Electrical Impedance Myography (EIM) is a painless, non-invasive electrophysiological technique for the assessment of different disease status of the human body. In EIM, high frequency, low-intensity electrical current is injected via the surface electrode to the localized area and resulting voltage patterns are analyzed using the voltage sensing electrode to access three major parameters-resistance(R), reactance(X), and phase(θ). This method detects the abnormalities in the biological tissue based on differences in values of these three parameters between normal and malignant tissue. In this study, a finite element model of the human breast has been developed in an attempt to analyze the EIM parameters for the detection of malignant tissue. Simulations were carried out for a frequency range of 2 to 3 GHz and electrical properties of breast tissue were used. For example, at 2.45 GHz, normal breast tissue has a resistance of .961 Ω and a reactance of 4.462 Ω. At this particular frequency, malignant breast tissue with a tumor size of 7 mm had a resistance of .945 ohm and reactance of 4.365 ohm. The percentage deviation of the normal breast tissue from the 7mm malignant tissue for resistance and reactance is 1.665% and 2.174% respectively. This paper attempts to illustrate the behavior of EIM parameters for different size and location of the tumor in the breast tissue. The ultimate goal of the paper is to investigate EIM’s ability to detect early cancer cell in the breast tissue.
Detection in chemical sensing which needs to be carried out in a specific controlled environment, becomes complex in multivariate environment. This complication is caused by chemical interference, sensor degradation or drifting of the signals with time. A minute drifting or overlapping of the signals affects the calibration, especially in the detection of sub-ppm level of concentration of any chemical species. The presence of other compounds can well interfere providing false positive readings, deterring calibration of the system in precise quantification of any compound. This problem is known to also happen in our optical fiber sensor for the detection of ammonia. A clad-modified polymer optical fiber sensor for ammonia detection is explored in this work where oxazine 170 per chlorate dye is used as a recognition element to detect ammonia. The sensor was tested in water media and the sensitivity of the sensor we found was 0.0006 ppm<sup>-1</sup>cm<sup>-2</sup>. However, the lower sensitivity causes significant overlaps in between signals corresponding to different concentrations. To resolve this problem, multivariate analysis method, such as principal component analysis (PCA) was explored to interpret the datasets for precision of measurement and classification of each concentration. PCA generates unique regression curve which represents each concentration of ammonia considering principle components. The significance of this research lies in its versatility dealing with the existing challenge of calibration of sub-ppm level measurement of any volatile compound, such as ammonia.
We report on highly sensitive and flexible biosensors for noninvasive lactate and alcohol monitoring in human perspiration based on zinc oxide (ZnO) nanostructures that does not require linker layer for surface functionalization due to the high isoelectric point of ZnO. Towards fabrication of the biosensors, two-dimensional (2D) ZnO nanoflakes (NFs) were synthesized on flexible polyethylene terephthalate (PET) substrates employing single step sonochemical method after which lactate oxidase (LOx) and anti-body for ethyl glucuronide (EtG)-a metabolite of ethanol were immobilized atop without a linker layer. The cyclic voltammetry (CV) measurements in the concentration range of 10pM-10μM for lactate and 4.5 μM-0.45 M for EtG yielded minimum limit of detection of 10 pM and 4.5 μM, respectively for the electrode area of 0.5 × 0.5 cm<sup>2</sup>. Moreover, lactate sensor with ZnO NF electrodes demonstrated four times higher sensitivity compared to the ones with gold electrode that required DTSP linker layer for surface functionalization. High isoelectric point allows a direct, stable pathway for rapid electron transport without any mediator when an analyte is immobilized on NFs and improves electron transfer rate.