The number of patients in intensive care units has increased over the past years. Critically ill patients are treated with a real time support of the instruments that offer monitoring of relevant blood parameters. These parameters include blood gases, lactate, and glucose, as well as pH and temperature. Considering the COVID-19 pandemic, continuous management of dynamic deteriorating parameters in patients is more relevant than ever before. This narrative review aims to summarize the currently available literature regarding real-time monitoring of blood parameters in intensive care. Both, invasive and non-invasive methods are described in detail and discussed in terms of general advantages and disadvantages particularly in context of their use in different medical fields but especially in critical care. The objective is to explicate both, well-known and frequently used as well as relatively unknown devices. Furtehrmore, potential future direction in research and development of realtime sensor systems are discussed. Therefore, the discussion section provides a brief description of current developments in biosensing with special emphasis on their technical implementation. In connection with these developments, the authors focus on different electrochemical approaches to invasive and non-invasive measurements in vivo.

We demonstrate the functionalization of silicon nanowire based field effect transistors (SiNW FETs) FETs with stimuli-responsive polymer brushes of poly(N-isopropylacrylamide) (PNIPAAM) and poly(acrylic acid) (PAA). Surface functionalization was confirmed by atomic force microscopy, contact angle measurements, and verified electrically using a silicon nanowire based field effect transistor sensor device. For thermo-responsive PNIPAAM, the physicochemical properties (i.e., a reversible phase transition, wettability) were induced by crossing the lower critical solution temperature (LCST) of about 32 °C. Taking advantage of this property, osteosarcomic SaoS-2 cells were cultured on PNIPAAM-modified sensors at temperatures above the LCST, and completely detached by simply cooling. Next, the weak polyelectrolyte PAA, that is sensitive towards alteration of pH and ionic strength, was used to cover the silicon nanowire based device. Here, the increase of pH will cause deprotonation of the present carboxylic (COOH) groups along the chains into negatively charged COO⁻ moieties that repel each other and cause swelling of the polymer. Our experimental results suggest that this functionalization enhances the pH sensitivity of the SiNW FETs. Specific receptor (bio-)molecules can be added to the polymer brushes by simple click chemistry so that functionality of the brush layer can be tuned optionally. We demonstrate at the proof-of concept-level that osteosarcomic Saos-2 cells can adhere to PNIPAAM-modified FETs, and cell signals could be recorded electrically. This study presents an applicable route for the modification of highly sensitive, versatile FETs that can be applied for detection of a variety of biological analytes.

Achieving and maintaining optimal oral health necessitates a comprehensive understanding of the complex bio‐adhesive and metabolic processes occurring within the oral cavity. These processes are significantly influenced by the intricate composition of oral fluids, particularly saliva and its resident microbiome. Currently available methodologies struggle to accurately monitor the dynamic and heterogeneous nature of key oral biomarkers, such as glucose. The development of miniaturized sensors for continuous and quantitative monitoring of clinically relevant salivary parameters represents a significant advancement in diagnostic capabilities. This work introduces an electrochemical sensor array designed for the continuous, quantitative monitoring of the clinically relevant and paradigmatic metabolite glucose. To address the challenges posed by the complex salivary environment, a surface modification strategy is implemented involving hybrid films of Prussian blue with chitosan and glucose oxidase enzyme entrapped within chitosan. The incorporation of chitosan, along with the further integration of zwitterionic polymer based on self‐polymerized dopamine (pDA) and 2‐ Methacryloyloxyethyl Phosphoryl Choline (MPC), facilitates the sensitive, selective, and reliable glucose monitoring in harsh salivary environments. Continuous amperometric glucose monitoring showcases the platform's capability for real‐time quantification, as increasing glucose concentrations correspond with elevated current signals. Pilot experiments show the sensors' capacity to precisely quantify salivary glucose levels and ascertain unknown concentrations, validated through the use of commercial glucometers. While the initial focus lies on glucose detection as a proof of concept, the final device integrates multiple electrochemical and potentiometric sensors. This advanced configuration enables the comprehensive quantification of several clinically relevant parameters in saliva. The development of multi‐sensor devices for continuous monitoring within the oral cavity holds immense potential: by unlocking deeper insights into the mechanisms driving the onset and progression of oral diseases, it will pave the way for further innovations in preventive dentistry.

Accurate monitoring of reproductive hormones is essential for the diagnosis and for improving treatment outcomes in infertility, polycystic ovary syndrome (PCOS), and other endocrine disorders. Conventional methods such as enzyme‐linked immunosorbent assay (ELISA) are reliable but often invasive, time‐consuming, and hence unsuitable for real‐time or point‐of‐care applications. We present a silicon nanonet‐based field‐effect transistor (BioFET) functionalized with DNA aptamers as a nano‐biosensing platform for discrete and real‐time detection of 17β estradiol (E2)—a key biomarker in reproductive health. The biosensor exhibits concentration‐dependent changes in drain–source current (I _SD ) across E2 levels of 20–400 pg/mL in phosphate‐buffered saline, reflecting physiologically relevant conditions. Minimal responses to progesterone and testosterone (200 pg/mL) confirm high selectivity. Analysis of the transfer characteristics shows a consistent increase in I _DS at fixed gate voltage with rising E2 concentration, while fluorescence microscopy verifies spatially controlled aptamer immobilization. The latter is achieved through microcontact printing, which enables patterned deposition of aptamers onto the 3‐triethoxysilylpropylsuccinic anhydride (TESPSA)‐functionalized silicon surface with high spatial precision. Real‐time monitoring at the gate voltage (V _G ) of 1.5 V enables dynamic tracking of hormone levels and partial signal reversibility after NaCl‐induced dissociation. Machine learning (ML) models applied to the time‐series biosensor data enable accurate prediction of E2 concentrations. These results emphasize the high potential of aptamer‐based BioFETs, particularly when integrated with data‐driven analysis, for non‐invasive and real‐time hormone monitoring in fertility care.

Thyroxine (T4) is a key hormone regulating metabolic, cardiovascular, and neurodevelopmental processes, yet its clinical quantification still relies on centralized immunoassays that limit rapid or point-of-care monitoring. Here, we present a label-free biosensing platform based on silicon nanowire field-effect transistors (SiNW-FETs) functionalized with a T4-selective DNA aptamer via a 3-Triethoxysilyl propylsuccinic Anhydride (TESPSA)-mediated silanization approach, enabling a streamlined two-step modification for oriented immobilization. The biosensor achieves robust real-time detection of T4 across the physiological concentration range (5–30 pM), with a limit of detection of ~5 pM and a strong linear correlation between drain current and analyte concentration (R² = 0.9931). Specificity is confirmed using non-functionalized devices and estradiol as a non-target control. All measurements were performed in undiluted phosphate-buffered saline, representing a physiologically relevant ionic environment and demonstrating stable sensor performance under realistic buffer conditions. The dose–response behavior follows a Hill model, allowing extraction of binding parameters and confirming that the electrical signal originates from specific aptamer–target interactions. These results demonstrate that aptamer-functionalized SiNW-FETs provide a highly sensitive, selective, and miniaturizable platform for quantitative thyroid hormone monitoring, with strong potential for future point-of-care applications.