Electrochemically driven optical and SERS immunosensor for the detection of a therapeutic cardiac drug.

Cardiovascular diseases pose a serious health risk and have a high mortality rate of 31% worldwide. Digoxin is the most commonly prescribed pharmaceutical preparation to cardiovascular patients particularly in developing countries. The effectiveness of the drug critically depends on its presence in the therapeutic range (0.8-2.0 ng mL-1) in the patient's serum. We fabricated immunoassay chips based on QD photoluminescence (QDs-ELISA) and AuNP Surface Enhanced Raman Scattering (SERS-ELISA) phenomena to detect digoxin in the therapeutic range. Digoxin levels were monitored using digoxin antibodies conjugated to QDs and AuNPs employing the sandwich immunoassay format in both the chips. The limit of detection (LOD) achieved through QDs-ELISA and SERS-ELISA was 0.5 ng mL-1 and 0.4 ng mL-1, respectively. It is demonstrated that the sensitivity of QDs-ELISA was dependent on the charge transfer mechanism from the QDs to the antibody through ionic media, which was further explored using electrochemical impedance spectroscopy. We demonstrate that QDs-ELISA was relatively easy to fabricate compared to SERS-ELISA. The current study envisages replacement of conventional methodologies with small immunoassay chips using QDs and/or SERS-based tags with fast turnaround detection time as compared to conventional ELISA.

Prevalence-pattern and risk factors of Cesarean section in a multiethnic cohort.

OBJECTIVE: This study was aimed to elucidate the prevalence-pattern and determinant of cesarean section (CS) in a multiethnic cohort from Pakistan. METHODS: Through a cross-sectional study design, women delivering at a tertiary care center were recruited during 2013-2017. Data on socio-demographic variables, obstetric complications and birth outcome were obtained. Descriptive statistics, bivariate and multivariate logistic regression analyses were performed. RESULTS: A total of 5,275 pregnant women were recruited and 43% of the deliveries underwent CS. Odds of CS were significantly higher in subjects originating from Azad JammuKashmir and Sindh regions, speaking Potohari and Pahari languages, women in advance ages, and those who were housewives. CS had significantly lower odds of prenatal mortality but increased odds of postnatal mortality. Obstetric factors that appeared to be significant predictors of CS were multiparity, breech position, fetal distress, oligohydroamniosis, preeclampsia, and previous scar. CONCLUSION: This study revealed high variability in CS in various socio-demographic strata of study population. The obstetric complications highlighted in this study may be reduced by proper perinatal counseling and pregnancy monitoring and should be the focus of intervention programs as suggested in the Millennium Development Goals.

The electrochemical reaction controlled optical response of cholestrol oxidase (COx) conjugated CdSe/ZnS quantum dots.

This paper reports the enhanced performance of cholesterol oxidase (COx) conjugated CdSe/ZnS quantum dots (QDs) by using water-soluble mercaptoacitic acid (MAA) as linker. The functionalized MAA-CdSe/ZnS QDs conjugated in four different dilutions of cholesterol oxidase significantly affected QDs photoluminescence intensities, which affected the process of charge transfer from QDs to MAA. The conjugation of COx to MAA-QDs in increased dilutions resulted in the regain of PL intensities, which were attributed to the passivation of MAA HOMO/LUMO states. The electrochemical impedance spectroscopy and cyclic voltammetry of the conjugated QDs were performed to get study the charge transfer mechanism. The 1:1000 diluted COx conjugated MAA-CdSe/ZnS QDs was found to have the lowest charge transfer resistance of 228 Ω, the highest diffusion (~ 1.39 × 10-13 cm2/s) and charge transfer rates (~ 4.5 × 10-6 s-1) between the electrode and the redox species. The current study demonstrated the sensitivity of electrochemical and optical based detection on the alkaline.

The adverse role of excess negative ions in reducing the photoluminescence from water soluble MAA-CdSe/ZnS quantum dots in various phosphate buffers.

The use of CdSe/ZnS quantum dots in making biosensors or biomarkers requires them to be water soluble, which can be achieved by conjugating with MAA. We report observation of modulation in the photoluminescence intensities of MAA conjugated CdSe/ZnS QDs (MAA-QDs) that depended strongly on the types and quantity of negative ions present in various kinds of phosphate buffers. The deterioration of PL was attributed to the presence of excess ions in the media that altered the energy and occupation of HOMO and LUMO levels of MAA. Instantaneously, strong reduction in the PL intensity with pH was observed. MAA-QDs incubated for more than 24 hours in the phosphate buffer at pH ∼ 7.0-8.0 showed recovery and enhanced PL intensity, which was attributed to the presence of excess positive ions and a small amount of OH-. Saline buffers showed no significant recovery due to the presence of additional Cl- ions. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were successfully employed to determine the band edges of the MAA-QD system in the presence of excess positive or negative ions (Na+, H+, Cl-, and OH-) in the media. Thus, it is very important to have complete knowledge of the ions present in the buffer when using MAA-QDs for biomarking or biosensing applications.