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This paper deals with the development and characterization of label-free microfluidic biosensors dedicated to the microwave dielectric spectroscopy of small volumes and flowing micro-scale particles. Especially, microwave dielectric spectroscopy offers unique capabilities to investigate intracellular properties of biological cells, which are informative on many biological processes. This paper presents two prototypes of high frequency biosensors able to operate in the microwave frequency range. Both are based on capacitive detection either in a broadband or resonant mode. Thick gold metal electrodes have been investigated to perform high sensitive analysis, while a microfluidic system was implemented over the RF circuit so that flowing liquid minimally impacts global losses of the system and has hence a limited effect on sensor sensitivity. Particles to be tested are manipulated to be accurately located in the detection area using dielectrophoresis techniques. To demonstrate the proposed approach and assess the detection capabilities of such sensors, HF measurements (up to 8 GHz) have been performed on calibrated size polystyrene beads (12 μm diameter) and compared with full-wave electromagnetic simulations. Measured capacitance contrasts are typically around 1 fF at 5 GHz. Preliminary experimentations were then achieved on cancerous cells. The presented results demonstrate the high potential of the proposed approach to develop new label-free analysis tools with a large application range, either in the diagnosis or treatment fields. [ABSTRACT FROM AUTHOR]