Cantilever with immobilized antibody for liver cancer biomarker detection

A novel cantilever array-based bio-sensor was batch-fabricated with IC compatible MEMS technology for precise liver cancer bio-marker detection. A micro-cavity was designed in the free end of the cantilever for local antibody-immobilization, thus the adsorption of the cancer biomarker takes place only in the local region of the cantilever instead of the whole lever, and the effect of adsorption-induced k variation can be dramatically reduced. These structural features offer several advantages： high sensitivity, high throughput, high mass detection accuracy, and a portable system. In addition, an analytical model has been established to eliminate the effect of the adsorption-induced lever stiffness change and has been applied to the precise mass detection of the cancer biomarker AFP; the experimentally detected AFP antigen mass by the sensor （7.6 pg/mL） is quite close to the calculated one （5.5 pg/mL）, two orders of magnitude better than those of the fully antibody-immobilized cantilever sensor. These approaches can promote real applications of the cantilever sensors in cancer diagnosis.

Nanomechanical sensor for rapid and ultrasensitive detection of tumor markers in serum using nanobody

Early cancer diagnosis requires ultrasensitive detection of tumor markers in blood.To this end,we develop a novel microcantilever immunosensor using nanobodies(Nbs)as receptors.As the smallest antibody(Ab)entity comprising an intact antigen-binding site,Nbs achieve dense receptor layers and short distances between antigen-binding regions and sensor surfaces,which significantly elevate the generation and transmission of surface stress.Owing to the inherent thiol group at the C-terminus,Nbs are covalently immobilized on microcantilever surfaces in directed orientation via one-step reaction,which further enhances the stress generation.For microcantilever-based nanomechanical sensor,these advantages dramatically increase the sensor sensitivity.Thus,Nb-functionalized microcantilevers can detect picomolar concentrations of tumor markers with three orders of magnitude higher sensitivity,when compared with conventional Ab-functionalized microcantilevers.This proof-of-concept study demonstrates an ultrasensitive,label-free,rapid,and low-cost method for tumor marker detection.Moreover,interestingly,we find Nb inactivation on sensor interfaces when using macromolecule blocking reagents.The adsorption-induced inactivation is presumably caused by the change of interfacial properties,due to binding site occlusion upon complex coimmobilization formations.Our findings are generalized to any coimmobilization methodology for Nbs and,thus,for the construction of high-performance immuno-surfaces.