Porous silicon affinity chips for biomarker detection by MALDI-TOF-MS.

B-type natriuretic peptide (BNP) is an important biomarker in early diagnosis of congestive heart failure. Many efforts have been made previously to evaluate the BNP level in human plasma. We developed a porous silicon (PSi) affinity chip to detect BNP present at low concentrations in human plasma by matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) directly. The PSi surface immobilized with antibodies captured and concentrated BNP through antibody-antigen interaction specifically and sensitively. A detection limit as low as 10 pg/mL BNP in human plasma was demonstrated by mass analysis. This effective on-chip recognition, enrichment, and detection strategy could be employed in identification of biomarkers in complex body fluids in diagnoses.