A Supramolecular Approach to Enzyme Immobilization in Micro‐Channels

A supramolecular assembly scheme is developed to enable the facile in‐situ immobilization of enzymes in a microfluidic channel system. A combination of orthogonal supramolecular interactions of host (β‐cyclodextrin)–guest (adamantane) and biotin–Streptavidin (SAv) interactions are employed to generate reusable homogeneous enzyme layers in microchannels. The structural integrity and catalytic activity of the immobilized enzyme calf‐intestine alkaline phosphatase (AlkPh) is demonstrated. From the kinetic analysis of a dephosphorylation reaction, the specificity constant k_cat/K_M for immobilized alkaline phosphatase in the channels is on the order of 10⁵ M^?1s^?1 and comparable to known literature values in other environments. These observations are ascribed to the good access of the substrate to favorably oriented enzymes across the microchannel. Therefore, this study demonstrates the great potential for adopting a supramolecular assembly scheme to immobilize enzymes in microfluidic devices.     

Structural composites hybridized with epoxy compatible polymer/MWCNT nanofibrous interlayers

Surface reactive P(St-co-GMA) copolymer and P(St-co-GMA)/MWCNT fibrous mats are placed onto a conventional carbon fiber/epoxy prepreg as interlayer reinforcing material. Experimental observations are used to demonstrate excellent epoxy wetting and structural compatibility of the interlayers chemically tuned for the epoxy matrix. Comparisons of increase in mechanical performance by incorporating P(St-co-GMA) and P(St-co-GMA)/MWCNT interlayers also show the contribution of MWCNT presence in the copolymer nanofibers. Flexural strength and stiffness of (0/0/0) and (90/0/90) laminates increase up to 17% when the nanocomposite interlayers are integrated. Cross-sectional SEM analyses of the failure surfaces suggest reinforcing ability of interlayers both against transverse cracking and delamination. Further examination for the delamination resistance is presented by the End Notched Flexure (ENF) tests. An improvement up to 70% in mode II strain energy release rate (G_IIc) is recorded for the laminates with nanocomposite interlayers. The resistance against transverse matrix cracking in the presence of interlayers is also elaborated. Charpy-impact and transverse-tension tests result in up to 20% and 27% increase in the impact energy absorbance and transverse tensile strength, respectively. Overall, the test results suggest that mechanical behavior of the laminates is enhanced by the nanofibrous interlayers chemically-tuned for epoxy crosslinking, with no weight penalty.