Surface reconstruction and hemocompatibility improvement of a phosphorylcholine end-capped poly(butylene succinate) coating

Bio-inspired hemocompatible surface modifications for biomedical applications

When blood first encounters the artificial surface of a medical device, a complex series of biochemical reactions is triggered, potentially resulting in clinical complications such as embolism/occlusion, inflammation, or device failure. Preventing thrombus formation on the surface of blood-contacting devices is crucial for maintaining device functionality and patient safety. As the number of patients reliant on blood-contacting devices continues to grow, minimizing the risk associated with these devices is vital towards lowering healthcare-associated morbidity and mortality. The current standard clinical practice primarily requires the systemic administration of anticoagulants such as heparin, which can result in serious complications such as post-operative bleeding and heparin-induced thrombocytopenia (HIT). Due to these complications, the administration of antithrombotic agents remains one of the leading causes of clinical drug-related deaths. To reduce the side effects spurred by systemic anticoagulation, researchers have been inspired by the hemocompatibility exhibited by natural phenomena, and thus have begun developing medical-grade surfaces which aim to exhibit total hemocompatibility via biomimicry. This review paper aims to address different bio-inspired surface modifications that increase hemocompatibility, discuss the limitations of each method, and explore the future direction for hemocompatible surface research.

Phosphorylcholine- and cation-bearing copolymer coating with superior antibiofilm and antithrombotic properties for blood-contacting devices

The phosphorylcholine- and cation-bering copolymer coating endowed the blood-contacting devices with superior antibiofilm and antithrombotic ability.

Facile preparation of medical segmented poly(ester-urethane) containing uniformly sized hard segments and phosphorylcholine groups for improved hemocompatibility

In order to improve the hemocompatibility of durable medical-grade polyurethane, a novel series of segmented poly(ester-urethane)s containing uniformly sized hard segments and phosphorylcholine (PC) groups on the side chains (SPU-PCs) was prepared by a facile method. The 2-methacryloyloxyethyl phosphorylcholine (MPC) was first reacted with α-thioglycerol by Michael addition to give a diol compound (MPC-diol), then the SPU-PCs with various PC content were prepared by a one-step chain extension of the mixture of MPC-diol and poly(ε-caprolactone) diol (PCL-diol) with aliphatic diurethane diisocyanates (HBH). The chemical structures of MPC-diol and SPU-PCs were confirmed by ¹H NMR and FT-IR, and the influences of PC content on the physicochemical properties of the SPU-PC films were studied. The introduction of PC groups enhanced the degree of micro-phase separation and improved the hydrolytic degradation of the films. Due to the denser hydrogen bonds formed in the uniformly sized hard segments, the films exhibited favorable tensile properties and a slow hydrolytic degradation rate. The results of water contact angle and XPS analysis indicated that the PC groups on the flexible side chains were concentrated on the surface after contact with water. The surface hemocompatibility of the films was evaluated by testing the protein adsorption and platelet adhesion, and the results revealed that the films surfaces could dramatically suppress the protein adsorption and platelet adhesion. The PC-containing polyurethane films possessed outstanding tensile properties, low degradation rate and good surface hemocompatibility, implying their great potential for use as long-term implant or blood-contacting devices.

Synthesis, characterization of phosphorus-containing copolyester and its application as flame retardants for poly(butylene succinate) (PBS)

Two novel phosphorus-containing copolyesters were synthesized by direct polycondensation reaction of phenyl dichlorophosphate, 1,4-succinic acid and 1,4-butanediol using stannous chloride (SnCl₂) and 4-Methylbenzenesulfonic acid as catalyst, and its chemical structures were identified by ¹H and ³¹P nuclear magnetic resonances (¹H and ³¹P NMR). The resulting phosphorus-containing poly(butylene succinate) (PPBS) was characterized by X-ray diffraction (XRD), polarized optical microscope (POM), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). PPBS can be as a flame retardant for commercial poly(butylene succinate) (PBS). A series of flame retardant composite materials were produced by melt-blending of PBS and PPBS. The comprehensive flame retardant property of composite materials was evaluated by limited oxygen index (LOI). While 20 wt % of PPBS was added into PBS resin, good flame retardant properties could be obtained. Composite materials can have much better flame retardancy (LOI = 30) than neat PBS resin. Thermogravimetric analysis (TGA) showed that the weight loss of PBS was decreased by the introduction of PPBS. In addition, possible flame retardancy mechanism of PPBS in composite materials was analyzed by SEM photos of char residue.

Adsorption of Fibrinogen and Fibronectin on Elastomeric Poly(butylene succinate) Copolyesters

Proteins adsorbed onto biomaterial surfaces facilitate cell-material interactions, including adhesion and migration. Of particular importance are provisional matrix components, fibrinogen (Fg) and fibronectin (Fn), which play an important role in the wound-healing process. Here, to assess the potential of a series of elastomeric poly(butylene succinate) (PBS) copolymers for soft tissue engineering and regenerative medicine applications, we examined the adsorption of Fg and Fn. We prepared spin-coated thin films of the poly(butylene succinate) homopolymer and a series of elastomeric poly(butylene succinate) copolymers with butylene succinate (PBS, hard segment) to succinate-dimer linoleic diol unit (dilinoleic succinate (DLS), soft segments) weight ratios of 70:30, 60:40, and 50:50. X-ray diffraction was used to assess crystallinity, whereas the obtained thin films were characterized using a quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy. Protein adsorption was assessed using QCM-D, followed by data analysis using viscoelastic modeling. On all three copolymers, we observed robust adsorption of both key provisional matrix proteins. Importantly, for both proteins, viscoelastic modeling determined that the adlayers were 30-40 nm thick and had low shear modulus values (<25 kPa), thus indicating soft orientations (end-on for Fg) or conformations (open for Fn) of the hydrated proteins. Overall, our results are very encouraging, as they predict excellent cell adhesion and migration, key features enabling tissue integration of potential PBS-DLS scaffolds.

Preparation, Physicochemical Properties, and Hemocompatibility of the Composites Based on Biodegradable Poly(Ether-Ester-Urethane) and Phosphorylcholine-Containing Copolymer

To improve the hemocompatibility of the biodegradable medical poly(ether-ester-urethane) (PEEU), containing uniform-size aliphatic hard segments that was prepared in our lab, a copolymer containing phosphorylcholine (PC) groups was blended with the PEEU. The PC-copolymer of poly(MPC-co-EHMA) (PMEH) was first obtained by copolymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-ethylhexyl methacrylate (EHMA), and then dissolved in mixed solvent of ethanol/chloroform to obtain a homogeneous solution. The composite films (PMPU) with varying PMEH content were prepared by solvent evaporation method. The physicochemical properties of the composite films with varying PMEH content were researched. The PMPU films exhibited higher thermal stability than that of the pure PEEU film. With the PMEH content increasing from 5 to 20 wt%, the PMPU films also possessed satisfied tensile properties with ultimate stress of 22.9-15.8 MPa and strain at break of 925-820%. The surface and bulk hydrophilicity of the films were improved after incorporation of PMEH. In vitro degradation studies indicated that the degradation rate increased with PMEH content, and it took 12-24 days for composite films to become fragments. The protein adsorption and platelet-rich plasma contact tests were adapted to evaluate the surface hemocompatibility of the composite films. It was found that the amount of adsorbed protein and adherent platelet on the surface decreased significantly, and almost no activated platelets were observed when PMEH content was above 5 wt%, which manifested good surface hemocompatibility. Due to the biodegradability, acceptable tensile properties and good surface hemocompatibility, the composites can be expected to be applied in blood-contacting implant materials.

Creation of antifouling microarrays by photopolymerization of zwitterionic compounds for protein assay and cell patterning

Nonspecific binding or adsorption of biomolecules presents as a major obstacle to higher sensitivity, specificity and reproducibility in microarray technology. We report herein a method to fabricate antifouling microarray via photopolymerization of biomimetic betaine compounds. In brief, carboxybetaine methacrylate was polymerized as arrays for protein sensing, while sulfobetaine methacrylate was polymerized as background. With the abundant carboxyl groups on array surfaces and zwitterionic polymers on the entire surfaces, this microarray allows biomolecular immobilization and recognition with low nonspecific interactions due to its antifouling property. Therefore, low concentration of target molecules can be captured and detected by this microarray. It was proved that a concentration of 10ngmL^-1 bovine serum albumin in the sample matrix of bovine serum can be detected by the microarray derivatized with anti-bovine serum albumin. Moreover, with proper hydrophilic-hydrophobic designs, this approach can be applied to fabricate surface-tension droplet arrays, which allows surface-directed cell adhesion and growth. These light controllable approaches constitute a clear improvement in the design of antifouling interfaces, which may lead to greater flexibility in the development of interfacial architectures and wider application in blood contact microdevices.

Artificial placenta: Analysis of recent progress

The artificial placenta (AP) has for many decades captured the imagination of scientists and authors with popular fiction including The Matrix and Aldous Huxley's "Brave New World", depicting a human surviving ex-utero in an artificial uterine environment (AUE). For scientists this has fascinated as a way forward for extremely preterm infants (EPIs) born less than 28 weeks of gestation. Early successes with mechanical ventilation (MV) for infants born above 28 weeks of gestation meant that AP research lost momentum. More recently, the gestational age limit for survival now borders on 23 weeks and corresponds to the biological milestone of lung development marked by the early canalicular stage of lung morphogenesis. The so called greyzone of 23-25 weeks represents a steep increase in mortality with decreasing gestational age and current options in neonatal care are on the fringes of efficacy for this population. A shift in thinking recognizes the vitality of EPIs as a fetus rather than a 37-40 week neonate and this has reinvigorated the concept of the AP. This review will discuss the scale of extreme preterm birth with special reference to previable infants born in the greyzone. Recent AP studies using sheep models are compared, technical obstacles discussed and future research themes identified.

Improved Antifouling Properties of Polydimethylsiloxane Films via Formation of Polysiloxane/Polyzwitterion Interpenetrating Networks

Nonspecific adsorption of proteins is a challenging problem for the development of biocompatible materials, as well as for antifouling and fouling-release coatings, for instance for the marine industry. The concept of preparing amphiphilic systems based on low surface energy hydrophobic materials via their hydrophilic modification is being widely pursued. This work describes a novel two-step route for the preparation of interpenetrating polymer networks of otherwise incompatible poly(dimethylsiloxane) and zwitterionic polymers. Changes in surface hydrophilicity as well as surface charge at different pH values are investigated. Characterization using atomic force microscopy provides thorough insight into surface changes upon hydrophilic modification. Protein fouling of the materials is assessed using fibrinogen as a model protein.

Self-assembled micelles prepared from amphiphilic copolymers bearing cell outer membrane phosphorylcholine zwitterions for a potential anti-phagocytic clearance carrier

A versatile strategy using amphiphilic copolymers to prepare micelles with cell membrane mimetic phosphorylcholine shell and PCL core showing potential anti-phagocytic clearance properties was reported.

Self-assembled porous film with interconnected 3-dimensional structure from 6sPCL-PMPC copolymer

Biodegradable porous films with fibrous frame and good interconnectivity were prepared just by evaporating solvent of 6-arms star-shaped copolymer solution.

Biocompatible and antifouling coating of cell membrane phosphorylcholine and mussel catechol modified multi-arm PEGs

The design and easy fabrication of biocompatible and antifouling coatings on different materials are extremely important for biotechnological and biomedical devices. Here we report a substrate-independent biomimetic modification strategy for fabricating a biocompatible and antifouling ultra-thin coating. Cell membrane antifouling phosphorylcholine (PC) and/or mussel adhesive catechol (c) groups are grafted at the amino-ends of an 8-armed poly(ethylene glycol). The PC groups are introduced by grafting a random copolymer bearing both PC and active ester groups. The modified 8-arm PEGs (PEG-2c-23PC, PEG-6c-23PC and PEG-8c) anchor themselves onto various substrates from aqueous solution and form cell outer membrane mimetic surfaces. Static contact angle, atomic force microscope (AFM) and X-ray photoelectron spectra (XPS) measurements confirm the successful fabrication of coatings on polydopamine (PDA) precoated surfaces. Real-time interaction results between proteins/bacteria and the coatings measured by surface plasmon resonance (SPR) technique suggest excellent anti-protein adsorption and short-term anti-bacteria adhesion performance. The long-term bacteria adhesion, platelet and L929 cell attachment results strongly support the SPR conclusions. Furthermore, the cell membrane mimetic and mussel adhesive protein mimetic PEG-2c-23PC shows hardly any toxicity to L929 fibroblasts, and the coating surface demonstrates the best anti-biofouling performance. This PDA-assisted immobilization of PC and/or catechol modified multi-arm PEGs provides a convenient and universal way to produce a biocompatible and fouling-resistant surface with tailor-made functions, which hopefully can be expanded to a wider range of applications based on both structure and surface superiorities.

Substrate independent coating formation and anti-biofouling performance improvement of mussel inspired polydopamine

Anti-biofouling performance of mussel inspired polydopamine coating can be improved significantly by simple coordination, oxidation, heating or grafting treatment.