Enhanced viscoelastic focusing of particle in microchannel.

A novel method is reported to enhance the focusing of microparticle in the viscoelastic fluid. Gradually contracted geometry is designed in microchannel, which changes the distribution of the elastic lift force on the cross section. Additionally, it induces the viscous drag force and the Saffman lift force in the lateral direction. Under the combined effect of these forces, microparticles fast migrate to the center of the channel. In comparison to the channel with constant cross section, the present channel significantly enhances the particle's lateral migration, leading to efficient viscoelastic particle focusing in a short channel length. The influence of flow rate, channel length, particle size and fluid property on the particle focusing is also investigated. With simple structure, small footprint and perfect particle focusing performance, the present device has great potential in the particle focusing processes in various lab-on-a-chip applications.

A target-triggered biosensing platform for detection of HBV DNA based on DNA walker and CHA.

Hepatitis B virus (HBV), one of the causative agents of viral hepatitis, may lead to chronic hepatitis, cirrhosis, and liver cancer. In this work, we designed a sensitive and modular biosensing platform for detecting HBV DNA based on a DNA walker that hangs on to surfaces and a catalyst-triggered catalyzed hairpin assembly (CHA). In the presence of HBV DNA, strand displacement reaction between target and double-stranded complex caused the release of walker strand to trigger the DNA walker. Then, a catalyst was free to open the trapped hairpins to form a new double-strand complex, driving the CHA reaction. Thus, a powerful cascade amplification reaction realized in DNA walker and CHA based on toehold-mediated strand displacement reaction in this system. To achieve quantitative detection of HBV DNA, a fluorescent-quencher signaling pair was employed, the turn-on fluorescence provided an analytical signal. A wide detection range from 0.5 nM to 50 nM with a detection limit as low as 0.20 nM was reached on the condition of acceptable specificity and reproducibility. We could also further apply it to multiple different bioanalysis by changing adjustable elements. This reported biosensor opened a new avenue for sensitivity and modularity of DNA detection.

Combined spinal-epidural anesthesia with hypobaric ropivacaine in sitting position significantly increases the incidence of hypotension in parturients undergoing cesarean section.

AIM: Maternal position during induction of combined spinal-epidural anesthesia (CSEA) may affect hemodynamics and block characteristics. This study aimed to assess whether the sitting position is more likely to induce hypotension and higher block level than the lateral position in CSEA with hypobaric ropivacaine. METHODS: Ninety American Society of Anesthesiologists physical status I and II parturients undergoing elective cesarean section were randomized into three groups: the sitting, left-lateral, and right-lateral position groups. The L3-4 interspace was selected as the puncture site, and subarachnoid injection of 2.5 mL 0.5% hypobaric ropivacaine was administered. After the epidural catheter was inserted and fixed, the patient's position was changed to the left-leaning supine position. The blood pressure was measured once every 1 min followed by once every 3 min after the delivery. The sensory block level was regularly measured. RESULTS: A total of 88 parturients were included in this study. The incidences of hypotension in the sitting, left-lateral, and right-lateral position groups were 72%, 38%, and 40%, respectively, P = 0.012. Incidence and total dose of the phenylephrine supplement in the sitting position group were significantly higher than in the other two groups. The sitting position group showed a significantly higher block level (T4 [T3, T4]) as compared to the left-lateral (T6 [T5, T6]) and right-lateral position groups (T6 [T4, T6]), P < 0.01. The Apgar scores of neonates at 1 min and 5 min, and the pH values of the umbilical arterial and venous blood were similar among the three groups. CONCLUSION: As compared to the lateral positions, CSEA with hypobaric ropivacaine in the sitting position is more likely to cause hypotension and excessively high block level.

Optimum programmed intermittent epidural bolus interval time between 8 mL boluses of Ropivacaine 0.1% with sufentanil 0.3 µg/mL with dural puncture epidural technique for labor analgesia: A biased-coin up-and-down sequential allocation trial.

OBJECTIVE: The combination of dural puncture epidural (DPE) technique and programmed intermittent epidural bolus (PIEB) is a novel alternative labor analgesia regimen providing rapid analgesia onset and improved analgesia quality. However, the optimum PIEB settings for using the DPE technique remain unclear. DESIGN: Biased-coin up-and-down sequential allocation design. SETTING: Labor analgesia. PATIENTS: Forty nulliparous women requesting labor analgesia. INTERVENTIONS: Dural was punctured using a 25-gauge Whitacre needle. 12 mL of 0.1% ropivacaine with 0.3 µg/mL of sufentanil was used for initiation. Labor analgesia was maintained using the same solution with a fixed 8 mL volume beginning 1 h after initiation. The interval for the first patient was 60 min and varied for subsequent patients according to the biased-coin design (groups 60, 50, 40, and 30; interval 60, 50, 40, and 30 min, respectively). MEASUREMENTS: The primary outcome was adequate analgesia, defined as no request of patient-controlled epidural analgesia or provider boluses for 6 h after the epidural analgesia initiation or until the maternal cervix was fully dilated, whichever came first. The secondary outcomes included sensory blockade level, motor strength, maternal hypotension, and pruritus. RESULTS: The estimated effective interval in 90% of participants was 41.5 min (95% CI 39.5-43.5 min) and 40.5 min (95% CI 33.7-47.5 min) by the truncated Dixon and Mood method and the isotonic regression method, respectively, for the 40 women included. The proportions of patients with the highest sensory block level achieving or above T6 were 60%, 26%, 27%, and 0% in groups 30, 40, 50, and 60, respectively. One patient presented a Bromage score of 1. There was a low incidence of hypotension in all the groups with no need for vasopressor treatment. CONCLUSIONS: The optimum PIEB interval time between 8 mL boluses of ropivacaine 0.1% and sufentanil 0.3 µg/mL when using the DPE technique was approximately 41 min.

Comparison of different approaches to combined spinal epidural anesthesia (CSEA) under the guidance of ultrasound in cesarean delivery of obese patients: a randomized controlled trial.

BACKGROUND: Combined spinal epidural anesthesia (CSEA) is commonly performed in cesarean deliveries. However, it is difficult to perform in obese parturients because of positioning challenges. The aim of this study was to compare the effect of different approaches to CSEA under the guidance of ultrasound. METHODS: One hundred obese patients (BMI ≥ 30 kg/m2) who underwent elective cesarean section were randomly enrolled. Patients were assigned to a median approach group and a paramedian approach group randomly. Clinical characteristics were compared between groups. First-attempt success rate, the median positioning time and total operation time, ultrasonic predicted anesthesia puncture depth, actual puncture depth, anesthesia adverse reactions, complications after anesthesia, and patients' satisfaction with the epidural puncture were recorded. RESULTS: The first-attempt success rate was significantly different between the two groups [92% (46/50) vs. 76% (38/50), P = 0.029]. The median positioning time and total operation time in the paramedian approach group were higher than those in the median approach group (227.7 s vs. 201.6 s, P = 0.037; 251.3 s vs. 247.4 s, P = 0.145). The incidence of postanesthesia complications in the paramedian approach group was significantly lower than that in the median approach group (2% vs. 12%, P = 0.026), and patient satisfaction was higher in the paramedian approach group than in the median approach group (P = 0.032). CONCLUSION: The ultrasound-guided paramedian approach for CSEA is time-consuming, but it can effectively improve the success rate of the first puncture, reduce the incidence of anesthesia-related adverse reactions, and improve patient satisfaction. TRIAL REGISTRATION: This study was registered with the Chinese Clinical Trial Registry (ChiCTR1900024722) on July 24, 2019.

Specific discrimination and universal signal amplification for RNA detection by coupling toehold exchange with RCA through nucleolytic conversion of a structure-switched hairpin probe.

Herein, we combined toehold exchange with ligation-free rolling circle amplification (RCA) by programming nucleolytic conversion of hairpin probe into sensors, allowed for both high specific recognition and universal signal amplification for RNA detection. The rational engineered HP ensured highly specific recognition based on toehold exchange and allowed the pre-formed circular template for RCA to be shared for different RNAs detection. Generally, detecting different RNA requires different circular template for signal amplification. In this paper, the circular template for RCA was independent of the sequences of the target, so the signal amplification system was an universal one for different RNAs detection. Taking miRNA let-7d as a model target, this method showed a wide linear range from 1 fM to 1 nM with a detection limit of 0.46 fM and exhibited a remarkable selectivity even in distinguishing homologous miRNAs with 1-nt or 2-nt difference. To evaluate the potential of the method, it was applied to analysis the let-7d concentration in human serum, total RNA, and cell lysates. In conclusion, we believe this method exhibits potential for both specific discrimination and universal signal amplification for RNA analysis in complex matrices.

A novel cytosensor based on Pt@Ag nanoflowers and AuNPs/Acetylene black for ultrasensitive and highly specific detection of Circulating Tumor Cells.

Circulating tumor cells (CTCs), as the cellular origin of metastasis, are cancer cells that break away from a primary tumor and circulate in the peripheral blood. And they provide a wealth of information about tumor phenotype. Here, this work reported a novel ultrasensitive immunoassay protocol for the detection of CTCs by using Pt@Ag nanoflowers (Pt@AgNFs) and AuNPs/Acetylene black (AuNPs/AB) nanomaterial. In the established approach, AuNPs/AB nanomaterial was used as substrate material to increase the specific surface area and enhance the conductivity of the gold electrode. Protein G was used for oriented immobilization of capture antibody, which strongly improved the capture efficiency of MCF-7 cells. The innovatively synthesized Pt@AgNFs by our group with high specific surface area and good biocompatibility were not only as the carriers of signal antibodies (Ab2) but also catalyzed the reduction of H2O2, which effectually amplified the current signal. A linear relationship between current signals and the concentrations of CTCs was obtained in the range from 20 to 1×106 cells mL-1 and the detection limit is as low as 3 cells mL-1 on condition of acceptable stability and reproducibility. Furthermore, the as-proposed cytosensor showed excellent performance in the detection of CTCs in human blood samples. These results suggest that the proposed cytosensor will be a promising application for accurately quantitative detection of CTCs.

Analogous modified DNA probe and immune competition method-based electrochemical biosensor for RNA modification.

N6-methyladenosine (m6A), one of the most abundant RNA methylation which is ubiquitous in eukaryotic RNA, plays vital roles in many biological progresses. Therefore, the rapid and accurate quantitative detection of m6A is particularly important for its functional research. Herein, a label-free and highly selective electrochemical immunosensor was developed for the detection of m6A. The method is established on that the anti-m6A-Ab can recognize both m6A-RNA and m6A-DNA. An analogous modified DNA probe (L1) serves as a signal molecule, by competing with m6A-RNA for binding to Abs to broaden the linear range. The detection of m6A-RNA by this method is unaffected by the lengths and base sequences of RNA. Under optimal conditions, the proposed immunosensor presented a wide linear range from 0.05 to 200 nM with a detection limit as low as 0.016 nM (S/N = 3). The specificity and reproducibility of the method are satisfactory. Furthermore, the developed immunosensor was validated for m6A determination in human cell lines. Thus, the immunosensor provides a promising platform for m6A-RNA detection with simplicity, high specificity and sensitivity.

Double-loop hairpin probe and doxorubicin-loaded gold nanoparticles for the ultrasensitive electrochemical sensing of microRNA.

An electrochemical microRNA (miRNA) analysis platform by combining double-loop hairpin probe (DHP) and doxorubicin-loaded gold nanoparticles (AuNPs@Dox) for ultrasensitive miRNA detection is proposed. Firstly, we here report a DHP that is simultaneously engineered to incorporate a miRNA recognition sequence, an output segment and output's complementary fragment. The important aspect of this hairpin probe is that it would not be degraded by duplex specific nuclease (DSN) and circumvents elaborately chemical modification disadvantages encountered by classic molecular beacon. For the DHP-based DSN signal amplification system, DHP hybridizes with target miRNA to form DNA-miRNA heteroduplexes, and the DSN can hydrolyze the DNA in the heteroduplexes structure selectively, while released target miRNA strand can initiate another cycle resulting in a significant signal amplification and the accumulated output segments could be responsible for strand displacement on the electrode directly. Furthermore, a great deal of doxorubicin (Dox) are loaded on the gold nanoparticles (AuNPs) to fabricate the AuNPs@Dox biocomposites that could magnify the electrochemical signal and enable the ultrasensitive analysis of miRNA. As a result, the miRNA was capable of being detected in a limit of 0.17pM and other kinds of miRNA were discriminated facilely by this method. The described DHP as a toolbox and the nano-biocomposites as a novel signal material would not only promote the design of electrochemical biosensors but also open a good way to promote the establishment of test method in malignant tumors.

Universal ratiometric electrochemical biosensing platform based on mesoporous platinum nanocomposite and nicking endonuclease assisted DNA walking strategy.

The occurrence and development of many complex diseases are associated with various molecules, whose contents are rarely in the early stage of the disease. Thus a universal platform for the ultrasensitive detection of multilevel biomarkers should be developed. In this study, we introduced an electrochemical biosensing system based on nicking endonuclease (Nt.BbvCI) assisted DNA walking strategy. We successfully constructed a universal signal-off-on ratiometric electrochemical biosensor for various biomolecules, including small molecules, nucleic acids, and proteins, by progressively optimizing the schematics (schemes 1, 2, and 3). The MB-hairpin probes (MB-HPs) acted as a signal-off probe, and nanocomposites (MPNs@DOX@DNA2) acted as a conventional signal-on probe (scheme 3). With the aid of the MPNs@DOX@DNA2 and Nt.BbvCI assisted DNA walking mechanism, the designed ratiometric electrochemical biosensor showed a high sensitivity and broad detection range. In addition, the proposed method can be utilized to detect diverse targets quantitatively by changing the sequence of aptamers under optimum experimental conditions. Furthermore, it has been widely proved to realize well-accepted signal response in identifying complex samples, thereby resulting in an wide prospect for bioanalysis and clinical diagnosis.

A novel platform for high sensitivity determination of PbP2a based on gold nanoparticles composited graphitized mesoporous carbon and doxorubicin loaded hollow gold nanospheres.

Gold nanoparticles composite graphitized mesoporous carbon nanoparticles (GMCs@AuNPs) biocomposite with the signal amplification capability was successfully synthesized for use in an immunoassay for penicillin binding protein 2 a (PbP2a). The polyamidoamine (PAMAM) dendrimers were first electrodeposited onto the Au electrode can greatly increase the amount of the captured antibodies. Protein A was used to properly orientate immobilized antibody against PbP2a, which strongly improved specificity of the antigen-antibody binding. Hollow gold nanospheres (HGNPs) as effective nanocarriers have been synthesized by sacrificial galvanic replacement of cobalt nanoparticles capable of encapsulating doxorubicin (Dox). The obtained HGNPs@Dox bionanocomposite was used for further loading of detection antibody (Ab2) to form the HGNPs@Dox@Ab2 bioconjugate. Then, the differential pulse voltammetric signals related to the concentration of PbP2a for Dox could be detected, and the immunosensor exhibited a detection limit as low as 0.65 pg mL(-1) (at an S/N ratio of 3). The proposed method with an excellent differentiation ability showed high sensitivity and specificity. The morphologies and electrochemistry properties of the composites were investigated by scanning electron microscopy, electrochemical characterization, UV-visible absorption spectroscopy, fluorescence spectrophotometer and Malvern laser particle size analyzer, respectively. In addition, the basic approach described here would be applicable towards developing biodetection assays against other important targets. Moreover, the bioconjugate of HGNPs@Dox is also a promising pattern to delivery Dox in vivo for anticancer therapy.

Intravenous remifentanil versus epidural ropivacaine with sufentanil for labour analgesia: a retrospective study.

Remifentanil with appropriate pharmacological properties seems to be an ideal alternative to epidural analgesia during labour. A retrospective cohort study was undertaken to assess the efficacy and safety of remifentanil intravenous patient-controlled analgesia (IVPCA) compared with epidural analgesia. Medical records of 370 primiparas who received remifentanil IVPCA or epidural analgesia were reviewed. Pain and sedation scores, overall satisfaction, the extent of pain control, maternal side effects and neonatal outcome as primary observational indicators were collected. There was a significant decline of pain scores in both groups. Pain reduction was greater in the epidural group throughout the whole study period (0 ∼ 180 min) (P < 0.0001), and pain scores in the remifentanil group showed an increasing trend one hour later. The remifentanil group had a lower SpO2 (P < 0.0001) and a higher sedation score (P < 0.0001) within 30 min after treatment. The epidural group had a higher overall satisfaction score (3.8 ± 0.4 vs. 3.7 ± 0.6, P = 0.007) and pain relief score (2.9 ± 0.3 vs. 2.8 ± 0.4, P < 0.0001) compared with the remifentanil group. There was no significant difference on side effects between the two groups, except that a higher rate of dizziness (1% vs. 21.8%, P < 0.0001) was observed during remifentanil analgesia. And logistic regression analysis demonstrated that nausea, vomiting were associated with oxytocin usage and instrumental delivery, and dizziness was associated to the type and duration of analgesia. Neonatal outcomes such as Apgar scores and umbilical-cord blood gas analysis were within the normal range, but umbilical pH and base excess of neonatus in the remifentanil group were significantly lower. Remifentanil IVPCA provides poorer efficacy on labor analgesia than epidural analgesia, with more sedation on parturients and a trend of newborn acidosis. Despite these adverse effects, remifentanil IVPCA can still be an alternative option for labor analgesia under the condition of one-to-one bedside care, continuous monitoring, oxygen supply and preparation for neonatal resuscitation.