Establishment and Evaluation of a New Chemiluminescent Enzyme Immunoassay for Carcinoembryonic Antigen Adapted to the Fully Automated ACCESS® System

Peer Reviewe

Biomimetic polyelectrolyte coating of stem cells suppresses thrombotic activation and enhances its survival and function

Mesenchymal stem cells (MSCs) therapy is a promising approach for treating inflammatory diseases due to their immunosuppressive and tissue repair characteristics. However, allogenic transplantation of MSCs induces thrombotic complications in some patients which limits its potential for clinical translation. To address this challenge, we have exploited the bioactivity of heparin, a well-known anticoagulant and immunosuppressive polysaccharide that is widely used in clinics. We have developed a smart layer-by-layer (LbL) coating strategy using gelatin and heparin polymers exploiting their overall positive and negative charges that enabled efficient complexation with the MSCs' glycocalyx. The stable coating of MSCs suppressed complement attack and mitigated thrombotic activation as demonstrated in human whole blood. Gratifyingly, the MSC coating retained its immunosuppressive properties and differentiation potential when exposed to inflammatory conditions and differentiation factors. We believe the simple coating procedure of MSCs will increase allogenic tolerance and circumvent the major challenge of MSCs transplantation.publishedVersionPeer reviewe

Cell surface modification with polymers for biomedical studies

Surface modification of living cells with natural or synthetic polymers is a powerful and useful tool in biomedical science and engineering. Various functional groups and bioactive substances can be immobilized to the cell surface through covalent conjugation, hydrophobic interaction, or electrostatic interaction. In this review, we provide an overview of the methods and polymers employed in cell surface modification, including: (1) covalent conjugation utilizing amino groups of cell surface proteins, (2) hydrophobic interaction of amphiphilic polymers with a lipid bilayer membrane, and (3) electrostatic interactions between cationic polymers and a negatively charged cell surface. We also discuss their applications in studies on cell therapy, cell–cell interaction analysis, cell arrangement, and lineage determination of stem cells

Surface modification of islets with PEG-lipid for improvement of graft survival in intraportal transplantation.

BACKGROUND: Transplantation of islets of Langerhans (islets) is a promising technique for treating insulin-dependent diabetes mellitus (type I). One unsolved issue is the early graft loss due to inflammatory reactions triggered by blood coagulation and complement activation that occurs immediately after transplantation into the liver through the portal vein. Several proposed approaches for improvement of the graft survival include heparin coating and covalent poly(ethylene glycol) (PEG) conjugation. We previously have studied the improvement of graft survival by modification of islet surfaces using amphiphilic PEG-conjugated phospholipid and bioactive molecules. Here, we analyzed the effect of PEG-modification on the improvement of graft survival immediately after intraportal transplantation into streptozotocin-induced diabetic mice. METHODS: The surface of hamster islets was modified with PEG-lipid. PEG-lipid modified islets (PEG-islets) were transplanted into the liver through the portal vein of streptozotocin-induced diabetic mice. We measured the graft survival periods and blood insulin levels immediately after intraportal transplantation to determine the cell damage to islets. Histocytochemical analyses of liver were also performed postintraportal transplantation. RESULTS: The graft survival of PEG-islets was significantly prolonged compared with bare islets in livers of diabetic mice. Reduction of blood insulin level within 60 min after transplantation of PEG-islets suggests that the cell damage observed immediately after transplantation could be suppressed by surface modification with PEG in comparison with bare islets. CONCLUSION: Our approach for the improvement of graft survival will be useful in the clinical setting

Layer-by-layer co-immobilization of soluble complement receptor 1 and heparin on islets.

Early graft loss due to instant blood-mediated inflammatory reactions (IBMIRs) is a major obstacle of clinical islet transplantation; inhibition of blood coagulation and complement activation is necessary to inhibit IBMIRs. Here, human soluble form complement receptor 1 (sCR1) and heparin were co-immobilized onto the surfaces of islet cells. sCR1 molecules carrying thiol groups were immobilized through maleimide-poly(ethylene glycol)-phospholipids anchored in the lipid bilayers of islet cells. Heparin was immobilized on the sCR1 layer via the affinity between sCR1 and heparin, and additional layers of sCR1 and heparin were formed layer-by-layer. The sCR1 and heparin molecules in these layers maintained anti-complement activation and anti-coagulation activities, respectively. This promising method could be employed to reduce the number of islet cells required to reverse hyperglycemia and prolong graft survival in both allo- and xeno-islet transplantation

Immobilization of the soluble domain of human complement receptor 1 on agarose-encapsulated islets for the prevention of complement activation.

The transplantation of islets of Langerhans has been successfully applied to the treatment of insulin-dependent diabetes. However, a shortage of human donors is the hardest obstacle to overcome. We aimed to develop a bioartificial pancreas that can realize xeno-islet transplantation. The islets were encapsulated in agarose microbeads carrying the soluble domain of human complement receptor 1 (sCR1), which is an effective inhibitor of the classical and alternative complement activation pathways. When naked rat islets were cultured in rabbit serum, large amounts of insulin leaked from the damaged islets over the course of a few days incubation, but no damaged cells were observed among islets in sCR1-agarose microbeads cultured in rabbit serum for 4 days. Although low levels of insulin were detected in the rabbit serum, the insulin did not leak from damaged β-cells, it was physiological insulin secreted by the β-cells

Design of Biointerfaces for Regenerative Medicine

Understanding and controlling biological responses against artificial materials is important for the development of medical devices and therapies. Self-assembled monolayers (SAMs) of alkanethiols provide well-defined surfaces that can be manipulated by varying the terminal functional groups. Thus, SAMs have been extensively used as a platform for studying how artificial materials affect biological responses. Here, we review cell adhesion behavior in response to SAMs with various surface properties and the effects that adsorbed proteins have on subsequent cell adhesion. We also describe an application for SAMs as a substrate for culturing neural stem cells (NSCs). Substrates that induced the correct orientation of immobilized growth factors, like epidermal growth factor, improved the selection of a pure NSC population during cell expansion. In addition, we review new methodologies for using amphiphilic polymers to modify the surfaces of cells and tissues. Coating the cell surface with amphiphilic polymers that can capture and immobilize bioactive substances or cells represents a promising approach for clinical applications, particularly cellular therapies

Control of cell attachment through polyDNA hybridization.

Cell-cell interactions play vital roles in embryo development and in homeostasis maintenance. Such interactions must be stringently controlled for cell-based tissue engineering and regenerative medicine therapies, and methods for studying and controlling cell-cell interactions are being developed using both biomedical and engineering approaches. In this study, we prepared amphiphilic PEG-lipid polymers that were attached to polyDNA with specific sequences. Incubation of cells with the polyDNA-PEG-lipid conjugate transferred some of the polyDNA to the cells' surfaces. Similarly, polyDNA-PEG-lipid conjugate using polyDNA with a complementary sequence was introduced to the surfaces of other cells or to a substrate surface. Cell-cell or cell-substrate attachments were subsequently mediated via hybridization between the two complementary polyDNAs and monitored using fluorescence microscopy