A concentration-dependent sensing behavior was observed, Figure demonstrates a linear response to different PSA concentrations in spiked untreated bovine serum samples showing sub ng/ml (low pM) sensitivity, with a LOD of 0.2 ng/ml. Additional specificity tests of the SiNPs platform were performed using high concentrations of the nonspecific proteins Cytochrome C, cTnT and BNP as shown in Figure . The concentrations were 100 ng/ml for all tested proteins including the PSA, which is a magnitude higher than the physiological PSA level in a healthy human. The anti-PSA-modified array showed nearzero response to the highly concentrated Cytochrome C, cTnT and BNP, indicating the high specificity of the present sensing microneedle device for the specific detection of the PSA target biomarker.