Location of Biomarkers and Reagents within Agarose Beads of a Programmable Bio‐nano‐chip

Abstract

The slow development of cost-effective medical microdevices with strong analytical performance characteristics is due to a lack of selective and efficient analyte capture and signaling. The recently developed programmable bio-nano-chip (PBNC) is a flexible detection device with analytical behavior rivaling established macroscopic methods. The PBNC system employs ≈300 μm-diameter bead sensors composed of agarose “nanonets” that populate a microelectromechanical support structure with integrated microfluidic elements. The beads are an efficient and selective protein-capture medium suitable for the analysis of complex fluid samples. Microscopy and computational studies probe the 3D interior of the beads. The relative contributions that the capture and detection of moieties, analyte size, and bead porosity make to signal distribution and intensity are reported. Agarose pore sizes ranging from 45 to 620 nm are examined and those near 140 nm provide optimal transport characteristics for rapid (<15 min) tests. The system exhibits efficient (99.5%) detection of bead-bound analyte along with low (≈2%) nonspecific immobilization of the detection probe for carcinoembryonic antigen assay. Furthermore, the role analyte dimensions play in signal distribution is explored, and enhanced methods for assay building that consider the unique features of biomarker size are offered.

Materials for Microfluidic Immunoassays: A Review

“…[65] Typically, the plastic flow-through microchip integrated a 280 µm diameter porous agarose beads with analyte-specific antibodies which can specifically identify biomarkers. [66] The agarose beads allowed a higher density in capturing the biomarkers owing to the 3D lattice structure to result in higher signal than conventional approaches and, thus, improved sensitivity. The self-contained, integrated microchip was fabricated with plastic using injection method for massfabrication which are designed for POC diagnosis.…”

Porous bead-based microfluidic assay: theory and confocal microscope imaging

“…Recent reviews by Ng et al (2010) and Derveaux et al (2008) discuss the synergy between microbead and microfluidic technologies. While many bead-based assays rely solely on reactions at the outer surface of the bead, the accessibility of the three-dimensional internal microstructure of porous beads enhances test sensitivity and improves binding capacity (Ali et al 2003;Jokerst et al 2011). This is achieved through increased surface area and reduced diffusion distances in the interior matrix.…”

“…Ali et al (2003) studied DNA hybridization within the pore structure of agarose bead microreactors with a confocal microscope and argued that the availability of internal binding sites improves intrinsic test sensitivity. Jokerst et al (2011) monitored labeled antigen migration within the matrix of agarose beads and, in tandem with finite element simulations, determined the impact of biomarker size, bead porosity, and antibody loading levels on immunocomplex formation and its associated signaling characteristics.…”

Programmable Bio-Nano-Chip System: A Flexible Diagnostic Platform that Learns

“…In an attempt to move these medical microdevices into broadscale clinical practice, a number of clinical trials and pilot studies have been initiated. Likewise, the laboratory version (not shown here, but reported extensively previously) [5][6][7][8][9][10] along with the more recently developed integrated analyzer Figure 1a and p-BNC cartridges Figure 1b are now involved in six clinical trials and two pilot studies, respectively, involving over 5,000 patients including over 10 clinical sites for diseases in the areas of cardiac heart disease, ovarian cancer, prostate cancer and drugs of abuse (Table 1).…”

“…This platform technology combines unique chem-and biosensing capabilities with powerful machine learning algorithms to provide novel and intuitive single-valued indices across several major diseases [5][6][7][8][9][10][11][12]. Nanomaterials and microelectronics have been combined and adapted for the practical implementation of two classes of mini-sensors (bead-based sensors for soluble chemistries and membrane-based chips for cytology) that read out with high-performance yet affordable imaging systems now in development, testing, and clinical validation.…”