As modern medicine becomes more and more integrated, intelligent, and personalized, the demand for novel and specialized biosensors increases. Biosensors are in the center of the current major technological advances in health care and diagnosis, drug delivery, and water and food quality/environmental monitoring. Biosensors are receptor-transducer devices (or probes), which can convert a biological response, from a physiological change caused by enzymes or antibodies, for example, into a measurable electrical signal. At the current state-of-the-art, even low concentrations of specific pathogens, or toxic chemicals, can be measured [1]. Today, the main challenges involved in the development of biosensors are related to the transduction of biosensing signals into electrical (or electrochemical, optical, acoustic etc.) signals, the increase on sensitivity and reproducibility, the decrease of the response time and detection limits, and the miniaturization using micro/nano-fabrication technologies. Recently, several researchers reported significant enhancements in the biosensing technology by using nanomaterials, such as carbon nanotubes, graphene [2] and metal or metal oxide nanoparticles, which present high surface-to-volume ratios, good electrical and thermal conductivities, and mechanical performance [3]. However, one aspect of the design that is often overlooked is electronic instrumentation, which is composed by a low-noise front- end, an amplification unit, a filtering stage, and an analog-to-digital unit. This is a non-ideally process where the circuits introduce inaccuracy, precision degrading, and unreliability for practical biosensors. The most important stage is the low-noise front-end (LNFE) which is connected directly to the biosensor. The topology of the LNFE depends on the nature of the sensor: (i) if the biosensor outputs a voltage, the LNFE is an instrumentation amplifier (INA); (ii) if the biosensor outputs a current, the LNFE can be either a transimpedance amplifier (TIA) or a shunt resistor followed by an INA; (iii) if the biosensor outputs a variation in impedance, the LNFE can be implemented using a bridge circuit, a combination of a current excitation module and an INA, or a combination of a voltage excitation module and a TIA. In case (i), the INA should provide high input impedance, high common-mode rejection ratio, and low input-referred noise for best performance. Furthermore, the INA gain should be designed to reduce the overall noise while maintaining enough dynamic range for the biosensor signal. In case (ii), TIAs are often a better option than shunt resistors, as they provide a lower impedance path to the current. The input impedance of the TIA should be kept small, while still providing enough transimpedance gain and bandwidth for the biosensor current. Moreover, current leakages from parasitic capacitances at the input should be minimized, to improve accuracy and stability. In case (iii), Wheatstone-Bridge circuits are desirable in applications dealing with very small impedance variations in the biosensor. In these cases, the circuit topology should be designed to provide the best sensitivity to the biosensor operation point, as well as to eliminate cable influence and any type of parasitic effect. When excitation circuits are necessary, current sources are typically the best choice, and must be designed with high output impedance, current stability, and voltage compliance [4]. Biosensors based on impedance measurements have an advantage on enzymatic and non-enzymatic electrochemical measurements due to simplicity, sensitivity, selectivity, low detection limit, low cost, and possible miniaturization. However, in some cases, estimation with impedance measurements requires a mathematical model to reduce possible uncertainty values. Measurement using a combination of a biosensor with electrical impedance spectroscopy (EIE) is a better alternative compared to currently used methodologies, with advantages as a non-invasive and non-destructive method [5]. [ABSTRACT FROM AUTHOR]