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A fusion protein, designated ELP-D-C, comprised of a hydrophobic elastin-like polypeptide unit, a hydrophilic aspartic acid-rich peptide unit, and an antibody-binding domain as a functional unit, was constructed. Upon heat induction, ELP-D-C forms micellar nanoparticles displaying antibody-binding domains on their surfaces. The protein nanoparticles were able to incorporate hydrophobic fluorescent compounds and subsequently detect target molecules via antibody binding by the resulting fluorescence intensity, which was proportional to the log of the concentration of the target molecule.

Supramolecular protein hydrogels with tunable properties represent promising candidates for advanced designer extracellular matrices (ECMs). To control cellular functions, ECMs should be able to spatiotemporally regulate synergistic signaling between transmembrane receptors and growth factor (GF) receptors. In this study, we developed genetically engineered temperature-responsive multifunctional protein hydrogels. The designed hydrogel was fabricated by combining the following four peptide blocks: thermosensitive elastin-like polypeptides (ELPs), a polyaspartic acid (polyD) chain to control aggregation and delivery of GFs, a de novo-designed helix peptide that forms antiparallel homotetrameric coiled-coils, and a biofunctional peptide. The resultant coiled-coil unit bound ELPs (CUBEs) exhibit a controllable sol-gel transition with tunable mechanical properties. CUBEs were functionalized with bone sialoprotein-derived RGD (bRGD), and human umbilical vein endothelial cells (HUVECs) were three-dimensionally cultured in bRGD-modified CUBE (bRGD-CUBE) hydrogels. Proangiogenic activity of HUVECs was promoted by bRGD. Moreover, heparin-binding angiogenic GFs were immobilized to bRGD-CUBEs via electrostatic interactions. HUVECs cultured in GF-tethered bRGD-CUBE hydrogels formed three-dimensional (3-D) tubulelike structures. The designed CUBE hydrogels may demonstrate utility as advanced smart biomaterials for biomedical applications. Further, the protein hydrogel design strategy may provide a novel platform for constructing designer 3-D microenvironments for specific cell types.

Artificial materials have no biological functions, but they are important for medical devices such as artificial organs and matrices for regenerative medicine. In this study, mitogenic and differentiation‐inducible materials are devised via the simple coating of polypeptides, which contain the sequence of epidermal growth factor or insulin‐like growth factor with a key amino acid (3,4‐dihydroxyphenylalanine) of underwater adhesive proteins. The adhesive polypeptides prepared via solid‐phase synthesis form layers on various substrates involving organic and inorganic materials to provide biological surfaces. Through the direct activation of cognate receptors on interactive surfaces, the materials enable increased cell growth and differentiation compared to that achieved by soluble growth factors. This superior growth and differentiation are attributed to the long‐lasting signal transduction (triggered by the bound growth factors), which do not cause receptor internalization and subsequent downregulation., 3,4‐dihydroxyphenylalanine‐containing peptides form bioactive layers on organic and inorganic material surfaces. On the adhesive growth factor nanolayers, cells receive long‐term biological signals from immobilized growth factors, leading to improved cell growth and differentiation.

COVID-19 pandemic situation demands effective serological tests with a view to adopting and developing policy for disease management, determining protective immunity as well as for sero-epidemiological study. Our study aims to develop and evaluate two rapid in-house ELISA assays targeting neutralizing antibodies (IgG) against S1 subunit of spike in SARS-CoV-2 and Receptor Binding Domain (RBD), as well as comparative analysis with nucleocapsid (NCP) ELISA. The assays were conducted with 184 samples in three panels collected from 134 patients. Panel 1 and 2 consist of RT-PCR positive samples collected within two weeks and after two weeks of symptom onset, respectively. Negative samples are included in panel 3 from healthy donors and pre-pandemic dengue patients. The total assay time has been set 30 minutes for both of the ELISA assays. Results show that S1 and RBD ELISA demonstrates 73.68% and 84.21% sensitivities, respectively for samples collected within two weeks, whereas 100% sensitivities were achieved by both for samples that were collected after two weeks of the onset of symptoms. S1-ELISA shows 0% positivity to panel 3 while for RBD-ELISA the figure is 1%. A strong correlation (rs=0.804, ps=0.800, ps=0.740, pHighlightsThe total assay time of these assays are 30 minutes.Sensitivity of S1 specific IgG ELISA for samples tested within 14 days of disease presentation is 73.68% while RBD specific ELISA demonstrates a sensitivity of 84.21%,Both of the assays under investigation can successfully detect all the cases (100% sensitivity) if the samples are tested after 14 days of onset of diseases.Specificity of S1-ELISA assay is 100%, whereas RBD specific IgG ELISA is 99% specific.The assays can be employed in dengue-endemic countriesAmong the three in-house IgG ELISA, assay system specific to S1 is found to be more sensitive and specific for retrospective serosurveillance.For acute to late phase, as well as retrospective serosurveillance of COVID-19, RBD-ELISA can be a method of choice for SARS-CoV-2 prevalent areas.

BackgroundIn the ongoing pandemic situation of COVID-19, serological tests can complement the molecular diagnostic methods, and can be one of the important tools of sero-surveillance and vaccine evaluation.AimTo develop and evaluate a rapid SARS-CoV-2 specific ELISA for detection of anti-SARS-CoV2 IgG from patient’s biological samples.MethodsIn order to develop the ELISA, three panels of samples (n=184) have been used: panel 1 (n=19) and panel 2 (n=60) were collected from RT-PCR positive patients within 14 and after 14 days of onset of clinical symptoms respectively, whereas panel 3 consisted of negative samples (n=105) collected either from healthy donors or pre-pandemic dengue patients. As a capturing agent full-length SARS-CoV2 specific recombinant nucleocapsid was immobilized. Commercial SARS-CoV2 IgG kit based on chemiluminescent assay was used for the selection of samples and optimization of the assay. The threshold cut-off point, inter-assay and intra-assay variations were determined. The total assay time for this in-house ELISA was set for 30 minutes.ResultsThe assay time was set at a total of 30 minutes with the sensitivity of 84% (95% confidence interval, CI, 60.4%, 96.6%) and 98% (95% CI, 91.1%, 100.0%), for panel 1 and 2 respectively, with over all 94.9% sensitivity (95% CI 87.5%, 98.6%). Moreover, the clinical specificity is 97.1% (95% CI, 91.9%, 99.4%) with no cross reaction with dengue sample. The overall positive and negative predictive values are 96.2% (95% CI 89.2%, 99.2%) and 96.2% (95% CI, 90.6% 99.0%) respectively. In-house ELISA demonstrated 100% positive and negative percent agreement with ROCHE (Elecsys; Anti-SARS-CoV-2), with a Cohen’s kappa value of 1.00 (very strong agreement), while comparing 13 positive and 17 negative confirmed cases.ConclusionThe assay is rapid and can be applied as one of the early and retrospective sero-monitoring tools in all over the affected areas.

Monoclonal antibodies have been developed as anticancer agents to block immune checkpoint pathways associated with programmed cell death 1 (PD-1) and its ligand PD-L1. However, the high cost of antibodies has encouraged researchers to develop other inhibitor types. Here, biphenyl compounds were conjugated with poly(ethylene glycol) (PEG) to enhance the activity of small molecular inhibitors. Immunoassay results revealed the decrease in the inhibition activity following conjugation with linear PEG, suggesting that the PEG moiety reduced the interaction between the biphenyl structure and PD-L1. However, the inhibitory effect on PD-1/PD-L1 interaction was further enhanced by using branched PEG conjugates. The increase in the number of conjugated biphenyl compounds resulted in increased inhibitory activity. The highest IC50 value was 0.33 μM, which was about 5 times higher than that observed for a non-conjugated monovalent compound. The inhibitory activity was more than 20 times the activity reported for the starting compound. Considering the increase in the inhibition activity, this multivalent strategy can be useful in the design of new immune checkpoint inhibitors.

E-cadherin is a key Ca-dependent cell adhesion molecule, which is expressed on many cell surfaces and involved in cell morphogenesis, embryonic development, EMT, etc. The fusion protein E-cad-Fc consists of the extracellular domain of E-cadherin and the IgG Fc domain. On plates coated with this chimeric protein, ES/iPS cells are cultivated particularly well and induced to differentiate. The cells adhere to the plate via E-cad-Fc in the presence of Ca2+ and detach by a chelating agent. For the purpose of clarifying the structures of E-cad-Fc in the presence and absence of Ca2+, we analyzed the molecular structure of E-cad-Fc by AFM in liquid. Our AFM observations revealed a rod-like structure of the entire extracellular domain of E-cad-Fc in the presence of Ca2+ as well as trans-binding of E-cad-Fc with adjacent molecules, which may be the first, direct confirmation of trans-dimerization of E-cadherin. The observed structures were in good agreement with an X-ray crystallographic model. Furthermore, we succeeded in visualizing the changes in the rod-like structure of the EC domains with and without calcium. The biomatrix surface plays an important role in cell culture, so the analysis of its structure and function may help promote cell engineering based on cell recognition.

Cancer immunotherapy has been revolutionized by the development of monoclonal antibodies (mAbs) that inhibit interactions between immune checkpoint molecules, such as programmed cell-death 1 (PD-1), and its ligand PD-L1. However, mAb-based drugs have some drawbacks, including poor tumor penetration and high production costs, which could potentially be overcome by small molecule drugs. BMS-8, one of the potent small molecule drugs, induces homodimerization of PD-L1, thereby inhibiting its binding to PD-1. Our assay system revealed that BMS-8 inhibited the PD-1/PD-L1 interaction with IC50 of 7.2 &mu, M. To improve the IC50 value, we designed and synthesized a small molecule based on the molecular structure of BMS-8 by in silico simulation. As a result, we successfully prepared a biphenyl-conjugated bromotyrosine (X) with IC50 of 1.5 &mu, M, which was about five times improved from BMS-8. We further prepared amino acid conjugates of X (amino-X), to elucidate a correlation between the docking modes of the amino-Xs and IC50 values. The results suggested that the displacement of amino-Xs from the BMS-8 in the pocket of PD-L1 homodimer correlated with IC50 values. This observation provides us a further insight how to derivatize X for better inhibitory effect.

In this study, we developed a protein nanoparticle-based immunoassay to detect cancer biomarkers using a bioluminescent fusion protein. This method relies on the use of protein nanoparticles comprised of genetically-engineered elastin-like polypeptides (ELPs) fused with poly-aspartic acid tails (ELP-D), previously developed in our lab. The sizes of the self-assembled ELP-D nanoparticles can be regulated at the nanoscale by charged repulsion of the poly-aspartic acid chains. To improve the sensitivity of enzyme-linked immunosorbent assays (ELISAs), we herein demonstrate the multivalent display of NanoLuc® (Nluc) luciferase and a biotin acceptor peptide (BAP) on the surfaces of ELP-D nanoparticles, and demonstrate the sensitivity of these multivalent nanoparticles as detection probes. The fusion protein comprised of ELP-D and Nluc-BAP (ELP-D-Nluc-BAP) was found to form nanoparticles with Nluc and BAP displayed multivalently on their surfaces. Moreover, the use of the nanoparticles in ELISA resulted in a detection sensitivity for α-fetoprotein (AFP) about 10 times higher than that of an assay relying on the use of the monomeric version of the fusion protein. Taken together, ELP-D-based nanoparticles displaying multivalent luciferases on their surfaces enable the construction of an ELISA with enhanced sensitivity.

Nanoparticles are small size-controlled particles from 1 to 100 nm diameters and characterized by their structure, base material and functional units displayed on their surfaces. In this study, protein-based nanoparticles composed of a hydrophobic elastin-like peptide unit, a hydrophilic aspartic acid-rich peptide unit and displaying antibody binding domains on their surfaces, were designed and genetically synthesized. The constituent fusion proteins, termed ELP-D-C, were found to exist in monomeric form (ELP-D-C/monomer) at low temperature. Above the phase transition temperature, however, ELP-D-C was found to rapidly self-assemble to form spherical micelles (ELP-D-C/micelle) with a hydrophobic core and diameters of ∼40 nm. Furthermore, ELP-D-C/micelle were shown to display antibody binding domains on their surfaces, which allowed for immobilization of antibodies and subsequent formation of large, visually detectable complexes in the presence of target molecule (antigen), whose sizes increased in proportion to the target molecule concentration. The observed target molecule concentration-dependent complex formation suggests that ELP-D-C/micelle may be useful as base particles in applications such as homogeneous turbidity immunoassays.

We constructed a novel peptide-array format system for cellular toxicity analysis. In this system, a peptide was immobilized on a conventional 96-well plate bottom via a photo-cleavable linker. Once UV light irradiated the desired wells, the peptide was released from the bottom. As a result, the cytotoxic behavior of the peptide could be monitored. Immobilization and light-irradiation conditions were optimized. The immobilized peptide showed no cytotoxicity; therefore, the cells could be cultured on the peptide-immobilizing plate from the beginning of the experiment. Cell-toxicity assays with this system for three cell types were performed. All cell types showed ∼25% lowering of viability with the photo-released 5-(and-6)-carboxytetramethylrhodamine (TMR)-GKLAKLAKKLAKLAKKLAKLAKGC (TMR-KLA-C) peptide compared with the non-coated plate. This relative toxicity nearly corresponded to that of ∼10 μM TMR-KLA-C in solution, and we found that the released peptide concentration per well was ∼10 μM at 60 min irradiation. Throughout this study, we successfully immobilized peptides via the photo-cleavable linker, released them by UV irradiation spatiotemporally and conducted the cell-toxicity assay. This study implies that the peptide photo-releasing array system will allow the realization of high-throughput cell arrays for cellomics analyses and cell-based phenotypic drug screenings. A novel peptide-array format system with a photo-cleavage linker for cellular toxicity analysis was constructed. In this system, a peptide was immobilized on a commercially available plate bottom via the photo-cleavable linker. UV light irradiation on the desired wells releases the peptide from the plate bottom, and then the cytotoxic behavior of the peptide can be monitored.

We explored the intra- and extracellular processes governing the kinetics of extracellular ATP (ATPe) in human erythrocytes stimulated with agents that increase cAMP. Using the luciferin-luciferase reaction in off-line luminometry we found both direct adenylyl cyclase activation by forskolin and indirect activation through β-adrenergic stimulation with isoproterenol-enhanced [ATP]e in a concentration-dependent manner. A mixture (3V) containing a combination of these agents and the phosphodiesterase inhibitor papaverine activated ATP release, leading to a 3-fold increase in [ATP]e, and caused increases in cAMP concentration (3-fold for forskolin + papaverine, and 10-fold for 3V). The pannexin 1 inhibitor carbenoxolone and a pannexin 1 blocking peptide ((10)Panx1) decreased [ATP]e by 75-84%. The residual efflux of ATP resulted from unavoidable mechanical perturbations stimulating a novel, carbenoxolone-insensitive pathway. In real-time luminometry experiments using soluble luciferase, addition of 3V led to an acute increase in [ATP]e to a constant value of ∼1 pmol × (10(6) cells)(-1). A similar treatment using a surface attached luciferase (proA-luc) triggered a rapid accumulation of surface ATP levels to a peak concentration of 2.4 pmol × (10(6) cells)(-1), followed by a slower exponential decay (t(frac12;) = 3.7 min) to a constant value of 1.3 pmol × (10(6) cells)(-1). Both for soluble luciferase and proA-luc, ATP efflux was fully blocked by carbenoxolone, pointing to a 3V-induced mechanism of ATP release mediated by pannexin 1. Ecto-ATPase activity was extremely low (∼28 fmol × (10(6) cells min)(-1)), but nevertheless physiologically relevant considering the high density of erythrocytes in human blood.

Endothelial cells (ECs) release ATP in response to shear stress, a fluid mechanical force generated by flowing blood but, although its release has a crucial role in controlling a variety of vascular functions by activating purinergic receptors, the mechanism of ATP release has never been established. To analyze the dynamics of ATP release, we developed a novel chemiluminescence imaging method by using cell-surface-attached firefly luciferase and a CCD camera. Upon stimulation of shear stress, cultured human pulmonary artery ECs simultaneously released ATP in two different manners, a highly concentrated, localized manner and a less concentrated, diffuse manner. The localized ATP release occurred at caveolin-1-rich regions of the cell membrane, and was blocked by caveolin-1 knockdown with siRNA and the depletion of plasma membrane cholesterol with methyl-β-cyclodexrin, indicating involvement of caveolae in localized ATP release. Ca2+ imaging with Fluo-4 combined with ATP imaging revealed that shear stress evoked an increase in intracellular Ca2+ concentration and the subsequent Ca2+ wave that originated from the same sites as the localized ATP release. These findings suggest that localized ATP release at caveolae triggers shear-stress-dependent Ca2+ signaling in ECs.

The interaction between proteins and ligands was evaluated by T7 RNA polymerase transcription with a DNA-modified ligand. The principle of this method is suppression of T7 RNA polymerase transcription by binding of a protein to small ligand modified by conjugation with a T7 RNA polymerase promoter. To demonstrate proof of principle, biotin or antifolate methotrexate was modified by covalent attachment of a T7 RNA promoter. Using these T7 RNA promoter-modified ligands, T7 RNA polymerase transcriptions were performed in the presence or absence of an anti-biotin antibody or recombinant human dihydrofolate reductase, respectively. Transcription was suppressed in the presence of each binding protein plus its modified ligand, but not in the absence of the binding protein.

A novel protein for controlling cellular functions was constructed by combining functional units of various proteins. The Arg-Gly-Asp (RGD) sequence functioning as a cell adhesive function, an epidermal growth factor (EGF) as a cell growth function, and a hydrophobic sequence (E12) as an efficient assembling function, were combined and incorporated into one molecule. The fusion protein, designated ERE-EGF, was produced in Escherichia coli and purified with affinity chromatography using a His-tag. The ERE-EGF coated on an unmodified hydrophobic surface of a cell-culture plate (through the hydrophobic E12 moiety) retained both cell adhesive activity (through the RGD sequence) and cell growth activity (through the EGF moiety).

In order to assess blood pressure control drugs, the endothelial cellular biosensing system for assessing blood pressure control drugs was constructed. This system consists of human umbilical vein endothelial cells (HUVEC) on a polyion-coated gold electrode, a platinum counter electrode and an Ag/AgCl reference electrode. Nitric oxide (NO) as an indicator of blood vessel relaxation was detected with a polyion-coated electrode in the system. The NO detection limit of this electrode was 8.4 nM by differential pulse voltammetry (DPV). The drugs of blood pressure control (acetylcholine chloride (AcChCl), NOC 7 and NG-monomethyl-L-arginine (L-NMMA)) were assessed with this endothelial cellular biosensing system. One milli molar of AcChCl make NO released from HUVEC stimulated by activating endothelial nitric oxide synthase (eNOS) in HUVEC. In the case of 5 mM of L-NMMA, NO releasing was inhibited by inhibiting eNOS activation by 1 mM of AcChCl. NOC 7 immediately released NO regardless of eNOS activation in endothelial cells.

Exocytosis in pheochromocytoma cells was induced by electric stimulation. To chase the movement of vesicles by electric stimulation, dense-core secretory vesicles were visualized by expression of the fusion protein between neuropeptide Y and enhanced green fluorescent protein (EGFP) in these differentiated PC12 rat pheochromocytoma cells. When the cells were stimulated with constant voltage potential at −300 mV, the movement of dense-core secretory vesicles could be regulated.

To monitor the extent of cellular physiological stress, the activity of the rpoS promoter was evaluated as a marker of the stress pathway. A reporter plasmid was constructed by inserting the GFPuv gene under the rpoS promoter and used to transform Escherichia coli cells. The fluorescence of the GFPuv protein was measured in intact cells in a non-destructive manner. The physiological status of the cells could be conveniently monitored using the rpoS –GFPuv reporter gene with respect to the cellular growth phase and to elevated ethanol and NaCl concentrations as two examples of environmental stress factors. Comparison of the response of different E. coli strains demonstrated an essential role of the relA gene in the induction of the rpoS –GFPuv reporter gene.

Cellular microenvironments are generally sophisticated, but crucial for regulating the functions of human pluripotent stem cells (hPSCs). Despite tremendous effort in this field, the correlation between the environmental factors-especially the extracellular matrix and soluble cell factors-and the desired cellular functions remains largely unknown because of the lack of appropriate tools to recapitulate in vivo conditions and/or simultaneously evaluate the interplay of different environment factors. Here, a combinatorial platform is developed with integrated microfluidic channels and nanofibers, associated with a method of high-content single-cell analysis, to study the effects of environmental factors on stem cell phenotype. Particular attention is paid to the dependence of hPSC short-term self-renewal on the density and composition of extracellular matrices and initial cell seeding densities. Thus, this combinatorial approach provides insights into the underlying chemical and physical mechanisms that govern stem cell fate decisions.

The single-chain antibody against 2-phenyloxazolone was modified with lipid molecules at its amino-terminus by genetic engineering. The engineered lipid-tagged antibody molecules were incorporated into liposomes consisting of phosphatidylcholine, and the immunoassay systems were constructed by the resulting immunoliposomes. One immunoassay system was based on fluoroimmunoassay. A competitive fluoroimmunoassay for caproic acid conjugate of 2-phenyloxazolone as a model antigen was performed with the calboxyfluoresceine-encapsulated immunoliposomes. Antigen could be determined in the concentration range from 10−7 to 10−9 M. The other system was based on quartz crystal microbalance (QCM). The immunoliposomes were competitively reacted with analyte to the hapten-immobilized surface of a crystal plate. The frequency change was observed by injection of the mixture of the immunoliposomes and analyte in a concentration dependent manner. In this competitive QCM assay, antigen could be measured in the concentration range from 10−5 to 10−8 M. Furthermore, direct observation of the immunoliposomes on the hapten-coated solid-surface by atomic force microscopy (AFM) was also performed in this study.

Mouse astroglial cells, which were cultured on an electrode, were found responsive to an electric stimulation of sine wave potential in enhancing hsp70 mRNA resulting from an activation of hsp70 gene expression. On the basis of this finding, electrically responsive cells were established by transfecting mouse 3T3-L1 cells with a constructed plasmid encoding hsp70 promoter and the firefly luciferase gene. A stable cell line has been established through selection of heat-stimulated luciferase expression. A 1-h electric stimulation of the cells resulted in activation of luciferase expression, which was confirmed to produce an increase in light emission. The sequential pattern of the electrically stimulated expression of luciferase was found different from that of the heat stimulation. Furthermore, the promoter was activated depending on the potential and duration of the stimulation applied. Consequently, the electric stimulation has proven effective on activating hspP70 promoter. This cell line is feasible in expressing the gene of interest by electrical stimulation, which lead us to construct environment responsive cells in general.

A novel tissue engineering for bone formation has been proposed, to make osteoblast differentiation balanced by transfecting the mesenchymal stem cells with a gene encoding human bone morphogenetic protein-2 (hBMP-2) under the control of adipocyte specific lipoprotein lipase (LPL) promoter. Due to the promoter specificity, the initiation of BMP transcription is dependent on adipogenesis. For 14-day culture in the presence of ascorbic acid (asc) and beta-glycerophosphate (gly), nontransfected mouse embryonic fibroblast C3H10T1/2 (10T1/2) cells showed extensive accumulation of lipid droplets and adipocyte specific enzyme glycerol-3-phosphate dehydrogenase (G3PDH) mRNA expression, but exhibited neither BMP-2 expression, high alkaline phosphatase (ALP) activity which reflects osteoblast phenotype. On the other hand, transfected 10T1/2 cells showed hBMP-2 expression, high ALP activity and low level of G3PDH. mRNA expression accompanied with minimal lipid droplets. These results indicate that 10T1/2 cells are proved to be differentiated with maintaining coordinated balance of adipogenesis and osteogenesis, when they are transfected by the gene encoding hBMP-2 under the control of LPL promoter.

The synthesis and the use of a new substrate, 4-hydroxy-naphthyl-1-phosphate (HNP), for the amperometric detection of alkaline phosphatase activity is described. The product of the enzymatic hydrolysis of HNP was dihydroxy naphthalene (DHN). DHN was rapidly oxidized in air to give naphthoquinone (NQ), which was measured in amperometric flow injection analysis (AFIA) at 300 mV versus Ag/AgCl. DHN standards could be measured at a 60 nM detection limit. There was a linear response to the enzyme with a 300 fM detection limit, which was equivalent to 6 attomole for each injection. The measurement range for human IgG, in an alkaline phosphatase amplified sandwich immunoassay with amperometric, was 1–1000 ng/ml.

The stability of immobilized mRNA against ribonucleases was investigated in a cell-free protein synthesis system. The plasmid-encoding protein A with the 20-mer poly(A) tail under the control of T7 promoter was constructed, and the corresponding mRNA was synthesized by T7 RNA polymerase reaction. The resulting mRNA was immobilized on oligo(dT)-immobilized latex beads by hybridization utilizing the poly(A) tail of mRNA at the 3'-terminus. The mRNA was stabilized against three types of nucleases (3'-OH exonuclease, 5'-OH exonuclease, and endonuclease) by immobilization. Translation of immobilized mRNA with a continuous-flow cell-free protein-synthesizing system from Saccharomyces cerevisiae was ascertained. Reusability of the immobilized mRNA as genetic information was also examined.

The design principle of a thermostable functional protein has been proposed by demonstrating genetic engineering synthesis of a thermostable cell adhesion protein. The cell adhesive peptide sequence, Arg-Gly-Asp (RGD), was incorporated into the elastin-based polyhexapeptide, whose repeating unit is Ala-Pro-Gly-Val-Gly-Val (APGVGV). The resulting protein possesses cell adhesion activity approximately 80% of fibronectin. After autoclaving at 120 °C for 20 min, the protein retained over 90% of cell adhesion activity, while the activity of autoclaved fibronectin decreased to 50%.

Morphological differentiation of PC12 cells cultured on an indium-tin oxide (ITO) electrode has been induced to grow neurites in the absence of nerve growth factor (NGF) by electrical stimulation. Rectangular pulse wave potentials were applied to the electrode at amplitudes of 200 mV and 400 mV with frequencies of 50 Hz, 500 Hz, and 1 kHz. The PC12 cells differentiated most prominently at 200 mV with 100 Hz. No statistically significant differences were observed among the electrically induced neurite lengths. The electrically induced differentiation was completely inhibited by a blockade of calcium influx using LaCl3. This indicates that repeated potential shift in the vicinity of a cellular membrane may stimulate morphological response, probably through calcium ion channels.

TOL plasmid in Pseudomonas putida mt-2 has a series of genes for the degradation of xylene, toluene, and their derivatives to pyruvate and acetaldehyde (or propionaldehyde). Two operons, i.e., upper operon and meta operon, play indispensable roles for the digestion of xylene derivatives: When XyIR protein recognizes xylene derivatives, another controlling gene, xyIS, is activated, which results in the activation of meta operon. Therefore, we have constructed a fusion gene between TOL plasmid and the firefly luciferase gene under the control of XyIR and the promoter of xyIS gene; i.e., by using fusions of the meta operon with promotorless luciferase expression vector from firefly, we have constructed and tested biomonitors for benzene derivatives. Bioluminescence specified by Escherichia coli (pTSN316), carrying xyIR and xyIS promoters, Ampr and luc, was measured in either a benzene derivative-saturated or o-methylbenzyl alcohol-dissolved medium both in the case of cell suspension and in the case of immobilized cell form. The utility of the biosensing system for monitoring in chemical plant drainage was demonstrated with samples supplemented with benzene derivatives. The xyIR-xyIS promoter-lux fusion carried by pTSN316 responded to a benzene-related chemical in sample solutions. Immobilization of the transformed E. coli, at one end of fiber optic, bearing firefly luciferase gene fused to TOL plasmid, has been demonstrated to fabricate a luminescent remote biomonitoring device for the protection of environmental deterioration. Due to the luminescent detection, the detection limits for benzene-related aromatics that are recognized by a binding protein (XyIR) were parts-per-million. We had already submitted a preliminary report concerning the possibility of environmental monitoring based on the above idea by using the transformed E. coli in a cell-suspended solution. This paper describes mainly a fiber-optic-based biomonitoring device for the protection of environmental deterioration.

Immunoliposomes were prepared by using biosynthetically lipid-tagged anti-2-phenyloxazolone single-chain antibody. Carboxyfluorescein as a fluorescent marker was encapsulated in the immunoliposomes. Some conditions for fluoroimmunoassay using the immunoliposomes were optimized by binding assays with hapten-coated microtiter wells. A competitive fluoroimmunoassay for the caproic acid conjugate of 2-phenyloxazolone as a model antigen was performed with the immunoliposomes. In the optimized assay conditions, antigen could be determined in the concentration range from 10-7 to 10-9 M.

A homogeneous immunoassay for α-fetoprotein (AFP) based on electrochemical luminescence is described. Luminol-labeled anti-AFP antibody was synthesized by coupling of diazoluminol with antibody. Homogeneous immunoassay for AFP was performed using the luminol-labeled anti-AFP antibody. A luminol-labeled antibody generated luminescence upon electrochemical oxidation and the luminescence markedly decreased in the presence of antigen, because the bound antigen inhibited the electrode reaction. A standard curve indicated that the lower limit of AFP determination should be 10 −11 g ml −1 in the time required for 5 min. The immunoassay for AFP in human control serum was also studied.

p-Aminophenyl-β-D-galactopyranoside (PAPG) was shown to be a suitable substrate for the amperometric detection of galactosidase activity at neutral pH. The application of this amplification system for immunoassay was demonstrated. The product of the enzyme reaction, p-aminophenol (PAP), was detected at 200 mV, vs. Ag/AgCl, by flow-injection analysis (FIA), with a 50 nM detection limit. PAPG was hydrolyzed more than 2.5 times faster than p-nitrophenyl-β-D-galactopyranoside, by the enzyme. Both PAP and PAPG were stable at pH 7. The galactosidase concentration could be measured down to a concentration of 100 fM, and mouse IgG could be assayed by sandwich immunoassay down to 700 fM. PAPG was found to be a promising reagent for heterogeneous systems, like the one described, and for homogenous assays of biological fluids.

Sensitive and convenient biosensing of environmental pollutants has been developed by fusing a gene of firefly luciferase to the TOL plasmid. TOL plasmid of Pseudomonas putida encodes a series of enzymes for degradation of benzene and its derivatives. The expression of these enzymes is controlled with the regulating proteins xylR and xylS, whose promoters are activated in the presence of aromatic compounds. The structural gene of firefly luciferase, as a reporter enzyme, was inserted under the control of the promoter of xylS protein, and gene fusion plasmid pTSN316 was constructed. The recombinant Escherichia coli transformed with this plasmid was applied to the environmental biosensing of benzene derivatives. The expression of luciferase was induced in the presence of aromatic compounds and the lower detection limit for m-xylene was 5 microM.

We conducted cell-based cytotoxicity screening of a 101-membered α-helical peptide library using cell fingerprints (CFPs). The CFP data suggested that there is a relationship between cytotoxicity and peptide characteristics, such as hydrophobicity, charge, and amino acid composition. In spite of the small size of the library used in this study, several peptides demonstrated cell-specific toxicity. The strategy of combining a designed peptide library with CFP thus shows real promise for peptide-based screening with cells.

We developed an electrochemical detection method for evaluating cellular physiological status based on the stringent response as a means to monitor cell viability. A reporter plasmid was constructed by inserting the beta-galactosidase gene (lacZ) under the control of the rpoS promoter, and then used to transform E. coli cells. Electrochemical responses from the products catalyzed by beta-galactosidase expressed by these E. coli cells were detected using the chronoamperometric technique in a nondestructive manner. Comparisons of response currents between the relA-positive strain and relA-negative strain revealed that increases in these currents were caused by the stringent response due to the stressful alcoholic environment, and thus as a model of stressful cultivating conditions. The current was proportional to the beta-galactosidase activity assayed by a conventional method that required the destruction of cells. The cellular physiological status, which depends on the stringent response as a viability marker, therefore, could then be evaluated online with a current using the rpoS-lacZ reporter gene in the relA-positive strain without pretreatment.

We have used outer cell potential measurement to record agonist-dependent cellular responses in cells engineered to express ligand-gated ion channels and grown on a microelectrode surface. Application of glutamate, a natural agonist, induced a complex and robust potentiometric response in cells expressing homomeric GluR-D glutamate receptor, but not in nonexpressing control cells. The response consisted of an initial decrease in outer potential followed by a transient increase and was not obtained for other amino acids devoid of agonist activity at glutamate receptors. Furthermore, the pharmacological agonist of the GluR-D receptor, kainate, also produced the potentiometric response whereas 6-cyano-7-nitroquinoxaline-2,3-dione, a competitive antagonist, was not active in itself but attenuated the responses to glutamate. The time course of the measured changes was slow, which may be partially due to the ligand being applied by free diffusion but may also reflect a contribution by secondary changes in the behavior of the cells. This novel approach should be applicable to other ligand-gated ion channels and holds promise as a cell-based biosensor for high-throughput drug screening and other applications.

Bone marrow stromal stem cells were cultured on the potential-controlled electrode surface. Dexamethasone-induced osteogenic differentiation was profoundly enhanced by a constant potential of electrical stimulation at +0.3 V vs. Ag/AgCl.

Cell differentiation of PC12 cells was electrically induced to grow neurites in the absence of nerve growth factor (NGF) on the electrode surface, of which potential was modulated by a rectangular wave of potential. The electric stimulation induced the c-fos expression which is essential for cell differentiation. Non-specific calcium channel blocker, lanthanum ion, inhibited the electrically induced differentiation, while NGF-induced differentiation was not suppressed. An L-type calcium channel blocker, nifedipine, also inhibited the electrically induced calcium influx and c-fos expression. Moreover, a stretch-activated (SA) channel blocker, gadolinium ion, inhibited the electrically stimulated differentiation by blocking the calcium influx, but gave no prominent effects on the potassium ion-induced differentiation. Chelerythrine, a specific protein kinase C (PKC) inhibitor, almost inhibited the cell differentiation by the electric stimulation but not by the NGF treatment. These results indicate that the alternative potential may stimulate cell differentiation through a PKC cascade.

A controlled culture system has been developed to induce nerve growth factor (NGF) production in astroglial cells that are cultured on an electrode surface. The electrode potential is alternatively modulated at an amplitude of 300 mV and a frequency of 10 Hz. The electric stimulation triggers NGF production and secretion. The mechanism of the electrically induced NGF production is discussed in association with protein kinase C (PKC) activation.

An increasing attention has arisen in designing a continuous flow bioreactor which incorporate hybridoma cells in immobilized form. An immobilized cell type of bioreactor has several advantages over a suspended cell type of bioreactor, which includes a superior controllability and efficiency. Several trials have been made in line with the development of an immobilized hybridoma bioreactor for producing monoclonal antibodies, although few significant results have been accomplished.

Protein A and firefly luciferase were genetically fused and the resulting fusion protein was applied to a bioluminescent immunoassay. The gene fusion plasmid, pMALU2, was constructed by inserting the structural gene of luciferase into a protein A expression vector, and was expressed in Escherichia coli. The resulting fusion protein of molecular weight 91 kDa retained not only the enzymatic activity of luciferase but also the binding capability of protein A to the Fc region of immunoglobulin G (IgG). The bioluminescent immunoassay was performed with the fusion protein and human IgG was determined in the concentration range from 10(-3) to 10(-7) g/ml.

Several types of cellular biosensors have been developed for assessing chemicals, in which the cell responses to chemicals are transduced to the sensor outputs in various manners. The cell layer is fixed in the vicinity of the signal transducer. As an example, assessment of immunomodulating chemicals has been performed with a cellular biosensor based on electrochemical determination of the inducible nitrogen oxide synthase (iNOS) expression in a macrophage-like cell.