Aptasensor based on screen-printed electrode for breast cancer detection in undiluted human serum.

Breast cancer remains one of the leading causes of women death. The development of more sensitive diagnostic tests, which could present a faster response, lower cost, and could promote early diagnosis would increase the chances of survival. This study reports the development and optimization of an electrochemical aptasensor for the detection of HER2 protein, a breast cancer biomarker. Two sensing platforms were developed on gold screen-printed electrodes. The first platform is composed of self-assembled monolayer (SAM) made from mixture of thiolated DNA aptamers specific for HER2 and 1-mercapto-6-hexanol (MCH), while the second one is a ternary SAM composed of the same aptamer and 1,6-hexanethiol (HDT). Both platforms were further passivated with MCH and blocked with bovine serum albumin. The biosensors were characterized using electrochemical impedance spectroscopy to detect the target protein from 1 pg/mL to 1 µg/mL in phosphate buffered saline, diluted and undiluted human serum through charge transfer resistance value. The ternary SAM architecture shows a reduction of non-specific attachment to the electrode surface due to the HDT antifouling properties. In addition, this platform exhibits 172 pg/mL as limit of detection and a sensitivity of 4.12% per decade for undiluted serum compared with SAM architecture with the 179 pg/mL and 4.32% per decade, respectively. Electrochemical aptasensors are highly promising for medical diagnostic and ternary layers could improve the limit of detection.

Estimation of Body Composition and Water Data Depends on the Bioelectrical Impedance Device.

Overweight, obese and chronic kidney disease patients have an altered and negative body composition being its assessment important. Bioelectrical impedance analysis is an easy-to-operate and low-cost method for this purpose. This study aimed to compare and correlate data from single- and multi-frequency bioelectrical impedance spectroscopy applied in subjects with different body sizes, adiposity, and hydration status. It was a cross-sectional study with 386 non-chronic kidney disease volunteers (body mass index from 17 to 40 kg/m2), 30 patients in peritoneal dialysis, and 95 in hemodialysis. Bioelectrical impedance, body composition, and body water data were assessed with single- and multi-frequency bioelectrical impedance spectroscopy. Differences (95% confidence interval) and agreements (Bland-Atman analyze) between devices were evaluated. The intraclass correlation coefficient was used to measure the strength of agreement and Pearson's correlation to measure the association. Regression analyze was performed to test the association between device difference with body mass index and overhydration. The limits of agreement between devices were very large. Fat mass showed the greatest difference and the lowest intraclass and Pearson's correlation coefficients. Pearson's correlation varied from moderate to strong and the intraclass correlation coefficient from weak to substantial. The difference between devices were greater as body mass index increased and was worse in the extremes of water imbalance. In conclusion, data obtained with single- and multi-frequency bioelectrical impedance spectroscopy were highly correlated with poor agreement; the devices cannot be used interchangeably and the agreement between the devices was worse as body mass index and fat mass increased and in the extremes of overhydration.

Capacitive aptasensor based on interdigitated electrode for breast cancer detection in undiluted human serum.

We report the development of a simple and powerful capacitive aptasensor for the detection and estimation of human epidermal growth factor receptor 2 (HER2), a biomarker for breast cancer, in undiluted serum. The study involves the incorporation of interdigitated gold electrodes, which were used to prepare the electrochemical platform. A thiol terminated DNA aptamer with affinity for HER2 was used to prepare the bio-recognition layer via self-assembly on interdigitated gold surfaces. Non-specific binding was prevented by blocking free spaces on surface via starting block phosphate buffer saline-tween20 blocker. The sensor was characterized using cyclic voltammetry, electrochemical impedance spectroscopy (EIS), atomic force microscopy and contact angle studies. Non-Faradic EIS measurements were utilized to investigate the sensor performance via monitoring of the changes in capacitance. The aptasensor exhibited logarithmically detection of HER2 from 1pM to 100nM in both buffer and undiluted serum with limits of detection lower than 1pM. The results pave the way to develop other aptamer-based biosensors for protein biomarkers detection in undiluted serum.

Highly sensitive dual mode electrochemical platform for microRNA detection.

MicroRNAs (miRNAs) play crucial regulatory roles in various human diseases including cancer, making them promising biomarkers. However, given the low levels of miRNAs present in blood, their use as cancer biomarkers requires the development of simple and effective analytical methods. Herein, we report the development of a highly sensitive dual mode electrochemical platform for the detection of microRNAs. The platform was developed using peptide nucleic acids as probes on gold electrode surfaces to capture target miRNAs. A simple amplification strategy using gold nanoparticles has been employed exploiting the inherent charges of the nucleic acids. Electrochemical impedance spectroscopy was used to monitor the changes in capacitance upon any binding event, without the need for any redox markers. By using thiolated ferrocene, a complementary detection mode on the same sensor was developed where the increasing peaks of ferrocene were recorded using square wave voltammetry with increasing miRNA concentration. This dual-mode approach allows detection of miRNA with a limit of detection of 0.37 fM and a wide dynamic range from 1 fM to 100 nM along with clear distinction from mismatched target miRNA sequences. The electrochemical platform developed can be easily expanded to other miRNA/DNA detection along with the development of microarray platforms.