing interest in the development of microfluidic devices for therapeutic treatments, such as extra-corporeal haemodialysis and oxygenation. However, the great potential in this area comes with great challenges. Haemocompatibility of materials has long been a concern for blood-contacting medical devices, and microfluidic devices are no exception. The small channel size, high surface area to volume ratio and dynamic conditions integral to microchannels contribute to the blood-material interactions. This review will begin by describing features of microfluidic technology with a focus on blood-contacting applications. Material haemocompatibility will be discussed in the context of interactions with blood components, from the initial absorption of plasma proteins to the activation of cells and factors, and the contribution of these interactions to the coagulation cascade and thrombogenesis. Reference will be made to the testing requirements for medical devices in contact with blood, set out by International Standards in ISO 10993-4. Finally, we will review the techniques for improving microfluidic channel haemocompatibility through material surface modifications-including bioactive and biopassive coatings-and future directions.

Diamond-like carbon films prepared by a low temperature periodic process for application in ventricular assist devices

Due to the poor tribological properties of titanium (Ti) and its alloy Ti6Al4V (commonly used for ventricular assist devices manufacturing), diamond-like carbon (DLC) films with excellent anti-wear properties are pursued to improve the wear resistance of Ti and its alloys. Considering the effect of temperature on magnets inside pump impellers and workpiece deformation, DLC films are preferred to be prepared under low temperature. In this study, DLC films were prepared on Ti6Al4V alloys by periodic and continuous processes, and the corresponding maximum deposition temperature was 85 and 154°C, respectively. The periodic DLC films exhibited the feature of columnar structure, and the surface hillocks were less uniform than that of continuous DLC films. The periodic DLC films possessed more sp³ -bonded structures, and the accessorial sp³ -bonding mainly existed in the form of CH. Compared to continuous DLC films, the periodic DLC films had lower residual stress and better adhesion with Ti6Al4V substrates. Both DLC films could effectively reduce the friction coefficient and wear rate of Ti6Al4V alloys both in air and fetal bovine serum (FBS), and the periodic DLC films exhibited superior anti-wear properties to that of continuous DLC films in FBS. Haemocompatibility evaluation revealed that both DLC films presented similar levels of more human platelet adhesion and activation as compared with that of bare Ti6Al4V. However, both DLC films significantly prolonged plasma clotting time in comparison to bare Ti6Al4V. This study demonstrates the potential of low-temperature DLC films as wear-resistant surface modification for VADs.

Bovine erythrocytes are poor surrogates for human when exposed to sublethal shear stress

Animal blood products are routinely used as surrogates for human tissue in haemocompatibility testing of rotary blood pumps. Bovine blood is particularly attractive due to the animal's large blood volume; however, bovine red blood cells (RBC) differ substantially from those of human, both in biophysical properties and molecular composition. We aimed to determine whether differences also exist in the sensitivity of bovine RBC to a standardised shear stress protocol. Fresh blood from healthy human and bovine donors was exposed to discrete combinations of shear stress using a Couette shearing system, prior to assessment of cellular deformability and mechanical sensitivity. Each sample was exposed to 25 sublethal shear stress combinations (ranging 60-100 Pa × 5-300 s). While bovine RBC exhibited decreased maximal elongation in the absence of conditioning shear, overall deformability at lower shears was ~1.8-fold greater than human. When exposed to any conditioning shear stresses >80 Pa (or 60-70 Pa beyond 5 s), human RBC were significantly rigidified, with greater magnitudes and prolonged exposure compounding this effect. Significantly larger shears were required to rigidify bovine RBC; the most extreme shear condition (100 Pa × 300 s) resulted in approximately three-times more rigidification of human RBC than bovine (137% and 47% respectively). Bovine RBC have superior resilience to mechanical stress when compared with human. Using bovine blood in ex vivo evaluation of rotary blood pumps may thus misrepresent and overestimate device-blood success, and may also have flow-on effects for eventual users. Fresh human blood during early-phase ex vivo testing is thus recommended, given shear-inducing blood pumps are designed for humans - not cattle.

Preparation of modified polysulfone material decorated by sulfonated citric chitosan for haemodialysis and its haemocompatibility

Polysulfone (PSF) works potentially in haemodialysis due to its great mechanical and chemical stability, but performs poorly in haemocompatibility. For promoting the unpleasant haemocompatibility, sulfonated citric chitosan (SCACS) with the structure and groups similar to heparin was primarily synthesized by acylation and sulfonation. Furthermore, the chloroacylated PSF was pretreated by electrophilic chloroacetyl chloride to achieve more active sites for further reaction; the following membranes underwent the amination and were named amination polysulfone (AMPSF) membranes. Moreover, SCACS with abundant carboxyl and sulfonic groups was covalently grafted at the surface of pretreated PSF membranes, called PSF-SCACS membranes. The PSF-SCACS membranes were successfully synthesized and characterized by 1H NMR, ATR-FTIR and XPS. In addition, the water contact angle of PSF-SCACS membranes decreased by 47° and the morphologies of the membranes changed little compared with the unmodified PSF membranes. The haemocompatible testing results, including protein adsorption, platelet adhesion, haemolysis rate, plasma recalcification time, activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT), demonstrated that the PSF-SCACS membranes possessed excellent haemocompatible performances, and SCACS played an important role in the modification.

Impact of Polyethylene Glycol Functionalization of Graphene Oxide on Anticoagulation and Haemolytic Properties of Human Blood

Graphene oxide (GO) is one of the most explored nanomaterials in recent years. It has numerous biomedical applications as a nanomaterial including drug and gene delivery, contrast imaging, cancer treatment, etc. Since most of these applications need intravenous administration of graphene oxide and derivatives, the evaluation of their haemocompatibility is an essential preliminary step for any of the developed GO applications. Plentiful data show that functionalization of graphene oxide nanoparticles with polyethylene glycol (PEG) increases biocompatibility, thus allowing PEGylated GO to elicit less dramatic blood cell responses than their pristine counterparts. Therefore, in this work, we PEGylated graphene oxide nanoparticles and evaluated the effects of their PEGylation on the structure and function of human blood components, especially on the morphology and the haemolytic potential of red blood cells (RBCs). Further, we studied the effect of PEGylation on some blood coagulation factors, including plasma fibrinogen as well as on the activated partial thromboplastin (aPTT), prothrombin time (PT) and platelet aggregation. Our findings provide important information on the mechanisms through which PEGylation increases GO compatibility with human blood cells. These data are crucial for the molecular design and biomedical applications of PEGylated graphene oxide nanomaterials in the future.

Systematic Modification and Evaluation of Enzyme-Loaded Chitosan Nanoparticles

Polymeric-based nano drug delivery systems have been widely exploited to overcome protein instability during formulation. Presently, a diverse range of polymeric agents can be used, among which polysaccharides, such as chitosan (CS), hyaluronic acid (HA) and cyclodextrins (CDs), are included. Due to its unique biological and physicochemical properties, CS is one of the most used polysaccharides for development of protein delivery systems. However, CS has been described as potentially immunogenic. By envisaging a biosafe cytocompatible and haemocompatible profile, this paper reports the systematic development of a delivery system based on CS and derived with HA and CDs to nanoencapsulate the model human phenylalanine hydroxylase (hPAH) through ionotropic gelation with tripolyphosphate (TPP), while maintaining protein stability and enzyme activity. By merging the combined set of biopolymers, we were able to effectively entrap hPAH within CS nanoparticles with improvements in hPAH stability and the maintenance of functional activity, while simultaneously achieving strict control of the formulation process. Detailed characterization of the developed nanoparticulate systems showed that the lead formulations were internalized by hepatocytes (HepG2 cell line), did not reveal cell toxicity and presented a safe haemocompatible profile.

Ligand-Sensitised LaF3 :Eu3+ and SrF2 :Eu3+ Nanoparticles and in Vitro Haemocompatiblity Studies

Luminescent Ln³⁺ -doped nanoparticles (NPs) functionalised with the desired organic ligand molecules for haemocompatibility studies were obtained in a one-pot synthesis. Chelated aromatic organic ligands such as isophthalic acid, terephthalic acid, ibuprofen, aspirin, 1,2,4,5-benzenetetracarboxylic acid, 2,6-pyridine dicarboxylic acid and adenosine were applied for surface functionalisation. The modification of the nanoparticles is based on the donor-acceptor character of the ligand-nanoparticle system, which is an alternative to covalent functionalisation by peptide bonding as presented in our recent report. The aromatic groups of selected ligands absorb UV light and transfer their excited-state energy to the dopant Eu³⁺ ions in LaF₃ and SrF₂ NPs. Herein, we discuss the structural and spectroscopic characterisation of the NPs and the results of haemocompatibility studies. Flow cytometry analysis of the nanoparticles' membrane-binding is also presented.

Biocompatibility of Biomaterials for Nanoencapsulation: Current Approaches

Nanoencapsulation is an approach to circumvent shortcomings such as reduced bioavailability, undesirable side effects, frequent dosing and unpleasant organoleptic properties of conventional drug delivery systems. The process of nanoencapsulation involves the use of biomaterials such as surfactants and/or polymers, often in combination with charge inducers and/or ligands for targeting. The biomaterials selected for nanoencapsulation processes must be as biocompatible as possible. The type(s) of biomaterials used for different nanoencapsulation approaches are highlighted and their use and applicability with regard to haemo- and, histocompatibility, cytotoxicity, genotoxicity and carcinogenesis are discussed.

Wood-Based Cellulose Nanofibrils: Haemocompatibility and Impact on the Development and Behaviour of Drosophila melanogaster

Wood-based cellulose nanofibrils (CNF) offer an excellent scaffold for drug-delivery formulation development. However, toxicity and haemocompatibility of the drug carrier is always an important issue. In this study, toxicity-related issues of CNF were addressed. Different doses of CNF were orally administered to Drosophila and different tests like the developmental cycle, trypan blue exclusion assay, larva crawling assay, thermal sensitivity assay, cold sensitivity assay, larval light preference test, climbing behaviour, nitroblue tetrazolium (NBT) reduction assay, adult phenotype, and adult weight were conducted to observe the impact on its development and behaviour. A haemocompatibility assay was done on the blood taken from healthy Wistar rats. In Drosophila, the abnormalities in larval development and behaviour were observed in the behavioural assays. However, the cytotoxic effect could not be confirmed by the gut staining and level of reactive oxygen species. The larvae developed into an adult without any abnormality in the phenotype. The CNF did cause loss of weight in the adult flies and did not cause much toxicity within the body since there was no phenotypic defect. Hemolysis data also suggested that CNF was safe at lower doses, as the data was well within acceptable limits. All these results suggest that cellulose nanofibres have no significant cytotoxic effects on Drosophila. However, the developmental and behavioural abnormalities suggest that CNF may act as a behavioural teratogen.

Kinetic study of NTPDase immobilization and its effect of haemocompatibility on polyethylene terephthalate

Poor haemocompatibility of material surfaces is a serious limitation that can lead to failure of blood-contacting devices and implants. In this work, we have improved the haemocompatibility of polyethylene terephthalate (PET) surfaces by immobilizing apyrase/ecto-nucleoside triphosphate diphosphohydrolase (NTPDase) on to the carboxylated PET. NTPDase immobilized PET surfaces scavenge the ADP released by activated platelets, which prevents further platelet activation and aggregation. The surface properties of the modified PET were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDAX), and contact angle measurement. The enzyme attachment and stability on the modified PET surfaces were evaluated. The kinetics of free enzyme and immobilized enzyme were studied and fitted using the Michaelis-Menten kinetic model. Both free and immobilized NTPDase followed Michaelis-Menten kinetics with similar Michaelis-Menten constants (K_m). This suggests that the activity of NTPDase was unchanged upon immobilization. Protein adsorption and %hemolysis was significantly reduced for carboxylated PET and NTPDase immobilized PET surfaces compared to unmodified PET. Lactate dehydrogenase assay showed that the number of adhered platelets reduced by more than an order of magnitude for the NTPDase immobilized PET surface compared to unmodified PET. These results clearly indicate that NTPDase immobilization significantly enhances the haemocompatibility of PET surfaces.

Highly stable gold nanoparticles green-synthesized by upcycling cartilage waste extract from yellow-nose skate (Dipturus chilensis) and evaluation of its cytotoxicity, haemocompatibility and antioxidant activity

Skate (Dipturus chilensis) cartilage extract was utilized as a green reducing agent for the synthesis of spherical gold nanoparticles with an average size of 16.7 ± 0.2 nm. The gold nanoparticle solution showed a surface plasmon resonance at 543 nm with a wine-red colour. A strong X-ray diffraction pattern and clear lattice structure in high-resolution transmission electron microscopy indicated a face-centred cubic structure of the gold nanoparticles. The gold nanoparticles retained excellent colloidal stability. Gold nanoparticles showed strong antioxidant activity in terms of 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity. In vitro cytotoxicity was observed for seven cancer cells assessed by the water-soluble tetrazolium assay. Among the seven cancer cells, the highest cytotoxicity was observed for MDA-MB-231 (human breast adenocarcinoma cell) followed by HeLa (human epithelial cervix adenocarcinoma cell) and lastly by HT-29 (human colorectal adenocarcinoma cell). Furthermore, gold nanoparticles showed excellent haemocompatibility, indicating the possibility of their use as a future nanomedicine. These results strongly suggest that gold nanoparticles green-synthesized by upcycling skate cartilage waste extract will be valuable carriers or vehicles for the delivery of drugs or bioactive molecules, such as anti-cancer agents, for the treatment of cancers.

Surface Nanostructuring of Parylene-C Coatings for Blood Contacting Implants

This paper investigates the effects on the blood compatibility of surface nanostructuring of Parylene-C coating. The proposed technique, based on the consecutive use of O₂ and SF₆ plasma, alters the surface roughness and enhances the intrinsic hydrophobicity of Parylene-C. The degree of hydrophobicity of the prepared surface can be precisely controlled by opportunely adjusting the plasma exposure times. Static contact angle measurements, performed on treated Parylene-C, showed a maximum contact angle of 158°. The nanostructured Parylene-C retained its hydrophobicity up to 45 days, when stored in a dry environment. Storing the samples in a body-mimicking solution caused the contact angle to progressively decrease. However, at the end of the measurement, the plasma treated surfaces still exhibited a higher hydrophobicity than the untreated counterparts. The proposed treatment improved the performance of the polymer as a water diffusion barrier in a body simulating environment. Modifying the nanotopography of the polymer influences the adsorption of different blood plasma proteins. The adsorption of albumin—a platelet adhesion inhibitor—and of fibrinogen—a platelet adhesion promoter—was studied by fluorescence microscopy. The adsorption capacity increased monotonically with increasing hydrophobicity for both studied proteins. The effect on albumin adsorption was considerably higher than on fibrinogen. Study of the proteins simultaneous adsorption showed that the albumin to fibrinogen adsorbed ratio increases with substrate hydrophobicity, suggesting lower thrombogenicity of the nanostructured surfaces. Animal experiments proved that the treated surfaces did not trigger any blood clot or thrombus formation when directly exposed to the arterial blood flow. The findings above, together with the exceptional mechanical and insulation properties of Parylene-C, support its use for packaging implants chronically exposed to the blood flow.

Comparative study of different polymeric coatings for the next-generation magnesium-based biodegradable stents

Development of next-generation bioabsorbable stents based on magnesium alloys is gaining lots of attention. However, finding an appropriate coating in order to enhance its corrosion resistance along with preserving other requirements is still a challenge. In this study, three FDA-approved polymers, namely poly(lactic acid), polycaprolactone and poly(lactic-co-glycolic acid), have been investigated as potential coatings for magnesium-based stents to enhance their corrosion resistance, biocompatibility and haemocompatibility. Potentiodynamic and electrochemical impedance spectroscopy results demonstrated that PLA and PLGA coating performed better in improving corrosion resistance in comparison with uncoated and other coated samples. Although all coated and bare samples displayed desirable results of haemocompatibility assays, PLA-coated samples showed better outcome in terms of biocompatibility. The results revealed that PLA can be considered as a potential coating material to enhance the main characteristics of magnesium-based bioabsorbable stents.

Prediction of the level and duration of shear stress exposure that induces subhemolytic damage to erythrocytes

BACKGROUND

Current generation mechanical circulatory assist devices are designed to minimize high shears to blood for prolonged durations to avoid hemolysis. However, red blood cells (RBC) demonstrate impaired capacity to deform when exposed to shear stress (SS) well below the "hemolytic threshold".

OBJECTIVE

We endeavored to identify how changes in the magnitude and duration of SS exposure alter RBC deformability and subsequently develop a model to predict erythrocyte subhemolytic damage.

METHODS

RBC suspensions were exposed to discrete magnitudes of SS (1-64 Pa) for specific durations (1-64 s), immediately prior to RBC deformability being measured. Analyses included exploring the maximal RBC deformation (EImax) and SS required for half EImax (SS1/2). A surface-mesh was interpolated onto the raw data to predict impaired RBC deformability.

RESULTS

When SS was applied at <16Pa, limited changes were observed. When RBC were exposed to 32 Pa, mild impairments in EImax and SS1/2 occurred, although 64 Pa caused a dramatic impairment of RBC deformability. A clear relation between SS duration and magnitude was determined, which could predict impaired RBC deformability.

CONCLUSION

The present results provide a model that may be used to predict whether RBC deformability is decreased following exposure to a given level and duration of SS, and may guide design of future generations of mechanical circulatory assist devices.

Haemocompatibility of Modified Nanodiamonds

This study reports the interactions of modified nanodiamond particles in vitro with human blood. Modifications performed on the nanodiamond particles include oxygenation with a chemical method and hydrogenation upon chemical vapor deposition (CVD) plasma treatment. Such nanodiamonds were later incubated in whole human blood for different time intervals, ranging from 5 min to 5 h. The morphology of red blood cells was assessed along with spectral measurements and determination of haemolysis. The results showed that no more than 3% of cells were affected by the nanodiamonds. Specific modifications of the nanodiamonds give us the possibility to obtain nanoparticles which are biocompatible with human blood. They can form a basis for the development of nanoscale biomarkers and parts of sensing systems and devices useful in biomedical environments.

Polyelectrolyte coating on superparamagnetic iron oxide nanoparticles as interface between magnetic core and biorelevant media

Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy, thus they have only kinetic stability. Spontaneous changes can be delayed by designed surface coating. In biomedical applications, superparamagnetic iron oxide nanoparticles (SPIONs) require an optimized coating in order to fulfil the expectation of medicine regulatory agencies and ultimately that of biocompatibility. In this work, we show the high surface reactivity of naked SPIONs due to ≡Fe-OH sites, which can react with H⁺/OH^- to form pH- and ionic strength-dependent charges. We explain the post-coating of naked SPIONs with organic polyacids via multi-site complex bonds formed spontaneously. The excess polyacids can be removed from the medium. The free COOH groups in coating are prone to react with active biomolecules like proteins. Charging and pH- and salt-dependent behaviour of carboxylated SPIONs were characterized quantitatively. The interrelation between the coating quality and colloidal stability measured under biorelevant conditions is discussed. Our coagulation kinetics results allow us to predict colloidal stability both on storage and in use; however, a simpler method would be required to test SPION preparations. Haemocompatibility tests (smears) support our qualification for good and bad SPION manufacturing; the latter 'promises' fatal outcome in vivo.

Synthesis of cubic ZnS microspheres exhibiting broad visible emission for bioimaging applications

Biocompatible ZnS microspheres with an average diameter of 3.85 µm were grown by solvo-hydrothermal (S-H) method using water-acetonitrile-ethylenediamine (EDA) solution combination. ZnS microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform (FT)-Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques. The broad photoluminescence (PL) emissions from 380-580 nm that were seen from the ZnS microspheres attributed to the increase in carrier concentration, as understood from the observed intense Raman band at 257 cm(-1). Cytotoxicity and haemocompatibility investigations of these ZnS microspheres revealed its biocompatibility. ZnS microspheres, along with biological cell lines, were giving visible light emission and could be used for bioimaging applications.

Blood compatibility of human amniotic membrane compared with heparin-coated ePTFE for vascular tissue engineering

Amniotic membrane (AM), a placenta-derived natural biomaterial, has several characteristics which make it a potential substitute for blood vessels. However, there are no reports on the effects of the AM on blood components. The aim of this study was to evaluate the blood compatibility of the epithelial and mesenchymal surfaces of the amnion for potential use in vascular tissue engineering. The activation of intrinsic and extrinsic pathways of the clotting system, haemolysis and platelet adhesion were studied and the results were compared with heparin-coated expanded polytetrafluoroethylene (ePTFE) as a standard synthetic vascular graft. Prothrombin time (PT), activated partial thromboplastin time (aPTT), clotting time (CT) and haemolysis (%) tests showed that both the epithelial and mesenchymal sides of the AM are haemocompatible. Platelet aggregation and P-selectin production from the platelets showed that the epithelial surface of the AM has less induction of platelet activation than ePTFE. The results of scanning electron microscopy (SEM) demonstrated that platelets in contact with ePTFE had a higher rate of adhesion than with the epithelial and mesenchymal surfaces of the AM. Moreover, the morphological distribution of the platelets showed that the majority of platelets were round, while a large number of cells on ePTFE were dendritic. These results suggest that the AM which contains epithelial and mesenchymal stem cells has appropriate haemocompatibility to be employed in vascular tissue engineering, especially as a vein substitute. Copyright © 2015 John Wiley & Sons, Ltd.

In vitro Endothelialization and Platelet Adhesion on Titaniferous Upgraded Polyether and Polycarbonate Polyurethanes

Polycarbonateurethanes (PCU) and polyetherurethanes (PEU) are used for medical devices, however their bio- and haemocompatibility is limited. In this study, the effect of titaniferous upgrading of different polyurethanes on the bio- and haemocompatibility was investigated by endothelial cell (EC) adhesion/proliferation and platelet adhesion (scanning electron microscopy), respectively. There was no EC adhesion/proliferation and only minor platelet adhesion on upgraded and pure PCU (Desmopan). PEUs (Texin 985, Tecothane 1085, Elastollan 1180A) differed in their cyto- and haemocompatibility. While EC adhesion depended on the type of PEU, any proliferative activity was inhibited. Additional titaniferous upgrading of PEU induced EC proliferation and increased metabolic activity. However, adherent ECs were significantly activated. While Texin was highly thrombotic, only small amounts of platelets adhered onto Tecothane and Elastollan. Additional titaniferous upgrading reduced thrombogenicity of Texin, preserved haemocompatibility of Elastollan, and increased platelet activation/aggregation on Tecothane. In conclusion, none of the PUs was cytocompatible; only titaniferous upgrading allowed EC proliferation and metabolism on PEUs. Haemocompatibility depended on the type of PU.

Surface modification of biomaterials using plasma immersion ion implantation and deposition

Although remarkable progress has been made on biomaterial research, the ideal biomaterial that satisfies all the technical requirements and biological functions is not available up to now. Surface modification seems to be a more economic and efficient way to adjust existing conventional biomaterials to meet the current and ever-evolving clinical needs. From an industrial perspective, plasma immersion ion implantation and deposition (PIII&D) is an attractive method for biomaterials owing to its capability of treating objects with irregular shapes, as well as the control of coating composition. It is well acknowledged that the physico-chemical characteristics of biomaterials are the decisive factors greatly affecting the biological responses of biomaterials including bioactivity, haemocompatibility and antibacterial activity. Here, we mainly review the recent advances in surface modification of biomaterials via PIII&D technology, especially titanium alloys and polymers used for orthopaedic, dental and cardiovascular implants. Moreover, the variations of biological performances depending on the physico-chemical properties of modified biomaterials will be discussed.