Zwitterionic fibrous polypropylene assembled with amphiphatic carboxybetaine copolymers for hemocompatible blood filtration.

UNLABELLED: The present study serves three main functions. First, it presents a novel random copolymer, made of octadecyl acrylate hydrophobic blocks and 2-(dimethylamino)ethyl methacrylate hydrophilic groups, and it zwitterionic form. Second, random copolymer and zwitterionic random copolymer, OmDn and Z-OmDn, are used to modify polypropylene membranes by evaporation coating. Our investigations unveil that this method leads to sufficiently stable self-assembling provided a minimum number of hydrophobic repeat units of 77, which also corresponds to a hydrophobic degree of 74%. Third, antifouling and hemocompatible properties of membranes are thoroughly investigated using all types of blood cells separately, as well as challenging membranes against whole blood in static and dynamic conditions. Membranes modified with zwitterionic copolymer containing 26% of zwitterionic groups are shown to be highly antifouling and hemocompatible, for a coating density as low as 0.2mg/cm(2). Their application in a specially designed blood filtration module enabled to almost totally inhibit blood cells interactions with membrane material, as well as to importantly reduce platelet activation in the permeate (2.5-fold reduction). STATEMENT OF SIGNIFICANCE: The design of new zwitterionic copolymer material is proposed and demonstrated in this study. It was showed that hydrophobicoctadecyl acrylate segments can be introduced in the zwitterioniccarboxybetaine polymer chain with a well-controlled random sequence. Stable, efficient, and effective surface zwitterionization of hydrophobic polypropylene are obtained via grafting onto approach by evaporation-induced self-assembling coating. In the perspective of potential application, hemocompatible blood filtration was demonstrated with the excellent results of non-activated platelets obtained. DESIGN: New zwitterionicmaterial, amphiphatic carboxybetaine copolymers. DEVELOPMENT: Evaporation-induced self-assembling grafting. APPLICATION: Hemocompatible blood filtration.

The consideration of indolicidin modification to balance its hemocompatibility and delivery efficiency.

Indolicidin (IL) is an antimicrobial peptide (AMP), which has been utilized as a cell penetrating peptide (CPP) for drug delivery. However, the hemolysis restricts its clinical application. Therefore, we investigated the delivery efficiency and hemocompatibility of IL and its derivatives. The transportation of fluorophore to NIH/3T3 cells could be improved either by in accompany with these peptides or in the form of peptide-conjugates. The hydrophobicity scales of these peptides were calculated according to their residues, which were compared to their effects on hemolysis as well as cell uptake efficiency. The results suggested that the cell penetrability of IL and its derivatives was related to their hydrophobicity scales based on the octanol-interface scale (ΔGoct-if), whereas their hemolysis levels depended on the hydrophobicity scales based on interface (ΔGwif). Consequently, we designed two peptides, IL-R57F89 and SAP10, to validate the correlation. These two peptides had similar ΔGwif; however, the ΔGoct-if of SAP10 was much higher than that of IL-K7F89. Both IL-R57F89 and SAP10 demonstrated extremely low hemolysis. Compared to the limit cell uptake of SAP10, IL-R57F89 greatly promoted the delivery efficiency. These results were consistent to our prediction, suggesting that hydrophobicity scales should be a useful preliminary guidance for AMP-derived CPP design.

Toll-like receptor 6 and connective tissue growth factor are significantly upregulated in mitomycin-C-treated urothelial carcinoma cells under hydrostatic pressure stimulation.

BACKGROUND: Urothelial carcinoma (UC) is the most common histologic subtype of bladder cancer. The administration of mitomycin C (MMC) into the bladder after transurethral resection of the bladder tumor (TURBT) is a common treatment strategy for preventing recurrence after surgery. We previously applied hydrostatic pressure combined with MMC in UC cells and found that hydrostatic pressure synergistically enhanced MMC-induced UC cell apoptosis through the Fas/FasL pathways. To understand the alteration of gene expressions in UC cells caused by hydrostatic pressure and MMC, oligonucleotide microarray was used to explore all the differentially expressed genes. RESULTS: After bioinformatics analysis and gene annotation, Toll-like receptor 6 (TLR6) and connective tissue growth factor (CTGF) showed significant upregulation among altered genes, and their gene and protein expressions with each treatment of UC cells were validated by quantitative real-time PCR and immunoblotting. CONCLUSION: Under treatment with MMC and hydrostatic pressure, UC cells showed increasing apoptosis using extrinsic pathways through upregulation of TLR6 and CTGF.

Electrical stimulation to promote osteogenesis using conductive polypyrrole films.

In this study, we developed an electrical cell culture and monitoring device. Polypyrrole (PPy) films with different resistances were fabricated as conductive surfaces to investigate the effect of substrate-mediated electrical stimulation. The physical and chemical properties of the devices, as well as their biocompatibilities, were thoroughly evaluated. These PPy films had a dark but transparent appearance, on which the surface cells could be easily observed. After treating with the osteogenic medium, rat bone marrow stromal cells cultured on the PPy films differentiated into osteoblasts. The cells grown on the PPy films had up-regulated osteogenic markers, and an alkaline phosphatase activity assay showed that the PPy films accelerated cell differentiation. Alizarin red staining and calcium analysis suggested that the PPy films promoted osteogenesis. Finally, PPy films were subjected to a constant electric field to elucidate the effect of electrical stimulation on osteogenesis. Compared with the untreated group, electrical stimulation improved calcium deposition in the extracellular matrix. Furthermore, PPy films with lower resistances allowed larger currents to stimulate the surface cells, which resulted in higher levels of mineralization. Overall, these results indicated that this system exhibited superior electroactivity with controllable electrical resistance and that it can be coated directly to produce medical devices with a transparent appearance, which should be beneficial for research on electrical stimulation for tissue regeneration.

Strategy of Fc-recognizable Peptide ligand design for oriented immobilization of antibody.

A new strategy for designing a short-chain peptide ligand with high affinity to the Fc region of an antibody was proposed. The targeted antibody is human prostate specific antibody (PSA) derived from Mouse IgG2a. The ligand design strategy involves two major parts: binding site selection and peptide ligand design. One of the exposed hydrophobic patches near the bottom of the antibody's Fc region, identified from the molecular docking of naphthelene and end-capped tryptophan, was selected as the binding site. After examining the charge distribution around the binding site, various peptide ligands were designed according to the possible hydrophobic and electrostatic interactions. A peptide ligand, RRGW, was found to have high Fc binding affinity by the analysis of molecular dynamics (MD) simulation. The first two residues, two arginines, play an important role in electrostatic interaction between the peptide and the Fc region of the antibody. The fourth residue, the tryptophan, provides the VDW force; and the flexibility of peptide is achieved through the help of the third residue, the glycine. The binding affinity, recognition efficiency, and orientation factor were calculated from the results of surface plasmon resonance (SPR) measurements. The result shows that the dissociation constant is 5.56 × 10(-10) M(-1). We also found that the recognition efficiency and orientation factor on the ligand attached surface were much higher than those on negatively and positively charged surfaces. This approach provides a simple and fast strategy for small ligands design on oriented antibody immobilization.

Bacterial resistance control on mineral surfaces of hydroxyapatite and human teeth via surface charge-driven antifouling coatings.

This works reports a set of new functionalized polyethyleneimine (PEI) polymers, including a neutral PEGylated polymer PEI-g-PEGMA, a negatively charged polymer PEI-g-SA, and a zwitterionic polymer PEI-g-SBMA, and their use as antibiofouling coating agent for human teeth protection. Polymers were synthesized by Michael addition, XPS analysis revealed that each polymer could be efficiently coated onto hydroxyapatite, ceramic material used as a model tooth. Polymers carrying a negative net charge were more efficiently adsorbed, because of the establishment of electrostatic interactions with calcium ions. Protein adsorption tests revealed that two factors were important in the reduction of protein adsorption. Both the surface charge and the surface ability to bind and entrap water molecules had to be considered. PEI-g-SBMA, which zeta potential in PBS solution was negative, was efficient to inhibit the adsorption of BSA, a negative protein. On the other hand, it also resisted the adsorption of lysozyme, a positive protein, because zwitterionic molecules can easily entrap water and provide a very hydrophilic environment. Streptococcus mutans attachment tests performed unveiled that all modified polymers were efficient to resist this type of bacteria responsible for dental carries. Best results were also obtained with PEI-g-SBMA coating. This polymer was also shown to efficiently resist the adsorption of positively charged bacteria (Stenotrophomonas maltophilia). Tests performed on real human tooth showed that PEI-g-SBMA could inhibit up to 70% of bacteria adhesion, which constitutes a major result considering that surface of teeth is very rough, therefore physically promoting the attachment of proteins and bacteria.

Hydrostatic pressure enhances mitomycin C induced apoptosis in urothelial carcinoma cells.

OBJECTIVES: Urothelial carcinoma (UC) of the bladder is the second most common cancer of the genitourinary system. Clinical UC treatment usually involves transurethral resection of the bladder tumor followed by adjuvant intravesical immunotherapy or chemotherapy to prevent recurrence. Intravesical chemotherapy induces fewer side effects than immunotherapy but is less effective at preventing tumor recurrence. Improvement to intravesical chemotherapy is, therefore, needed. METHODS AND MATERIALS: Cellular effects of mitomycin C (MMC) and hydrostatic pressure on UC BFTC905 cells were assessed. The viability of the UC cells was determined using cellular proliferation assay. Changes in apoptotic function were evaluated by caspase 3/7 activities, expression of FasL, and loss of mitochondrial membrane potential. RESULTS: Reduced cell viability was associated with increasing hydrostatic pressure. Caspase 3/7 activities were increased following treatment of the UC cells with MMC or hydrostatic pressure. In combination with 10 kPa hydrostatic pressure, MMC treatment induced increasing FasL expression. The mitochondria of UC cells displayed increasingly impaired membrane potentials following a combined treatment with 10 µg/ml MMC and 10 kPa hydrostatic pressure. CONCLUSIONS: Both MMC and hydrostatic pressure can induce apoptosis in UC cells through an extrinsic pathway. Hydrostatic pressure specifically increases MMC-induced apoptosis and might minimize the side effects of the chemotherapy by reducing the concentration of the chemical agent. This study provides a new and alternative approach for treatment of patients with UC following transurethral resection of the bladder tumor.

The regulation of DNA adsorption and release through chitosan multilayers.

To sustain transgene expression, chitosan was studied to immobilize DNA using layer-by-layer assembly to form polyelectrolyte multilayers (PEMs). Higher DNA concentrations and longer deposition periods demonstrated more DNA adsorptions to PEMs. By adjusting pH and the molecular weight of chitosan, PEM structures were manipulated. Chitosan molecules adsorption to PEMs increased when they were at pH 6 because of their low protonation. Furthermore, the configuration of chitosan favored a coiled-form when the pH was high, as the intramolecular repulsion decreased. Therefore, interdiffusion of polyelectrolytes in PEMs was promoted to increase DNA adsorption, especially for chitosan with high molecular weight. For the release experiments, because PEMs fabricated by lower pH chitosan owned less chitosan molecules, DNA release was enhanced. However, this phenomenon did not happen to chitosan with high molecular weight, which should be due to the entanglement between polymer chains. This comprehensive approach should be beneficial to substrate-mediated gene delivery applications.

A novel application of indolicidin for gene delivery.

A bovine derived antimicrobial peptide, indolicidin (IL), was studied of its new application for gene transfer. Plasmid DNA was complexed with both IL and polyethylenimine (PEI) as ternary particles. Compared to DNA/IL complexes, the DNA/IL/PEI particles demonstrated high zeta potentials, small particle sizes, and superior loading efficiencies, suggesting the incorporation of polycations can support IL for gene delivery. For in vitro experiments, these ternary particles significantly improved gene transfection efficiencies over the sole administrations of IL or PEI. This synergistic effect revealed that IL and PEI may play different roles for gene transfer. Our results suggest that IL should be a potential carrier for gene delivery. As our knowledge, our study should be the first article indicating the carrier ability of IL for gene transfer.

Interfacially polymerized layers for oxygen enrichment: a method to overcome Robeson's upper-bound limit.

Interfacial polymerization of four aqueous phase monomers, diethylenetriamine (DETA), m-phenylenediamine (mPD), melamine (Mela), and piperazine (PIP), and two organic phase monomers, trimethyl chloride (TMC) and cyanuric chloride (CC), produce a thin-film composite membrane of polymerized polyamide layer capable of O2/N2 separation. To achieve maximum efficiency in gas permeance and O2/N2 permselectivity, the concentrations of monomers, time of interfacial polymerization, number of reactive groups in monomers, and the structure of monomers need to be optimized. By controlling the aqueous/organic monomer ratio between 1.9 and 2.7, we were able to obtain a uniformly interfacial polymerized layer. To achieve a highly cross-linked layer, three reactive groups in both the aqueous and organic phase monomers are required; however, if the monomers were arranged in a planar structure, the likelihood of structural defects also increased. On the contrary, linear polymers are less likely to result in structural defects, and can also produce polymer layers with moderate O2/N2 selectivity. To minimize structural defects while maximizing O2/N2 selectivity, the planar monomer, TMC, containing 3 reactive groups, was reacted with the semirigid monomer, PIP, containing 2 reactive groups to produce a membrane with an adequate gas permeance of 7.72 × 10(-6) cm(3) (STP) s(-1) cm(-2) cm Hg(-1) and a high O2/N2 selectivity of 10.43, allowing us to exceed the upper-bound limit of conventional thin-film composite membranes.

Structural stability-chromatographic retention relationship on exenatide diastereomer separation.

In this study, the relationship of the structural stability of peptide diastereomers in elution solvents and their retention behaviors in reversed-phase chromatography (RPC) was examined to provide guidance on the solvent selection for a better separation of peptide diastereomers. We investigated the chromatographic retention behaviors of exenatide, a peptide drug for the treatment of type II diabetes mellitus and its three diastereomers using RPC and implicit molecular dynamics (MD) simulation analysis. Three diastereomers involved in the single serine residue mutation of D-form at the 11th, 32nd, and 39th residues were investigated in this study. Results show that the order of the solution structural stability of exenatide and its diastereomers is consistent with their retention order by 36 % acetonitrile/water elution. The sample loading solvent also affects the retention behaviors of exenatide peptide diastereomers in RPC column. Furthermore, a larger solution conformation energy difference of the critical pair of exenatide and its diastereomer (D-Ser39) at the elution solvent of 32 % tetrahydrofuran/water were obtained by MD simulation, and baseline separation was proved experimentally. In summary, we demonstrated that the solution structural stability-chromatographic retention relationship could be a powerful tool for elution solvent selection in peptide chromatographic purification, especially valuable for the separation of critical pair of diastereomers.

Use of biotinylated chitosan for substrate-mediated gene delivery.

To improve transfection efficiency of nonviral vectors, biotinylated chitosan was applied to complex with DNA in different N/P ratios. The morphologies and the sizes of formed nanoparticles were suitable for cell uptake. The biotinylation decreased the surface charges of nanoparticles and hence reduced the cytotoxicity. The loading capacities of chitosan were slightly decreased with the increase of biotinylation, but most of the DNA molecules were still complexed. Using different avidin-coated surfaces, the interaction between biotinylated nanoparticles to the substrate may be manipulated. The in vitro transfection results demonstrated that biotinylated nanoparticles may be bound to avidin coated surfaces, and the transfection efficiencies were thus increased. Through regulating the N/P ratio, biotinylation levels, and surface avidin, the gene delivery can be optimized. Compared to the nonmodified chitosan, biotinylated nanoparticles on biomaterial surfaces can increase their chances to contact adhered cells. This spatially controlled gene delivery improved the gene transfer efficiency of nonviral vectors and could be broadly applied to different biomaterial scaffolds for tissue engineering applications.

Molecular dynamics simulation of the induced-fit binding process of DNA aptamer and L-argininamide.

Aptamers are rare functional nucleic acids with binding affinity to and specificity for target ligands. Recent experiments have lead to the proposal of an induced-fit binding mechanism for L-argininamide (Arm) and its binding aptamer. However, at the molecular level, this mechanism between the aptamer and its coupled ligand is still poorly understood. The present study used explicit solvent molecular dynamics (MD) simulations to examine the critical bases involved in aptamer-Arm binding and the induced-fit binding process at atomic resolution. The simulation results revealed that the Watson-Crick pair (G10-C16), C9, A12, and C17 bases play important roles in aptamer-Arm binding, and that binding of Arm results in an aptamer conformation optimized through a general induced-fit process. In an aqueous solution, the mechanism has the following characteristic stages: (a) adsorption stage, the Arm anchors to the binding site of aptamer with strong electrostatic interaction; (b) binding stage, the Arm fits into the binding site of aptamer by hydrogen-bond formation; and (c) complex stabilization stage, the hydrogen bonding and electrostatic interactions cooperatively stabilize the complex structure. This study provides dynamics information on the aptamer-ligand induced-fit binding mechanism. The critical bases in aptamer-ligand binding may provide a guideline in aptamer design for molecular recognition engineering.

Adsorption of antimicrobial indolicidin-derived peptides on hydrophobic surfaces.

The hydrophobic interaction between antimicrobial peptides and membrane hydrophobic cores is usually related to their cytotoxicity. In this study, the adsorption mechanism of five plasma membrane-associated peptides, indolicidin (IL) and its four derivatives, with hydrophobic ligands was investigated to understand the relationship between peptide hydrophobicity and bioactivity. The hydrophobic adsorption mechanisms of IL and its derivatives were interpreted thermodynamically and kinetically by reversed-phase chromatography (RPC) analysis and surface plasmon resonance (SPR) measurement, respectively. IL and its derivatives possess a similar random coil structure in both aqueous and organic solvents. Thermodynamic analysis showed that the binding enthalpy of peptides with higher electropositivity was lower than those with lower electropositivity and exhibited unfavorable binding entropy. Higher electropositivity peptides adsorbed to the hydrophobic surface arising from the less bound solvent on the peptide surface. A comparison with the kinetic analysis showed that IL and its derivatives adopt a two-state binding model (i.e., adsorption onto and self-association on the hydrophobic acyl chain) to associate with the hydrophobic surface, and the binding affinity of peptide self-association correlates well with peptide hemolysis. Consequently, this study provided a novel concept for understanding the action of plasma membrane-associated peptides.

Biofouling resistance of ultrafiltration membranes controlled by surface self-assembled coating with PEGylated copolymers.

Block and random PEGylated copolymers of poly(ethylene glycol) methacrylate (PEGMA) and polystyrene (PS) were synthesized with a controlled polydispersity using an atom transfer radical polymerization method and varying molar mass ratios of PS/PEGMA. Two types of PEGylated copolymers were self-assembly coated onto the surface of poly(vinylidene fluoride) (PVDF) ultrafiltration membranes for enhancing biofouling resistance. It was found that the adsorption capacities of random copolymers on PVDF membranes were all higher than those of block copolymers. However, the specific and overall protein resistance of bovine serum albumin (BSA) on PVDF membranes coated with block copolymers was much higher than that with random copolymers. The increase in styrene content in copolymer increased the amount of polymer coating on the membrane, and the increase in PEGMA content enhanced the protein resistance of membranes. The optimum PS/PEGMA ratio was found to be close to 2 for the best resistance of protein adsorption and bacterial adhesion on the PEGylated diblock copolymer-coated membranes. The PVDF membrane coated with such a copolymer owned excellent biofouling resistance to BSA, humic acid, negatively surface charged bacteria E. coli, and positively surface charged bacteria S. maltophilia.

Hemocompatible mixed-charge copolymer brushes of pseudozwitterionic surfaces resistant to nonspecific plasma protein fouling.

In this work, the hemocompatibility of a sulfobetaine-like copolymer brush resulting from a mixed-charge copolymerization of the positively charged 11-mercapto-N,N,N-trimethylammonium chloride (TMA) and negatively charged 11-mercaptoundecylsulfonic acid (SA) was studied. Mixed charge distribution in the prepared poly(TMA-co-SA) copolymer brushes was controlled by the regulation of the reaction rate of the surface-initiated atom transfer radical polymerization (ATRP). The adsorption behavior of plasma proteins on a surface grafted with poly(TMA-co-SA) was measured by a surface plasmon resonance (SPR) sensor. The effects of varying temperature, solution pH, and ionic strength on the antifouling characteristics of the mixed-charge copolymer brushes were systematically evaluated, and the protein-fouling resistance was discussed in detail, especially with respect to the effect of ionic strength on the intra- and intermolecular interactions of the poly(TMA-co-SA) with proteins. The adhesion and activation of blood cells on the poly(TMA-co-SA)-grafted surface in contact with human whole blood was also demonstrated. The results suggest that mixed-charge copolymer brushes of poly(TMA-co-SA), which, like zwitterionic homopolymer brushes, have overall charge neutrality, can be used in similar applications for protein-fouling resistance and have excellent hemocompatibility with human whole blood at physiologic temperatures.

A systematic SPR study of human plasma protein adsorption behavior on the controlled surface packing of self-assembled poly(ethylene oxide) triblock copolymer surfaces.

A well-controlled biocompatible nonfouling surface is significant for biomedical requirements, especially for the improvement of biocompatibility. We demonstrate the low or nonbiofouling surfaces by coating hydrophobic-hydrophilic triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) on the CH(3)-terminated self-assembled monolayer (SAM). Two types of copolymers are used to modify the surface, one with different PEO/PPO ratios ( approximately 20/80, 40/60, and 80/20, w/w) but the same PPO molecular weight ( approximately 2 k), the other with different copolymer MWs ( approximately 9, 11, and 15 k) but the same PEO/PPO ratio (80/20, w/w). In situ surface plasmon resonance (SPR) sensor is used to evaluate polymer adsorption on the SAMs and subsequent protein adsorption on the copolymer-treated surface. The effects of PEO-PPO-PEO molecular weight, PPO-to-PEO ratio, and ionic strength on protein adsorption from single protein solutions of fibrinogen, BSA, and complex mixed proteins are systematically investigated. A Pluronic F108 treated surface is highly resistant to nonspecific protein adsorption under the optimized conditions (MW of 15 k and PEO/PPO ratio of 80/20). This work demonstrates that the PEO-PPO-PEO polymer is able to achieve ultra low fouling surface via surface modification by controlling surface packing density of polymers (molecular weight, hydrophobic/hydrophilic ratio, and hydrophilic group coverage).

Dual-thermoresponsive phase behavior of blood compatible zwitterionic copolymers containing nonionic poly(N-isopropyl acrylamide).

Thermoresponsive statistical copolymers of zwitterionic sulfobetaine methacrylate (SBMA) and nonionic N-isopropylacrylamide (NIPAAm) were prepared with an average molecular weight of about 6.0 kDa via homogeneous free radical copolymerization. The aqueous solution properties of poly(SBMA-co-NIPAAm) were measured using a UV--visible spectrophotometer. The copolymers exhibited controllable lower and upper critical solution temperatures in aqueous solution and showed stimuli-responsive phase transition in the presence of salts. Regulated zwitterionic and nonionic molar mass ratios led to poly(SBMA-co-NIPAAm) copolymers having double-critical solution temperatures, where the water-insoluble polymer microdomains are generated by the zwitterionic copolymer region of polySBMA or nonionic copolymer region of polyNIPAAm depending on temperature. A high content of the nonionic polyNIPAAm in poly(SBMA-co-NIPAAm) exhibits nonionic aggregation at high temperatures due to the desolvation of polyNIPAAm, whereas relatively low content of polyNIPAAm in poly(SBMA-co-NIPAAm) exhibits zwitterionic aggregation at low temperatures due to the desolvation of polySBMA. Plasma protein adsorption on the surface coated with poly(SBMA-co-NIPAAm) was measured with a surface plasmon resonance (SPR) sensor. The copolymers containing polySBMA above 29 mol % showed extremely low protein adsorption and high anticoagulant activity in human blood plasma. The tunable and switchable thermoresponsive phase behavior of poly(SBMA-co-NIPAAm), as well as its high plasma protein adsorption resistance and anticoagulant activity, suggests a potential for blood-contacting applications.

Preparation of a DNA aptamer-Pt complex and its use in the colorimetric sensing of thrombin and anti-thrombin antibodies.

DNA aptamers carrying Pt nanoparticles were prepared by the reaction of DNA aptamers (without functionalization with biotin, thiol, or other reactive groups) with K 2[PtCl 4] in solution at 60-90 degrees C. The DNA-Pt complexes possessed peroxidase enzymatic activity while retaining the specific binding ability of the aptamers. The enzymatic reaction of these complexes obeyed Michaelis-Menten kinetics. K M for the DNA-Pt complex was found to be on the same order as K M for hemin and hemin-DNA complex but 1 or 2 orders of magnitude higher than that of horseradish peroxidase. The rate of the reaction catalyzed by the DNA-Pt complex, k cat, was found to be on the same order as that of hemin and hemin-DNA complex but 2 or 3 orders of magnitude lower than that of horseradish peroxidase. Two types of DNAzyme-linked aptamer assays (DLAAs) were developed using these complexes, which successfully detected target proteins, with the sandwich type of DLAA targeting thrombin and the competitive type of DLAA targeting anti-thrombin IgA/G/M in serum. The DNA-Pt complexes retained their peroxidase enzymatic activity even after heat treatment. DLAAs having high thermal stability were developed using these complexes, which were free of animal and plant matter because neither antibodies nor horseradish peroxidase were used in their synthesis.

A highly stable nonbiofouling surface with well-packed grafted zwitterionic polysulfobetaine for plasma protein repulsion.

An ideal nonbiofouling surface for biomedical applications requires both high-efficient antifouling characteristics in relation to biological components and long-term material stability from biological systems. In this study we demonstrate the performance and stability of an antifouling surface with grafted zwitterionic sulfobetaine methacrylate (SBMA). The SBMA was grafted from a bromide-covered gold surface via surface-initiated atom transfer radical polymerization to form well-packed polymer brushes. Plasma protein adsorption on poly(sulfobetaine methacrylate) (polySBMA) grafted surfaces was measured with a surface plasmon resonance sensor. It is revealed that an excellent stable nonbiofouling surface with grafted polySBMA can be performed with a cycling test of the adsorption of three model proteins in a wide range of various salt types, buffer compositions, solution pH levels, and temperatures. This work also demonstrates the adsorption of plasma proteins and the adhesion of platelets from human blood plasma on the polySBMA grafted surface. It was found that the polySBMA grafted surface effectively reduces the plasma protein adsorption from platelet-poor plasma solution to a level superior to that of adsorption on a surface terminated with tetra(ethylene glycol). The adhesion and activation of platelets from platelet-rich plasma solution were not observed on the polySBMA grafted surface. This work further concludes that a surface with good hemocompatibility can be achieved by the well-packed surface-grafted polySBMA brushes.