Wearable microneedle-based colorimetric and fluorescence sensing for transdermal diagnostics

•The review focuses on the integration of microneedles with optical sensors.•Advantages and limitations of microneedles for microsampling action are covered.•Microneedles are fabricated using various methods chosen by type, geometry, and material.•Microneedles-based optical sensing show potential for transdermal diagnostics.•The future perspectives cover ways of enhancing selectivity and sensitivity. Interstitial fluid is a readily accessible source of biomarkers for various diseases, providing a less invasive and more convenient option than traditional blood or tissue sampling methods. Microneedle-based point-of-care testing devices have gained significant interest due to their potential for direct detection of target analytes in ISF, accomplished through minimally invasive penetration of the stratum corneum. Thus, microneedle-based devices can be considered as adhesive tools for diagnostic sensing and therapeutic drug administration. Microneedle-based colorimetric and fluorescence sensing has the potential to revolutionize disease diagnosis and monitoring, offering a rapid, highly sensitive, specific, and cost-effective alternative to traditional methods. These devices enable the detection of low levels of biomarkers in the collected fluid, which is particularly important in situations requiring prompt diagnosis and treatment. This review covers the types of microneedles and their fabrication methods, the detection principles of microneedle-based colorimetric and fluorescence sensing, as well as their key applications, advantages, and limitations. Additionally, the review explores ways to overcome current limitations and improve the performance, as well as future perspectives for the development of microneedle-based devices. [Display omitted]