Simple Detection and Culture of Circulating Tumor Cells from Colorectal Cancer Patients Using Poly(2-Methoxyethyl Acrylate)-Coated Plates

Here we aimed to establish a simple detection method for detecting circulating tumor cells (CTCs) in the blood sample of colorectal cancer (CRC) patients using poly(2-methoxyethyl acrylate) (PMEA)-coated plates. Adhesion test and spike test using CRC cell lines assured efficacy of PMEA coating. A total of 41 patients with pathological stage II-IV CRC were enrolled between January 2018 and September 2022. Blood samples were concentrated by centrifugation by the OncoQuick tube, and then incubated overnight on PMEA-coated chamber slides. The next day, cell culture and immunocytochemistry with anti-EpCAM antibody were performed. Adhesion tests revealed good attachment of CRCs to PMEA-coated plates. Spike tests indicated that ~75% of CRCs from a 10-mL blood sample were recovered on the slides. By cytological examination, CTCs were identified in 18/41 CRC cases (43.9%). In cell cultures, spheroid-like structures or tumor-cell clusters were found in 18/33 tested cases (54.5%). Overall, CTCs and/or growing circulating tumor cells were found in 23/41 CRC cases (56.0%). History of chemotherapy or radiation was significantly negatively correlated with CTC detection (p = 0.02). In summary, we successfully captured CTCs from CRC patients using the unique biomaterial PMEA. Cultured tumor cells will provide important and timely information regarding the molecular basis of CTCs.

Cell Adhesion Strength Indicates the Antithrombogenicity of Poly(2-Methoxyethyl Acrylate) (PMEA): Potential Candidate for Artificial Small-Diameter Blood Vessel

Poly (2-methoxyethyl acrylate) (PMEA) is a US FDA-approved biocompatible polymer, although there is insufficient work on human umbilical vein endothelial cells (HUVECs) and platelet interaction analysis on PMEA-analogous polymers. In this study, we extensively investigated HUVEC–polymer and platelet–polymer interaction behavior by measuring the adhesion strength using single-cell force spectroscopy. Furthermore, the hydration layer of the polymer interface was observed using frequency-modulation atomic force microscopy. We found that endothelial cells can attach and spread on the PMEA surface with strong adhesion strength compared to other analogous polymers. We found that the hydration layers on the PMEA-analogous polymers were closely related to their weak platelet adhesion behavior. Based on our results, it can be concluded that PMEA is a promising candidate for the construction of artificial small-diameter blood vessels owing to the presence of IW and a hydration layer on the interface.

Roles of interfacial water states on advanced biomedical material design

When biomedical materials come into contact with body fluids, the first reaction that occurs on the material surface is hydration; proteins are then adsorbed and denatured on the hydrated material surface. The amount and degree of denaturation of adsorbed proteins affect subsequent cell behavior, including cell adhesion, migration, proliferation, and differentiation. Biomolecules are important for understanding the interactions and biological reactions of biomedical materials to elucidate the role of hydration in biomedical materials and their interaction partners. Analysis of the water states of hydrated materials is complicated and remains controversial; however, knowledge about interfacial water is useful for the design and development of advanced biomaterials. Herein, we summarize recent findings on the hydration of synthetic polymers, supramolecular materials, inorganic materials, proteins, and lipid membranes. Furthermore, we present recent advances in our understanding of the classification of interfacial water and advanced polymer biomaterials, based on the intermediate water concept.

Poly(2-Methoxyethyl Acrylate) (PMEA)-Coated Anti-Platelet Adhesive Surfaces to Mimic Native Blood Vessels through HUVECs Attachment, Migration, and Monolayer Formation

Confluent monolayers of human umbilical vein endothelial cells (HUVECs) on a poly(2-methoxyethyl acrylate) (PMEA) antithrombogenic surface play a major role in mimicking the inner surface of native blood vessels. In this study, we extensively investigated the behavior of cell–polymer and cell–cell interactions by measuring adhesion strength using single-cell force spectroscopy. In addition, the attachment and migration of HUVECs on PMEA-analogous substrates were detected, and the migration rate was estimated. Moreover, the bilateral migration of HUVECs between two adjacent surfaces was observed. Furthermore, the outer surface of HUVEC was examined using frequency-modulation atomic force microscopy (FM-AFM). Hydration was found to be an indication of a healthy glycocalyx layer. The results were compared with the hydration states of individual PMEA-analogous polymers to understand the adhesion mechanism between the cells and substrates in the interface region. HUVECs could attach and spread on the PMEA surface with stronger adhesion strength than self-adhesion strength, and migration occurred over the surface of analogue polymers. We confirmed that platelets could not adhere to HUVEC monolayers cultured on the PMEA surface. FM-AFM images revealed a hydration layer on the HUVEC surfaces, indicating the presence of components of the glycocalyx layer in the presence of intermediate water. Our findings show that PMEA can mimic original blood vessels through an antithrombogenic HUVEC monolayer and is thus suitable for the construction of artificial small-diameter blood vessels.

Foldable Bulk Anti-adhesive Polyacrylic Intraocular Lens Material Design and Fabrication for Posterior Capsule Opacification Prevention

Posterior capsular opacification (PCO) is a primary complication after phacoemulsification combined with intraocular lens (IOL) implantation, which is attributed to adhesion, proliferation, and migration of residual lens epithelial cells on IOL. Although surface hydrophilic coating is considered to be a powerful way to inhibit PCO incidence after surgery, it requires complex post-production processes, thus limiting their applicability. In comparison, bulk modification is a stable, effective, and facile IOL synthesis method for PCO prevention. Herein, a new anti-adhesive IOL material was designed and successfully synthesized by radical copolymerization of ethylene glycol phenyl ether methacrylate (EGPEMA) and 2-(2-ethoxyethoxy) ethyl acrylate (EA). The physicochemical properties of P(EGPEMA-co-EA) copolymer materials, including chemical structure, mechanical, thermal, surface, and optical properties, were analyzed by using ¹H NMR spectroscopy, FT-IR spectroscopy, tensile test, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angle measurement, and UV-vis spectroscopy. The elongation at break and the modulus of elasticity of the copolymer were tunable through the change of the composition of monomers. Compared to other components, the tensile results showed that P(EGPEMA-co-EA) materials (70% EGPEMA in mass ratio, F7) are suitable for the preparation of foldable intraocular lens with lower elastic modulus and higher elongation at break. TGA and DSC showed that the material has high thermal stability, and the glass transition temperature of F7 material is 16.1 °C. The water contact angle measurement results showed that the introduction of EA improved the hydrophilicity of the material. The percentage of transmittance of all copolymers at 400-800 nm is above 85%. Then, the biocompatibility of the materials was evaluated by in vitro assay and subcutaneous implantation. Both in vitro results and subcutaneous implantation experiments showed that the designed IOL materials exhibited a good anti-adhesion effect and no cytotoxicity. Finally, phacoemulsification and IOL intraocular implantation were performed, and the in vivo results confirmed the good PCO prevention ability as well as the biocompatibility of the new IOL materials.

Modulation of Biological Responses of Tumor Cells Adhered to Poly(2-methoxyethyl acrylate) with Increasing Cell Viability under Serum-Free Conditions

Circulating tumor cells in body fluids are important biomarkers in cancer diagnosis. The culture of tumor cells isolated from body fluids can provide intrinsic information about tumors and can be used to screen for the best anticancer drugs. However, the culture of primary tumor cells has been hindered by their low viability and difficulties in recapitulating the phenotype of primary tumors in in vitro culture. The culture of tumor cells under serum-free conditions is one of the methodologies to maintain the phenotype and genotype of primary tumors. Poly(2-methoxyethyl acrylate) (PMEA)-coated substrates have been investigated to prolong the proliferation of tumor cells under serum-free conditions. In this study, we investigated the detailed behavior and the mechanism of the increase in tumor cell viability after adherence to PMEA substrates. The blebbing formation of tumor cells on PMEA was attributed not to apoptosis but to the low adhesion strength of cells on PMEA. Moreover, blebbing tumor cells showed amoeboid movement and formed clusters with other cells via N-cadherin, leading to an increase in tumor cell viability. Furthermore, the behaviors of tumor cells adhered to PMEA under serum-free conditions were involved in the activation of the PI3K and Rho-associated protein kinase pathways. Thus, we propose that PMEA would be suitable for the development of devices to cultivate primary tumor cells under serum-free conditions for the label-free diagnosis of cancer.

Nanoscopic Analyses of Protein Adsorption on Poly(2-methoxyethyl acrylate) Surfaces for Tailoring Cell Adhesiveness

Regulation of protein adsorption on the surface of biomaterials is important for modulating cell adhesion. Two important proteins in this regard are fibrinogen and fibronectin. Poly(2-methoxyethyl acrylate) (PMEA) and its...

Effect of bound water content on cell adhesion strength to water-insoluble polymers

Adhesion of cells on biomaterials plays an essential role in modulating cellular functions. Although hydration of biomaterials occurs under biological conditions, it is challenging to systematically evaluate the correlation of hydrated water content in biomaterials with the cell adhesion strength. In this report, we investigated the effect of bound water content on the adhesion strength of cells on poly(2-methoxyethyl acrylate) (PMEA) analogue substrates. Water-insoluble PMEA analogues were synthesized to fabricate substrates with a systemically controlled bound water content. To assess the surface properties of their substrates, contact angle measurement, atomic force microscopy (AFM), and fluorescence measurement were conducted. To reflect the effect of bound water of PMEA analogues, the relationship between the bound water content and cell adhesion behavior was evaluated under serum-free condition. From the single cell force spectrometry (SCFS) and microscopic analysis, it revealed that the increment of bound water content on the substrates decreased cell adhesion strength and cell spreading on the substrates. The bound water content exhibited a good correlation with adhesion strength, spreading area, circularity, and aspect ratio of cells. Our findings indicate that the bound water content could contribute to the development of a novel biomaterial and evaluation of cell behaviors on biomaterials. STATEMENT OF SIGNIFICANCE: For coordinating cell functions, such as growth, mobility, and differentiation, modulating the adhesion strength between cells and their environments is important. Although the hydration to biomaterials has been reported to be closely related to a antifouling property, the effect of hydration water on the cell adhesion behavior is not well understood. We present the first demonstration of essential relationship between cell adhesion strength and hydrated water on a biomaterials surface using the water-insoluble polymers with different hydrated water content. The results reveal that the hydrated water content of polymer substrates strong correlation with adhesion strength of cells. Collectively, the hydrated water content of the biomaterials will be a predominant factor affecting the cell adhesion strength and behavior.

Attachment and Growth of Fibroblast Cells on Poly (2-Methoxyethyl Acrylate) Analog Polymers as Coating Materials

The regulation of adhesion and the subsequent behavior of fibroblast cells on the surface of biomaterials is important for successful tissue regeneration and wound healing by implanted biomaterials. We have synthesized poly(ω-methoxyalkyl acrylate)s (PMCxAs; x indicates the number of methylene carbons between the ester and ethyl oxygen), with a carbon chain length of x = 2–6, to investigate the regulation of fibroblast cell behavior including adhesion, proliferation, migration, differentiation and collagen production. We found that PMC2A suppressed the cell spreading, protein adsorption, formation of focal adhesion, and differentiation of normal human dermal fibroblasts, while PMC4A surfaces enhanced them compared to other PMCxAs. Our findings suggest that fibroblast activities attached to the PMCxA substrates can be modified by changing the number of methylene carbons in the side chains of the polymers. These results indicate that PMCxAs could be useful coating materials for use in skin regeneration and wound dressing applications.

Effect of interfacial structure based on grafting density of poly(2-methoxyethyl acrylate) on blood compatibility

An excellent blood-compatible polymer, poly(2-methoxyethyl acrylate) (PMEA), exhibits nanometer-scale phase-separated structures at the interface with water or phosphate-buffered saline (PBS), and fibrinogen adsorption is suppressed, especially on the water-rich region. To understand the correlation between the interfacial structure based on the grafting density of PMEA and blood compatibility, grafted PMEA (gPMEA) surfaces with controlled density were prepared by immobilizing thiol-terminated PMEA on a gold substrate. The amount of adsorbed fibrinogen and the number of adhered platelets on gPMEAs decreased first with the increasing grafting density (σ), but increased after showed minimum at σ of approximately 0.11 chains/nm². The interfacial structures of the gPMEA/PBS interface changed with grafting density, and the maximum area of water-rich region was obtained at σ = 0.11. The water contact angle at σ = 0.11 is smaller than that at the other grafting density. These results revealed that hydration to the polymer is very effective to suppress the platelet adhesion and water-rich region shows excellent blood compatibility on gPMEA surfaces. This work clearly indicated that the density of PMEA affects the interfacial structure and plays an important role in the blood compatibility of the material.

Effect of the Molecular Weight of Poly(2-methoxyethyl acrylate) on Interfacial Structure and Blood Compatibility

The blood-compatible polymer poly(2-methoxyethyl acrylate) (PMEA) is composed of nanometer-scale interfacial structures because of the phase separation of the polymer and water at the PMEA/phosphate-buffered saline (PBS) interface. We synthesized PMEA with four different molecular weights (19, 30, 44, and 183 kg/mol) to investigate the effect of the molecular weight on the interfacial structures and blood compatibility. The amounts of intermediate water and fibrinogen adsorption were not affected by the molecular weight of PMEA. In contrast, the degree of denaturation of adsorbed fibrinogen molecules and platelet adhesion increased as the molecular weight increased. Atomic force microscopy observation revealed that the domain size of the microphase separation structures observed at the PMEA/PBS interfaces drastically (nearly 3 times in the mean area of a domain) changed with the molecular weight. PMEA with a lower molecular weight showed a smaller polymer-rich domain size, as expected on the basis of the microphase separation of polymer-rich and water-rich domains. The small domain size suppressed the aggregation and denaturation of adsorbed fibrinogen molecules because only a few fibrinogen molecules were adsorbed on a domain. Increasing the domain size enhanced the denaturation of adsorbed fibrinogen molecules. Controlling the interfacial structures is crucial for ensuring the blood compatibility of polymer interfaces.

Thermosensitive Polymer Biocompatibility Based on Interfacial Structure at Biointerface

The interfacial structure of a thermosensitive biocompatible polymer, poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMe2MA), at the polymer/phosphate-buffered saline (PBS) interface was investigated by atomic force microscopy. A number of nanometer scale protrusions appeared at 37 °C and disappeared at 22 °C, reversibly. This structural change occurred above the lower critical solution temperature of PMe2MA in PBS (19 °C), indicating that the formation of protrusions was explained by the microphase separation of polymer and water at the interfacial region. The protein adsorption and platelet adhesion onto PMe2MA interface were drastically restrained at 22 °C compared to that at 37 °C. Detachment of NIH3T3 cells accompanied by the dissipation of protrusions on the PMe2MA interface was also demonstrated. These results indicate that the protrusions act as the scaffold for the protein adsorption and cell adhesion.

Designing Smart Biomaterials for Tissue Engineering

The engineering of human tissues to cure diseases is an interdisciplinary and a very attractive field of research both in academia and the biotechnology industrial sector. Three-dimensional (3D) biomaterial scaffolds can play a critical role in the development of new tissue morphogenesis via interacting with human cells. Although simple polymeric biomaterials can provide mechanical and physical properties required for tissue development, insufficient biomimetic property and lack of interactions with human progenitor cells remain problematic for the promotion of functional tissue formation. Therefore, the developments of advanced functional biomaterials that respond to stimulus could be the next choice to generate smart 3D biomimetic scaffolds, actively interacting with human stem cells and progenitors along with structural integrity to form functional tissue within a short period. To date, smart biomaterials are designed to interact with biological systems for a wide range of biomedical applications, from the delivery of bioactive molecules and cell adhesion mediators to cellular functioning for the engineering of functional tissues to treat diseases.

Monoether-Tagged Biodegradable Polycarbonate Preventing Platelet Adhesion and Demonstrating Vascular Cell Adhesion: A Promising Material for Resorbable Vascular Grafts and Stents

We developed a biodegradable polycarbonate that demonstrates antithrombogenicity and vascular cell adhesion via organocatalytic ring-opening polymerization of a trimethylene carbonate (TMC) analogue bearing a methoxy group. The monoether-tagged polycarbonate demonstrates a platelet adhesion property that is 93 and 89% lower than those of poly(ethylene terephthalate) and polyTMC, respectively. In contrast, vascular cell adhesion properties of the polycarbonate are comparable to those controls, indicating a potential for selective cell adhesion properties. This difference in the cell adhesion property is well associated with surface hydration, which affects protein adsorption and denaturation. Fibrinogen is slightly denatured on the monoether-tagged polycarbonate, whereas fibronectin is highly activated to expose the RGD motif for favorable vascular cell adhesion. The surface hydration, mainly induced by the methoxy side chain, also contributes to slowing the enzymatic degradation. Consequently, the polycarbonate exhibits decent blood compatibility, vascular cell adhesion properties, and biodegradability, which is promising for applications in resorbable vascular grafts and stents.