Strategy to Immobilize Peptide Probe Selected through In Vitro Ribosome Display for Electrochemical Aptasensor Application.

In this study, we demonstrated an electrochemical aptasensor for calmodulin (CaM) detection and the peptide sequence (YWDKIKDFIGG) is obtained from in vitro ribosome display selection. To immobilize this peptide probe on the electrode surface, cystine was incorporated at the end of this peptide sequence. After a maleimide-functionalized poly(3,4-ethylenedioxythiophene), poly(EODT-MI), film was electropolymerized on the electrode, the peptide probe was immobilized through thiol-ene conjugation with the cystine end. Four peptides with different linkers were used for the binding test of bovine serum albumin and CaM using a quartz crystal microbalance. The zwitterionic linker EKEKEKEKEKEK provided good antifouling properties and the highest CaM binding. Furthermore, the immobilization of the peptide with this zwitterionic linker resulted in a minimal increase in the electrochemical impedance. By immobilizing the peptide with the selected zwitterionic linker, we successfully demonstrated an electrochemical aptasensor with a linear detection range for CaM from 0.01 to 10 mg/L and a detection limit of 0.001 mg/L.

Dual aptamer assay for detection of Acinetobacter baumannii on an electromagnetically-driven microfluidic platform.

Rapid detection of Acinetobacter baumannii (AB) is critical for limiting healthcare-associated infections and providing the best treatment for infected individuals. Herein an integrated microfluidic device for AB diagnosis utilizing a new dual aptamer assay was developed for point-of-care (POC) applications; magnetic beads coated with AB-specific aptamers were used to capture bacteria, and quantum dots (QD) bound to a second aptamer were utilized to quantify the amount of bacteria with a light-emitting diode (LED)-induced fluorescence module integrated into the device. Within a rapid detection of 30 min, a limit of detection of only 100 colony-forming units (CFU)/reaction was obtained, and all necessary microfluidic devices were actuated by a combination of permanent magnets and electromagnets. The pumping rate of the micropump was 270 µL/min at only 10 V, which is amenable for POC applications with lower power consumption, and only 10 µL of sample and reagents were required. Given these attributes, an automatic POC device was demonstrated which could perform a dual aptamer assay to diagnose AB by using electromagnetically-driven microfluidic system. This system provides a rapid, sensitive, low power and reagents consumption and fully automated for AB detection by using a dual aptamer assay. It will allow rapid clinical diagnosis of AB in the near future.

Electrochemical SERS for in Situ Monitoring the Redox States of PEDOT and Its Potential Application in Oxidant Detection.

In response to recent developments for applying conducting polymers on various biomedical applications, the development of characterization techniques for evaluating the states of conducting polymers in liquids is beneficial to the applications of these materials. In this study, we propose a platform using electrochemical surface-enhanced Raman scattering (EC-SERS) technology, which allows a direct measurement of the redox states of conducing polymers in liquids. A thiophene-based conducting polymer, hydroxymethyl poly(3,4-ethylenedioxythiophene) or poly(EDOT-OH), was used to demonstrate this concept. Poly(EDOT-OH) films were coated on Au nanoparticle-coated ITO glass as SERS-active substrates. Taking the advantage of Raman enhancement, we can in situ and clearly monitor the redox behavior of poly(EDOT-OH) in aqueous solutions. The Raman peak intensity decreases as the poly(EDOT-OH) film is oxidized. Furthermore, we demonstrated our idea to utilize this phenomenon as the sensing mechanism for oxidant detection. The Raman intensity of conducting polymers reduces faster when oxidants exist, and we obtain a quantitative analysis for the detection of oxidants. Moreover, the oxidized poly(EDOT-OH) films can be reused for detection of oxidants simply by applying a reduction potential to activate the poly(EDOT-OH) films. The film stability was also confirmed, and the detection of two other oxidants, namely ammonium persulfate and iron chloride, were also demonstrated. The results show different SERS spectra of poly(EDOT-OH) films oxidized by using different oxidants. Besides, the oxidized films can be easily recovered simply by applying a cathodic potential, which allows repeating usage and makes it possible for continuous monitoring applications. To the best of our knowledge, this is the first time to apply PEDOT's Raman feature for detection purposes.

C-peptide predicts the remission of type 2 diabetes after bariatric surgery.

BACKGROUND: C-peptide is a surrogate of the pancreatic beta cell mass. However, the clinical significance of C-peptide in a diabetic patient after bariatric surgery has not been studied clearly. METHODS: From February 2005 to January 2009, a total of 205 (124 females and 81 males) consecutive morbidly obese patients with type 2 diabetes mellitus (T2DM) enrolled in a surgically supervised weight loss program with at least 1 year follow-up were examined. Among them, 147 patients (71.7%) received gastric bypass procedures, while the other 58 patients (28.3%) received restrictive-type procedures. RESULTS: The mean C-peptide before the surgery was 5.3 ± 3.5 ng/ml. One hundred nineteen patients (58.0%) had an elevated C-peptide (>4 ng/ml), while 2 patients (1.0%) had a low C-peptide (<1.0 ng/ml). Multivariate analysis confirmed that waist circumference, triglycerides, and HbA1c were the independent predictors for the elevation of C-peptide. It was observed that the mean C-peptide levels decreased to 1.7 ± 0.9 ng/ml 1 year after bariatric surgery with a mean reduction of 64.1%. One year after surgery, 160 patients (78.0%) out of a total of 205 patients had a remission of their T2DM. Patients in the bypass group had a higher diabetes remission rate (91.2%; 134 out of 147) in comparison to patients in the restrictive group (44.8%; 26 out of 58, p < 0.001). The diabetes remission rates for those with preoperative C-peptide <3, 3-6, and > 6 ng/ml were 26 out of 47 (55.3%), 87 out of 108 (82.0%), and 47 out of 52 (90.3%), p < 0.001, respectively. CONCLUSIONS: Baseline C-peptide is commonly elevated in morbidly obese patients with T2DM. There was a marked reduction in C-peptide after a significant weight reduction 1 year after surgery with a T2DM remission rate of 78.0%. Thus, bariatric surgery is recommended for obesity-related T2DM patients with elevated C-peptide.