Described herein are devices and methods for improved detection and quantitation of biomolecules. Devices and methods may include a microfluidic biosensing platform for measuring electrical impedance changes in the presence of target analytes from sinusoidal input voltages to improve the sensitivity of immunoassays. In one embodiment, the described devices and methods may provide a point-of-care immunoassay platform for quantitative diagnostics using signal-enhancing microparticles to improve sensitivity and the limit-of-detection.