title: Method for label-free detection of femtogram quantities of biologics in flowing liquid samples.
abstract: Rapid (approximately 10 min) measurement of very low concentration of pathogens (approximately 10 cells/mL) and protein (approximately fg/mL) has widespread use in medical diagnostics, monitoring biothreat agents, and in a broader context as a research method. For low-level pathogen, we currently use culture enrichment methods and, thus, rapid analysis is not possible. For low protein concentration, no direct method is currently available. We report here a novel macrocantilever design whose high-order resonant mode near 1 MHz exhibits mass detection sensitivity of 10 cells/mL for cells and 100 fg/mL for protein. The sensor is 1x3 mm and uses a piezoelectric layer for both actuation and sensing resonance. Sample is flowed (approximately 1 mL/min) past the antibody-immobilized sensor, and as antigen binds to the sensor, resonance frequency decreases in proportion to antigen concentration. The sensor showed selectivity to the pathogen even though copious nonpathogenic variant was simultaneously present.
authors.affiliation: Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA.
authors.forename: David
authors.initials: D
authors.lastname: Maraldo
authors.forename: Kishan
authors.initials: K
authors.lastname: Rijal
authors.forename: Gossett
authors.initials: G
authors.lastname: Campbell
authors.forename: Raj
authors.initials: R
authors.lastname: Mutharasan
mesh_terms: D000818:Animals; D000906:Antibodies / Q000737:chemistry / Q000276:immunology; D000937:Antigen-Antibody Reactions; D002417:Cattle; D004566:Electrodes; D004926:Escherichia coli / Q000737:chemistry* / Q000276:immunology / Q000472:pathogenicity; D009419:Nerve Tissue Proteins / Q000032:analysis* / Q000276:immunology; D012680:Sensitivity and Specificity; D012710:Serum Albumin, Bovine / Q000032:analysis* / Q000276:immunology; D013997:Time Factors
chemical_list: D000906:Antibodies; C029152:G-substrate; D009419:Nerve Tissue Proteins; D012710:Serum Albumin, Bovine