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3D bioprinting technologies and bioink development are enabling significant advances in miniaturized and integrated biosensors. For example, bioreceptors can be immobilized within a porous 3D structure to significantly amplify the signal, while biocompatible and mechanically flexible systems uniquely enable wearable chem- and bio-sensors. This advancement is accelerating translation by enabling the production of high performance, reproducible, and flexible analytical devices. The formulation of the bioink plays a crucial role in determining the bio-functionality of the resulting printed structures, e.g., the porosity that allows the analyte to diffuse through the 3D structure, the affinity and avidity of the receptors, etc. This review explores the next generation of advanced bioinks for biosensor development and provides insights into the latest cutting-edge bioprinting technologies. The bioprinting methods available for biosensor fabrication including inkjet, extrusion, and laser-based bioprinting, are discussed. The advantages and limitations of each method are analysed, and recent advancements in bioprinting technologies are presented. The review then delves into the properties of advanced bioinks, such as biocompatibility, printability, stability, and applicability. Different types of advanced bioinks are explored, including multicomponent, stimuli-responsive, and conductive bioinks. Finally, the next generation of bioinks for biosensors is considered, identifying possible new opportunities and challenges. Overall, this literature review highlights the combined importance of bioink formulation and bioprinting methods for the development of high-performance analytical biosensors.

An impedance-based biosensor for the ultrasensitive, selective, and label-free detection of a blood miRNA associated to Alzheimer disease (AD), miRNA-206, was developed. The principle was grounded in the changes in the charge transfer resistance (RCT) as an effect of intramolecular forces between miRNAs and ferro/ferricyanide in a well-structured transducer platform. A compact well-ordered mixed monolayer made of co-immobilized miRNA capture to 6-mercapto-1-hexanol (MCH) in a 1:4 M ratio (at 37 °C), uplifted the performance of the sensor through effectively assisting the orientation of the oligonucleotides. In this work, the remarkable response of the sensor was generated through new insights into the use of different moieties of miRNA capture to MCH, aiming to control interfacial constants, surface densities, and hybridization efficiency.A very low limit of detection, 0.15 aM, is achieved and the sensor has a wide linear dynamic range (from 1 aM to 1 μM), high selectivity to mismatches, low non-specific binding of proteins (BSA) and good stability (95 % recovery), correlating directly with qPCR results. Nanomolar concentrations of miRNA-206 were found in the plasma of confirmed AD patients, while healthy controls, had a concentration of pM or lower. The biosensor's ability to quantitatively detect miRNA-206 in plasma without target amplification, e.g., using PCR, is significant, opening the possibility of developing a point-of-care diagnostic device for AD screening, contributing to clinical trials and patient care.