Engineering Shelf-Stable Coating for Microfluidic Organ-on-a-Chip Using Bioinspired Catecholamine Polymers.

The conceptualization of body-on-a-chip in 2004 resulted in a new approach for studying human physiology in three-dimensional culture. Despite pioneering works and the progress made in replicating human physiology on-a-chip, the stability, reliability, and preservation of cell-culture-treated microfluidic chips remain a challenge. The development of a reliable surface treatment technique to more efficiently and reproducibly modify microfluidic channels would significantly simplify the process of creating and implementing organ-on-a-chip (OOC) systems. In this work, a new flow-based coating technique using bioinspired polymers was implemented to create reliable, reproducible, ready-to-use microfluidic cell culture chips for OOC studies. Single-channel polydimethylsiloxane microfluidic chips were coated with the bioinspired catecholamine polymers, polydopamine (PDA) and polynorepinephrine (PNE), using a flow-based coating technique. The functionality of the resulting microfluidic chips was evaluated by extensive surface characterizations, at 130 °C, in the presence of various cleaning and culture media in static and flow conditions regularly used in OOCs and tested for shelf life by storing the coated microfluidic chips for 4 months at room temperature. Microfluidic chips coated with polycatecholamine were then seeded with the mouse cancer cell line Cath.a.differentiated (CAD) and with the normal human cerebral microvascular endothelial cell line human cerebral microvascular endothelial cells (hCMEC)/D3. Cell viability, cell phenotype, and cell functionality were assessed to evaluate the performance of both the coatings and the surface treatment technique. Both PDA- and PNE-coated microfluidic chips maintained high viability, phenotype, and functionality of CAD cells and hCMEC/D3 cells. In addition, CAD cells retained high viability when they were cultured in both the polymer-coated chips, which were stored at room temperature for up to 120 days. These results suggest that flow-based techniques to coat surfaces with polycatecholamines can be used to generate ready-to-use microfluidic OOC chips that offer long-term stability and reliability for the culture of cell types with application in pathophysiological studies and drug screening.

Single-step functionalization of poly-catecholamine nanofilms for ultra-sensitive immunosensing of ubiquitin carboxyl terminal hydrolase-L1 (UCHL-1) in spinal cord injury.

Rapid, selective, and ultra-sensitive detection of brain and spinal cord injury markers in bodily fluids is an unmet clinical need. In this work, Polycatecholamine as a rich source of amine moieties was used for single-step fabrication of ultrasensitive immunosensors for the detection of Ubiquitin carboxyl-terminal hydrolase (UCHL-1) biomarker of brain and spinal cord injuries and address the clinical need. The surface of graphene electrodes was modified by electropolymerizing aqueous solution of dopamine (DA) and norepinephrine (NE) monomers for generating polycatecholamines nanofilms on the surface of graphene screen printed electrodes (GSPE) in a single functionalization step. Amine moieties of the polymer allowed immobilization of UCHL-1 antibody on the electrode. The single-step modification of GSPE offered a simple, ultrasensitive, and stable production of immunosensors for the detection of UCHL-1. The operational range of the UCHL-1 immunosensor developed with Polynorepinephrine pNE-modified is 0.1 pg mL-1 - 105 pg mL-1 (LOD: 1.91 pg mL-1), and 1 pg mL-1 - 105 pg mL-1 (LOD: 0.70 pg mL-1) with Polydopamine (pDA) modification, satisfying the clinical range. Both pNE and pDA modified immunosensors, detected UCHL-1 spiked in phosphate buffer saline, artificial cerebrospinal fluid, and serum. Along with the sensitive detections, selective performances were recorded in the above matrices in the presence of interfering neurotransmitters GABA and Glutamate as well as glial fibrillary acidic protein (GFAP). Upon testing clinical samples of spinal cord injury patients and healthy controls, both pNE and pDA immunosensors, delivered a comparable response for UCHL-1, thereby, making immunosensors useful for clinical settings.