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Bioremediation uses the degradation abilities of microorganisms and other organisms to remove harmful pollutants that pollute the natural environment, helping return it to a natural state that is free of harmful substances. Organism-derived enzymes can degrade and eliminate a variety of pollutants and transform them into non-toxic forms; as such, they are expected to be used in bioremediation. However, since enzymes are proteins, the low operational stability and catalytic efficiency of free enzyme-based degradation systems need improvement. Enzyme immobilization methods are often used to overcome these challenges. Several enzyme immobilization methods have been applied to improve operational stability and reduce remediation costs. Herein, we review recent advancements in immobilized enzymes for bioremediation and summarize the methods for preparing immobilized enzymes for use as catalysts and in pollutant degradation systems. Additionally, the advantages, limitations, and future perspectives of immobilized enzymes in bioremediation are discussed.

Introduction: With the advent of effective systemic therapy, transarterial chemoembolization (TACE) is established as a highly effective locoregional treatment modality for carefully selected patients with hepatocellular carcinoma (HCC). This randomized controlled trial was conducted to clarify whether selective TACE with drug-eluting beads (DEB-TACE) loaded with epirubicin or selective conventional TACE (cTACE) with epirubicin-ethiodized oil might be more effective for obtaining complete response(CR) in patients with HCC. Methods: Between March 2016 and May 2019, Child-Pugh class A or B patients with unresectable HCC who were scheduled to receive selective TACE were randomly assigned at a 1:1 ratio to the DEB-TACE arm or the cTACE arm. The primary endpoint was the CR rate at 3 months, as evaluated according to the modified Response Evaluation Criteria in Solid Tumors by an independent review committee, and the secondary endpoints were the CR rate at 1 month and incidences of adverse events. Results: A total of 200 patients (DEB-TACE, 99 patients; cTACE, 101 patients) were enrolled in the study. The CR rates at 3 months and 1 month were significantly higher in the cTACE arm (75.2%, 84.2%) as compared with the DEB-TACE arm (27.6%, 35.7%). However, the frequencies of adverse events of any grade, including pyrexia (DEB-TACE vs. cTACE, 19.4% vs. 45.5%, p = 0.0001), fatigue (5.1% vs. 15.8%, p = 0.0194), malaise (11.1% vs. 25.7%, p = 0.0103), appetite loss (12.1% vs. 28.7%, p = 0.0048), abdominal pain (12.1% vs. 23.8%, p = 0.0423), increased serum bilirubin (22.2% vs. 48.5%, p = 0.0002), hypoalbuminemia (43.4% vs. 60.3%, p = 0.0154), increased serum aspartate aminotransferase (35.7% vs. 81.2%, p < 0.0001), and increased serum alanine aminotransferase (35.7% vs. 77.2%, p < 0.0001), were also significantly higher in the cTACE arm than in the DEB-TACE arm. Conclusions: Selective cTACE appeared to have higher CR rates for local tumor control as compared to selective DEB-TACE for HCC. However, the frequency of postembolization syndrome was also significantly higher in the cTACE group than in the DEB-TACE group. Thus, to achieve CR, cTACE may be selected over DEB-TACE in patients who can be expected to tolerate postembolization syndrome.

Abstract Background Liver cirrhosis occurs in approximately 80–90% of patients with hepatocellular carcinoma (HCC), and hepatic resection may be dangerous because of well-documented liver cirrhosis, which may be accompanied by portal hypertension (PH). Here we report a patient with advanced HCC with gastric varices and PH who experienced a good clinical course after undergoing balloon-occluded retrograde transvenous obliteration (BRTO), percutaneous transhepatic portal vein embolization (PTPE), hand-assisted laparoscopic (HALS) splenectomy, and right lobectomy of the liver. Case presentation A 72-year-old man had two HCCs with gastric varices. CT revealed one tumor (4.5 cm) located in segment 7, involving the right hepatic vein, adjacent to the middle hepatic vein. Another tumor (2.7 cm) was located in segment 6. He first underwent BRTO for gastric varices and PTPE for planned right lobectomy of the liver. To reduce PH, HALS splenectomy was performed, and uncomplicated right lobectomy of the liver was performed 10 weeks after the first visit. He has remained free of recurrence for at least 1 year. Conclusions Our patient underwent uncomplicated BRTO, PTPE, HALS splenectomy, and right lobectomy of the liver for advanced HCC with PH. Controlling portal pressure is important when hepatic resection is required to treat HCC with PH.

We report the case of a bowel injury, which occurred after the percutaneous cryoablation (PCA) of large renal cell carcinoma (RCC). A 50-year-old man with RCC measuring 47 mm in diameter. First, we performed transarterial embolization for the tumor, followed by PCA with hydrodissection, which displaced the small intestine from the iceball. The procedure was completed without any complication on the procedural day; however, the patient complained of appetite loss and abdominal pain 2 days after PCA. Computed tomography revealed a bowel injury at the small intestine adjacent to the tumor. After 7 days, ileus tube insertion, and fasting, the patient recovered from the bowel injury and was discharged 10 days after PCA. He underwent a second PCA because of a small recurrent renal tumor 5 months after the first PCA without complications. This case indicated that a bowel injury after PCA for RCC could be treated conservatively. Keywords: Cryoablation, Renal cell carcinoma, Bowel injury, CT guided

Abstract Background We compared clinical outcomes of carbon ion radiotherapy and transarterial chemoembolization in the treatment of hepatocellular carcinoma. Methods Data of 477 patients with hepatocellular carcinoma who had undergone carbon ion radiotherapy or transarterial chemoembolization between April 2007 and September 2016 were retrospectively reviewed. Treatment naïve patients with single HCC, who underwent carbon ion radiotherapy or transarterial chemoembolization as a primary treatment were included. Clinical outcomes of the treatments were compared after utilizing propensity score matching. Results Of 124 patients who received carbon ion radiotherapy and 353 patients who received transarterial chemoembolization, 31 and 23 patients met our inclusion criteria, respectively. After utilizing propensity score matching, 17 matched pairs of patients from each treatment group were analyzed. The median follow-up durations after carbon ion radiotherapy and transarterial chemoembolization were 43 and 32 months, respectively. The 3-year overall survival, local control, and progression-free survival rates in the carbon ion radiotherapy versus transarterial chemoembolization groups were 88% versus 58% (p

In this study, the microreactor system was investigated and compared with the batch-wise system as rapid and effective extractive Pb(II) separation over Fe(III), Cu(II) and Zn(II) with tetraacetic acid calix[4]arene. By using a microreactor system, the Pb(II) extraction percentages reached the maximum of 73, 89 and 100% in 8 sec residence time at equilibrium pH of 2.00, 2.25 and 2.50, respectively. The stripping percentage was 92% at 8 sec residence time by using a microreactor system with 2.0 M HNO3 as a stripping reagent. Complete separation of Pb(II) over Fe(III), Cu(II) and Zn(II) ions with the tetraacetic acid calix[4]arene in a competitive metal system was achieved at pH 2.00. However, the batch system required 24 h to reach the equilibrium for both extraction and stripping processes. The results suggested that the microreactor system enhanced the Pb(II) extraction and stripping rate up to 104 times faster than the batch-wise system.

Abstract Background Pleomorphic leiomyosarcomas (PLMSs) are extremely rare tumors. We present the first case of hepatic primary PLMS after surgery for gastric gastrointestinal stromal tumor (GIST). Case presentation The patient was a 62-year-old man who was referred to our hospital for resection of a hepatic tumor arising after gastric GIST surgery that was resistant to imatinib and sunitinib. A 40-mm tumor in the left lobe of the liver and three small nodules in the right lobe were detected. We performed hepatic left lobectomy and partial resections for three lesions. According to the histopathological and immunohistochemical findings and c-kit gene mutations analysis, the main tumor was diagnosed as a PLMS. Conclusion It is necessary to consider the possibility that imatinib-resistant GIST recurrence lesions are a different kind of soft-tissue sarcoma. Accurate diagnosis is required to not miss the opportunity for radical excision of PLMS.

Tyrosine kinase inhibitors (TKIs) induce autophagy in many types of cancer cells. We previously reported that gefitinib (GEF) and imatinib (IMA) induce autophagy in epidermal growth factor receptor (EGFR) knock-out A549 and non-BCR-ABL-expressing leukemia cell lines, respectively. This evidence suggests that TKI-induced autophagy is independent of the original target molecules. The present study compared the autophagy-inducing abilities of various TKIs, regardless of their targets, by quantitative autophagy flux assay. We established stable clones expressing the GFP-LC3-mCherry-LC3ΔG plasmid in A549, PC-9, and CAL 27 cell lines and assessed autophagy inducibility by monitoring the fluorescent ratios of GFP-LC3 to mCherry-LC3ΔG using an IncuCyte live cell imaging system during exposure to TKIs viz; GEF, osimertinib (OSI), lapatinib (LAP), lenvatinib (LEN), sorafenib (SOR), IMA, dasatinib (DAS), and tivantinib (TIV). Among these TKIs, DAS, GEF, and SOR exhibited prominent autophagy induction in A549 and PC-9 cells. In CAL 27 cells, IMA, SOR, and LEN, but not GEF, TIV, or OSI, exhibited autophagy induction. In the presence of azithromycin (AZM), which showed an inhibitory effect on autophagy flux, TKIs with prominent autophagy inducibility exhibited enhanced cytotoxicity via non-apoptotic cell death relative to effects of TKI alone. Therefore, autophagy inducibility of TKIs differed in the context of cancer cells. However, once induced, they appeared to have cytoprotective functions. Thus, blocking TKI-induced autophagy with AZM may improve the therapeutic effect of TKIs in cancer cells.

Hepatic epithelioid hemangioendothelioma (HEHE) is a rare tumor. Preoperative diagnosis of HEHE is difficult because it does not manifest specific symptoms or tumor markers. We report a resected case of small and solitary HEHE. The patient, a 74-year-old man, had undergone surgical resection for left renal cell carcinoma 20 years ago. During follow-up, a tumor approximately 1.3 cm in diameter was detected by computed tomography (CT) at liver segment VIII. It showed isodensity in the arterial phase, low density in the portal venous phase, and homogeneous enhancement in the late phase on CT and magnetic resonance imaging (MRI). We performed hepatic resection of the right hepatic vein drainage area. A pathological diagnosis of HEHE was made. Although small and solitary HEHE is rare, an enhancement pattern in each phase on CT and MRI, using contrast media, can yield clues for the diagnosis of HEHE.

Abstract Background Bile leakage after hepatectomy still causes relatively serious problems, and some types of bile leakage are intractable. Case presentation We report a case of postoperative isolated bile duct leakage managed successfully by combination therapy of percutaneous transhepatic portal vein embolization (PTPE) and bile duct ablation with ethanol. A 61-year-old man diagnosed with hepatocellular carcinoma underwent partial hepatectomy. On postoperative day 1, bile leakage was detected at the drainage tube. Simple drainage treatment did not improve the situation. He was diagnosed with isolated bile leakage based on fistulogram from the drainage tube that showed the bile duct at segments V and VIII but not the common bile duct. A volume of drainage fluid of 200 mL/day was observed. Combination therapy with PTPE and bile duct ablation with ethanol was planned. After the percutaneous transhepatic cholangiography, the drainage tube was inserted into the bile duct, and PTPE was performed to segments V and VIII. The amount of drainage fluid decreased, and bile duct ablation with ethanol was performed to the isolated bile duct. No complication was found following combination therapy. Conclusion In this case, we successfully treated a patient with isolated bile leakage by combination therapy with PTPE and bile duct ablation.

Lithium extraction remains a challenge in the hydrometallurgy process due to its economic value and maldistribution sources. Employing calix[4]arene derivatives in solvent extraction techniques results in high selectivity and extraction capability, but a slow extraction rate. The slow kinetics of batch-wise extraction can be drastically accelerated by using a T-type microreactor system. Therefore, a combination of calix[4]arene and a microreactor system serves as an ideal platform for efficient lithium extraction. In this work, the fluid dynamics of lithium extraction using a monoacetic acid calix[4]arene derivative in a T-type microreactor system were studied. Increasing the O/A ratio increases the average length, surface area, and volume of the organic droplets, but decreases the specific surface area. In contrast, increasing the Reynolds number decreases the average length, surface area, and volume of the organic droplets, but increases the specific surface area. It was found that shorter diffusion distance, larger specific surface area, and faster vortex velocity were the factors that play the most pivotal roles in achieving great extraction rate enhancement in T-type microreactor systems compared to batch-wise systems. These findings represent an important new concept in the study of the fluid dynamics of lithium extraction using monoacetic acid calix[4]arene derivatives in T-type microreactor systems.

In livestock production, point-of-care testing (POCT) technology that enables easy on-site analysis of sex hormones is desired to improve reproductive efficiency. In this context, low-molecular-weight endogenous steroids are particularly important for perinatal management. Therefore, we attempted to use a simple method that combines electrochemical techniques with immunochromatography to measure estrone-3-sulfate (E1S), one of the low-molecular-weight endogenous steroids that is an estrogen ester. The limit of detection (LOD) for E1S achieved by electrochemical immunochromatography was 570.5 ng/mL, which was one to two orders of magnitude lower than that of small molecule compounds analyzed by other POCT techniques (Primpray et al., Anal. Chim. Acta, 2019). In addition, it was indicated by a colorimetric analysis that the sensitivity of the electrochemical immunochromatographic technique could be enhanced by improving the method of application of the antibodies on the nitrocellulose membrane and the contact between the electrochemical detector and the nitrocellulose membrane.

Biologically active proteins are useful for studying the biological functions of genes and for the development of therapeutic drugs and biomaterials in a biotechnology industry. Overexpression of recombinant proteins in bacteria, such as Escherichia coli, often results in the formation of inclusion bodies, which are protein aggregates with non-native conformations. As inclusion bodies contain relatively pure and intact proteins, protein refolding is an important process to obtain active recombinant proteins from inclusion bodies. However, conventional refolding methods, such as dialysis and dilution, are time consuming and, often, recovered yields of active proteins are low, and a trial-and-error process is required to achieve success. Recently, several approaches have been reported to refold these aggregated proteins into an active form. The strategies largely aim at reducing protein aggregation during the refolding procedure. This review focuses on protein refolding techniques using chemical additives and laminar flow in microfluidic chips for the efficient recovery of active proteins from inclusion bodies.

Microreaction technology, which is an interdisciplinary science and engineering area, has been the focus of different fields of research in the past few years. Several microreactors have been developed. Enzymes are a type of catalyst, which are useful in the production of substance in an environmentally friendly way, and they also have high potential for analytical applications. However, not many enzymatic processes have been commercialized, because of problems in stability of the enzymes, cost, and efficiency of the reactions. Thus, there have been demands for innovation in process engineering, particularly for enzymatic reactions, and microreaction devices represent important tools for the development of enzyme processes. In this review, we summarize the recent advances of microchannel reaction technologies especially for enzyme immobilized microreactors. We discuss the manufacturing process of microreaction devices and the advantages of microreactors compared to conventional reaction devices. Fundamental techniques for enzyme immobilized microreactors and important applications of this multidisciplinary technology are also included in our topics.

Enzymes are biocatalysts. They are useful in environmentally friendly production processes and have high potential for industrial applications. However, because of problems with operational stability, cost, and catalytic efficiency, many enzymatic processes have limited applications. The use of cross-linked enzyme aggregates (CLEAs) has been introduced as an effective carrier-free immobilization method. This immobilization method is attractive because it is simple and robust, and unpurified enzymes can be used. Coimmobilization of different enzymes can be achieved. CLEAs generally show high catalytic activities, good storage and operational stabilities, and good reusability. In this review, we summarize techniques for the preparation of CLEAs for use as biocatalysts. Some important applications of these techniques in chemical synthesis and environmental applications are also included. CLEAs provide feasible and efficient techniques for improving the properties of immobilized enzymes for use in industrial applications.

Content analysis proves to be very useful in inferring the intention among competing firms. Content analysis is the systematic and replicable examination of symbols of communication. Like individuals, firms render messages outside of themselves. Their daily activities are, so to speak, communications process. Therefore researchers are able to apply content analysis to the exploration of firms’ behavior. This paper will take up, as one of these cases, new products news releases made by inkjet printer makers. Through the analysis, the product concept trajectory is developed. These depicted trajectories show us the intention of competing firms.

The aim of this study was to evaluate the accuracy, safety, and role of splenic biopsy in the management of patients with non-mass-forming isolated splenomegaly and suspected malignant lymphoma.Between 2001 and 2013, 137 biopsies were performed under computed tomography (CT) fluoroscopic guidance in 39 patients. All patients had splenomegaly based on the CT findings and a suspected diagnosis of malignant lymphoma based on their clinical symptoms. The spleen was the only accessible site to perform a biopsy, and no mass lesions could be identified in the spleen.The overall sensitivity, specificity, and diagnostic accuracy of image-guided biopsy for malignant lymphoma were 88%, 100% and 92%, respectively. Major complications occurred in 3 patients. In 1 patient, transcatheter arterial embolization was performed due to hemorrhage, and two patients needed blood transfusion because of hematoma development, without the need for further treatment.Image-guided splenic core-needle biopsy is a safe and accurate technique with a high diagnostic accuracy in most patients who with non-mass-forming isolated splenomegaly and suspected underlying malignant lymphoma.

We conducted electrochemical immunochromatography using a developed electrochemical immunochromatography platform. We used immunoglobulin G (IgG) as a representative protein. We also conducted enzyme-linked immunosorbent assay (ELISA) as a control test. We used the same reagents except for the substrate and compared their limits of detection (LODs) and detection ranges. We succeeded in measuring IgG concentrations ranging from 30 ng/ml to 10 μg/ml and obtained 23.00 ng/ml as the LOD for electrochemical immunochromatography. The detection signal was not saturated even at 10 μg/ml, so it seems that higher concentrations of IgG can also be measured. The LOD was approximately 80-fold higher than that of ELISA (0.30 ng/ml); however, the detection range was one order of magnitude higher than that of ELISA. While electrochemical immunochromatography is less sensitive than ELISA, we demonstrated sufficient sensitivity for its use in a point-of-care testing (POCT) device. Furthermore, this information will be very helpful when introducing an assay system already established in ELISA to POCT. [ABSTRACT FROM AUTHOR]

The number of patients suffering from osteoporosis increases year by year. Osteoporosis is characterized by decreased bone strength and increases the risk of fracture. The femoral neck is the most possible part of the fracture. In this study, bone strength, particularly the femoral neck bone, of ovariectomized osteopenia (OVX) model mouse was measured using a newly improved stage device for femoral neck fracture. Female ICR mice were divided into the Sham and OVX groups. Eight weeks after surgery, right and left femurs were taken out. The right femur neck was set on an improved bone strength measurement device and the maximum breaking load (NT) was measured. Moreover, the left femur was measured for bone mineral density (BMD) using a CT. All results were regression analyzed with Stat View analysis software and their correlation was analyzed. As for the right femur, N value of the OVX group showed a significant decrease compared to that of the Sham group. As for the left femur, value of cancellous BMD of OVX group was also lower. Therefore, we examined the correlation between the BMD and bone strength of the Sham and OVX, respectively, and obtained a significant positive correlation. Moreover, when the correlation with stiffness and bone strength was also investigated as a parameter index of bone quality, significant positive correlation was found. The present study indicates that the novel strength measurement equipment of the femoral neck is useful for an evaluation of osteopenic model animals, for instance of OVX model mice. [ABSTRACT FROM AUTHOR]

We have studied the construction of an electrochemical immunochromatography platform as one of the point-of-care testing devices from both experimental and theoretical aspects. In the electrochemical immunochromatography measurement, the layout of working, reference, and counter electrodes and the flow rate in a porous membrane are important in obtaining a highly sensitive and stable electrochemical signal. In this manuscript, we report the effects of the layout of the three electrodes and the elapsed time after sample injection on electrochemical signals. We found that the working electrode should be placed upstream of the reference electrode because an unfavorable electrochemical signal from a Ag+ ion from the reference electrode was observed on the working electrode when it was located downstream of the reference electrode. Furthermore, we found that the electrochemical signal was inversely proportional to the sixth root of time. Experimental and theoretical results are consistent with each other, exhibiting a high correlation coefficient of 0.99. [ABSTRACT FROM AUTHOR]

Introduction Anaplastic transformation of well-differentiated papillary thyroid carcinoma at distant metastasis sites is rare. To the best of our knowledge, this is the first report of an autopsy case of anaplastic transformation of papillary thyroid carcinoma in multiple lung metastases presenting with a malignant pleural effusion. Case presentation We report an autopsy case of a 61-year-old Japanese man with anaplastic transformation of papillary thyroid carcinoma with multiple lung metastases presenting with a malignant pleural effusion, which was difficult to diagnose by cytological examination before the autopsy. He presented with a 1-month history of progressive dyspnea, and examination of the left pleural effusion revealed a bloody exudate with an increase in thyroglobulin; however, malignant cells in the pleural fluid were negative for thyroglobulin. Conclusion It is important to be aware that anaplastic transformation of differentiated thyroid carcinoma could develop in lung metastases and could be a cause of a malignant pleural effusion. [ABSTRACT FROM AUTHOR]

Complementary surfaces are buried when peptide hormones, growth factors, or cytokines bind and activate cellular receptors. Although these extended surfaces provide high affinity and specificity to the interactions, they also present great challenges to the design of small molecules that might either mimic or antagonize the process. We show that the insulin receptor (IR) and downstream signals can be activated by targeting a site outside of its ligand-binding domain. A 24-residue peptide having the IR transmembrane (TM) domain sequence activates IR, but not related growth factor receptors, through specific interactions with the receptor TM domain. Like insulin-dependent activation, IR-TM requires that IR have a competent ATP-binding site and kinase activation loop. IR-TM also activates mutated receptors from patients with severe insulin resistance, which do not respond to insulin. These results show that IR can be activated through a pathway that bypasses its canonical ligand-binding domain. [ABSTRACT FROM AUTHOR]

Direct fluorination of 1,3-dicarbonyl compounds including 1,3-diketones, 3-oxo esters, and 3-oxoamides was conducted using aqueous hydrofluoric acid with the aid of iodosylarenes, giving the corresponding 2-fluorinated products in good to high yields. Among the used iodosylarenes, o-iodosyltoluene was found to be the most effective, and the yield of 2-fluorinated products was improved. [ABSTRACT FROM AUTHOR]

Background: Real-time virtual sonography (RVS) is a diagnostic imaging support system that can synchronize with ultrasound images in conjunction with computed tomography or magnetic resonance images using magnetic navigation system. RVS has been applied in clinical practice to perform such procedures as radiofrequency ablation and biopsy; however, the application of RVS for percutaneous transhepatic biliary drainage (PTBD) is rare. Methods: Between 2007 and 2012, RVS-assisted PTBD was performed for 30 patients (19 males and 11 females; age range, 41 to 89 years; mean age, 66.9 years) with obstructive jaundice. The targeted bile duct was determined using the RVS system before the procedure. The intervention was considered to be successful when the targeted bile duct was punctured and the drainage catheter was placed in the bile duct. Complications were evaluated according to the Society of Interventional Radiology Clinical Practice Guidelines. Results: A total of 37 interventions were performed for 30 patients. The interventions were successful in 35 (95%) of 37 interventions. The targeted bile ducts were: B3 (n = 24), B5 (n = 7), B8 (n = 3), B6 (n = 1), and the anterior (n = 1) and posterior (n = 1) branches of the right bile duct. The mean targeted bile duct diameter was 4.9 mm (1.9 to 8.2 mm). PTBD was able to be accomplished in all patients because the non-targeted bile ducts were successfully punctured alternatively. No major complications were observed in relation to the interventional procedure. Conclusions: RVS-assisted PTBD is a feasible and safe procedure. Accurate puncture of targeted bile ducts can be achieved using this method. [ABSTRACT FROM AUTHOR]

This paper describes kinetic parameters of an enzymatic reaction obtained by measuring the reaction rates of hydrolysis by trypsin at various flow rates and temperatures. Using these parameters, the mechanisms of an efficient reaction of nonimmobilized, i.e., “free state” enzyme in microchannel laminar flow can be examined from a kinetic perspective. Efficient complex formation between the enzyme and substrate was confirmed through Michaelis−Menten analysis. Results show that the enhancing effect of microfluidics in complex formation accelerated the enzymatic reaction. Results of activation energy analysis confirmed that a decrease in the apparent activation energy occurred as the flow rate increased. Taken together, these results suggest that a microfluidic system is useful for performing rapid reactions by influencing the complex formation and activation energy. [ABSTRACT FROM AUTHOR]

This paper presents the capability of changing the activation energy of chemical reactions using microchannel laminar flow. Kinetic parameters of the duplex–coil equilibrium of DNA oligomers were studied by measuring the hysteresis between denaturation–renaturation curves using an in-house temperature-controllable microchannel-type flow cell. For this study, DNA oligomers were used because they allow physicochemical analysis and theoretical discussion. Kinetic parameters of the duplex–coil equilibrium of DNA oligomers were obtained by measuring the denaturation–renaturation hysteresis curves. Both cooling and heating curves were shifted to the high-temperature side at higher flow rates. The renaturation reaction was influenced by a slower flow rate. The effect of the slower flow rate was more pronounced for renaturation than denaturation reactions. The magnitude of the activation energies of association decreased as the flow rate increased, but that of the activation energies of the dissociation increased as the flow rate increased. Overall, these results suggest that chemical reactions' change of activation energy depends on the flow rate and the DNA molecular size. [ABSTRACT FROM AUTHOR]

This paper reports the shift in thermal stability of DNA duplex and its thermodynamics spectroscopically, caused by stretching and orientation of DNA strands in a microchannel laminar flow. For direct spectroscopic measurement of the microchannel, we prepared an in-house temperature-controllable microchannel-type flow cell. The melting curves of DNA oligomers in a microchannel laminar flow were measured. For DNA oligomers with more than 10 base pairs, the melting curve shifted to the high-temperature side with higher flow speed. However, for 8-base-pair DNA oligomers, a change in the melting profile was not observed in batchwise and microchannel flows. We undertook microfluidic thermodynamic analysis to elucidate details of the shift in thermal stability of the DNA duplex in a microchannel laminar flow. Enthalpy−entropy compensation is applicable to the microfluidic thermal stability shift. We studied the relationships between the enthalpy−entropy compensation and DNA strand length or flow speed. Results showed that the enthalpy−entropy compensation was influenced by both DNA strand length and flow speed, and the penalties of enthalpy were 2−12% greater than the benefits of entropy. [ABSTRACT FROM AUTHOR]

We developed a novel microreaction system for optical resolution of racemic amino acids. This device, which is based on a continuous microfluidic system, consists of an enzyme-immobilized microreactor and a microextractor. Use of the enzyme-microreactor, which was prepared by membrane formation on the microchannel surface, enabled a highly enantioselective reaction for a racemic amino acid derivative. The microextractor provided a laminar flow of two immiscible solutions, which enabled selective extraction of the product. Using this integrated device, we could perform efficient continuous production of optically pure unnatural amino acids. [ABSTRACT FROM AUTHOR]

Laminar flow which is formed in a microchannel generally provides specific microfluidic characteristics and is applied to a variety of uses such as micro-biochemical analysis, handling of biological objects and micromixing. Influence of gravity on the laminar flow behaviour has not been much investigated because its influence has been considered to be very small due to the largeness of surface effects. In this work, a quantitative investigation into gravity influence on horizontal two-layer laminar flow was carried out using computational fluid dynamics simulation. Results showed the possibility of representing horizontal two-layer laminar flow behaviour by a dimensionless parameter which is a function of density difference, viscosity, microchannel size and velocity, under the condition that the microchannel cross section is square, and interfacial tension and diffusion are negligible. The dimensionless parameter becomes important especially for microfluidics where laminar flow can be formed easily. This simple parameter enables a rough estimation of the horizontal two-layer laminar flow behaviour. The results in this work are useful for microdevice design, biochemical analysis, mixing and chemical reaction. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue on topics including bioelectronics, biosensors, and biomedical devices.