Nanoscaled Morphology and Mechanical Properties of a Biomimetic Polymer Surface on a Silicone Hydrogel Contact Lens.

Materials taking advantage of the characteristics of biological tissues are strongly sought after in medical science and bioscience. On the natural corneal tissue surface, the highly soft and lubricated surface is maintained by composite structures composed of hydrophilic biomolecules and substrates. To mimic this structure, the surface of a silicone hydrogel contact lens was modified with a biomimetic phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), and the nanoscaled morphology and mechanical properties of the surface were confirmed with advanced surface characterization and imaging techniques under an aqueous medium. Concavities and convexities on the nanometer order were recognized on the surface. The surface was completely covered with a PMPC layer and remained intact even after 30 days of clinical use in a human ocular environment. The mechanical properties of the natural corneal tissue and the PMPC-modified surface were similar in the living environment, that is, low modulus and frictional properties comparable to natural tissues. These results show the validity of material preparation by biomimetic methods. The methodologies developed in this study may contribute to future development of human-friendly medical devices.

Photoinduced Surface Zwitterionization for Antifouling of Porous Polymer Substrates.

Surface functionalization of polymeric porous substrates is one of the most important requirements to enhance their applications in the biomedical field. In this study, we achieved photoinduced surface modification using a highly efficient reaction of hydrophilic polymers bearing phosphorylcholine groups. Polymers composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) units and 2-( N-ethylanilino)ethyl methacrylate units were synthesized with attention to the polymer architectures. The surface modification of the porous polyethylene (PE) substrates was carried out by the coating of the MPC polymers with a photochemical radical generator, followed by photoirradiation for a few minutes. Surface analysis by attenuated total reflectance Fourier transform IR spectroscopy and X-ray photoelectron spectroscopy indicated that the MPC polymer layer was generated on the PE surface. Cross-sectional confocal microscopy images showed that the MPC polymers were coated on the polymer surface, even inside the porous structure of the PE substrate. After modification, the porous PE substrates showed a significant increase in hydrophilicity and the water-penetration rate through the pores. Furthermore, the amount of protein adsorbed on the PE substrate was reduced significantly by the surface modification. These functionalities were dependent on the MPC polymer architectures. Thus, we concluded that the photoreactive polymer system developed furnished the porous substrates with antifouling properties.

Label-Free Separation of Induced Pluripotent Stem Cells with Anti-SSEA-1 Antibody Immobilized Microfluidic Channel.

When induced pluripotent stem cells (iPSCs) are routinely cultured, the obtained cells are a heterogeneous mixture, including feeder cells and partially differentiated cells. Therefore, a purification process is required to use them in a clinical stage. We described a label-free separation of iPSCs using a microfluidic channel. Antibodies against stage-specific embryonic antigen 1 (SSEA-1) was covalently immobilized on the channel coated with a phospholipid polymer. After injection of the heterogeneous cell suspension containing iPSCs, the velocity of cell movement under a liquid flow condition was measured. The mean velocity of the cell movement was 2.1 mm/sec in the unmodified channel, while that in the channel with the immobilized-antibody was 0.4 mm/sec. The eluted cells were fractionated by eluting time. As a result, the SSEA-1 positive iPSCs were mainly contained in later fractions, and the proportion of iPSCs was increased from 43% to 82% as a comparison with the initial cell suspension. These results indicated that iPSCs were selectively separated by the microfluidic channel. This channel is a promising device for label-free separation of iPSCs based on their pluripotent state.

Synthesis of grafted phosphorylcholine polymer layers as specific recognition ligands for C-reactive protein focused on grafting density and thickness to achieve highly sensitive detection.

We studied the effects of layer thickness and grafting density of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) thin layers as specific ligands for the highly sensitive binding of C-reactive protein (CRP). PMPC layer thickness was controlled by surface-initiated activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP). PMPC grafting density was controlled by utilizing mixed self-assembled monolayers with different incorporation ratios of the bis[2-(2-bromoisobutyryloxy)undecyl] disulfide ATRP initiator, as modulated by altering the feed molar ratio with (11-mercaptoundecyl)tetra(ethylene glycol). X-ray photoelectron spectroscopy and ellipsometry measurements were used to characterize the modified surfaces. PMPC grafting densities were estimated from polymer thickness and the molecular weight obtained from sacrificial initiator during surface-initiated AGET ATRP. The effects of thickness and grafting density of the obtained PMPC layers on CRP binding performance were investigated using surface plasmon resonance employing a 10 mM Tris-HCl running buffer containing 140 mM NaCl and 2 mM CaCl2 (pH 7.4). Furthermore, the non-specific binding properties of the obtained layers were investigated using human serum albumin (HSA) as a reference protein. The PMPC layer which has 4.6 nm of thickness and 1.27 chains per nm(2) of grafting density showed highly sensitive CRP detection (limit of detection: 4.4 ng mL(-1)) with low non-specific HSA adsorption, which was improved 10 times than our previous report of 50 ng mL(-1).

Animal Experiments of the Helical Flow Total Artificial Heart.

Severe cardiac failure patients require a total artificial heart (TAH) to save life. To realize a TAH that can fit a body of small stature and has high performance, high durability, good anatomical fitting, good blood compatibility, and physiological control, we have been developing the helical flow TAH (HFTAH) with two helical flow pumps with hydrodynamic levitation impeller. Animal experiments of the HFTAH were conducted to perform in vivo studies. The HFTAH was implanted in 13 adult female goats weighing 45.0-64.0 kg. After surgery, neither anti-coagulant nor anti-platelet medication was given systemically. The HFTAH was usually driven with a quasi-pulsatile mode. The 1/R control or ΔP control was applied to control the circulation. The ΔP control is a new method using simplified equation of the 1/R control. The HFTAH could be implanted in all goats with good anatomical fitting. Two goats survived for a long time (100 and 68 days). Major causes of termination were device failure and surgical complications. In the device failure, trouble with hydrodynamic bearing was conspicuous. In the two long-term survived goats, experiments were terminated with bearing instability that was probably caused by the suction effect. In these goats, hemolysis occurred on postoperative day 88 and 44, which was considered to be relevant to the bearing trouble. Thrombus was found at the broken right bearing of the 100-day survived goat. However, antithrombogenicity of the pump is expected to be good unless bearing trouble occurs. In two long-term survived goats, the 1/R control or ΔP control worked appropriately to prevent the elevation of right atrial pressure. In both goats, hemodynamic parameters changed with the condition of the animals, liver and kidney functions remained almost normal except when recovering from surgery and during hemolysis, and total protein recovered 2 weeks after surgery. Although instability of the hydrodynamic bearing should be improved, performance of the HFTAH with physiological control could be demonstrated.

Photo-induced universal modification of small-diameter decellularized blood vessels with a hemocompatible peptide improves in vivo patency.

Decellularized vessels (DVs) have the potential to serve as available grafts for small-diameter vascular (<6 mm) reconstruction. However, the absence of functional endothelia makes them likely to trigger platelet aggregation and thrombosis. Luminal surface modification is an efficient approach to prevent thrombosis and promote endothelialization. Previously, we identified a hemocompatible peptide, HGGVRLY, that showed endothelial affinity and antiplatelet ability. By conjugating HGGVRLY with a phenylazide group, we generated a photoreactive peptide that can be modified onto multiple materials, including non-denatured extracellular matrices. To preserve the natural collagen of DVs as much as possible, we used a lower ultrahydrostatic pressure than that previously reported to prepare decellularized grafts. The photoreactive HGGVRLY peptide could be modified onto DV grafts via UV exposure for only 2 min. Modified DVs showed improved endothelial affinity and antiplatelet ability in vitro. When rat abdominal aortas were replaced with DVs, modified DVs with more natural collagen demonstrated the highest patent rate after 10 weeks. Moreover, the photoreactive peptide remained on the lumen surface of DVs over two months after implantation. Therefore, the photoreactive peptide could be efficiently and sustainably modified onto DVs with more natural collagens, resulting in improved hemocompatibility. STATEMENT OF SIGNIFICANCE: We employed a relatively lower ultrahydrostatic pressure to prepare decellularized vessels (DVs) with less denatured collagens to provide a more favorable environment for cell migration and proliferation. The hemocompatibility of DV luminal surface can be enhanced by peptide modification, but undenatured collagens are difficult to modify. We innovatively introduce a phenylazide group into the hemocompatible peptide HGGVRLY, which we previously identified to possess endothelial affinity and antiplatelet ability, to generate a photoreactive peptide. The photoreactive peptide can be efficiently and stably modified onto DVs with more natural collagens. DV grafts modified with photoreactive peptide exhibit enhanced in vivo patency. Furthermore, the sustainability of photoreactive peptide modification on DV grafts within bloodstream is evident after two months of transplantation.

Widely distributable and retainable in-situ gelling material for treating myocardial infarction.

Intramyocardial hydrogel injection is a promising therapy to prevent negative remodeling following myocardial infarction (MI). In this study, we report a mechanism for in-situ gel formation without external stimulation, resulting in an injectable and tissue-retainable hydrogel for MI treatment, and investigate its therapeutic outcomes. A liquid-like polymeric solution comprising poly(3-acrylamidophenylboronic acid-co-acrylamide) (BAAm), polyvinyl alcohol (PVA), and sorbitol (S) increases the viscous modulus by reducing the pre-added sorbitol concentration is developed. This solution achieves a sol-gel transition in-vitro in heart tissue by spontaneously diffusing the sorbitol. After intramyocardial injection, the BAAm/PVA/S with lower initial viscous modulus widely spreads in the myocardium and gelate compared to a viscoelastic alginate (ALG) hydrogel and is retained longer than the BAAm/S solution. Serial echocardiogram analyses prove that injecting the BAAm/PVA/S into the hearts of subacute MI rats significantly increases the fraction shortening and ejection shortening and attenuates the expansion of systolic LV diameter for up to 21 d after injection compared to the saline injection as a control, but the ALG injection does not. In addition, histological evaluation shows that only the BAAm/PVA/S decreases the infarct size and increases the wall thickness 21 d after injection. The BAAm/PVA/S intramyocardial injection is better at restraining systolic ventricular dilatation and cardiac failure in the rat MI model than in the control groups. Our findings highlight an effective injectable hydrogel therapy for MI by optimizing injectability-dependent distribution and retention of injected material. STATEMENT OF SIGNIFICANCE: In-situ gelling material is a promising strategy for intramyocardial hydrogel injection therapy for myocardial infarction (MI). Since the sol-gel transition of reported materials is driven by external stimulation such as temperature, pH, or ultraviolet, their application in vivo remains challenging. In this study, we first reported a synthetic in-situ gelling material (BAAm/PVA/S) whose gelation is stimulated by spontaneously reducing pre-added sorbitol after contacting the heart tissue. The BAAm/PVA/S solution spreads evenly, and is retained for at least 21 d in the heart tissue. Our study demonstrated that intramyocardial injection of the BAAm/PVA/S with more extensive distribution and longer retention had better effects on preventing LV dilation and improving cardiac function after MI than that of viscoelastic ALG and saline solution. We expect that these findings provide fundamental information for the optimum design of injectable biomaterials for treating MI.

Biomimetic-Engineered Silicone Hydrogel Contact Lens Materials.

Contact lenses are one of the most successful applications of biomaterials. The chemical structure of the polymers used in contact lenses plays an important role in determining the function of contact lenses. Different types of contact lenses have been developed based on the chemical structure of polymers. When designing contact lenses, materials scientists consider factors such as mechanical properties, processing properties, optical properties, histocompatibility, and antifouling properties, to ensure long-term wear with minimal discomfort. Advances in contact lens materials have addressed traditional issues such as oxygen permeability and biocompatibility, improving overall comfort, and duration of use. For example, silicone hydrogel contact lenses with high oxygen permeability were developed to extend the duration of use. In addition, controlling the surface properties of contact lenses in direct contact with the cornea tissue through surface polymer modification mimics the surface morphology of corneal tissue while maintaining the essential properties of the contact lens, a significant improvement for long-term use and reuse of contact lenses. This review presents the material science elements required for advanced contact lenses of the future and summarizes the chemical methods for achieving these goals.

The helical flow pump with a hydrodynamic levitation impeller.

The helical flow pump (HFP) is a novel rotary blood pump invented for developing a total artificial heart (TAH). The HFP with a hydrodynamic levitation impeller, which consists of a multi-vane impeller involving rotor magnets, stator coils at the core position, and double helical-volute pump housing, was developed. Between the stator and impeller, a hydrodynamic bearing is formed. Since the helical volutes are formed at both sides of the impeller, blood flows with a helical flow pattern inside the pump. The developed HFP showed maximum output of 19 l/min against 100 mmHg of pressure head and 11 % maximum efficiency. The profile of the H-Q (pressure head vs. flow) curve was similar to that of the undulation pump. Hydrodynamic levitation of the impeller was possible with higher than 1,000 rpm rotation speed. The normalized index of the hemolysis ratio of the HFP to centrifugal pump (BPX-80) was from 2.61 to 8.07 depending on the design of the bearing. The HFP was implanted in two goats with a left ventricular bypass method. After surgery, hemolysis occurred in both goats. The hemolysis ceased on postoperative days 14 and 9, respectively. In the first experiment, no thrombus was found in the pump after 203 days of pumping. In the second experiment, a white thrombus was found in the pump after 23 days of pumping. While further research and development are necessary, we are expecting to develop an excellent TAH with the HFP.

Cell-membrane-inspired polymers for constructing biointerfaces with efficient molecular recognition.

Fabrication of devices that accurately recognize, detect, and separate target molecules from mixtures is a crucial aspect of biotechnology for applications in medical, pharmaceutical, and food sciences. This technology has also been recently applied in solving environmental and energy-related problems. In molecular recognition, biomolecules are typically complexed with a substrate, and specific molecules from a mixture are recognized, captured, and reacted. To increase sensitivity and efficiency, the activity of the biomolecules used for capture should be maintained, and non-specific reactions on the surface should be prevented. This review summarizes polymeric materials that are used for constructing biointerfaces. Precise molecular recognition occurring at the surface of cell membranes is fundamental to sustaining life; therefore, materials that mimic the structure and properties of this particular surface are emphasized in this article. The requirements for biointerfaces to eliminate nonspecific interactions of biomolecules are described. In particular, the major issue of protein adsorption on biointerfaces is discussed by focusing on the structure of water near the interface from a thermodynamic viewpoint; moreover, the structure of polymer molecules that control the water structure is considered. Methodologies enabling stable formation of these interfaces on material surfaces are also presented.

Photoinduced immobilization of 2-methacryloyloxyethyl phosphorylcholine polymers with different molecular architectures on a poly(ether ether ketone) surface.

Poly(ether ether ketone) (PEEK) has seen increasing use in biomedical fields as a replacement for metal implants. Accordingly, the surface functionalities of PEEK are important for the development of medical devices. We have focused on the application of photoinduced reactions in PEEK to immobilize a functional polymer via radical generation on the surface, which can react with hydrocarbon groups. In this study, we used zwitterionic copolymers comprising 2-methacryloyloxyethyl phosphorylcholine (MPC) units and n-butyl methacrylate (BMA) units with various molecular architectures for surface modification. A random copolymer (poly(MPC-co-BMA) (r-PMB)), an AB-type diblock copolymer (di-PMB), and an ABA-type triblock copolymer (tri-PMB) (A segment: poly(BMA); B segment: poly(MPC)) were synthesized with the same monomer compositions. All PMBs were successfully immobilized on the PEEK surface via UV irradiation after the dip-coating process, regardless of their molecular structure. In this reaction, the alkyl group of the BMA unit functioned as a photoreactive site on the PEEK surface. This indicates that the molecular structure differences affect the surface properties. For example, compared to r-PMB and tri-PMB, di-PMB-modified surfaces exhibited an extremely low water contact angle of approximately 10°. The findings of this study demonstrate that this surface functionalization method does not require a low-molecular-weight compound, such as an initiator, and can be applied to the surface of inert PEEK through a simple photoreaction under room temperature, atmospheric pressure, and dry state conditions.

Induction of mesenchymal stem cell differentiation by co-culturing with mature cells in double-layered 2-methacryloyloxyethyl phosphorylcholine polymer hydrogel matrices.

The effects of differentiated cells on stem cell differentiation were analyzed via co-culturing using a cell-encapsulated double-layered hydrogel system. As a polymer hydrogel matrix, a water-soluble zwitterionic polymer having both a 2-methacryloyloxyethyl phosphorylcholine unit and a p-vinylphenylboronic acid unit (PMBV), was complexed spontaneously with poly(vinyl alcohol) (PVA) under mild cell culture conditions. The creep modulus of the hydrogel was controlled by changing the composition of the polymer in the solution. Mouse mesenchymal stem cells (MSCs), C3H10T1/2 cells, were encapsulated into PMBV/PVA hydrogels and cultured. In the PMBV/PVA hydrogel with a lower creep modulus (0.40 kPa), proliferation of C3H10T1/2 cells occurred, and the formation of cell aggregates was observed. On the other hand, a higher creep modulus (1.7 kPa) of the hydrogel matrix prevented cell proliferation. Culturing C3H10T1/2 cells encapsulated in the PMBV/PVA hydrogel in the presence of bone morphogenetic protein-2 increased the activity of intracellular alkaline phosphatase (ALP). This indicated that C3H10T1/2 cells differentiated into mature osteoblasts. When the C3H10T1/2 cells encapsulated in the PMBV/PVA hydrogel were cultured in combination with the mature osteoblasts in the hydrogel by a close contacting double-layered hydrogel structure, higher ALP activity was observed compared with the cells cultured separately. It was considered that the differentiation of C3H10T1/2 cells in the hydrogel layer was induced by cytokines diffused from mature osteoblasts encapsulated in another hydrogel layer. It could be concluded that the PMBV/PVA hydrogel system provides a good way to observe the effects of the surrounding cells on cell function in three-dimensional culture.

Mechanical detection of interactions between proteins related to intermediate filament and transcriptional regulation in living cells.

Intermediate filaments (IF) bind to various proteins and regulate cell function in the cytoplasm. Recently, IFs were found to regulate gene expression by acting as capture scaffolds for transcription-related proteins and preventing their translocation into the nucleus. To reveal such transcriptional regulatory mechanisms controlled by IFs, a method to analyze the interaction between IFs and transcription-related proteins is necessary. Although there are many methods to observe interactions in living cells, it is still challenging to measure protein-protein interactions in living cells in their unmodified and native state. In this study, we utilized a nanoneedle that can access the cytosol by insertion into the cell. Modification of antibody recognizing transcription-related proteins allows the needle to detect mechanical force required to unbind the interaction between antibody and target proteins interacting with IFs during retraction of the needle from the cell. We focused on IF vimentin, a marker of epithelial-mesenchymal transition, to mechanically detect transcription-related proteins trapped by vimentin filaments. Prohibitin 2 (PHB2), a transcription-related factor, was selected as the candidate vimentin-binding protein. We conducted mechanical detection of PHB2 using atomic force microscopy and anti-PHB2 antibody-modified nanoneedles in vimentin-expressing mouse breast cancer and vimentin-knockout (VKO) cells. Significantly larger unbinding forces were detected in the vimentin-expressing cells than in the VKO cells. The results demonstrate that this method is useful for in-cell mechanical detection of IF-binding proteins.

Direct photoreactive immobilization of water-soluble phospholipid polymers on substrates in an aqueous environment.

The purpose of this study is to achieve a simpler and safer surface modification of substrates using a photoreactive polymer in an aqueous environment. We synthesized water-soluble photoreactive polymers with both phenylazide groups and phosphorylcholine groups, poly(2-methacryloyloxyethyl phosphorylcholine-co-4-methacryl tetra(ethylene glycol)oxycarbonyl-4-phenylazide) (PMEPAz), via reversible addition fragmentation chain transfer polymerization. PMEPAz with different polymerization degrees were synthesized with a well-defined structure. To immobilize PMEPAz on the substrate surface by photoreaction, it is necessary to adsorb the polymer on the substrate surface in an aqueous solution because the phenylazide groups chemically bind to the substrate via a hydrogen abstract reaction. The relationship between the polymer solubilization state in the aqueous solution and the adsorption behavior at the surface was investigated. PMEPAz began to form unstable molecular aggregates at a concentration of 10-2 mg/mL and formed stable aggregates at 100 mg/mL. At a concentration of 10-1 mg/mL, unstable molecular aggregates of PMEPAz were formed in the aqueous solution, resulting in the maximization of the amount of adsorbed polymer and effective photoreaction with the substrate. The thickness of the reacted polymer layer on the substrate increased with an increase in the polymerization degree, a uniform polymer layer with a thickness of 3.4 nm was formed when the polymerization degree was 400. After surface modification, the hydrophobic surfaces of the original substrates became hydrophilic. Additionally, fibrinogen adsorption and platelet adhesion were effectively suppressed based on the characteristics of the phosphorylcholine unit.

Preparation of Magnetic Hydrogel Microparticles with Cationic Surfaces and Their Cell-Assembling Performance.

Cationic magnetic hydrogel microparticles with high retention on cell surfaces were prepared using a two-step procedure. Using these magnetic hydrogel microparticles, cells were clustered with each other, and cell aggregates were prepared effectively. Cross-linked poly(vinyl alcohol) (PVA) hydrogel microparticles containing iron oxide nanoparticles were prepared. The diameter of the microparticles was in the range of 200-500 nm. Water-soluble cationic polymers containing both trimethyl ammonium (TMA) groups and phenylboronic acid (PBA) groups were synthesized for the surface modification of the microparticles. To regulate the composition, electrically neutral phosphorylcholine groups were introduced into the polymer. Covalent bonds were formed between the hydroxy groups of PVA microparticles and PBA groups in the polymer. The surface zeta potential of the microparticles reflected the composition of the TMA groups. The particles responded to an external magnetic field and clustered rapidly. Microparticles were adsorbed on the floating cell surface and induced cell aggregation quickly when a magnetic field was applied. Under the most effective conditions, the diameter of the cell aggregates increased to approximately 1 mm after 30 min. Denser cell aggregates were formed by the synergistic effects of the magnetic field and the properties of the microparticles. The formed cell aggregates continued to grow for more than 4 days under an applied magnetic field, indicating that the ability of the cells in the aggregate to proliferate was well maintained.

Control of Cell-Substrate Binding Related to Cell Proliferation Cycle Status Using a Cytocompatible Phospholipid Polymer Bearing Phenylboronic Acid Groups.

To provide high-quality cellular raw materials for cell engineering and pharmaceutical engineering, a polymer substrate is prepared for cell separation focusing on the cell proliferation cycle. There are many types of sugar chains on cell membranes, which function as signaling molecules to control interactions with the exterior of the cell; their abundance changes during the cell-proliferation cycle. In this study, a phenylboronic acid group, which has affinity for sugar chains, is introduced into a polymer containing a phosphorylcholine group that does not induce cell activation. On the surface of this polymer, human promyelocytic leukemia cells can adhere. The adhesion rate is increased by pretreating the substrate with an alkaline solution. Moreover, cell adhesion is dependent on the sugar additive in the culture medium. Therefore, cell adhesion is governed by reactions between the sugar chain on the cell membrane and the phenylboronic acid groups on the substrate. It is revealed that the adhesion rate changes depending on the expression level of sugar chains related to the cell-proliferation cycle. Based on this, it may be proposed a cell proliferation cycle-specific separation process using the polymer substrate based on cell adhesion depending on sugar chain density.

Effects of molecular architecture of photoreactive phospholipid polymer on adsorption and reaction on substrate surface under aqueous condition.

Water-soluble photoreactive polymers with both phosphorylcholine and benzophenone groups were synthesized for the reaction between the polymers and the substrate in aqueous medium. To control the polymer architecture, the living radical polymerization method was applied to the copolymerization of 2-methacryloyloxyethyl phosphorylcholine and benzophenone methacrylates. These polymers possess various architectures, such as linear polymers, polymers with hydrophobic terminals, and 4-armed star-like polymers, that could promote their adsorption on the substrate surfaces. Additionally, two types of benzophenone groups were examined. Due to the bulky phosphorylcholine group, tetra(ethylene oxide) group as a spacer between polymer main chain and benzophenone group was considered. These polymers could adsorb on the surface in an aqueous medium, followed by reaction on the surface via photoirradiation depending on the chemical structure of the benzophenone group. The thickness of the polymer layer depended on the polymer architecture, i.e. a polymer with a hydrophobic terminal could form a thick layer. After modification, the contact angle by air in the aqueous medium decreased, compared to that on the base substrate. This was due to the hydrophilic nature based on the phosphorylcholine groups at the surface. The amount of proteins adsorbed on the surface also decreased because of the surface modification. These findings indicated that these water-soluble photoreactive polymers could be applied for the safer and effective surface modification of substrates via conventional photoirradiation without using an organic solvent.

Surface characterization of a silicone hydrogel contact lens having bioinspired 2-methacryloyloxyethyl phosphorylcholine polymer layer in hydrated state.

A silicone hydrogel contact lens material, with a unique chemical and physical structure has been designed for long-term ocular performance. Enhancement of this silicone hydrogel contact lens material was achieved through surface modification using a cross-linkable bioinspired 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, which creates a soft surface gel layer on the silicone hydrogel base material. The surface properties of this MPC polymer-modified lens were characterized under hydrated condition revealing, inter alia, its unique polymer structure, excellent hydrophilicity, lubricity, and flexibility. Analysis of the MPC polymer layer in a hydrated state was performed using a combination of a high-resolution environmental scanning electron microscopy and atomic force microscopy. Compared to the silicone hydrogel base material, this surface had a higher captive bubble contact angle, which corresponds to higher hydrophilicity of the surface. In addition, the hydrated MPC polymer layer exhibited an extremely soft surface and reduced the coefficient of friction by more than 80 %. These characteristics were attributed to the hydration state of the MPC polymer layer on the surface of the silicone hydrogel base material. Also, interaction force of protein deposition was lowered on the surface. Such superior surface properties are anticipated to contribute to excellent ocular performance.

Antifouling Silicone Hydrogel Contact Lenses with a Bioinspired 2-Methacryloyloxyethyl Phosphorylcholine Polymer Surface.

Inspired by the cell membrane surface as well as the ocular tissue, a novel and clinically applicable antifouling silicone hydrogel contact lens material was developed. The unique chemical and biological features on the surface on a silicone hydrogel base substrate were achieved by a cross-linked polymer layer composed of 2-methacryloyloxyethyl phosphorylcholine (MPC), which was considered important for optimal on-eye performance. The effects of the polymer layer on adsorption of biomolecules, such as lipid and proteins, and adhesion of cells and bacteria were evaluated and compared with several conventional silicone hydrogel contact lens materials. The MPC polymer layer provided significant resistance to lipid deposition as visually demonstrated by the three-dimensional confocal images of whole contact lenses. Also, fibroblast cell adhesion was decreased to a 1% level compared with that on the conventional silicone hydrogel contact lenses. The movement of the cells on the surface of the MPC polymer-modified lens material was greater compared with other silicone hydrogel contact lenses indicating that lubrication of the contact lenses on ocular tissue might be improved. The superior hydrophilic nature of the MPC polymer layer provides improved surface properties compared to the underlying silicone hydrogel base substrate.

Interface of Phospholipid Polymer Grafting Layers to Analyze Functions of Immobilized Oligopeptides Involved in Cell Adhesion.

The aim of this study was to design a material surface for use in the analysis of the behavior of biomolecules at the interface of direct cell contact. A superhydrophilic surface was prepared with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), which was grafted onto a substrate with controlled polymer chain density. An arginine-glycine-aspartic acid (RGD) peptide was immobilized at the surface of the polymer graft surface (PMPC-RGD surface). Initial adhesion of the cells to this substrate was observed. The PMPC-RGD surface could enable cell adhesion only through RGD peptide-integrin interactions. The density and movability of the RGD peptide at the terminal of the graft PMPC chain and the orientation of the RGD peptide affected the density of adherent cells. Thus, the PMPC graft surface may be a good candidate for a new platform with the ability to immobilize biomolecules to a defined position and enable accurate analysis of their effects on cells.