This paper presents the capabilities of microwave dielectric spectroscopy for biological cells suspensions analysis. The developed biosensor integrates both microfluidic channel for biological samples manipulation together with a microwave circuit for dielectric spectroscopy. Experimental investigation validates the success and accuracy of the microwave dielectric spectroscopy technique. This technique is applied with various cells concentrations in suspension in their culture medium. Results demonstrate that both real and imaginary parts of the contrast of the dielectric permittivity are proportional to the cells concentration with a correlation coefficient (R-square) greater than 0.99. The technique is consequently suitable for proliferation evaluation of cells. More widely, this work contributes to settle down the capabilities of microwave sensing for biochemical and bio-cellular analysis applications.