Electrochemical immunoplatform to assist in the diagnosis and classification of breast cancer through the determination of matrix-metalloproteinase-9.

Matrix metalloproteinase 9 (MMP-9) is a zinc-dependent endopeptidase that promotes angiogenesis, tumor growth, metastasis and cell invasion through the degradation of extracellular matrix. This work reports a magnetic microbeads (MBs)-based sandwich immunoassay for the amperometric determination of MMP-9 at screen-printed carbon electrodes (SPCEs). The suitable capture antibody (cAb) is immobilized onto carboxylic MBs to selectively capture the antigen which is sandwiched with a biotinylated detector antibody (biotin-dAb) further conjugated with a commercial streptavidin-horseradish peroxidase (Strep-HRP) polymer. This immunoplatform provides great analytical characteristics in terms of selectivity and sensitivity, achieving a LOD value of 2.4 pg mL for standards in buffered solutions. Although this value is similar to those reported for some other approaches described so far, the method described here is simpler involving a single 30 min incubation step which makes it ideal for automation or implementation in POC devices. Moreover, the method was assayed for the accurate determination of endogenous MMP-9 in both cancer cell lysates and serum samples of patients diagnosed with different subtypes of breast cancer (BC) after a simple dilution. The results obtained show that the disposable and affordable immunoplatform developed is able not only to discriminate BC patients from healthy individuals but also to do it for the worst outcome triple negative (TNBC) subtype.