(162b) Bio-Inspired Pseudo SAMs Coating to Increase the Hemocompatibility of a Microfluidic Photoreactor for the Treatment of Neonatal Jaundice

Hyperbilirubinemia, a condition characterized by excessive bilirubin levels, affects over half of newborn babies and can lead to serious complications including brain damage or death. Absorption of light by bilirubin leads to isomerization reactions that convert bilirubin into more readily excreted compounds (e.g. lumirubin). Here, an extracorporeal microfluidic device has been developed to isomerize bilirubin in neonates. An experiment using a Gunn rat model has shown the microfluidic treatment meets, if not exceeds, the conversion efficiency of exchange transfusions the riskier treatment employed today. Reactor variables such as channel thickness, light intensity, and wavelength of light have been optimized to maximize efficiency. The devices are formed from polycarbonate or cyclic olefin copolymer (COC) and the main design challenge for this device increasing hemocompatibility. To achieve a greater degree of hemocompatibility polydopamine (PDA) and self-assembled monolayers (SAMs) are used to create a hydrophobic layer. The increased hydrophobicity creates a strong layer of repelled water to resist non-specific protein adsorption. While typical SAMs are formed on noble metals there is evidence that they can be formed on PDA surfaces, coined pseudo-SAMs or pSAMs. These pSAMs can be used for simple attachment of target biomolecules like proteins or peptides where the only requirement is an accessible thiol. A solution of dopamine under slightly basic oxidative conditions will self-polymerize onto virtually any material ranging from metals, glasses and plastics. Our approach is to modify the blood contacting channels by forming pSAMs at the interface. The specific molecules in the pSAM contain fluorinated chains in order to create a hydrophobic interface. The pSAM modifications were characterized by water contact angle, atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS). Water contact angle has shown a two-fold increase in the contact angle from a PDA layer (41±3) to a deposited pSAM (85±5) that consisted of the fluorinated chain molecule. The atomic composition of each surface modification step was confirmed by XPS. For example, the S 2p spectra identified the presence of thiols from the pSAM while a change in the nitrogen content represents a modification at the PDA surface. The culmination of these techniques will show the overall quality of the pSAMs. The pSAM coatings lay the groundwork for a simpler attachment of relevant biomolecules like proteins, peptides, or anticoagulants dependent on the application of interest.